[clang] fix printing of canonical template template parameters (#93124)

Author: mizvekov

clang/lib/AST/TemplateBase.cpp

@@ -538,9 +538,19 @@ void TemplateArgument::print(const PrintingPolicy &Policy, raw_ostream &Out,
     Out << "nullptr";
     break;
 
-  case Template:
-    getAsTemplate().print(Out, Policy, TemplateName::Qualified::Fully);
+  case Template: {
+    TemplateName TN = getAsTemplate();
+    if (const auto *TD = TN.getAsTemplateDecl();
+        TD && TD->getDeclName().isEmpty()) {
+      assert(isa<TemplateTemplateParmDecl>(TD) &&
+             "Unexpected anonymous template");
+      const auto *TTP = cast<TemplateTemplateParmDecl>(TD);
+      Out << "template-parameter-" << TTP->getDepth() << "-" << TTP->getIndex();
+    } else {
+      TN.print(Out, Policy, TemplateName::Qualified::Fully);
+    }
     break;
+  }
 
   case TemplateExpansion:
     getAsTemplateOrTemplatePattern().print(Out, Policy);

clang/test/SemaCXX/cxx20-ctad-type-alias.cpp

@@ -284,7 +284,7 @@ class Foo {};
 // Verify that template template type parameter TTP is referenced/used in the
 // template arguments of the RHS.
 template <template<typename> typename TTP>
-using Bar = Foo<K<TTP>>; // expected-note {{candidate template ignored: could not match 'Foo<K<>>' against 'int'}}
+using Bar = Foo<K<TTP>>; // expected-note {{candidate template ignored: could not match 'Foo<K<template-parameter-0-0>>' against 'int'}}
 
 template <class T>
 class Container {};

clang/test/SemaTemplate/deduction-guide.cpp

@@ -102,9 +102,9 @@ using CT = C<int>;
 // CHECK: |-NonTypeTemplateParmDecl {{.*}} 'type-parameter-0-2' depth 0 index 3 V
 // CHECK: | `-TemplateArgument {{.*}} expr
 // CHECK: |   `-IntegerLiteral {{.*}} 'int' 0
-// CHECK: |-CXXDeductionGuideDecl {{.*}} 'auto (A, Y<>, type-parameter-0-2) -> C<A>'
+// CHECK: |-CXXDeductionGuideDecl {{.*}} 'auto (A, Y<template-parameter-0-1>, type-parameter-0-2) -> C<A>'
 // CHECK: | |-ParmVarDecl {{.*}} 'A'
-// CHECK: | |-ParmVarDecl {{.*}} 'Y<>'
+// CHECK: | |-ParmVarDecl {{.*}} 'Y<template-parameter-0-1>'
 // CHECK: | `-ParmVarDecl {{.*}} 'type-parameter-0-2'
 // CHECK: `-CXXDeductionGuideDecl {{.*}} 'auto (int, Y<B>, int) -> C<int>'
 // CHECK:  |-TemplateArgument type 'int'
@@ -114,12 +114,12 @@ using CT = C<int>;
 // CHECK:  |-ParmVarDecl {{.*}} 'int'
 // CHECK:  |-ParmVarDecl {{.*}} 'Y<B>'
 // CHECK:  `-ParmVarDecl {{.*}} 'int'
-// CHECK: FunctionProtoType {{.*}} 'auto (A, Y<>, type-parameter-0-2) -> C<A>' dependent trailing_return cdecl
+// CHECK: FunctionProtoType {{.*}} 'auto (A, Y<template-parameter-0-1>, type-parameter-0-2) -> C<A>' dependent trailing_return cdecl
 // CHECK: |-InjectedClassNameType {{.*}} 'C<A>' dependent
 // CHECK: |-TemplateTypeParmType {{.*}} 'A' dependent depth 0 index 0
 // CHECK: | `-TemplateTypeParm {{.*}} 'A'
-// CHECK: |-ElaboratedType {{.*}} 'Y<>' sugar dependent
-// CHECK: | `-TemplateSpecializationType {{.*}} 'Y<>' dependent Y
+// CHECK: |-ElaboratedType {{.*}} 'Y<template-parameter-0-1>' sugar dependent
+// CHECK: | `-TemplateSpecializationType {{.*}} 'Y<template-parameter-0-1>' dependent Y
 // CHECK: |   `-TemplateArgument template
 // CHECK: `-TemplateTypeParmType {{.*}} 'type-parameter-0-2' dependent depth 0 index 2
 

clang/test/SemaTemplate/make_integer_seq.cpp

@@ -61,7 +61,7 @@ using test2 = B<int, 1>;
 
 template <template <class T, T...> class S, class T, int N> struct C {
   using test3 = __make_integer_seq<S, T, N>;
-//      CHECK: |-TypeAliasDecl 0x{{[0-9A-Fa-f]+}} <line:63:3, col:43> col:9 test3 '__make_integer_seq<S, T, N>':'__make_integer_seq<type-parameter-0-1, N>'
+//      CHECK: |-TypeAliasDecl 0x{{[0-9A-Fa-f]+}} <line:63:3, col:43> col:9 test3 '__make_integer_seq<S, T, N>':'__make_integer_seq<template-parameter-0-0, type-parameter-0-1, N>'
 // CHECK-NEXT:   `-ElaboratedType 0x{{[0-9A-Fa-f]+}} '__make_integer_seq<S, T, N>' sugar dependent
 // CHECK-NEXT:     `-TemplateSpecializationType 0x{{[0-9A-Fa-f]+}} '__make_integer_seq<S, T, N>' sugar dependent alias __make_integer_seq
 // CHECK-NEXT:       |-TemplateArgument template S
@@ -71,7 +71,7 @@ template <template <class T, T...> class S, class T, int N> struct C {
 // CHECK-NEXT:       |-TemplateArgument expr
 // CHECK-NEXT:       | `-ImplicitCastExpr 0x{{[0-9A-Fa-f]+}} <col:42> 'T' <Dependent>
 // CHECK-NEXT:       |   `-DeclRefExpr 0x{{[0-9A-Fa-f]+}} <col:42> 'int' NonTypeTemplateParm 0x{{[0-9A-Fa-f]+}} 'N' 'int'
-// CHECK-NEXT:       `-TemplateSpecializationType 0x{{[0-9A-Fa-f]+}} '__make_integer_seq<type-parameter-0-1, N>' dependent __make_integer_seq
+// CHECK-NEXT:       `-TemplateSpecializationType 0x{{[0-9A-Fa-f]+}} '__make_integer_seq<template-parameter-0-0, type-parameter-0-1, N>' dependent __make_integer_seq
 // CHECK-NEXT:         |-TemplateArgument template
 // CHECK-NEXT:         |-TemplateArgument type 'type-parameter-0-1'
 // CHECK-NEXT:         | `-TemplateTypeParmType 0x{{[0-9A-Fa-f]+}} 'type-parameter-0-1' dependent depth 0 index 1