bjoernager/rust
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Show more information when multiple impl apply

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This commit is contained in:
Esteban Küber 2023-08-14 11:56:23 +00:00
parent 79f38b7914
commit 2817ece19c
7 changed files with 158 additions and 8 deletions
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23
compiler/rustc_trait_selection/src/traits/error_reporting/mod.rs
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@ -17,6 +17,7 @@ use crate::solve::{GenerateProofTree, InferCtxtEvalExt, UseGlobalCache};
use crate::traits::query::evaluate_obligation::InferCtxtExt as _;
use crate::traits::specialize::to_pretty_impl_header;
use crate::traits::NormalizeExt;
use ambiguity::Ambiguity::*;
use on_unimplemented::{AppendConstMessage, OnUnimplementedNote, TypeErrCtxtExt as _};
use rustc_data_structures::fx::{FxHashMap, FxIndexMap};
use rustc_errors::{
@ -2366,14 +2367,28 @@ impl<'tcx> InferCtxtPrivExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
)
};
let ambiguities = ambiguity::recompute_applicable_impls(
let mut ambiguities = ambiguity::recompute_applicable_impls(
self.infcx,
&obligation.with(self.tcx, trait_ref),
);
let has_non_region_infer =
trait_ref.skip_binder().args.types().any(|t| !t.is_ty_or_numeric_infer());
// It doesn't make sense to talk about applicable impls if there are more
// than a handful of them.
// It doesn't make sense to talk about applicable impls if there are more than a
// handful of them. If there are a lot of them, but only a few of them have no type
// params, we only show those, as they are more likely to be useful/intended.
if ambiguities.len() > 20 {
let infcx = self.infcx;
if !ambiguities.iter().all(|option| match option {
DefId(did) => infcx.fresh_args_for_item(DUMMY_SP, *did).is_empty(),
ParamEnv(_) => true,
}) {
// If not all are blanket impls, we filter blanked impls out.
ambiguities.retain(|option| match option {
DefId(did) => infcx.fresh_args_for_item(DUMMY_SP, *did).is_empty(),
ParamEnv(_) => true,
});
}
}
if ambiguities.len() > 1 && ambiguities.len() < 10 && has_non_region_infer {
if self.tainted_by_errors().is_some() && subst.is_none() {
// If `subst.is_none()`, then this is probably two param-env
@ -2392,7 +2407,7 @@ impl<'tcx> InferCtxtPrivExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
err.note(format!("cannot satisfy `{predicate}`"));
let impl_candidates = self
.find_similar_impl_candidates(predicate.to_opt_poly_trait_pred().unwrap());
if impl_candidates.len() < 10 {
if impl_candidates.len() < 40 {
self.report_similar_impl_candidates(
impl_candidates.as_slice(),
trait_ref,