Index: cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td
===================================================================
--- cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td
+++ cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td
@@ -1994,6 +1994,8 @@
 def err_concept_decl_invalid_specifiers : Error<
   "%select{variable|function}0 concept cannot be declared "
   "'%select{thread_local|inline|friend|constexpr}1'">;
+def err_function_concept_with_params : Error<
+  "function concept cannot have any parameters">;
 
 // C++11 char16_t/char32_t
 def warn_cxx98_compat_unicode_type : Warning<
Index: cfe/trunk/lib/Sema/SemaDecl.cpp
===================================================================
--- cfe/trunk/lib/Sema/SemaDecl.cpp
+++ cfe/trunk/lib/Sema/SemaDecl.cpp
@@ -7607,6 +7607,13 @@
         } else {
           Context.adjustExceptionSpec(NewFD, EST_BasicNoexcept);
         }
+
+        // C++ Concepts TS [dcl.spec.concept]p5: A function concept has the
+        // following restrictions:
+        // - The declaration's parameter list shall be equivalent to an empty
+        //   parameter list.
+        if ((FPT->getNumParams() > 0) || (FPT->isVariadic()))
+          Diag(NewFD->getLocation(), diag::err_function_concept_with_params);
       }
 
       // C++ Concepts TS [dcl.spec.concept]p2: Every concept definition is
Index: cfe/trunk/test/CXX/concepts-ts/dcl.dcl/dcl.spec/dcl.spec.concept/p5.cpp
===================================================================
--- cfe/trunk/test/CXX/concepts-ts/dcl.dcl/dcl.spec/dcl.spec.concept/p5.cpp
+++ cfe/trunk/test/CXX/concepts-ts/dcl.dcl/dcl.spec/dcl.spec.concept/p5.cpp
@@ -0,0 +1,13 @@
+// RUN:  %clang_cc1 -std=c++14 -fconcepts-ts -x c++ -verify %s
+
+template<typename T>
+concept bool fcpv(void) { return true; }
+
+template<typename T>
+concept bool fcpi(int i = 0) { return true; } // expected-error {{function concept cannot have any parameters}}
+
+template<typename... Ts>
+concept bool fcpp(Ts... ts) { return true; } // expected-error {{function concept cannot have any parameters}}
+
+template<typename T>
+concept bool fcpva(...) { return true; } // expected-error {{function concept cannot have any parameters}}