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This commit is contained in:
Felix S. Klock II 2019-10-25 14:47:04 +02:00
parent 98f5b11b6b
commit 86f7d6f21e
1 changed files with 21 additions and 5 deletions
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26
src/librustc/ty/structural_match.rs
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@ -93,17 +93,20 @@ pub fn type_marked_structural(id: hir::HirId,
fulfillment_cx.select_all_or_error(infcx).is_ok()
}
/// This implements the traversal over the structure of a given type to try to
/// find instances of ADTs (specifically structs or enums) that do not implement
/// the structural-match traits (`StructuralPartialEq` and `StructuralEq`).
struct Search<'a, 'tcx> {
id: hir::HirId,
span: Span,
infcx: InferCtxt<'a, 'tcx>,
// records the first ADT we find that does not implement `Structural`.
/// Records first ADT that does not implement a structural-match trait.
found: Option<NonStructuralMatchTy<'tcx>>,
// tracks ADT's previously encountered during search, so that
// we will not recur on them again.
/// Tracks ADTs previously encountered during search, so that
/// we will not recur on them again.
seen: FxHashSet<hir::def_id::DefId>,
}
@ -129,13 +132,26 @@ impl<'a, 'tcx> TypeVisitor<'tcx> for Search<'a, 'tcx> {
}
ty::RawPtr(..) => {
// structural-match ignores substructure of
// `*const _`/`*mut _`, so skip super_visit_with
// `*const _`/`*mut _`, so skip `super_visit_with`.
//
// For example, if you have:
// ```
// struct NonStructural;
// #[derive(PartialEq, Eq)]
// struct T(*const NonStructural);
// const C: T = T(std::ptr::null());
// ```
//
// Even though `NonStructural` does not implement `PartialEq`,
// structural equality on `T` does not recur into the raw
// pointer. Therefore, one can still use `C` in a pattern.
// (But still tell caller to continue search.)
return false;
}
ty::FnDef(..) | ty::FnPtr(..) => {
// types of formals and return in `fn(_) -> _` are also irrelevant
// types of formals and return in `fn(_) -> _` are also irrelevant;
// so we do not recur into them via `super_visit_with`
//
// (But still tell caller to continue search.)
return false;