make palceholders less sticky

Author: kaikalii

src/format.rs

@@ -631,7 +631,9 @@ impl<'a> Formatter<'a> {
                 );
                 self.format_words(&m.operands, true, depth);
             }
-            Word::Placeholder(sig) => self.format_signature('^', *sig, false),
+            Word::Placeholder(sig) => {
+                self.format_signature('^', *sig, word.span.as_str().ends_with(' '))
+            }
             Word::Spaces => self.push(&word.span, " "),
             Word::Comment(comment) => {
                 let beginning_of_line = self

src/parse.rs

@@ -327,8 +327,10 @@ impl Parser {
         let start = self.try_exact(initial_token)?;
         self.try_spaces();
         let (args, outs) = self.sig_inner();
-        let end = self.prev_span();
-        self.try_spaces();
+        let mut end = self.prev_span();
+        if let Some(sp) = self.try_spaces() {
+            end = sp.span;
+        }
         let span = start.merge(end);
         Some(span.sp(Signature::new(args, outs)))
     }