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<h3 style="margin-top: 20px; margin-bottom: 10px;">
Simon Peyton Jones pushed to branch wip/T24676 at <a href="https://gitlab.haskell.org/ghc/ghc">Glasgow Haskell Compiler / GHC</a>
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Commits:
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<strong style="font-weight: bold;"><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/04d97afa95e35ea6bcdb14f1242d25f2b23190e2">04d97afa</a></strong>
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<span> by Simon Peyton Jones </span> <i> at 2024-05-13T11:56:45+01:00 </i>
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<pre class="commit-message" style='white-space: pre-wrap; display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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: #fbfafd; border-radius: 2px; margin: 0; padding: 8px 12px; border: 1px solid #dcdcde;'>Comments only...

.. relating to deep subsumption and visible (required) foralls.
See #24696
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1 changed file:
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<a href="#74295edeac870ee7f2f3484ebaffab5c948b735a">
compiler/GHC/Tc/Utils/Unify.hs
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Changes:
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<li id="74295edeac870ee7f2f3484ebaffab5c948b735a">
<a href="https://gitlab.haskell.org/ghc/ghc/-/commit/04d97afa95e35ea6bcdb14f1242d25f2b23190e2#74295edeac870ee7f2f3484ebaffab5c948b735a"><strong style="font-weight: bold;">compiler/GHC/Tc/Utils/Unify.hs</strong></a>
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<td class="diff-line-num unfold js-unfold new_line" data-linenumber="1638" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #ececef; border-right-style: solid; padding: inherit;" align="right" bgcolor="#fbfafd">...</td>
<td class="line_content match" style="color: rgba(31,30,36,0.24); padding: inherit;" bgcolor="#fbfafd">@@ -1638,8 +1638,17 @@ Consider (1)</td>
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<td class="new_line diff-line-num" data-linenumber="1638" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #ececef; border-right-style: solid; padding: inherit;" align="right" bgcolor="#fbfafd">
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<td class="line_content" style="padding: inherit;"><pre style='display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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 #dcdcde;'> <span id="LC1638" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">We must skolemise the `forall b` before instantiating the `forall a`.</span></span>
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<td class="new_line diff-line-num" data-linenumber="1639" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #ececef; border-right-style: solid; padding: inherit;" align="right" bgcolor="#fbfafd">
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<td class="line_content" style="padding: inherit;"><pre style='display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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 #dcdcde;'> <span id="LC1639" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">See also Note [Deep skolemisation].</span></span>
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<td class="line_content" style="padding: inherit;"><pre style='display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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 #dcdcde;'> <span id="LC1640" class="line" lang="haskell"></span>
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<td class="new_line diff-line-num old" data-linenumber="1641" style="width: 35px; color: rgba(31,30,36,0.24); 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: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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 #dcdcde;'>-<span id="LC1641" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">Note that we /always/ use shallow subsumption in the ambiguity check.</span></span>
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<td class="new_line diff-line-num old" data-linenumber="1641" style="width: 35px; color: rgba(31,30,36,0.24); 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: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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 #dcdcde;'>-<span id="LC1642" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">See Note [Ambiguity check and deep subsumption].</span></span>
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<td class="old_line diff-line-num new" data-linenumber="1643" style="width: 35px; color: rgba(31,30,36,0.24); 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="1641" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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 #dcdcde;'>+<span id="LC1641" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">Wrinkles:</span></span>
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<td class="new_line diff-line-num new" data-linenumber="1642" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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 #dcdcde;'>+<span id="LC1642" class="line" lang="haskell"></span>
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<td class="new_line diff-line-num new" data-linenumber="1643" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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 #dcdcde;'>+<span id="LC1643" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">(DS1) Note that we /always/ use shallow subsumption in the ambiguity check.</span></span>
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<td class="new_line diff-line-num new" data-linenumber="1644" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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 #dcdcde;'>+<span id="LC1644" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">      See Note [Ambiguity check and deep subsumption].</span></span>
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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 #dcdcde;'>+<span id="LC1645" class="line" lang="haskell"></span>
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<td class="new_line diff-line-num new" data-linenumber="1646" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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 #dcdcde;'>+<span id="LC1646" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">(DS2) Deep subsumption requires deep instantiation too.</span></span>
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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 #dcdcde;'>+<span id="LC1647" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">      See Note [The need for deep instantiation]</span></span>
</pre></td>
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<td class="old_line diff-line-num new" data-linenumber="1643" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
 
</td>
<td class="new_line diff-line-num new" data-linenumber="1648" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1648
</td>
<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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 #dcdcde;'>+<span id="LC1648" class="line" lang="haskell"></span>
</pre></td>
</tr>
<tr class="line_holder new" style="line-height: 1.6;">
<td class="old_line diff-line-num new" data-linenumber="1643" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
 
