[clang] [clang] correct argument offset for function template partial ordering (PR #107972)

[Matheus Izvekov via cfe-commits]

https://github.com/mizvekov created https://github.com/llvm/llvm-project/pull/107972

This fixes a bug in #18291, that was reported in the PR.

Since this is a bug fix for a patch that was never released, no entries are added to the changelog.

>From 395ddd73b4dd366155a8718c13410b03bf8c6d32 Mon Sep 17 00:00:00 2001
From: Matheus Izvekov <mizvekov at gmail.com>
Date: Tue, 10 Sep 2024 02:02:20 -0300
Subject: [PATCH] [clang] correct argument offset for function template partial
 ordering

This fixes a bug in #18291, that was reported in the PR.

Since this is a bug fix for a patch that was never released, no
entries are added to the changelog.
---
 clang/lib/Sema/SemaTemplateDeduction.cpp | 28 ++++++++++++------------
 clang/test/SemaTemplate/GH18291.cpp      | 27 ++++++++++++++++++++++-
 2 files changed, 40 insertions(+), 15 deletions(-)

diff --git a/clang/lib/Sema/SemaTemplateDeduction.cpp b/clang/lib/Sema/SemaTemplateDeduction.cpp
index 4c88159ea4cedf..562c57a41299a9 100644
--- a/clang/lib/Sema/SemaTemplateDeduction.cpp
+++ b/clang/lib/Sema/SemaTemplateDeduction.cpp
@@ -5502,10 +5502,6 @@ static TemplateDeductionResult CheckDeductionConsistency(
     ArrayRef<TemplateArgument> DeducedArgs, bool CheckConsistency) {
   MultiLevelTemplateArgumentList MLTAL(FTD, DeducedArgs,
                                        /*Final=*/true);
-  if (ArgIdx != -1)
-    if (auto *MD = dyn_cast<CXXMethodDecl>(FTD->getTemplatedDecl());
-        MD && MD->isImplicitObjectMemberFunction())
-      ArgIdx -= 1;
   Sema::ArgumentPackSubstitutionIndexRAII PackIndex(
       S, ArgIdx != -1 ? ::getPackIndexForParam(S, FTD, MLTAL, ArgIdx) : -1);
   bool IsIncompleteSubstitution = false;
@@ -5576,12 +5572,10 @@ static TemplateDeductionResult FinishTemplateArgumentDeduction(
 
 /// Determine whether the function template \p FT1 is at least as
 /// specialized as \p FT2.
-static bool isAtLeastAsSpecializedAs(Sema &S, SourceLocation Loc,
-                                     FunctionTemplateDecl *FT1,
-                                     FunctionTemplateDecl *FT2,
-                                     TemplatePartialOrderingContext TPOC,
-                                     ArrayRef<QualType> Args1,
-                                     ArrayRef<QualType> Args2) {
+static bool isAtLeastAsSpecializedAs(
+    Sema &S, SourceLocation Loc, FunctionTemplateDecl *FT1,
+    FunctionTemplateDecl *FT2, TemplatePartialOrderingContext TPOC,
+    ArrayRef<QualType> Args1, ArrayRef<QualType> Args2, bool Args1Offset) {
   FunctionDecl *FD1 = FT1->getTemplatedDecl();
   FunctionDecl *FD2 = FT2->getTemplatedDecl();
   const FunctionProtoType *Proto1 = FD1->getType()->getAs<FunctionProtoType>();
@@ -5676,6 +5670,8 @@ static bool isAtLeastAsSpecializedAs(Sema &S, SourceLocation Loc,
                       TemplateDeductionInfo &Info,
                       SmallVectorImpl<DeducedTemplateArgument> &Deduced,
                       PartialOrderingKind) {
+                    if (ArgIdx != -1)
+                      ArgIdx -= Args1Offset;
                     return ::CheckDeductionConsistency(
                         S, FTD, ArgIdx, P, A, DeducedArgs,
                         /*CheckConsistency=*/HasDeducedParam[ParamIdx]);
@@ -5763,6 +5759,8 @@ FunctionTemplateDecl *Sema::getMoreSpecializedTemplate(
   const FunctionDecl *FD2 = FT2->getTemplatedDecl();
   bool ShouldConvert1 = false;
   bool ShouldConvert2 = false;
+  bool Args1Offset = false;
+  bool Args2Offset = false;
   QualType Obj1Ty;
   QualType Obj2Ty;
   if (TPOC == TPOC_Call) {
@@ -5811,6 +5809,7 @@ FunctionTemplateDecl *Sema::getMoreSpecializedTemplate(
         Obj1Ty = GetImplicitObjectParameterType(this->Context, Method1,
                                                 RawObj1Ty, IsRValRef2);
         Args1.push_back(Obj1Ty);
+        Args1Offset = true;
       }
       if (ShouldConvert2) {
         bool IsRValRef1 =
@@ -5821,6 +5820,7 @@ FunctionTemplateDecl *Sema::getMoreSpecializedTemplate(
         Obj2Ty = GetImplicitObjectParameterType(this->Context, Method2,
                                                 RawObj2Ty, IsRValRef1);
         Args2.push_back(Obj2Ty);
+        Args2Offset = true;
       }
     } else {
       if (NonStaticMethod1 && Method1->hasCXXExplicitFunctionObjectParameter())
@@ -5842,10 +5842,10 @@ FunctionTemplateDecl *Sema::getMoreSpecializedTemplate(
   } else {
     assert(!Reversed && "Only call context could have reversed arguments");
   }
-  bool Better1 =
-      isAtLeastAsSpecializedAs(*this, Loc, FT1, FT2, TPOC, Args1, Args2);
-  bool Better2 =
-      isAtLeastAsSpecializedAs(*this, Loc, FT2, FT1, TPOC, Args2, Args1);
+  bool Better1 = isAtLeastAsSpecializedAs(*this, Loc, FT1, FT2, TPOC, Args1,
+                                          Args2, Args2Offset);
+  bool Better2 = isAtLeastAsSpecializedAs(*this, Loc, FT2, FT1, TPOC, Args2,
+                                          Args1, Args1Offset);
   // C++ [temp.deduct.partial]p10:
   //   F is more specialized than G if F is at least as specialized as G and G
   //   is not at least as specialized as F.
diff --git a/clang/test/SemaTemplate/GH18291.cpp b/clang/test/SemaTemplate/GH18291.cpp
index ca1e69e4ca3f53..820564ffa6f1a0 100644
--- a/clang/test/SemaTemplate/GH18291.cpp
+++ b/clang/test/SemaTemplate/GH18291.cpp
@@ -86,4 +86,29 @@ namespace func_pointer {
     template <class _Tp> void pow(_Tp, complex<typename __promote<_Tp>::type>) = delete;
     void (*ptr)(const complex<float> &, complex<float>){pow};
   } // namespace param
-} // namespace t3
+} // namespace func_pointer
+
+namespace static_vs_nonstatic {
+  namespace implicit_obj_param {
+    struct A {
+      template <class... Args>
+        static void f(int a, Args... args) {}
+      template <class... Args>
+        void f(Args... args) = delete;
+    };
+    void g(){
+      A::f(0);
+    }
+  } // namespace implicit_obj_param
+  namespace explicit_obj_param {
+    struct A {
+      template <class... Args>
+        static void f(int, Args... args) {}
+      template <class... Args>
+        void f(this A *, Args... args) = delete;
+    };
+    void g(){
+      A::f(0);
+    }
+  } // namespace explicit_obj_param
+} // namespace static_vs_nonstatic