romaji fails to build on beta,

@uzimith

With a few minutes of time invested I wasn't able to narrow this down to a smaller example that still succeeded on stable.

! 
Nov 02 07:32:11.418 INFO kablam! error[E0282]: type annotations needed
Nov 02 07:32:11.418 INFO kablam!   --> src/romaji.rs:80:24
Nov 02 07:32:11.418 INFO kablam!    |
Nov 02 07:32:11.418 INFO kablam! 80 |                 x if x.is_youon() && buffer.is_katakana() => {
Nov 02 07:32:11.419 INFO kablam!    |                        ^^^^^^^^ cannot infer type for `T`
Nov 02 07:32:11.419 INFO kablam!    |
Nov 02 07:32:11.419 INFO kablam!    = note: type must be known at this point

cc @rust-lang/libs

Minimized:

struct S;

impl S {
    fn method(&self) -> bool {
        unimplemented!()
    }
}

fn get<T>() -> T {
    unimplemented!()
}

fn main() {
    match get() {
        x if x.method() => {}
        &S => {}
    }
}

@rust-lang/compiler because this doesn't look to be caused by a library change.

Hmm I wonder if this is some sort of bad interaction between 1. the new way to do pat variables in guards (which is activated by NLL) and 2. Method lookup and/or autoref...

... but this test isn’t asking for the 2018 edition, right? (I think we are still building the old style MIR if you don’t request NLL. But maybe that changed ...)

This can be caused by the typeck order. To make this work, all arms' patterns must be checked before any guards are.

This was injected between rustc 1.31.0-nightly (46880f4 2018-10-15) and rustc 1.31.0-nightly (bef62cc 2018-10-16)

Log of bors commits in that time in the details block

Details

% git log 46880f4..bef62cc --author bors --format=oneline
bef62cc Auto merge of #54486 - orium:obligation-forest-graphviz, r=nikomatsakis
8a7048b Auto merge of #54251 - varkor:silence-bad_style, r=Manishearth
99ab2f4 Auto merge of #54937 - alexcrichton:update-stdsimd, r=nikomatsakis
5ea8eb5 Auto merge of #55067 - ljedrz:generic_iterator_related_improvements, r=petrochenkov
df0d6ad Auto merge of #55023 - euclio:llvm-error-handler, r=cuviper

Hmm this line in the description of #55067 set off some alarm bells in my head:

typeck: don't collect into a vector when unnecessary

Auto merge of #55893 - pnkfelix:issue-55810-beta-backport-of-pr-55819…

Fixed by #55893?

Confirmed fixed as of nightly-2018-11-12 -- rustc 1.32.0-nightly (ca79ecd 2018-11-11) -- and rustc 1.31.0-beta.9 (c341a59 2018-11-12).

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romaji fails to build on beta, #55810

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romaji fails to build on beta, #55810

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dtolnay commented on Nov 9, 2018

dtolnay commented on Nov 9, 2018

pnkfelix commented on Nov 9, 2018

eddyb commented on Nov 9, 2018

pnkfelix commented on Nov 9, 2018

pnkfelix commented on Nov 9, 2018

goffrie commented on Nov 14, 2018

dtolnay commented on Nov 14, 2018

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