[clang][DeclPrinter] Implement visitors for {TemplateType,NonTypeTemplate}Parms

[merge_guards_bot]

Unit tests: pass. 62330 tests passed, 0 failed and 838 were skipped.

clang-tidy: pass.

clang-format: pass.

Build artifacts: diff.json, clang-tidy.txt, clang-format.patch, CMakeCache.txt, console-log.txt, test-results.xml

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[hokein]

if it is trivial, it would be nice to add some unittests in clang/unittests/AST/DeclPrinterTest.cpp.

[kadircet]

• Add unittests to ASTDeclPrinter

clang-tools-extra/clangd/unittests/FindTargetTests.cpp

Code = R"cpp(
     int x = a::[[X::]]y;
   )cpp";
   EXPECT_DECLS("NestedNameSpecifierLoc", "struct X");
 
   Code = R"cpp(
     template <typename T>
     int x = [[T::]]y;
   )cpp";
-  // FIXME: We don't do a good job printing TemplateTypeParmDecls, apparently!
-  EXPECT_DECLS("NestedNameSpecifierLoc", "");
+  EXPECT_DECLS("NestedNameSpecifierLoc", "typename T");
 
   Code = R"cpp(
     namespace a { int x; }
     namespace b = a;
     int y = [[b]]::x;
   )cpp";
   EXPECT_DECLS("NestedNameSpecifierLoc", {"namespace b = a", Rel::Alias},
                {"namespace a", Rel::Underlying});
TEST_F(TargetDeclTest, Types) {
 
   // FIXME: Auto-completion in a template requires disabling delayed template
   // parsing.
   Flags = {"-fno-delayed-template-parsing"};
   Code = R"cpp(
     template<class T>
     void foo() { [[T]] x; }
   )cpp";
-  // FIXME: We don't do a good job printing TemplateTypeParmDecls, apparently!
-  EXPECT_DECLS("TemplateTypeParmTypeLoc", "");
+  EXPECT_DECLS("TemplateTypeParmTypeLoc", "class T");
   Flags.clear();
 
   // FIXME: Auto-completion in a template requires disabling delayed template
   // parsing.
   Flags = {"-fno-delayed-template-parsing"};
   Code = R"cpp(
     template<template<typename> class T>
     void foo() { [[T<int>]] x; }
TEST_F(TargetDeclTest, Types) {
   EXPECT_DECLS("AutoTypeLoc");
 
   Code = R"cpp(
     template <typename... E>
     struct S {
       static const int size = sizeof...([[E]]);
     };
   )cpp";
-  // FIXME: We don't do a good job printing TemplateTypeParmDecls, apparently!
-  EXPECT_DECLS("SizeOfPackExpr", "");
+  EXPECT_DECLS("SizeOfPackExpr", "typename ...E");
 
   Code = R"cpp(
     template <typename T>
     class Foo {
       void f([[Foo]] x);
     };
   )cpp";
   EXPECT_DECLS("InjectedClassNameTypeLoc", "class Foo");

clang/lib/AST/DeclPrinter.cpp

public:
     void VisitUsingDecl(UsingDecl *D);
     void VisitUsingShadowDecl(UsingShadowDecl *D);
     void VisitOMPThreadPrivateDecl(OMPThreadPrivateDecl *D);
     void VisitOMPAllocateDecl(OMPAllocateDecl *D);
     void VisitOMPRequiresDecl(OMPRequiresDecl *D);
     void VisitOMPDeclareReductionDecl(OMPDeclareReductionDecl *D);
     void VisitOMPDeclareMapperDecl(OMPDeclareMapperDecl *D);
     void VisitOMPCapturedExprDecl(OMPCapturedExprDecl *D);
+    void VisitTemplateTypeParmDecl(const TemplateTypeParmDecl *TTP);
+    void VisitNonTypeTemplateParmDecl(const NonTypeTemplateParmDecl *NTTP);
 
     void printTemplateParameters(const TemplateParameterList *Params,
                                  bool OmitTemplateKW = false);
     void printTemplateArguments(llvm::ArrayRef<TemplateArgument> Args);
     void printTemplateArguments(llvm::ArrayRef<TemplateArgumentLoc> Args);
     void prettyPrintAttributes(Decl *D);
     void prettyPrintPragmas(Decl *D);
     void printDeclType(QualType T, StringRef DeclName, bool Pack = false);
for (const Decl *Param : *Params) {
     if (Param->isImplicit())
       continue;
 
     if (NeedComma)
       Out << ", ";
     else
       NeedComma = true;
 
