Revert rL301328 and add tests for the regressions introduced.

[emilio]

Summary

See https://reviews.llvm.org/D32348#738704

[rsmith]

I'm OK with this from a mechanical perspective. But there's also a libclang design question here: what should the libclang methods to query template arguments for a type cursor representing an alias template specialization actually do? Should there be some way for a libclang user to choose what result they get?

One way we could make the behavior fully consistent (and more backwards-compatible with pre-clang-4.0) would be to revert both this and D26663, and provide the information that D26663 wanted to expose by another set of interface functions. What do other people with an interest in the libclang interface think?

[emilio]

I'm personally fine with this behavior in particular, given you can check the cursor you're querying to know if it's a typedef or alias specialization. Of course I'm not the only one using libclang, though, so I'd be interested in hearing other people's opinion.

I think that we should try to prevent this _third_ different behavior to stay in tree in the meantime, though, what do you think?

[rsmith]

Yes, let's first revert back to the clang 4.0 behavior, then please mail cfe-dev to discuss what the right behavior should be.

[emilio]

I sent http://lists.llvm.org/pipermail/cfe-dev/2017-May/053703.html

cfe/trunk/test/Index/print-type.cpp

 struct Specialization {};
 
 template<>
 struct Specialization<int>;
 
 Specialization<Specialization<bool>& > templRefParam;
 auto autoTemplRefParam = templRefParam;
 
-template<typename T, typename U = int>
-struct DefaultedTypeExample {};
-
-typedef DefaultedTypeExample<int> DefaultedTypeAlias;
+template<typename T> struct A {};
+template<typename T> using C = T;
+using baz = C<A<void>>;
 
 // RUN: c-index-test -test-print-type %s -std=c++14 | FileCheck %s
 // CHECK: Namespace=outer:1:11 (Definition) [type=] [typekind=Invalid] [isPOD=0]
 // CHECK: ClassTemplate=Foo:4:8 (Definition) [type=] [typekind=Invalid] [isPOD=0]
 // CHECK: TemplateTypeParameter=T:3:19 (Definition) [type=T] [typekind=Unexposed] [canonicaltype=type-parameter-0-0] [canonicaltypekind=Unexposed] [isPOD=0]
 // CHECK: FieldDecl=t:5:5 (Definition) [type=T] [typekind=Unexposed] [canonicaltype=type-parameter-0-0] [canonicaltypekind=Unexposed] [isPOD=0]
 // CHECK: TypeRef=T:3:19 [type=T] [typekind=Unexposed] [canonicaltype=type-parameter-0-0] [canonicaltypekind=Unexposed] [isPOD=0]
 // CHECK: ClassTemplate=Baz:9:8 (Definition) [type=] [typekind=Invalid] [isPOD=0]

