From 15f0491d3963d91202aef659acc20f59aa83fae7 Mon Sep 17 00:00:00 2001
From: Erich Keane <erich.keane@intel.com>
Date: Fri, 28 Apr 2023 09:54:28 -0700
Subject: [PATCH] [NFC] Fix a mem-sanitizer found issue in AutoType

We only need the list of constriant template arguments when we have a
valid constraint.  We give up on merging the auto-type constraints if
the template arguments don't match, but neglected to clear the
collection of template arguments.  The result was we had an AutoType
where we initialized the number of template arguments, but never
initialized the template arguments themselves.

This patch adds an assert to catch this in the future, plus ensures we
clear out the vector so we don't try to create the AutoType incorrectly.
---
 clang/lib/AST/ASTContext.cpp | 4 +++-
 clang/lib/AST/Type.cpp       | 1 +
 2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/clang/lib/AST/ASTContext.cpp b/clang/lib/AST/ASTContext.cpp
index e331df8..6bc202e 100644
--- a/clang/lib/AST/ASTContext.cpp
+++ b/clang/lib/AST/ASTContext.cpp
@@ -12982,8 +12982,10 @@ static QualType getCommonSugarTypeNode(ASTContext &Ctx, const Type *X,
     SmallVector<TemplateArgument, 8> As;
     if (CD &&
         getCommonTemplateArguments(Ctx, As, AX->getTypeConstraintArguments(),
-                                   AY->getTypeConstraintArguments()))
+                                   AY->getTypeConstraintArguments())) {
       CD = nullptr; // The arguments differ, so make it unconstrained.
+      As.clear();
+    }
 
     // Both auto types can't be dependent, otherwise they wouldn't have been
     // sugar. This implies they can't contain unexpanded packs either.
diff --git a/clang/lib/AST/Type.cpp b/clang/lib/AST/Type.cpp
index e1686a7..c0d2250 100644
--- a/clang/lib/AST/Type.cpp
+++ b/clang/lib/AST/Type.cpp
@@ -4630,6 +4630,7 @@ AutoType::AutoType(QualType DeducedAsType, AutoTypeKeyword Keyword,
   AutoTypeBits.Keyword = (unsigned)Keyword;
   AutoTypeBits.NumArgs = TypeConstraintArgs.size();
   this->TypeConstraintConcept = TypeConstraintConcept;
+  assert(TypeConstraintConcept || AutoTypeBits.NumArgs == 0);
   if (TypeConstraintConcept) {
     auto *ArgBuffer =
         const_cast<TemplateArgument *>(getTypeConstraintArguments().data());
-- 
2.7.4