</td>
<td class="new_line diff-line-num new" data-linenumber="1649" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1649
</td>
<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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 #dcdcde;'>+<span id="LC1649" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">(DS3) The interaction between deep subsumption and required foralls</span></span>
</pre></td>
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<td class="old_line diff-line-num new" data-linenumber="1643" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
 
</td>
<td class="new_line diff-line-num new" data-linenumber="1650" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1650
</td>
<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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 #dcdcde;'>+<span id="LC1650" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">      (forall a -> ty) is a bit subtle.  See #24696 and</span></span>
</pre></td>
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<tr class="line_holder new" style="line-height: 1.6;">
<td class="old_line diff-line-num new" data-linenumber="1643" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
 
</td>
<td class="new_line diff-line-num new" data-linenumber="1651" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1651
</td>
<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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 #dcdcde;'>+<span id="LC1651" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">      Note [Deep subsumption and required foralls]</span></span>
</pre></td>
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<td class="old_line diff-line-num" data-linenumber="1643" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #ececef; border-right-style: solid; padding: inherit;" align="right" bgcolor="#fbfafd">
1643
</td>
<td class="new_line diff-line-num" data-linenumber="1652" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #ececef; border-right-style: solid; padding: inherit;" align="right" bgcolor="#fbfafd">
1652
</td>
<td class="line_content" style="padding: inherit;"><pre style='display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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 #dcdcde;'> <span id="LC1652" class="line" lang="haskell"></span>
</pre></td>
</tr>
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<td class="old_line diff-line-num" data-linenumber="1644" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #ececef; border-right-style: solid; padding: inherit;" align="right" bgcolor="#fbfafd">
1644
</td>
<td class="new_line diff-line-num" data-linenumber="1653" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #ececef; border-right-style: solid; padding: inherit;" align="right" bgcolor="#fbfafd">
1653
</td>
<td class="line_content" style="padding: inherit;"><pre style='display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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 #dcdcde;'> <span id="LC1653" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">Note [Deep skolemisation]</span></span>
</pre></td>
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<td class="old_line diff-line-num" data-linenumber="1645" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #ececef; border-right-style: solid; padding: inherit;" align="right" bgcolor="#fbfafd">
1645
</td>
<td class="new_line diff-line-num" data-linenumber="1654" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #ececef; border-right-style: solid; padding: inherit;" align="right" bgcolor="#fbfafd">
1654
</td>
<td class="line_content" style="padding: inherit;"><pre style='display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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 #dcdcde;'> <span id="LC1654" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">~~~~~~~~~~~~~~~~~~~~~~~~~</span></span>
</pre></td>
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<tr class="line_holder match" style="line-height: 1.6;">
<td class="diff-line-num unfold js-unfold old_line" data-linenumber="1715" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #ececef; border-right-style: solid; padding: inherit;" align="right" bgcolor="#fbfafd">...</td>
<td class="diff-line-num unfold js-unfold new_line" data-linenumber="1724" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #ececef; border-right-style: solid; padding: inherit;" align="right" bgcolor="#fbfafd">...</td>
<td class="line_content match" style="color: rgba(31,30,36,0.24); padding: inherit;" bgcolor="#fbfafd">@@ -1715,6 +1724,70 @@ complains.</td>
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1715
</td>
<td class="new_line diff-line-num" data-linenumber="1724" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #ececef; border-right-style: solid; padding: inherit;" align="right" bgcolor="#fbfafd">
1724
</td>
<td class="line_content" style="padding: inherit;"><pre style='display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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 #dcdcde;'> <span id="LC1724" class="line" lang="haskell"></span>
</pre></td>
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<td class="old_line diff-line-num" data-linenumber="1716" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #ececef; border-right-style: solid; padding: inherit;" align="right" bgcolor="#fbfafd">
1716
</td>
<td class="new_line diff-line-num" data-linenumber="1725" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #ececef; border-right-style: solid; padding: inherit;" align="right" bgcolor="#fbfafd">
1725
</td>
<td class="line_content" style="padding: inherit;"><pre style='display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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 #dcdcde;'> <span id="LC1725" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">The easiest solution was to use tcEqMult in tc_sub_type_deep, and</span></span>
</pre></td>
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<tr class="line_holder" style="line-height: 1.6;">
<td class="old_line diff-line-num" data-linenumber="1717" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #ececef; border-right-style: solid; padding: inherit;" align="right" bgcolor="#fbfafd">
1717
</td>
<td class="new_line diff-line-num" data-linenumber="1726" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #ececef; border-right-style: solid; padding: inherit;" align="right" bgcolor="#fbfafd">
1726
</td>
<td class="line_content" style="padding: inherit;"><pre style='display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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 #dcdcde;'> <span id="LC1726" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">insist on equality. This is only in the DeepSubsumption code anyway.</span></span>
</pre></td>
</tr>
<tr class="line_holder new" style="line-height: 1.6;">
<td class="old_line diff-line-num new" data-linenumber="1718" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
 