-    if (auto TTP = dyn_cast<TemplateTypeParmDecl>(Param)) {
-
-      if (const TypeConstraint *TC = TTP->getTypeConstraint())
-        TC->print(Out, Policy);
-      else if (TTP->wasDeclaredWithTypename())
-        Out << "typename";
-      else
-        Out << "class";
-
-      if (TTP->isParameterPack())
-        Out << " ...";
-      else if (!TTP->getName().empty())
-        Out << ' ';
-
-      Out << *TTP;
-
-      if (TTP->hasDefaultArgument()) {
-        Out << " = ";
-        Out << TTP->getDefaultArgument().getAsString(Policy);
-      };
+    if (const auto *TTP = dyn_cast<TemplateTypeParmDecl>(Param)) {
+      VisitTemplateTypeParmDecl(TTP);
     } else if (auto NTTP = dyn_cast<NonTypeTemplateParmDecl>(Param)) {
-      StringRef Name;
-      if (IdentifierInfo *II = NTTP->getIdentifier())
-        Name = II->getName();
-      printDeclType(NTTP->getType(), Name, NTTP->isParameterPack());
-
-      if (NTTP->hasDefaultArgument()) {
-        Out << " = ";
-        NTTP->getDefaultArgument()->printPretty(Out, nullptr, Policy,
-                                                Indentation);
-      }
+      VisitNonTypeTemplateParmDecl(NTTP);
     } else if (auto TTPD = dyn_cast<TemplateTemplateParmDecl>(Param)) {
       VisitTemplateDecl(TTPD);
       // FIXME: print the default argument, if present.
     }
   }
 
   Out << '>';
   if (!OmitTemplateKW)
if (!D->isInvalidDecl()) {
     }
   }
 }
 
 void DeclPrinter::VisitOMPCapturedExprDecl(OMPCapturedExprDecl *D) {
   D->getInit()->printPretty(Out, nullptr, Policy, Indentation);
 }
 
+void DeclPrinter::VisitTemplateTypeParmDecl(const TemplateTypeParmDecl *TTP) {
+  if (const TypeConstraint *TC = TTP->getTypeConstraint())
+    TC->print(Out, Policy);
+  else if (TTP->wasDeclaredWithTypename())
+    Out << "typename";
+  else
+    Out << "class";
+
+  if (TTP->isParameterPack())
+    Out << " ...";
+  else if (!TTP->getName().empty())
+    Out << ' ';
+
+  Out << *TTP;
+
+  if (TTP->hasDefaultArgument()) {
+    Out << " = ";
+    Out << TTP->getDefaultArgument().getAsString(Policy);
+  }
+}
+
+void DeclPrinter::VisitNonTypeTemplateParmDecl(
+    const NonTypeTemplateParmDecl *NTTP) {
+  StringRef Name;
+  if (IdentifierInfo *II = NTTP->getIdentifier())
+    Name = II->getName();
+  printDeclType(NTTP->getType(), Name, NTTP->isParameterPack());
+
+  if (NTTP->hasDefaultArgument()) {
+    Out << " = ";
+    NTTP->getDefaultArgument()->printPretty(Out, nullptr, Policy, Indentation);
+  }
+}

clang/unittests/AST/DeclPrinterTest.cpp

 // * additional helper declarations are 'Z', 'Y', 'X' and so on.
 //
 //===----------------------------------------------------------------------===//
 
 #include "clang/AST/ASTContext.h"
 #include "clang/ASTMatchers/ASTMatchFinder.h"
 #include "clang/Tooling/Tooling.h"
 #include "llvm/ADT/SmallString.h"
+#include "llvm/ADT/StringRef.h"
 #include "gtest/gtest.h"
 
 using namespace clang;
 using namespace ast_matchers;
 using namespace tooling;
 
 namespace {
 
ASSERT_TRUE(PrintedDeclCXX11Matches(
     "template<typename... T> struct X {"
     "  Z<sizeof...(T)> A;"
     "};",
     "A",
     "Z<sizeof...(T)> A"));
     // Should be: with semicolon
 }
 
+TEST(DeclPrinter, TestTemplateArgumentList16) {
+  llvm::StringLiteral Code = "template<typename T1, int NT1, typename T2 = "
+                             "bool, int NT2 = 5> struct Z {};";
+  ASSERT_TRUE(PrintedDeclCXX11Matches(Code, "T1", "typename T1"));
+  ASSERT_TRUE(PrintedDeclCXX11Matches(Code, "T2", "typename T2 = bool"));
+  ASSERT_TRUE(PrintedDeclCXX11Matches(Code, "NT1", "int NT1"));
+  ASSERT_TRUE(PrintedDeclCXX11Matches(Code, "NT2", "int NT2 = 5"));
+}
+
 TEST(DeclPrinter, TestStaticAssert1) {
   ASSERT_TRUE(PrintedDeclCXX1ZMatches(
     "static_assert(true);",
     staticAssertDecl().bind("id"),
     "static_assert(true)"));
 }
 
 TEST(DeclPrinter, TestObjCMethod1) {