Merge pull request #4882 from somzzz/issue_8799

fix issue 8799

std/meta.d

@@ -100,6 +100,75 @@ template AliasSeq(TList...)
     static assert(is(Types == AliasSeq!(int, double, char)));
 }
 
+
+/**
+  Returns an `AliasSeq` expression of `Func` being
+  applied to every variadic template argument.
+ */
+
+///
+@safe unittest
+{
+    auto ref ArgCall(alias Func, alias arg)()
+    {
+        return Func(arg);
+    }
+
+    template Map(alias Func, args...)
+    {
+        static if (args.length > 1)
+        {
+            alias Map = AliasSeq!(ArgCall!(Func, args[0]), Map!(Func, args[1 .. $]));
+        }
+        else
+        {
+            alias Map = ArgCall!(Func, args[0]);
+        }
+    }
+
+    static int square(int arg)
+    {
+        return arg * arg;
+    }
+
+    static int refSquare(ref int arg)
+    {
+        arg *= arg;
+        return arg;
+    }
+
+    static ref int refRetSquare(ref int arg)
+    {
+        arg *= arg;
+        return arg;
+    }
+
+    static void test(int a, int b)
+    {
+        assert(a == 4);
+        assert(b == 16);
+    }
+
+    static void testRef(ref int a, ref int b)
+    {
+        assert(a++ == 16);
+        assert(b++ == 256);
+    }
+
+    static int a = 2;
+    static int b = 4;
+
+    test(Map!(square, a, b));
+
+    test(Map!(refSquare, a, b));
+    assert(a == 4);
+    assert(b == 16);
+
+    testRef(Map!(refRetSquare, a, b));
+    assert(a == 17);
+    assert(b == 257);
+}
+
 /**
  * Allows `alias`ing of any single symbol, type or compile-time expression.
  *