</td>
<td class="new_line diff-line-num new" data-linenumber="1727" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1727
</td>
<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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 #dcdcde;'>+<span id="LC1727" class="line" lang="haskell"></span>
</pre></td>
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<tr class="line_holder new" style="line-height: 1.6;">
<td class="old_line diff-line-num new" data-linenumber="1718" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
 
</td>
<td class="new_line diff-line-num new" data-linenumber="1728" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1728
</td>
<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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 #dcdcde;'>+<span id="LC1728" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">Note [The need for deep instantiation]</span></span>
</pre></td>
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<td class="old_line diff-line-num new" data-linenumber="1718" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
 
</td>
<td class="new_line diff-line-num new" data-linenumber="1729" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1729
</td>
<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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 #dcdcde;'>+<span id="LC1729" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~</span></span>
</pre></td>
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<tr class="line_holder new" style="line-height: 1.6;">
<td class="old_line diff-line-num new" data-linenumber="1718" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
 
</td>
<td class="new_line diff-line-num new" data-linenumber="1730" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1730
</td>
<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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 #dcdcde;'>+<span id="LC1730" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">Consider this, without Quick Look, but with Deep Subsumption:</span></span>
</pre></td>
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<td class="old_line diff-line-num new" data-linenumber="1718" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
 
</td>
<td class="new_line diff-line-num new" data-linenumber="1731" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1731
</td>
<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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 #dcdcde;'>+<span id="LC1731" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">   f :: ∀a b c. a b c -> Int</span></span>
</pre></td>
</tr>
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<td class="old_line diff-line-num new" data-linenumber="1718" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
 
</td>
<td class="new_line diff-line-num new" data-linenumber="1732" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1732
</td>
<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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 #dcdcde;'>+<span id="LC1732" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">   g :: Bool -> ∀d. d -> d</span></span>
</pre></td>
</tr>
<tr class="line_holder new" style="line-height: 1.6;">
<td class="old_line diff-line-num new" data-linenumber="1718" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
 
</td>
<td class="new_line diff-line-num new" data-linenumber="1733" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1733
</td>
<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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 #dcdcde;'>+<span id="LC1733" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">Consider the application (f g).  We need to do the subsumption test</span></span>
</pre></td>
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<td class="old_line diff-line-num new" data-linenumber="1718" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
 
</td>
<td class="new_line diff-line-num new" data-linenumber="1734" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1734
</td>
<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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 #dcdcde;'>+<span id="LC1734" class="line" lang="haskell"></span>
</pre></td>
</tr>
<tr class="line_holder new" style="line-height: 1.6;">
<td class="old_line diff-line-num new" data-linenumber="1718" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
 
</td>
<td class="new_line diff-line-num new" data-linenumber="1735" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1735
</td>
<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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 #dcdcde;'>+<span id="LC1735" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">  (Bool -> ∀ d. d->d)   <=   (alpha beta gamma)</span></span>
</pre></td>
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<td class="old_line diff-line-num new" data-linenumber="1718" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
 
</td>
<td class="new_line diff-line-num new" data-linenumber="1736" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1736
</td>
<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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 #dcdcde;'>+<span id="LC1736" class="line" lang="haskell"></span>
</pre></td>
</tr>
<tr class="line_holder new" style="line-height: 1.6;">
<td class="old_line diff-line-num new" data-linenumber="1718" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
 
</td>
<td class="new_line diff-line-num new" data-linenumber="1737" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1737
</td>
<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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 #dcdcde;'>+<span id="LC1737" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">where alpha, beta, gamma are the unification variables that instantiate a,b,c,</span></span>
</pre></td>
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<td class="old_line diff-line-num new" data-linenumber="1718" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
 
</td>
<td class="new_line diff-line-num new" data-linenumber="1738" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1738
</td>
<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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 #dcdcde;'>+<span id="LC1738" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">respectively.  We must not drop down to unification, or we will reject the call.</span></span>
</pre></td>
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<td class="old_line diff-line-num new" data-linenumber="1718" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
 
