Warn about multiple conflicting #[repr] hints

[lambda-fairy]

Closes#34622

[rust-highfive]

r? @pnkfelix

(rust_highfive has picked a reviewer for you, use r? to override)

[Aatch]

I wonder if this should instead be a warning instead of an error? Also, @nagisa is the use of #[repr(C, u32)] in the failing test deliberate?

[nagisa]

@Aatch what do you mean/are you referring to?

[Aatch]

@nagisa one of the tests is failing, mir_adt_construction.rs because it uses #[repr(C, u32)]. You wrote the test, so I pinged you about it.

[lambda-fairy]

Okay, fixed the error in mir_adt_construction.rs. Lets see if Travis likes it now.

[nagisa]

Ah, no, I don’t think it was intentional.

[lambda-fairy]

I've switched to a warning instead.

Should we do a crater run with this patch? I'm curious as to which crates make this mistake in the wild.

[lambda-fairy]

Just noticed this weird test failure:

failures:
---- [pretty] pretty/conflicting-repr-hints.rs stdout ----
error: pretty-printed source does not match expected source
expected:
------------------------------------------
// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
#![allow(dead_code)]
#[repr(C)]
enum A { A, }
#[repr(u64)]
enum B { B, }
//~ WARNING conflicting representation hints
#[repr(C, u64)]
enum C { C, }
//~ WARNING conflicting representation hints
#[repr(u32, u64)]
enum D { D, }
#[repr(C, packed)]
struct E(i32);
fn main() { }
------------------------------------------
actual:
------------------------------------------
// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
#![allow(dead_code)]
#[repr(C)]
enum A { A, }
#[repr(u64)]
enum B { B, }
//~ WARNING conflicting representation hints
#[repr(C, u64)]
enum C { C, }
//~ WARNING conflicting representation hints
#[repr(u32, u64)]
enum D { D, }
#[repr(C, packed)]
struct E(i32);
fn main() { }
------------------------------------------

Anyone know what's going on here? The test seems to expect an extra space (??)

[bors]

☔ The latest upstream changes (presumably #35764) made this pull request unmergeable. Please resolve the merge conflicts.

[lambda-fairy]

I've rewritten the patch to use the HIR machinery. It should be ready to merge now.

Thanks @eddyb for your help on IRC!

[eddyb]

You should pick the first available number after the highest in use.

[lambda-fairy]

@eddyb I've changed the error code to the one after the last.

Should I squash the two commits, or leave them as-is?

[eddyb]

@lfairy Squashing/amending is preferred in such cases.

[lambda-fairy]

Sure, I've squashed it now.

[bors]

☔ The latest upstream changes (presumably #36049) made this pull request unmergeable. Please resolve the merge conflicts.

[lambda-fairy]

Rebased.

[bors]

☔ The latest upstream changes (presumably #36066) made this pull request unmergeable. Please resolve the merge conflicts.

[lambda-fairy]

Rebased again.

By the way: is anyone looking at this PR? It's been open for a while now, and I'd rather get it merged soon before the diagnostics system gets more churn.

[Aatch]

@bors r+

[bors]

📌 Commit e2e5807 has been approved by Aatch

[bors]

⌛ Testing commit e2e5807 with merge b96f323...

[bors]

💔 Test failed - auto-win-gnu-32-opt-rustbuild

[lambda-fairy]

Apparently someone else added a diagnostic code in the mean time 😢 Should be fixed now.

@Aatch re-r?

[eddyb]

@bors r=Aatch

[bors]

📌 Commit 42b75a5 has been approved by Aatch

[bors]

⌛ Testing commit 42b75a5 with merge 603d9cc...

[bors]

☀️ Test successful - auto-linux-32-nopt-t, auto-linux-32-opt, auto-linux-64-cargotest, auto-linux-64-cross-freebsd, auto-linux-64-debug-opt, auto-linux-64-nopt-t, auto-linux-64-opt, auto-linux-64-opt-rustbuild, auto-linux-64-x-android-t, auto-linux-cross-opt, auto-linux-musl-64-opt, auto-mac-32-opt, auto-mac-64-opt, auto-mac-64-opt-rustbuild, auto-mac-cross-ios-opt, auto-win-gnu-32-opt, auto-win-gnu-32-opt-rustbuild, auto-win-gnu-64-opt, auto-win-msvc-32-opt, auto-win-msvc-64-cargotest, auto-win-msvc-64-opt, auto-win-msvc-64-opt-rustbuild
Approved by: Aatch
Pushing 603d9cc to master...