rustc_trait_selection/error_reporting/traits/fulfillment_errors.rs
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use core::ops::ControlFlow;
use std::borrow::Cow;
use rustc_ast::TraitObjectSyntax;
use rustc_data_structures::fx::FxHashMap;
use rustc_data_structures::unord::UnordSet;
use rustc_errors::codes::*;
use rustc_errors::{
Applicability, Diag, ErrorGuaranteed, Level, MultiSpan, StashKey, StringPart, Suggestions,
pluralize, struct_span_code_err,
};
use rustc_hir::def::Namespace;
use rustc_hir::def_id::{DefId, LOCAL_CRATE, LocalDefId};
use rustc_hir::intravisit::Visitor;
use rustc_hir::{self as hir, LangItem, Node};
use rustc_infer::infer::{InferOk, TypeTrace};
use rustc_middle::traits::SignatureMismatchData;
use rustc_middle::traits::select::OverflowError;
use rustc_middle::ty::abstract_const::NotConstEvaluatable;
use rustc_middle::ty::error::{ExpectedFound, TypeError};
use rustc_middle::ty::fold::{TypeFolder, TypeSuperFoldable};
use rustc_middle::ty::print::{
FmtPrinter, Print, PrintPolyTraitPredicateExt, PrintTraitPredicateExt as _,
PrintTraitRefExt as _, with_forced_trimmed_paths,
};
use rustc_middle::ty::{
self, ToPolyTraitRef, TraitRef, Ty, TyCtxt, TypeFoldable, TypeVisitableExt, Upcast,
};
use rustc_middle::{bug, span_bug};
use rustc_span::symbol::sym;
use rustc_span::{BytePos, DUMMY_SP, Span, Symbol};
use tracing::{debug, instrument};
use super::on_unimplemented::{AppendConstMessage, OnUnimplementedNote};
use super::suggestions::get_explanation_based_on_obligation;
use super::{
ArgKind, CandidateSimilarity, FindExprBySpan, GetSafeTransmuteErrorAndReason, ImplCandidate,
UnsatisfiedConst,
};
use crate::error_reporting::TypeErrCtxt;
use crate::error_reporting::infer::TyCategory;
use crate::error_reporting::traits::report_dyn_incompatibility;
use crate::errors::{
AsyncClosureNotFn, ClosureFnMutLabel, ClosureFnOnceLabel, ClosureKindMismatch,
};
use crate::infer::{self, InferCtxt, InferCtxtExt as _};
use crate::traits::query::evaluate_obligation::InferCtxtExt as _;
use crate::traits::{
MismatchedProjectionTypes, NormalizeExt, Obligation, ObligationCause, ObligationCauseCode,
ObligationCtxt, Overflow, PredicateObligation, SelectionError, SignatureMismatch,
TraitDynIncompatible, elaborate,
};
impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
/// The `root_obligation` parameter should be the `root_obligation` field
/// from a `FulfillmentError`. If no `FulfillmentError` is available,
/// then it should be the same as `obligation`.
pub fn report_selection_error(
&self,
mut obligation: PredicateObligation<'tcx>,
root_obligation: &PredicateObligation<'tcx>,
error: &SelectionError<'tcx>,
) -> ErrorGuaranteed {
let tcx = self.tcx;
let mut span = obligation.cause.span;
let mut err = match *error {
SelectionError::Unimplemented => {
// If this obligation was generated as a result of well-formedness checking, see if we
// can get a better error message by performing HIR-based well-formedness checking.
if let ObligationCauseCode::WellFormed(Some(wf_loc)) =
root_obligation.cause.code().peel_derives()
&& !obligation.predicate.has_non_region_infer()
{
if let Some(cause) = self
.tcx
.diagnostic_hir_wf_check((tcx.erase_regions(obligation.predicate), *wf_loc))
{
obligation.cause = cause.clone();
span = obligation.cause.span;
}
}
if let ObligationCauseCode::CompareImplItem {
impl_item_def_id,
trait_item_def_id,
kind: _,
} = *obligation.cause.code()
{
debug!("ObligationCauseCode::CompareImplItemObligation");
return self.report_extra_impl_obligation(
span,
impl_item_def_id,
trait_item_def_id,
&format!("`{}`", obligation.predicate),
)
.emit()
}
// Report a const-param specific error
if let ObligationCauseCode::ConstParam(ty) = *obligation.cause.code().peel_derives()
{
return self.report_const_param_not_wf(ty, &obligation).emit();
}
let bound_predicate = obligation.predicate.kind();
match bound_predicate.skip_binder() {
ty::PredicateKind::Clause(ty::ClauseKind::Trait(trait_predicate)) => {
let leaf_trait_predicate =
self.resolve_vars_if_possible(bound_predicate.rebind(trait_predicate));
// Let's use the root obligation as the main message, when we care about the
// most general case ("X doesn't implement Pattern<'_>") over the case that
// happened to fail ("char doesn't implement Fn(&mut char)").
//
// We rely on a few heuristics to identify cases where this root
// obligation is more important than the leaf obligation:
let (main_trait_predicate, o) = if let ty::PredicateKind::Clause(
ty::ClauseKind::Trait(root_pred)
) = root_obligation.predicate.kind().skip_binder()
&& !leaf_trait_predicate.self_ty().skip_binder().has_escaping_bound_vars()
&& !root_pred.self_ty().has_escaping_bound_vars()
// The type of the leaf predicate is (roughly) the same as the type
// from the root predicate, as a proxy for "we care about the root"
// FIXME: this doesn't account for trivial derefs, but works as a first
// approximation.
&& (
// `T: Trait` && `&&T: OtherTrait`, we want `OtherTrait`
self.can_eq(
obligation.param_env,
leaf_trait_predicate.self_ty().skip_binder(),
root_pred.self_ty().peel_refs(),
)
// `&str: Iterator` && `&str: IntoIterator`, we want `IntoIterator`
|| self.can_eq(
obligation.param_env,
leaf_trait_predicate.self_ty().skip_binder(),
root_pred.self_ty(),
)
)
// The leaf trait and the root trait are different, so as to avoid
// talking about `&mut T: Trait` and instead remain talking about
// `T: Trait` instead
&& leaf_trait_predicate.def_id() != root_pred.def_id()
// The root trait is not `Unsize`, as to avoid talking about it in
// `tests/ui/coercion/coerce-issue-49593-box-never.rs`.
&& Some(root_pred.def_id()) != self.tcx.lang_items().unsize_trait()
{
(
self.resolve_vars_if_possible(
root_obligation.predicate.kind().rebind(root_pred),
),
root_obligation,
)
} else {
(leaf_trait_predicate, &obligation)
};
let main_trait_ref = main_trait_predicate.to_poly_trait_ref();
let leaf_trait_ref = leaf_trait_predicate.to_poly_trait_ref();
if let Some(guar) = self.emit_specialized_closure_kind_error(
&obligation,
leaf_trait_ref,
) {
return guar;
}
if let Err(guar) = leaf_trait_predicate.error_reported()
{
return guar;
}
// Silence redundant errors on binding access that are already
// reported on the binding definition (#56607).
if let Err(guar) = self.fn_arg_obligation(&obligation) {
return guar;
}
let mut file = None;
let (post_message, pre_message, type_def) = self
.get_parent_trait_ref(obligation.cause.code())
.map(|(t, s)| {
let t = self.tcx.short_ty_string(t, &mut file);
(
format!(" in `{t}`"),
format!("within `{t}`, "),
s.map(|s| (format!("within this `{t}`"), s)),
)
})
.unwrap_or_default();
let file_note = file.as_ref().map(|file| format!(
"the full trait has been written to '{}'",
file.display(),
));
let mut long_ty_file = None;
let OnUnimplementedNote {
message,
label,
notes,
parent_label,
append_const_msg,
} = self.on_unimplemented_note(main_trait_predicate, o, &mut long_ty_file);
let have_alt_message = message.is_some() || label.is_some();
let is_try_conversion = self.is_try_conversion(span, main_trait_ref.def_id());
let is_unsize =
self.tcx.is_lang_item(leaf_trait_ref.def_id(), LangItem::Unsize);
let (message, notes, append_const_msg) = if is_try_conversion {
(
Some(format!(
"`?` couldn't convert the error to `{}`",
main_trait_ref.skip_binder().self_ty(),
)),
vec![
"the question mark operation (`?`) implicitly performs a \
conversion on the error value using the `From` trait"
.to_owned(),
],
Some(AppendConstMessage::Default),
)
} else {
(message, notes, append_const_msg)
};
let err_msg = self.get_standard_error_message(
main_trait_predicate,
message,
None,
append_const_msg,
post_message,
);
let (err_msg, safe_transmute_explanation) = if self.tcx.is_lang_item(main_trait_ref.def_id(), LangItem::TransmuteTrait)
{
// Recompute the safe transmute reason and use that for the error reporting
match self.get_safe_transmute_error_and_reason(
obligation.clone(),
main_trait_ref,
span,
) {
GetSafeTransmuteErrorAndReason::Silent => {
return self.dcx().span_delayed_bug(
span, "silent safe transmute error"
);
}
GetSafeTransmuteErrorAndReason::Default => {
(err_msg, None)
}
GetSafeTransmuteErrorAndReason::Error {
err_msg,
safe_transmute_explanation,
} => (err_msg, safe_transmute_explanation),
}
} else {
(err_msg, None)
};
let mut err = struct_span_code_err!(self.dcx(), span, E0277, "{}", err_msg);
if let Some(long_ty_file) = long_ty_file {
err.note(format!(
"the full name for the type has been written to '{}'",
long_ty_file.display(),
));
err.note("consider using `--verbose` to print the full type name to the console");
}
let mut suggested = false;
if is_try_conversion {
suggested = self.try_conversion_context(&obligation, main_trait_ref.skip_binder(), &mut err);
}
if is_try_conversion && let Some(ret_span) = self.return_type_span(&obligation) {
err.span_label(
ret_span,
format!(
"expected `{}` because of this",
main_trait_ref.skip_binder().self_ty()
),
);
}
if tcx.is_lang_item(leaf_trait_ref.def_id(), LangItem::Tuple) {
self.add_tuple_trait_message(
obligation.cause.code().peel_derives(),
&mut err,
);
}
let explanation = get_explanation_based_on_obligation(
self.tcx,
&obligation,
leaf_trait_predicate,
pre_message,
);
self.check_for_binding_assigned_block_without_tail_expression(
&obligation,
&mut err,
leaf_trait_predicate,
);
self.suggest_add_result_as_return_type(
&obligation,
&mut err,
leaf_trait_predicate,
);
if self.suggest_add_reference_to_arg(
&obligation,
&mut err,
leaf_trait_predicate,
have_alt_message,
) {
self.note_obligation_cause(&mut err, &obligation);
return err.emit();
}
file_note.map(|note| err.note(note));
if let Some(s) = label {
// If it has a custom `#[rustc_on_unimplemented]`
// error message, let's display it as the label!
err.span_label(span, s);
if !matches!(leaf_trait_ref.skip_binder().self_ty().kind(), ty::Param(_)) {
// When the self type is a type param We don't need to "the trait
// `std::marker::Sized` is not implemented for `T`" as we will point
// at the type param with a label to suggest constraining it.
err.help(explanation);
}
} else if let Some(custom_explanation) = safe_transmute_explanation {
err.span_label(span, custom_explanation);
} else if explanation.len() > self.tcx.sess.diagnostic_width() {
// Really long types don't look good as span labels, instead move it
// to a `help`.
