Avoid type mismatch error where a variable is bound with different ref-ness

[nrc]

e.g.,

match x {
      opts::a(ref i) | opts::b(i) => {}
      //~^ ERROR variable `i` is bound with different mode in pattern #2 than in pattern #1
      //~^^ ERROR mismatched types

Where the field of a and b has the same type

cc #30320

[estebank]

Current output, no change:

error[E0409]: variable `i` is bound in inconsistent ways within the same match arm
 --> src/main.rs:8:32
  |
8 |       opts::a(ref i) | opts::b(i) => {}
  |                   -            ^ bound in different ways
  |                   |
  |                   first binding

error[E0308]: mismatched types
 --> src/main.rs:8:32
  |
8 |       opts::a(ref i) | opts::b(i) => {}
  |                                ^ expected &isize, found isize
  |
  = note: expected type `&isize`
             found type `isize`

[estebank]

Current output:

error[E0409]: variable `i` is bound inconsistently across alternatives separated by `|`
 --> src/lib.rs:8:32
  |
8 |       opts::a(ref i) | opts::b(i) => {}
  |                   -            ^ bound in different ways
  |                   |
  |                   first binding

error[E0308]: mismatched types
 --> src/lib.rs:8:32
  |
7 |     match x {
  |           - this expression has type `opts`
8 |       opts::a(ref i) | opts::b(i) => {}
  |               -----            ^ expected `&isize`, found `isize`
  |               |
  |               first introduced with type `&isize` here
  |
  = note: in the same arm, a binding must have the same type in all alternatives
help: consider adding `ref`
  |
8 |       opts::a(ref i) | opts::b(ref i) => {}
  |                                +++

I don't know what else we can do here beyond silencing the E0409.