2018 edition allows ungated access to unstable crates #52489

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1. alexcrichton

   added this to the Rust 2018 Preview 2 milestone on Jul 18, 2018
2. alexcrichton

   added

   F-rust_2018_preview`#![feature(rust_2018_preview)]``#![feature(rust_2018_preview)]`

   on Jul 18, 2018
3. Mark-Simulacrum

   modified the milestones: Rust 2018 Preview 2, Rust 2018 Release Candidate on Jul 24, 2018
4. Mark-Simulacrum

   added

   I-nominated

   T-compilerRelevant to the compiler team, which will review and decide on the PR/issue.Relevant to the compiler team, which will review and decide on the PR/issue.

   on Jul 31, 2018
5. Mark-Simulacrum commented on Jul 31, 2018

   

   Mark-Simulacrum

   on Jul 31, 2018

   Member

   More actions

   @rust-lang/compiler Can we get some eyes on this, not necessarily to fix but at least to confirm that we believe a fix can be made and landed in time for RC? This is a hard-stop blocker for RC.
6. eddyb commented on Aug 1, 2018

   

   eddyb

   on Aug 1, 2018

   Last edited by eddyb

   Contributor

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   So this is generally harmless (you can't actually get anything from the unstable crate), except for it being a minor dead-code-but-allowed hazard.

   The culprit appears to be this special-casing:
   

   rust/src/librustc_resolve/resolve_imports.rs

   Lines 635 to 641 in e94df4a

   	// FIXME: Last path segment is treated specially in import resolution, so extern crate
   	// mode for absolute paths needs some special support for single-segment imports.
   	if module_path.len() == 1 && (module_path[0].name == keywords::CrateRoot.name() ||
   	module_path[0].name == keywords::Extern.name()) {
   	let is_extern = module_path[0].name == keywords::Extern.name() ||
   	(self.session.features_untracked().extern_absolute_paths &&
   	self.session.rust_2018());

   Which loads the crate (producing an error if no crate with that name exists), but doesn't record the resolution. So there's nothing to check - and presumably no way to use that broken import.

   The part that's missing is this (recording the import resolutions):
   

   rust/src/librustc_resolve/resolve_imports.rs

   Lines 878 to 884 in e94df4a

   	// Record what this import resolves to for later uses in documentation,
   	// this may resolve to either a value or a type, but for documentation
   	// purposes it's good enough to just favor one over the other.
   	self.per_ns(|this, ns| if let Some(binding) = result[ns].get().ok() {
   	let import = this.import_map.entry(directive.id).or_default();
   	import[ns] = Some(PathResolution::new(binding.def()));
   	});

   But the special-casing exits early:
   

   rust/src/librustc_resolve/resolve_imports.rs

   Lines 693 to 694 in e94df4a

   	let _ = self.try_define(directive.parent, target, TypeNS, binding);
   	return None;

   Expected minimal diff (between the two lines in the last snippet):

   let import = self.import_map.entry(directive.id).or_default(); 
   import[TypeNS] = Some(PathResolution::new(binding.def())); 
7. Mark-Simulacrum

   added a commit that references this issue on Aug 1, 2018

   Rollup merge of rust-lang#52930 - eddyb:issue-52489, r=cramertj

   ...

   This issue will close once commit af12be2 is merged into the 'main' branch.

   af12be2
8. emilyalbini

   added a commit that references this issue on Aug 1, 2018

   Rollup merge of rust-lang#52930 - eddyb:issue-52489, r=cramertj

   ...

   This issue will close once commit 2893bd0 is merged into the 'master' branch.

   2893bd0
9. bors

   closed this as completedin #52930on Aug 1, 2018
10. fmease

    added

    A-edition-2018Area: The 2018 editionArea: The 2018 edition

    on Dec 21, 2024