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Simon Peyton Jones pushed to branch wip/T25325 at <a href="https://gitlab.haskell.org/ghc/ghc">Glasgow Haskell Compiler / GHC</a>
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<strong style="font-weight: 600;"><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/c15a7e65259749663728e44d35ecbabd26b687f9">c15a7e65</a></strong>
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<span> by Simon Peyton Jones </span> <i> at 2024-10-07T15:56:12+01:00 </i>
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2 changed files:
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compiler/GHC/Tc/Errors.hs
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compiler/GHC/Tc/Types/Constraint.hs
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Changes:
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<a href="https://gitlab.haskell.org/ghc/ghc/-/commit/c15a7e65259749663728e44d35ecbabd26b687f9#e4b9d5e9d2de37561bfd06a2c97a5c924a1bab76"><strong style="font-weight: 600;">compiler/GHC/Tc/Errors.hs</strong></a>
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<td class="diff-line-num unfold js-unfold new_line" data-linenumber="470" style="width: 35px; color: rgba(5,5,6,.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(5,5,6,.24); padding: inherit;" bgcolor="#fbfafd">@@ -470,6 +470,8 @@ mkErrorItem ct</td>
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<td class="old_line diff-line-num" data-linenumber="470" style="width: 35px; color: rgba(5,5,6,.24); border-right-width: 1px; border-right-color: #ececef; border-right-style: solid; padding: inherit;" align="right" bgcolor="#fbfafd">
470
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<td class="new_line diff-line-num" data-linenumber="470" style="width: 35px; color: rgba(5,5,6,.24); border-right-width: 1px; border-right-color: #ececef; border-right-style: solid; padding: inherit;" align="right" bgcolor="#fbfafd">
470
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<td class="line_content" style="padding: inherit;"><pre style='display: block; font-size: 14px; color: #28272d; position: relative; font-family: "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="LC470" class="line" lang="haskell"> <span class="n" style="color: #333;">flav</span> <span class="o" style="font-weight: 600;">=</span> <span class="n" style="color: #333;">ctFlavour</span> <span class="n" style="color: #333;">ct</span></span>
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471
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<td class="new_line diff-line-num" data-linenumber="471" style="width: 35px; color: rgba(5,5,6,.24); border-right-width: 1px; border-right-color: #ececef; border-right-style: solid; padding: inherit;" align="right" bgcolor="#fbfafd">
471
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<td class="line_content" style="padding: inherit;"><pre style='display: block; font-size: 14px; color: #28272d; position: relative; font-family: "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="LC471" class="line" lang="haskell"></span>
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472
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<td class="new_line diff-line-num" data-linenumber="472" style="width: 35px; color: rgba(5,5,6,.24); border-right-width: 1px; border-right-color: #ececef; border-right-style: solid; padding: inherit;" align="right" bgcolor="#fbfafd">
472
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<td class="line_content" style="padding: inherit;"><pre style='display: block; font-size: 14px; color: #28272d; position: relative; font-family: "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="LC472" class="line" lang="haskell"> <span class="p">;</span> <span class="p">(</span><span class="n" style="color: #333;">suppress</span><span class="p">,</span> <span class="n" style="color: #333;">m_evdest</span><span class="p">)</span> <span class="o" style="font-weight: 600;"><-</span> <span class="kr" style="font-weight: 600;">case</span> <span class="n" style="color: #333;">ctEvidence</span> <span class="n" style="color: #333;">ct</span> <span class="kr" style="font-weight: 600;">of</span></span>
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<td class="new_line diff-line-num new" data-linenumber="473" style="width: 35px; color: rgba(5,5,6,.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
473
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 14px; color: #28272d; position: relative; font-family: "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="LC473" class="line" lang="haskell"> <span class="c1" style="color: #998; font-style: italic;">-- For this `suppress` stuff</span></span>
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<td class="new_line diff-line-num new" data-linenumber="474" style="width: 35px; color: rgba(5,5,6,.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
474
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 14px; color: #28272d; position: relative; font-family: "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="LC474" class="line" lang="haskell"> <span class="c1" style="color: #998; font-style: italic;">-- see Note [Wanteds rewrite Wanteds] in GHC.Tc.Types.Constraint</span></span>
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473
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<td class="new_line diff-line-num" data-linenumber="475" style="width: 35px; color: rgba(5,5,6,.24); border-right-width: 1px; border-right-color: #ececef; border-right-style: solid; padding: inherit;" align="right" bgcolor="#fbfafd">
475
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<td class="line_content" style="padding: inherit;"><pre style='display: block; font-size: 14px; color: #28272d; position: relative; font-family: "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="LC475" class="line" lang="haskell"> <span class="kt" style="color: #458; font-weight: 600;">CtGiven</span> <span class="p">{}</span> <span class="o" style="font-weight: 600;">-></span> <span class="n" style="color: #333;">return</span> <span class="p">(</span><span class="kt" style="color: #458; font-weight: 600;">False</span><span class="p">,</span> <span class="kt" style="color: #458; font-weight: 600;">Nothing</span><span class="p">)</span></span>
