[clang] fix partial ordering of NTTP packs (#134461)

This fixes partial ordering of pack expansions of NTTPs, by procedding
with the check using the pattern of the NTTP through the rules of the
non-pack case.

This also unifies almost all of the different versions of
FinishTemplateArgumentDeduction (except the function template case).
This makes sure they all follow the rules consistently, instantiating
the parameters and comparing those with the argument.

Fixes #132562

Author: mizvekov

clang/docs/ReleaseNotes.rst

@@ -396,6 +396,7 @@ Bug Fixes to C++ Support
 - Improved fix for an issue with pack expansions of type constraints, where this
   now also works if the constraint has non-type or template template parameters.
   (#GH131798)
+- Fixes to partial ordering of non-type template parameter packs. (#GH132562)
 - Fix crash when evaluating the trailing requires clause of generic lambdas which are part of
   a pack expansion.
 - Fixes matching of nested template template parameters. (#GH130362)

clang/include/clang/AST/ExprCXX.h

@@ -4209,10 +4209,10 @@ class PackExpansionExpr : public Expr {
   Stmt *Pattern;
 
 public:
-  PackExpansionExpr(QualType T, Expr *Pattern, SourceLocation EllipsisLoc,
+  PackExpansionExpr(Expr *Pattern, SourceLocation EllipsisLoc,
                     UnsignedOrNone NumExpansions)
-      : Expr(PackExpansionExprClass, T, Pattern->getValueKind(),
-             Pattern->getObjectKind()),
+      : Expr(PackExpansionExprClass, Pattern->getType(),
+             Pattern->getValueKind(), Pattern->getObjectKind()),
         EllipsisLoc(EllipsisLoc),
         NumExpansions(NumExpansions ? *NumExpansions + 1 : 0),
         Pattern(Pattern) {

clang/include/clang/Sema/Sema.h

@@ -10127,13 +10127,14 @@ class Sema final : public SemaBase {
 
   /// Contexts in which a converted constant expression is required.
   enum CCEKind {
-    CCEK_CaseValue,    ///< Expression in a case label.
-    CCEK_Enumerator,   ///< Enumerator value with fixed underlying type.
-    CCEK_TemplateArg,  ///< Value of a non-type template parameter.
-    CCEK_InjectedTTP,  ///< Injected parameter of a template template parameter.
-    CCEK_ArrayBound,   ///< Array bound in array declarator or new-expression.
-    CCEK_ExplicitBool, ///< Condition in an explicit(bool) specifier.
-    CCEK_Noexcept,     ///< Condition in a noexcept(bool) specifier.
+    CCEK_CaseValue,     ///< Expression in a case label.
+    CCEK_Enumerator,    ///< Enumerator value with fixed underlying type.
+    CCEK_TemplateArg,   ///< Value of a non-type template parameter.
+    CCEK_TempArgStrict, ///< As above, but applies strict template checking
+                        ///< rules.
+    CCEK_ArrayBound,    ///< Array bound in array declarator or new-expression.
+    CCEK_ExplicitBool,  ///< Condition in an explicit(bool) specifier.
+    CCEK_Noexcept,      ///< Condition in a noexcept(bool) specifier.
     CCEK_StaticAssertMessageSize, ///< Call to size() in a static assert
                                   ///< message.
     CCEK_StaticAssertMessageData, ///< Call to data() in a static assert
@@ -11895,7 +11896,7 @@ class Sema final : public SemaBase {
                                    QualType InstantiatedParamType, Expr *Arg,
                                    TemplateArgument &SugaredConverted,
                                    TemplateArgument &CanonicalConverted,
-                                   bool MatchingTTP,
+                                   bool StrictCheck,
                                    CheckTemplateArgumentKind CTAK);
 