err.span_label(span, "unsatisfied trait bound");
err.help(explanation);
} else {
err.span_label(span, explanation);
}
if let ObligationCauseCode::Coercion { source, target } =
*obligation.cause.code().peel_derives()
{
if self.tcx.is_lang_item(leaf_trait_ref.def_id(), LangItem::Sized) {
self.suggest_borrowing_for_object_cast(
&mut err,
root_obligation,
source,
target,
);
}
}
let UnsatisfiedConst(unsatisfied_const) = self
.maybe_add_note_for_unsatisfied_const(
leaf_trait_predicate,
&mut err,
span,
);
if let Some((msg, span)) = type_def {
err.span_label(span, msg);
}
for note in notes {
// If it has a custom `#[rustc_on_unimplemented]` note, let's display it
err.note(note);
}
if let Some(s) = parent_label {
let body = obligation.cause.body_id;
err.span_label(tcx.def_span(body), s);
}
self.suggest_floating_point_literal(&obligation, &mut err, leaf_trait_ref);
self.suggest_dereferencing_index(&obligation, &mut err, leaf_trait_predicate);
suggested |= self.suggest_dereferences(&obligation, &mut err, leaf_trait_predicate);
suggested |= self.suggest_fn_call(&obligation, &mut err, leaf_trait_predicate);
let impl_candidates = self.find_similar_impl_candidates(leaf_trait_predicate);
suggested = if let &[cand] = &impl_candidates[..] {
let cand = cand.trait_ref;
if let (ty::FnPtr(..), ty::FnDef(..)) =
(cand.self_ty().kind(), main_trait_ref.self_ty().skip_binder().kind())
{
// Wrap method receivers and `&`-references in parens
let suggestion = if self.tcx.sess.source_map().span_look_ahead(span, ".", Some(50)).is_some() {
vec![
(span.shrink_to_lo(), format!("(")),
(span.shrink_to_hi(), format!(" as {})", cand.self_ty())),
]
} else if let Some(body) = self.tcx.hir().maybe_body_owned_by(obligation.cause.body_id) {
let mut expr_finder = FindExprBySpan::new(span, self.tcx);
expr_finder.visit_expr(body.value);
if let Some(expr) = expr_finder.result &&
let hir::ExprKind::AddrOf(_, _, expr) = expr.kind {
vec![
(expr.span.shrink_to_lo(), format!("(")),
(expr.span.shrink_to_hi(), format!(" as {})", cand.self_ty())),
]
} else {
vec![(span.shrink_to_hi(), format!(" as {}", cand.self_ty()))]
}
} else {
vec![(span.shrink_to_hi(), format!(" as {}", cand.self_ty()))]
};
err.multipart_suggestion(
format!(
"the trait `{}` is implemented for fn pointer `{}`, try casting using `as`",
cand.print_trait_sugared(),
cand.self_ty(),
),
suggestion,
Applicability::MaybeIncorrect,
);
true
} else {
false
}
} else {
false
} || suggested;
suggested |=
self.suggest_remove_reference(&obligation, &mut err, leaf_trait_predicate);
suggested |= self.suggest_semicolon_removal(
&obligation,
&mut err,
span,
leaf_trait_predicate,
);
self.note_version_mismatch(&mut err, leaf_trait_ref);
self.suggest_remove_await(&obligation, &mut err);
self.suggest_derive(&obligation, &mut err, leaf_trait_predicate);
if tcx.is_lang_item(leaf_trait_ref.def_id(), LangItem::Try) {
self.suggest_await_before_try(
&mut err,
&obligation,
leaf_trait_predicate,
span,
);
}
if self.suggest_add_clone_to_arg(&obligation, &mut err, leaf_trait_predicate) {
return err.emit();
}
if self.suggest_impl_trait(&mut err, &obligation, leaf_trait_predicate) {
return err.emit();
}
if is_unsize {
// If the obligation failed due to a missing implementation of the
// `Unsize` trait, give a pointer to why that might be the case
err.note(
"all implementations of `Unsize` are provided \
automatically by the compiler, see \
<https://doc.rust-lang.org/stable/std/marker/trait.Unsize.html> \
for more information",
);
}
let is_fn_trait = tcx.is_fn_trait(leaf_trait_ref.def_id());
let is_target_feature_fn = if let ty::FnDef(def_id, _) =
*leaf_trait_ref.skip_binder().self_ty().kind()
{
!self.tcx.codegen_fn_attrs(def_id).target_features.is_empty()
} else {
false
};
if is_fn_trait && is_target_feature_fn {
err.note(
"`#[target_feature]` functions do not implement the `Fn` traits",
);
}
self.try_to_add_help_message(
&root_obligation,
&obligation,
leaf_trait_predicate,
&mut err,
span,
is_fn_trait,
suggested,
unsatisfied_const,
);
// Changing mutability doesn't make a difference to whether we have
// an `Unsize` impl (Fixes ICE in #71036)
if !is_unsize {
self.suggest_change_mut(&obligation, &mut err, leaf_trait_predicate);
}
// If this error is due to `!: Trait` not implemented but `(): Trait` is
// implemented, and fallback has occurred, then it could be due to a
// variable that used to fallback to `()` now falling back to `!`. Issue a
// note informing about the change in behaviour.
if leaf_trait_predicate.skip_binder().self_ty().is_never()
&& self.fallback_has_occurred
{
let predicate = leaf_trait_predicate.map_bound(|trait_pred| {
trait_pred.with_self_ty(self.tcx, tcx.types.unit)
});
let unit_obligation = obligation.with(tcx, predicate);
if self.predicate_may_hold(&unit_obligation) {
err.note(
"this error might have been caused by changes to \
Rust's type-inference algorithm (see issue #48950 \
<https://github.com/rust-lang/rust/issues/48950> \
for more information)",
);
err.help("did you intend to use the type `()` here instead?");
}
}
self.explain_hrtb_projection(&mut err, leaf_trait_predicate, obligation.param_env, &obligation.cause);
self.suggest_desugaring_async_fn_in_trait(&mut err, main_trait_ref);
// Return early if the trait is Debug or Display and the invocation
// originates within a standard library macro, because the output
// is otherwise overwhelming and unhelpful (see #85844 for an
// example).
let in_std_macro =
match obligation.cause.span.ctxt().outer_expn_data().macro_def_id {
Some(macro_def_id) => {
let crate_name = tcx.crate_name(macro_def_id.krate);
crate_name == sym::std || crate_name == sym::core
}
None => false,
};
if in_std_macro
&& matches!(
self.tcx.get_diagnostic_name(leaf_trait_ref.def_id()),
Some(sym::Debug | sym::Display)
)
{
return err.emit();
}
err
}
ty::PredicateKind::Clause(ty::ClauseKind::HostEffect(predicate)) => {
// FIXME(const_trait_impl): We should recompute the predicate with `~const`
// if it's `const`, and if it holds, explain that this bound only
// *conditionally* holds. If that fails, we should also do selection
// to drill this down to an impl or built-in source, so we can
// point at it and explain that while the trait *is* implemented,
// that implementation is not const.
let err_msg = self.get_standard_error_message(
bound_predicate.rebind(ty::TraitPredicate {
trait_ref: predicate.trait_ref,
polarity: ty::PredicatePolarity::Positive,
}),
None,
Some(predicate.constness),
None,
String::new(),
);
struct_span_code_err!(self.dcx(), span, E0277, "{}", err_msg)
}
ty::PredicateKind::Subtype(predicate) => {
// Errors for Subtype predicates show up as
// `FulfillmentErrorCode::SubtypeError`,
// not selection error.
span_bug!(span, "subtype requirement gave wrong error: `{:?}`", predicate)
}
ty::PredicateKind::Coerce(predicate) => {
// Errors for Coerce predicates show up as
// `FulfillmentErrorCode::SubtypeError`,
// not selection error.
span_bug!(span, "coerce requirement gave wrong error: `{:?}`", predicate)
}
ty::PredicateKind::Clause(ty::ClauseKind::RegionOutlives(..))
| ty::PredicateKind::Clause(ty::ClauseKind::TypeOutlives(..)) => {
span_bug!(
span,
"outlives clauses should not error outside borrowck. obligation: `{:?}`",
obligation
)
}
ty::PredicateKind::Clause(ty::ClauseKind::Projection(..)) => {
span_bug!(
span,
"projection clauses should be implied from elsewhere. obligation: `{:?}`",
obligation
)
}
ty::PredicateKind::DynCompatible(trait_def_id) => {
let violations = self.tcx.dyn_compatibility_violations(trait_def_id);
let mut err = report_dyn_incompatibility(
self.tcx,
span,
None,
trait_def_id,
violations,
);
if let hir::Node::Item(item) =
self.tcx.hir_node_by_def_id(obligation.cause.body_id)
&& let hir::ItemKind::Impl(impl_) = item.kind
&& let None = impl_.of_trait
&& let hir::TyKind::TraitObject(_, _, syntax) = impl_.self_ty.kind
&& let TraitObjectSyntax::None = syntax
&& impl_.self_ty.span.edition().at_least_rust_2021()
{
// Silence the dyn-compatibility error in favor of the missing dyn on
// self type error. #131051.
err.downgrade_to_delayed_bug();
}
err
}
ty::PredicateKind::Clause(ty::ClauseKind::WellFormed(ty)) => {
let ty = self.resolve_vars_if_possible(ty);
if self.next_trait_solver() {
// FIXME: we'll need a better message which takes into account
// which bounds actually failed to hold.
self.dcx().struct_span_err(
span,
format!("the type `{ty}` is not well-formed"),
)
} else {
// WF predicates cannot themselves make
// errors. They can only block due to
// ambiguity; otherwise, they always
// degenerate into other obligations
// (which may fail).
span_bug!(span, "WF predicate not satisfied for {:?}", ty);
}
}
// Errors for `ConstEvaluatable` predicates show up as
// `SelectionError::ConstEvalFailure`,
// not `Unimplemented`.
ty::PredicateKind::Clause(ty::ClauseKind::ConstEvaluatable(..))
// Errors for `ConstEquate` predicates show up as
// `SelectionError::ConstEvalFailure`,
// not `Unimplemented`.
| ty::PredicateKind::ConstEquate { .. }
// Ambiguous predicates should never error
| ty::PredicateKind::Ambiguous
| ty::PredicateKind::NormalizesTo { .. }
| ty::PredicateKind::AliasRelate { .. }
| ty::PredicateKind::Clause(ty::ClauseKind::ConstArgHasType { .. }) => {
span_bug!(
span,
"Unexpected `Predicate` for `SelectionError`: `{:?}`",
obligation
)
}
}
}
SignatureMismatch(box SignatureMismatchData {
found_trait_ref,
expected_trait_ref,
terr: terr @ TypeError::CyclicTy(_),
}) => self.report_cyclic_signature_error(
&obligation,
found_trait_ref,
expected_trait_ref,
terr,
),
SignatureMismatch(box SignatureMismatchData {
found_trait_ref,
expected_trait_ref,
terr: _,
}) => {
match self.report_signature_mismatch_error(
&obligation,
span,
found_trait_ref,
expected_trait_ref,
) {
Ok(err) => err,
Err(guar) => return guar,
}
}
SelectionError::OpaqueTypeAutoTraitLeakageUnknown(def_id) => return self.report_opaque_type_auto_trait_leakage(
&obligation,
def_id,
),
TraitDynIncompatible(did) => {
let violations = self.tcx.dyn_compatibility_violations(did);
report_dyn_incompatibility(self.tcx, span, None, did, violations)
}
SelectionError::NotConstEvaluatable(NotConstEvaluatable::MentionsInfer) => {
bug!(
"MentionsInfer should have been handled in `traits/fulfill.rs` or `traits/select/mod.rs`"
)
}
SelectionError::NotConstEvaluatable(NotConstEvaluatable::MentionsParam) => {
match self.report_not_const_evaluatable_error(&obligation, span) {
Ok(err) => err,
Err(guar) => return guar,
}
}
// Already reported in the query.
SelectionError::NotConstEvaluatable(NotConstEvaluatable::Error(guar)) |
// Already reported.
Overflow(OverflowError::Error(guar)) => {
self.set_tainted_by_errors(guar);
return guar
},
Overflow(_) => {
bug!("overflow should be handled before the `report_selection_error` path");
}
SelectionError::ConstArgHasWrongType { ct, ct_ty, expected_ty } => {
let mut diag = self.dcx().struct_span_err(
span,
format!("the constant `{ct}` is not of type `{expected_ty}`"),
);
self.note_type_err(
&mut diag,
&obligation.cause,
None,
None,
TypeError::Sorts(ty::error::ExpectedFound::new(true, expected_ty, ct_ty)),
false,
);
diag
}
};
self.note_obligation_cause(&mut err, &obligation);
self.point_at_returns_when_relevant(&mut err, &obligation);
err.emit()
}
}
impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
pub(super) fn apply_do_not_recommend(
&self,
obligation: &mut PredicateObligation<'tcx>,
) -> bool {
let mut base_cause = obligation.cause.code().clone();
let mut applied_do_not_recommend = false;
loop {
if let ObligationCauseCode::ImplDerived(ref c) = base_cause {
if self.tcx.do_not_recommend_impl(c.impl_or_alias_def_id) {
let code = (*c.derived.parent_code).clone();
obligation.cause.map_code(|_| code);
obligation.predicate = c.derived.parent_trait_pred.upcast(self.tcx);
applied_do_not_recommend = true;
}
}
if let Some((parent_cause, _parent_pred)) = base_cause.parent() {
base_cause = parent_cause.clone();
} else {
break;
}
}
applied_do_not_recommend
}
fn emit_specialized_closure_kind_error(
&self,
obligation: &PredicateObligation<'tcx>,
mut trait_ref: ty::PolyTraitRef<'tcx>,
) -> Option<ErrorGuaranteed> {
// If `AsyncFnKindHelper` is not implemented, that means that the closure kind
// doesn't extend the goal kind. This is worth reporting, but we can only do so
// if we actually know which closure this goal comes from, so look at the cause
// to see if we can extract that information.