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474
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<td class="new_line diff-line-num" data-linenumber="476" style="width: 35px; color: rgba(5,5,6,.24); border-right-width: 1px; border-right-color: #ececef; border-right-style: solid; padding: inherit;" align="right" bgcolor="#fbfafd">
476
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<td class="line_content" style="padding: inherit;"><pre style='display: block; font-size: 14px; color: #28272d; position: relative; font-family: "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="LC476" class="line" lang="haskell"> <span class="kt" style="color: #458; font-weight: 600;">CtWanted</span> <span class="p">{</span> <span class="n" style="color: #333;">ctev_rewriters</span> <span class="o" style="font-weight: 600;">=</span> <span class="n" style="color: #333;">rewriters</span><span class="p">,</span> <span class="n" style="color: #333;">ctev_dest</span> <span class="o" style="font-weight: 600;">=</span> <span class="n" style="color: #333;">dest</span> <span class="p">}</span></span>
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475
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<td class="new_line diff-line-num" data-linenumber="477" style="width: 35px; color: rgba(5,5,6,.24); border-right-width: 1px; border-right-color: #ececef; border-right-style: solid; padding: inherit;" align="right" bgcolor="#fbfafd">
477
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<td class="line_content" style="padding: inherit;"><pre style='display: block; font-size: 14px; color: #28272d; position: relative; font-family: "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="LC477" 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="n" style="color: #333;">rewriters'</span> <span class="o" style="font-weight: 600;"><-</span> <span class="n" style="color: #333;">zonkRewriterSet</span> <span class="n" style="color: #333;">rewriters</span></span>
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<a href="https://gitlab.haskell.org/ghc/ghc/-/commit/c15a7e65259749663728e44d35ecbabd26b687f9#3b6d78a50c8462304f843b952a88e531718dbbd2"><strong style="font-weight: 600;">compiler/GHC/Tc/Types/Constraint.hs</strong></a>
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<td class="diff-line-num unfold js-unfold old_line" data-linenumber="1444" style="width: 35px; color: rgba(5,5,6,.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="1444" style="width: 35px; color: rgba(5,5,6,.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(5,5,6,.24); padding: inherit;" bgcolor="#fbfafd">@@ -1444,13 +1444,13 @@ can't be solved. But not quite all such constraints; see wrinkles.</td>
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<td class="old_line diff-line-num" data-linenumber="1444" style="width: 35px; color: rgba(5,5,6,.24); border-right-width: 1px; border-right-color: #ececef; border-right-style: solid; padding: inherit;" align="right" bgcolor="#fbfafd">
1444
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<td class="new_line diff-line-num" data-linenumber="1444" style="width: 35px; color: rgba(5,5,6,.24); border-right-width: 1px; border-right-color: #ececef; border-right-style: solid; padding: inherit;" align="right" bgcolor="#fbfafd">
1444
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<td class="line_content" style="padding: inherit;"><pre style='display: block; font-size: 14px; color: #28272d; position: relative; font-family: "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="LC1444" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;"> it looks only for IrredCt; all insoluble constraints oare put into</span></span>
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<td class="old_line diff-line-num" data-linenumber="1445" style="width: 35px; color: rgba(5,5,6,.24); border-right-width: 1px; border-right-color: #ececef; border-right-style: solid; padding: inherit;" align="right" bgcolor="#fbfafd">
1445
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1445
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<td class="line_content" style="padding: inherit;"><pre style='display: block; font-size: 14px; color: #28272d; position: relative; font-family: "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="LC1445" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;"> CIrredCan</span></span>
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1446
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1446
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<td class="line_content" style="padding: inherit;"><pre style='display: block; font-size: 14px; color: #28272d; position: relative; font-family: "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="LC1446" class="line" lang="haskell"></span>
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<td class="old_line diff-line-num old" data-linenumber="1447" style="width: 35px; color: rgba(5,5,6,.24); border-right-width: 1px; border-right-color: #fac5cd; border-right-style: solid; padding: inherit;" align="right" bgcolor="#f9d7dc">
1447
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<td class="new_line diff-line-num old" data-linenumber="1447" style="width: 35px; color: rgba(5,5,6,.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: #28272d; position: relative; font-family: "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="LC1447" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">(IW2) We only treat it as insoluble if it has an empty rewriter set.</span></span>
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<td class="old_line diff-line-num old" data-linenumber="1448" style="width: 35px; color: rgba(5,5,6,.24); border-right-width: 1px; border-right-color: #fac5cd; border-right-style: solid; padding: inherit;" align="right" bgcolor="#f9d7dc">
