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Raw Pointers are Constant PatKinds too#144573

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BoxyUwU:patkind_constant_ptr_docs
Jul 29, 2025
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Raw Pointers are Constant PatKinds too#144573
bors merged 1 commit intorust-lang:masterfrom
BoxyUwU:patkind_constant_ptr_docs

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@BoxyUwU BoxyUwU commented Jul 28, 2025 •
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raw pointers can be matched on with a const pattern:

const FOO: *const u8 = core::ptr::null();

fn foo(a: *const u8) {
  match a {
    FOO => (),
    _ => todo!(),
  }
}

as far as I can tell this is represented with a PatKind::Constant: https://github.com/rust-lang/rust/blob/master/compiler/rustc_mir_build/src/thir/pattern/const_to_pat.rs#L333-L337

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lcnr
lcnr reviewed Jul 28, 2025
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@BoxyUwU BoxyUwU force-pushed the patkind_constant_ptr_docs branch from 64fc4f6 to 2b11851 Compare July 28, 2025 09:13
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BoxyUwU commented Jul 28, 2025

@bors r=lcnr rollup

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📌 Commit 2b11851 has been approved by lcnr

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@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 Jul 28, 2025
RalfJung
RalfJung reviewed Jul 28, 2025
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compiler/rustc_middle/src/thir.rs
/// * integer, bool, char or float (represented as a valtree), which will be handled by
/// exhaustiveness to cover exactly its own value, similar to `&str`, but these values are
/// much simpler.
/// * raw pointers derived from integers, other raw pointers will have already resulted in an
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This will also be a valtree then.

Hm, that makes me wonder whether we shouldn't change the type here from mir::Const to something that enforces val-tree-ness... that was part of the goal of the big const pattern changes we did last year.

I don't know how the String case is represented though.

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Yeah I don't know about the String case :3 mir::Const does seem a bit funny to me too

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See follow-up at #144591.

samueltardieu added a commit to samueltardieu/rust that referenced this pull request Jul 28, 2025
@samueltardieu
Rollup merge of rust-lang#144573 - BoxyUwU:patkind_constant_ptr_docs,…
800f948 
… r=lcnr

Raw Pointers are Constant PatKinds too

raw pointers can be matched on with a const pattern:
```rust
const FOO: *const u8 = core::ptr::null();

fn foo(a: *const u8) {
  match a {
    FOO => (),
    _ => todo!(),
  }
}
```
as far as I can tell this is represented with a `PatKind::Constant`: https://github.com/rust-lang/rust/blob/master/compiler/rustc_mir_build/src/thir/pattern/const_to_pat.rs#L333-L337
@samueltardieu samueltardieu mentioned this pull request Jul 28, 2025
Closed
bors added a commit that referenced this pull request Jul 29, 2025
@bors
Auto merge of #144611 - samueltardieu:rollup-c57gj2t, r=samueltardieu
0b9f7b9 
Rollup of 11 pull requests

Successful merges:

 - #143289 (Remove `[T]::array_chunks(_mut)`)
 - #143883 (Add `--link-targets-dir` argument to linkchecker)
 - #144034 (tests: Test line number in debuginfo for diverging function calls)
 - #144236 (Add `core::mem::DropGuard`)
 - #144268 (Add method `find_ancestor_not_from_macro` and `find_ancestor_not_from_extern_macro` to supersede `find_oldest_ancestor_in_same_ctxt`)
 - #144303 (Consolidate staging for `rustc_private` tools)
 - #144539 (constify with_exposed_provenance)
 - #144569 (rustc-dev-guide subtree update)
 - #144573 (Raw Pointers are Constant PatKinds too)
 - #144578 (Ensure correct aligement of rustc_hir::Lifetime on platforms with lower default alignments.)
 - #144582 (fix `Atomic*::as_ptr` wording)

r? `@ghost`
`@rustbot` modify labels: rollup
Zalathar added a commit to Zalathar/rust that referenced this pull request Jul 29, 2025
@Zalathar
Rollup merge of rust-lang#144573 - BoxyUwU:patkind_constant_ptr_docs,…
89a8c20 
… r=lcnr

Raw Pointers are Constant PatKinds too

raw pointers can be matched on with a const pattern:
```rust
const FOO: *const u8 = core::ptr::null();

fn foo(a: *const u8) {
  match a {
    FOO => (),
    _ => todo!(),
  }
}
```
as far as I can tell this is represented with a `PatKind::Constant`: https://github.com/rust-lang/rust/blob/master/compiler/rustc_mir_build/src/thir/pattern/const_to_pat.rs#L333-L337
@Zalathar Zalathar mentioned this pull request Jul 29, 2025
Closed
Zalathar added a commit to Zalathar/rust that referenced this pull request Jul 29, 2025
@Zalathar
Rollup merge of rust-lang#144573 - BoxyUwU:patkind_constant_ptr_docs,…
639bb3a 
… r=lcnr

