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Simon Peyton Jones pushed to branch wip/T20666 at <a href="https://gitlab.haskell.org/ghc/ghc" style="color: #1068bf;">Glasgow Haskell Compiler / GHC</a>
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<strong style="font-weight: bold;"><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/eb62d802e3bafa2474ff39ac30a5c5cd69ea9cef" style="color: #1068bf;">eb62d802</a></strong>
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<span> by Simon Peyton Jones </span> <i> at 2022-12-23T09:45:33+00:00 </i>
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compiler/GHC/Tc/TyCl/Instance.hs
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compiler/GHC/Tc/Validity.hs
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<a href="https://gitlab.haskell.org/ghc/ghc/-/commit/eb62d802e3bafa2474ff39ac30a5c5cd69ea9cef#e63425e031ffe9350ee6b1687e506aaea75d11e1" style="color: #1068bf;"><strong style="font-weight: bold;">compiler/GHC/Tc/TyCl/Instance.hs</strong></a>
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<td class="line_content match" style="color: rgba(0,0,0,0.3); padding: inherit;" bgcolor="#fafafa">@@ -1544,8 +1544,8 @@ definition. More precisely:</td>
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1544
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<td class="new_line diff-line-num" data-linenumber="1544" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #f0f0f0; border-right-style: solid; padding: inherit;" align="right" bgcolor="#fafafa">
1544
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<td class="line_content" style="padding: inherit;"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'> <span id="LC1544" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">To achieve the Superclass Invariant, in a dfun definition we can</span></span>
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<td class="old_line diff-line-num" data-linenumber="1545" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #f0f0f0; border-right-style: solid; padding: inherit;" align="right" bgcolor="#fafafa">
1545
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<td class="new_line diff-line-num" data-linenumber="1545" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #f0f0f0; border-right-style: solid; padding: inherit;" align="right" bgcolor="#fafafa">
1545
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<td class="line_content" style="padding: inherit;"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'> <span id="LC1545" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">generate a guaranteed-non-bottom superclass witness from:</span></span>
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<td class="old_line diff-line-num" data-linenumber="1546" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #f0f0f0; border-right-style: solid; padding: inherit;" align="right" bgcolor="#fafafa">
1546
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<td class="new_line diff-line-num" data-linenumber="1546" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #f0f0f0; border-right-style: solid; padding: inherit;" align="right" bgcolor="#fafafa">
1546
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<td class="line_content" style="padding: inherit;"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'> <span id="LC1546" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;"> (sc1) one of the dictionary arguments itself (all non-bottom)</span></span>
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<td class="old_line diff-line-num old" data-linenumber="1547" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #fac5cd; border-right-style: solid; padding: inherit;" align="right" bgcolor="#f9d7dc">
1547
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<td class="new_line diff-line-num old" data-linenumber="1547" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #fac5cd; border-right-style: solid; padding: inherit;" align="right" bgcolor="#f9d7dc">
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<td class="line_content old" style="padding: inherit;" bgcolor="#fbe9eb"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'>-<span id="LC1547" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;"> (sc2) an immediate superclass of a dictionary that is<span class="idiff left right deletion" style="background-color: #fac5cd;"> Paterson-smaller</span></span></span>
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<td class="old_line diff-line-num old" data-linenumber="1548" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #fac5cd; border-right-style: solid; padding: inherit;" align="right" bgcolor="#f9d7dc">
1548
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<td class="new_line diff-line-num old" data-linenumber="1547" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #fac5cd; border-right-style: solid; padding: inherit;" align="right" bgcolor="#f9d7dc">
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<td class="line_content old" style="padding: inherit;" bgcolor="#fbe9eb"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'>-<span id="LC1548" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;"> than the instance head</span></span>
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<td class="old_line diff-line-num new" data-linenumber="1549" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
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<td class="new_line diff-line-num new" data-linenumber="1547" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1547
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'>+<span id="LC1547" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;"> (sc2) an immediate superclass of a dictionary that is</span></span>
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<td class="new_line diff-line-num new" data-linenumber="1548" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1548
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'>+<span id="LC1548" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;"> <span class="idiff left right addition" style="background-color: #c7f0d2;">/Paterson-smaller/ </span>than the instance head</span></span>
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1549
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<td class="new_line diff-line-num" data-linenumber="1549" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #f0f0f0; border-right-style: solid; padding: inherit;" align="right" bgcolor="#fafafa">
1549
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<td class="line_content" style="padding: inherit;"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'> <span id="LC1549" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;"> See Note [The PatersonSize of a type] in GHC.Tc.Utils.TcType</span></span>
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1550
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<td class="new_line diff-line-num" data-linenumber="1550" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #f0f0f0; border-right-style: solid; padding: inherit;" align="right" bgcolor="#fafafa">
1550
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<td class="line_content" style="padding: inherit;"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'> <span id="LC1550" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;"> (sc3) a call of a dfun (always returns a dictionary constructor)</span></span>
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1551
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1551
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<td class="line_content" style="padding: inherit;"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'> <span id="LC1551" class="line" lang="haskell"></span>
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<td class="diff-line-num unfold js-unfold old_line" data-linenumber="1567" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #f0f0f0; border-right-style: solid; padding: inherit;" align="right" bgcolor="#fafafa">...</td>
<td class="diff-line-num unfold js-unfold new_line" data-linenumber="1567" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #f0f0f0; border-right-style: solid; padding: inherit;" align="right" bgcolor="#fafafa">...</td>
<td class="line_content match" style="color: rgba(0,0,0,0.3); padding: inherit;" bgcolor="#fafafa">@@ -1567,34 +1567,43 @@ Here is an example, taken from CmmExpr:</td>
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1567
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<td class="new_line diff-line-num" data-linenumber="1567" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #f0f0f0; border-right-style: solid; padding: inherit;" align="right" bgcolor="#fafafa">
1567
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<td class="line_content" style="padding: inherit;"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'> <span id="LC1567" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">(i1) instance UserOfRegs r a => UserOfRegs r (Maybe a) where</span></span>
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1568
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1568
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<td class="line_content" style="padding: inherit;"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'> <span id="LC1568" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">(i2) instance (Ord r, UserOfRegs r CmmReg) => UserOfRegs r CmmExpr where</span></span>
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1569
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1569
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<td class="line_content" style="padding: inherit;"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'> <span id="LC1569" class="line" lang="haskell"></span>
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1570
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<td class="new_line diff-line-num old" data-linenumber="1570" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #fac5cd; border-right-style: solid; padding: inherit;" align="right" bgcolor="#f9d7dc">
