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Attributes starting with rustc_ are supposed to be gated, but they are not always gated #62116

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petrochenkov opened this issue Jun 25, 2019 · 0 comments · Fixed by #62133
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Attributes starting with rustc_ are supposed to be gated, but they are not always gated #62116

petrochenkov opened this issue Jun 25, 2019 · 0 comments · Fixed by #62133
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@petrochenkov
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A-attributes Area: #[attributes(..)] A-resolve Area: Path resolution A-stability Area: issues related to #[stable] and #[unstable] attributes themselves. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. T-lang Relevant to the language team, which will review and decide on the PR/issue.

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@petrochenkov
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Of course, the specific known built-in attributes like #[rustc_copy_clone_marker] are feature gated, but the rustc_* names are not reserved in general.
As a result, you can easily create a procedural macro attribute starting with rustc_.

As a result, introduction of a new built-in attribute is technically a breaking change even if the attribute starts with rustc_.

Q: Why is introduction of a new built-in attribute a breaking change.
A: Because built-in attributes will conflict with any other attributes in scope having the same name (see #53913 (comment) for some technical details).

Possible solutions:

  • Reserve (feature gate) any attributes starting with rustc_, including macros, run crater and see what happens.
  • Do nothing, this is not a big deal.
    • Third party attribute names are unlikely to start with rustc_.
    • We are going to add new non-rustc_* built-in attributes anyway and go through the same technically breaking changes in process.
@petrochenkov petrochenkov self-assigned this Jun 25, 2019
@petrochenkov petrochenkov added A-attributes Area: #[attributes(..)] A-resolve Area: Path resolution A-stability Area: issues related to #[stable] and #[unstable] attributes themselves. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. T-lang Relevant to the language team, which will review and decide on the PR/issue. labels Jun 25, 2019
@petrochenkov petrochenkov mentioned this issue Jun 25, 2019
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bors added a commit that referenced this issue Jun 25, 2019
@bors
Auto merge of #62133 - petrochenkov:norustc, r=<try>
8ec8125 
Feature gate `rustc` attributes harder

cc #62116
Centril added a commit to Centril/rust that referenced this issue Jul 1, 2019
@Centril
Rollup merge of rust-lang#62133 - petrochenkov:norustc, r=eddyb
e590677 
Feature gate `rustc` attributes harder

Fixes rust-lang#62116
Manishearth added a commit to Manishearth/rust that referenced this issue Jul 2, 2019
@Manishearth
Rollup merge of rust-lang#62133 - petrochenkov:norustc, r=eddyb
62b38c1 
Feature gate `rustc` attributes harder

Fixes rust-lang#62116
Mark-Simulacrum added a commit to Mark-Simulacrum/rust that referenced this issue Jul 3, 2019
@Mark-Simulacrum
Rollup merge of rust-lang#62133 - petrochenkov:norustc, r=eddyb
351442b 
Feature gate `rustc` attributes harder

Fixes rust-lang#62116
Centril added a commit to Centril/rust that referenced this issue Jul 4, 2019
@Centril
Rollup merge of rust-lang#62133 - petrochenkov:norustc, r=eddyb
0668f38 
Feature gate `rustc` attributes harder

Fixes rust-lang#62116
Mark-Simulacrum added a commit to Mark-Simulacrum/rust that referenced this issue Jul 4, 2019
@Mark-Simulacrum
Rollup merge of rust-lang#62133 - petrochenkov:norustc, r=eddyb
b5246fd 
Feature gate `rustc` attributes harder

Fixes rust-lang#62116
Mark-Simulacrum added a commit to Mark-Simulacrum/rust that referenced this issue Jul 4, 2019
@Mark-Simulacrum
Rollup merge of rust-lang#62133 - petrochenkov:norustc, r=eddyb
2a374b0 
Feature gate `rustc` attributes harder

Fixes rust-lang#62116
Centril added a commit to Centril/rust that referenced this issue Jul 5, 2019
@Centril
Rollup merge of rust-lang#62133 - petrochenkov:norustc, r=eddyb
de03018 
Feature gate `rustc` attributes harder

Fixes rust-lang#62116
Centril added a commit to Centril/rust that referenced this issue Jul 5, 2019
@Centril
Rollup merge of rust-lang#62133 - petrochenkov:norustc, r=eddyb
51454fd 
Feature gate `rustc` attributes harder

Fixes rust-lang#62116
Centril added a commit to Centril/rust that referenced this issue Jul 5, 2019
@Centril
Rollup merge of rust-lang#62133 - petrochenkov:norustc, r=eddyb
0224532 
Feature gate `rustc` attributes harder

Fixes rust-lang#62116
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A-attributes Area: #[attributes(..)] A-resolve Area: Path resolution A-stability Area: issues related to #[stable] and #[unstable] attributes themselves. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. T-lang Relevant to the language team, which will review and decide on the PR/issue.
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Feature gate rustc attributes harder petrochenkov/rust
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