Coerce fields to the expected field type

[arielb1]

Fully fixes #31260.

This needs a crater run. I was supposed to do this last month but it slipped. Let's get this done.

[rust-highfive]

r? @pnkfelix

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[eddyb]

Started crater run.

[eddyb]

Crater report shows 0 regressions (ignoring network errors).

[eddyb]

cc @rust-lang/compiler

[nikomatsakis]

Discussed in the @rust-lang/compiler meeting briefly. If no regressions, seems like we should do this.

[eddyb]

@bors r+

[bors]

📌 Commit 7769c9a has been approved by eddyb

[bors]

⌛ Testing commit 7769c9a with merge 7a087743874c8f3bd906ff84806361af2b31cd6b...

[bors]

💔 Test failed - status-travis

[Mark-Simulacrum]

I suspect this is a spurious failure; it looks like the test will exit after 30 seconds via process::exit(1) -- which should probably be 0, really, I think.

[01:03:36] failures:
[01:03:36]
[01:03:36] ---- [run-pass] run-pass/tcp-stress.rs stdout ----
[01:03:36]
[01:03:36] error: test run failed!
[01:03:36] status: exit code: 1
[01:03:36] command: /checkout/obj/build/x86_64-unknown-linux-gnu/test/run-pass/tcp-stress.stage2-x86_64-unknown-linux-gnu
[01:03:36] stdout:
[01:03:36] ------------------------------------------
[01:03:36]
[01:03:36] ------------------------------------------
[01:03:36] stderr:
[01:03:36] ------------------------------------------
[01:03:36]
[01:03:36] ------------------------------------------
[01:03:36]
[01:03:36] thread '[run-pass] run-pass/tcp-stress.rs' panicked at 'explicit panic', /checkout/src/tools/compiletest/src/runtest.rs:2479
[01:03:36] note: Run with `RUST_BACKTRACE=1` for a backtrace.

[Mark-Simulacrum]

@bors retry

[bors]

⌛ Testing commit 7769c9a with merge 8b35998e0a2a3967eb0bc33fc37256692a93b6b2...

[bors]

💔 Test failed - status-appveyor

[Mark-Simulacrum]

@bors retry

#41006

[01:46:36] error: failed to remove: C:\projects\rust\build\i686-pc-windows-msvc\stage1-rustc\i686-pc-windows-msvc\release\rustc_driver.dll
[01:46:36]
[01:46:36] Caused by:
[01:46:36]   Access is denied. (os error 5)
[01:46:36] Build failed, waiting for other jobs to finish...
[01:46:40] error: build failed

[bors]

⌛ Testing commit 7769c9a with merge e72580c...

[bors]

☀️ Test successful - status-appveyor, status-travis
Approved by: eddyb
Pushing e72580c to master...