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<td class="line_content old" style="padding: inherit;" bgcolor="#fbe9eb"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'>-<span id="LC1570" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">For (i1) we can get the (Ord r) superclass by selection from (UserOfRegs r a),</span></span>
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1571
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<td class="line_content old" style="padding: inherit;" bgcolor="#fbe9eb"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'>-<span id="LC1571" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">since it is smaller than the thing we are building (UserOfRegs r (Maybe a)).</span></span>
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<td class="old_line diff-line-num new" data-linenumber="1572" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
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<td class="new_line diff-line-num new" data-linenumber="1570" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1570
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'>+<span id="LC1570" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">For (i1) we can get the (Ord r) superclass by selection from</span></span>
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<td class="old_line diff-line-num new" data-linenumber="1572" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
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<td class="new_line diff-line-num new" data-linenumber="1571" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1571
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'>+<span id="LC1571" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">(UserOfRegs r a), since it (i.e. UserOfRegs r a) is smaller than the</span></span>
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<td class="new_line diff-line-num new" data-linenumber="1572" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1572
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'>+<span id="LC1572" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">thing we are building, namely (UserOfRegs r (Maybe a)).</span></span>
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1572
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<td class="new_line diff-line-num" data-linenumber="1573" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #f0f0f0; border-right-style: solid; padding: inherit;" align="right" bgcolor="#fafafa">
1573
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<td class="line_content" style="padding: inherit;"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'> <span id="LC1573" class="line" lang="haskell"></span>
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<td class="old_line diff-line-num old" data-linenumber="1573" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #fac5cd; border-right-style: solid; padding: inherit;" align="right" bgcolor="#f9d7dc">
1573
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<td class="new_line diff-line-num old" data-linenumber="1574" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #fac5cd; border-right-style: solid; padding: inherit;" align="right" bgcolor="#f9d7dc">
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<td class="line_content old" style="padding: inherit;" bgcolor="#fbe9eb"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'>-<span id="LC1573" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">But for (i2) that isn't the case, so we must add an explicit, and</span></span>
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<td class="old_line diff-line-num old" data-linenumber="1574" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #fac5cd; border-right-style: solid; padding: inherit;" align="right" bgcolor="#f9d7dc">
1574
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<td class="new_line diff-line-num old" data-linenumber="1574" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #fac5cd; border-right-style: solid; padding: inherit;" align="right" bgcolor="#f9d7dc">
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<td class="line_content old" style="padding: inherit;" bgcolor="#fbe9eb"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'>-<span id="LC1574" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">perhaps surprising, (Ord r) argument to the instance declaration.</span></span>
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<td class="old_line diff-line-num new" data-linenumber="1575" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
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<td class="new_line diff-line-num new" data-linenumber="1574" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1574
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'>+<span id="LC1574" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">But for (i2) that isn't the case: (UserOfRegs r CmmReg) is not smaller</span></span>
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<td class="new_line diff-line-num new" data-linenumber="1575" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1575
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'>+<span id="LC1575" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">than the thing we are building (UserOfRegs r CmmExpr), so we can't use</span></span>
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<td class="old_line diff-line-num new" data-linenumber="1575" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
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<td class="new_line diff-line-num new" data-linenumber="1576" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1576
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'>+<span id="LC1576" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">the superclasses of the former. Hence we must instead add an explicit,</span></span>
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<td class="new_line diff-line-num new" data-linenumber="1577" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1577
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'>+<span id="LC1577" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">and perhaps surprising, (Ord r) argument to the instance declaration.</span></span>
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1575
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<td class="new_line diff-line-num" data-linenumber="1578" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #f0f0f0; border-right-style: solid; padding: inherit;" align="right" bgcolor="#fafafa">
1578
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<td class="line_content" style="padding: inherit;"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'> <span id="LC1578" class="line" lang="haskell"></span>
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1576
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<td class="new_line diff-line-num" data-linenumber="1579" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #f0f0f0; border-right-style: solid; padding: inherit;" align="right" bgcolor="#fafafa">
1579
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<td class="line_content" style="padding: inherit;"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'> <span id="LC1579" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">Here's another example from #6161:</span></span>
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1577
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<td class="new_line diff-line-num" data-linenumber="1580" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #f0f0f0; border-right-style: solid; padding: inherit;" align="right" bgcolor="#fafafa">
1580
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<td class="line_content" style="padding: inherit;"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'> <span id="LC1580" class="line" lang="haskell"></span>
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<td class="old_line diff-line-num old" data-linenumber="1578" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #fac5cd; border-right-style: solid; padding: inherit;" align="right" bgcolor="#f9d7dc">
1578
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<td class="new_line diff-line-num old" data-linenumber="1581" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #fac5cd; border-right-style: solid; padding: inherit;" align="right" bgcolor="#f9d7dc">
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<td class="line_content old" style="padding: inherit;" bgcolor="#fbe9eb"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'>-<span id="LC1578" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;"> class Super a => Duper a where ...</span></span>
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<td class="old_line diff-line-num old" data-linenumber="1579" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #fac5cd; border-right-style: solid; padding: inherit;" align="right" bgcolor="#f9d7dc">
1579
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<td class="new_line diff-line-num old" data-linenumber="1581" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #fac5cd; border-right-style: solid; padding: inherit;" align="right" bgcolor="#f9d7dc">
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<td class="line_content old" style="padding: inherit;" bgcolor="#fbe9eb"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'>-<span id="LC1579" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;"> class Duper (<span class="idiff left right deletion" style="background-color: #fac5cd;">Fam</span> a) => Foo a where ...</span></span>
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<td class="old_line diff-line-num old" data-linenumber="1580" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #fac5cd; border-right-style: solid; padding: inherit;" align="right" bgcolor="#f9d7dc">
1580
