1 files changed, 26 insertions, 0 deletions
diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index 22803653edf..d25b4dda885 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -4861,6 +4861,17 @@ NamedDecl *Sema::HandleDeclarator(Scope *S, Declarator &D,
   if (getLangOpts().CPlusPlus)
     CheckExtraCXXDefaultArguments(D);
 
+  if (D.getDeclSpec().isConceptSpecified()) {
+    // C++ Concepts TS [dcl.spec.concept]p1: The concept specifier shall be
+    // applied only to the definition of a function template or variable
+    // template, declared in namespace scope
+    if (!DC->getRedeclContext()->isFileContext()) {
+      Diag(D.getIdentifierLoc(),
+           diag::err_concept_decls_may_only_appear_in_namespace_scope);
+      return nullptr;
+    }
+  }
+
   NamedDecl *New;
 
   bool AddToScope = true;
@@ -7203,6 +7214,7 @@ Sema::ActOnFunctionDeclarator(Scope *S, Declarator &D, DeclContext *DC,
     bool isVirtual = D.getDeclSpec().isVirtualSpecified();
     bool isExplicit = D.getDeclSpec().isExplicitSpecified();
     bool isConstexpr = D.getDeclSpec().isConstexprSpecified();
+    bool isConcept = D.getDeclSpec().isConceptSpecified();
     isFriend = D.getDeclSpec().isFriendSpecified();
     if (isFriend && !isInline && D.isFunctionDefinition()) {
       // C++ [class.friend]p5
@@ -7419,6 +7431,20 @@ Sema::ActOnFunctionDeclarator(Scope *S, Declarator &D, DeclContext *DC,
         Diag(D.getDeclSpec().getConstexprSpecLoc(), diag::err_constexpr_dtor);
     }
 
+    if (isConcept) {
+      // C++ Concepts TS [dcl.spec.concept]p1: The concept specifier shall be
+      // applied only to the definition of a function template...
+      if (!D.isFunctionDefinition()) {
+        Diag(D.getDeclSpec().getConceptSpecLoc(),
+             diag::err_function_concept_not_defined);
+        NewFD->setInvalidDecl();
+      }
+
+      // C++ Concepts TS [dcl.spec.concept]p2: Every concept definition is
+      // implicity defined to be a constexpr declaration (implicitly inline)
+      NewFD->setImplicitlyInline();
+    }
+
     // If __module_private__ was specified, mark the function accordingly.
     if (D.getDeclSpec().isModulePrivateSpecified()) {
       if (isFunctionTemplateSpecialization) {