Rollup merge of #85900 - LingMan:pat_mat, r=petrochenkov

Use pattern matching instead of checking lengths explicitly

This piece of code checks that there are exaclty two variants, one having
exactly one field, the other having exactly zero fields. If any of these
conditions is violated, it returns `None`. Otherwise it assigns that one
field's ty to `field_ty`.

Instead of fiddling with indices and length checks explicitly, use pattern
matching to simplify this.

`@rustbot` modify labels +C-cleanup +T-compiler

0 files changed, 0 insertions, 0 deletions