[clang][TypePrinter] Test TemplateArgument::IsDefaulted when omitting default arguments

[Michael137]

Summary

Summary

This patch allows clients who can't properly construct
a ClassTemplateDecl to still benefit from the clang::TypePrinters
ability to skip printing defaulted template arguments. The
clients simply have to call TemplateArgument::setIsDefaulted
in advance.

See discussion in https://reviews.llvm.org/D140423

[Michael137]

• Rebase

[Michael137]

This caused some LLDB test failures for the import-std-module setting. https://green.lab.llvm.org/green/view/LLDB/job/lldb-cmake/

We construct TemplateArguments manually in the CxxModuleHandler. Fix is in-flight.

clang/lib/AST/TypePrinter.cpp

 template <typename TA>
 static void
 printTo(raw_ostream &OS, ArrayRef<TA> Args, const PrintingPolicy &Policy,
         const TemplateParameterList *TPL, bool IsPack, unsigned ParmIndex) {
   // Drop trailing template arguments that match default arguments.
   if (TPL && Policy.SuppressDefaultTemplateArgs &&
       !Policy.PrintCanonicalTypes && !Args.empty() && !IsPack &&
       Args.size() <= TPL->size()) {
-    ASTContext &Ctx = TPL->getParam(0)->getASTContext();
     llvm::SmallVector<TemplateArgument, 8> OrigArgs;
     for (const TA &A : Args)
       OrigArgs.push_back(getArgument(A));
-    while (!Args.empty() &&
-           isSubstitutedDefaultArgument(Ctx, getArgument(Args.back()),
-                                        TPL->getParam(Args.size() - 1),
-                                        OrigArgs, TPL->getDepth()))
+    while (!Args.empty() && getArgument(Args.back()).getIsDefaulted())
       Args = Args.drop_back();
   }
 
   const char *Comma = Policy.MSVCFormatting ? "," : ", ";
   if (!IsPack)
     OS << '<';
 
   bool NeedSpace = false;