   /// Check a template argument against its corresponding

clang/lib/AST/ASTContext.cpp

@@ -5852,8 +5852,7 @@ TemplateArgument ASTContext::getInjectedTemplateArg(NamedDecl *Param) const {
                     T, VK, NTTP->getLocation());
 
     if (NTTP->isParameterPack())
-      E = new (*this)
-          PackExpansionExpr(DependentTy, E, NTTP->getLocation(), std::nullopt);
+      E = new (*this) PackExpansionExpr(E, NTTP->getLocation(), std::nullopt);
     Arg = TemplateArgument(E);
   } else {
     auto *TTP = cast<TemplateTemplateParmDecl>(Param);

clang/lib/AST/ASTImporter.cpp

@@ -8273,14 +8273,13 @@ ASTNodeImporter::VisitMaterializeTemporaryExpr(MaterializeTemporaryExpr *E) {
 
 ExpectedStmt ASTNodeImporter::VisitPackExpansionExpr(PackExpansionExpr *E) {
   Error Err = Error::success();
-  auto ToType = importChecked(Err, E->getType());
-  auto ToPattern = importChecked(Err, E->getPattern());
+  auto *ToPattern = importChecked(Err, E->getPattern());
   auto ToEllipsisLoc = importChecked(Err, E->getEllipsisLoc());
   if (Err)
     return std::move(Err);
 
-  return new (Importer.getToContext()) PackExpansionExpr(
-      ToType, ToPattern, ToEllipsisLoc, E->getNumExpansions());
+  return new (Importer.getToContext())
+      PackExpansionExpr(ToPattern, ToEllipsisLoc, E->getNumExpansions());
 }
 
 ExpectedStmt ASTNodeImporter::VisitSizeOfPackExpr(SizeOfPackExpr *E) {

clang/lib/Sema/SemaOverload.cpp

@@ -6201,7 +6201,7 @@ static ExprResult BuildConvertedConstantExpression(Sema &S, Expr *From,
                                                    Sema::CCEKind CCE,
                                                    NamedDecl *Dest,
                                                    APValue &PreNarrowingValue) {
-  assert((S.getLangOpts().CPlusPlus11 || CCE == Sema::CCEK_InjectedTTP) &&
+  assert((S.getLangOpts().CPlusPlus11 || CCE == Sema::CCEK_TempArgStrict) &&
          "converted constant expression outside C++11 or TTP matching");
 
   if (checkPlaceholderForOverload(S, From))
@@ -6272,7 +6272,7 @@ static ExprResult BuildConvertedConstantExpression(Sema &S, Expr *From,
   // class type.
   ExprResult Result;
   bool IsTemplateArgument =
-      CCE == Sema::CCEK_TemplateArg || CCE == Sema::CCEK_InjectedTTP;
+      CCE == Sema::CCEK_TemplateArg || CCE == Sema::CCEK_TempArgStrict;
   if (T->isRecordType()) {
     assert(IsTemplateArgument &&
            "unexpected class type converted constant expr");
@@ -6325,7 +6325,7 @@ static ExprResult BuildConvertedConstantExpression(Sema &S, Expr *From,
     // value-dependent so we can't tell whether it's actually narrowing.
     // For matching the parameters of a TTP, the conversion is ill-formed
     // if it may narrow.
-    if (CCE != Sema::CCEK_InjectedTTP)
+    if (CCE != Sema::CCEK_TempArgStrict)
       break;
     [[fallthrough]];
   case NK_Type_Narrowing:
@@ -6400,7 +6400,7 @@ Sema::EvaluateConvertedConstantExpression(Expr *E, QualType T, APValue &Value,
   Expr::EvalResult Eval;
   Eval.Diag = &Notes;
 
-  assert(CCE != Sema::CCEK_InjectedTTP && "unnexpected CCE Kind");
+  assert(CCE != Sema::CCEK_TempArgStrict && "unnexpected CCE Kind");
 
   ConstantExprKind Kind;
   if (CCE == Sema::CCEK_TemplateArg && T->isRecordType())