Index: clang/lib/AST/Type.cpp
===================================================================
--- clang/lib/AST/Type.cpp
+++ clang/lib/AST/Type.cpp
@@ -751,6 +751,17 @@
 
 #define TRIVIAL_TYPE_CLASS(Class) \
   QualType Visit##Class##Type(const Class##Type *T) { return QualType(T, 0); }
+#define SUGARED_TYPE_CLASS(Class) \
+  QualType Visit##Class##Type(const Class##Type *T) { \
+    if (!T->isSugared()) \
+      return QualType(T, 0); \
+    QualType desugaredType = recurse(T->desugar()); \
+    if (desugaredType.isNull()) \
+      return {}; \
+    if (desugaredType.getAsOpaquePtr() == T->desugar().getAsOpaquePtr()) \
+      return QualType(T, 0); \
+    return desugaredType; \
+  }
 
   TRIVIAL_TYPE_CLASS(Builtin)
 
@@ -954,8 +965,8 @@
     return Ctx.getParenType(innerType);
   }
 
-  TRIVIAL_TYPE_CLASS(Typedef)
-  TRIVIAL_TYPE_CLASS(ObjCTypeParam)
+  SUGARED_TYPE_CLASS(Typedef)
+  SUGARED_TYPE_CLASS(ObjCTypeParam)
 
   QualType VisitAdjustedType(const AdjustedType *T) {
     QualType originalType = recurse(T->getOriginalType());
@@ -986,15 +997,15 @@
     return Ctx.getDecayedType(originalType);
   }
 
-  TRIVIAL_TYPE_CLASS(TypeOfExpr)
-  TRIVIAL_TYPE_CLASS(TypeOf)
-  TRIVIAL_TYPE_CLASS(Decltype)
-  TRIVIAL_TYPE_CLASS(UnaryTransform)
+  SUGARED_TYPE_CLASS(TypeOfExpr)
+  SUGARED_TYPE_CLASS(TypeOf)
+  SUGARED_TYPE_CLASS(Decltype)
+  SUGARED_TYPE_CLASS(UnaryTransform)
   TRIVIAL_TYPE_CLASS(Record)
   TRIVIAL_TYPE_CLASS(Enum)
 
   // FIXME: Non-trivial to implement, but important for C++
-  TRIVIAL_TYPE_CLASS(Elaborated)
+  SUGARED_TYPE_CLASS(Elaborated)
 
   QualType VisitAttributedType(const AttributedType *T) {
     QualType modifiedType = recurse(T->getModifiedType());
@@ -1029,7 +1040,7 @@
   }
 
   // FIXME: Non-trivial to implement, but important for C++
-  TRIVIAL_TYPE_CLASS(TemplateSpecialization)
+  SUGARED_TYPE_CLASS(TemplateSpecialization)
 
   QualType VisitAutoType(const AutoType *T) {
     if (!T->isDeduced())
@@ -1048,7 +1059,7 @@
   }
 
   // FIXME: Non-trivial to implement, but important for C++
-  TRIVIAL_TYPE_CLASS(PackExpansion)
+  SUGARED_TYPE_CLASS(PackExpansion)
 
   QualType VisitObjCObjectType(const ObjCObjectType *T) {
     QualType baseType = recurse(T->getBaseType());
@@ -1106,6 +1117,7 @@
   }
 
 #undef TRIVIAL_TYPE_CLASS
+#undef SUGARED_TYPE_CLASS
 };
 
 } // namespace
Index: clang/test/SemaObjC/parameterized_classes_subst.m
===================================================================
--- clang/test/SemaObjC/parameterized_classes_subst.m
+++ clang/test/SemaObjC/parameterized_classes_subst.m
@@ -104,6 +104,12 @@
 @property (nonatomic,retain) ViewType view;
 @end
 
+@interface TypedefTypeParam<T> : NSObject
+typedef T AliasT;
+- (void)test:(AliasT)object;
+// expected-note@-1 {{parameter 'object' here}}
+@end
+
 // --------------------------------------------------------------------------
 // Nullability
 // --------------------------------------------------------------------------
@@ -190,6 +196,7 @@
        MutableSetOfArrays<NSString *> *mutStringArraySet,
        NSMutableSet *mutSet,
        MutableSetOfArrays *mutArraySet,
+       TypedefTypeParam<NSString *> *typedefTypeParam,
        void (^block)(void)) {
   Window *window;
 
@@ -199,6 +206,7 @@
   [mutStringArraySet addObject: window]; // expected-warning{{parameter of type 'NSArray<NSString *> *'}}
   [mutSet addObject: window]; // expected-warning{{parameter of incompatible type 'id<NSCopying>'}}
   [mutArraySet addObject: window]; // expected-warning{{parameter of incompatible type 'id<NSCopying>'}}
+  [typedefTypeParam test: window]; // expected-warning{{parameter of type 'NSString *'}}
   [block addObject: window]; // expected-warning{{parameter of incompatible type 'id<NSCopying>'}}
 }