Merge pull request #301 from dtolnay/negative

Support negative int and float literals in FromStr

src/fallback.rs

@@ -896,10 +896,20 @@ impl Literal {
 impl FromStr for Literal {
     type Err = LexError;
 
-    fn from_str(repr: &str) -> Result<Self, Self::Err> {
+    fn from_str(mut repr: &str) -> Result<Self, Self::Err> {
+        let negative = repr.starts_with('-');
+        if negative {
+            repr = &repr[1..];
+            if !repr.starts_with(|ch: char| ch.is_ascii_digit()) {
+                return Err(LexError::call_site());
+            }
+        }
         let cursor = get_cursor(repr);
-        if let Ok((_rest, literal)) = parse::literal(cursor) {
+        if let Ok((_rest, mut literal)) = parse::literal(cursor) {
             if literal.text.len() == repr.len() {
+                if negative {
+                    literal.text.insert(0, '-');
+                }
                 return Ok(literal);
             }
         }

tests/test.rs

@@ -168,7 +168,11 @@ fn literal_iter_negative() {
 #[test]
 fn literal_parse() {
     assert!("1".parse::<Literal>().is_ok());
+    assert!("-1".parse::<Literal>().is_ok());
+    assert!("-1u12".parse::<Literal>().is_ok());
     assert!("1.0".parse::<Literal>().is_ok());
+    assert!("-1.0".parse::<Literal>().is_ok());
+    assert!("-1.0f12".parse::<Literal>().is_ok());
     assert!("'a'".parse::<Literal>().is_ok());
     assert!("\"\n\"".parse::<Literal>().is_ok());
     assert!("0 1".parse::<Literal>().is_err());
@@ -177,6 +181,9 @@ fn literal_parse() {
     assert!("/* comment */0".parse::<Literal>().is_err());
     assert!("0/* comment */".parse::<Literal>().is_err());
     assert!("0// comment".parse::<Literal>().is_err());
+    assert!("- 1".parse::<Literal>().is_err());
+    assert!("- 1.0".parse::<Literal>().is_err());
+    assert!("-\"\"".parse::<Literal>().is_err());
 }
 
 #[test]