[Clang] Substitute non dependent concepts in constraints

clang/include/clang/Sema/Sema.h

@@ -13385,6 +13385,13 @@ class Sema final : public SemaBase {
                          const MultiLevelTemplateArgumentList &TemplateArgs,
                          TemplateArgumentListInfo &Outputs);
 
+  /// Substitute concept template arguments in the constraint expression
+  /// of a concept-id. This is used to implement [temp.constr.normal].
+  ExprResult
+  SubstConceptTemplateArguments(const ConceptSpecializationExpr *CSE,
+                                const Expr *ConstraintExpr,
+                                const MultiLevelTemplateArgumentList &MLTAL);
+
   bool SubstTemplateArgumentsInParameterMapping(
       ArrayRef<TemplateArgumentLoc> Args, SourceLocation BaseLoc,
       const MultiLevelTemplateArgumentList &TemplateArgs,

clang/lib/AST/TemplateBase.cpp

@@ -340,13 +340,14 @@ bool TemplateArgument::isPackExpansion() const {
 }
 
 bool TemplateArgument::isConceptOrConceptTemplateParameter() const {
-  if (getKind() == TemplateArgument::Template) {
-    if (isa<ConceptDecl>(getAsTemplate().getAsTemplateDecl()))
-      return true;
-    else if (auto *TTP = dyn_cast_if_present<TemplateTemplateParmDecl>(
-                 getAsTemplate().getAsTemplateDecl()))
-      return TTP->templateParameterKind() == TNK_Concept_template;
-  }
+  if (getKind() != TemplateArgument::Template)
+    return false;
+
+  if (isa_and_nonnull<ConceptDecl>(getAsTemplate().getAsTemplateDecl()))
+    return true;
+  if (auto *TTP = llvm::dyn_cast_or_null<TemplateTemplateParmDecl>(
+          getAsTemplate().getAsTemplateDecl()))
+    return TTP->templateParameterKind() == TNK_Concept_template;
   return false;
 }
 

clang/lib/Sema/SemaConcept.cpp

@@ -1217,10 +1217,48 @@ bool Sema::CheckConstraintSatisfaction(
   return false;
 }
 
+static const ExprResult
+SubstituteConceptsInConstrainExpression(Sema &S, const NamedDecl *D,
+                                        const ConceptSpecializationExpr *CSE,
+                                        UnsignedOrNone SubstIndex) {
+
+  // [C++2c] [temp.constr.normal]
+  // Otherwise, to form CE, any non-dependent concept template argument Ai
+  // is substituted into the constraint-expression of C.
+  // If any such substitution results in an invalid concept-id,
+  // the program is ill-formed; no diagnostic is required.
+
+  ConceptDecl *Concept = CSE->getNamedConcept()->getCanonicalDecl();
+  Sema::ArgPackSubstIndexRAII _(S, SubstIndex);
+
+  const auto *ArgsAsWritten = CSE->getTemplateArgsAsWritten();
+  if (llvm::none_of(
+          ArgsAsWritten->arguments(), [&](const TemplateArgumentLoc &ArgLoc) {
+            return !ArgLoc.getArgument().isDependent() &&
+                   ArgLoc.getArgument().isConceptOrConceptTemplateParameter();
+          })) {
+    return Concept->getConstraintExpr();
+  }
+
+  MultiLevelTemplateArgumentList MLTAL = S.getTemplateInstantiationArgs(
+      Concept, Concept->getLexicalDeclContext(),
+      /*Final=*/false, CSE->getTemplateArguments(),
+      /*RelativeToPrimary=*/true,
+      /*Pattern=*/nullptr,
+      /*ForConstraintInstantiation=*/true);
+  return S.SubstConceptTemplateArguments(CSE, Concept->getConstraintExpr(),
+                                         MLTAL);
+}
+
 bool Sema::CheckConstraintSatisfaction(
     const ConceptSpecializationExpr *ConstraintExpr,
     ConstraintSatisfaction &Satisfaction) {
 
