handle ConstValue::ByRef in relate #71018
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| = note: expected struct `Const<ByRef { alloc: Allocation { bytes: [3, 0, 0, 0, 0, 0, 0, 0], relocations: Relocations(SortedMap { data: [] }), undef_mask: UndefMask { blocks: [255], len: Size { raw: 8 } }, size: Size { raw: 8 }, align: Align { pow2: 3 }, mutability: Not, extra: () }, offset: Size { raw: 0 } }: [usize; 1]>` | ||
| found struct `Const<ByRef { alloc: Allocation { bytes: [4, 0, 0, 0, 0, 0, 0, 0], relocations: Relocations(SortedMap { data: [] }), undef_mask: UndefMask { blocks: [255], len: Size { raw: 8 } }, size: Size { raw: 8 }, align: Align { pow2: 3 }, mutability: Not, extra: () }, offset: Size { raw: 0 } }: [usize; 1]>` |
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I have a WIP branch where I make this print the actual values, I think we should wait for that, so that we can actually see it in action.
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🤷♂️ don't think that waiting is worth it if this is otherwise ready.
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It's not ready, because we can't read the error message.
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We already emit this error message rn. This PR only prevents correct programs from failing with it.
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That branch I mentioned is now a PR: #71232.
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src/librustc_middle/ty/relate.rs
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| let a_destructured = tcx.destructure_const(param_env.and(a)); | ||
| let b_destructured = tcx.destructure_const(param_env.and(b)); | ||
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| // Both the variant and each field have to be equal. | ||
| if a_destructured.variant == b_destructured.variant { | ||
| for (a_field, b_field) in | ||
| a_destructured.fields.iter().zip(b_destructured.fields.iter()) | ||
| { | ||
| relation.consts(a_field, b_field)?; |
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@oli-obk @matthewjasper What do you think of this use of destructure_const?
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destructure_const panics if the type isn't an array, adt or tuple, so it looks incorrect to not have a check on the type.
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it is. breaks with #63322
currently working on this
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It should allow closures as well, IMO, although I'm not sure closures should be considered structurally matcheable...
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Should be fixed, don't know if there are other types which have ConstValue::ByRef and should work rn.
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Oh yeah you can't have closures in a const type, so you can mark closures as not structurally matcheable.
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Wait, hang on, it can't be ty::Closure, maybe you were still talking about dyn Trait.
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both examples in #63322 end up relying on &dyn Trait afaict
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src/librustc_middle/ty/relate.rs
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| // FIXME(const_generics): There are probably some `TyKind`s | ||
| // which should be handled here. | ||
| _ => Err(TypeError::ConstMismatch(expected_found(relation, &a, &b))), |
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I can't think of any, at least out of the types we allow. You should use at least delay_span_bug, because returning Err indicates that they're definitely not equal (which may allow e.g. overlapping impls).
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👌 should relate_consts only be called for types which are structural match?
Is structural match implemented for &?
i.e. should this work
#![feature(const_generics)]
struct A<const N: &'static ()>;
fn main() {
let _ = A::<{&()}>;
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Yes, it should, but it's blocked on one of @oli-obk's PRs.
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Blocking on #71018 (comment). |
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ty/print: pretty-print constant aggregates (arrays, tuples and ADTs). Oddly enough, we don't have any UI tests showing this off in types, only `mir-opt` tests. However, the pretty form should show up in the test output diff of rust-lang#71018, if this PR is merged first. <hr/> Examples of before/after: |`Option<bool>`| |:-:| |`{transmute(0x01): std::option::Option<bool>}`| | :sparkles: ↓↓↓ :sparkles: | |`std::option::Option::<bool>::Some(true)`| | `RawVec<u32>` | |:-:| | `ByRef { alloc: Allocation { bytes: [4, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0], relocations: Relocations(SortedMap { data: [] }), undef_mask: UndefMask { blocks: [65535], len: Size { raw: 16 } }, size: Size { raw: 16 }, align: Align { pow2: 3 }, mutability: Not, extra: () }, offset: Size { raw: 0 } }: alloc::raw_vec::RawVec::<u32>`| | :sparkles: ↓↓↓ :sparkles: | |`alloc::raw_vec::RawVec::<u32> { ptr: std::ptr::Unique::<u32> { pointer: {0x4 as *const u32}, _marker: std::marker::PhantomData::<u32> }, cap: 0usize, alloc: std::alloc::Global }`| <hr/> This PR is a prerequisite for rust-lang#61486, *sort of*, in that we need to be able to pretty-print values in order to even consider how we might mangle them. We still don't have pretty-printing for constants of reference types, @oli-obk has the necessary support logic in a PR but I didn't want to interfere with that. <hr/> Each commit should be reviewed separately, as I've fixed a couple deficiencies along the way. r? @oli-obk cc @rust-lang/wg-mir-opt @varkor @yodaldevoid
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I think this is unblocked now since the fore-mentioned PR has been merged, maybe this will need a rebase? |
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Your PR failed (pretty log, raw log). Through arcane magic we have determined that the following fragments from the build log may contain information about the problem. Click to expand the log.I'm a bot! I can only do what humans tell me to, so if this was not helpful or you have suggestions for improvements, please ping or otherwise contact |
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Should be ready for merge ✨ |
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| --> $DIR/different_byref.rs:8:9 | ||
| | | ||
| LL | x = Const::<{ [4] }> {}; | ||
| | ^^^^^^^^^^^^^^^^^^^ expected `3usize`, found `4usize` |
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Only mildly related to this PR
@rust-lang/wg-const-eval we could consider collecting all spans that lead to a value during const eval and thus allow each byte in the final constant to have its own spans for diagnostics. Then we can report a sort of backtrace for values. Though I fear that will cause quite some overhead, even if we only need to do it in the current crate and not serialize it to metadata (so ClearCrossCrate).
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That would be more advanced than what we do for type aliases, heh.
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☔ The latest upstream changes (presumably #71707) made this pull request unmergeable. Please resolve the merge conflicts. |
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@bors r+ |
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📌 Commit a08bccb has been approved by |
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handle ConstValue::ByRef in relate fixes rust-lang#68615 r? @eddyb
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handle ConstValue::ByRef in relate fixes rust-lang#68615 r? @eddyb
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⌛ Testing commit a08bccb with merge b6e7b292fff458a6728a49e39a114a5b00678970... |
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@bors retry yield |
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Rollup of 5 pull requests Successful merges: - rust-lang#71018 (handle ConstValue::ByRef in relate) - rust-lang#71758 (Remove leftover chalk types) - rust-lang#71760 (Document unsafety for `*const T` and `*mut T`) - rust-lang#71761 (doc: reference does not exist, probably a typo) - rust-lang#71762 (doc: this resulted in a link pointing to a non-existent target) Failed merges: - rust-lang#71726 (Suggest deref when coercing `ty::Ref` to `ty::RawPtr` with arbitrary mutability) r? @ghost
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fixes #68615
r? @eddyb