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bors 02c7a5921e Auto merge of #113169 - oli-obk:tait_must_be_constrained_if_in_sig, r=lcnr
Tait must be constrained if in sig

r? `@compiler-errors`

kind of reverts https://github.com/rust-lang/rust/pull/62423, but that PR only removed cycles in cases that we want to forbid now anyway.

see https://rust-lang.zulipchat.com/#narrow/stream/315482-t-compiler.2Fetc.2Fopaque-types/topic/lcnr.20oli.20meeting/near/370712246 for related discussion and motivating example

a TAIT showing up in a signature doesn't just mean it can register a hidden type, but that it must.

This is the [design the types team decided upon](https://hackmd.io/QOsEaEJtQK-XDS_xN4UyQA#Proposal-preferred) for the following reasons

* avoids a hypothetical situation where getting smarter in trait solving could cause new cycle errors or new inference errors to show up, where today something is treated as opaque.
* avoids having the situation where a (minor?) change to a function body causes an error, because its TAIT usage suddenly isn't "opaque enough" anymore.
* avoids having to explain why in some cases you need to put a Tait into a tiny module together with its defining usages. Now you basically gotta always do this, the moment a Tait is in a signature that isn't in the defining scope.
* avoids false-cycle errors
* anything diverging from this pattern needs to either
    * move the TAIT declaration and defining function into their own helper sub module
    * use the attributes we'll provide in the future to explicitly opt in or out of being in the defining scope

fixes #117861

reverts #125362 cc `@Nilstrieb` `@joboet`
2024-06-12 09:00:37 +00:00
.github CI: remove Setup Python action 2024-06-07 11:26:36 +02:00
.reuse std: move Once implementations to sys 2024-03-12 15:41:06 +01:00
compiler Add a fn main() {} to a doctest to prevent the test from being wrapped in a fn main() {} body 2024-06-12 08:53:59 +00:00
library Require any function with a tait in its signature to actually constrain a hidden type 2024-06-12 08:53:59 +00:00
LICENSES Add missing CC-BY-SA-4.0. 2023-11-27 11:03:53 +00:00
src Auto merge of #126290 - weihanglo:update-cargo, r=weihanglo 2024-06-12 06:51:07 +00:00
tests Require any function with a tait in its signature to actually constrain a hidden type 2024-06-12 08:53:59 +00:00
.editorconfig Only use max_line_length = 100 for *.rs 2023-07-10 15:18:36 -07:00
.git-blame-ignore-revs Ignore compiletest test directive migration commits 2024-02-22 18:55:02 +00:00
.gitattributes Rename config.toml.example to config.example.toml 2023-03-11 14:10:00 -08:00
.gitignore don't globally ignore rustc-ice files 2023-09-16 09:44:44 +02:00
.gitmodules refactor: add rustc-perf submodule to src/tools 2024-05-20 14:56:49 +00:00
.mailmap Rollup merge of #123873 - cuviper:mailmap, r=lqd 2024-04-13 00:18:47 -04:00
Cargo.lock run-make-support: bump version 2024-06-11 09:14:28 +00:00
Cargo.toml Remove the expand-yaml-anchors tool 2024-04-29 21:33:17 +02:00
CODE_OF_CONDUCT.md Remove the code of conduct; instead link https://www.rust-lang.org/conduct.html 2019-10-05 22:55:19 +02:00
config.example.toml config.example.toml: minor improves 2024-06-07 19:41:37 +02:00
configure Ensure ./configure works when configure.py path contains spaces 2024-02-16 18:57:22 +00:00
CONTRIBUTING.md fix: Update CONTRIBUTING.md recommend -> recommended 2023-11-16 23:57:09 +05:30
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INSTALL.md chore: fix some comments 2024-03-27 22:32:53 +08:00
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LICENSE-MIT LICENSE-MIT: Remove inaccurate (misattributed) copyright notice 2017-07-26 16:51:58 -07:00
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RELEASES.md Add release notes for 1.79.0 2024-06-09 12:31:12 -04:00
rust-bors.toml Increase timeout for new bors bot 2024-03-13 08:31:07 +01:00
rustfmt.toml Explain why tests/ui-fulldeps/ is unformatted. 2024-06-04 14:15:45 +10:00
triagebot.toml Autolabel run-make tests, remind to update tracking issue 2024-06-09 15:52:41 +00:00
x Make x capable of resolving symlinks 2023-10-14 17:53:33 +03:00
x.ps1 use & instead of start-process in x.ps1 2023-12-09 09:46:16 -05:00
x.py Fix recent python linting errors 2023-08-02 04:40:28 -04:00

This is the main source code repository for Rust. It contains the compiler, standard library, and documentation.

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