(Maybe) fix macro compatibility for older Rusts

Author: mhallin

.travis.yml

@@ -2,14 +2,16 @@ language: rust
 cache: cargo
 
 rust:
+  - stable
+  - beta
+  - nightly
+
+  # The five most recent stable releases before "stable"
   - 1.10.0
   - 1.11.0
   - 1.12.1
   - 1.13.0
   - 1.14.0
-  - stable
-  - beta
-  - nightly
 
 matrix:
   allow_failures:

src/macros/scalar.rs

@@ -38,6 +38,8 @@ usable as arguments and default values.
 */
 #[macro_export]
 macro_rules! graphql_scalar {
+    ( @as_expr, $e:expr) => { $e };
+
     // Calls $val.$func($arg) if $arg is not None
     ( @maybe_apply, None, $func:ident, $val:expr ) => { $val };
     ( @maybe_apply, $arg:tt, $func:ident, $val:expr ) => { $val.$func($arg) };
@@ -65,7 +67,7 @@ macro_rules! graphql_scalar {
             type Context = ();
 
             fn name() -> Option<&'static str> {
-                Some($outname)
+                Some(graphql_scalar!( @as_expr, $outname ))
             }
 
             fn meta<'r>(registry: &mut $crate::Registry<'r>) -> $crate::meta::MetaType<'r> {