(fix) Ignore empty brackets

Compiler would crash if `[]` occured in the macro invocation (e.g.
`vec![]`).

Author: SkylerLipthay

Cargo.toml

@@ -1,7 +1,7 @@
 [package]
 
 name = "interpolate_idents"
-version = "0.0.2"
+version = "0.0.3"
 authors = ["Skyler Lipthay <[email protected]>"]
 description = "Useable macro identifier concatenation plugin"
 readme = "README.md"

src/lib.rs

@@ -39,8 +39,13 @@ fn interpolate_idents<'a>(cx: &'a mut ExtCtxt,
                     }
                 }
 
-                let new_ident = token::str_to_ident(&new_ident[..]);
-                Some(TtToken(new_span.unwrap(), Token::Ident(new_ident, IdentStyle::Plain)))
+                match new_span {
+                    Some(s) => {
+                        let new_ident = token::str_to_ident(&new_ident[..]);
+                        Some(TtToken(s, Token::Ident(new_ident, IdentStyle::Plain)))
+                    },
+                    None => None
+                }
             },
             _ => None,
         }

tests/tests.rs

@@ -21,3 +21,21 @@ fn test_macro() {
     assert_eq!(foo_bar_1(), 1);
     assert_eq!(Foobar::new().bar_30, 30);
 }
+
+macro_rules! define_brackets {
+    () => ( interpolate_idents! {
+        fn brackets() -> Vec<i32> {
+            let mut b: Vec<i32> = vec![];
+            let c: Vec<i32> = vec![1, 2, 3];
+            b.push(c[1]);
+            b
+        }
+    } )
+}
+
+define_brackets!();
+
+#[test]
+fn test_brackets() {
+    assert_eq!(brackets(), vec![2]);
+}