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Use const-checking to forbid use of unstable features in const-stable functions #76807

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merged 6 commits into from
Sep 22, 2020

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ecstatic-morse
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First step towards #76618.

Currently this code isn't ever hit because qualify_min_const_fn runs first and catches pretty much everything. One exception is const_precise_live_drops, which does not use the newly added code since it runs as part of a separate pass.

Also contains some unrelated refactoring, which is split into separate commits.

r? @oli-obk

@rust-highfive rust-highfive added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Sep 16, 2020
@ecstatic-morse ecstatic-morse force-pushed the const-checking-staged-api branch from 589e285 to abc7167 Compare September 16, 2020 21:19
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oli-obk commented Sep 17, 2020

This is a good safety net for the actual changes!

@bors r+

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bors commented Sep 17, 2020

📌 Commit abc7167 has been approved by oli-obk

@bors bors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Sep 17, 2020
Dylan-DPC-zz pushed a commit to Dylan-DPC-zz/rust that referenced this pull request Sep 19, 2020
…d-api, r=oli-obk

Use const-checking to forbid use of unstable features in const-stable functions

First step towards rust-lang#76618.

Currently this code isn't ever hit because `qualify_min_const_fn` runs first and catches pretty much everything. One exception is `const_precise_live_drops`, which does not use the newly added code since it runs as part of a separate pass.

Also contains some unrelated refactoring, which is split into separate commits.

r? @oli-obk
Dylan-DPC-zz pushed a commit to Dylan-DPC-zz/rust that referenced this pull request Sep 19, 2020
…d-api, r=oli-obk

Use const-checking to forbid use of unstable features in const-stable functions

First step towards rust-lang#76618.

Currently this code isn't ever hit because `qualify_min_const_fn` runs first and catches pretty much everything. One exception is `const_precise_live_drops`, which does not use the newly added code since it runs as part of a separate pass.

Also contains some unrelated refactoring, which is split into separate commits.

r? @oli-obk
Dylan-DPC-zz pushed a commit to Dylan-DPC-zz/rust that referenced this pull request Sep 19, 2020
…d-api, r=oli-obk

Use const-checking to forbid use of unstable features in const-stable functions

First step towards rust-lang#76618.

Currently this code isn't ever hit because `qualify_min_const_fn` runs first and catches pretty much everything. One exception is `const_precise_live_drops`, which does not use the newly added code since it runs as part of a separate pass.

Also contains some unrelated refactoring, which is split into separate commits.

r? @oli-obk
Dylan-DPC-zz pushed a commit to Dylan-DPC-zz/rust that referenced this pull request Sep 21, 2020
…d-api, r=oli-obk

Use const-checking to forbid use of unstable features in const-stable functions

First step towards rust-lang#76618.

Currently this code isn't ever hit because `qualify_min_const_fn` runs first and catches pretty much everything. One exception is `const_precise_live_drops`, which does not use the newly added code since it runs as part of a separate pass.

Also contains some unrelated refactoring, which is split into separate commits.

r? @oli-obk
ecstatic-morse added a commit to ecstatic-morse/rust that referenced this pull request Sep 22, 2020
…d-api, r=oli-obk

Use const-checking to forbid use of unstable features in const-stable functions

First step towards rust-lang#76618.

Currently this code isn't ever hit because `qualify_min_const_fn` runs first and catches pretty much everything. One exception is `const_precise_live_drops`, which does not use the newly added code since it runs as part of a separate pass.

Also contains some unrelated refactoring, which is split into separate commits.

r? @oli-obk
bors added a commit to rust-lang-ci/rust that referenced this pull request Sep 22, 2020
…atic-morse

Rollup of 13 pull requests

Successful merges:

 - rust-lang#72734 (Reduce duplicate in liballoc reserve error handling)
 - rust-lang#76131 (Don't use `zip` to compare iterators during pretty-print hack)
 - rust-lang#76150 (Don't recommend ManuallyDrop to customize drop order)
 - rust-lang#76275 (Implementation of Write for some immutable ref structs)
 - rust-lang#76489 (Add explanation for E0756)
 - rust-lang#76581 (do not ICE on bound variables, return `TooGeneric` instead)
 - rust-lang#76655 (Make some methods of `Pin` unstable const)
 - rust-lang#76783 (Only get ImplKind::Impl once)
 - rust-lang#76807 (Use const-checking to forbid use of unstable features in const-stable functions)
 - rust-lang#76888 (use if let instead of single match arm expressions)
 - rust-lang#76914 (extend `Ty` and `TyCtxt` lints to self types)
 - rust-lang#77022 (Reduce boilerplate for BytePos and CharPos)
 - rust-lang#77032 (lint missing docs for extern items)

Failed merges:

r? `@ghost`
@bors bors merged commit 60b9901 into rust-lang:master Sep 22, 2020
@rustbot rustbot added this to the 1.48.0 milestone Sep 22, 2020
ecstatic-morse added a commit to ecstatic-morse/rust that referenced this pull request Sep 22, 2020
…tor, r=oli-obk

Remove `qualify_min_const_fn`

~~Blocked on rust-lang#76807 (the first six commits).~~

With this PR, all checks in `qualify_min_const_fn` are replicated in `check_consts`, and the former is no longer invoked. My goal was to have as few changes to test output as possible, since making sweeping changes to the code *while* doing big batches of diagnostics updates turned out to be a headache. To this end, there's a few `HACK`s in `check_consts` to achieve parity with `qualify_min_const_fn`.

The new system that replaces `is_min_const_fn` is referred to as "const-stability"  My end goal for the const-stability rules is this:
* Const-stability is only applicable to functions defined in `staged_api` crates.
* All functions not marked `rustc_const_unstable` are considered "const-stable".
    - NB. This is currently not implemented. `#[unstable]` functions are also const-unstable. This causes problems when searching for feature gates.
    - All "const-unstable" functions have an associated feature gate
* const-stable functions can only call other const-stable functions
     - `allow_internal_unstable` can be used to circumvent this.
* All const-stable functions are subject to some additional checks (the ones that were unique to `qualify_min_const_fn`)

The plan is to remove each `HACK` individually in subsequent PRs. That way, changes to error message output can be reviewed in isolation.
bors added a commit to rust-lang-ci/rust that referenced this pull request Sep 23, 2020
…r, r=oli-obk

Remove `qualify_min_const_fn`

~~Blocked on rust-lang#76807 (the first six commits).~~

With this PR, all checks in `qualify_min_const_fn` are replicated in `check_consts`, and the former is no longer invoked. My goal was to have as few changes to test output as possible, since making sweeping changes to the code *while* doing big batches of diagnostics updates turned out to be a headache. To this end, there's a few `HACK`s in `check_consts` to achieve parity with `qualify_min_const_fn`.

The new system that replaces `is_min_const_fn` is referred to as "const-stability"  My end goal for the const-stability rules is this:
* Const-stability is only applicable to functions defined in `staged_api` crates.
* All functions not marked `rustc_const_unstable` are considered "const-stable".
    - NB. This is currently not implemented. `#[unstable]` functions are also const-unstable. This causes problems when searching for feature gates.
    - All "const-unstable" functions have an associated feature gate
* const-stable functions can only call other const-stable functions
     - `allow_internal_unstable` can be used to circumvent this.
* All const-stable functions are subject to some additional checks (the ones that were unique to `qualify_min_const_fn`)

The plan is to remove each `HACK` individually in subsequent PRs. That way, changes to error message output can be reviewed in isolation.
@ecstatic-morse ecstatic-morse deleted the const-checking-staged-api branch October 6, 2020 01:42
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5 participants