[Concepts] Fix ast dump for immediately declared constraint.

[nridge]

clang/test/AST/ast-dump-concepts.cpp

5

nit: perhaps use a more generic name like binary_concept (meaning concept that takes two types)

[nridge]

clang/test/AST/ast-dump-concepts.cpp

13

another nit: the requires(true) is not relevant to the testcase.

(Although, perhaps it is another bug that it does not appear in the dump?)

[riccibruno]

clang/test/AST/ast-dump-concepts.cpp

2

Can you also test for serialization by round-tripping through a PCH (see the other AST dump tests for examples; you just need to add two RUN lines)?

[hokein]

address review comments.

clang/lib/AST/TextNodeDumper.cpp

void TextNodeDumper::VisitTemplateTypeParmDecl(const TemplateTypeParmDecl *D) {
   if (const auto *TC = D->getTypeConstraint()) {
     OS << " ";
     dumpBareDeclRef(TC->getNamedConcept());
     if (TC->getNamedConcept() != TC->getFoundDecl()) {
       OS << " (";
       dumpBareDeclRef(TC->getFoundDecl());
       OS << ")";
     }
-    Visit(TC->getImmediatelyDeclaredConstraint());
+    AddChild([=] { Visit(TC->getImmediatelyDeclaredConstraint()); });
   } else if (D->wasDeclaredWithTypename())
     OS << " typename";
   else
     OS << " class";
   OS << " depth " << D->getDepth() << " index " << D->getIndex();
   if (D->isParameterPack())
     OS << " ...";
   dumpName(D);

clang/test/AST/ast-dump-concepts.cpp

+// RUN: %clang_cc1 -triple x86_64-unknown-unknown -std=c++2a -ast-dump -ast-dump-filter Foo %s | FileCheck -strict-whitespace %s
+
+// Test with serialization:
+// RUN: %clang_cc1 -std=c++20 -triple x86_64-unknown-unknown -emit-pch -o %t %s
+// RUN: %clang_cc1 -x c++ -std=c++20 -triple x86_64-unknown-unknown -include-pch %t \
+// RUN: -ast-dump-all -ast-dump-filter Foo /dev/null \
+// RUN: | FileCheck --strict-whitespace %s
+
+template <typename T, typename U>
+concept binary_concept = true;
+
+template <typename T>
+struct Foo {
+  // CHECK:      TemplateTypeParmDecl {{.*}} referenced Concept {{.*}} 'binary_concept'
+  // CHECK-NEXT: |-ConceptSpecializationExpr {{.*}} 'bool'
+  // CHECK-NEXT: `-TemplateArgument {{.*}} type 'int'
+  template <binary_concept<int> R>
+  Foo(R);
+};