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409 lines
17 KiB
Rust
409 lines
17 KiB
Rust
use crate::astconv::AstConv;
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use crate::errors::{ManualImplementation, MissingTypeParams};
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use rustc_data_structures::fx::FxHashMap;
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use rustc_errors::{pluralize, struct_span_err, Applicability, ErrorGuaranteed};
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use rustc_hir as hir;
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use rustc_hir::def_id::DefId;
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use rustc_middle::ty;
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use rustc_session::parse::feature_err;
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use rustc_span::lev_distance::find_best_match_for_name;
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use rustc_span::symbol::{sym, Ident};
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use rustc_span::{Span, Symbol, DUMMY_SP};
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use std::collections::BTreeSet;
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impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
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/// On missing type parameters, emit an E0393 error and provide a structured suggestion using
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/// the type parameter's name as a placeholder.
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pub(crate) fn complain_about_missing_type_params(
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&self,
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missing_type_params: Vec<Symbol>,
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def_id: DefId,
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span: Span,
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empty_generic_args: bool,
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) {
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if missing_type_params.is_empty() {
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return;
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}
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self.tcx().sess.emit_err(MissingTypeParams {
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span,
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def_span: self.tcx().def_span(def_id),
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span_snippet: self.tcx().sess.source_map().span_to_snippet(span).ok(),
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missing_type_params,
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empty_generic_args,
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});
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}
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/// When the code is using the `Fn` traits directly, instead of the `Fn(A) -> B` syntax, emit
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/// an error and attempt to build a reasonable structured suggestion.
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pub(crate) fn complain_about_internal_fn_trait(
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&self,
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span: Span,
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trait_def_id: DefId,
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trait_segment: &'_ hir::PathSegment<'_>,
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is_impl: bool,
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) {
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if self.tcx().features().unboxed_closures {
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return;
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}
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let trait_def = self.tcx().trait_def(trait_def_id);
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if !trait_def.paren_sugar {
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if trait_segment.args().parenthesized {
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// For now, require that parenthetical notation be used only with `Fn()` etc.
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let mut err = feature_err(
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&self.tcx().sess.parse_sess,
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sym::unboxed_closures,
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span,
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"parenthetical notation is only stable when used with `Fn`-family traits",
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);
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err.emit();
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}
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return;
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}
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let sess = self.tcx().sess;
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if !trait_segment.args().parenthesized {
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// For now, require that parenthetical notation be used only with `Fn()` etc.
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let mut err = feature_err(
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&sess.parse_sess,
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sym::unboxed_closures,
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span,
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"the precise format of `Fn`-family traits' type parameters is subject to change",
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);
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// Do not suggest the other syntax if we are in trait impl:
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// the desugaring would contain an associated type constraint.
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if !is_impl {
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let args = trait_segment
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.args
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.as_ref()
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.and_then(|args| args.args.get(0))
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.and_then(|arg| match arg {
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hir::GenericArg::Type(ty) => match ty.kind {
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hir::TyKind::Tup(t) => t
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.iter()
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.map(|e| sess.source_map().span_to_snippet(e.span))
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.collect::<Result<Vec<_>, _>>()
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.map(|a| a.join(", ")),
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_ => sess.source_map().span_to_snippet(ty.span),
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}
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.map(|s| format!("({})", s))
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.ok(),
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_ => None,
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})
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.unwrap_or_else(|| "()".to_string());
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let ret = trait_segment
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.args()
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.bindings
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.iter()
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.find_map(|b| match (b.ident.name == sym::Output, &b.kind) {
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(true, hir::TypeBindingKind::Equality { term }) => {
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let span = match term {
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hir::Term::Ty(ty) => ty.span,
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hir::Term::Const(c) => self.tcx().hir().span(c.hir_id),
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};
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sess.source_map().span_to_snippet(span).ok()
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}
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_ => None,
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})
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.unwrap_or_else(|| "()".to_string());
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err.span_suggestion(
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span,
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"use parenthetical notation instead",
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format!("{}{} -> {}", trait_segment.ident, args, ret),
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Applicability::MaybeIncorrect,
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);
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}
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err.emit();
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}
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if is_impl {
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let trait_name = self.tcx().def_path_str(trait_def_id);
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self.tcx().sess.emit_err(ManualImplementation { span, trait_name });
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}
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}
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pub(crate) fn complain_about_assoc_type_not_found<I>(
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&self,
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all_candidates: impl Fn() -> I,
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ty_param_name: &str,
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assoc_name: Ident,
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span: Span,
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) -> ErrorGuaranteed
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where
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I: Iterator<Item = ty::PolyTraitRef<'tcx>>,
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{
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// The fallback span is needed because `assoc_name` might be an `Fn()`'s `Output` without a
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// valid span, so we point at the whole path segment instead.
