In blocks, only pretend that enum constants have enum type if necessary.

In C, enum constants have the type of the enum's underlying integer type,
rather than the type of the enum. (This is not true in C++.) Thus, when a
block's return type is inferred from an enum constant, it is incompatible
with expressions that return the enum type.

In r158899, I told block returns to pretend that enum constants have enum
type, like in C++. Doug Gregor pointed out that this can break existing code.

Now, we don't check the types of return statements until the end of the block.
This lets us go back and add implicit casts in blocks with mixed enum
constants and enum-typed expressions.

<rdar://problem/11662489> (again)

llvm-svn: 159591

1 files changed, 6 insertions, 1 deletions

diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index d63922ba326..99814911e09 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -7659,7 +7659,12 @@ Decl *Sema::ActOnFinishFunctionBody(Decl *dcl, Stmt *Body,
       if (CXXConstructorDecl *Constructor = dyn_cast<CXXConstructorDecl>(FD))
         MarkVTableUsed(FD->getLocation(), Constructor->getParent());
       
-      computeNRVO(Body, getCurFunction());
+      // Try to apply the named return value optimization. We have to check
+      // if we can do this here because lambdas keep return statements around
+      // to deduce an implicit return type.
+      if (getLangOpts().CPlusPlus && FD->getResultType()->isRecordType() &&
+          !FD->isDependentContext())
+        computeNRVO(Body, getCurFunction());
     }
     
     assert((FD == getCurFunctionDecl() || getCurLambda()->CallOperator == FD) &&