[Clang] Ensure correct parameters are in the scope for constraint equivalence checking

[zyn0217]

This is another case where untransformed constraint expressions led to inconsistent transforms.

We did fix some of those issues by looking at parent scopes, however the parent instantiation scope is not always available because we could also reach here after the parents get instantiated.

Fixes #146614

[llvmbot]

@llvm/pr-subscribers-clang

Author: Younan Zhang (zyn0217)

Changes

This is another case where untransformed constraint expressions led to inconsistent transforms.

We did fix some of those issues by looking at parent scopes, however the parent instantiation scope is not always available because we could also reach here after the parents get instantiated.

Fixes #146614

---

Full diff: https://github.com/llvm/llvm-project/pull/149264.diff

3 Files Affected:

• (modified) clang/docs/ReleaseNotes.rst (+1)
• (modified) clang/lib/Sema/SemaConcept.cpp (+4-1)
• (modified) clang/test/SemaTemplate/concepts-using-decl.cpp (+21)

diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index fcd3887ec7a09..6f55d14fd0aa5 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -808,6 +808,7 @@ Bug Fixes in This Version
   nested scopes. (#GH147495)
 - Fixed a failed assertion with an operator call expression which comes from a
   macro expansion when performing analysis for nullability attributes. (#GH138371)
+- Fixed a concept equivalent checking crash due to untransformed constraint expressions. (#GH146614)
 
 Bug Fixes to Compiler Builtins
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
diff --git a/clang/lib/Sema/SemaConcept.cpp b/clang/lib/Sema/SemaConcept.cpp
index 834417f8e15ac..fbb2b8e650630 100644
--- a/clang/lib/Sema/SemaConcept.cpp
+++ b/clang/lib/Sema/SemaConcept.cpp
@@ -923,8 +923,11 @@ static const Expr *SubstituteConstraintExpressionWithoutSatisfaction(
   std::optional<LocalInstantiationScope> ScopeForParameters;
   if (const NamedDecl *ND = DeclInfo.getDecl();
       ND && ND->isFunctionOrFunctionTemplate()) {
-    ScopeForParameters.emplace(S, /*CombineWithOuterScope=*/true);
+    ScopeForParameters.emplace(S);
     const FunctionDecl *FD = ND->getAsFunction();
+    if (FunctionTemplateDecl *Template = FD->getDescribedFunctionTemplate();
+        Template && Template->getInstantiatedFromMemberTemplate())
+      FD = Template->getInstantiatedFromMemberTemplate()->getTemplatedDecl();
     for (auto *PVD : FD->parameters()) {
       if (!PVD->isParameterPack()) {
         ScopeForParameters->InstantiatedLocal(PVD, PVD);
diff --git a/clang/test/SemaTemplate/concepts-using-decl.cpp b/clang/test/SemaTemplate/concepts-using-decl.cpp
index fca69dea5c88f..41f7b6d2f8faa 100644
--- a/clang/test/SemaTemplate/concepts-using-decl.cpp
+++ b/clang/test/SemaTemplate/concepts-using-decl.cpp
@@ -176,3 +176,24 @@ void func() {
   f.foo<10, 10>(); // expected-error {{no matching member function for call to 'foo'}}
 }
 } // namespace heads_without_concepts.
+
+namespace GH146614 {
+
+template <typename T>
+struct base {
+    template <typename A>
+    void foo(A x)
+        requires (requires{x;})
+    {}
+};
+
+
+struct child : base<int> {
+  using base<int>::foo;
+  template <typename A>
+  void foo(A x)
+      requires (false)
+  {}
+};
+
+}

[cor3ntin]

LGTM