Raw Pointers are Constant PatKinds too

raw pointers can be matched on with a const pattern:
```rust
const FOO: *const u8 = core::ptr::null();

fn foo(a: *const u8) {
  match a {
    FOO => (),
    _ => todo!(),
  }
}
```
as far as I can tell this is represented with a `PatKind::Constant`: https://github.com/rust-lang/rust/blob/master/compiler/rustc_mir_build/src/thir/pattern/const_to_pat.rs#L333-L337
@Zalathar Zalathar mentioned this pull request Jul 29, 2025
Closed
Zalathar added a commit to Zalathar/rust that referenced this pull request Jul 29, 2025
@Zalathar
Rollup merge of rust-lang#144573 - BoxyUwU:patkind_constant_ptr_docs,…
8ebb05f 
… r=lcnr

Raw Pointers are Constant PatKinds too

raw pointers can be matched on with a const pattern:
```rust
const FOO: *const u8 = core::ptr::null();

fn foo(a: *const u8) {
  match a {
    FOO => (),
    _ => todo!(),
  }
}
```
as far as I can tell this is represented with a `PatKind::Constant`: https://github.com/rust-lang/rust/blob/master/compiler/rustc_mir_build/src/thir/pattern/const_to_pat.rs#L333-L337
@Zalathar Zalathar mentioned this pull request Jul 29, 2025
Closed
bors added a commit that referenced this pull request Jul 29, 2025
@bors
Auto merge of #144622 - Zalathar:rollup-1k3spo6, r=Zalathar
c471dec 
Rollup of 11 pull requests

Successful merges:

 - #143883 (Add `--link-targets-dir` argument to linkchecker)
 - #144236 (Add `core::mem::DropGuard`)
 - #144303 (Consolidate staging for `rustc_private` tools)
 - #144367 (Move dist-apple-various from x86_64 to aarch64)
 - #144539 (constify with_exposed_provenance)
 - #144569 (rustc-dev-guide subtree update)
 - #144573 (Raw Pointers are Constant PatKinds too)
 - #144575 (fixed typo chunks->as_chunks)
 - #144578 (Ensure correct aligement of rustc_hir::Lifetime on platforms with lower default alignments.)
 - #144582 (fix `Atomic*::as_ptr` wording)
 - #144616 (coverage: Regression test for "function name is empty" bug)

r? `@ghost`
`@rustbot` modify labels: rollup
@Zalathar Zalathar mentioned this pull request Jul 29, 2025
Merged
bors added a commit that referenced this pull request Jul 29, 2025
@bors
Auto merge of #144624 - Zalathar:rollup-w803jmq, r=Zalathar
5529041 
Rollup of 10 pull requests

Successful merges:

 - #143883 (Add `--link-targets-dir` argument to linkchecker)
 - #144236 (Add `core::mem::DropGuard`)
 - #144367 (Move dist-apple-various from x86_64 to aarch64)
 - #144539 (constify with_exposed_provenance)
 - #144569 (rustc-dev-guide subtree update)
 - #144573 (Raw Pointers are Constant PatKinds too)
 - #144575 (fixed typo chunks->as_chunks)
 - #144578 (Ensure correct aligement of rustc_hir::Lifetime on platforms with lower default alignments.)
 - #144582 (fix `Atomic*::as_ptr` wording)
 - #144616 (coverage: Regression test for "function name is empty" bug)

r? `@ghost`
`@rustbot` modify labels: rollup
@bors bors merged commit fce74ba into rust-lang:master Jul 29, 2025
10 checks passed
@rustbot rustbot added this to the 1.90.0 milestone Jul 29, 2025
rust-timer added a commit that referenced this pull request Jul 29, 2025
@rust-timer
Unrolled build for #144573
e868020 
Rollup merge of #144573 - BoxyUwU:patkind_constant_ptr_docs, r=lcnr

Raw Pointers are Constant PatKinds too

raw pointers can be matched on with a const pattern:
```rust
const FOO: *const u8 = core::ptr::null();

fn foo(a: *const u8) {
  match a {
    FOO => (),
    _ => todo!(),
  }
}
```
as far as I can tell this is represented with a `PatKind::Constant`: https://github.com/rust-lang/rust/blob/master/compiler/rustc_mir_build/src/thir/pattern/const_to_pat.rs#L333-L337
github-actions bot pushed a commit to rust-lang/rustc-dev-guide that referenced this pull request Jul 31, 2025
@bors
Auto merge of #144624 - Zalathar:rollup-w803jmq, r=Zalathar
c6e19e4 
Rollup of 10 pull requests

Successful merges:

 - rust-lang/rust#143883 (Add `--link-targets-dir` argument to linkchecker)
 - rust-lang/rust#144236 (Add `core::mem::DropGuard`)
 - rust-lang/rust#144367 (Move dist-apple-various from x86_64 to aarch64)
 - rust-lang/rust#144539 (constify with_exposed_provenance)
 - rust-lang/rust#144569 (rustc-dev-guide subtree update)
 - rust-lang/rust#144573 (Raw Pointers are Constant PatKinds too)
 - rust-lang/rust#144575 (fixed typo chunks->as_chunks)
 - rust-lang/rust#144578 (Ensure correct aligement of rustc_hir::Lifetime on platforms with lower default alignments.)
 - rust-lang/rust#144582 (fix `Atomic*::as_ptr` wording)
 - rust-lang/rust#144616 (coverage: Regression test for "function name is empty" bug)

r? `@ghost`
`@rustbot` modify labels: rollup
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