[Sema] Fix decltype of static data members

Summary:
According to the C++11 standard [dcl.type.simple]p4:
  The type denoted by decltype(e) is defined as follows:
  - if e is an unparenthesized id-expression or an unparenthesized
    class member access (5.2.5), decltype(e) is the type of the entity
    named by e.
    
Currently Clang handles the 'member access' case incorrectly for
static data members (decltype returns T& instead of T). This patch
fixes the issue.

Reviewers: faisalv, rsmith, rogfer01

Reviewed By: rogfer01

Subscribers: rogfer01, cfe-commits

Differential Revision: https://reviews.llvm.org/D42969

llvm-svn: 325117

clang/lib/Sema/SemaType.cpp

@@ -7868,8 +7868,9 @@ static QualType getDecltypeForExpr(Sema &S, Expr *E) {
     if (const ValueDecl *VD = dyn_cast<ValueDecl>(DRE->getDecl()))
       return VD->getType();
   } else if (const MemberExpr *ME = dyn_cast<MemberExpr>(E)) {
-    if (const FieldDecl *FD = dyn_cast<FieldDecl>(ME->getMemberDecl()))
-      return FD->getType();
+    if (const ValueDecl *VD = ME->getMemberDecl())
+      if (isa<FieldDecl>(VD) || isa<VarDecl>(VD))
+        return VD->getType();
   } else if (const ObjCIvarRefExpr *IR = dyn_cast<ObjCIvarRefExpr>(E)) {
     return IR->getDecl()->getType();
   } else if (const ObjCPropertyRefExpr *PR = dyn_cast<ObjCPropertyRefExpr>(E)) {

clang/test/CXX/dcl.dcl/dcl.spec/dcl.type/dcl.type.simple/p4-cxx0x.cpp

@@ -12,13 +12,18 @@ struct is_same<T, T> {
 
 const int&& foo();
 int i;
-struct A { double x; };
+struct A {
+  double x;
+  static int y;
+};
 const A* a = new A();
 
 static_assert(is_same<decltype(foo()), const int&&>::value, "");
 static_assert(is_same<decltype(i), int>::value, "");
 static_assert(is_same<decltype(a->x), double>::value, "");
 static_assert(is_same<decltype((a->x)), const double&>::value, "");
+static_assert(is_same<decltype(a->y), int>::value, "");
+static_assert(is_same<decltype((a->y)), int&>::value, "");
 static_assert(is_same<decltype(static_cast<int&&>(i)), int&&>::value, "");
 
 int f0(int); // expected-note{{possible target}}