Adjust span of closure param

compiler/rustc_parse/src/parser/expr.rs

@@ -2268,7 +2268,7 @@ impl<'a> Parser<'a> {
                     attrs: attrs.into(),
                     ty,
                     pat,
-                    span: lo.to(this.token.span),
+                    span: lo.to(this.prev_token.span),
                     id: DUMMY_NODE_ID,
                     is_placeholder: false,
                 },

src/test/ui/unboxed-closures/unboxed-closures-type-mismatch.stderr

@@ -10,7 +10,7 @@ note: closure parameter defined here
   --> $DIR/unboxed-closures-type-mismatch.rs:4:18
    |
 LL |     let mut f = |x: isize, y: isize| -> isize { x + y };
-   |                  ^^^^^^^^^
+   |                  ^^^^^^^^
 help: change the type of the numeric literal from `usize` to `isize`
    |
 LL |     let z = f(1_isize, 2);