Merge #647

647: Fail parsing of missing display hint r=japaric a=justahero

Before this change a format string was allowed to contain `{:}` without a display hint, which resulted in a `DisplayHint::NoHint`.

Co-authored-by: Sebastian Ziebell <[email protected]>

Author: bors[bot]

parser/src/lib.rs

@@ -340,6 +340,9 @@ fn parse_param(mut input: &str, mode: ParserMode) -> Result<Param, Cow<'static,
     if input.starts_with(HINT_PREFIX) {
         // skip the prefix
         input = &input[HINT_PREFIX.len()..];
+        if input.is_empty() {
+            return Err("malformed format string (missing display hint after ':')".into());
+        }
 
         hint = Some(match parse_display_hint(input) {
             Some(a) => a,
@@ -1111,6 +1114,10 @@ mod tests {
             parse("{0dunno}", ParserMode::Strict),
             Err("unexpected content \"dunno\" in format string".into())
         );
+        assert_eq!(
+            parse("{:}", ParserMode::Strict),
+            Err("malformed format string (missing display hint after ':')".into())
+        );
     }
 
     #[test]