+  ExprResult Res = SubstituteConceptsInConstrainExpression(
+      *this, nullptr, ConstraintExpr, ArgPackSubstIndex);
+  if (!Res.isUsable())
+    return true;
+
   llvm::SmallVector<AssociatedConstraint, 1> Constraints;
   Constraints.emplace_back(
       ConstraintExpr->getNamedConcept()->getConstraintExpr());
@@ -2249,8 +2287,14 @@ NormalizedConstraint *NormalizedConstraint::fromConstraintExpr(
       // Use canonical declarations to merge ConceptDecls across
       // different modules.
       ConceptDecl *CD = CSE->getNamedConcept()->getCanonicalDecl();
+
+      ExprResult Res =
+          SubstituteConceptsInConstrainExpression(S, D, CSE, SubstIndex);
+      if (!Res.isUsable())
+        return nullptr;
+
       SubNF = NormalizedConstraint::fromAssociatedConstraints(
-          S, CD, AssociatedConstraint(CD->getConstraintExpr(), SubstIndex));
+          S, CD, AssociatedConstraint(Res.get(), SubstIndex));
 
       if (!SubNF)
         return nullptr;

clang/lib/Sema/SemaTemplateInstantiate.cpp

@@ -4487,6 +4487,109 @@ ExprResult Sema::SubstConstraintExprWithoutSatisfaction(
   return Instantiator.TransformExpr(E);
 }
 
+ExprResult Sema::SubstConceptTemplateArguments(
+    const ConceptSpecializationExpr *CSE, const Expr *ConstraintExpr,
+    const MultiLevelTemplateArgumentList &MLTAL) {
+  TemplateInstantiator Instantiator(*this, MLTAL, SourceLocation(),
+                                    DeclarationName());
+  auto *ArgsAsWritten = CSE->getTemplateArgsAsWritten();
+  TemplateArgumentListInfo SubstArgs(ArgsAsWritten->getLAngleLoc(),
+                                     ArgsAsWritten->getRAngleLoc());
+
+  Sema::InstantiatingTemplate Inst(
+      *this, ArgsAsWritten->arguments().front().getSourceRange().getBegin(),
+      Sema::InstantiatingTemplate::ConstraintNormalization{},
+      CSE->getNamedConcept(),
+      ArgsAsWritten->arguments().front().getSourceRange());
+
+  if (Instantiator.TransformConceptTemplateArguments(
+          ArgsAsWritten->getTemplateArgs(),
+          ArgsAsWritten->getTemplateArgs() +
+              ArgsAsWritten->getNumTemplateArgs(),
+          SubstArgs))
+    return true;
+
+  llvm::SmallVector<TemplateArgument, 4> NewArgList;
+  NewArgList.reserve(SubstArgs.arguments().size());
+  for (const auto &ArgLoc : SubstArgs.arguments())
+    NewArgList.push_back(ArgLoc.getArgument());
+
+  MultiLevelTemplateArgumentList MLTALForConstraint =
+      getTemplateInstantiationArgs(
+          CSE->getNamedConcept(),
+          CSE->getNamedConcept()->getLexicalDeclContext(),
+          /*Final=*/false,
+          /*Innermost=*/NewArgList,
+          /*RelativeToPrimary=*/true,
+          /*Pattern=*/nullptr,
+          /*ForConstraintInstantiation=*/true);
+
+  struct ConstraintExprTransformer : TreeTransform<ConstraintExprTransformer> {
+    using Base = TreeTransform<ConstraintExprTransformer>;
+    MultiLevelTemplateArgumentList &MLTAL;
+
+    ConstraintExprTransformer(Sema &SemaRef,
+                              MultiLevelTemplateArgumentList &MLTAL)
+        : TreeTransform(SemaRef), MLTAL(MLTAL) {}
+
+    ExprResult TransformExpr(Expr *E) {
+      if (!E)
+        return E;
+      switch (E->getStmtClass()) {
+      case Stmt::BinaryOperatorClass:
+      case Stmt::ConceptSpecializationExprClass:
+      case Stmt::ParenExprClass:
+      case Stmt::UnresolvedLookupExprClass:
+        return Base::TransformExpr(E);
+      default:
+        break;
+      }
+      return E;
+    }
+
+    ExprResult TransformBinaryOperator(BinaryOperator *E) {
+      if (!(E->getOpcode() == BinaryOperatorKind::BO_LAnd ||
+            E->getOpcode() == BinaryOperatorKind::BO_LOr))
+        return E;
+
+      ExprResult LHS = TransformExpr(E->getLHS());
+      ExprResult RHS = TransformExpr(E->getRHS());
+
+      if (LHS.get() == E->getLHS() && RHS.get() == E->getRHS())
+        return E;
+
+      return BinaryOperator::Create(SemaRef.Context, LHS.get(), RHS.get(),
+                                    E->getOpcode(), SemaRef.Context.BoolTy,
+                                    VK_PRValue, OK_Ordinary,
+                                    E->getOperatorLoc(), FPOptionsOverride{});
+    }
+
+    bool TransformTemplateArgument(const TemplateArgumentLoc &Input,
+                                   TemplateArgumentLoc &Output,
+                                   bool Uneval = false) {
+      if (Input.getArgument().isConceptOrConceptTemplateParameter())
+        return Base::TransformTemplateArgument(Input, Output, Uneval);
+
+      Output = Input;
+      return false;
+    }
+
+    ExprResult TransformUnresolvedLookupExpr(UnresolvedLookupExpr *E,
+                                             bool IsAddressOfOperand = false) {
+      if (E->isConceptReference()) {
+        ExprResult Res = SemaRef.SubstExpr(E, MLTAL);
+        return Res;
+      }
+      return E;
+    }
+  };
+
+  ConstraintExprTransformer Transformer(*this, MLTALForConstraint);
+  ExprResult Res =
+      Transformer.TransformExpr(const_cast<Expr *>(ConstraintExpr));
+  return Res;
+}
+
 ExprResult Sema::SubstInitializer(Expr *Init,
                           const MultiLevelTemplateArgumentList &TemplateArgs,
                           bool CXXDirectInit) {

