rewrite fuzzy on_unimplemented matching to avoid ICEs
This commit is contained in:
Ariel Ben-Yehuda
parent
f0f5ef51bf
commit
5458d8b419
@ -26,11 +26,11 @@ use super::{
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use fmt_macros::{Parser, Piece, Position};
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use hir::def_id::DefId;
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use infer::{InferCtxt, TypeOrigin};
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use ty::{self, ToPredicate, ToPolyTraitRef, TraitRef, Ty, TyCtxt, TypeFoldable, TypeVariants};
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use infer::{InferCtxt};
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use ty::{self, ToPredicate, ToPolyTraitRef, Ty, TyCtxt, TypeFoldable};
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use ty::fast_reject;
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use ty::fold::TypeFolder;
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use ty::subst::{self, ParamSpace, Subst};
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use ty::subst::{self, Subst};
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use util::nodemap::{FnvHashMap, FnvHashSet};
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use std::cmp;
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@ -61,128 +61,6 @@ impl<'a, 'gcx, 'tcx> TraitErrorKey<'tcx> {
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}
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}
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// Enum used to differentiate the "big" and "little" weights.
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enum Weight {
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Coarse,
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Precise,
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}
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trait AssociatedWeight {
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fn get_weight(&self) -> (u32, u32);
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}
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impl<'a> AssociatedWeight for TypeVariants<'a> {
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// Left number is for "global"/"big" weight and right number is for better precision.
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fn get_weight(&self) -> (u32, u32) {
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match *self {
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TypeVariants::TyBool => (1, 1),
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TypeVariants::TyChar => (1, 2),
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TypeVariants::TyStr => (1, 3),
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TypeVariants::TyInt(_) => (2, 1),
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TypeVariants::TyUint(_) => (2, 2),
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TypeVariants::TyFloat(_) => (2, 3),
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TypeVariants::TyRawPtr(_) => (2, 4),
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TypeVariants::TyEnum(_, _) => (3, 1),
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TypeVariants::TyStruct(_, _) => (3, 2),
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TypeVariants::TyBox(_) => (3, 3),
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TypeVariants::TyTuple(_) => (3, 4),
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TypeVariants::TyArray(_, _) => (4, 1),
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TypeVariants::TySlice(_) => (4, 2),
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TypeVariants::TyRef(_, _) => (5, 1),
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TypeVariants::TyFnDef(_, _, _) => (5, 2),
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TypeVariants::TyFnPtr(_) => (5, 3),
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TypeVariants::TyTrait(_) => (6, 1),
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TypeVariants::TyClosure(_, _) => (7, 1),
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TypeVariants::TyProjection(_) => (8, 1),
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TypeVariants::TyParam(_) => (8, 2),
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TypeVariants::TyInfer(_) => (8, 3),
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TypeVariants::TyError => (9, 1),
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}
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}
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}
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// The "closer" the types are, the lesser the weight.
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fn get_weight_diff(a: &ty::TypeVariants, b: &TypeVariants, weight: Weight) -> u32 {
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let (w1, w2) = match weight {
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Weight::Coarse => (a.get_weight().0, b.get_weight().0),
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Weight::Precise => (a.get_weight().1, b.get_weight().1),
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};
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if w1 < w2 {
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w2 - w1
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} else {
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w1 - w2
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}
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}
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// Once we have "globally matching" types, we need to run another filter on them.
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//
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// In the function `get_best_matching_type`, we got the types which might fit the
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// most to the type we're looking for. This second filter now intends to get (if
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// possible) the type which fits the most.
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//
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// For example, the trait expects an `usize` and here you have `u32` and `i32`.
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// Obviously, the "correct" one is `u32`.
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fn filter_matching_types<'tcx>(weights: &[(usize, u32)],
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imps: &[(DefId, subst::Substs<'tcx>)],
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trait_types: &[ty::Ty<'tcx>])
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-> usize {
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let matching_weight = weights[0].1;
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let iter = weights.iter().filter(|&&(_, weight)| weight == matching_weight);
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let mut filtered_weights = vec!();
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for &(pos, _) in iter {
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let mut weight = 0;
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for (type_to_compare, original_type) in imps[pos].1
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.types
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.get_slice(ParamSpace::TypeSpace)
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.iter()
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.zip(trait_types.iter()) {
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weight += get_weight_diff(&type_to_compare.sty, &original_type.sty, Weight::Precise);
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}
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filtered_weights.push((pos, weight));
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}
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filtered_weights.sort_by(|a, b| a.1.cmp(&b.1));
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filtered_weights[0].0
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}
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// Here, we run the "big" filter. Little example:
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//
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// We receive a `String`, an `u32` and an `i32`.
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// The trait expected an `usize`.
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// From human point of view, it's easy to determine that `String` doesn't correspond to
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// the expected type at all whereas `u32` and `i32` could.
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//
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// This first filter intends to only keep the types which match the most.
