Moving some code around results in linking error with incremental comp

[sgrif]

I've had this happen 3 times now today. It's fixed by cargo clean, so is not a critical issue, but still is a moderately interesting incremental compilation bug. The change was moving the trait query_dsl::OffsetDsl to query_dsl::methods::OffsetDsl. The code in question that is failing was importing OffsetDsl::offset from diesel::prelude instead, the x.offset is now resolving to query_dsl::QueryDsl::offset, which simply calls OffsetDsl::offset, and is exported from prelude.

Anyway, this is the error
and the patch that caused it is https://gist.github.com/sgrif/8bb17b2a143d482e060fc3fd08705067

rustc --version: rustc 1.24.0-nightly (73bca2b 2017-11-28)

[michaelwoerister]

Heh, you might have provided a neat regression test for #46427 :) It sounds like it might be the same underlying problem.

[michaelwoerister]

I'm having a hard time reproducing this. Do you have two consecutive commits somewhere that trigger the problem?

[sgrif]

Not off-hand, but I can try to recreate the state things were in when I noticed this on a branch.

[michaelwoerister]

That would be awesome.

[sgrif]

I ran into a semi-related case today (sorry, these repro steps require libpq to be installed):

• Check out the sg-bug-repro branch of Diesel. https://github.com/diesel-rs/diesel/tree/sg-bug-repro
• cd examples/postgres/all_about_inserts
• EXPORT CARGO_INCREMENTAL=1
• cargo test (it'll probably fail but that doesn't matter)
• Change this line to unwrap
• cargo test

[michaelwoerister]

Thanks, that's very helpful!

[steveklabnik]

Triage:

@sgrif have you seen this bug lately?