Make isWideString compatible with Phobos isNarrowString

tests/tanya/memory/tests/smartref.d

@@ -3,6 +3,7 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 module tanya.memory.tests.smartref;
 
+import std.traits : ReturnType;
 import tanya.memory.allocator;
 import tanya.memory.smartref;
 import tanya.meta.trait;

tests/tanya/meta/tests/trait.d

@@ -1,91 +0,0 @@
-/* This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this
- * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
-module tanya.meta.tests.trait;
-
-import tanya.meta.metafunction;
-import tanya.meta.trait;
-
-// typeof(null) is not a pointer.
-@nogc nothrow pure @safe unittest
-{
-    static assert(!isPointer!(typeof(null)));
-    static assert(!isPointer!(const shared typeof(null)));
-
-    enum typeOfNull : typeof(null)
-    {
-        null_ = null,
-    }
-    static assert(!isPointer!typeOfNull);
-}
-
-@nogc nothrow pure @safe unittest
-{
-    static struct S
-    {
-        @property int opCall()
-        {
-            return 0;
-        }
-    }
-    S s;
-    static assert(isCallable!S);
-    static assert(isCallable!s);
-}
-
-@nogc nothrow pure @safe unittest
-{
-    static assert(is(FunctionTypeOf!(void delegate()) == function));
-
-    static void staticFunc()
-    {
-    }
-    auto functionPointer = &staticFunc;
-    static assert(is(FunctionTypeOf!staticFunc == function));
-    static assert(is(FunctionTypeOf!functionPointer == function));
-
-    void func()
-    {
-    }
-    auto dg = &func;
-    static assert(is(FunctionTypeOf!func == function));
-    static assert(is(FunctionTypeOf!dg == function));
-
-    interface I
-    {
-        @property int prop();
-    }
-    static assert(is(FunctionTypeOf!(I.prop) == function));
-
-    static struct S
-    {
-        void opCall()
-        {
-        }
-    }
-    class C
-    {
-        static void opCall()
-        {
-        }
-    }
-    S s;
-
-    static assert(is(FunctionTypeOf!s == function));
-    static assert(is(FunctionTypeOf!C == function));
-    static assert(is(FunctionTypeOf!S == function));
-}
-
-@nogc nothrow pure @safe unittest
-{
-    static struct S2
-    {
-        @property int opCall()
-        {
-            return 0;
-        }
-    }
-    S2 s2;
-    static assert(is(FunctionTypeOf!S2 == function));
-    static assert(is(FunctionTypeOf!s2 == function));
-}