From 6e6aa44c7d14b37a12e40c6b36478045d6004a0a Mon Sep 17 00:00:00 2001
From: Erich Keane <ekeane@nvidia.com>
Date: Wed, 31 Jan 2024 06:58:58 -0800
Subject: [PATCH] =?UTF-8?q?Revert=20"[Clang][Sema]=20fix=20outline=20membe?=
 =?UTF-8?q?r=20function=20template=20with=20defau=E2=80=A6=20(#80144)?=
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…lt align crash (#78400)"

This reverts commit 7b3389980ddbd84f72ccc4776889c67519cc2c14.

A regression was discovered here:
https://github.com/llvm/llvm-project/pull/78400

and the author requested a revert to give time to review.
---
 clang/docs/ReleaseNotes.rst                   |  4 --
 clang/lib/Sema/SemaTemplateInstantiate.cpp    | 13 +----
 clang/test/SemaTemplate/default-parm-init.cpp | 50 -------------------
 3 files changed, 2 insertions(+), 65 deletions(-)
 delete mode 100644 clang/test/SemaTemplate/default-parm-init.cpp

diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 37f2423441a30c..2fa2bab867d033 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/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>`_)
diff --git a/clang/lib/Sema/SemaTemplateInstantiate.cpp b/clang/lib/Sema/SemaTemplateInstantiate.cpp
index 41e58b91de4e08..e12186d7d82f8d 100644
--- a/clang/lib/Sema/SemaTemplateInstantiate.cpp
+++ b/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())
diff --git a/clang/test/SemaTemplate/default-parm-init.cpp b/clang/test/SemaTemplate/default-parm-init.cpp
deleted file mode 100644
index 4bcea7eaa10176..00000000000000
--- a/clang/test/SemaTemplate/default-parm-init.cpp
+++ /dev/null
@@ -1,50 +0,0 @@
-// RUN: %clang_cc1 -fsyntax-only -std=c++17 -verify %s
-// RUN: %clang_cc1 -fsyntax-only -std=c++20 -verify %s
-// expected-no-diagnostics
-
-template<typename TemplateParam>
-struct Problem{
-  template<typename FunctionTemplateParam>
-  constexpr int FuncAlign(int param = alignof(FunctionTemplateParam));
-
-  template<typename FunctionTemplateParam>
-  constexpr int FuncSizeof(int param = sizeof(FunctionTemplateParam));
-
-  template<typename FunctionTemplateParam>
-  constexpr int FuncAlign2(int param = alignof(TemplateParam));
-
-  template<typename FunctionTemplateParam>
-  constexpr int FuncSizeof2(int param = sizeof(TemplateParam));
-};
-
-template <>
-template<typename FunctionTemplateParam>
-constexpr int Problem<int>::FuncAlign(int param) {
-	return param;
-}
-
-template <>
-template<typename FunctionTemplateParam>
-constexpr int Problem<int>::FuncSizeof(int param) {
-	return param;
-}
-
-template <>
-template<typename FunctionTemplateParam>
-constexpr int Problem<int>::FuncAlign2(int param) {
-	return param;
-}
-
-template <>
-template<typename FunctionTemplateParam>
-constexpr int Problem<int>::FuncSizeof2(int param) {
-	return param;
-}
-
-int main(){
-    Problem<int> p = {};
-    static_assert(p.FuncAlign<char>() == alignof(char));
-    static_assert(p.FuncSizeof<char>() == sizeof(char));
-    static_assert(p.FuncAlign2<char>() == alignof(int));
-    static_assert(p.FuncSizeof2<char>() == sizeof(int));
-}