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async move breaks doc tests #59313
Description
Steps to reproduce:
- Create a library project with the following contents in
lib.rs:
//! ```
//! #![feature(async_await)]
//!
//! fn foo() {
//! drop(async move {});
//! }
//! ```
- Run tests:
repro master $ cargo --version
cargo 1.35.0-nightly (0e35bd8af 2019-03-13)
repro master $ rustc --version
rustc 1.35.0-nightly (3eb4890df 2019-03-19)
repro master $ cargo test
Finished dev [unoptimized + debuginfo] target(s) in 0.00s
Running target/debug/deps/repro-0e401502cf52c662
running 0 tests
test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out
Doc-tests repro
running 1 test
test src/lib.rs - (line 1) ... FAILED
failures:
failures:
src/lib.rs - (line 1)
test result: FAILED. 0 passed; 1 failed; 0 ignored; 0 measured; 0 filtered out
error: test failed, to rerun pass '--doc'- Now delete the
moveinsideasync move {}:
//! ```
//! #![feature(async_await)]
//!
//! fn foo() {
//! drop(async {});
//! }
//! ```
- Run tests again:
repro master $ cargo test
Compiling repro v0.1.0 (/home/stjepan/work/repro)
Finished dev [unoptimized + debuginfo] target(s) in 0.25s
Running target/debug/deps/repro-0e401502cf52c662
running 0 tests
test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out
Doc-tests repro
running 1 test
test src/lib.rs - (line 1) ... ok
test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out
Activity
nikomatsakis commentedon Apr 16, 2019
This seems to work outside of rustdoc
nikomatsakis commentedon Apr 16, 2019
Marking as blocking for async await stabilization pending some investigation.
cc @rust-lang/rustdoc -- can you all give any tips to try and gain insight into what error is occurring etc?
GuillaumeGomez commentedon Apr 17, 2019
Can you give a try to:
But beyond that, I'm wondering if it isn't just a missing flag or something along the line?
Maybe you have other ideas @QuietMisdreavus ?
QuietMisdreavus commentedon Apr 17, 2019
I spent some time yesterday poking at this, and it seems like it's failing somewhere in the pre-parsing of the doctest. Some time around the part where it parses the
movekeyword, it just... dies. I'm having trouble pinning down exactly where (and how) it fails, since it's not panicking, and setting-Z treat-err-as-bug(which i have to modify the code to do since we usually don't pass that into doctests) makes it fail at an earlier spot.nikomatsakis commentedon Apr 17, 2019
I've sometimes seen problems around
FatalError.raise()QuietMisdreavus commentedon Apr 17, 2019
Funny you should say that... It looks like one of those is being hit when processing this sample:
rust/src/libsyntax/parse/parser.rs
Lines 791 to 792 in 8260e96
It doesn't seem to hit this when compiling regularly, though.
QuietMisdreavus commentedon Apr 17, 2019
I think i've figured it out. The "pre-parse" step of doctest execution runs the parser separately from the later execution of it. In this run, the "default edition" is never set, so libsyntax assumes everything is being run under Rust 2015. This causes it to fail when parsing the
async moveblock. What's confusing is how this has never been a problem until now... 🤔QuietMisdreavus commentedon Apr 18, 2019
I've got a PR posted that should fix this: #60065
Nemo157 commentedon Apr 18, 2019
Hmm, I was going to suggest that might be the issue, but I tried a test containing
async { let foo = 5; }(which fails to compile on edition 2015) and that works fine (unsurprisingly sincefuturesuse a lot of doc-tests containing something similar).QuietMisdreavus commentedon Apr 18, 2019
Plain
asyncblocks probably pass in the current nightly because they fail after the initial parse, or perhaps they bubble up a single error fromparse_iteminstead of emitting it directly, which causes rustdoc to stop parsing and continue creating the doctest. The difference withasync moveblocks is that they use a keyword that exists in 2015, which causes it to attempt parsing a closure (instead of a struct expression), so it totally fails to parse instead of just creating a real expression that would fail a later check.Auto merge of #60065 - QuietMisdreavus:async-move-doctests, r=ollie27