1448
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<td class="new_line diff-line-num old" data-linenumber="1447" style="width: 35px; color: rgba(5,5,6,.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: #28272d; position: relative; font-family: "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="LC1448" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;"> Otherwise #25325 happens: a Wanted constraint A<span class="idiff left right deletion" style="background-color: #fac5cd;"> that is /not/ insoluble</span></span></span>
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1449
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<td class="new_line diff-line-num old" data-linenumber="1447" style="width: 35px; color: rgba(5,5,6,.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: #28272d; position: relative; font-family: "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="LC1449" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;"> rewrites some other Wanted constraint B, so B has A<span class="idiff left right deletion" style="background-color: #fac5cd;"> in its rewriter</span></span></span>
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<td class="old_line diff-line-num old" data-linenumber="1450" style="width: 35px; color: rgba(5,5,6,.24); border-right-width: 1px; border-right-color: #fac5cd; border-right-style: solid; padding: inherit;" align="right" bgcolor="#f9d7dc">
1450
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<td class="new_line diff-line-num old" data-linenumber="1447" style="width: 35px; color: rgba(5,5,6,.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: #28272d; position: relative; font-family: "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="LC1450" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;"> set. Now B looks insoluble. The danger is that we'll<span class="idiff left right deletion" style="background-color: #fac5cd;"> suppress reporting</span></span></span>
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<td class="old_line diff-line-num old" data-linenumber="1451" style="width: 35px; color: rgba(5,5,6,.24); border-right-width: 1px; border-right-color: #fac5cd; border-right-style: solid; padding: inherit;" align="right" bgcolor="#f9d7dc">
1451
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<td class="new_line diff-line-num old" data-linenumber="1447" style="width: 35px; color: rgba(5,5,6,.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: #28272d; position: relative; font-family: "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="LC1451" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;"> B becuase of its empty rewriter set; and suppress<span class="idiff left right deletion" style="background-color: #fac5cd;"> reporting A because</span></span></span>
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<td class="old_line diff-line-num old" data-linenumber="1452" style="width: 35px; color: rgba(5,5,6,.24); border-right-width: 1px; border-right-color: #fac5cd; border-right-style: solid; padding: inherit;" align="right" bgcolor="#f9d7dc">
1452
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<td class="new_line diff-line-num old" data-linenumber="1447" style="width: 35px; color: rgba(5,5,6,.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: #28272d; position: relative; font-family: "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="LC1452" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;"> there is an insoluble B lying around. (This suppression<span class="idiff left right deletion" style="background-color: #fac5cd;"> happens in</span></span></span>
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<td class="old_line diff-line-num old" data-linenumber="1453" style="width: 35px; color: rgba(5,5,6,.24); border-right-width: 1px; border-right-color: #fac5cd; border-right-style: solid; padding: inherit;" align="right" bgcolor="#f9d7dc">
1453
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<td class="new_line diff-line-num old" data-linenumber="1447" style="width: 35px; color: rgba(5,5,6,.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: #28272d; position: relative; font-family: "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="LC1453" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;"> GHC.Tc.Errors.) Solution: don't treat B as insoluble.</span></span>
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<td class="old_line diff-line-num new" data-linenumber="1454" style="width: 35px; color: rgba(5,5,6,.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="1447" style="width: 35px; color: rgba(5,5,6,.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1447
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 14px; color: #28272d; position: relative; font-family: "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="LC1447" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">(IW2) We only treat it as insoluble if it has an empty rewriter set.<span class="idiff left right addition" style="background-color: #c7f0d2;"> (See Note</span></span></span>
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<td class="old_line diff-line-num new" data-linenumber="1454" style="width: 35px; color: rgba(5,5,6,.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="1448" style="width: 35px; color: rgba(5,5,6,.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1448
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 14px; color: #28272d; position: relative; font-family: "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="LC1448" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;"> <span class="idiff left right addition" style="background-color: #c7f0d2;">[Wanteds rewrite Wanteds].) </span>Otherwise #25325 happens: a Wanted constraint A</span></span>
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<td class="old_line diff-line-num new" data-linenumber="1454" style="width: 35px; color: rgba(5,5,6,.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="1449" style="width: 35px; color: rgba(5,5,6,.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1449