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<td class="new_line diff-line-num old" data-linenumber="1581" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #fac5cd; border-right-style: solid; padding: inherit;" align="right" bgcolor="#f9d7dc">
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<td class="line_content old" style="padding: inherit;" bgcolor="#fbe9eb"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'>-<span id="LC1580" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">(i3) instance Foo a => Duper (<span class="idiff left right deletion" style="background-color: #fac5cd;">Fam</span> a) where ...</span></span>
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1581
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<td class="new_line diff-line-num old" data-linenumber="1581" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #fac5cd; border-right-style: solid; padding: inherit;" align="right" bgcolor="#f9d7dc">
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<td class="line_content old" style="padding: inherit;" bgcolor="#fbe9eb"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'>-<span id="LC1581" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">(i4) instance Foo Float where ...</span></span>
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<td class="new_line diff-line-num new" data-linenumber="1581" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1581
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'>+<span id="LC1581" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;"> class <span class="idiff left right addition" style="background-color: #c7f0d2;"> </span>Super a => Duper a where ...</span></span>
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<td class="new_line diff-line-num new" data-linenumber="1582" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1582
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'>+<span id="LC1582" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;"> class Duper (<span class="idiff left right addition" style="background-color: #c7f0d2;">Maybe</span> a) => Foo a where ...</span></span>
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<td class="new_line diff-line-num new" data-linenumber="1583" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1583
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'>+<span id="LC1583" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">(i3) instance Foo a => Duper (<span class="idiff left right addition" style="background-color: #c7f0d2;">Maybe</span> a) where ...</span></span>
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<td class="new_line diff-line-num new" data-linenumber="1584" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1584
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'>+<span id="LC1584" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">(i4) instance <span class="idiff left right addition" style="background-color: #c7f0d2;"> </span>Foo Float where ...</span></span>
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1582
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<td class="new_line diff-line-num" data-linenumber="1585" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #f0f0f0; border-right-style: solid; padding: inherit;" align="right" bgcolor="#fafafa">
1585
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<td class="line_content" style="padding: inherit;"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'> <span id="LC1585" class="line" lang="haskell"></span>
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<td class="old_line diff-line-num" data-linenumber="1583" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #f0f0f0; border-right-style: solid; padding: inherit;" align="right" bgcolor="#fafafa">
1583
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<td class="new_line diff-line-num" data-linenumber="1586" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #f0f0f0; border-right-style: solid; padding: inherit;" align="right" bgcolor="#fafafa">
1586
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<td class="line_content" style="padding: inherit;"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'> <span id="LC1586" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">It would be horribly wrong to define</span></span>
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<td class="old_line diff-line-num old" data-linenumber="1584" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #fac5cd; border-right-style: solid; padding: inherit;" align="right" bgcolor="#f9d7dc">
1584
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<td class="new_line diff-line-num old" data-linenumber="1587" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #fac5cd; border-right-style: solid; padding: inherit;" align="right" bgcolor="#f9d7dc">
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<td class="line_content old" style="padding: inherit;" bgcolor="#fbe9eb"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'>-<span id="LC1584" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;"> dfDuper<span class="idiff left deletion" style="background-color: #fac5cd;">Fam</span> :: Foo a -> Duper (<span class="idiff right deletion" style="background-color: #fac5cd;">Fam</span> a) -- from (i3)</span></span>
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<td class="old_line diff-line-num old" data-linenumber="1585" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #fac5cd; border-right-style: solid; padding: inherit;" align="right" bgcolor="#f9d7dc">
1585
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<td class="new_line diff-line-num old" data-linenumber="1587" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #fac5cd; border-right-style: solid; padding: inherit;" align="right" bgcolor="#f9d7dc">
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<td class="line_content old" style="padding: inherit;" bgcolor="#fbe9eb"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'>-<span id="LC1585" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;"> dfDuper<span class="idiff left right deletion" style="background-color: #fac5cd;">Fam</span> d = MkDuper (sc_sel1 (sc_sel2 d)) ...</span></span>
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<td class="old_line diff-line-num new" data-linenumber="1586" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
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<td class="new_line diff-line-num new" data-linenumber="1587" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1587
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'>+<span id="LC1587" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;"> dfDuper<span class="idiff left addition" style="background-color: #c7f0d2;">Maybe</span> :: Foo a -> Duper (<span class="idiff right addition" style="background-color: #c7f0d2;">Maybe</span> a) -- from (i3)</span></span>
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<td class="new_line diff-line-num new" data-linenumber="1588" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1588
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'>+<span id="LC1588" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;"> dfDuper<span class="idiff left right addition" style="background-color: #c7f0d2;">Maybe</span> d = MkDuper (sc_sel1 (sc_sel2 d)) ...</span></span>
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1586
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<td class="new_line diff-line-num" data-linenumber="1589" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #f0f0f0; border-right-style: solid; padding: inherit;" align="right" bgcolor="#fafafa">
1589
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<td class="line_content" style="padding: inherit;"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'> <span id="LC1589" class="line" lang="haskell"></span>
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<td class="old_line diff-line-num" data-linenumber="1587" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #f0f0f0; border-right-style: solid; padding: inherit;" align="right" bgcolor="#fafafa">
1587
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<td class="new_line diff-line-num" data-linenumber="1590" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #f0f0f0; border-right-style: solid; padding: inherit;" align="right" bgcolor="#fafafa">
1590
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<td class="line_content" style="padding: inherit;"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'> <span id="LC1590" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;"> dfFooFloat :: Foo Float -- from (i4)</span></span>
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<td class="old_line diff-line-num old" data-linenumber="1588" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #fac5cd; border-right-style: solid; padding: inherit;" align="right" bgcolor="#f9d7dc">
1588
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<td class="new_line diff-line-num old" data-linenumber="1591" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #fac5cd; border-right-style: solid; padding: inherit;" align="right" bgcolor="#f9d7dc">
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<td class="line_content old" style="padding: inherit;" bgcolor="#fbe9eb"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'>-<span id="LC1588" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;"> dfFooFloat = MkFoo (dfDuperFam dfFooFloat) ...</span></span>
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1589
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<td class="new_line diff-line-num old" data-linenumber="1591" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #fac5cd; border-right-style: solid; padding: inherit;" align="right" bgcolor="#f9d7dc">
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<td class="line_content old" style="padding: inherit;" bgcolor="#fbe9eb"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'>-<span id="LC1589" class="line" lang="haskell"></span>
