[clang] [Clang] Fix deduction of explicit object member functions (PR #140030)

[via cfe-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang

Author: cor3ntin (cor3ntin)

<details>
<summary>Changes</summary>

When taking the address of an overload set containing an explicit object member, we should not take the
explicit object parameter into account.

---
Full diff: https://github.com/llvm/llvm-project/pull/140030.diff


5 Files Affected:

- (modified) clang/docs/ReleaseNotes.rst (+1) 
- (modified) clang/include/clang/Sema/Sema.h (+1) 
- (modified) clang/lib/Sema/SemaOverload.cpp (+4) 
- (modified) clang/lib/Sema/SemaTemplateDeduction.cpp (+10-1) 
- (modified) clang/test/SemaCXX/cxx2b-deducing-this.cpp (+27) 


``````````diff
diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 31c517338c21f..1f17bc6e5c8e3 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -710,6 +710,7 @@ Bug Fixes to C++ Support
 - Clang now correctly parses arbitrary order of ``[[]]``, ``__attribute__`` and ``alignas`` attributes for declarations (#GH133107)
 - Fixed a crash when forming an invalid function type in a dependent context. (#GH138657) (#GH115725) (#GH68852)
 - Clang no longer segfaults when there is a configuration mismatch between modules and their users (http://crbug.com/400353616).
+- Fix an incorrect deduction when calling an explicit object member function template through an overload set address.
 
 Bug Fixes to AST Handling
 ^^^^^^^^^^^^^^^^^^^^^^^^^
diff --git a/clang/include/clang/Sema/Sema.h b/clang/include/clang/Sema/Sema.h
index 6ea7ee281e14d..5ec67087aeea4 100644
--- a/clang/include/clang/Sema/Sema.h
+++ b/clang/include/clang/Sema/Sema.h
@@ -12576,6 +12576,7 @@ class Sema final : public SemaBase {
       bool PartialOverloading, bool AggregateDeductionCandidate,
       bool PartialOrdering, QualType ObjectType,
       Expr::Classification ObjectClassification,
+      bool ForOverloadSetAddressResolution,
       llvm::function_ref<bool(ArrayRef<QualType>)> CheckNonDependent);
 
   /// Deduce template arguments when taking the address of a function
diff --git a/clang/lib/Sema/SemaOverload.cpp b/clang/lib/Sema/SemaOverload.cpp
index e20a41c10ccaa..23304e12f8c31 100644
--- a/clang/lib/Sema/SemaOverload.cpp
+++ b/clang/lib/Sema/SemaOverload.cpp
@@ -7846,6 +7846,8 @@ static void AddMethodTemplateCandidateImmediately(
           MethodTmpl, ExplicitTemplateArgs, Args, Specialization, Info,
           PartialOverloading, /*AggregateDeductionCandidate=*/false,
           /*PartialOrdering=*/false, ObjectType, ObjectClassification,
+          CandidateSet.getKind() ==
+              clang::OverloadCandidateSet::CSK_AddressOfOverloadSet,
           [&](ArrayRef<QualType> ParamTypes) {
             return S.CheckNonDependentConversions(
                 MethodTmpl, ParamTypes, Args, CandidateSet, Conversions,
@@ -7960,6 +7962,8 @@ static void AddTemplateOverloadCandidateImmediately(
           /*PartialOrdering=*/false,
           /*ObjectType=*/QualType(),
           /*ObjectClassification=*/Expr::Classification(),
+          CandidateSet.getKind() ==
+              OverloadCandidateSet::CSK_AddressOfOverloadSet,
           [&](ArrayRef<QualType> ParamTypes) {
             return S.CheckNonDependentConversions(
                 FunctionTemplate, ParamTypes, Args, CandidateSet, Conversions,
diff --git a/clang/lib/Sema/SemaTemplateDeduction.cpp b/clang/lib/Sema/SemaTemplateDeduction.cpp
index 5dc06ebc2a235..217d57d67f067 100644
--- a/clang/lib/Sema/SemaTemplateDeduction.cpp
+++ b/clang/lib/Sema/SemaTemplateDeduction.cpp
@@ -4432,6 +4432,7 @@ TemplateDeductionResult Sema::DeduceTemplateArguments(
     bool PartialOverloading, bool AggregateDeductionCandidate,
     bool PartialOrdering, QualType ObjectType,
     Expr::Classification ObjectClassification,
+    bool ForOverloadSetAddressResolution,
     llvm::function_ref<bool(ArrayRef<QualType>)> CheckNonDependent) {
   if (FunctionTemplate->isInvalidDecl())
     return TemplateDeductionResult::Invalid;
@@ -4440,7 +4441,15 @@ TemplateDeductionResult Sema::DeduceTemplateArguments(
   unsigned NumParams = Function->getNumParams();
   bool HasExplicitObject = false;
   int ExplicitObjectOffset = 0;
-  if (Function->hasCXXExplicitFunctionObjectParameter()) {
+
+  // [C++26] [over.call.func]p3
+  // If the primary-expression is the address of an overload set,
+  // the argument list is the same as the expression-list in the call.
+  // Otherwise, the argument list is the expression-list in the call augmented
+  // by the addition of an implied object argument as in a qualified function
+  // call.
+  if (!ForOverloadSetAddressResolution &&
+      Function->hasCXXExplicitFunctionObjectParameter()) {
     HasExplicitObject = true;
     ExplicitObjectOffset = 1;
   }
diff --git a/clang/test/SemaCXX/cxx2b-deducing-this.cpp b/clang/test/SemaCXX/cxx2b-deducing-this.cpp
index 7e392213710a4..2286da8d1c0e5 100644
--- a/clang/test/SemaCXX/cxx2b-deducing-this.cpp
+++ b/clang/test/SemaCXX/cxx2b-deducing-this.cpp
@@ -926,6 +926,33 @@ struct C {
     (&fref)();
   }
 };
+
+struct CTpl {
+  template <typename T>
+  constexpr int c(this const CTpl&, T) {  // #P2797-ctpl-1
+      return 42;
+  }
+
+  template <typename T>
+  void c(T)&; // #P2797-ctpl-2
+
+  template <typename T>
+  static void c(T = 0, T = 0);  // #P2797-ctpl-3
+
+  void d() {
+    c(0);               // expected-error {{call to member function 'c' is ambiguous}}
+                        // expected-note@#P2797-ctpl-1{{candidate}}
+                        // expected-note@#P2797-ctpl-2{{candidate}}
+                        // expected-note@#P2797-ctpl-3{{candidate}}
+    (CTpl::c)(0);       // expected-error {{call to member function 'c' is ambiguous}}
+                        // expected-note@#P2797-ctpl-1{{candidate}}
+                        // expected-note@#P2797-ctpl-2{{candidate}}
+                        // expected-note@#P2797-ctpl-3{{candidate}}
+
+    static_assert((&CTpl::c)(CTpl{}, 0) == 42); // selects #1
+  }
+};
+
 }
 
 namespace GH85992 {

``````````

</details>


https://github.com/llvm/llvm-project/pull/140030