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 14px; color: #28272d; position: relative; font-family: "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="LC1449" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;"> <span class="idiff left right addition" style="background-color: #c7f0d2;">that is /not/ insoluble </span>rewrites some other Wanted constraint B, so B has A</span></span>
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<td class="old_line diff-line-num new" data-linenumber="1454" style="width: 35px; color: rgba(5,5,6,.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="1450" style="width: 35px; color: rgba(5,5,6,.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1450
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 14px; color: #28272d; position: relative; font-family: "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="LC1450" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;"> <span class="idiff left right addition" style="background-color: #c7f0d2;">in its rewriter </span>set. Now B looks insoluble. The danger is that we'll</span></span>
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<td class="old_line diff-line-num new" data-linenumber="1454" style="width: 35px; color: rgba(5,5,6,.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="1451" style="width: 35px; color: rgba(5,5,6,.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1451
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 14px; color: #28272d; position: relative; font-family: "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="LC1451" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;"> <span class="idiff left right addition" style="background-color: #c7f0d2;">suppress reporting </span>B becuase of its empty rewriter set; and suppress</span></span>
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<td class="old_line diff-line-num new" data-linenumber="1454" style="width: 35px; color: rgba(5,5,6,.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="1452" style="width: 35px; color: rgba(5,5,6,.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1452
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 14px; color: #28272d; position: relative; font-family: "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="LC1452" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;"> <span class="idiff left right addition" style="background-color: #c7f0d2;">reporting A because </span>there is an insoluble B lying around. (This suppression</span></span>
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<td class="old_line diff-line-num new" data-linenumber="1454" style="width: 35px; color: rgba(5,5,6,.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="1453" style="width: 35px; color: rgba(5,5,6,.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
1453
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='display: block; font-size: 14px; color: #28272d; position: relative; font-family: "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="LC1453" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;"> <span class="idiff left addition" style="background-color: #c7f0d2;">happens in </span>GHC.Tc.Errors.<span class="idiff right addition" style="background-color: #c7f0d2;">mkErrorItem.</span>) Solution: don't treat B as insoluble.</span></span>
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1454
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<td class="new_line diff-line-num" data-linenumber="1454" style="width: 35px; color: rgba(5,5,6,.24); border-right-width: 1px; border-right-color: #ececef; border-right-style: solid; padding: inherit;" align="right" bgcolor="#fbfafd">
1454
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<td class="line_content" style="padding: inherit;"><pre style='display: block; font-size: 14px; color: #28272d; position: relative; font-family: "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="LC1454" class="line" lang="haskell"></span>
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<td class="old_line diff-line-num" data-linenumber="1455" style="width: 35px; color: rgba(5,5,6,.24); border-right-width: 1px; border-right-color: #ececef; border-right-style: solid; padding: inherit;" align="right" bgcolor="#fbfafd">
1455
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<td class="new_line diff-line-num" data-linenumber="1455" style="width: 35px; color: rgba(5,5,6,.24); border-right-width: 1px; border-right-color: #ececef; border-right-style: solid; padding: inherit;" align="right" bgcolor="#fbfafd">
1455
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<td class="line_content" style="padding: inherit;"><pre style='display: block; font-size: 14px; color: #28272d; position: relative; font-family: "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="LC1455" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">(IW3) If the Wanted arises from a Given (how can that happen?), don't</span></span>
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<td class="old_line diff-line-num" data-linenumber="1456" style="width: 35px; color: rgba(5,5,6,.24); border-right-width: 1px; border-right-color: #ececef; border-right-style: solid; padding: inherit;" align="right" bgcolor="#fbfafd">
1456
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<td class="new_line diff-line-num" data-linenumber="1456" style="width: 35px; color: rgba(5,5,6,.24); border-right-width: 1px; border-right-color: #ececef; border-right-style: solid; padding: inherit;" align="right" bgcolor="#fbfafd">
1456
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<td class="line_content" style="padding: inherit;"><pre style='display: block; font-size: 14px; color: #28272d; position: relative; font-family: "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="LC1456" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;"> treat it as a Wanted insoluble (obviously).</span></span>
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