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<td class="old_line diff-line-num old" data-linenumber="1590" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #fac5cd; border-right-style: solid; padding: inherit;" align="right" bgcolor="#f9d7dc">
1590
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<td class="new_line diff-line-num old" data-linenumber="1591" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #fac5cd; border-right-style: solid; padding: inherit;" align="right" bgcolor="#f9d7dc">
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<td class="line_content old" style="padding: inherit;" bgcolor="#fbe9eb"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'>-<span id="LC1590" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">Now the Super superclass of Duper is definitely bottom!</span></span>
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1591
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<td class="new_line diff-line-num old" data-linenumber="1591" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #fac5cd; border-right-style: solid; padding: inherit;" align="right" bgcolor="#f9d7dc">
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<td class="line_content old" style="padding: inherit;" bgcolor="#fbe9eb"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'>-<span id="LC1591" class="line" lang="haskell"></span>
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<td class="old_line diff-line-num old" data-linenumber="1592" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #fac5cd; border-right-style: solid; padding: inherit;" align="right" bgcolor="#f9d7dc">
1592
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<td class="new_line diff-line-num old" data-linenumber="1591" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #fac5cd; border-right-style: solid; padding: inherit;" align="right" bgcolor="#f9d7dc">
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<td class="line_content old" style="padding: inherit;" bgcolor="#fbe9eb"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'>-<span id="LC1592" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">This won't happen because when processing (i3) we can use the</span></span>
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1593
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<td class="new_line diff-line-num old" data-linenumber="1591" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #fac5cd; border-right-style: solid; padding: inherit;" align="right" bgcolor="#f9d7dc">
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<td class="line_content old" style="padding: inherit;" bgcolor="#fbe9eb"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'>-<span id="LC1593" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">superclasses of (Foo a), which is smaller than the head Duper (Fam a).</span></span>
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<td class="old_line diff-line-num old" data-linenumber="1594" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #fac5cd; border-right-style: solid; padding: inherit;" align="right" bgcolor="#f9d7dc">
1594
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<td class="new_line diff-line-num old" data-linenumber="1591" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #fac5cd; border-right-style: solid; padding: inherit;" align="right" bgcolor="#f9d7dc">
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<td class="line_content old" style="padding: inherit;" bgcolor="#fbe9eb"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'>-<span id="LC1594" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">This superclass is Duper (Fam a). But that is *not* smaller than the</span></span>
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1595
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<td class="new_line diff-line-num old" data-linenumber="1591" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #fac5cd; border-right-style: solid; padding: inherit;" align="right" bgcolor="#f9d7dc">
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<td class="line_content old" style="padding: inherit;" bgcolor="#fbe9eb"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'>-<span id="LC1595" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">head so we can't take *its* superclasses. As a result the program is</span></span>
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<td class="old_line diff-line-num old" data-linenumber="1596" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #fac5cd; border-right-style: solid; padding: inherit;" align="right" bgcolor="#f9d7dc">
1596
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<td class="new_line diff-line-num old" data-linenumber="1591" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #fac5cd; border-right-style: solid; padding: inherit;" align="right" bgcolor="#f9d7dc">
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<td class="line_content old" style="padding: inherit;" bgcolor="#fbe9eb"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'>-<span id="LC1596" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">rightly rejected, unless you add (Super (Fam a)) to the context of</span></span>
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<td class="old_line diff-line-num old" data-linenumber="1597" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #fac5cd; border-right-style: solid; padding: inherit;" align="right" bgcolor="#f9d7dc">
1597
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<td class="new_line diff-line-num old" data-linenumber="1591" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #fac5cd; border-right-style: solid; padding: inherit;" align="right" bgcolor="#f9d7dc">
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<td class="line_content old" style="padding: inherit;" bgcolor="#fbe9eb"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'>-<span id="LC1597" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">(i3).</span></span>
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<td class="old_line diff-line-num new" data-linenumber="1598" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
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<td class="new_line diff-line-num new" data-linenumber="1591" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1591
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'>+<span id="LC1591" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;"> dfFooFloat = MkFoo (dfDuperMaybe dfFooFloat) ...</span></span>
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<td class="new_line diff-line-num new" data-linenumber="1592" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1592
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'>+<span id="LC1592" class="line" lang="haskell"></span>
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<td class="old_line diff-line-num new" data-linenumber="1598" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
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<td class="new_line diff-line-num new" data-linenumber="1593" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1593
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'>+<span id="LC1593" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">Let's expand the RHS of dfFooFloat:</span></span>
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<td class="old_line diff-line-num new" data-linenumber="1598" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
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<td class="new_line diff-line-num new" data-linenumber="1594" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1594
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'>+<span id="LC1594" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;"> dfFooFloat = MkFoo (MkDuper (sc_sel1 (sc_sel2 dfFooFloat)) ...) ...</span></span>
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<td class="new_line diff-line-num new" data-linenumber="1595" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1595
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'>+<span id="LC1595" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">That superclass argument to MkDuper is bottom!</span></span>
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<td class="new_line diff-line-num new" data-linenumber="1596" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1596
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'>+<span id="LC1596" class="line" lang="haskell"></span>
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<td class="new_line diff-line-num new" data-linenumber="1597" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1597
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'>+<span id="LC1597" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">This program gets rejected because:</span></span>
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<td class="new_line diff-line-num new" data-linenumber="1598" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1598
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'>+<span id="LC1598" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">* When processing (i3) we need to construct a dictionary for Super</span></span>
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<td class="new_line diff-line-num new" data-linenumber="1599" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1599
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'>+<span id="LC1599" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;"> (Maybe a), to put in the superclass field of (Duper (Maybe a)).</span></span>
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<td class="new_line diff-line-num new" data-linenumber="1600" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1600
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'>+<span id="LC1600" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">* We /can/ use the superclasses of (Foo a), because the latter is</span></span>
