bjoernager/rust
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always emit AliasRelate goals when relating aliases

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Add `StructurallyRelateAliases` to allow instantiating infer vars with rigid aliases.
Change `instantiate_query_response` to be infallible in the new solver. This requires canonicalization to not hide any information used by the query, so weaken
universe compression. It also modifies `term_is_fully_unconstrained` to allow
region inference variables in a higher universe.
This commit is contained in:
lcnr 2024-02-26 10:17:43 +01:00
parent eeeb9b4d31
commit 1b3164f5c9
21 changed files with 417 additions and 272 deletions
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38
compiler/rustc_next_trait_solver/src/canonicalizer.rs
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@ -108,21 +108,22 @@ impl<'a, Infcx: InferCtxtLike<Interner = I>, I: Interner> Canonicalizer<'a, Infc
// universes `n`, this algorithm compresses them in place so that:
//
// - the new universe indices are as small as possible
// - we only create a new universe if we would otherwise put a placeholder in
// the same compressed universe as an existential which cannot name it
// - we create a new universe if we would otherwise
// 1. put existentials from a different universe into the same one
// 2. put a placeholder in the same universe as an existential which cannot name it
//
// Let's walk through an example:
// - var_infos: [E0, U1, E5, U2, E2, E6, U6], curr_compressed_uv: 0, next_orig_uv: 0
// - var_infos: [E0, U1, E5, U2, E2, E6, U6], curr_compressed_uv: 0, next_orig_uv: 1
// - var_infos: [E0, U1, E5, U2, E2, E6, U6], curr_compressed_uv: 1, next_orig_uv: 2
// - var_infos: [E0, U1, E5, U1, E1, E6, U6], curr_compressed_uv: 1, next_orig_uv: 5
// - var_infos: [E0, U1, E1, U1, E1, E6, U6], curr_compressed_uv: 1, next_orig_uv: 6
// - var_infos: [E0, U1, E1, U1, E1, E2, U2], curr_compressed_uv: 2, next_orig_uv: -
// - var_infos: [E0, U1, E2, U1, E1, E6, U6], curr_compressed_uv: 2, next_orig_uv: 6
// - var_infos: [E0, U1, E1, U1, E1, E3, U3], curr_compressed_uv: 2, next_orig_uv: -
//
// This algorithm runs in `O(n²)` where `n` is the number of different universe
// indices in the input. This should be fine as `n` is expected to be small.
let mut curr_compressed_uv = ty::UniverseIndex::ROOT;
let mut existential_in_new_uv = false;
let mut existential_in_new_uv = None;
let mut next_orig_uv = Some(ty::UniverseIndex::ROOT);
while let Some(orig_uv) = next_orig_uv.take() {
let mut update_uv = |var: &mut CanonicalVarInfo<I>, orig_uv, is_existential| {
@ -131,14 +132,29 @@ impl<'a, Infcx: InferCtxtLike<Interner = I>, I: Interner> Canonicalizer<'a, Infc
Ordering::Less => (), // Already updated
Ordering::Equal => {
if is_existential {
existential_in_new_uv = true;
} else if existential_in_new_uv {
if existential_in_new_uv.is_some_and(|uv| uv < orig_uv) {
// Condition 1.
//
// We already put an existential from a outer universe
// into the current compressed universe, so we need to
// create a new one.
curr_compressed_uv = curr_compressed_uv.next_universe();
}
// `curr_compressed_uv` will now contain an existential from
// `orig_uv`. Trying to canonicalizing an existential from
// a higher universe has to therefore use a new compressed
// universe.
existential_in_new_uv = Some(orig_uv);
} else if existential_in_new_uv.is_some() {
// Condition 2.
//
// `var` is a placeholder from a universe which is not nameable
// by an existential which we already put into the compressed
// universe `curr_compressed_uv`. We therefore have to create a
// new universe for `var`.
curr_compressed_uv = curr_compressed_uv.next_universe();
existential_in_new_uv = false;
existential_in_new_uv = None;
}
*var = var.with_updated_universe(curr_compressed_uv);
@ -174,8 +190,14 @@ impl<'a, Infcx: InferCtxtLike<Interner = I>, I: Interner> Canonicalizer<'a, Infc
}
}
// We uniquify regions and always put them into their own universe
let mut first_region = true;
for var in var_infos.iter_mut() {
if var.is_region() {
if first_region {
first_region = false;
curr_compressed_uv = curr_compressed_uv.next_universe();
}
assert!(var.is_existential());
*var = var.with_updated_universe(curr_compressed_uv);
}