</td>
<td class="new_line diff-line-num new" data-linenumber="1739" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1739
</td>
<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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 #dcdcde;'>+<span id="LC1739" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">Rather we must deeply instantiate the LHS to get</span></span>
</pre></td>
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<td class="old_line diff-line-num new" data-linenumber="1718" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
 
</td>
<td class="new_line diff-line-num new" data-linenumber="1740" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1740
</td>
<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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 #dcdcde;'>+<span id="LC1740" class="line" lang="haskell"></span>
</pre></td>
</tr>
<tr class="line_holder new" style="line-height: 1.6;">
<td class="old_line diff-line-num new" data-linenumber="1718" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
 
</td>
<td class="new_line diff-line-num new" data-linenumber="1741" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1741
</td>
<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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 #dcdcde;'>+<span id="LC1741" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">  (Bool -> delta -> delta)   <=   (alpha beta gamma)</span></span>
</pre></td>
</tr>
<tr class="line_holder new" style="line-height: 1.6;">
<td class="old_line diff-line-num new" data-linenumber="1718" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
 
</td>
<td class="new_line diff-line-num new" data-linenumber="1742" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1742
</td>
<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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 #dcdcde;'>+<span id="LC1742" class="line" lang="haskell"></span>
</pre></td>
</tr>
<tr class="line_holder new" style="line-height: 1.6;">
<td class="old_line diff-line-num new" data-linenumber="1718" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
 
</td>
<td class="new_line diff-line-num new" data-linenumber="1743" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1743
</td>
<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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 #dcdcde;'>+<span id="LC1743" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">and now we can unify to get</span></span>
</pre></td>
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<td class="old_line diff-line-num new" data-linenumber="1718" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
 
</td>
<td class="new_line diff-line-num new" data-linenumber="1744" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1744
</td>
<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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 #dcdcde;'>+<span id="LC1744" class="line" lang="haskell"></span>
</pre></td>
</tr>
<tr class="line_holder new" style="line-height: 1.6;">
<td class="old_line diff-line-num new" data-linenumber="1718" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
 
</td>
<td class="new_line diff-line-num new" data-linenumber="1745" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1745
</td>
<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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 #dcdcde;'>+<span id="LC1745" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">   alpha = (->)</span></span>
</pre></td>
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<td class="old_line diff-line-num new" data-linenumber="1718" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
 
</td>
<td class="new_line diff-line-num new" data-linenumber="1746" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1746
</td>
<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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 #dcdcde;'>+<span id="LC1746" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">   beta = Bool</span></span>
</pre></td>
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<td class="new_line diff-line-num new" data-linenumber="1747" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1747
</td>
<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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 #dcdcde;'>+<span id="LC1747" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">   gamma = delta -> delta</span></span>
</pre></td>
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<td class="old_line diff-line-num new" data-linenumber="1718" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
 
</td>
<td class="new_line diff-line-num new" data-linenumber="1748" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1748
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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 #dcdcde;'>+<span id="LC1748" class="line" lang="haskell"></span>
</pre></td>
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<td class="old_line diff-line-num new" data-linenumber="1718" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
 
</td>
<td class="new_line diff-line-num new" data-linenumber="1749" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1749
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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 #dcdcde;'>+<span id="LC1749" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">Hence the call to `deeplyInstantiate` in `tc_sub_type_deep`.</span></span>
</pre></td>
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</td>
<td class="new_line diff-line-num new" data-linenumber="1750" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1750
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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 #dcdcde;'>+<span id="LC1750" class="line" lang="haskell"></span>
</pre></td>
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<td class="old_line diff-line-num new" data-linenumber="1718" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
 
</td>
<td class="new_line diff-line-num new" data-linenumber="1751" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1751
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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 #dcdcde;'>+<span id="LC1751" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">See typecheck/should_compile/T11305 for an example of when this is important.</span></span>
</pre></td>
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<td class="old_line diff-line-num new" data-linenumber="1718" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
 
</td>
<td class="new_line diff-line-num new" data-linenumber="1752" style="width: 35px; color: rgba(31,30,36,0.24); 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: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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 #dcdcde;'>+<span id="LC1752" class="line" lang="haskell"></span>
</pre></td>
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<td class="old_line diff-line-num new" data-linenumber="1718" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
 
</td>
<td class="new_line diff-line-num new" data-linenumber="1753" style="width: 35px; color: rgba(31,30,36,0.24); 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: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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 #dcdcde;'>+<span id="LC1753" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">Note [Deep subsumption and required foralls]</span></span>
</pre></td>
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</td>
<td class="new_line diff-line-num new" data-linenumber="1754" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1754
</td>
<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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 #dcdcde;'>+<span id="LC1754" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~</span></span>
</pre></td>
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<td class="old_line diff-line-num new" data-linenumber="1718" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
 