if self.tcx.is_lang_item(trait_ref.def_id(), LangItem::AsyncFnKindHelper)
&& let Some(found_kind) = trait_ref.skip_binder().args.type_at(0).to_opt_closure_kind()
&& let Some(expected_kind) =
trait_ref.skip_binder().args.type_at(1).to_opt_closure_kind()
&& !found_kind.extends(expected_kind)
{
if let Some((_, Some(parent))) = obligation.cause.code().parent() {
// If we have a derived obligation, then the parent will be a `AsyncFn*` goal.
trait_ref = parent.to_poly_trait_ref();
} else if let &ObligationCauseCode::FunctionArg { arg_hir_id, .. } =
obligation.cause.code()
&& let Some(typeck_results) = &self.typeck_results
&& let ty::Closure(closure_def_id, _) | ty::CoroutineClosure(closure_def_id, _) =
*typeck_results.node_type(arg_hir_id).kind()
{
// Otherwise, extract the closure kind from the obligation.
let mut err = self.report_closure_error(
&obligation,
closure_def_id,
found_kind,
expected_kind,
"async ",
);
self.note_obligation_cause(&mut err, &obligation);
self.point_at_returns_when_relevant(&mut err, &obligation);
return Some(err.emit());
}
}
let self_ty = trait_ref.self_ty().skip_binder();
if let Some(expected_kind) = self.tcx.fn_trait_kind_from_def_id(trait_ref.def_id()) {
let (closure_def_id, found_args, by_ref_captures) = match *self_ty.kind() {
ty::Closure(def_id, args) => {
(def_id, args.as_closure().sig().map_bound(|sig| sig.inputs()[0]), None)
}
ty::CoroutineClosure(def_id, args) => (
def_id,
args.as_coroutine_closure()
.coroutine_closure_sig()
.map_bound(|sig| sig.tupled_inputs_ty),
Some(args.as_coroutine_closure().coroutine_captures_by_ref_ty()),
),
_ => return None,
};
let expected_args = trait_ref.map_bound(|trait_ref| trait_ref.args.type_at(1));
// Verify that the arguments are compatible. If the signature is
// mismatched, then we have a totally different error to report.
if self.enter_forall(found_args, |found_args| {
self.enter_forall(expected_args, |expected_args| {
!self.can_eq(obligation.param_env, expected_args, found_args)
})
}) {
return None;
}
if let Some(found_kind) = self.closure_kind(self_ty)
&& !found_kind.extends(expected_kind)
{
let mut err = self.report_closure_error(
&obligation,
closure_def_id,
found_kind,
expected_kind,
"",
);
self.note_obligation_cause(&mut err, &obligation);
self.point_at_returns_when_relevant(&mut err, &obligation);
return Some(err.emit());
}
// If the closure has captures, then perhaps the reason that the trait
// is unimplemented is because async closures don't implement `Fn`/`FnMut`
// if they have captures.
if let Some(by_ref_captures) = by_ref_captures
&& let ty::FnPtr(sig_tys, _) = by_ref_captures.kind()
&& !sig_tys.skip_binder().output().is_unit()
{
let mut err = self.dcx().create_err(AsyncClosureNotFn {
span: self.tcx.def_span(closure_def_id),
kind: expected_kind.as_str(),
});
self.note_obligation_cause(&mut err, &obligation);
self.point_at_returns_when_relevant(&mut err, &obligation);
return Some(err.emit());
}
}
None
}
fn fn_arg_obligation(
&self,
obligation: &PredicateObligation<'tcx>,
) -> Result<(), ErrorGuaranteed> {
if let ObligationCauseCode::FunctionArg { arg_hir_id, .. } = obligation.cause.code()
&& let Node::Expr(arg) = self.tcx.hir_node(*arg_hir_id)
&& let arg = arg.peel_borrows()
&& let hir::ExprKind::Path(hir::QPath::Resolved(
None,
hir::Path { res: hir::def::Res::Local(hir_id), .. },
)) = arg.kind
&& let Node::Pat(pat) = self.tcx.hir_node(*hir_id)
&& let Some((preds, guar)) = self.reported_trait_errors.borrow().get(&pat.span)
&& preds.contains(&obligation.predicate)
{
return Err(*guar);
}
Ok(())
}
/// When the `E` of the resulting `Result<T, E>` in an expression `foo().bar().baz()?`,
/// identify those method chain sub-expressions that could or could not have been annotated
/// with `?`.
fn try_conversion_context(
&self,
obligation: &PredicateObligation<'tcx>,
trait_ref: ty::TraitRef<'tcx>,
err: &mut Diag<'_>,
) -> bool {
let span = obligation.cause.span;
/// Look for the (direct) sub-expr of `?`, and return it if it's a `.` method call.
struct FindMethodSubexprOfTry {
search_span: Span,
}
impl<'v> Visitor<'v> for FindMethodSubexprOfTry {
type Result = ControlFlow<&'v hir::Expr<'v>>;
fn visit_expr(&mut self, ex: &'v hir::Expr<'v>) -> Self::Result {
if let hir::ExprKind::Match(expr, _arms, hir::MatchSource::TryDesugar(_)) = ex.kind
&& ex.span.with_lo(ex.span.hi() - BytePos(1)).source_equal(self.search_span)
&& let hir::ExprKind::Call(_, [expr, ..]) = expr.kind
{
ControlFlow::Break(expr)
} else {
hir::intravisit::walk_expr(self, ex)
}
}
}
let hir_id = self.tcx.local_def_id_to_hir_id(obligation.cause.body_id);
let body_id = match self.tcx.hir_node(hir_id) {
hir::Node::Item(hir::Item { kind: hir::ItemKind::Fn(_, _, body_id), .. }) => body_id,
_ => return false,
};
let ControlFlow::Break(expr) = (FindMethodSubexprOfTry { search_span: span })
.visit_body(self.tcx.hir().body(*body_id))
else {
return false;
};
let Some(typeck) = &self.typeck_results else {
return false;
};
let Some((ObligationCauseCode::QuestionMark, Some(y))) = obligation.cause.code().parent()
else {
return false;
};
if !self.tcx.is_diagnostic_item(sym::FromResidual, y.def_id()) {
return false;
}
let self_ty = trait_ref.self_ty();
let found_ty = trait_ref.args.get(1).and_then(|a| a.as_type());
let mut prev_ty = self.resolve_vars_if_possible(
typeck.expr_ty_adjusted_opt(expr).unwrap_or(Ty::new_misc_error(self.tcx)),
);
// We always look at the `E` type, because that's the only one affected by `?`. If the
// incorrect `Result<T, E>` is because of the `T`, we'll get an E0308 on the whole
// expression, after the `?` has "unwrapped" the `T`.
let get_e_type = |prev_ty: Ty<'tcx>| -> Option<Ty<'tcx>> {
let ty::Adt(def, args) = prev_ty.kind() else {
return None;
};
let Some(arg) = args.get(1) else {
return None;
};
if !self.tcx.is_diagnostic_item(sym::Result, def.did()) {
return None;
}
arg.as_type()
};
let mut suggested = false;
let mut chain = vec![];
// The following logic is similar to `point_at_chain`, but that's focused on associated types
let mut expr = expr;
while let hir::ExprKind::MethodCall(path_segment, rcvr_expr, args, span) = expr.kind {
// Point at every method call in the chain with the `Result` type.
// let foo = bar.iter().map(mapper)?;
// ------ -----------
expr = rcvr_expr;
chain.push((span, prev_ty));
let next_ty = self.resolve_vars_if_possible(
typeck.expr_ty_adjusted_opt(expr).unwrap_or(Ty::new_misc_error(self.tcx)),
);
let is_diagnostic_item = |symbol: Symbol, ty: Ty<'tcx>| {
let ty::Adt(def, _) = ty.kind() else {
return false;
};
self.tcx.is_diagnostic_item(symbol, def.did())
};
// For each method in the chain, see if this is `Result::map_err` or
// `Option::ok_or_else` and if it is, see if the closure passed to it has an incorrect
// trailing `;`.
if let Some(ty) = get_e_type(prev_ty)
&& let Some(found_ty) = found_ty
// Ideally we would instead use `FnCtxt::lookup_method_for_diagnostic` for 100%
// accurate check, but we are in the wrong stage to do that and looking for
// `Result::map_err` by checking the Self type and the path segment is enough.
// sym::ok_or_else
&& (
( // Result::map_err
path_segment.ident.name == sym::map_err
&& is_diagnostic_item(sym::Result, next_ty)
) || ( // Option::ok_or_else
path_segment.ident.name == sym::ok_or_else
&& is_diagnostic_item(sym::Option, next_ty)
)
)
// Found `Result<_, ()>?`
&& let ty::Tuple(tys) = found_ty.kind()
&& tys.is_empty()
// The current method call returns `Result<_, ()>`
&& self.can_eq(obligation.param_env, ty, found_ty)
// There's a single argument in the method call and it is a closure
&& let [arg] = args
&& let hir::ExprKind::Closure(closure) = arg.kind
// The closure has a block for its body with no tail expression
&& let body = self.tcx.hir().body(closure.body)
&& let hir::ExprKind::Block(block, _) = body.value.kind
&& let None = block.expr
// The last statement is of a type that can be converted to the return error type
&& let [.., stmt] = block.stmts
&& let hir::StmtKind::Semi(expr) = stmt.kind
&& let expr_ty = self.resolve_vars_if_possible(
typeck.expr_ty_adjusted_opt(expr)
.unwrap_or(Ty::new_misc_error(self.tcx)),
)
&& self
.infcx
.type_implements_trait(
self.tcx.get_diagnostic_item(sym::From).unwrap(),
[self_ty, expr_ty],
obligation.param_env,
)
.must_apply_modulo_regions()
{
suggested = true;
err.span_suggestion_short(
stmt.span.with_lo(expr.span.hi()),
"remove this semicolon",
String::new(),
Applicability::MachineApplicable,
);
}
prev_ty = next_ty;
if let hir::ExprKind::Path(hir::QPath::Resolved(None, path)) = expr.kind
&& let hir::Path { res: hir::def::Res::Local(hir_id), .. } = path
&& let hir::Node::Pat(binding) = self.tcx.hir_node(*hir_id)
{
let parent = self.tcx.parent_hir_node(binding.hir_id);
// We've reached the root of the method call chain...
if let hir::Node::LetStmt(local) = parent
&& let Some(binding_expr) = local.init
{
// ...and it is a binding. Get the binding creation and continue the chain.
expr = binding_expr;
}
if let hir::Node::Param(_param) = parent {
// ...and it is an fn argument.
break;
}
}
}
// `expr` is now the "root" expression of the method call chain, which can be any
// expression kind, like a method call or a path. If this expression is `Result<T, E>` as
// well, then we also point at it.
prev_ty = self.resolve_vars_if_possible(
typeck.expr_ty_adjusted_opt(expr).unwrap_or(Ty::new_misc_error(self.tcx)),
);
chain.push((expr.span, prev_ty));
let mut prev = None;
for (span, err_ty) in chain.into_iter().rev() {
let err_ty = get_e_type(err_ty);
let err_ty = match (err_ty, prev) {
(Some(err_ty), Some(prev)) if !self.can_eq(obligation.param_env, err_ty, prev) => {
err_ty
}
(Some(err_ty), None) => err_ty,
_ => {
prev = err_ty;
continue;
}
};
if self
.infcx
.type_implements_trait(
self.tcx.get_diagnostic_item(sym::From).unwrap(),
[self_ty, err_ty],
obligation.param_env,
)
.must_apply_modulo_regions()
{
if !suggested {
err.span_label(span, format!("this has type `Result<_, {err_ty}>`"));
}
} else {
err.span_label(
span,
format!(
"this can't be annotated with `?` because it has type `Result<_, {err_ty}>`",
),
);
}
prev = Some(err_ty);
}
suggested
}
fn report_const_param_not_wf(
&self,
ty: Ty<'tcx>,
obligation: &PredicateObligation<'tcx>,
) -> Diag<'a> {
let span = obligation.cause.span;
let mut diag = match ty.kind() {
_ if ty.has_param() => {
span_bug!(span, "const param tys cannot mention other generic parameters");
}
ty::Float(_) => {
struct_span_code_err!(
self.dcx(),
span,
E0741,
"`{ty}` is forbidden as the type of a const generic parameter",
)
}
ty::FnPtr(..) => {
struct_span_code_err!(
self.dcx(),
span,
E0741,
"using function pointers as const generic parameters is forbidden",
)
}
ty::RawPtr(_, _) => {
struct_span_code_err!(
self.dcx(),
span,
E0741,
"using raw pointers as const generic parameters is forbidden",
)
}
ty::Adt(def, _) => {
// We should probably see if we're *allowed* to derive `ConstParamTy` on the type...
