[PATCH][ObjC] Cleanup ObjCInterfaceDecl lookup for ObjC literals

[John McCall]

> On Jul 23, 2015, at 8:33 AM, AlexDenisov <1101.debian at gmail.com> wrote:
>> Then, on the Sema side, you should define an enum that corresponds to
>> the different cases in that second parameter.
> 
> I just reused ObjCLiteralKind, seems it fits for this task very well.

Sounds good.

>> If you do this, you should be able to unify all the different diagnostics for
>> NSNumber/NSArray/NSValue.
> 
> Merged all specific errors into one err_undeclared_objc_literal_class, as you suggested.
> 
> New version attached.
> 
> <lookup_objc_literal_interface_decl.patch>

+static bool ValidateObjCLiteralInterfaceDecl(Sema &S, ObjCInterfaceDecl *Decl,
+                                             SourceLocation Loc,
+                                             NSAPI::NSClassIdKindKind ClassKind) {

I think it would make more sense to have this take an ObjCLiteralKind
and then map that to a NSAPI::NSClassIdKindKind than the other way
around.

+  ObjCInterfaceDecl *Decl = nullptr;
+  IdentifierInfo *II = S.NSAPIObj->getNSClassId(ClassKind);
+  NamedDecl *IF = S.LookupSingleName(S.TUScope, II, Loc,
+                                     Sema::LookupOrdinaryName);
+  Decl = dyn_cast_or_null<ObjCInterfaceDecl>(IF);

You should declare variables as close as possible to the point they’re initialized,
and you should try to avoid naming variables the same as a type.

So, specifically, please make this
  ObjCInterfaceDecl *ID = dyn_cast_or_null<ObjCInterfaceDecl>(IF);

Otherwise, this looks good, thanks!

John.