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<td class="new_line diff-line-num new" data-linenumber="1601" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1601
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'>+<span id="LC1601" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;"> smaller than the head of the instance, namely Duper (Maybe a).</span></span>
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<td class="old_line diff-line-num new" data-linenumber="1598" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
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<td class="new_line diff-line-num new" data-linenumber="1602" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1602
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'>+<span id="LC1602" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">* So we know (by (sc2)) that this Duper (Maybe a) dictionary is</span></span>
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<td class="new_line diff-line-num new" data-linenumber="1603" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1603
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'>+<span id="LC1603" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;"> non-bottom. But because (Duper (Maybe a)) is not smaller than the</span></span>
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<td class="new_line diff-line-num new" data-linenumber="1604" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1604
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'>+<span id="LC1604" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;"> instance head (Duper (Maybe a)), we can't take *its* superclasses.</span></span>
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<td class="new_line diff-line-num new" data-linenumber="1605" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1605
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'>+<span id="LC1605" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">As a result the program is rightly rejected, unless you add</span></span>
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<td class="new_line diff-line-num new" data-linenumber="1606" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1606
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'>+<span id="LC1606" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">(Super (Maybe a)) to the context of (i3).</span></span>
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1598
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1607
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<td class="line_content" style="padding: inherit;"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'> <span id="LC1607" class="line" lang="haskell"></span>
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1599
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1608
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<td class="line_content" style="padding: inherit;"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'> <span id="LC1608" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">Note [Solving superclass constraints]</span></span>
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1600
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1609
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<td class="line_content" style="padding: inherit;"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'> <span id="LC1609" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~</span></span>
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<a href="https://gitlab.haskell.org/ghc/ghc/-/commit/eb62d802e3bafa2474ff39ac30a5c5cd69ea9cef#1db07ed8cd9bab6b217a8f5a140176d3cb8672fd" style="color: #1068bf;"><strong style="font-weight: bold;">compiler/GHC/Tc/Validity.hs</strong></a>
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<td class="line_content match" style="color: rgba(0,0,0,0.3); padding: inherit;" bgcolor="#fafafa">@@ -1715,31 +1715,44 @@ The Paterson Conditions ensure termination of instance resolution.</td>
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1715
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1715
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<td class="line_content" style="padding: inherit;"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'> <span id="LC1715" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">Given an instance declaration</span></span>
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1716
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1716
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<td class="line_content" style="padding: inherit;"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'> <span id="LC1716" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;"> instance (..., C t1.. tn, ...) => D s1 .. sm</span></span>
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1717
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1717
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<td class="line_content" style="padding: inherit;"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'> <span id="LC1717" class="line" lang="haskell"></span>
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1718
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<td class="new_line diff-line-num old" data-linenumber="1718" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #fac5cd; border-right-style: solid; padding: inherit;" align="right" bgcolor="#f9d7dc">
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<td class="line_content old" style="padding: inherit;" bgcolor="#fbe9eb"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'>-<span id="LC1718" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">for each class constraint (C t1 ... tn) in the context we check that</span></span>
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1718
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'>+<span id="LC1718" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">we check that each constraint in the context of the instance is</span></span>
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<td class="new_line diff-line-num new" data-linenumber="1719" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1719
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'>+<span id="LC1719" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">"Paterson-smaller" than the instance head. The underlying idea of</span></span>
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1720
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'>+<span id="LC1720" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">Paterson-smaller is that</span></span>
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1719
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1721
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<td class="line_content" style="padding: inherit;"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'> <span id="LC1721" class="line" lang="haskell"></span>
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1720
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<td class="new_line diff-line-num old" data-linenumber="1722" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #fac5cd; border-right-style: solid; padding: inherit;" align="right" bgcolor="#f9d7dc">
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<td class="line_content old" style="padding: inherit;" bgcolor="#fbe9eb"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'>-<span id="LC1720" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">(PC1) No type variable has more occurrences in the constraint than in the head</span></span>
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1722
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'>+<span id="LC1722" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;"> For any ground substitution S, for each constraint P in the</span></span>
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<td class="new_line diff-line-num new" data-linenumber="1723" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1723
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'>+<span id="LC1723" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;"> context, S(P) has fewer type constructors, counting repetitions,</span></span>
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1724
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'>+<span id="LC1724" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;"> than the head S(H)</span></span>
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1721
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1725
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<td class="line_content" style="padding: inherit;"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'> <span id="LC1725" class="line" lang="haskell"></span>
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1722
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<td class="new_line diff-line-num old" data-linenumber="1726" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #fac5cd; border-right-style: solid; padding: inherit;" align="right" bgcolor="#f9d7dc">
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<td class="line_content old" style="padding: inherit;" bgcolor="#fbe9eb"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'>-<span id="LC1722" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">(PC2) The constraint has fewer constructors and variables (taken together and</span></span>
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1723
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<td class="line_content old" style="padding: inherit;" bgcolor="#fbe9eb"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'>-<span id="LC1723" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;"> counting repetitions) than the head</span></span>
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1726
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'>+<span id="LC1726" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">More precisely, a constraint P is Paterson-smaller than H iff</span></span>