let mut diag = struct_span_code_err!(
self.dcx(),
span,
E0741,
"`{ty}` must implement `ConstParamTy` to be used as the type of a const generic parameter",
);
// Only suggest derive if this isn't a derived obligation,
// and the struct is local.
if let Some(span) = self.tcx.hir().span_if_local(def.did())
&& obligation.cause.code().parent().is_none()
{
if ty.is_structural_eq_shallow(self.tcx) {
diag.span_suggestion(
span,
"add `#[derive(ConstParamTy)]` to the struct",
"#[derive(ConstParamTy)]\n",
Applicability::MachineApplicable,
);
} else {
// FIXME(adt_const_params): We should check there's not already an
// overlapping `Eq`/`PartialEq` impl.
diag.span_suggestion(
span,
"add `#[derive(ConstParamTy, PartialEq, Eq)]` to the struct",
"#[derive(ConstParamTy, PartialEq, Eq)]\n",
Applicability::MachineApplicable,
);
}
}
diag
}
_ => {
struct_span_code_err!(
self.dcx(),
span,
E0741,
"`{ty}` can't be used as a const parameter type",
)
}
};
let mut code = obligation.cause.code();
let mut pred = obligation.predicate.as_trait_clause();
while let Some((next_code, next_pred)) = code.parent() {
if let Some(pred) = pred {
self.enter_forall(pred, |pred| {
diag.note(format!(
"`{}` must implement `{}`, but it does not",
pred.self_ty(),
pred.print_modifiers_and_trait_path()
));
})
}
code = next_code;
pred = next_pred;
}
diag
}
}
impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
fn can_match_trait(
&self,
goal: ty::TraitPredicate<'tcx>,
assumption: ty::PolyTraitPredicate<'tcx>,
) -> bool {
if goal.polarity != assumption.polarity() {
return false;
}
let trait_goal = goal.trait_ref;
let trait_assumption = self.instantiate_binder_with_fresh_vars(
DUMMY_SP,
infer::BoundRegionConversionTime::HigherRankedType,
assumption.to_poly_trait_ref(),
);
self.can_eq(ty::ParamEnv::empty(), trait_goal, trait_assumption)
}
fn can_match_projection(
&self,
goal: ty::ProjectionPredicate<'tcx>,
assumption: ty::PolyProjectionPredicate<'tcx>,
) -> bool {
let assumption = self.instantiate_binder_with_fresh_vars(
DUMMY_SP,
infer::BoundRegionConversionTime::HigherRankedType,
assumption,
);
let param_env = ty::ParamEnv::empty();
self.can_eq(param_env, goal.projection_term, assumption.projection_term)
&& self.can_eq(param_env, goal.term, assumption.term)
}
// returns if `cond` not occurring implies that `error` does not occur - i.e., that
// `error` occurring implies that `cond` occurs.
#[instrument(level = "debug", skip(self), ret)]
pub(super) fn error_implies(
&self,
cond: ty::Predicate<'tcx>,
error: ty::Predicate<'tcx>,
) -> bool {
if cond == error {
return true;
}
if let Some(error) = error.as_trait_clause() {
self.enter_forall(error, |error| {
elaborate(self.tcx, std::iter::once(cond))
.filter_map(|implied| implied.as_trait_clause())
.any(|implied| self.can_match_trait(error, implied))
})
} else if let Some(error) = error.as_projection_clause() {
self.enter_forall(error, |error| {
elaborate(self.tcx, std::iter::once(cond))
.filter_map(|implied| implied.as_projection_clause())
.any(|implied| self.can_match_projection(error, implied))
})
} else {
false
}
}
#[instrument(level = "debug", skip_all)]
pub(super) fn report_projection_error(
&self,
obligation: &PredicateObligation<'tcx>,
error: &MismatchedProjectionTypes<'tcx>,
) -> ErrorGuaranteed {
let predicate = self.resolve_vars_if_possible(obligation.predicate);
if let Err(e) = predicate.error_reported() {
return e;
}
self.probe(|_| {
// try to find the mismatched types to report the error with.
//
// this can fail if the problem was higher-ranked, in which
// cause I have no idea for a good error message.
let bound_predicate = predicate.kind();
let (values, err) = match bound_predicate.skip_binder() {
ty::PredicateKind::Clause(ty::ClauseKind::Projection(data)) => {
let ocx = ObligationCtxt::new(self);
let data = self.instantiate_binder_with_fresh_vars(
obligation.cause.span,
infer::BoundRegionConversionTime::HigherRankedType,
bound_predicate.rebind(data),
);
let unnormalized_term = data.projection_term.to_term(self.tcx);
// FIXME(-Znext-solver): For diagnostic purposes, it would be nice
// to deeply normalize this type.
let normalized_term =
ocx.normalize(&obligation.cause, obligation.param_env, unnormalized_term);
// constrain inference variables a bit more to nested obligations from normalize so
// we can have more helpful errors.
//
// we intentionally drop errors from normalization here,
// since the normalization is just done to improve the error message.
let _ = ocx.select_where_possible();
if let Err(new_err) =
ocx.eq(&obligation.cause, obligation.param_env, data.term, normalized_term)
{
(
Some((
data.projection_term,
self.resolve_vars_if_possible(normalized_term),
data.term,
)),
new_err,
)
} else {
(None, error.err)
}
}
ty::PredicateKind::AliasRelate(lhs, rhs, _) => {
let derive_better_type_error =
|alias_term: ty::AliasTerm<'tcx>, expected_term: ty::Term<'tcx>| {
let ocx = ObligationCtxt::new(self);
let normalized_term = match expected_term.unpack() {
ty::TermKind::Ty(_) => self.next_ty_var(DUMMY_SP).into(),
ty::TermKind::Const(_) => self.next_const_var(DUMMY_SP).into(),
};
ocx.register_obligation(Obligation::new(
self.tcx,
ObligationCause::dummy(),
obligation.param_env,
ty::PredicateKind::NormalizesTo(ty::NormalizesTo {
alias: alias_term,
term: normalized_term,
}),
));
let _ = ocx.select_where_possible();
if let Err(terr) = ocx.eq(
&ObligationCause::dummy(),
obligation.param_env,
expected_term,
normalized_term,
) {
Some((terr, self.resolve_vars_if_possible(normalized_term)))
} else {
None
}
};
if let Some(lhs) = lhs.to_alias_term()
&& let Some((better_type_err, expected_term)) =
derive_better_type_error(lhs, rhs)
{
(
Some((lhs, self.resolve_vars_if_possible(expected_term), rhs)),
better_type_err,
)
} else if let Some(rhs) = rhs.to_alias_term()
&& let Some((better_type_err, expected_term)) =
derive_better_type_error(rhs, lhs)
{
(
Some((rhs, self.resolve_vars_if_possible(expected_term), lhs)),
better_type_err,
)
} else {
(None, error.err)
}
}
_ => (None, error.err),
};
let msg = values
.and_then(|(predicate, normalized_term, expected_term)| {
self.maybe_detailed_projection_msg(predicate, normalized_term, expected_term)
})
.unwrap_or_else(|| {
let mut cx = FmtPrinter::new_with_limit(
self.tcx,
Namespace::TypeNS,
rustc_session::Limit(10),
);
with_forced_trimmed_paths!(format!("type mismatch resolving `{}`", {
self.resolve_vars_if_possible(predicate).print(&mut cx).unwrap();
cx.into_buffer()
}))
});
let mut diag = struct_span_code_err!(self.dcx(), obligation.cause.span, E0271, "{msg}");
let secondary_span = (|| {
let ty::PredicateKind::Clause(ty::ClauseKind::Projection(proj)) =
predicate.kind().skip_binder()
else {
return None;
};
let trait_assoc_item = self.tcx.opt_associated_item(proj.projection_term.def_id)?;
let trait_assoc_ident = trait_assoc_item.ident(self.tcx);
let mut associated_items = vec![];
self.tcx.for_each_relevant_impl(
self.tcx.trait_of_item(proj.projection_term.def_id)?,
proj.projection_term.self_ty(),
|impl_def_id| {
associated_items.extend(
self.tcx
.associated_items(impl_def_id)
.in_definition_order()
.find(|assoc| assoc.ident(self.tcx) == trait_assoc_ident),
);
},
);
let [associated_item]: &[ty::AssocItem] = &associated_items[..] else {
return None;
};
match self.tcx.hir().get_if_local(associated_item.def_id) {
Some(
hir::Node::TraitItem(hir::TraitItem {
kind: hir::TraitItemKind::Type(_, Some(ty)),
..
})
| hir::Node::ImplItem(hir::ImplItem {
kind: hir::ImplItemKind::Type(ty),
..
}),
) => Some((
ty.span,
with_forced_trimmed_paths!(Cow::from(format!(
"type mismatch resolving `{}`",
{
let mut cx = FmtPrinter::new_with_limit(
self.tcx,
Namespace::TypeNS,
rustc_session::Limit(5),
);
self.resolve_vars_if_possible(predicate).print(&mut cx).unwrap();
cx.into_buffer()
}
))),
true,
)),
_ => None,
}
})();
self.note_type_err(
&mut diag,
&obligation.cause,
secondary_span,
values.map(|(_, normalized_ty, expected_ty)| {
obligation.param_env.and(infer::ValuePairs::Terms(ExpectedFound::new(
true,
expected_ty,
normalized_ty,
)))
}),
err,
false,
);
self.note_obligation_cause(&mut diag, obligation);
diag.emit()
})
}
fn maybe_detailed_projection_msg(
&self,
projection_term: ty::AliasTerm<'tcx>,
normalized_ty: ty::Term<'tcx>,
expected_ty: ty::Term<'tcx>,
) -> Option<String> {
let trait_def_id = projection_term.trait_def_id(self.tcx);
let self_ty = projection_term.self_ty();
with_forced_trimmed_paths! {
if self.tcx.is_lang_item(projection_term.def_id, LangItem::FnOnceOutput) {
let fn_kind = self_ty.prefix_string(self.tcx);
let item = match self_ty.kind() {
ty::FnDef(def, _) => self.tcx.item_name(*def).to_string(),
_ => self_ty.to_string(),
};
Some(format!(
"expected `{item}` to be a {fn_kind} that returns `{expected_ty}`, but it \
returns `{normalized_ty}`",
))
} else if self.tcx.is_lang_item(trait_def_id, LangItem::Future) {
Some(format!(
"expected `{self_ty}` to be a future that resolves to `{expected_ty}`, but it \
resolves to `{normalized_ty}`"
))
} else if Some(trait_def_id) == self.tcx.get_diagnostic_item(sym::Iterator) {
Some(format!(
"expected `{self_ty}` to be an iterator that yields `{expected_ty}`, but it \
yields `{normalized_ty}`"
))
} else {
None
}
}
}
pub fn fuzzy_match_tys(
&self,
mut a: Ty<'tcx>,
mut b: Ty<'tcx>,
ignoring_lifetimes: bool,
) -> Option<CandidateSimilarity> {
/// returns the fuzzy category of a given type, or None
/// if the type can be equated to any type.
fn type_category(tcx: TyCtxt<'_>, t: Ty<'_>) -> Option<u32> {
match t.kind() {
ty::Bool => Some(0),
ty::Char => Some(1),
ty::Str => Some(2),
ty::Adt(def, _) if tcx.is_lang_item(def.did(), LangItem::String) => Some(2),
ty::Int(..)
| ty::Uint(..)
| ty::Float(..)
| ty::Infer(ty::IntVar(..) | ty::FloatVar(..)) => Some(4),
ty::Ref(..) | ty::RawPtr(..) => Some(5),
ty::Array(..) | ty::Slice(..) => Some(6),
ty::FnDef(..) | ty::FnPtr(..) => Some(7),
ty::Dynamic(..) => Some(8),
ty::Closure(..) => Some(9),
ty::Tuple(..) => Some(10),
ty::Param(..) => Some(11),
ty::Alias(ty::Projection, ..) => Some(12),
ty::Alias(ty::Inherent, ..) => Some(13),
ty::Alias(ty::Opaque, ..) => Some(14),
ty::Alias(ty::Weak, ..) => Some(15),
ty::Never => Some(16),
ty::Adt(..) => Some(17),
ty::Coroutine(..) => Some(18),
ty::Foreign(..) => Some(19),
ty::CoroutineWitness(..) => Some(20),
ty::CoroutineClosure(..) => Some(21),
ty::Pat(..) => Some(22),
ty::Placeholder(..) | ty::Bound(..) | ty::Infer(..) | ty::Error(_) => None,
}
}
let strip_references = |mut t: Ty<'tcx>| -> Ty<'tcx> {
loop {
match t.kind() {
ty::Ref(_, inner, _) | ty::RawPtr(inner, _) => t = *inner,
_ => break t,
}
}
};
if !ignoring_lifetimes {
a = strip_references(a);
b = strip_references(b);
}
let cat_a = type_category(self.tcx, a)?;
let cat_b = type_category(self.tcx, b)?;
if a == b {
Some(CandidateSimilarity::Exact { ignoring_lifetimes })
} else if cat_a == cat_b {
match (a.kind(), b.kind()) {
(ty::Adt(def_a, _), ty::Adt(def_b, _)) => def_a == def_b,
(ty::Foreign(def_a), ty::Foreign(def_b)) => def_a == def_b,
// Matching on references results in a lot of unhelpful
// suggestions, so let's just not do that for now.