clang/lib/Sema/TreeTransform.h

@@ -694,6 +694,12 @@ class TreeTransform {
                                   TemplateArgumentListInfo &Outputs,
                                   bool Uneval = false);
 
+  template <typename InputIterator>
+  bool TransformConceptTemplateArguments(InputIterator First,
+                                         InputIterator Last,
+                                         TemplateArgumentListInfo &Outputs,
+                                         bool Uneval = false);
+
   /// Checks if the argument pack from \p In will need to be expanded and does
   /// the necessary prework.
   /// Whether the expansion is needed is captured in Info.Expand.
@@ -5192,6 +5198,46 @@ bool TreeTransform<Derived>::TransformTemplateArguments(
   return false;
 }
 
+template <typename Derived>
+template <typename InputIterator>
+bool TreeTransform<Derived>::TransformConceptTemplateArguments(
+    InputIterator First, InputIterator Last, TemplateArgumentListInfo &Outputs,
+    bool Uneval) {
+
+  auto isNonDependentConcept = [](const TemplateArgument &Arg) {
+    return !Arg.isDependent() && Arg.isConceptOrConceptTemplateParameter();
+  };
+
+  for (; First != Last; ++First) {
+    TemplateArgumentLoc Out;
+    TemplateArgumentLoc In = *First;
+
+    if (In.getArgument().getKind() == TemplateArgument::Pack) {
+      typedef TemplateArgumentLocInventIterator<Derived,
+                                                TemplateArgument::pack_iterator>
+          PackLocIterator;
+      if (TransformConceptTemplateArguments(
+              PackLocIterator(*this, In.getArgument().pack_begin()),
+              PackLocIterator(*this, In.getArgument().pack_end()), Outputs,
+              Uneval))
+        return true;
+      continue;
+    }
+
+    if (!isNonDependentConcept(In.getArgument())) {
+      Outputs.addArgument(In);
+      continue;
+    }
+
+    if (getDerived().TransformTemplateArgument(In, Out, Uneval))
+      return true;
+
+    Outputs.addArgument(Out);
+  }
+
+  return false;
+}
+
 // FIXME: Find ways to reduce code duplication for pack expansions.
 template <typename Derived>
 bool TreeTransform<Derived>::PreparePackForExpansion(TemplateArgumentLoc In,

