[clang] concepts: perform parameter mapping subsitution in correct context

Prior to this patch, during constraint normalization we could
forget from which declaration an atomic constraint was normalized
from.

Subsequently when performing parameter mapping substitution for
that atomic constraint with an incorrect context, we couldn't
correctly recognize which declarations are supposed to be visible.

Fixes #60336

Author: mizvekov

clang/docs/ReleaseNotes.rst

@@ -179,6 +179,9 @@ Bug Fixes to C++ Support
   with a string literal. (#GH82167)
 - Fix a crash when matching template template parameters with templates which have
   parameters of different class type. (#GH101394)
+- Clang now correctly recognizes the correct context for parameter
+  substitutions in concepts, so it doesn't incorrectly complain of missing
+  module imports in those situations. (#GH60336)
 
 Bug Fixes to AST Handling
 ^^^^^^^^^^^^^^^^^^^^^^^^^

clang/include/clang/Sema/SemaConcept.h

@@ -30,10 +30,11 @@ enum { ConstraintAlignment = 8 };
 
 struct alignas(ConstraintAlignment) AtomicConstraint {
   const Expr *ConstraintExpr;
+  NamedDecl *ConstraintDecl;
   std::optional<ArrayRef<TemplateArgumentLoc>> ParameterMapping;
 
-  AtomicConstraint(Sema &S, const Expr *ConstraintExpr) :
-      ConstraintExpr(ConstraintExpr) { };
+  AtomicConstraint(const Expr *ConstraintExpr, NamedDecl *ConstraintDecl)
+      : ConstraintExpr(ConstraintExpr), ConstraintDecl(ConstraintDecl) {};
 
   bool hasMatchingParameterMapping(ASTContext &C,
                                    const AtomicConstraint &Other) const {

clang/lib/Sema/SemaConcept.cpp

@@ -1457,8 +1457,8 @@ substituteParameterMappings(Sema &S, NormalizedConstraint &N,
           : ArgsAsWritten->arguments().front().getSourceRange().getEnd();
   Sema::InstantiatingTemplate Inst(
       S, InstLocBegin,
-      Sema::InstantiatingTemplate::ParameterMappingSubstitution{}, Concept,
-      {InstLocBegin, InstLocEnd});
+      Sema::InstantiatingTemplate::ParameterMappingSubstitution{},
+      Atomic.ConstraintDecl, {InstLocBegin, InstLocEnd});
   if (Inst.isInvalid())
     return true;
   if (S.SubstTemplateArguments(*Atomic.ParameterMapping, MLTAL, SubstArgs))
@@ -1632,7 +1632,7 @@ NormalizedConstraint::fromConstraintExpr(Sema &S, NamedDecl *D, const Expr *E) {
         Kind, std::move(*Sub), FE->getPattern()}};
   }
 
-  return NormalizedConstraint{new (S.Context) AtomicConstraint(S, E)};
+  return NormalizedConstraint{new (S.Context) AtomicConstraint(E, D)};
 }
 
 bool FoldExpandedConstraint::AreCompatibleForSubsumption(

clang/test/Modules/GH60336-2.cpp

@@ -0,0 +1,44 @@
+// RUN: rm -rf %t
+// RUN: %clang_cc1 -x c++ -std=c++20 %s -verify -fmodules -fmodules-cache-path=%t
+// expected-no-diagnostics
+
+#pragma clang module build std
+module std {
+  module concepts {}
+  module functional {}
+}
+#pragma clang module contents
+#pragma clang module begin std
+
+template <class _Tp> struct common_reference {
+  using type = _Tp;
+};
+
+#pragma clang module end
+#pragma clang module begin std.concepts
+#pragma clang module import std
+
+template <class _Tp>
+concept same_as = __is_same(_Tp, _Tp);
+
+template <class _Tp>
+concept common_reference_with =
+    same_as<typename common_reference<_Tp>::type>;
+
+#pragma clang module end
+#pragma clang module begin std.functional
+#pragma clang module import std.concepts
+
+template <class, class _Ip>
+concept sentinel_for = common_reference_with<_Ip>;
+
+constexpr bool ntsf_subsumes_sf(sentinel_for<char *> auto)
+  requires true
+{
+  return true;
+}
+bool ntsf_subsumes_sf(sentinel_for<char *> auto);
+static_assert(ntsf_subsumes_sf(""));
+
+#pragma clang module end
+#pragma clang module endbuild

clang/test/Modules/GH60336.cpp

@@ -1,5 +1,7 @@
 // RUN: rm -rf %t
 // RUN: %clang_cc1 -x c++ -std=c++20 %s -verify -fmodules -fmodules-cache-path=%t
+// expected-no-diagnostics
+
 #pragma clang module build std
 module std   [system] {
   module concepts     [system] {
@@ -65,14 +67,3 @@ constexpr bool ntsf_subsumes_sf(std::nothrow_sentinel_for<char*> auto) requires
 }
 constexpr bool ntsf_subsumes_sf(std::sentinel_for<char*> auto);
 static_assert(ntsf_subsumes_sf("foo"));
-
-// Note: Doing diagnostics verify lines in the individual modules isn't
-// permitted, and using 'bookmarks' in a module also doesn't work, so we're 
-// forced to diagnose this by line-number.
-//
-// Check to ensure that this error happens, prior to a revert of a concepts
-// sugaring patch, this diagnostic didn't happen correctly.
-
-// expected-error@* {{partial specialization of 'common_reference<_Tp, _Up>' must be imported from module 'std.type_traits' before it is required}}
-// expected-note@63 {{while substituting into concept arguments here}}
-// expected-note@*{{partial specialization declared here is not reachable}}