//
// We still upgrade successful matches to `ignoring_lifetimes: true`
// to prioritize that impl.
(ty::Ref(..) | ty::RawPtr(..), ty::Ref(..) | ty::RawPtr(..)) => {
self.fuzzy_match_tys(a, b, true).is_some()
}
_ => true,
}
.then_some(CandidateSimilarity::Fuzzy { ignoring_lifetimes })
} else if ignoring_lifetimes {
None
} else {
self.fuzzy_match_tys(a, b, true)
}
}
pub(super) fn describe_closure(&self, kind: hir::ClosureKind) -> &'static str {
match kind {
hir::ClosureKind::Closure => "a closure",
hir::ClosureKind::Coroutine(hir::CoroutineKind::Coroutine(_)) => "a coroutine",
hir::ClosureKind::Coroutine(hir::CoroutineKind::Desugared(
hir::CoroutineDesugaring::Async,
hir::CoroutineSource::Block,
)) => "an async block",
hir::ClosureKind::Coroutine(hir::CoroutineKind::Desugared(
hir::CoroutineDesugaring::Async,
hir::CoroutineSource::Fn,
)) => "an async function",
hir::ClosureKind::Coroutine(hir::CoroutineKind::Desugared(
hir::CoroutineDesugaring::Async,
hir::CoroutineSource::Closure,
))
| hir::ClosureKind::CoroutineClosure(hir::CoroutineDesugaring::Async) => {
"an async closure"
}
hir::ClosureKind::Coroutine(hir::CoroutineKind::Desugared(
hir::CoroutineDesugaring::AsyncGen,
hir::CoroutineSource::Block,
)) => "an async gen block",
hir::ClosureKind::Coroutine(hir::CoroutineKind::Desugared(
hir::CoroutineDesugaring::AsyncGen,
hir::CoroutineSource::Fn,
)) => "an async gen function",
hir::ClosureKind::Coroutine(hir::CoroutineKind::Desugared(
hir::CoroutineDesugaring::AsyncGen,
hir::CoroutineSource::Closure,
))
| hir::ClosureKind::CoroutineClosure(hir::CoroutineDesugaring::AsyncGen) => {
"an async gen closure"
}
hir::ClosureKind::Coroutine(hir::CoroutineKind::Desugared(
hir::CoroutineDesugaring::Gen,
hir::CoroutineSource::Block,
)) => "a gen block",
hir::ClosureKind::Coroutine(hir::CoroutineKind::Desugared(
hir::CoroutineDesugaring::Gen,
hir::CoroutineSource::Fn,
)) => "a gen function",
hir::ClosureKind::Coroutine(hir::CoroutineKind::Desugared(
hir::CoroutineDesugaring::Gen,
hir::CoroutineSource::Closure,
))
| hir::ClosureKind::CoroutineClosure(hir::CoroutineDesugaring::Gen) => "a gen closure",
}
}
pub(super) fn find_similar_impl_candidates(
&self,
trait_pred: ty::PolyTraitPredicate<'tcx>,
) -> Vec<ImplCandidate<'tcx>> {
let mut candidates: Vec<_> = self
.tcx
.all_impls(trait_pred.def_id())
.filter_map(|def_id| {
let imp = self.tcx.impl_trait_header(def_id).unwrap();
if imp.polarity != ty::ImplPolarity::Positive
|| !self.tcx.is_user_visible_dep(def_id.krate)
{
return None;
}
let imp = imp.trait_ref.skip_binder();
self.fuzzy_match_tys(trait_pred.skip_binder().self_ty(), imp.self_ty(), false).map(
|similarity| ImplCandidate { trait_ref: imp, similarity, impl_def_id: def_id },
)
})
.collect();
if candidates.iter().any(|c| matches!(c.similarity, CandidateSimilarity::Exact { .. })) {
// If any of the candidates is a perfect match, we don't want to show all of them.
// This is particularly relevant for the case of numeric types (as they all have the
// same category).
candidates.retain(|c| matches!(c.similarity, CandidateSimilarity::Exact { .. }));
}
candidates
}
pub(super) fn report_similar_impl_candidates(
&self,
impl_candidates: &[ImplCandidate<'tcx>],
trait_ref: ty::PolyTraitRef<'tcx>,
body_def_id: LocalDefId,
err: &mut Diag<'_>,
other: bool,
param_env: ty::ParamEnv<'tcx>,
) -> bool {
let alternative_candidates = |def_id: DefId| {
let mut impl_candidates: Vec<_> = self
.tcx
.all_impls(def_id)
// ignore `do_not_recommend` items
.filter(|def_id| !self.tcx.do_not_recommend_impl(*def_id))
// Ignore automatically derived impls and `!Trait` impls.
.filter_map(|def_id| self.tcx.impl_trait_header(def_id))
.filter_map(|header| {
(header.polarity != ty::ImplPolarity::Negative
|| self.tcx.is_automatically_derived(def_id))
.then(|| header.trait_ref.instantiate_identity())
})
.filter(|trait_ref| {
let self_ty = trait_ref.self_ty();
// Avoid mentioning type parameters.
if let ty::Param(_) = self_ty.kind() {
false
}
// Avoid mentioning types that are private to another crate
else if let ty::Adt(def, _) = self_ty.peel_refs().kind() {
// FIXME(compiler-errors): This could be generalized, both to
// be more granular, and probably look past other `#[fundamental]`
// types, too.
self.tcx.visibility(def.did()).is_accessible_from(body_def_id, self.tcx)
} else {
true
}
})
.collect();
impl_candidates.sort_by_key(|tr| tr.to_string());
impl_candidates.dedup();
impl_candidates
};
// We'll check for the case where the reason for the mismatch is that the trait comes from
// one crate version and the type comes from another crate version, even though they both
// are from the same crate.
let trait_def_id = trait_ref.def_id();
let trait_name = self.tcx.item_name(trait_def_id);
let crate_name = self.tcx.crate_name(trait_def_id.krate);
if let Some(other_trait_def_id) = self.tcx.all_traits().find(|def_id| {
trait_name == self.tcx.item_name(trait_def_id)
&& trait_def_id.krate != def_id.krate
&& crate_name == self.tcx.crate_name(def_id.krate)
}) {
// We've found two different traits with the same name, same crate name, but
// different crate `DefId`. We highlight the traits.
let found_type =
if let ty::Adt(def, _) = trait_ref.self_ty().skip_binder().peel_refs().kind() {
Some(def.did())
} else {
None
};
let candidates = if impl_candidates.is_empty() {
alternative_candidates(trait_def_id)
} else {
impl_candidates.into_iter().map(|cand| cand.trait_ref).collect()
};
let mut span: MultiSpan = self.tcx.def_span(trait_def_id).into();
span.push_span_label(self.tcx.def_span(trait_def_id), "this is the required trait");
for (sp, label) in [trait_def_id, other_trait_def_id]
.iter()
.filter_map(|def_id| self.tcx.extern_crate(def_id.krate))
.map(|data| {
let dependency = if data.dependency_of == LOCAL_CRATE {
"direct dependency of the current crate".to_string()
} else {
let dep = self.tcx.crate_name(data.dependency_of);
format!("dependency of crate `{dep}`")
};
(
data.span,
format!(
"one version of crate `{crate_name}` is used here, as a {dependency}"
),
)
})
{
span.push_span_label(sp, label);
}
let mut points_at_type = false;
if let Some(found_type) = found_type {
span.push_span_label(
self.tcx.def_span(found_type),
"this type doesn't implement the required trait",
);
for trait_ref in candidates {
if let ty::Adt(def, _) = trait_ref.self_ty().peel_refs().kind()
&& let candidate_def_id = def.did()
&& let Some(name) = self.tcx.opt_item_name(candidate_def_id)
&& let Some(found) = self.tcx.opt_item_name(found_type)
&& name == found
&& candidate_def_id.krate != found_type.krate
&& self.tcx.crate_name(candidate_def_id.krate)
== self.tcx.crate_name(found_type.krate)
{
// A candidate was found of an item with the same name, from two separate
// versions of the same crate, let's clarify.
let candidate_span = self.tcx.def_span(candidate_def_id);
span.push_span_label(
candidate_span,
"this type implements the required trait",
);
points_at_type = true;
}
}
}
span.push_span_label(self.tcx.def_span(other_trait_def_id), "this is the found trait");
err.highlighted_span_note(span, vec![
StringPart::normal("there are ".to_string()),
StringPart::highlighted("multiple different versions".to_string()),
StringPart::normal(" of crate `".to_string()),
StringPart::highlighted(format!("{crate_name}")),
StringPart::normal("` in the dependency graph\n".to_string()),
]);
if points_at_type {
// We only clarify that the same type from different crate versions are not the
// same when we *find* the same type coming from different crate versions, otherwise
// it could be that it was a type provided by a different crate than the one that
// provides the trait, and mentioning this adds verbosity without clarification.
err.highlighted_note(vec![
StringPart::normal(
"two types coming from two different versions of the same crate are \
different types "
.to_string(),
),
StringPart::highlighted("even if they look the same".to_string()),
]);
}
err.highlighted_help(vec![
StringPart::normal("you can use `".to_string()),
StringPart::highlighted("cargo tree".to_string()),
StringPart::normal("` to explore your dependency tree".to_string()),
]);
// FIXME: this is a giant hack for the benefit of this specific diagnostic. Because
// we're so nested in method calls before the error gets emitted, bubbling a single bit
// flag informing the top level caller to stop adding extra detail to the diagnostic,
// would actually be harder to follow. So we do something naughty here: we consume the
// diagnostic, emit it and leave in its place a "delayed bug" that will continue being
// modified but won't actually be printed to end users. This *is not ideal*, but allows
// us to reduce the verbosity of an error that is already quite verbose and increase its
// specificity. Below we modify the main message as well, in a way that *could* break if
// the implementation of Diagnostics change significantly, but that would be caught with
// a make test failure when this diagnostic is tested.
err.primary_message(format!(
"{} because the trait comes from a different crate version",
err.messages[0].0.as_str().unwrap(),
));
let diag = err.clone();
err.downgrade_to_delayed_bug();
self.tcx.dcx().emit_diagnostic(diag);
return true;
}
if let [single] = &impl_candidates {
// If we have a single implementation, try to unify it with the trait ref
// that failed. This should uncover a better hint for what *is* implemented.
if self.probe(|_| {
let ocx = ObligationCtxt::new(self);
self.enter_forall(trait_ref, |obligation_trait_ref| {
let impl_args = self.fresh_args_for_item(DUMMY_SP, single.impl_def_id);
let impl_trait_ref = ocx.normalize(
&ObligationCause::dummy(),
param_env,
ty::EarlyBinder::bind(single.trait_ref).instantiate(self.tcx, impl_args),
);
ocx.register_obligations(
self.tcx
.predicates_of(single.impl_def_id)
.instantiate(self.tcx, impl_args)
.into_iter()
.map(|(clause, _)| {
Obligation::new(
self.tcx,
ObligationCause::dummy(),
param_env,
clause,
)
}),
);
if !ocx.select_where_possible().is_empty() {
return false;
}
let mut terrs = vec![];
for (obligation_arg, impl_arg) in
std::iter::zip(obligation_trait_ref.args, impl_trait_ref.args)
{
if (obligation_arg, impl_arg).references_error() {
return false;
}
if let Err(terr) =
ocx.eq(&ObligationCause::dummy(), param_env, impl_arg, obligation_arg)
{
terrs.push(terr);
}
if !ocx.select_where_possible().is_empty() {
return false;
}
}
// Literally nothing unified, just give up.
if terrs.len() == impl_trait_ref.args.len() {
return false;
}
let impl_trait_ref = self.resolve_vars_if_possible(impl_trait_ref);
if impl_trait_ref.references_error() {
return false;
}
if let [child, ..] = &err.children[..]
