[clang] 04d20b1 - [concepts] Set up an instantiation scope for constraint expression comparison (#79698)

[via cfe-commits]

Author: Younan Zhang
Date: 2024-01-30T19:34:52+08:00
New Revision: 04d20b17050203e07394b4f9ee61b5affe2d5347

URL: https://github.com/llvm/llvm-project/commit/04d20b17050203e07394b4f9ee61b5affe2d5347
DIFF: https://github.com/llvm/llvm-project/commit/04d20b17050203e07394b4f9ee61b5affe2d5347.diff

LOG: [concepts] Set up an instantiation scope for constraint expression comparison (#79698)

This is a follow-up for the comparison of constraints on out-of-line
function template definitions. We require the instantiation of a
ParmVarDecl while transforming the expression if that Decl gets
referenced by a DeclRefExpr. However, we're not actually performing the
class or function template instantiation at the time of such comparison.
Therefore, let's map these parameters to themselves so that they get
preserved after the substitution.

Fixes https://github.com/llvm/llvm-project/issues/74447.

Added: 
    

Modified: 
    clang/docs/ReleaseNotes.rst
    clang/lib/Sema/SemaConcept.cpp
    clang/test/SemaTemplate/concepts-out-of-line-def.cpp

Removed: 
    


################################################################################
diff  --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index bac6c7162a45..f0dea0c9bc89 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -138,6 +138,9 @@ Bug Fixes to C++ Support
 - Fixed a bug where variables referenced by requires-clauses inside
   nested generic lambdas were not properly injected into the constraint scope.
   (`#73418 <https://github.com/llvm/llvm-project/issues/73418>`_)
+- Fixed a crash where substituting into a requires-expression that refers to function
+  parameters during the equivalence determination of two constraint expressions.
+  (`#74447 <https://github.com/llvm/llvm-project/issues/74447>`_)
 - Fixed deducing auto& from const int in template parameters of partial
   specializations.
   (`#77189 <https://github.com/llvm/llvm-project/issues/77189>`_)

diff  --git a/clang/lib/Sema/SemaConcept.cpp b/clang/lib/Sema/SemaConcept.cpp
index 88fc846c89e4..19a460f41175 100644
--- a/clang/lib/Sema/SemaConcept.cpp
+++ b/clang/lib/Sema/SemaConcept.cpp
@@ -797,6 +797,15 @@ static const Expr *SubstituteConstraintExpressionWithoutSatisfaction(
   if (Inst.isInvalid())
     return nullptr;
 
+  // Set up a dummy 'instantiation' scope in the case of reference to function
+  // parameters that the surrounding function hasn't been instantiated yet. Note
+  // this may happen while we're comparing two templates' constraint
+  // equivalence.
+  LocalInstantiationScope ScopeForParameters(S);
+  if (auto *FD = llvm::dyn_cast<FunctionDecl>(DeclInfo.getDecl()))
+    for (auto *PVD : FD->parameters())
+      ScopeForParameters.InstantiatedLocal(PVD, PVD);
+
   std::optional<Sema::CXXThisScopeRAII> ThisScope;
   if (auto *RD = dyn_cast<CXXRecordDecl>(DeclInfo.getDeclContext()))
     ThisScope.emplace(S, const_cast<CXXRecordDecl *>(RD), Qualifiers());

diff  --git a/clang/test/SemaTemplate/concepts-out-of-line-def.cpp b/clang/test/SemaTemplate/concepts-out-of-line-def.cpp
index c4e8e6f720c4..7323ad8d9ef2 100644
--- a/clang/test/SemaTemplate/concepts-out-of-line-def.cpp
+++ b/clang/test/SemaTemplate/concepts-out-of-line-def.cpp
@@ -536,3 +536,25 @@ void X<T>::bar(decltype(requires { requires something_interesting<T>; })) {}
 template <class T>
 void X<T>::bar(decltype(requires { requires is_not_same_v<T, int>; })) {}
 } // namespace GH74314
+
+namespace GH74447 {
+template <typename T> struct S {
+  template <typename... U, int V>
+  void test(T target, U... value)
+    requires requires {
+      target;
+      sizeof...(value) == 1;
+      V == 2;
+    };
+};
+
+template <typename T>
+template <typename... U, int V>
+void S<T>::test(T target, U... value)
+  requires requires {
+    target;
+    sizeof...(value) == 1;
+    V == 2;
+  }
+{}
+} // namespace GH74447