clang/test/SemaCXX/cxx2c-template-template-param.cpp

@@ -350,3 +350,87 @@ template <A<concept missing<int>> T> // expected-error {{expected expression}} \
                                      // expected-error {{expected unqualified-id}}
 auto f();
 }
+
+namespace concept_arg_normalization {
+
+template <typename T,
+          template <typename...> concept C1>
+concept one = (C1<T>); // #concept-arg-one
+
+template <typename T>
+concept A = true; // #concept-arg-A
+
+template <typename T>
+concept BetterA = A<T> && true;
+
+template <typename T>
+concept B = true; // #concept-arg-B
+
+template <typename T>
+concept False = false; // #concept-arg-False
+
+template <typename T>
+requires one<T, A>
+void f1(T){} // #concept-arg-f1-1
+
+template <typename T>
+requires one<T, B>
+void f1(T){} // #concept-arg-f1-2
+
+template <typename T>
+requires one<T, A>
+void f2(T){}
+
+template <typename T>
+requires one<T, BetterA>
+void f2(T){}
+
+
+template <template <typename> concept CT>
+requires one<int, A>
+void f3(){} // #concept-arg-f3-1
+
+template <template <typename> concept CT>
+requires one<int, CT>
+void f3(){} // #concept-arg-f3-2
+
+template <typename T>
+requires one<T, False> void f4(T){} // #concept-arg-f4
+
+
+void test() {
+    f1(0);
+    // expected-error@-1 {{call to 'f1' is ambiguous}}
+    // expected-note@#concept-arg-f1-1{{candidate function [with T = int]}}
+    // expected-note@#concept-arg-f1-2{{candidate function [with T = int]}}
+    // expected-note@#concept-arg-A {{similar constraint expressions not considered equivalent}}
+    // expected-note@#concept-arg-B {{similar constraint expression here}}
+    f2(0);
+
+    f3<BetterA>();
+    // expected-error@-1 {{call to 'f3' is ambiguous}}
+    // expected-note@#concept-arg-f3-1 {{candidate function [with CT = concept_arg_normalization::BetterA]}}
+    // expected-note@#concept-arg-f3-2 {{candidate function [with CT = concept_arg_normalization::BetterA]}}
+
+static_assert(one<int, A>);
+static_assert(one<int, False>);
+// expected-error@-1 {{static assertion failed}} \
+// expected-note@-1 {{because 'one<int, False>' evaluated to false}}
+// expected-note@#concept-arg-one {{because 'int' does not satisfy 'False'}}
+// expected-note@#concept-arg-False {{because 'false' evaluated to false}}
+
+f4(0);
+// expected-error@-1 {{no matching function for call to 'f4'}}
+// expected-note@#concept-arg-f4 {{candidate template ignored: constraints not satisfied [with T = int]}}
+// expected-note@#concept-arg-f4 {{because 'one<int, False>'}}
+// expected-note@#concept-arg-one {{because 'int' does not satisfy 'False'}}
+// expected-note@#concept-arg-False {{because 'false' evaluated to false}}
+
+
+template <typename T, template <typename...> concept C1>
+concept TestBinary = T::a || C1<T>;
+static_assert(TestBinary<int, A>);
+
+}
+
+}