Accept TyError in patterns to avoid ICE on bad input

[estebank]

Fix #50585.

[rust-highfive]

r? @nikomatsakis

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[oli-obk]

I think it might be less fragile to check at the assignment of the tables field, whether tables.tainted_by_errors is true and then just not recurse.

[estebank]

Does this seem better?

[oli-obk]

Hmm no. You're right. your original thing seemed better. I thought we could check before calling from_hir or new, but I just checked and that seems messy.

r=me with your original thing

[estebank]

There's a discrepancy in regular output and -Z unpretty=mir output:

error[E0308]: mismatched types
  --> ../../src/test/compile-fail/issue-37665.rs:20:17
   |
20 |     let x: () = 0; //~ ERROR: mismatched types
   |                 ^ expected (), found integral variable
   |
   = note: expected type `()`
              found type `{integer}`

warning: variable does not need to be mutable
  --> ../../src/test/compile-fail/issue-37665.rs:17:9
   |
17 |     let mut foo : String = "hello".to_string();
   |         ----^^^
   |         |
   |         help: remove this `mut`
   |
   = note: #[warn(unused_mut)] on by default

The warning appears only in the latter. This is true in current stable too.

[estebank]

@bors r=oli-obk rollup

[bors]

📌 Commit fe5710a has been approved by oli-obk

[bors]

⌛ Testing commit fe5710a with merge 2ea922a...

[bors]

☀️ Test successful - status-appveyor, status-travis
Approved by: oli-obk
Pushing 2ea922a to master...