Add CustomEq
qualif
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0850c3bbb8
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3 changed files with 64 additions and 1 deletions
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@ -80,6 +80,7 @@ pub struct BorrowCheckResult<'tcx> {
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pub struct ConstQualifs {
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pub has_mut_interior: bool,
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pub needs_drop: bool,
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pub custom_eq: bool,
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}
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/// After we borrow check a closure, we are left with various
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@ -2,9 +2,11 @@
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//!
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//! See the `Qualif` trait for more info.
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use rustc_infer::infer::TyCtxtInferExt;
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use rustc_middle::mir::*;
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use rustc_middle::ty::{self, subst::SubstsRef, AdtDef, Ty};
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use rustc_span::DUMMY_SP;
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use rustc_trait_selection::traits;
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use super::ConstCx;
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@ -12,6 +14,7 @@ pub fn in_any_value_of_ty(cx: &ConstCx<'_, 'tcx>, ty: Ty<'tcx>) -> ConstQualifs
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ConstQualifs {
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has_mut_interior: HasMutInterior::in_any_value_of_ty(cx, ty),
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needs_drop: NeedsDrop::in_any_value_of_ty(cx, ty),
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custom_eq: CustomEq::in_any_value_of_ty(cx, ty),
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}
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}
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@ -108,6 +111,39 @@ impl Qualif for NeedsDrop {
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}
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}
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/// A constant that cannot be used as part of a pattern in a `match` expression.
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pub struct CustomEq;
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impl Qualif for CustomEq {
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const ANALYSIS_NAME: &'static str = "flow_custom_eq";
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fn in_qualifs(qualifs: &ConstQualifs) -> bool {
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qualifs.custom_eq
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}
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fn in_any_value_of_ty(cx: &ConstCx<'_, 'tcx>, ty: Ty<'tcx>) -> bool {
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// If *any* component of a composite data type does not implement `Structural{Partial,}Eq`,
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// we know that at least some values of that type are not structural-match. I say "some"
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// because that component may be part of an enum variant (e.g.,
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// `Option::<NonStructuralMatchTy>::Some`), in which case some values of this type may be
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// structural-match (`Option::None`).
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let id = cx.tcx.hir().local_def_id_to_hir_id(cx.def_id.as_local().unwrap());
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traits::search_for_structural_match_violation(id, cx.body.span, cx.tcx, ty).is_some()
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}
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fn in_adt_inherently(
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cx: &ConstCx<'_, 'tcx>,
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adt: &'tcx AdtDef,
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substs: SubstsRef<'tcx>,
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) -> bool {
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let ty = cx.tcx.mk_ty(ty::Adt(adt, substs));
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let id = cx.tcx.hir().local_def_id_to_hir_id(cx.def_id.as_local().unwrap());
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cx.tcx
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.infer_ctxt()
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.enter(|infcx| !traits::type_marked_structural(id, cx.body.span, &infcx, ty))
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}
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}
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// FIXME: Use `mir::visit::Visitor` for the `in_*` functions if/when it supports early return.
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/// Returns `true` if this `Rvalue` contains qualif `Q`.
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@ -17,7 +17,7 @@ use std::borrow::Cow;
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use std::ops::Deref;
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use super::ops::{self, NonConstOp};
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use super::qualifs::{self, HasMutInterior, NeedsDrop};
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use super::qualifs::{self, CustomEq, HasMutInterior, NeedsDrop};
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use super::resolver::FlowSensitiveAnalysis;
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use super::{is_lang_panic_fn, ConstCx, ConstKind, Qualif};
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use crate::const_eval::{is_const_fn, is_unstable_const_fn};
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@ -142,9 +142,35 @@ impl Qualifs<'mir, 'tcx> {
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let return_loc = ccx.body.terminator_loc(return_block);
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let custom_eq = match ccx.const_kind() {
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// We don't care whether a `const fn` returns a value that is not structurally
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// matchable. Functions calls are opaque and always use type-based qualification, so
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// this value should never be used.
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ConstKind::ConstFn => true,
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// If we know that all values of the return type are structurally matchable, there's no
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// need to run dataflow.
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ConstKind::Const | ConstKind::Static | ConstKind::StaticMut
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if !CustomEq::in_any_value_of_ty(ccx, ccx.body.return_ty()) =>
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{
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false
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}
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ConstKind::Const | ConstKind::Static | ConstKind::StaticMut => {
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let mut cursor = FlowSensitiveAnalysis::new(CustomEq, ccx)
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.into_engine(ccx.tcx, &ccx.body, ccx.def_id)
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.iterate_to_fixpoint()
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.into_results_cursor(&ccx.body);
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cursor.seek_after(return_loc);
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cursor.contains(RETURN_PLACE)
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}
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};
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ConstQualifs {
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needs_drop: self.needs_drop(ccx, RETURN_PLACE, return_loc),
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has_mut_interior: self.has_mut_interior(ccx, RETURN_PLACE, return_loc),
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custom_eq,
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}
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}
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}
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