</td>
<td class="new_line diff-line-num new" data-linenumber="1755" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1755
</td>
<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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 #dcdcde;'>+<span id="LC1755" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">A required forall, (forall a -> ty) behaves like a "rho-type", one with no</span></span>
</pre></td>
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<td class="old_line diff-line-num new" data-linenumber="1718" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
 
</td>
<td class="new_line diff-line-num new" data-linenumber="1756" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1756
</td>
<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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 #dcdcde;'>+<span id="LC1756" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">top-level quantification.  In particular, it is neither implicitly instantiated nor</span></span>
</pre></td>
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<td class="old_line diff-line-num new" data-linenumber="1718" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
 
</td>
<td class="new_line diff-line-num new" data-linenumber="1757" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1757
</td>
<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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 #dcdcde;'>+<span id="LC1757" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">skolemised.  So</span></span>
</pre></td>
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<td class="old_line diff-line-num new" data-linenumber="1718" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
 
</td>
<td class="new_line diff-line-num new" data-linenumber="1758" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1758
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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 #dcdcde;'>+<span id="LC1758" class="line" lang="haskell"></span>
</pre></td>
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<td class="old_line diff-line-num new" data-linenumber="1718" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
 
</td>
<td class="new_line diff-line-num new" data-linenumber="1759" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1759
</td>
<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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 #dcdcde;'>+<span id="LC1759" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">  rid1 :: forall a -> a -> a</span></span>
</pre></td>
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<td class="old_line diff-line-num new" data-linenumber="1718" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
 
</td>
<td class="new_line diff-line-num new" data-linenumber="1760" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1760
</td>
<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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 #dcdcde;'>+<span id="LC1760" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">  rid1 = id</span></span>
</pre></td>
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<td class="old_line diff-line-num new" data-linenumber="1718" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
 
</td>
<td class="new_line diff-line-num new" data-linenumber="1761" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1761
</td>
<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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 #dcdcde;'>+<span id="LC1761" class="line" lang="haskell"></span>
</pre></td>
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<td class="old_line diff-line-num new" data-linenumber="1718" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
 
</td>
<td class="new_line diff-line-num new" data-linenumber="1762" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1762
</td>
<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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 #dcdcde;'>+<span id="LC1762" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">  rid2 :: forall a -> a -> a</span></span>
</pre></td>
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<td class="old_line diff-line-num new" data-linenumber="1718" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
 
</td>
<td class="new_line diff-line-num new" data-linenumber="1763" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1763
</td>
<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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 #dcdcde;'>+<span id="LC1763" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">  rid2 a = id</span></span>
</pre></td>
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<td class="old_line diff-line-num new" data-linenumber="1718" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
 
</td>
<td class="new_line diff-line-num new" data-linenumber="1764" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1764
</td>
<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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 #dcdcde;'>+<span id="LC1764" class="line" lang="haskell"></span>
</pre></td>
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<tr class="line_holder new" style="line-height: 1.6;">
<td class="old_line diff-line-num new" data-linenumber="1718" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
 
</td>
<td class="new_line diff-line-num new" data-linenumber="1765" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1765
</td>
<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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 #dcdcde;'>+<span id="LC1765" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">Here `rid2` wll typecheck, but `rid1` will not, because we don't implicitly skolemise</span></span>
</pre></td>
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<td class="old_line diff-line-num new" data-linenumber="1718" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
 
</td>
<td class="new_line diff-line-num new" data-linenumber="1766" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1766
</td>
<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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 #dcdcde;'>+<span id="LC1766" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">the  type.</span></span>
</pre></td>
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<td class="old_line diff-line-num new" data-linenumber="1718" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
 
</td>
<td class="new_line diff-line-num new" data-linenumber="1767" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1767
</td>
<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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 #dcdcde;'>+<span id="LC1767" class="line" lang="haskell"></span>
</pre></td>
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<td class="old_line diff-line-num new" data-linenumber="1718" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
 
</td>
<td class="new_line diff-line-num new" data-linenumber="1768" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1768
</td>
<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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 #dcdcde;'>+<span id="LC1768" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">This "no implicit subsumption nor skolemisation" applies during subsumption.</span></span>
</pre></td>
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<td class="old_line diff-line-num new" data-linenumber="1718" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
 
</td>
<td class="new_line diff-line-num new" data-linenumber="1769" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1769
</td>
<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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 #dcdcde;'>+<span id="LC1769" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">For example</span></span>
</pre></td>
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<td class="old_line diff-line-num new" data-linenumber="1718" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
 