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1724
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<td class="new_line diff-line-num" data-linenumber="1727" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #f0f0f0; border-right-style: solid; padding: inherit;" align="right" bgcolor="#fafafa">
1727
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<td class="line_content" style="padding: inherit;"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'> <span id="LC1727" class="line" lang="haskell"></span>
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<td class="old_line diff-line-num old" data-linenumber="1725" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #fac5cd; border-right-style: solid; padding: inherit;" align="right" bgcolor="#f9d7dc">
1725
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<td class="new_line diff-line-num old" data-linenumber="1728" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #fac5cd; border-right-style: solid; padding: inherit;" align="right" bgcolor="#f9d7dc">
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<td class="line_content old" style="padding: inherit;" bgcolor="#fbe9eb"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'>-<span id="LC1725" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">(PC3) The constraint mentions no type functions. A type function</span></span>
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1726
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<td class="new_line diff-line-num old" data-linenumber="1728" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #fac5cd; border-right-style: solid; padding: inherit;" align="right" bgcolor="#f9d7dc">
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<td class="line_content old" style="padding: inherit;" bgcolor="#fbe9eb"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'>-<span id="LC1726" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;"> application can in principle expand to a type of arbitrary size, and</span></span>
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1727
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<td class="new_line diff-line-num old" data-linenumber="1728" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #fac5cd; border-right-style: solid; padding: inherit;" align="right" bgcolor="#f9d7dc">
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<td class="line_content old" style="padding: inherit;" bgcolor="#fbe9eb"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'>-<span id="LC1727" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;"> so are rejected out of hand</span></span>
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<td class="new_line diff-line-num new" data-linenumber="1728" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1728
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'>+<span id="LC1728" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">(PC1) No type variable has more (shallow) occurrences in P than in H.</span></span>
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1728
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<td class="new_line diff-line-num" data-linenumber="1729" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #f0f0f0; border-right-style: solid; padding: inherit;" align="right" bgcolor="#fafafa">
1729
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<td class="line_content" style="padding: inherit;"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'> <span id="LC1729" class="line" lang="haskell"></span>
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<td class="old_line diff-line-num old" data-linenumber="1729" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #fac5cd; border-right-style: solid; padding: inherit;" align="right" bgcolor="#f9d7dc">
1729
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<td class="new_line diff-line-num old" data-linenumber="1730" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #fac5cd; border-right-style: solid; padding: inherit;" align="right" bgcolor="#f9d7dc">
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<td class="line_content old" style="padding: inherit;" bgcolor="#fbe9eb"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'>-<span id="LC1729" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">The underlying idea is that</span></span>
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<td class="new_line diff-line-num new" data-linenumber="1730" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1730
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'>+<span id="LC1730" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;"> (If not, a substitution that replaces that variable with a big type</span></span>
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<td class="new_line diff-line-num new" data-linenumber="1731" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1731
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'>+<span id="LC1731" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;"> would make P have many more type constructors than H. Side note: we</span></span>
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<td class="new_line diff-line-num new" data-linenumber="1732" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1732
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'>+<span id="LC1732" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;"> could in principle skip this test for a variable of kind Bool,</span></span>
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<td class="new_line diff-line-num new" data-linenumber="1733" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1733
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'>+<span id="LC1733" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;"> since there are no big ground types we can substitute for it.)</span></span>
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1730
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<td class="new_line diff-line-num" data-linenumber="1734" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #f0f0f0; border-right-style: solid; padding: inherit;" align="right" bgcolor="#fafafa">
1734
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<td class="line_content" style="padding: inherit;"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'> <span id="LC1734" class="line" lang="haskell"></span>
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1731
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<td class="new_line diff-line-num old" data-linenumber="1735" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #fac5cd; border-right-style: solid; padding: inherit;" align="right" bgcolor="#f9d7dc">
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<td class="line_content old" style="padding: inherit;" bgcolor="#fbe9eb"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'>-<span id="LC1731" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;"> for any ground substitution, each assertion in the</span></span>
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1732
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<td class="new_line diff-line-num old" data-linenumber="1735" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #fac5cd; border-right-style: solid; padding: inherit;" align="right" bgcolor="#f9d7dc">
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<td class="line_content old" style="padding: inherit;" bgcolor="#fbe9eb"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'>-<span id="LC1732" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;"> context has fewer type constructors than the head.</span></span>
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<td class="new_line diff-line-num new" data-linenumber="1735" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1735
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'>+<span id="LC1735" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">(PC2) The constraint P has fewer constructors and variables (taken</span></span>
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<td class="new_line diff-line-num new" data-linenumber="1736" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1736
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'>+<span id="LC1736" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;"> together and counting repetitions) than the head H. This size</span></span>
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<td class="new_line diff-line-num new" data-linenumber="1737" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1737
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'>+<span id="LC1737" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;"> metric is computed by sizeType.</span></span>
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1738
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'>+<span id="LC1738" class="line" lang="haskell"></span>
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1739
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'>+<span id="LC1739" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;"> (A substitution that replaces each variable with Int demonstrates</span></span>
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1740
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'>+<span id="LC1740" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;"> the need.)</span></span>
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1741
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'>+<span id="LC1741" class="line" lang="haskell"></span>
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<td class="new_line diff-line-num new" data-linenumber="1742" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1742
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'>+<span id="LC1742" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">(PC3) The constraint P mentions no type functions.</span></span>
