Implement the lvalue-to-rvalue conversion where needed. The

lvalue-to-rvalue conversion adjusts lvalues of qualified, non-class
type to rvalue expressions of the unqualified variant of that
type. For example, given:

  const int i;
  (void)(i + 17);

the lvalue-to-rvalue conversion for the subexpression "i" will turn it
from an lvalue expression (a DeclRefExpr) with type 'const int' into
an rvalue expression with type 'int'. Both C and C++ mandate this
conversion, and somehow we've slid through without implementing it. 

We now have both DefaultFunctionArrayConversion and
DefaultFunctionArrayLvalueConversion, and which gets used depends on
whether we do the lvalue-to-rvalue conversion or not. Generally, we do
the lvalue-to-rvalue conversion, but there are a few notable
exceptions:
  - the left-hand side of a '.' operator
  - the left-hand side of an assignment
  - a C++ throw expression
  - a subscript expression that's subscripting a vector

Making this change exposed two issues with blocks:
  - we were deducing const-qualified return types of non-class type
  from a block return, which doesn't fit well
  - we weren't always setting the known return type of a block when it
  was provided with the ^return-type syntax

Fixes the current Clang-on-Clang compile failure and PR6076.

llvm-svn: 95167

clang/lib/Sema/SemaCodeComplete.cpp

@@ -2978,7 +2978,7 @@ void Sema::CodeCompleteObjCInstanceMessage(Scope *S, ExprTy *Receiver,
   
   // If necessary, apply function/array conversion to the receiver.
   // C99 6.7.5.3p[7,8].
-  DefaultFunctionArrayConversion(RecExpr);
+  DefaultFunctionArrayLvalueConversion(RecExpr);
   QualType ReceiverType = RecExpr->getType();
   
   if (ReceiverType->isObjCIdType() || ReceiverType->isBlockPointerType()) {