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Associated lang items #70718

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ecstatic-morse opened this issue Apr 2, 2020 · 1 comment · Fixed by #72559
Closed

Associated lang items #70718

ecstatic-morse opened this issue Apr 2, 2020 · 1 comment · Fixed by #72559
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@ecstatic-morse
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A-associated-items Area: Associated items (types, constants & functions) A-lang-item Area: Language items C-cleanup Category: PRs that clean code up or issues documenting cleanup. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue.

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@ecstatic-morse
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Some associated items have a special meaning in the compiler, for example, Fn::Output and Future::Output. However, these associated types are often looked up by name, or worse by definition order. We should be using the lang item machinery for them.
@ecstatic-morse ecstatic-morse added C-enhancement Category: An issue proposing an enhancement or a PR with one. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. A-lang-item Area: Language items labels Apr 2, 2020
@ecstatic-morse ecstatic-morse self-assigned this Apr 2, 2020
@jonas-schievink jonas-schievink added C-cleanup Category: PRs that clean code up or issues documenting cleanup. and removed C-enhancement Category: An issue proposing an enhancement or a PR with one. labels Apr 2, 2020
@lcnr
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lcnr commented Apr 7, 2020

relevant for #70705

@jonas-schievink jonas-schievink added the A-associated-items Area: Associated items (types, constants & functions) label Apr 7, 2020
@Aaron1011 Aaron1011 mentioned this issue May 25, 2020
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bors added a commit to rust-lang-ci/rust that referenced this issue Jun 25, 2020
@bors
Auto merge of rust-lang#72559 - Aaron1011:feature/assoc-lang-items, r…
229e5b2 
…=oli-obk

Implement associated lang items

Fixes rust-lang#70718

This commit allows making associated items (e.g. associated functions
and types) into lang items via the `#[lang]` attribute. This allows such
items to be accessed directly, rather than by iterating over the parent
item's associated items.

I've added `FnOnce::Output` as a lang item, and updated one old usage to
use the new lang item. The remaining uses can be updated separately.
@bors bors closed this as completed in a13d467 Jun 25, 2020
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@ecstatic-morse ecstatic-morse

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A-associated-items Area: Associated items (types, constants & functions) A-lang-item Area: Language items C-cleanup Category: PRs that clean code up or issues documenting cleanup. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue.
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Implement associated lang items Aaron1011/rust
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@jonas-schievink @ecstatic-morse @lcnr