</td>
<td class="new_line diff-line-num new" data-linenumber="1770" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1770
</td>
<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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 #dcdcde;'>+<span id="LC1770" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">   (forall a. a->a)  <=  (forall a -> a -> a)  -- NOT!</span></span>
</pre></td>
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<td class="old_line diff-line-num new" data-linenumber="1718" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
 
</td>
<td class="new_line diff-line-num new" data-linenumber="1771" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1771
</td>
<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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 #dcdcde;'>+<span id="LC1771" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">does /not/ hold, because that would require implicitly skoleming the (forall a->).</span></span>
</pre></td>
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<td class="old_line diff-line-num new" data-linenumber="1718" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
 
</td>
<td class="new_line diff-line-num new" data-linenumber="1772" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1772
</td>
<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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 #dcdcde;'>+<span id="LC1772" class="line" lang="haskell"></span>
</pre></td>
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<td class="old_line diff-line-num new" data-linenumber="1718" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
 
</td>
<td class="new_line diff-line-num new" data-linenumber="1773" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1773
</td>
<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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 #dcdcde;'>+<span id="LC1773" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">Note also that, in Core, `eqType` distinguishes between</span></span>
</pre></td>
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<td class="old_line diff-line-num new" data-linenumber="1718" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
 
</td>
<td class="new_line diff-line-num new" data-linenumber="1774" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1774
</td>
<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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 #dcdcde;'>+<span id="LC1774" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">   (forall a. blah) and forall a -> blah)</span></span>
</pre></td>
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<td class="old_line diff-line-num new" data-linenumber="1718" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
 
</td>
<td class="new_line diff-line-num new" data-linenumber="1775" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1775
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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 #dcdcde;'>+<span id="LC1775" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">See discussion on #22762 and these Notes in GHC.Core.TyCo.Compare</span></span>
</pre></td>
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</td>
<td class="new_line diff-line-num new" data-linenumber="1776" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1776
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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 #dcdcde;'>+<span id="LC1776" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">  * Note [ForAllTy and type equality]</span></span>
</pre></td>
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<td class="old_line diff-line-num new" data-linenumber="1718" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
 
</td>
<td class="new_line diff-line-num new" data-linenumber="1777" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1777
</td>
<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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 #dcdcde;'>+<span id="LC1777" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">  * Note [Comparing visibility]</span></span>
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<td class="old_line diff-line-num new" data-linenumber="1718" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
 
</td>
<td class="new_line diff-line-num new" data-linenumber="1778" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1778
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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 #dcdcde;'>+<span id="LC1778" class="line" lang="haskell"></span>
</pre></td>
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<td class="old_line diff-line-num new" data-linenumber="1718" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
 
</td>
<td class="new_line diff-line-num new" data-linenumber="1779" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1779
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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 #dcdcde;'>+<span id="LC1779" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">So during deep subsumption we simply stop (and drop down to equality) when we encounter</span></span>
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<td class="old_line diff-line-num new" data-linenumber="1718" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
 
</td>
<td class="new_line diff-line-num new" data-linenumber="1780" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1780
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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 #dcdcde;'>+<span id="LC1780" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">a (forall a->).  This is a little odd:</span></span>
</pre></td>
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<td class="old_line diff-line-num new" data-linenumber="1718" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
 
</td>
<td class="new_line diff-line-num new" data-linenumber="1781" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1781
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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 #dcdcde;'>+<span id="LC1781" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">* Deep subsumption looks inside invisible foralls (forall a. ty)</span></span>
</pre></td>
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<td class="old_line diff-line-num new" data-linenumber="1718" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
 
</td>
<td class="new_line diff-line-num new" data-linenumber="1782" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1782
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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 #dcdcde;'>+<span id="LC1782" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">* Deep subsumption looks inside arrows (t1 -> t2)</span></span>
</pre></td>
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<td class="old_line diff-line-num new" data-linenumber="1718" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
 
</td>
<td class="new_line diff-line-num new" data-linenumber="1783" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1783
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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 #dcdcde;'>+<span id="LC1783" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">* But it does not look inside required foralls (forall a -> ty)</span></span>
</pre></td>
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<td class="old_line diff-line-num new" data-linenumber="1718" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
 
</td>
<td class="new_line diff-line-num new" data-linenumber="1784" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1784
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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 #dcdcde;'>+<span id="LC1784" class="line" lang="haskell"></span>
</pre></td>
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<td class="old_line diff-line-num new" data-linenumber="1718" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
 
</td>
<td class="new_line diff-line-num new" data-linenumber="1785" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1785
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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 #dcdcde;'>+<span id="LC1785" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">There is discussion on #24696.  How is this implemented?</span></span>
</pre></td>
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<td class="old_line diff-line-num new" data-linenumber="1718" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
 