 // CHECK: DeclRefExpr=z:22:35 [type=outer::inner::Bar::FooType] [typekind=Typedef] [canonicaltype=int] [canonicaltypekind=Int] [isPOD=1]
 // CHECK: TypedefDecl=OtherType:26:18 (Definition) [type=outer::inner::Bar::OtherType] [typekind=Typedef] [canonicaltype=double] [canonicaltypekind=Double] [isPOD=1]
 // CHECK: TypedefDecl=ArrayType:27:15 (Definition) [type=outer::inner::Bar::ArrayType] [typekind=Typedef] [canonicaltype=int [5]] [canonicaltypekind=ConstantArray] [isPOD=1]
 // CHECK: IntegerLiteral= [type=int] [typekind=Int] [isPOD=1]
 // CHECK: FieldDecl=baz:28:20 (Definition) [type=Baz<int, 1, Foo>] [typekind=Unexposed] [templateargs/3= [type=int] [typekind=Int]] [canonicaltype=outer::Baz<int, 1, Foo>] [canonicaltypekind=Record] [canonicaltemplateargs/3= [type=int] [typekind=Int]] [isPOD=1]
 // CHECK: TemplateRef=Baz:9:8 [type=] [typekind=Invalid] [isPOD=0]
 // CHECK: IntegerLiteral= [type=int] [typekind=Int] [isPOD=1]
 // CHECK: TemplateRef=Foo:4:8 [type=] [typekind=Invalid] [isPOD=0]
-// CHECK: FieldDecl=qux:29:38 (Definition) [type=Qux<int, char *, Foo<int>, outer::inner::Bar::FooType>] [typekind=Unexposed] [templateargs/4= [type=int] [typekind=Int] [type=char *] [typekind=Pointer] [type=outer::Foo<int>] [typekind=Record] [type=int] [typekind=Int]] [canonicaltype=outer::Qux<int, char *, outer::Foo<int>, int>] [canonicaltypekind=Record] [canonicaltemplateargs/4= [type=int] [typekind=Int] [type=char *] [typekind=Pointer] [type=outer::Foo<int>] [typekind=Record] [type=int] [typekind=Int]] [isPOD=1]
+// CHECK: FieldDecl=qux:29:38 (Definition) [type=Qux<int, char *, Foo<int>, outer::inner::Bar::FooType>] [typekind=Unexposed] [templateargs/4= [type=int] [typekind=Int] [type=char *] [typekind=Pointer] [type=Foo<int>] [typekind=Unexposed] [type=outer::inner::Bar::FooType] [typekind=Typedef]] [canonicaltype=outer::Qux<int, char *, outer::Foo<int>, int>] [canonicaltypekind=Record] [canonicaltemplateargs/4= [type=int] [typekind=Int] [type=char *] [typekind=Pointer] [type=outer::Foo<int>] [typekind=Record] [type=int] [typekind=Int]] [isPOD=1]
 // CHECK: TemplateRef=Qux:12:8 [type=] [typekind=Invalid] [isPOD=0]
 // CHECK: TemplateRef=Foo:4:8 [type=] [typekind=Invalid] [isPOD=0]
 // CHECK: FunctionTemplate=tbar:36:3 [type=T (int)] [typekind=FunctionProto] [canonicaltype=type-parameter-0-0 (int)] [canonicaltypekind=FunctionProto] [resulttype=T] [resulttypekind=Unexposed] [isPOD=0]
 // CHECK: TemplateTypeParameter=T:35:20 (Definition) [type=T] [typekind=Unexposed] [canonicaltype=type-parameter-0-0] [canonicaltypekind=Unexposed] [isPOD=0]
 // CHECK: TypeRef=T:35:20 [type=T] [typekind=Unexposed] [canonicaltype=type-parameter-0-0] [canonicaltypekind=Unexposed] [isPOD=0]
 // CHECK: ParmDecl=:36:11 (Definition) [type=int] [typekind=Int] [isPOD=1]
 // CHECK: FunctionTemplate=tbar:39:3 [type=T (int *)] [typekind=FunctionProto] [canonicaltype=type-parameter-0-0 (int *)] [canonicaltypekind=FunctionProto] [resulttype=T] [resulttypekind=Unexposed] [isPOD=0]
 // CHECK: TemplateTypeParameter=T:38:20 (Definition) [type=T] [typekind=Unexposed] [canonicaltype=type-parameter-0-0] [canonicaltypekind=Unexposed] [isPOD=0]