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let span = if assoc_name.span != DUMMY_SP { assoc_name.span } else { span };
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let mut err = struct_span_err!(
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self.tcx().sess,
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span,
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E0220,
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"associated type `{}` not found for `{}`",
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assoc_name,
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ty_param_name
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);
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let all_candidate_names: Vec<_> = all_candidates()
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.flat_map(|r| self.tcx().associated_items(r.def_id()).in_definition_order())
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.filter_map(
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|item| if item.kind == ty::AssocKind::Type { Some(item.name) } else { None },
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)
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.collect();
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if let (Some(suggested_name), true) = (
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find_best_match_for_name(&all_candidate_names, assoc_name.name, None),
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assoc_name.span != DUMMY_SP,
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) {
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err.span_suggestion(
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assoc_name.span,
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"there is an associated type with a similar name",
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suggested_name,
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Applicability::MaybeIncorrect,
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);
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return err.emit();
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}
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// If we didn't find a good item in the supertraits (or couldn't get
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// the supertraits), like in ItemCtxt, then look more generally from
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// all visible traits. If there's one clear winner, just suggest that.
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let visible_traits: Vec<_> = self
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.tcx()
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.all_traits()
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.filter(|trait_def_id| {
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let viz = self.tcx().visibility(*trait_def_id);
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let def_id = self.item_def_id();
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viz.is_accessible_from(def_id, self.tcx())
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})
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.collect();
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let wider_candidate_names: Vec<_> = visible_traits
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.iter()
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.flat_map(|trait_def_id| {
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self.tcx().associated_items(*trait_def_id).in_definition_order()
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})
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.filter_map(
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|item| if item.kind == ty::AssocKind::Type { Some(item.name) } else { None },
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)
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.collect();
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if let (Some(suggested_name), true) = (
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find_best_match_for_name(&wider_candidate_names, assoc_name.name, None),
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assoc_name.span != DUMMY_SP,
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) {
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if let [best_trait] = visible_traits
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.iter()
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.filter(|trait_def_id| {
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self.tcx()
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.associated_items(*trait_def_id)
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.filter_by_name_unhygienic(suggested_name)
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.any(|item| item.kind == ty::AssocKind::Type)
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})
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.collect::<Vec<_>>()[..]
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{
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err.span_label(
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assoc_name.span,
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format!(
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"there is a similarly named associated type `{suggested_name}` in the trait `{}`",
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self.tcx().def_path_str(*best_trait)
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),
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);
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return err.emit();
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}
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}
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err.span_label(span, format!("associated type `{}` not found", assoc_name));
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err.emit()
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}
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/// When there are any missing associated types, emit an E0191 error and attempt to supply a
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/// reasonable suggestion on how to write it. For the case of multiple associated types in the
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/// same trait bound have the same name (as they come from different supertraits), we instead
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/// emit a generic note suggesting using a `where` clause to constraint instead.
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pub(crate) fn complain_about_missing_associated_types(
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&self,
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associated_types: FxHashMap<Span, BTreeSet<DefId>>,
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potential_assoc_types: Vec<Span>,
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trait_bounds: &[hir::PolyTraitRef<'_>],
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) {
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if associated_types.values().all(|v| v.is_empty()) {
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return;
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}
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let tcx = self.tcx();
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// FIXME: Marked `mut` so that we can replace the spans further below with a more
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// appropriate one, but this should be handled earlier in the span assignment.
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let mut associated_types: FxHashMap<Span, Vec<_>> = associated_types
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.into_iter()
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.map(|(span, def_ids)| {
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(span, def_ids.into_iter().map(|did| tcx.associated_item(did)).collect())
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})
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.collect();
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let mut names = vec![];
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// Account for things like `dyn Foo + 'a`, like in tests `issue-22434.rs` and
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// `issue-22560.rs`.
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let mut trait_bound_spans: Vec<Span> = vec![];
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for (span, items) in &associated_types {
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if !items.is_empty() {
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trait_bound_spans.push(*span);
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}
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for assoc_item in items {
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let trait_def_id = assoc_item.container_id(tcx);
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names.push(format!(
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"`{}` (from trait `{}`)",
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assoc_item.name,
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tcx.def_path_str(trait_def_id),
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));
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}
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}
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if let ([], [bound]) = (&potential_assoc_types[..], &trait_bounds) {
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match bound.trait_ref.path.segments {
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// FIXME: `trait_ref.path.span` can point to a full path with multiple
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// segments, even though `trait_ref.path.segments` is of length `1`. Work
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// around that bug here, even though it should be fixed elsewhere.