</td>
<td class="new_line diff-line-num new" data-linenumber="1786" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1786
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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 #dcdcde;'>+<span id="LC1786" class="line" lang="haskell"></span>
</pre></td>
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<td class="old_line diff-line-num new" data-linenumber="1718" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
 
</td>
<td class="new_line diff-line-num new" data-linenumber="1787" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1787
</td>
<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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 #dcdcde;'>+<span id="LC1787" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">* In `tc_sub_type_deep`, the calls to `topInstantiate` and `deeplyInstantiate`</span></span>
</pre></td>
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<td class="old_line diff-line-num new" data-linenumber="1718" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
 
</td>
<td class="new_line diff-line-num new" data-linenumber="1788" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1788
</td>
<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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 #dcdcde;'>+<span id="LC1788" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">  instantiate only /invisible/ binders.</span></span>
</pre></td>
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<td class="old_line diff-line-num new" data-linenumber="1718" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
 
</td>
<td class="new_line diff-line-num new" data-linenumber="1789" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1789
</td>
<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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 #dcdcde;'>+<span id="LC1789" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">* In `tc_sub_type_ds`, the call to `tcSkolemise` skolemises only /invisible/</span></span>
</pre></td>
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<td class="old_line diff-line-num new" data-linenumber="1718" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
 
