[Sema] PR25156 Crash when parsing dtor call on incomplete type

[hintonda]

Summary

Fix crash from PR25156 where getDestructorName() calls LookupQualifiedName() on incomplete type.

[hintonda]

• Simplify diff

[hintonda]

Rebase and move test to existing file.

[rjmccall]

lib/Sema/SemaExprCXX.cpp

192–194

You should probably respond to the incomplete context within this case (by returning nullptr, I guess) instead of falling down into the else.

[hintonda]

• Addressed comments.

[rjmccall]

Thanks, looks great.

If you're going to be submitting multiple patches, you should really ask for commit access; it's not an arduous process.

[hintonda]

Committed in r305169.

lib/Sema/SemaExprCXX.cpp

ParsedType Sema::getDestructorName(SourceLocation TildeLoc,
 
   TypeDecl *NonMatchingTypeDecl = nullptr;
   LookupResult Found(*this, &II, NameLoc, LookupOrdinaryName);
   for (unsigned Step = 0; Step != 2; ++Step) {
     // Look for the name first in the computed lookup context (if we
     // have one) and, if that fails to find a match, in the scope (if
     // we're allowed to look there).
     Found.clear();
-    if (Step == 0 && LookupCtx)
+    if (Step == 0 && LookupCtx) {
+      if (RequireCompleteDeclContext(SS, LookupCtx))
+        return nullptr;
       LookupQualifiedName(Found, LookupCtx);
-    else if (Step == 1 && LookInScope && S)
+    } else if (Step == 1 && LookInScope && S) {
       LookupName(Found, S);
-    else
+    } else {
       continue;
+    }
 
     // FIXME: Should we be suppressing ambiguities here?
     if (Found.isAmbiguous())
       return nullptr;
 
     if (TypeDecl *Type = Found.getAsSingle<TypeDecl>()) {
       QualType T = Context.getTypeDeclType(Type);
       MarkAnyDeclReferenced(Type->getLocation(), Type, /*OdrUse=*/false);

test/SemaCXX/nested-name-spec.cpp

 }
 void ::global_func2(int) { } // expected-warning{{extra qualification on member 'global_func2'}}
 
 void N::f() { } // okay
 
 struct Y;  // expected-note{{forward declaration of 'Y'}}
 Y::foo y; // expected-error{{incomplete type 'Y' named in nested name specifier}}
 
+namespace PR25156 {
+struct Y;  // expected-note{{forward declaration of 'PR25156::Y'}}
+void foo() {
+  Y::~Y(); // expected-error{{incomplete type 'PR25156::Y' named in nested name specifier}}
+}
+}
+
 X::X() : a(5) { } // expected-error{{use of undeclared identifier 'X'}}
 
 struct foo_S {
   static bool value;
 };
 bool (foo_S::value);