ObjCXX: Warn undeclared identifiers.

[manmanren]

Summary

Instantiation dependence were not being handled correctly for OpqaueValueExpr
AST nodes. As a result, if an undeclared identifier was used in a CXXNewExpr
that is assigned to a ObjC property, there would be no error during parsing, and
there would be a crash during code gen. This patch makes sure that an error
will be issued during parsing in this case.

Before the fix, if CXXNewExpr has a typo, its InstantiationDependent will be
set to true, but if it is wrapped in a OpaqueValueExpr, the OpaqueValueExpr will
not be instantiation dependent, causing the TypoExpr not be to resolved. The fix
propagates InstantiationDependent to OpaqueValueExpr from its SourceExpr.

[rjmccall]

LGTM.

[rjmccall]

Oh, you know, this should really propagate all the dependence bits, not just instantiation-dependence. It would be safer, at least. You could probably find a contrived example involving value-dependence.

[manmanren]

In D18461#383218, @rjmccall wrote:

Oh, you know, this should really propagate all the dependence bits, not just instantiation-dependence. It would be safer, at least. You could probably find a contrived example involving value-dependence.

Thanks for the quick review, John!

I will propagate all the dependence bits and commit.

Cheers,
Manman

include/clang/AST/Expr.h

OpaqueValueExpr(SourceLocation Loc, QualType T, ExprValueKind VK,
                   Expr *SourceExpr = nullptr)
     : Expr(OpaqueValueExprClass, T, VK, OK,
            T->isDependentType(), 
            T->isDependentType() || 
            (SourceExpr && SourceExpr->isValueDependent()),
            T->isInstantiationDependentType(),
            false),
       SourceExpr(SourceExpr), Loc(Loc) {
+    if (SourceExpr)
+      ExprBits.InstantiationDependent |= SourceExpr->isInstantiationDependent();
   }
 
   /// Given an expression which invokes a copy constructor --- i.e.  a
   /// CXXConstructExpr, possibly wrapped in an ExprWithCleanups ---
   /// find the OpaqueValueExpr that's the source of the construction.
   static const OpaqueValueExpr *findInCopyConstruct(const Expr *expr);
 
   explicit OpaqueValueExpr(EmptyShell Empty)

include/clang/AST/Stmt.h

class ExprBitfields {
     friend class ObjCDictionaryLiteral; // ctor
     friend class ShuffleVectorExpr; // ctor
     friend class ParenListExpr; // ctor
     friend class CXXUnresolvedConstructExpr; // ctor
     friend class CXXDependentScopeMemberExpr; // ctor
     friend class OverloadExpr; // ctor
     friend class PseudoObjectExpr; // ctor
     friend class AtomicExpr; // ctor
+    friend class OpaqueValueExpr; // ctor
     unsigned : NumStmtBits;
 
     unsigned ValueKind : 2;
     unsigned ObjectKind : 2;
     unsigned TypeDependent : 1;
     unsigned ValueDependent : 1;
     unsigned InstantiationDependent : 1;
     unsigned ContainsUnexpandedParameterPack : 1;

test/SemaObjCXX/typo-correction.mm

+// RUN: %clang_cc1 %s -verify -fsyntax-only
+
+class ClassA {};
+
+class ClassB {
+public:
+  ClassB(ClassA* parent=0);
+  ~ClassB();
+};
+
+@interface NSObject
+@end
+
+@interface InterfaceA : NSObject
+@property(nonatomic, assign) ClassA *m_prop1; // expected-note {{here}}
+@property(nonatomic, assign) ClassB *m_prop2;
+@end
+
+@implementation InterfaceA
+- (id)test {
+  self.m_prop2 = new ClassB(m_prop1); // expected-error {{use of undeclared identifier 'm_prop1'; did you mean '_m_prop1'?}}
+}
+@end