Fix ICE on unsound_collection_transmute

[JohnTitor]

Fixes #4968

Check if Tys are normalizable. It might show hidden false negative, I'm not sure.
Also, the regression tests are placed on two dirs, so move them to /crashes. I think it will be easier to find the right place.

changelog: Fix ICE on unsound_collection_transmute

[flip1995]

Thanks for moving the tests, I also wanted to do this recently.

Maybe we should put the is_normalizable in a utils function, in case we'll need it sometimes in the future.

[JohnTitor]

Maybe we should put the is_normalizable in a utils function, in case we'll need it sometimes in the future.

It's reasonable, moved into utils.

[phansch]

@bors r+

[bors]

📌 Commit bf67fcf has been approved by phansch

[bors]

⌛ Testing commit bf67fcf with merge cfa0abb...

[bors]

💔 Test failed - status-appveyor

[phansch]

Huh, never saw this before. rustfmt fails:

error: couldn't read \\?\C:\projects\rust-clippy\tests\ui\crashes\..\auxiliary\use_self_macro.rs: The filename, directory name, or volume label syntax is incorrect. (os error 123)
 --> \\?\C:\projects\rust-clippy\tests\ui\crashes\ice-4671.rs:5:5
  |
5 | mod use_self_macro;
  |     ^^^^^^^^^^^^^^
rustfmt failed on C:\projects\rust-clippy\tests\ui\crashes\ice-4671.rs

Maybe move the auxiliary file into crashes, too?

[JohnTitor]

Oh, it seems so, moved it.

[phansch]

@bors r+ thanks!

[bors]

📌 Commit c6aeda7 has been approved by phansch

[bors]

⌛ Testing commit c6aeda7 with merge 2e8c3c3...

[bors]

☀️ Test successful - checks-travis, status-appveyor
Approved by: phansch
Pushing 2e8c3c3 to master...