Revert "[Clang][Sema] fix outline member function template with defau… (

llvm#80144)

…lt align crash (llvm#78400)"

This reverts commit 7b33899.

A regression was discovered here:
llvm#78400

and the author requested a revert to give time to review.

clang/docs/ReleaseNotes.rst

@@ -164,10 +164,6 @@ Bug Fixes to C++ Support
 
 - Fix crash when using lifetimebound attribute in function with trailing return.
  Fixes (`#73619 <https://github.com/llvm/llvm-project/issues/73619>`_)
-- Fix a crash when specializing an out-of-line member function with a default
- parameter where we did an incorrect specialization of the initialization of
- the default parameter.
- Fixes (`#68490 <https://github.com/llvm/llvm-project/issues/68490>`_)
 - Addressed an issue where constraints involving injected class types are perceived
  distinct from its specialization types.
  (`#56482 <https://github.com/llvm/llvm-project/issues/56482>`_)

clang/lib/Sema/SemaTemplateInstantiate.cpp

@@ -3049,7 +3049,6 @@ bool Sema::SubstDefaultArgument(
  // default argument expression appears.
  ContextRAII SavedContext(*this, FD);
  std::unique_ptr<LocalInstantiationScope> LIS;
- MultiLevelTemplateArgumentList NewTemplateArgs = TemplateArgs;
 
  if (ForCallExpr) {
  // When instantiating a default argument due to use in a call expression,
@@ -3062,19 +3061,11 @@ bool Sema::SubstDefaultArgument(
  /*ForDefinition*/ false);
  if (addInstantiatedParametersToScope(FD, PatternFD, *LIS, TemplateArgs))
  return true;
- if (FD->isOutOfLine()) {
- TemplateArgumentList *CurrentTemplateArgumentList =
- TemplateArgumentList::CreateCopy(getASTContext(),
- TemplateArgs.getInnermost());
- NewTemplateArgs = getTemplateInstantiationArgs(
- FD, FD->getDeclContext(), /*Final=*/false,
- CurrentTemplateArgumentList, /*RelativeToPrimary=*/true);
- }
  }
 
  runWithSufficientStackSpace(Loc, [&] {
- Result = SubstInitializer(PatternExpr, NewTemplateArgs,
- /*DirectInit*/ false);
+ Result = SubstInitializer(PatternExpr, TemplateArgs,
+ /*DirectInit*/false);
  });
  }
  if (Result.isInvalid())