&& child.level == Level::Help
&& let Some(line) = child.messages.get(0)
&& let Some(line) = line.0.as_str()
&& line.starts_with("the trait")
&& line.contains("is not implemented for")
{
// HACK(estebank): we remove the pre-existing
// "the trait `X` is not implemented for" note, which only happens if there
// was a custom label. We do this because we want that note to always be the
// first, and making this logic run earlier will get tricky. For now, we
// instead keep the logic the same and modify the already constructed error
// to avoid the wording duplication.
err.children.remove(0);
}
let traits = self.cmp_traits(
obligation_trait_ref.def_id,
&obligation_trait_ref.args[1..],
impl_trait_ref.def_id,
&impl_trait_ref.args[1..],
);
let traits_content = (traits.0.content(), traits.1.content());
let types = self.cmp(obligation_trait_ref.self_ty(), impl_trait_ref.self_ty());
let types_content = (types.0.content(), types.1.content());
let mut msg = vec![StringPart::normal("the trait `")];
if traits_content.0 == traits_content.1 {
msg.push(StringPart::normal(
impl_trait_ref.print_trait_sugared().to_string(),
));
} else {
msg.extend(traits.0.0);
}
msg.extend([
StringPart::normal("` "),
StringPart::highlighted("is not"),
StringPart::normal(" implemented for `"),
]);
if types_content.0 == types_content.1 {
let ty =
self.tcx.short_ty_string(obligation_trait_ref.self_ty(), &mut None);
msg.push(StringPart::normal(ty));
} else {
msg.extend(types.0.0);
}
msg.push(StringPart::normal("`"));
if types_content.0 == types_content.1 {
msg.push(StringPart::normal("\nbut trait `"));
msg.extend(traits.1.0);
msg.extend([
StringPart::normal("` "),
StringPart::highlighted("is"),
StringPart::normal(" implemented for it"),
]);
} else if traits_content.0 == traits_content.1 {
msg.extend([
StringPart::normal("\nbut it "),
StringPart::highlighted("is"),
StringPart::normal(" implemented for `"),
]);
msg.extend(types.1.0);
msg.push(StringPart::normal("`"));
} else {
msg.push(StringPart::normal("\nbut trait `"));
msg.extend(traits.1.0);
msg.extend([
StringPart::normal("` "),
StringPart::highlighted("is"),
StringPart::normal(" implemented for `"),
]);
msg.extend(types.1.0);
msg.push(StringPart::normal("`"));
}
err.highlighted_help(msg);
if let [TypeError::Sorts(exp_found)] = &terrs[..] {
let exp_found = self.resolve_vars_if_possible(*exp_found);
err.highlighted_help(vec![
StringPart::normal("for that trait implementation, "),
StringPart::normal("expected `"),
StringPart::highlighted(exp_found.expected.to_string()),
StringPart::normal("`, found `"),
StringPart::highlighted(exp_found.found.to_string()),
StringPart::normal("`"),
]);
}
true
})
}) {
return true;
}
}
let other = if other { "other " } else { "" };
let report = |mut candidates: Vec<TraitRef<'tcx>>, err: &mut Diag<'_>| {
candidates.retain(|tr| !tr.references_error());
if candidates.is_empty() {
return false;
}
if let &[cand] = &candidates[..] {
let (desc, mention_castable) =
match (cand.self_ty().kind(), trait_ref.self_ty().skip_binder().kind()) {
(ty::FnPtr(..), ty::FnDef(..)) => {
(" implemented for fn pointer `", ", cast using `as`")
}
(ty::FnPtr(..), _) => (" implemented for fn pointer `", ""),
_ => (" implemented for `", ""),
};
err.highlighted_help(vec![
StringPart::normal(format!("the trait `{}` ", cand.print_trait_sugared())),
StringPart::highlighted("is"),
StringPart::normal(desc),
StringPart::highlighted(cand.self_ty().to_string()),
StringPart::normal("`"),
StringPart::normal(mention_castable),
]);
return true;
}
let trait_ref = TraitRef::identity(self.tcx, candidates[0].def_id);
// Check if the trait is the same in all cases. If so, we'll only show the type.
let mut traits: Vec<_> =
candidates.iter().map(|c| c.print_only_trait_path().to_string()).collect();
traits.sort();
traits.dedup();
// FIXME: this could use a better heuristic, like just checking
// that args[1..] is the same.
let all_traits_equal = traits.len() == 1;
let candidates: Vec<String> = candidates
.into_iter()
.map(|c| {
if all_traits_equal {
format!("\n {}", c.self_ty())
} else {
format!("\n `{}` implements `{}`", c.self_ty(), c.print_only_trait_path())
}
})
.collect();
let end = if candidates.len() <= 9 || self.tcx.sess.opts.verbose {
candidates.len()
} else {
8
};
err.help(format!(
"the following {other}types implement trait `{}`:{}{}",
trait_ref.print_trait_sugared(),
candidates[..end].join(""),
if candidates.len() > 9 && !self.tcx.sess.opts.verbose {
format!("\nand {} others", candidates.len() - 8)
} else {
String::new()
}
));
true
};
// we filter before checking if `impl_candidates` is empty
// to get the fallback solution if we filtered out any impls
let impl_candidates = impl_candidates
.into_iter()
.cloned()
.filter(|cand| !self.tcx.do_not_recommend_impl(cand.impl_def_id))
.collect::<Vec<_>>();
let def_id = trait_ref.def_id();
if impl_candidates.is_empty() {
if self.tcx.trait_is_auto(def_id)
|| self.tcx.lang_items().iter().any(|(_, id)| id == def_id)
|| self.tcx.get_diagnostic_name(def_id).is_some()
{
// Mentioning implementers of `Copy`, `Debug` and friends is not useful.
return false;
}
return report(alternative_candidates(def_id), err);
}
// Sort impl candidates so that ordering is consistent for UI tests.
// because the ordering of `impl_candidates` may not be deterministic:
// https://github.com/rust-lang/rust/pull/57475#issuecomment-455519507
//
// Prefer more similar candidates first, then sort lexicographically
// by their normalized string representation.
let mut impl_candidates: Vec<_> = impl_candidates
.iter()
.cloned()
.filter(|cand| !cand.trait_ref.references_error())
.map(|mut cand| {
// Normalize the trait ref in its *own* param-env so
// that consts are folded and any trivial projections
// are normalized.
cand.trait_ref = self
.tcx
.try_normalize_erasing_regions(
ty::TypingEnv::non_body_analysis(self.tcx, cand.impl_def_id),
cand.trait_ref,
)
.unwrap_or(cand.trait_ref);
cand
})
.collect();
impl_candidates.sort_by_key(|cand| (cand.similarity, cand.trait_ref.to_string()));
let mut impl_candidates: Vec<_> =
impl_candidates.into_iter().map(|cand| cand.trait_ref).collect();
impl_candidates.dedup();
report(impl_candidates, err)
}
fn report_similar_impl_candidates_for_root_obligation(
&self,
obligation: &PredicateObligation<'tcx>,
trait_predicate: ty::Binder<'tcx, ty::TraitPredicate<'tcx>>,
body_def_id: LocalDefId,
err: &mut Diag<'_>,
) {
// This is *almost* equivalent to
// `obligation.cause.code().peel_derives()`, but it gives us the
// trait predicate for that corresponding root obligation. This
// lets us get a derived obligation from a type parameter, like
// when calling `string.strip_suffix(p)` where `p` is *not* an
// implementer of `Pattern<'_>`.
let mut code = obligation.cause.code();
let mut trait_pred = trait_predicate;
let mut peeled = false;
while let Some((parent_code, parent_trait_pred)) = code.parent() {
code = parent_code;
if let Some(parent_trait_pred) = parent_trait_pred {
trait_pred = parent_trait_pred;
peeled = true;
}
}
let def_id = trait_pred.def_id();
// Mention *all* the `impl`s for the *top most* obligation, the
// user might have meant to use one of them, if any found. We skip
// auto-traits or fundamental traits that might not be exactly what
// the user might expect to be presented with. Instead this is
// useful for less general traits.
if peeled
&& !self.tcx.trait_is_auto(def_id)
&& !self.tcx.lang_items().iter().any(|(_, id)| id == def_id)
{
let trait_ref = trait_pred.to_poly_trait_ref();
let impl_candidates = self.find_similar_impl_candidates(trait_pred);
self.report_similar_impl_candidates(
&impl_candidates,
trait_ref,
body_def_id,
err,
true,
obligation.param_env,
);
}
}
/// Gets the parent trait chain start
fn get_parent_trait_ref(
&self,
code: &ObligationCauseCode<'tcx>,
) -> Option<(Ty<'tcx>, Option<Span>)> {
match code {
ObligationCauseCode::BuiltinDerived(data) => {
let parent_trait_ref = self.resolve_vars_if_possible(data.parent_trait_pred);
match self.get_parent_trait_ref(&data.parent_code) {
Some(t) => Some(t),
None => {
let ty = parent_trait_ref.skip_binder().self_ty();
let span = TyCategory::from_ty(self.tcx, ty)
.map(|(_, def_id)| self.tcx.def_span(def_id));
Some((ty, span))
}
}
}
ObligationCauseCode::FunctionArg { parent_code, .. } => {
self.get_parent_trait_ref(parent_code)
}
_ => None,
}
}
/// If the `Self` type of the unsatisfied trait `trait_ref` implements a trait
/// with the same path as `trait_ref`, a help message about
/// a probable version mismatch is added to `err`
fn note_version_mismatch(&self, err: &mut Diag<'_>, trait_ref: ty::PolyTraitRef<'tcx>) -> bool {
let get_trait_impls = |trait_def_id| {
let mut trait_impls = vec![];
self.tcx.for_each_relevant_impl(
trait_def_id,
trait_ref.skip_binder().self_ty(),
|impl_def_id| {
trait_impls.push(impl_def_id);
},
);
trait_impls
};
let required_trait_path = self.tcx.def_path_str(trait_ref.def_id());
let traits_with_same_path: UnordSet<_> = self
.tcx
.all_traits()
.filter(|trait_def_id| *trait_def_id != trait_ref.def_id())
.map(|trait_def_id| (self.tcx.def_path_str(trait_def_id), trait_def_id))
.filter(|(p, _)| *p == required_trait_path)
.collect();
let traits_with_same_path =
traits_with_same_path.into_items().into_sorted_stable_ord_by_key(|(p, _)| p);
let mut suggested = false;
for (_, trait_with_same_path) in traits_with_same_path {
let trait_impls = get_trait_impls(trait_with_same_path);
if trait_impls.is_empty() {
continue;
}
let impl_spans: Vec<_> =
trait_impls.iter().map(|impl_def_id| self.tcx.def_span(*impl_def_id)).collect();
err.span_help(
impl_spans,
format!("trait impl{} with same name found", pluralize!(trait_impls.len())),
);
let trait_crate = self.tcx.crate_name(trait_with_same_path.krate);
let crate_msg =
format!("perhaps two different versions of crate `{trait_crate}` are being used?");
err.note(crate_msg);
suggested = true;
}
suggested
}
/// Creates a `PredicateObligation` with `new_self_ty` replacing the existing type in the
/// `trait_ref`.
///
/// For this to work, `new_self_ty` must have no escaping bound variables.
pub(super) fn mk_trait_obligation_with_new_self_ty(
&self,
param_env: ty::ParamEnv<'tcx>,
trait_ref_and_ty: ty::Binder<'tcx, (ty::TraitPredicate<'tcx>, Ty<'tcx>)>,
) -> PredicateObligation<'tcx> {
let trait_pred =
trait_ref_and_ty.map_bound(|(tr, new_self_ty)| tr.with_self_ty(self.tcx, new_self_ty));
Obligation::new(self.tcx, ObligationCause::dummy(), param_env, trait_pred)
}
/// Returns `true` if the trait predicate may apply for *some* assignment
/// to the type parameters.
fn predicate_can_apply(
&self,
param_env: ty::ParamEnv<'tcx>,
pred: ty::PolyTraitPredicate<'tcx>,
) -> bool {
struct ParamToVarFolder<'a, 'tcx> {
infcx: &'a InferCtxt<'tcx>,
var_map: FxHashMap<Ty<'tcx>, Ty<'tcx>>,
}
impl<'a, 'tcx> TypeFolder<TyCtxt<'tcx>> for ParamToVarFolder<'a, 'tcx> {
fn cx(&self) -> TyCtxt<'tcx> {
self.infcx.tcx
}
fn fold_ty(&mut self, ty: Ty<'tcx>) -> Ty<'tcx> {
if let ty::Param(_) = *ty.kind() {
let infcx = self.infcx;
*self.var_map.entry(ty).or_insert_with(|| infcx.next_ty_var(DUMMY_SP))
} else {
ty.super_fold_with(self)
}
}
}
self.probe(|_| {
let cleaned_pred =
pred.fold_with(&mut ParamToVarFolder { infcx: self, var_map: Default::default() });
let InferOk { value: cleaned_pred, .. } =
self.infcx.at(&ObligationCause::dummy(), param_env).normalize(cleaned_pred);
let obligation =
Obligation::new(self.tcx, ObligationCause::dummy(), param_env, cleaned_pred);
self.predicate_may_hold(&obligation)
})
}
pub fn note_obligation_cause(
&self,
err: &mut Diag<'_>,
obligation: &PredicateObligation<'tcx>,
) {
// First, attempt to add note to this error with an async-await-specific
// message, and fall back to regular note otherwise.
if !self.maybe_note_obligation_cause_for_async_await(err, obligation) {
let mut long_ty_file = None;
self.note_obligation_cause_code(
obligation.cause.body_id,
err,
obligation.predicate,
obligation.param_env,
obligation.cause.code(),
&mut vec![],
&mut Default::default(),
&mut long_ty_file,
);
if let Some(file) = long_ty_file {
err.note(format!(
"the full name for the type has been written to '{}'",
file.display(),
));
err.note("consider using `--verbose` to print the full type name to the console");
}
self.suggest_unsized_bound_if_applicable(err, obligation);
if let Some(span) = err.span.primary_span()
&& let Some(mut diag) =
self.dcx().steal_non_err(span, StashKey::AssociatedTypeSuggestion)
&& let Suggestions::Enabled(ref mut s1) = err.suggestions
&& let Suggestions::Enabled(ref mut s2) = diag.suggestions
{
s1.append(s2);
diag.cancel()
}
}
}
pub(super) fn is_recursive_obligation(
&self,
obligated_types: &mut Vec<Ty<'tcx>>,
cause_code: &ObligationCauseCode<'tcx>,
) -> bool {
if let ObligationCauseCode::BuiltinDerived(ref data) = cause_code {
let parent_trait_ref = self.resolve_vars_if_possible(data.parent_trait_pred);
let self_ty = parent_trait_ref.skip_binder().self_ty();
if obligated_types.iter().any(|ot| ot == &self_ty) {
return true;
}
if let ty::Adt(def, args) = self_ty.kind()
&& let [arg] = &args[..]
