[Sema] Use the value category of the base expression when creating an ExtVectorElementExpr

[ahatanak]

Summary

This fixes a bug where an lvalue ExtVectorElementExpr was created when the base expression was an ObjC property dot operator.

This reverts 220d08d942ab0df3211388e602ed34fa6139ca61.

[rjmccall]

LGTM

clang/lib/Sema/SemaExprMember.cpp

S.Diag(R.getNameLoc(), diag::err_ext_vector_component_name_illegal)
         << (BaseExpr.get() ? BaseExpr.get()->getSourceRange() : SourceRange());
     return ExprError();
   }
 
   // Handle 'field access' to vectors, such as 'V.xx'.
   if (BaseType->isExtVectorType()) {
     // FIXME: this expr should store IsArrow.
     IdentifierInfo *Member = MemberName.getAsIdentifierInfo();
-    ExprValueKind VK;
-    if (IsArrow)
-      VK = VK_LValue;
-    else {
-      if (PseudoObjectExpr *POE = dyn_cast<PseudoObjectExpr>(BaseExpr.get()))
-        VK = POE->getSyntacticForm()->getValueKind();
-      else
-        VK = BaseExpr.get()->getValueKind();
-    }
-
+    ExprValueKind VK = (IsArrow ? VK_LValue : BaseExpr.get()->getValueKind());
     QualType ret = CheckExtVectorComponent(S, BaseType, VK, OpLoc,
                                            Member, MemberLoc);
     if (ret.isNull())
       return ExprError();
     Qualifiers BaseQ =
         S.Context.getCanonicalType(BaseExpr.get()->getType()).getQualifiers();
     ret = S.Context.getQualifiedType(ret, BaseQ);
 

clang/test/SemaObjC/property-not-lvalue.m

 // RUN: %clang_cc1 -fsyntax-only -verify -Wno-objc-root-class %s
 
 typedef struct NSSize {
         int width;
     struct {
       int dim;
     } inner;
 } NSSize;
 
+typedef __attribute__((__ext_vector_type__(2))) float simd_float2;
+
 @interface Foo  {
         NSSize _size;
 }
 @property NSSize size;
+@property simd_float2 f2;
 @end
 
 void foo(void) { 
         Foo *f;
         f.size.width = 2.2; // expected-error {{expression is not assignable}}
   f.size.inner.dim = 200; // expected-error {{expression is not assignable}}
 }
 
 // radar 7628953
 
 @interface Gorf  {
 }
 - (NSSize)size;
 @end
 
 @implementation Gorf
 - (void)MyView_sharedInit {
     self.size.width = 2.2; // expected-error {{expression is not assignable}}
 }
 - (NSSize)size {}
 @end
+
+// clang used to crash compiling this code.
+void test(Foo *f) {
+  simd_float2 *v = &f.f2.xy; // expected-error {{cannot take the address of an rvalue}}
+}