[PATCH] Fix for PR18393 - emit error when abstract type is returned by value

[Richard Smith]

We need to defer this check in the case where the type in question is still being defined.

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Comment at: lib/Sema/SemaDecl.cpp:6497-6498
@@ -6496,3 +6496,4 @@
   // Check that the return type is not an abstract class type.
   // For record types, this is done by the AbstractClassUsageDiagnoser once
   // the class has been completely parsed.
+  if (SemaRef.RequireNonAbstractType(
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This comment describes how this case is intended to be handled; we need more digging to figure out what's actually wrong here.

http://reviews.llvm.org/D4769