<div dir="ltr">Seems like a reasonable candidate for branch: just turning an assertion failure into proper handling of the relevant case.</div><div class="gmail_extra"><br><div class="gmail_quote">On Tue, Feb 10, 2015 at 5:48 PM, Richard Smith <span dir="ltr"><<a href="mailto:richard-llvm@metafoo.co.uk" target="_blank">richard-llvm@metafoo.co.uk</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Author: rsmith<br>
Date: Tue Feb 10 19:48:47 2015<br>
New Revision: 228785<br>
<br>
URL: <a href="http://llvm.org/viewvc/llvm-project?rev=228785&view=rev" target="_blank">http://llvm.org/viewvc/llvm-project?rev=228785&view=rev</a><br>
Log:<br>
PR21857: weaken an incorrect assertion.<br>
<br>
Modified:<br>
    cfe/trunk/lib/Sema/SemaLookup.cpp<br>
    cfe/trunk/test/SemaCXX/lambda-expressions.cpp<br>
<br>
Modified: cfe/trunk/lib/Sema/SemaLookup.cpp<br>
URL: <a href="http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaLookup.cpp?rev=228785&r1=228784&r2=228785&view=diff" target="_blank">http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaLookup.cpp?rev=228785&r1=228784&r2=228785&view=diff</a><br>
==============================================================================<br>
--- cfe/trunk/lib/Sema/SemaLookup.cpp (original)<br>
+++ cfe/trunk/lib/Sema/SemaLookup.cpp Tue Feb 10 19:48:47 2015<br>
@@ -2503,8 +2503,18 @@ Sema::SpecialMemberOverloadResult *Sema:<br>
   // will always be a (possibly implicit) declaration to shadow any others.<br>
   OverloadCandidateSet OCS(RD->getLocation(), OverloadCandidateSet::CSK_Normal);<br>
   DeclContext::lookup_result R = RD->lookup(Name);<br>
-  assert(!R.empty() &&<br>
-         "lookup for a constructor or assignment operator was empty");<br>
+<br>
+  if (R.empty()) {<br>
+    // We might have no default constructor because we have a lambda's closure<br>
+    // type, rather than because there's some other declared constructor.<br>
+    // Every class has a copy/move constructor, copy/move assignment, and<br>
+    // destructor.<br>
+    assert(SM == CXXDefaultConstructor &&<br>
+           "lookup for a constructor or assignment operator was empty");<br>
+    Result->setMethod(nullptr);<br>
+    Result->setKind(SpecialMemberOverloadResult::NoMemberOrDeleted);<br>
+    return Result;<br>
+  }<br>
<br>
   // Copy the candidates as our processing of them may load new declarations<br>
   // from an external source and invalidate lookup_result.<br>
<br>
Modified: cfe/trunk/test/SemaCXX/lambda-expressions.cpp<br>
URL: <a href="http://llvm.org/viewvc/llvm-project/cfe/trunk/test/SemaCXX/lambda-expressions.cpp?rev=228785&r1=228784&r2=228785&view=diff" target="_blank">http://llvm.org/viewvc/llvm-project/cfe/trunk/test/SemaCXX/lambda-expressions.cpp?rev=228785&r1=228784&r2=228785&view=diff</a><br>
==============================================================================<br>
--- cfe/trunk/test/SemaCXX/lambda-expressions.cpp (original)<br>
+++ cfe/trunk/test/SemaCXX/lambda-expressions.cpp Tue Feb 10 19:48:47 2015<br>
@@ -437,3 +437,12 @@ namespace error_in_transform_prototype {<br>
     f(S()); // expected-note {{requested here}}<br>
   }<br>
 }<br>
+<br>
+namespace PR21857 {<br>
+  template<typename Fn> struct fun : Fn {<br>
+    fun() = default;<br>
+    using Fn::operator();<br>
+  };<br>
+  template<typename Fn> fun<Fn> wrap(Fn fn);<br>
+  auto x = wrap([](){});<br>
+}<br>
<br>
<br>
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</blockquote></div><br></div>