&& let ty::GenericArgKind::Type(ty) = arg.unpack()
&& let ty::Adt(inner_def, _) = ty.kind()
&& inner_def == def
{
return true;
}
}
false
}
fn get_standard_error_message(
&self,
trait_predicate: ty::PolyTraitPredicate<'tcx>,
message: Option<String>,
predicate_constness: Option<ty::BoundConstness>,
append_const_msg: Option<AppendConstMessage>,
post_message: String,
) -> String {
message
.and_then(|cannot_do_this| {
match (predicate_constness, append_const_msg) {
// do nothing if predicate is not const
(None, _) => Some(cannot_do_this),
// suggested using default post message
(
Some(ty::BoundConstness::Const | ty::BoundConstness::Maybe),
Some(AppendConstMessage::Default),
) => Some(format!("{cannot_do_this} in const contexts")),
// overridden post message
(
Some(ty::BoundConstness::Const | ty::BoundConstness::Maybe),
Some(AppendConstMessage::Custom(custom_msg, _)),
) => Some(format!("{cannot_do_this}{custom_msg}")),
// fallback to generic message
(Some(ty::BoundConstness::Const | ty::BoundConstness::Maybe), None) => None,
}
})
.unwrap_or_else(|| {
format!(
"the trait bound `{}` is not satisfied{post_message}",
trait_predicate.print_with_bound_constness(predicate_constness)
)
})
}
fn get_safe_transmute_error_and_reason(
&self,
obligation: PredicateObligation<'tcx>,
trait_ref: ty::PolyTraitRef<'tcx>,
span: Span,
) -> GetSafeTransmuteErrorAndReason {
use rustc_transmute::Answer;
self.probe(|_| {
// We don't assemble a transmutability candidate for types that are generic
// and we should have ambiguity for types that still have non-region infer.
if obligation.predicate.has_non_region_param() || obligation.has_non_region_infer() {
return GetSafeTransmuteErrorAndReason::Default;
}
// Erase regions because layout code doesn't particularly care about regions.
let trait_ref =
self.tcx.erase_regions(self.tcx.instantiate_bound_regions_with_erased(trait_ref));
let src_and_dst = rustc_transmute::Types {
dst: trait_ref.args.type_at(0),
src: trait_ref.args.type_at(1),
};
let ocx = ObligationCtxt::new(self);
let Ok(assume) = ocx.structurally_normalize_const(
&obligation.cause,
obligation.param_env,
trait_ref.args.const_at(2),
) else {
self.dcx().span_delayed_bug(
span,
"Unable to construct rustc_transmute::Assume where it was previously possible",
);
return GetSafeTransmuteErrorAndReason::Silent;
};
let Some(assume) =
rustc_transmute::Assume::from_const(self.infcx.tcx, obligation.param_env, assume)
else {
self.dcx().span_delayed_bug(
span,
"Unable to construct rustc_transmute::Assume where it was previously possible",
);
return GetSafeTransmuteErrorAndReason::Silent;
};
let dst = trait_ref.args.type_at(0);
let src = trait_ref.args.type_at(1);
let err_msg = format!("`{src}` cannot be safely transmuted into `{dst}`");
match rustc_transmute::TransmuteTypeEnv::new(self.infcx).is_transmutable(
obligation.cause,
src_and_dst,
assume,
) {
Answer::No(reason) => {
let safe_transmute_explanation = match reason {
rustc_transmute::Reason::SrcIsNotYetSupported => {
format!("analyzing the transmutability of `{src}` is not yet supported")
}
rustc_transmute::Reason::DstIsNotYetSupported => {
format!("analyzing the transmutability of `{dst}` is not yet supported")
}
rustc_transmute::Reason::DstIsBitIncompatible => {
format!(
"at least one value of `{src}` isn't a bit-valid value of `{dst}`"
)
}
rustc_transmute::Reason::DstUninhabited => {
format!("`{dst}` is uninhabited")
}
rustc_transmute::Reason::DstMayHaveSafetyInvariants => {
format!("`{dst}` may carry safety invariants")
}
rustc_transmute::Reason::DstIsTooBig => {
format!("the size of `{src}` is smaller than the size of `{dst}`")
}
rustc_transmute::Reason::DstRefIsTooBig { src, dst } => {
let src_size = src.size;
let dst_size = dst.size;
format!(
"the referent size of `{src}` ({src_size} bytes) \
is smaller than that of `{dst}` ({dst_size} bytes)"
)
}
rustc_transmute::Reason::SrcSizeOverflow => {
format!(
"values of the type `{src}` are too big for the target architecture"
)
}
rustc_transmute::Reason::DstSizeOverflow => {
format!(
"values of the type `{dst}` are too big for the target architecture"
)
}
rustc_transmute::Reason::DstHasStricterAlignment {
src_min_align,
dst_min_align,
} => {
format!(
"the minimum alignment of `{src}` ({src_min_align}) should \
be greater than that of `{dst}` ({dst_min_align})"
)
}
rustc_transmute::Reason::DstIsMoreUnique => {
format!(
"`{src}` is a shared reference, but `{dst}` is a unique reference"
)
}
// Already reported by rustc
rustc_transmute::Reason::TypeError => {
return GetSafeTransmuteErrorAndReason::Silent;
}
rustc_transmute::Reason::SrcLayoutUnknown => {
format!("`{src}` has an unknown layout")
}
rustc_transmute::Reason::DstLayoutUnknown => {
format!("`{dst}` has an unknown layout")
}
};
GetSafeTransmuteErrorAndReason::Error {
err_msg,
safe_transmute_explanation: Some(safe_transmute_explanation),
}
}
// Should never get a Yes at this point! We already ran it before, and did not get a Yes.
Answer::Yes => span_bug!(
span,
"Inconsistent rustc_transmute::is_transmutable(...) result, got Yes",
),
// Reached when a different obligation (namely `Freeze`) causes the
// transmutability analysis to fail. In this case, silence the
// transmutability error message in favor of that more specific
// error.
Answer::If(_) => GetSafeTransmuteErrorAndReason::Error {
err_msg,
safe_transmute_explanation: None,
},
}
})
}
fn add_tuple_trait_message(
&self,
obligation_cause_code: &ObligationCauseCode<'tcx>,
err: &mut Diag<'_>,
) {
match obligation_cause_code {
ObligationCauseCode::RustCall => {
err.primary_message("functions with the \"rust-call\" ABI must take a single non-self tuple argument");
}
ObligationCauseCode::WhereClause(def_id, _) if self.tcx.is_fn_trait(*def_id) => {
err.code(E0059);
err.primary_message(format!(
"type parameter to bare `{}` trait must be a tuple",
self.tcx.def_path_str(*def_id)
));
}
_ => {}
}
}
fn try_to_add_help_message(
&self,
root_obligation: &PredicateObligation<'tcx>,
obligation: &PredicateObligation<'tcx>,
trait_predicate: ty::PolyTraitPredicate<'tcx>,
err: &mut Diag<'_>,
span: Span,
is_fn_trait: bool,
suggested: bool,
unsatisfied_const: bool,
) {
let body_def_id = obligation.cause.body_id;
let span = if let ObligationCauseCode::BinOp { rhs_span: Some(rhs_span), .. } =
obligation.cause.code()
{
*rhs_span
} else {
span
};
// Try to report a help message
let trait_def_id = trait_predicate.def_id();
if is_fn_trait
&& let Ok((implemented_kind, params)) = self.type_implements_fn_trait(
obligation.param_env,
trait_predicate.self_ty(),
trait_predicate.skip_binder().polarity,
)
{
self.add_help_message_for_fn_trait(
trait_predicate.to_poly_trait_ref(),
err,
implemented_kind,
params,
);
} else if !trait_predicate.has_non_region_infer()
&& self.predicate_can_apply(obligation.param_env, trait_predicate)
{
// If a where-clause may be useful, remind the
// user that they can add it.
//
// don't display an on-unimplemented note, as
// these notes will often be of the form
// "the type `T` can't be frobnicated"
// which is somewhat confusing.
self.suggest_restricting_param_bound(
err,
trait_predicate,
None,
obligation.cause.body_id,
);
} else if trait_def_id.is_local()
&& self.tcx.trait_impls_of(trait_def_id).is_empty()
&& !self.tcx.trait_is_auto(trait_def_id)
&& !self.tcx.trait_is_alias(trait_def_id)
&& trait_predicate.polarity() == ty::PredicatePolarity::Positive
{
err.span_help(
self.tcx.def_span(trait_def_id),
crate::fluent_generated::trait_selection_trait_has_no_impls,
);
} else if !suggested
&& !unsatisfied_const
&& trait_predicate.polarity() == ty::PredicatePolarity::Positive
{
// Can't show anything else useful, try to find similar impls.
let impl_candidates = self.find_similar_impl_candidates(trait_predicate);
if !self.report_similar_impl_candidates(
&impl_candidates,
trait_predicate.to_poly_trait_ref(),
body_def_id,
err,
true,
obligation.param_env,
) {
self.report_similar_impl_candidates_for_root_obligation(
obligation,
trait_predicate,
body_def_id,
err,
);
}
self.suggest_convert_to_slice(
err,
obligation,
trait_predicate.to_poly_trait_ref(),
impl_candidates.as_slice(),
span,
);
self.suggest_tuple_wrapping(err, root_obligation, obligation);
}
}
fn add_help_message_for_fn_trait(
&self,
trait_ref: ty::PolyTraitRef<'tcx>,
err: &mut Diag<'_>,
implemented_kind: ty::ClosureKind,
params: ty::Binder<'tcx, Ty<'tcx>>,
) {
// If the type implements `Fn`, `FnMut`, or `FnOnce`, suppress the following
// suggestion to add trait bounds for the type, since we only typically implement
// these traits once.
