Use functions not closures

src/lib.rs

@@ -41,17 +41,21 @@ mod tests {
         Object(HashMap<String, JsonValue>),
     }
 
-    #[test]
+    trait JsonParser<'a, T>: Parser<&'a str, T, &'a str> {}
-    fn parse_json() {
+    impl<'a, T, P> JsonParser<'a, T> for P where P: Parser<&'a str, T, &'a str> {}
-        let json_null = literal("null").to(JsonValue::Null);
+
-        let json_bool = choice((
+    fn json_null<'a>() -> impl JsonParser<'a, JsonValue> {
+        literal("null").to(JsonValue::Null)
+    }
+    fn json_bool<'a>() -> impl JsonParser<'a, JsonValue> {
+        choice((
             literal("true").to(JsonValue::Bool(true)),
             literal("false").to(JsonValue::Bool(false)),
-        ));
+        ))
+    }
 
+    fn json_number() -> impl JsonParser<'static, JsonValue> {
         let digit = || one_of("1234567890");
-        assert_eq!(digit().parse("3"), Ok(("3", "")));
-
         let digits = || repeated(digit()).at_least(1);
 
         let json_number_inner = choice((
@@ -72,7 +76,6 @@ mod tests {
         ))
         .map(|digits| digits.parse::<f64>().unwrap());
 
-        let json_number =
         literal("-")
             .optional()
             .then(json_number_inner)
@@ -81,31 +84,41 @@ mod tests {
                     val *= -1.0;
                 }
                 JsonValue::Num(val)
-                });
+            })
+    }
 
-        assert_eq!(
+    fn json_string<'a>() -> impl JsonParser<'a, JsonValue> {
-            json_number.parse("-383").unwrap().0,
+        seq((
-            JsonValue::Num(-383f64)
-        );
-        assert_eq!(
-            json_number.parse("-.383").unwrap().0,
-            JsonValue::Num(-0.383)
-        );
-        assert_eq!(json_number.parse(".383").unwrap().0, JsonValue::Num(0.383));
-        assert_eq!(
-            json_number.parse("-1.383").unwrap().0,
-            JsonValue::Num(-1.383)
-        );
-
-        let json_string = seq((
             literal_char('"'),
             pred(any_char, |ch| *ch != '"'),
             literal_char('"'),
         ))
-        .map(|(_, s, _)| JsonValue::Str(s.to_string()));
+        .map(|(_, s, _)| JsonValue::Str(s.to_string()))
+    }
 
-        let json_value = choice((json_null, json_bool, json_number, json_string));
+    fn json_value() -> impl JsonParser<'static, JsonValue> {
+        choice((json_null(), json_bool(), json_number(), json_string()))
+    }
 
-        assert_eq!(json_value.parse("true"), Ok((JsonValue::Bool(true), "")));
+    #[test]
+    fn parse_json() {
+        assert_eq!(
+            json_number().parse("-383").unwrap().0,
+            JsonValue::Num(-383f64)
+        );
+        assert_eq!(
+            json_number().parse("-.383").unwrap().0,
+            JsonValue::Num(-0.383)
+        );
+        assert_eq!(
+            json_number().parse(".383").unwrap().0,
+            JsonValue::Num(0.383)
+        );
+        assert_eq!(
+            json_number().parse("-1.383").unwrap().0,
+            JsonValue::Num(-1.383)
+        );
+
+        assert_eq!(json_value().parse("true"), Ok((JsonValue::Bool(true), "")));
     }
 }