Point at the match discriminant when arm pattern has a type mismatch

src/test/ui/pattern/pattern-error-continue.stderr

@@ -21,6 +21,8 @@ LL |         A::B(_, _, _) => (), //~ ERROR this pattern has 3 fields, but
 error[E0308]: mismatched types
   --> $DIR/pattern-error-continue.rs:22:9
    |
+LL |     match 'c' {
+   |           --- this match expression evaluates to `char`
 LL |         S { .. } => (),
    |         ^^^^^^^^ expected char, found struct `S`
    |

src/test/ui/pattern/pattern-tyvar.stderr

@@ -1,6 +1,8 @@
 error[E0308]: mismatched types
   --> $DIR/pattern-tyvar.rs:5:18
    |
+LL |     match t {
+   |           - this match expression evaluates to `std::option::Option<std::vec::Vec<isize>>`
 LL |       Bar::T1(_, Some::<isize>(x)) => { //~ ERROR mismatched types
    |                  ^^^^^^^^^^^^^^^^ expected struct `std::vec::Vec`, found isize
    |