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// This would otherwise cause an invalid suggestion. For an example, look at
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// `tests/ui/issues/issue-28344.rs` where instead of the following:
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//
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// error[E0191]: the value of the associated type `Output`
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// (from trait `std::ops::BitXor`) must be specified
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// --> $DIR/issue-28344.rs:4:17
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// |
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// LL | let x: u8 = BitXor::bitor(0 as u8, 0 as u8);
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// | ^^^^^^ help: specify the associated type:
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// | `BitXor<Output = Type>`
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//
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// we would output:
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//
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// error[E0191]: the value of the associated type `Output`
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// (from trait `std::ops::BitXor`) must be specified
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// --> $DIR/issue-28344.rs:4:17
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// |
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// LL | let x: u8 = BitXor::bitor(0 as u8, 0 as u8);
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// | ^^^^^^^^^^^^^ help: specify the associated type:
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// | `BitXor::bitor<Output = Type>`
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[segment] if segment.args.is_none() => {
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trait_bound_spans = vec![segment.ident.span];
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associated_types = associated_types
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.into_iter()
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.map(|(_, items)| (segment.ident.span, items))
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.collect();
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}
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_ => {}
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}
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}
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names.sort();
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trait_bound_spans.sort();
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let mut err = struct_span_err!(
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tcx.sess,
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trait_bound_spans,
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E0191,
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"the value of the associated type{} {} must be specified",
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pluralize!(names.len()),
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names.join(", "),
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);
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let mut suggestions = vec![];
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let mut types_count = 0;
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let mut where_constraints = vec![];
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let mut already_has_generics_args_suggestion = false;
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for (span, assoc_items) in &associated_types {
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let mut names: FxHashMap<_, usize> = FxHashMap::default();
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for item in assoc_items {
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types_count += 1;
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*names.entry(item.name).or_insert(0) += 1;
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}
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let mut dupes = false;
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for item in assoc_items {
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let prefix = if names[&item.name] > 1 {
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let trait_def_id = item.container_id(tcx);
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dupes = true;
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format!("{}::", tcx.def_path_str(trait_def_id))
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} else {
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String::new()
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};
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if let Some(sp) = tcx.hir().span_if_local(item.def_id) {
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err.span_label(sp, format!("`{}{}` defined here", prefix, item.name));
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}
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}
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if potential_assoc_types.len() == assoc_items.len() {
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// When the amount of missing associated types equals the number of
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// extra type arguments present. A suggesting to replace the generic args with
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// associated types is already emitted.
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already_has_generics_args_suggestion = true;
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} else if let (Ok(snippet), false) =
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(tcx.sess.source_map().span_to_snippet(*span), dupes)
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{
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let types: Vec<_> =
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assoc_items.iter().map(|item| format!("{} = Type", item.name)).collect();
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let code = if snippet.ends_with('>') {
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// The user wrote `Trait<'a>` or similar and we don't have a type we can
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// suggest, but at least we can clue them to the correct syntax
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// `Trait<'a, Item = Type>` while accounting for the `<'a>` in the
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// suggestion.
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format!("{}, {}>", &snippet[..snippet.len() - 1], types.join(", "))
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} else {
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// The user wrote `Iterator`, so we don't have a type we can suggest, but at
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// least we can clue them to the correct syntax `Iterator<Item = Type>`.
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format!("{}<{}>", snippet, types.join(", "))
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};
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suggestions.push((*span, code));
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} else if dupes {
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where_constraints.push(*span);
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}
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}
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let where_msg = "consider introducing a new type parameter, adding `where` constraints \
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using the fully-qualified path to the associated types";
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if !where_constraints.is_empty() && suggestions.is_empty() {
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// If there are duplicates associated type names and a single trait bound do not
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// use structured suggestion, it means that there are multiple supertraits with
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// the same associated type name.
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err.help(where_msg);
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}
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if suggestions.len() != 1 || already_has_generics_args_suggestion {
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// We don't need this label if there's an inline suggestion, show otherwise.
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for (span, assoc_items) in &associated_types {
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let mut names: FxHashMap<_, usize> = FxHashMap::default();
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for item in assoc_items {
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types_count += 1;
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*names.entry(item.name).or_insert(0) += 1;
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}
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let mut label = vec![];
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for item in assoc_items {
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let postfix = if names[&item.name] > 1 {
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let trait_def_id = item.container_id(tcx);
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format!(" (from trait `{}`)", tcx.def_path_str(trait_def_id))
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} else {
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String::new()
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};
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label.push(format!("`{}`{}", item.name, postfix));
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}
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if !label.is_empty() {
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err.span_label(
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*span,
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format!(
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"associated type{} {} must be specified",
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pluralize!(label.len()),
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label.join(", "),
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),
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);
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}
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}
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}
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if !suggestions.is_empty() {
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err.multipart_suggestion(
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&format!("specify the associated type{}", pluralize!(types_count)),
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suggestions,
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Applicability::HasPlaceholders,
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);
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if !where_constraints.is_empty() {
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err.span_help(where_constraints, where_msg);
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}
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}
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err.emit();
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}
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}
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