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fn get_best_matching_type<'tcx>(imps: &[(DefId, subst::Substs<'tcx>)],
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trait_types: &[ty::Ty<'tcx>]) -> usize {
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let mut weights = vec!();
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for (pos, imp) in imps.iter().enumerate() {
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let mut weight = 0;
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for (type_to_compare, original_type) in imp.1
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.types
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.get_slice(ParamSpace::TypeSpace)
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.iter()
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.zip(trait_types.iter()) {
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weight += get_weight_diff(&type_to_compare.sty, &original_type.sty, Weight::Coarse);
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}
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weights.push((pos, weight));
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}
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weights.sort_by(|a, b| a.1.cmp(&b.1));
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if weights[0].1 == weights[1].1 {
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filter_matching_types(&weights, &imps, trait_types)
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} else {
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weights[0].0
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}
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}
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impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
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pub fn report_fulfillment_errors(&self, errors: &Vec<FulfillmentError<'tcx>>) {
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for error in errors {
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@ -272,72 +150,46 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
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substs
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}
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fn get_current_failing_impl(&self,
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trait_ref: &TraitRef<'tcx>,
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obligation: &PredicateObligation<'tcx>)
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-> Option<(DefId, subst::Substs<'tcx>)> {
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let simp = fast_reject::simplify_type(self.tcx,
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trait_ref.self_ty(),
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true);
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let trait_def = self.tcx.lookup_trait_def(trait_ref.def_id);
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fn impl_with_self_type_of(&self,
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trait_ref: ty::PolyTraitRef<'tcx>,
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obligation: &PredicateObligation<'tcx>)
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-> Option<DefId>
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{
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let tcx = self.tcx;
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let mut result = None;
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let mut ambiguous = false;
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match simp {
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Some(_) => {
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let mut matching_impls = Vec::new();
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trait_def.for_each_impl(self.tcx, |def_id| {
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let imp = self.tcx.impl_trait_ref(def_id).unwrap();
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let substs = self.impl_substs(def_id, obligation.clone());
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let imp = imp.subst(self.tcx, &substs);
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let trait_self_ty = tcx.erase_late_bound_regions(&trait_ref).self_ty();
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if self.eq_types(true,
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TypeOrigin::Misc(obligation.cause.span),
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trait_ref.self_ty(),
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imp.self_ty()).is_ok() {
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matching_impls.push((def_id, imp.substs.clone()));
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}
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});
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if matching_impls.len() == 0 {
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None
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} else if matching_impls.len() == 1 {
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Some(matching_impls[0].clone())
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} else {
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let end = trait_ref.input_types().len() - 1;
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// we need to determine which type is the good one!
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Some(matching_impls[get_best_matching_type(&matching_impls,
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&trait_ref.input_types()[0..end])]
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.clone())
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self.tcx.lookup_trait_def(trait_ref.def_id())
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.for_each_relevant_impl(self.tcx, trait_self_ty, |def_id| {
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let impl_self_ty = tcx
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.impl_trait_ref(def_id)
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.unwrap()
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.self_ty()
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.subst(tcx, &self.impl_substs(def_id, obligation.clone()));
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if let Ok(..) = self.can_equate(&trait_self_ty, &impl_self_ty) {
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ambiguous = result.is_some();
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result = Some(def_id);
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}
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},
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None => None,
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}
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}
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});
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fn find_attr(&self,
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def_id: DefId,
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attr_name: &str)
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-> Option<ast::Attribute> {
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for item in self.tcx.get_attrs(def_id).iter() {
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if item.check_name(attr_name) {
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return Some(item.clone());
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match result {
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Some(def_id) if !ambiguous && tcx.has_attr(def_id, "rustc_on_unimplemented") => {
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result
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}
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_ => None
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}
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None
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}
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fn on_unimplemented_note(&self,
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trait_ref: ty::PolyTraitRef<'tcx>,
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obligation: &PredicateObligation<'tcx>) -> Option<String> {
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let def_id = self.impl_with_self_type_of(trait_ref, obligation)
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.unwrap_or(trait_ref.def_id());
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let trait_ref = trait_ref.skip_binder();
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let def_id = match self.get_current_failing_impl(trait_ref, obligation) {
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Some((def_id, _)) => {
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if let Some(_) = self.find_attr(def_id, "rustc_on_unimplemented") {
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def_id
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} else {
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trait_ref.def_id
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}
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},
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None => trait_ref.def_id,
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};
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let span = obligation.cause.span;
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let mut report = None;
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for item in self.tcx.get_attrs(def_id).iter() {
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@ -1,64 +0,0 @@
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// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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// Test if the on_unimplemented message override works
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#![feature(on_unimplemented)]
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#![feature(rustc_attrs)]
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#[rustc_on_unimplemented = "invalid"]
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trait Index<Idx: ?Sized> {
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type Output: ?Sized;
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fn index(&self, index: Idx) -> &Self::Output;
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}
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#[rustc_on_unimplemented = "a isize is required to index into a slice"]
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impl Index<isize> for [i32] {
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type Output = i32;
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fn index(&self, index: isize) -> &i32 {
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&self[index as usize]
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}
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}
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#[rustc_on_unimplemented = "a usize is required to index into a slice"]
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impl Index<usize> for [i32] {
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type Output = i32;
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fn index(&self, index: usize) -> &i32 {
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&self[index]
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}
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}
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trait Foo<A, B> {
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fn f(&self, a: &A, b: &B);
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}
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#[rustc_on_unimplemented = "two i32 Foo trait takes"]
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impl Foo<i32, i32> for [i32] {
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fn f(&self, a: &i32, b: &i32) {}
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}
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#[rustc_on_unimplemented = "two u32 Foo trait takes"]
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impl Foo<u32, u32> for [i32] {
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fn f(&self, a: &u32, b: &u32) {}
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}
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#[rustc_error]
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fn main() {
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Index::<u32>::index(&[1, 2, 3] as &[i32], 2u32); //~ ERROR E0277
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//~| NOTE a usize is required
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//~| NOTE required by
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Index::<i32>::index(&[1, 2, 3] as &[i32], 2i32); //~ ERROR E0277
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//~| NOTE a isize is required
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//~| NOTE required by
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Foo::<usize, usize>::f(&[1, 2, 3] as &[i32], &2usize, &2usize); //~ ERROR E0277
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//~| NOTE two u32 Foo trait
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//~| NOTE required by
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}
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