</td>
<td class="new_line diff-line-num new" data-linenumber="1790" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1790
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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 #dcdcde;'>+<span id="LC1790" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">  binders.</span></span>
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1718
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1791
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<td class="line_content" style="padding: inherit;"><pre style='display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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 #dcdcde;'> <span id="LC1791" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">-}</span></span>
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1719
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1792
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<td class="line_content" style="padding: inherit;"><pre style='display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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 #dcdcde;'> <span id="LC1792" class="line" lang="haskell"></span>
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1720
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<td class="new_line diff-line-num" data-linenumber="1793" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #ececef; border-right-style: solid; padding: inherit;" align="right" bgcolor="#fbfafd">
1793
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<td class="line_content" style="padding: inherit;"><pre style='display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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 #dcdcde;'> <span id="LC1793" class="line" lang="haskell"><span class="kr" style="font-weight: 600;">data</span> <span class="kt" style="color: #458; font-weight: 600;">DeepSubsumptionFlag</span> <span class="o" style="font-weight: 600;">=</span> <span class="kt" style="color: #458; font-weight: 600;">Deep</span> <span class="o" style="font-weight: 600;">|</span> <span class="kt" style="color: #458; font-weight: 600;">Shallow</span></span>
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<td class="diff-line-num unfold js-unfold old_line" data-linenumber="1786" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #ececef; border-right-style: solid; padding: inherit;" align="right" bgcolor="#fbfafd">...</td>
<td class="diff-line-num unfold js-unfold new_line" data-linenumber="1859" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #ececef; border-right-style: solid; padding: inherit;" align="right" bgcolor="#fbfafd">...</td>
<td class="line_content match" style="color: rgba(31,30,36,0.24); padding: inherit;" bgcolor="#fbfafd">@@ -1786,10 +1859,7 @@ tc_sub_type_deep unify inst_orig ctxt ty_actual ty_expected</td>
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1786
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<td class="new_line diff-line-num" data-linenumber="1859" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #ececef; border-right-style: solid; padding: inherit;" align="right" bgcolor="#fbfafd">
1859
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<td class="line_content" style="padding: inherit;"><pre style='display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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 #dcdcde;'> <span id="LC1859" class="line" lang="haskell">      <span class="o" style="font-weight: 600;">|</span> <span class="n" style="color: #333;">otherwise</span>   <span class="c1" style="color: #998; font-style: italic;">-- Revert to unification</span></span>
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1787
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<td class="new_line diff-line-num" data-linenumber="1860" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #ececef; border-right-style: solid; padding: inherit;" align="right" bgcolor="#fbfafd">
1860
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<td class="line_content" style="padding: inherit;"><pre style='display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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 #dcdcde;'> <span id="LC1860" class="line" lang="haskell">      <span class="o" style="font-weight: 600;">=</span> <span class="kr" style="font-weight: 600;">do</span> <span class="p">{</span> <span class="c1" style="color: #998; font-style: italic;">-- It's still possible that ty_actual has nested foralls. Instantiate</span></span>
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<td class="old_line diff-line-num" data-linenumber="1788" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #ececef; border-right-style: solid; padding: inherit;" align="right" bgcolor="#fbfafd">
1788
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<td class="new_line diff-line-num" data-linenumber="1861" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #ececef; border-right-style: solid; padding: inherit;" align="right" bgcolor="#fbfafd">
1861
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<td class="line_content" style="padding: inherit;"><pre style='display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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 #dcdcde;'> <span id="LC1861" class="line" lang="haskell">             <span class="c1" style="color: #998; font-style: italic;">-- these, as there's no way unification will succeed with them in.</span></span>
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<td class="old_line diff-line-num old" data-linenumber="1789" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #fac5cd; border-right-style: solid; padding: inherit;" align="right" bgcolor="#f9d7dc">
1789
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<td class="new_line diff-line-num old" data-linenumber="1862" style="width: 35px; color: rgba(31,30,36,0.24); 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: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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 #dcdcde;'>-<span id="LC1789" class="line" lang="haskell">             <span class="c1" style="color: #998; font-style: italic;">-- See typecheck/should_compile/T11305 for an example of when this</span></span>
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<td class="old_line diff-line-num old" data-linenumber="1790" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #fac5cd; border-right-style: solid; padding: inherit;" align="right" bgcolor="#f9d7dc">
1790
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<td class="new_line diff-line-num old" data-linenumber="1862" style="width: 35px; color: rgba(31,30,36,0.24); 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: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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 #dcdcde;'>-<span id="LC1790" class="line" lang="haskell">             <span class="c1" style="color: #998; font-style: italic;">-- is important. The problem is that we're checking something like</span></span>
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<td class="old_line diff-line-num old" data-linenumber="1791" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #fac5cd; border-right-style: solid; padding: inherit;" align="right" bgcolor="#f9d7dc">
1791
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<td class="new_line diff-line-num old" data-linenumber="1862" style="width: 35px; color: rgba(31,30,36,0.24); 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: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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 #dcdcde;'>-<span id="LC1791" class="line" lang="haskell">             <span class="c1" style="color: #998; font-style: italic;">--  a -> forall b. b -> b     <=   alpha beta gamma</span></span>
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<td class="old_line diff-line-num old" data-linenumber="1792" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #fac5cd; border-right-style: solid; padding: inherit;" align="right" bgcolor="#f9d7dc">
1792
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<td class="new_line diff-line-num old" data-linenumber="1862" style="width: 35px; color: rgba(31,30,36,0.24); 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: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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 #dcdcde;'>-<span id="LC1792" class="line" lang="haskell">             <span class="c1" style="color: #998; font-style: italic;">-- where we end up with alpha := (->)</span></span>
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<td class="old_line diff-line-num new" data-linenumber="1793" style="width: 35px; color: rgba(31,30,36,0.24); 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="1862" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1862
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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 #dcdcde;'>+<span id="LC1862" class="line" lang="haskell">             <span class="c1" style="color: #998; font-style: italic;">-- See Note [The need for deep instantiation]</span></span>
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1793
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<td class="new_line diff-line-num" data-linenumber="1863" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #ececef; border-right-style: solid; padding: inherit;" align="right" bgcolor="#fbfafd">
1863
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<td class="line_content" style="padding: inherit;"><pre style='display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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 #dcdcde;'> <span id="LC1863" class="line" lang="haskell">             <span class="p">(</span><span class="n" style="color: #333;">inst_wrap</span><span class="p">,</span> <span class="n" style="color: #333;">rho_a</span><span class="p">)</span> <span class="o" style="font-weight: 600;"><-</span> <span class="n" style="color: #333;">deeplyInstantiate</span> <span class="n" style="color: #333;">inst_orig</span> <span class="n" style="color: #333;">ty_actual</span></span>
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1794
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<td class="new_line diff-line-num" data-linenumber="1864" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #ececef; border-right-style: solid; padding: inherit;" align="right" bgcolor="#fbfafd">
1864
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<td class="line_content" style="padding: inherit;"><pre style='display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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 #dcdcde;'> <span id="LC1864" class="line" lang="haskell">           <span class="p">;</span> <span class="n" style="color: #333;">unify_wrap</span>         <span class="o" style="font-weight: 600;"><-</span> <span class="n" style="color: #333;">just_unify</span> <span class="n" style="color: #333;">rho_a</span> <span class="n" style="color: #333;">ty_expected</span></span>
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1795
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1865
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<td class="line_content" style="padding: inherit;"><pre style='display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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 #dcdcde;'> <span id="LC1865" class="line" lang="haskell">           <span class="p">;</span> <span class="n" style="color: #333;">return</span> <span class="p">(</span><span class="n" style="color: #333;">unify_wrap</span> <span class="o" style="font-weight: 600;"><.></span> <span class="n" style="color: #333;">inst_wrap</span><span class="p">)</span> <span class="p">}</span></span>
</pre></td>
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