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Auto merge of rust-lang#119989 - lcnr:sub_relations-bye-bye, r=compil…
…er-errors remove `sub_relations` from the `InferCtxt` While doing so, I tried to remove the `delay_span_bug` in `rematch_impl` again, which lead me to discover another `freshen` bug, fixing that one in the second commit. See commit descriptions for the reasoning behind each change. r? `@compiler-errors`
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81 changes: 81 additions & 0 deletions
81
compiler/rustc_infer/src/infer/error_reporting/sub_relations.rs
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,81 @@ | ||
| use rustc_data_structures::fx::FxHashMap; | ||
| use rustc_data_structures::undo_log::NoUndo; | ||
| use rustc_data_structures::unify as ut; | ||
| use rustc_middle::ty; | ||
|
|
||
| use crate::infer::InferCtxt; | ||
|
|
||
| #[derive(Debug, Copy, Clone, PartialEq)] | ||
| struct SubId(u32); | ||
| impl ut::UnifyKey for SubId { | ||
| type Value = (); | ||
| #[inline] | ||
| fn index(&self) -> u32 { | ||
| self.0 | ||
| } | ||
| #[inline] | ||
| fn from_index(i: u32) -> SubId { | ||
| SubId(i) | ||
| } | ||
| fn tag() -> &'static str { | ||
| "SubId" | ||
| } | ||
| } | ||
|
|
||
| /// When reporting ambiguity errors, we sometimes want to | ||
| /// treat all inference vars which are subtypes of each | ||
| /// others as if they are equal. For this case we compute | ||
| /// the transitive closure of our subtype obligations here. | ||
| /// | ||
| /// E.g. when encountering ambiguity errors, we want to suggest | ||
| /// specifying some method argument or to add a type annotation | ||
| /// to a local variable. Because subtyping cannot change the | ||
| /// shape of a type, it's fine if the cause of the ambiguity error | ||
| /// is only related to the suggested variable via subtyping. | ||
| /// | ||
| /// Even for something like `let x = returns_arg(); x.method();` the | ||
| /// type of `x` is only a supertype of the argument of `returns_arg`. We | ||
| /// still want to suggest specifying the type of the argument. | ||
| #[derive(Default)] | ||
| pub struct SubRelations { | ||
| map: FxHashMap<ty::TyVid, SubId>, | ||
| table: ut::UnificationTableStorage<SubId>, | ||
| } | ||
|
|
||
| impl SubRelations { | ||
| fn get_id<'tcx>(&mut self, infcx: &InferCtxt<'tcx>, vid: ty::TyVid) -> SubId { | ||
| let root_vid = infcx.root_var(vid); | ||
| *self.map.entry(root_vid).or_insert_with(|| self.table.with_log(&mut NoUndo).new_key(())) | ||
| } | ||
|
|
||
| pub fn add_constraints<'tcx>( | ||
| &mut self, | ||
| infcx: &InferCtxt<'tcx>, | ||
| obls: impl IntoIterator<Item = ty::Predicate<'tcx>>, | ||
| ) { | ||
| for p in obls { | ||
| let (a, b) = match p.kind().skip_binder() { | ||
| ty::PredicateKind::Subtype(ty::SubtypePredicate { a_is_expected: _, a, b }) => { | ||
| (a, b) | ||
| } | ||
| ty::PredicateKind::Coerce(ty::CoercePredicate { a, b }) => (a, b), | ||
| _ => continue, | ||
| }; | ||
|
|
||
| match (a.kind(), b.kind()) { | ||
| (&ty::Infer(ty::TyVar(a_vid)), &ty::Infer(ty::TyVar(b_vid))) => { | ||
| let a = self.get_id(infcx, a_vid); | ||
| let b = self.get_id(infcx, b_vid); | ||
| self.table.with_log(&mut NoUndo).unify_var_var(a, b).unwrap(); | ||
| } | ||
| _ => continue, | ||
| } | ||
| } | ||
| } | ||
|
|
||
| pub fn unified<'tcx>(&mut self, infcx: &InferCtxt<'tcx>, a: ty::TyVid, b: ty::TyVid) -> bool { | ||
| let a = self.get_id(infcx, a); | ||
| let b = self.get_id(infcx, b); | ||
| self.table.with_log(&mut NoUndo).unioned(a, b) | ||
| } | ||
| } |
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