reserve whitespaces between prefix and pipe

src/librustc/traits/error_reporting.rs

@@ -1097,7 +1097,7 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
             //
             // move |_| { ... }
             // ^^^^^-- prefix
-            let prefix_span = self.tcx.sess.source_map().span_until_char(found_span, '|');
+            let prefix_span = self.tcx.sess.source_map().span_until_non_whitespace(found_span);
             // move |_| { ... }
             //      ^^^-- pipe_span
             let pipe_span = if let Some(span) = found_span.trim_start(prefix_span) {

src/test/ui/mismatched_types/closure-arg-count.rs

@@ -22,7 +22,7 @@ fn main() {
     //~^ ERROR closure is expected to take
     f(|| panic!());
     //~^ ERROR closure is expected to take
-    f(move || panic!());
+    f(  move    || panic!());
     //~^ ERROR closure is expected to take
 
     let _it = vec![1, 2, 3].into_iter().enumerate().map(|i, x| i);

src/test/ui/mismatched_types/closure-arg-count.stderr

@@ -63,8 +63,8 @@ LL |     f(|_| panic!());
 error[E0593]: closure is expected to take 1 argument, but it takes 0 arguments
   --> $DIR/closure-arg-count.rs:25:5
    |
-LL |     f(move || panic!());
-   |     ^ ------- takes 0 arguments
+LL |     f(  move    || panic!());
+   |     ^   ---------- takes 0 arguments
    |     |
    |     expected closure that takes 1 argument
    |
@@ -75,8 +75,8 @@ LL | fn f<F: Fn<usize>>(_: F) {}
    | ^^^^^^^^^^^^^^^^^^^^^^^^
 help: consider changing the closure to take and ignore the expected argument
    |
-LL |     f(move|_| panic!());
-   |           ^^^
+LL |     f(  move    |_| panic!());
+   |                 ^^^
 
 error[E0593]: closure is expected to take a single 2-tuple as argument, but it takes 2 distinct arguments
   --> $DIR/closure-arg-count.rs:28:53