[lldb] Ignore type sugar in TypeSystemClang::GetPointerType

Summary:
Currently having a typedef for ObjC types is breaking member access in LLDB:
```
typedef NSString Str;
NSString *s; s.length; // OK
Str *s; s.length; // Causes: member reference base type 'Str *' (aka 'NSString *') is not a structure or union
```

This works for NSString as there the type building from `NSString` -> `NSString *` will correctly
build a ObjCObjectPointerType (which is necessary to make member access with a dot possible),
but for the typedef the `Str` -> `Str *` conversion will produce an incorrect PointerType. The reason
for this is that our check in TypeSystemClang::GetPointerType is not desugaring the base type,
which causes that `Str` is not recognised as a type to a `ObjCInterface` as the check only sees the
typedef sugar that was put around it. This causes that we fall back to constructing a PointerType
instead which does not allow member access with the dot operator.

This patch just changes the check to look at the desugared type instead.

Fixes rdar://17525603

Reviewers: shafik, mib

Reviewed By: mib

Subscribers: mib, JDevlieghere, lldb-commits

Tags: #lldb

Differential Revision: https://reviews.llvm.org/D73952

lldb/packages/Python/lldbsuite/test/lang/objc/objc-property/TestObjCProperty.py

@@ -110,6 +110,11 @@ class ObjCPropertyTestCase(TestBase):
         self.assertTrue(backed_value.GetValueAsUnsigned(12345)
                         == backing_value.GetValueAsUnsigned(23456))
 
+        value_from_typedef = frame.EvaluateExpression("typedefd.backedInt", False)
+        self.assertTrue(value_from_typedef.GetError().Success())
+        self.assertEqual(value_from_typedef.GetValueAsUnsigned(12345),
+                         backing_value.GetValueAsUnsigned(23456))
+
         unbacked_value = frame.EvaluateExpression("mine.unbackedInt", False)
         unbacked_error = unbacked_value.GetError()
         self.assertTrue(unbacked_error.Success())

lldb/packages/Python/lldbsuite/test/lang/objc/objc-property/main.m

@@ -87,10 +87,13 @@ static int _class_int = 123;
 }
 @end
 
+typedef BaseClass TypedefBaseClass;
+
 int
 main ()
 {
   BaseClass *mine = [BaseClass baseClassWithBackedInt: 10 andUnbackedInt: 20];
+  TypedefBaseClass *typedefd = mine;
   
   // Set a breakpoint here.
   int nonexistant = mine.nonexistantInt;

lldb/source/Plugins/TypeSystem/Clang/TypeSystemClang.cpp

@@ -4259,8 +4259,7 @@ TypeSystemClang::GetPointerType(lldb::opaque_compiler_type_t type) {
   if (type) {
     clang::QualType qual_type(GetQualType(type));
 
-    const clang::Type::TypeClass type_class = qual_type->getTypeClass();
-    switch (type_class) {
+    switch (qual_type.getDesugaredType(getASTContext())->getTypeClass()) {
     case clang::Type::ObjCObject:
     case clang::Type::ObjCInterface:
       return GetType(getASTContext().getObjCObjectPointerType(qual_type));