1 files changed, 92 insertions, 4 deletions

diff --git a/clang/lib/Sema/SemaTemplate.cpp b/clang/lib/Sema/SemaTemplate.cpp
index 49ba771379e..fba8cd4eee0 100644
--- a/clang/lib/Sema/SemaTemplate.cpp
+++ b/clang/lib/Sema/SemaTemplate.cpp
@@ -271,9 +271,11 @@ TemplateNameKind Sema::isTemplateName(Scope *S,
     } else {
       assert(isa<ClassTemplateDecl>(TD) || isa<TemplateTemplateParmDecl>(TD) ||
              isa<TypeAliasTemplateDecl>(TD) || isa<VarTemplateDecl>(TD) ||
-             isa<BuiltinTemplateDecl>(TD));
+             isa<BuiltinTemplateDecl>(TD) || isa<ConceptDecl>(TD));
       TemplateKind =
-          isa<VarTemplateDecl>(TD) ? TNK_Var_template : TNK_Type_template;
+          isa<VarTemplateDecl>(TD) ? TNK_Var_template :
+          isa<ConceptDecl>(TD) ? TNK_Concept_template :
+          TNK_Type_template;
     }
   }
 
@@ -3227,7 +3229,8 @@ QualType Sema::CheckTemplateIdType(TemplateName Name,
 
   TemplateDecl *Template = Name.getAsTemplateDecl();
   if (!Template || isa<FunctionTemplateDecl>(Template) ||
-      isa<VarTemplateDecl>(Template)) {
+      isa<VarTemplateDecl>(Template) ||
+      isa<ConceptDecl>(Template)) {
     // We might have a substituted template template parameter pack. If so,
     // build a template specialization type for it.
     if (Name.getAsSubstTemplateTemplateParmPack())
@@ -4234,6 +4237,18 @@ void Sema::diagnoseMissingTemplateArguments(TemplateName Name,
   }
 }
 
+ExprResult
+Sema::CheckConceptTemplateId(const CXXScopeSpec &SS,
+                             const DeclarationNameInfo &NameInfo,
+                             ConceptDecl *Template,
+                             SourceLocation TemplateLoc,
+                             const TemplateArgumentListInfo *TemplateArgs) {
+  // TODO: Do concept specialization here.
+  Diag(NameInfo.getBeginLoc(), diag::err_concept_not_implemented) <<
+    "concept specialization";
+  return ExprError();
+}
+
 ExprResult Sema::BuildTemplateIdExpr(const CXXScopeSpec &SS,
                                      SourceLocation TemplateKWLoc,
                                      LookupResult &R,
@@ -4274,6 +4289,12 @@ ExprResult Sema::BuildTemplateIdExpr(const CXXScopeSpec &SS,
                               TemplateKWLoc, TemplateArgs);
   }
 
+  if (R.getAsSingle<ConceptDecl>() && !AnyDependentArguments()) {
+    return CheckConceptTemplateId(SS, R.getLookupNameInfo(),
+                                  R.getAsSingle<ConceptDecl>(),
+                                  TemplateKWLoc, TemplateArgs);
+  }
+
   // We don't want lookup warnings at this point.
   R.suppressDiagnostics();
 
@@ -7974,7 +7995,74 @@ Decl *Sema::ActOnTemplateDeclarator(Scope *S,
   return NewDecl;
 }
 
-/// Strips various properties off an implicit instantiation
+Decl *Sema::ActOnConceptDefinition(Scope *S,
+                              MultiTemplateParamsArg TemplateParameterLists,
+                                   IdentifierInfo *Name, SourceLocation NameLoc,
+                                   Expr *ConstraintExpr) {
+  DeclContext *DC = CurContext;
+
+  if (!DC->getRedeclContext()->isFileContext()) {
+    Diag(NameLoc,
+      diag::err_concept_decls_may_only_appear_in_global_namespace_scope);
+    return nullptr;
+  }
+
+  if (TemplateParameterLists.size() > 1) {
+    Diag(NameLoc, diag::err_concept_extra_headers);
+    return nullptr;
+  }
+
+  if (TemplateParameterLists.front()->size() == 0) {
+    Diag(NameLoc, diag::err_concept_no_parameters);
+    return nullptr;
+  }
+
+  ConceptDecl *NewDecl = ConceptDecl::Create(Context, DC, NameLoc, Name,
+                                             TemplateParameterLists.front(),
+                                             ConstraintExpr);
+
+  if (!ConstraintExpr->isTypeDependent() &&
+      ConstraintExpr->getType() != Context.BoolTy) {
+    // C++2a [temp.constr.atomic]p3:
+    // E shall be a constant expression of type bool.
+    // TODO: Do this check for individual atomic constraints
+    // and not the constraint expression. Probably should do it in
+    // ParseConstraintExpression.
+    Diag(ConstraintExpr->getSourceRange().getBegin(),
+        diag::err_concept_initialized_with_non_bool_type)
+      << ConstraintExpr->getType();
+    NewDecl->setInvalidDecl();
+  }
+
+  if (NewDecl->getAssociatedConstraints()) {
+    // C++2a [temp.concept]p4:
+    // A concept shall not have associated constraints.
+    // TODO: Make a test once we have actual associated constraints.
+    Diag(NameLoc, diag::err_concept_no_associated_constraints);
+    NewDecl->setInvalidDecl();
+  }
+
+  // Check for conflicting previous declaration.
+  DeclarationNameInfo NameInfo(NewDecl->getDeclName(), NameLoc);
+  LookupResult Previous(*this, NameInfo, LookupOrdinaryName,
+                        ForVisibleRedeclaration);
+  LookupName(Previous, S);
+
+  FilterLookupForScope(Previous, DC, S, /*ConsiderLinkage=*/false,
+                       /*AllowInlineNamespace*/false);
+  if (!Previous.empty()) {
+    auto *Old = Previous.getRepresentativeDecl();
+    Diag(NameLoc, isa<ConceptDecl>(Old) ? diag::err_redefinition :
+         diag::err_redefinition_different_kind) << NewDecl->getDeclName();
+    Diag(Old->getLocation(), diag::note_previous_definition);
+  }
+
+  ActOnDocumentableDecl(NewDecl);
+  PushOnScopeChains(NewDecl, S);
+  return NewDecl;
+}
+
+/// \brief Strips various properties off an implicit instantiation
 /// that has just been explicitly specialized.
 static void StripImplicitInstantiation(NamedDecl *D) {
   D->dropAttr<DLLImportAttr>();