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1743
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'>+<span id="LC1743" class="line" lang="haskell"></span>
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<td class="new_line diff-line-num new" data-linenumber="1744" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1744
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'>+<span id="LC1744" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;"> (A type function application can in principle expand to a type of</span></span>
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<td class="new_line diff-line-num new" data-linenumber="1745" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1745
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'>+<span id="LC1745" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;"> arbitrary size, and so are rejected out of hand.)</span></span>
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1733
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<td class="new_line diff-line-num" data-linenumber="1746" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #f0f0f0; border-right-style: solid; padding: inherit;" align="right" bgcolor="#fafafa">
1746
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<td class="line_content" style="padding: inherit;"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'> <span id="LC1746" class="line" lang="haskell"></span>
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1734
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<td class="new_line diff-line-num" data-linenumber="1747" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #f0f0f0; border-right-style: solid; padding: inherit;" align="right" bgcolor="#fafafa">
1747
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<td class="line_content" style="padding: inherit;"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'> <span id="LC1747" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">(See Section 5 of "Understanding functional dependencies via Constraint</span></span>
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1735
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<td class="new_line diff-line-num" data-linenumber="1748" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #f0f0f0; border-right-style: solid; padding: inherit;" align="right" bgcolor="#fafafa">
1748
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<td class="line_content" style="padding: inherit;"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'> <span id="LC1748" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">Handling Rules", JFP Jan 2007; and the user manual section "Instance</span></span>
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1736
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<td class="new_line diff-line-num" data-linenumber="1749" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #f0f0f0; border-right-style: solid; padding: inherit;" align="right" bgcolor="#fafafa">
1749
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<td class="line_content" style="padding: inherit;"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'> <span id="LC1749" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">termiantion rules".</span></span>
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1737
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<td class="new_line diff-line-num" data-linenumber="1750" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #f0f0f0; border-right-style: solid; padding: inherit;" align="right" bgcolor="#fafafa">
1750
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<td class="line_content" style="padding: inherit;"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'> <span id="LC1750" class="line" lang="haskell"></span>
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1738
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<td class="new_line diff-line-num" data-linenumber="1751" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #f0f0f0; border-right-style: solid; padding: inherit;" align="right" bgcolor="#fafafa">
1751
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<td class="line_content" style="padding: inherit;"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'> <span id="LC1751" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">We measure "size" with the data type PatersonSize, in GHC.Tc.Utils.TcType.</span></span>
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<td class="old_line diff-line-num old" data-linenumber="1739" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #fac5cd; border-right-style: solid; padding: inherit;" align="right" bgcolor="#f9d7dc">
1739
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<td class="new_line diff-line-num old" data-linenumber="1752" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #fac5cd; border-right-style: solid; padding: inherit;" align="right" bgcolor="#f9d7dc">
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<td class="line_content old" style="padding: inherit;" bgcolor="#fbe9eb"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'>-<span id="LC1739" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;"><span class="idiff left right deletion" style="background-color: #fac5cd;"> </span> data PatersonSize</span></span>
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<td class="old_line diff-line-num old" data-linenumber="1740" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #fac5cd; border-right-style: solid; padding: inherit;" align="right" bgcolor="#f9d7dc">
1740
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<td class="new_line diff-line-num old" data-linenumber="1752" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #fac5cd; border-right-style: solid; padding: inherit;" align="right" bgcolor="#f9d7dc">
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<td class="line_content old" style="padding: inherit;" bgcolor="#fbe9eb"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'>-<span id="LC1740" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;"> <span class="idiff left right deletion" style="background-color: #fac5cd;"> </span>= PS_TyFam TyCon</span></span>
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<td class="old_line diff-line-num old" data-linenumber="1741" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #fac5cd; border-right-style: solid; padding: inherit;" align="right" bgcolor="#f9d7dc">
1741
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<td class="new_line diff-line-num old" data-linenumber="1752" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #fac5cd; border-right-style: solid; padding: inherit;" align="right" bgcolor="#f9d7dc">
</td>
<td class="line_content old" style="padding: inherit;" bgcolor="#fbe9eb"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'>-<span id="LC1741" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;"> <span class="idiff left right deletion" style="background-color: #fac5cd;"> </span>| PS_Vanilla { ps_tvs :: [TyVar] -- Free tyvars, including repetitions;</span></span>
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1742
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<td class="new_line diff-line-num old" data-linenumber="1752" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #fac5cd; border-right-style: solid; padding: inherit;" align="right" bgcolor="#f9d7dc">
</td>
<td class="line_content old" style="padding: inherit;" bgcolor="#fbe9eb"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'>-<span id="LC1742" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;"> <span class="idiff left right deletion" style="background-color: #fac5cd;"> </span>, ps_size :: Int} -- Number of type constructors and variables</span></span>
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<td class="new_line diff-line-num new" data-linenumber="1752" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1752
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'>+<span id="LC1752" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;"> data PatersonSize</span></span>
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<td class="new_line diff-line-num new" data-linenumber="1753" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1753
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'>+<span id="LC1753" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;"> = PS_TyFam TyCon</span></span>
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1754
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'>+<span id="LC1754" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;"> | PS_Vanilla { ps_tvs :: [TyVar] -- Free tyvars, including repetitions;</span></span>
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1755
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'>+<span id="LC1755" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;"> , ps_size :: Int} -- Number of type constructors and variables</span></span>
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1743
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1756
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<td class="line_content" style="padding: inherit;"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'> <span id="LC1756" class="line" lang="haskell"></span>
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1744
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1757
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<td class="line_content" style="padding: inherit;"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'> <span id="LC1757" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">* ps_tvs deals with (PC1)</span></span>
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1758
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<td class="line_content" style="padding: inherit;"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'> <span id="LC1758" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">* ps_size deals with (PC2)</span></span>
