Add label to primary span in some parse errors

src/test/ui/cross-file-errors/main.stderr

@@ -2,7 +2,7 @@ error: expected expression, found `_`
   --> $DIR/underscore.rs:18:9
    |
 LL |         _
-   |         ^
+   |         ^ expected expression
    | 
   ::: $DIR/main.rs:15:5
    |

src/test/ui/macro-context.stderr

@@ -38,7 +38,7 @@ error: expected expression, found reserved keyword `typeof`
   --> $DIR/macro-context.rs:13:17
    |
 LL |     () => ( i ; typeof );   //~ ERROR expected expression, found reserved keyword `typeof`
-   |                 ^^^^^^
+   |                 ^^^^^^ expected expression
 ...
 LL |     m!();
    |     ----- in this macro invocation

src/test/ui/resolve/token-error-correct.stderr

@@ -26,7 +26,7 @@ error: expected expression, found `;`
   --> $DIR/token-error-correct.rs:14:13
    |
 LL |     foo(bar(;
-   |             ^
+   |             ^ expected expression
 
 error: aborting due to 3 previous errors
 

src/test/ui/token/issue-10636-2.stderr

@@ -20,7 +20,7 @@ error: expected expression, found `)`
   --> $DIR/issue-10636-2.rs:18:1
    |
 LL | } //~ ERROR: incorrect close delimiter
-   | ^
+   | ^ expected expression
 
 error[E0601]: main function not found