 // CHECK: StructDecl=Specialization:69:8 [Specialization of Specialization:66:8] [type=Specialization<int>] [typekind=Record] [templateargs/1= [type=int] [typekind=Int]] [isPOD=0]
 // CHECK: VarDecl=templRefParam:71:40 (Definition) [type=Specialization<Specialization<bool> &>] [typekind=Unexposed] [templateargs/1= [type=Specialization<bool> &] [typekind=LValueReference]] [canonicaltype=Specialization<Specialization<bool> &>] [canonicaltypekind=Record] [canonicaltemplateargs/1= [type=Specialization<bool> &] [typekind=LValueReference]] [isPOD=1]
 // CHECK: TemplateRef=Specialization:66:8 [type=] [typekind=Invalid] [isPOD=0]
 // CHECK: CallExpr=Specialization:66:8 [type=Specialization<Specialization<bool> &>] [typekind=Unexposed] [templateargs/1= [type=Specialization<bool> &] [typekind=LValueReference]] [canonicaltype=Specialization<Specialization<bool> &>] [canonicaltypekind=Record] [canonicaltemplateargs/1= [type=Specialization<bool> &] [typekind=LValueReference]] [isPOD=1]
 // CHECK: VarDecl=autoTemplRefParam:72:6 (Definition) [type=Specialization<Specialization<bool> &>] [typekind=Auto] [templateargs/1= [type=Specialization<bool> &] [typekind=LValueReference]] [canonicaltype=Specialization<Specialization<bool> &>] [canonicaltypekind=Record] [canonicaltemplateargs/1= [type=Specialization<bool> &] [typekind=LValueReference]] [isPOD=1]
 // CHECK: UnexposedExpr=templRefParam:71:40 [type=const Specialization<Specialization<bool> &>] [typekind=Unexposed] const [templateargs/1= [type=Specialization<bool> &] [typekind=LValueReference]] [canonicaltype=const Specialization<Specialization<bool> &>] [canonicaltypekind=Record] [canonicaltemplateargs/1= [type=Specialization<bool> &] [typekind=LValueReference]] [isPOD=1]
 // CHECK: DeclRefExpr=templRefParam:71:40 [type=Specialization<Specialization<bool> &>] [typekind=Unexposed] [templateargs/1= [type=Specialization<bool> &] [typekind=LValueReference]] [canonicaltype=Specialization<Specialization<bool> &>] [canonicaltypekind=Record] [canonicaltemplateargs/1= [type=Specialization<bool> &] [typekind=LValueReference]] [isPOD=1]
 // CHECK: TypedefDecl=DefaultedTypeAlias:77:35 (Definition) [type=DefaultedTypeAlias] [typekind=Typedef] [templateargs/2= [type=int] [typekind=Int] [type=int] [typekind=Int]] [canonicaltype=DefaultedTypeExample<int, int>] [canonicaltypekind=Record] [canonicaltemplateargs/2= [type=int] [typekind=Int] [type=int] [typekind=Int]] [isPOD=0]
+// CHECK: TypeAliasDecl=baz:76:7 (Definition) [type=baz] [typekind=Typedef] [templateargs/1= [type=A<void>] [typekind=Unexposed]] [canonicaltype=A<void>] [canonicaltypekind=Record] [canonicaltemplateargs/1= [type=void] [typekind=Void]] [isPOD=0]

cfe/trunk/tools/libclang/CXType.cpp

 
 static inline CXTranslationUnit GetTU(CXType CT) {
   return static_cast<CXTranslationUnit>(CT.data[1]);
 }
 
 static Optional<ArrayRef<TemplateArgument>>
 GetTemplateArguments(QualType Type) {
   assert(!Type.isNull());
+  if (const auto *Specialization = Type->getAs<TemplateSpecializationType>())
+    return Specialization->template_arguments();
+
   if (const auto *RecordDecl = Type->getAsCXXRecordDecl()) {
     const auto *TemplateDecl =
       dyn_cast<ClassTemplateSpecializationDecl>(RecordDecl);
     if (TemplateDecl)
       return TemplateDecl->getTemplateArgs().asArray();
   }
 
-  if (const auto *Specialization = Type->getAs<TemplateSpecializationType>())
-    return Specialization->template_arguments();
-
   return None;
 }
 
 static Optional<QualType> TemplateArgumentToQualType(const TemplateArgument &A) {
   if (A.getKind() == TemplateArgument::Type)
     return A.getAsType();
   return None;
 }