Make search path debugging info! for easier debugging

[Zoxc]

No description provided.

[rust-highfive]

r? @nikomatsakis

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[nikomatsakis]

Hmm. I have no particular objection to this, but I do wonder about the "stability" of said messages. Perhaps we want some explicit text stating that we make no promises here?

cc @eddyb -- seems related to things we were discussing before about compiler's debug logs though =)

[eddyb]

We need to change the builtin log crate to use RUSTC_LOG instead of RUST_LOG before we add more of these - maybe it can be done in rustc_driver specifically.

[nikomatsakis]

@eddyb

We need to change the builtin log crate to use RUSTC_LOG instead of RUST_LOG before we add more of these - maybe it can be done in rustc_driver specifically.

I think I agree. I have no idea how to do this though. :)

(Haven't looked at how logging works in a while; it's been refactored quite a bit I think?)

[bors]

☔ The latest upstream changes (presumably #37082) made this pull request unmergeable. Please resolve the merge conflicts.

[nikomatsakis]

@Zoxc

For context, @eddyb has been pointing out that if you do RUST_LOG=... cargo run, changes are that you intend to this RUST_LOG to apply to program you are running, not the compiler. For now, since the majority of logs are debug and compiled out, this isn't much of an issue, but if we're going to expand infos -- and in particular if we're going to expand to include infos that are targeting end-users -- this becomes a bigger concern. Especially since it could become part of a de facto stable interface; I know that I myself never considered the possibility that people would rely on the RUST_LOG behavior of rustc until recently. Anyway, TL;DR is that at minimum we'd rather change to RUSTC_LOG before we add any more output into rustc. Would you be up for pursuing such a patch?

[nikomatsakis]

OK, I'm going to close this PR in light of @eddyb's comment in any case. @Zoxc let me know if you're up to rename RUST_LOG =)