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<td class="diff-line-num unfold js-unfold old_line" data-linenumber="2111" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #f0f0f0; border-right-style: solid; padding: inherit;" align="right" bgcolor="#fafafa">...</td>
<td class="diff-line-num unfold js-unfold new_line" data-linenumber="2124" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #f0f0f0; border-right-style: solid; padding: inherit;" align="right" bgcolor="#fafafa">...</td>
<td class="line_content match" style="color: rgba(0,0,0,0.3); padding: inherit;" bgcolor="#fafafa">@@ -2111,10 +2124,10 @@ checkValidAssocTyFamDeflt fam_tc pats =</td>
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2111
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<td class="new_line diff-line-num" data-linenumber="2124" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #f0f0f0; border-right-style: solid; padding: inherit;" align="right" bgcolor="#fafafa">
2124
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<td class="line_content" style="padding: inherit;"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'> <span id="LC2124" class="line" lang="haskell"> <span class="n" style="color: #333;">suggestion</span> <span class="o" style="font-weight: 600;">=</span> <span class="n" style="color: #333;">text</span> <span class="s" style="color: #d14;">"The arguments to"</span> <span class="o" style="font-weight: 600;"><+></span> <span class="n" style="color: #333;">quotes</span> <span class="p">(</span><span class="n" style="color: #333;">ppr</span> <span class="n" style="color: #333;">fam_tc</span><span class="p">)</span></span>
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<td class="old_line diff-line-num" data-linenumber="2112" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #f0f0f0; border-right-style: solid; padding: inherit;" align="right" bgcolor="#fafafa">
2112
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<td class="new_line diff-line-num" data-linenumber="2125" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #f0f0f0; border-right-style: solid; padding: inherit;" align="right" bgcolor="#fafafa">
2125
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<td class="line_content" style="padding: inherit;"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'> <span id="LC2125" class="line" lang="haskell"> <span class="o" style="font-weight: 600;"><+></span> <span class="n" style="color: #333;">text</span> <span class="s" style="color: #d14;">"must all be distinct type variables"</span></span>
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2113
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<td class="new_line diff-line-num" data-linenumber="2126" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #f0f0f0; border-right-style: solid; padding: inherit;" align="right" bgcolor="#fafafa">
2126
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<td class="line_content" style="padding: inherit;"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'> <span id="LC2126" class="line" lang="haskell"></span>
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<td class="old_line diff-line-num old" data-linenumber="2114" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #fac5cd; border-right-style: solid; padding: inherit;" align="right" bgcolor="#f9d7dc">
2114
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<td class="new_line diff-line-num old" data-linenumber="2127" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #fac5cd; border-right-style: solid; padding: inherit;" align="right" bgcolor="#f9d7dc">
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<td class="line_content old" style="padding: inherit;" bgcolor="#fbe9eb"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'>-<span id="LC2114" class="line" lang="haskell"><span class="c1" style="color: #998; font-style: italic;">-- Make sure that each type family application is</span></span>
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<td class="old_line diff-line-num new" data-linenumber="2115" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
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<td class="new_line diff-line-num new" data-linenumber="2127" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
2127
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'>+<span id="LC2127" class="line" lang="haskell"><span class="c1" style="color: #998; font-style: italic;">-- Make sure that each type family application <span class="idiff left right addition" style="background-color: #c7f0d2;">in the RHS </span>is</span></span>
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2115
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<td class="new_line diff-line-num" data-linenumber="2128" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #f0f0f0; border-right-style: solid; padding: inherit;" align="right" bgcolor="#fafafa">
2128
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<td class="line_content" style="padding: inherit;"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'> <span id="LC2128" class="line" lang="haskell"><span class="c1" style="color: #998; font-style: italic;">-- (1) strictly smaller than the lhs,</span></span>
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<td class="old_line diff-line-num" data-linenumber="2116" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #f0f0f0; border-right-style: solid; padding: inherit;" align="right" bgcolor="#fafafa">
2116
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<td class="new_line diff-line-num" data-linenumber="2129" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #f0f0f0; border-right-style: solid; padding: inherit;" align="right" bgcolor="#fafafa">
2129
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<td class="line_content" style="padding: inherit;"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'> <span id="LC2129" class="line" lang="haskell"><span class="c1" style="color: #998; font-style: italic;">-- (2) mentions no type variable more often than the lhs, and</span></span>
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<td class="old_line diff-line-num old" data-linenumber="2117" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #fac5cd; border-right-style: solid; padding: inherit;" align="right" bgcolor="#f9d7dc">
2117
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<td class="new_line diff-line-num old" data-linenumber="2130" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #fac5cd; border-right-style: solid; padding: inherit;" align="right" bgcolor="#f9d7dc">
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<td class="line_content old" style="padding: inherit;" bgcolor="#fbe9eb"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'>-<span id="LC2117" class="line" lang="haskell"><span class="c1" style="color: #998; font-style: italic;">-- (3) does not contain any further type family <span class="idiff left right deletion" style="background-color: #fac5cd;">instances.</span></span></span>
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<td class="new_line diff-line-num new" data-linenumber="2130" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
2130
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'>+<span id="LC2130" class="line" lang="haskell"><span class="c1" style="color: #998; font-style: italic;">-- (3) does not contain any further type family <span class="idiff left right addition" style="background-color: #c7f0d2;">applications</span></span></span>
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2118
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<td class="new_line diff-line-num" data-linenumber="2131" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #f0f0f0; border-right-style: solid; padding: inherit;" align="right" bgcolor="#fafafa">
2131
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<td class="line_content" style="padding: inherit;"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'> <span id="LC2131" class="line" lang="haskell"><span class="c1" style="color: #998; font-style: italic;">--</span></span>
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2119
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<td class="new_line diff-line-num" data-linenumber="2132" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #f0f0f0; border-right-style: solid; padding: inherit;" align="right" bgcolor="#fafafa">
2132
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<td class="line_content" style="padding: inherit;"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'> <span id="LC2132" class="line" lang="haskell"><span class="n" style="color: #333;">checkFamInstRhs</span> <span class="o" style="font-weight: 600;">::</span> <span class="kt" style="color: #458; font-weight: 600;">TyCon</span> <span class="o" style="font-weight: 600;">-></span> <span class="p">[</span><span class="kt" style="color: #458; font-weight: 600;">Type</span><span class="p">]</span> <span class="c1" style="color: #998; font-style: italic;">-- LHS</span></span>
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2120
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<td class="new_line diff-line-num" data-linenumber="2133" style="width: 35px; color: rgba(0,0,0,0.3); border-right-width: 1px; border-right-color: #f0f0f0; border-right-style: solid; padding: inherit;" align="right" bgcolor="#fafafa">
2133
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<td class="line_content" style="padding: inherit;"><pre style='display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dbdbdb;'> <span id="LC2133" class="line" lang="haskell"> <span class="o" style="font-weight: 600;">-></span> <span class="p">[(</span><span class="kt" style="color: #458; font-weight: 600;">TyCon</span><span class="p">,</span> <span class="p">[</span><span class="kt" style="color: #458; font-weight: 600;">Type</span><span class="p">])]</span> <span class="c1" style="color: #998; font-style: italic;">-- type family calls in RHS</span></span>
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