// Note if the `FnMut` or `FnOnce` is less general than the trait we're trying
// to implement.
let selected_kind = self
.tcx
.fn_trait_kind_from_def_id(trait_ref.def_id())
.expect("expected to map DefId to ClosureKind");
if !implemented_kind.extends(selected_kind) {
err.note(format!(
"`{}` implements `{}`, but it must implement `{}`, which is more general",
trait_ref.skip_binder().self_ty(),
implemented_kind,
selected_kind
));
}
// Note any argument mismatches
let given_ty = params.skip_binder();
let expected_ty = trait_ref.skip_binder().args.type_at(1);
if let ty::Tuple(given) = given_ty.kind()
&& let ty::Tuple(expected) = expected_ty.kind()
{
if expected.len() != given.len() {
// Note number of types that were expected and given
err.note(
format!(
"expected a closure taking {} argument{}, but one taking {} argument{} was given",
given.len(),
pluralize!(given.len()),
expected.len(),
pluralize!(expected.len()),
)
);
} else if !self.same_type_modulo_infer(given_ty, expected_ty) {
// Print type mismatch
let (expected_args, given_args) = self.cmp(given_ty, expected_ty);
err.note_expected_found(
&"a closure with arguments",
expected_args,
&"a closure with arguments",
given_args,
);
}
}
}
fn maybe_add_note_for_unsatisfied_const(
&self,
_trait_predicate: ty::PolyTraitPredicate<'tcx>,
_err: &mut Diag<'_>,
_span: Span,
) -> UnsatisfiedConst {
let unsatisfied_const = UnsatisfiedConst(false);
// FIXME(const_trait_impl)
unsatisfied_const
}
fn report_closure_error(
&self,
obligation: &PredicateObligation<'tcx>,
closure_def_id: DefId,
found_kind: ty::ClosureKind,
kind: ty::ClosureKind,
trait_prefix: &'static str,
) -> Diag<'a> {
let closure_span = self.tcx.def_span(closure_def_id);
let mut err = ClosureKindMismatch {
closure_span,
expected: kind,
found: found_kind,
cause_span: obligation.cause.span,
trait_prefix,
fn_once_label: None,
fn_mut_label: None,
};
// Additional context information explaining why the closure only implements
// a particular trait.
if let Some(typeck_results) = &self.typeck_results {
let hir_id = self.tcx.local_def_id_to_hir_id(closure_def_id.expect_local());
match (found_kind, typeck_results.closure_kind_origins().get(hir_id)) {
(ty::ClosureKind::FnOnce, Some((span, place))) => {
err.fn_once_label = Some(ClosureFnOnceLabel {
span: *span,
place: ty::place_to_string_for_capture(self.tcx, place),
})
}
(ty::ClosureKind::FnMut, Some((span, place))) => {
err.fn_mut_label = Some(ClosureFnMutLabel {
span: *span,
place: ty::place_to_string_for_capture(self.tcx, place),
})
}
_ => {}
}
}
self.dcx().create_err(err)
}
fn report_cyclic_signature_error(
&self,
obligation: &PredicateObligation<'tcx>,
found_trait_ref: ty::TraitRef<'tcx>,
expected_trait_ref: ty::TraitRef<'tcx>,
terr: TypeError<'tcx>,
) -> Diag<'a> {
let self_ty = found_trait_ref.self_ty();
let (cause, terr) = if let ty::Closure(def_id, _) = self_ty.kind() {
(
ObligationCause::dummy_with_span(self.tcx.def_span(def_id)),
TypeError::CyclicTy(self_ty),
)
} else {
(obligation.cause.clone(), terr)
};
self.report_and_explain_type_error(
TypeTrace::trait_refs(&cause, true, expected_trait_ref, found_trait_ref),
obligation.param_env,
terr,
)
}
fn report_opaque_type_auto_trait_leakage(
&self,
obligation: &PredicateObligation<'tcx>,
def_id: DefId,
) -> ErrorGuaranteed {
let name = match self.tcx.local_opaque_ty_origin(def_id.expect_local()) {
hir::OpaqueTyOrigin::FnReturn { .. } | hir::OpaqueTyOrigin::AsyncFn { .. } => {
"opaque type".to_string()
}
hir::OpaqueTyOrigin::TyAlias { .. } => {
format!("`{}`", self.tcx.def_path_debug_str(def_id))
}
};
let mut err = self.dcx().struct_span_err(
obligation.cause.span,
format!("cannot check whether the hidden type of {name} satisfies auto traits"),
);
err.note(
"fetching the hidden types of an opaque inside of the defining scope is not supported. \
You can try moving the opaque type and the item that actually registers a hidden type into a new submodule",
);
err.span_note(self.tcx.def_span(def_id), "opaque type is declared here");
self.note_obligation_cause(&mut err, &obligation);
self.point_at_returns_when_relevant(&mut err, &obligation);
self.dcx().try_steal_replace_and_emit_err(self.tcx.def_span(def_id), StashKey::Cycle, err)
}
fn report_signature_mismatch_error(
&self,
obligation: &PredicateObligation<'tcx>,
span: Span,
found_trait_ref: ty::TraitRef<'tcx>,
expected_trait_ref: ty::TraitRef<'tcx>,
) -> Result<Diag<'a>, ErrorGuaranteed> {
let found_trait_ref = self.resolve_vars_if_possible(found_trait_ref);
let expected_trait_ref = self.resolve_vars_if_possible(expected_trait_ref);
expected_trait_ref.self_ty().error_reported()?;
let found_trait_ty = found_trait_ref.self_ty();
let found_did = match *found_trait_ty.kind() {
ty::Closure(did, _) | ty::FnDef(did, _) | ty::Coroutine(did, ..) => Some(did),
_ => None,
};
let found_node = found_did.and_then(|did| self.tcx.hir().get_if_local(did));
let found_span = found_did.and_then(|did| self.tcx.hir().span_if_local(did));
if !self.reported_signature_mismatch.borrow_mut().insert((span, found_span)) {
// We check closures twice, with obligations flowing in different directions,
// but we want to complain about them only once.
return Err(self.dcx().span_delayed_bug(span, "already_reported"));
}
let mut not_tupled = false;
let found = match found_trait_ref.args.type_at(1).kind() {
ty::Tuple(tys) => vec![ArgKind::empty(); tys.len()],
_ => {
not_tupled = true;
vec![ArgKind::empty()]
}
};
let expected_ty = expected_trait_ref.args.type_at(1);
let expected = match expected_ty.kind() {
ty::Tuple(tys) => {
tys.iter().map(|t| ArgKind::from_expected_ty(t, Some(span))).collect()
}
_ => {
not_tupled = true;
vec![ArgKind::Arg("_".to_owned(), expected_ty.to_string())]
}
};
// If this is a `Fn` family trait and either the expected or found
// is not tupled, then fall back to just a regular mismatch error.
// This shouldn't be common unless manually implementing one of the
// traits manually, but don't make it more confusing when it does
// happen.
if Some(expected_trait_ref.def_id) != self.tcx.lang_items().coroutine_trait() && not_tupled
{
return Ok(self.report_and_explain_type_error(
TypeTrace::trait_refs(&obligation.cause, true, expected_trait_ref, found_trait_ref),
obligation.param_env,
ty::error::TypeError::Mismatch,
));
}
if found.len() != expected.len() {
let (closure_span, closure_arg_span, found) = found_did
.and_then(|did| {
let node = self.tcx.hir().get_if_local(did)?;
let (found_span, closure_arg_span, found) = self.get_fn_like_arguments(node)?;
Some((Some(found_span), closure_arg_span, found))
})
.unwrap_or((found_span, None, found));
// If the coroutine take a single () as its argument,
// the trait argument would found the coroutine take 0 arguments,
// but get_fn_like_arguments would give 1 argument.
// This would result in "Expected to take 1 argument, but it takes 1 argument".
// Check again to avoid this.
if found.len() != expected.len() {
return Ok(self.report_arg_count_mismatch(
span,
closure_span,
expected,
found,
found_trait_ty.is_closure(),
closure_arg_span,
));
}
}
Ok(self.report_closure_arg_mismatch(
span,
found_span,
found_trait_ref,
expected_trait_ref,
obligation.cause.code(),
found_node,
obligation.param_env,
))
}
/// Given some node representing a fn-like thing in the HIR map,
/// returns a span and `ArgKind` information that describes the
/// arguments it expects. This can be supplied to
/// `report_arg_count_mismatch`.
pub fn get_fn_like_arguments(
&self,
node: Node<'_>,
) -> Option<(Span, Option<Span>, Vec<ArgKind>)> {
let sm = self.tcx.sess.source_map();
let hir = self.tcx.hir();
Some(match node {
Node::Expr(&hir::Expr {
kind: hir::ExprKind::Closure(&hir::Closure { body, fn_decl_span, fn_arg_span, .. }),
..
}) => (
fn_decl_span,
fn_arg_span,
hir.body(body)
.params
.iter()
.map(|arg| {
if let hir::Pat { kind: hir::PatKind::Tuple(args, _), span, .. } = *arg.pat
{
Some(ArgKind::Tuple(
Some(span),
args.iter()
.map(|pat| {
sm.span_to_snippet(pat.span)
.ok()
.map(|snippet| (snippet, "_".to_owned()))
})
.collect::<Option<Vec<_>>>()?,
))
} else {
let name = sm.span_to_snippet(arg.pat.span).ok()?;
Some(ArgKind::Arg(name, "_".to_owned()))
}
})
.collect::<Option<Vec<ArgKind>>>()?,
),
Node::Item(&hir::Item { kind: hir::ItemKind::Fn(ref sig, ..), .. })
| Node::ImplItem(&hir::ImplItem { kind: hir::ImplItemKind::Fn(ref sig, _), .. })
| Node::TraitItem(&hir::TraitItem {
kind: hir::TraitItemKind::Fn(ref sig, _), ..
})
| Node::ForeignItem(&hir::ForeignItem {
kind: hir::ForeignItemKind::Fn(ref sig, _, _),
..
}) => (
sig.span,
None,
sig.decl
.inputs
.iter()
.map(|arg| match arg.kind {
hir::TyKind::Tup(tys) => {
ArgKind::Tuple(Some(arg.span), vec![
("_".to_owned(), "_".to_owned());
tys.len()
])
}
_ => ArgKind::empty(),
})
.collect::<Vec<ArgKind>>(),
),
Node::Ctor(variant_data) => {
let span = variant_data.ctor_hir_id().map_or(DUMMY_SP, |id| hir.span(id));
(span, None, vec![ArgKind::empty(); variant_data.fields().len()])
}
_ => panic!("non-FnLike node found: {node:?}"),
})
}
/// Reports an error when the number of arguments needed by a
/// trait match doesn't match the number that the expression
/// provides.
pub fn report_arg_count_mismatch(
&self,
span: Span,
found_span: Option<Span>,
expected_args: Vec<ArgKind>,
found_args: Vec<ArgKind>,
is_closure: bool,
closure_arg_span: Option<Span>,
) -> Diag<'a> {
let kind = if is_closure { "closure" } else { "function" };
let args_str = |arguments: &[ArgKind], other: &[ArgKind]| {
let arg_length = arguments.len();
let distinct = matches!(other, &[ArgKind::Tuple(..)]);
match (arg_length, arguments.get(0)) {
(1, Some(ArgKind::Tuple(_, fields))) => {
format!("a single {}-tuple as argument", fields.len())
}
_ => format!(
"{} {}argument{}",
arg_length,
if distinct && arg_length > 1 { "distinct " } else { "" },
pluralize!(arg_length)
),
}
};
let expected_str = args_str(&expected_args, &found_args);
let found_str = args_str(&found_args, &expected_args);
let mut err = struct_span_code_err!(
self.dcx(),
span,
E0593,
"{} is expected to take {}, but it takes {}",
kind,
expected_str,
found_str,
);
err.span_label(span, format!("expected {kind} that takes {expected_str}"));
if let Some(found_span) = found_span {
err.span_label(found_span, format!("takes {found_str}"));
// Suggest to take and ignore the arguments with expected_args_length `_`s if
// found arguments is empty (assume the user just wants to ignore args in this case).
// For example, if `expected_args_length` is 2, suggest `|_, _|`.
if found_args.is_empty() && is_closure {
let underscores = vec!["_"; expected_args.len()].join(", ");
err.span_suggestion_verbose(
closure_arg_span.unwrap_or(found_span),
format!(
"consider changing the closure to take and ignore the expected argument{}",
pluralize!(expected_args.len())
),
format!("|{underscores}|"),
Applicability::MachineApplicable,
);
}
if let &[ArgKind::Tuple(_, ref fields)] = &found_args[..] {
if fields.len() == expected_args.len() {
let sugg = fields
.iter()
.map(|(name, _)| name.to_owned())
.collect::<Vec<String>>()
.join(", ");
err.span_suggestion_verbose(
found_span,
"change the closure to take multiple arguments instead of a single tuple",
format!("|{sugg}|"),
Applicability::MachineApplicable,
);
}
}
if let &[ArgKind::Tuple(_, ref fields)] = &expected_args[..]
&& fields.len() == found_args.len()
&& is_closure
{
let sugg = format!(
"|({}){}|",
found_args
.iter()
.map(|arg| match arg {
ArgKind::Arg(name, _) => name.to_owned(),
_ => "_".to_owned(),
})
.collect::<Vec<String>>()
.join(", "),
// add type annotations if available
if found_args.iter().any(|arg| match arg {
ArgKind::Arg(_, ty) => ty != "_",
_ => false,
}) {
format!(
": ({})",
fields
.iter()
.map(|(_, ty)| ty.to_owned())
.collect::<Vec<String>>()
.join(", ")
)
} else {
String::new()
},
);
err.span_suggestion_verbose(
found_span,
"change the closure to accept a tuple instead of individual arguments",
sugg,
Applicability::MachineApplicable,
);
}
}
err
}
/// Checks if the type implements one of `Fn`, `FnMut`, or `FnOnce`
/// in that order, and returns the generic type corresponding to the
/// argument of that trait (corresponding to the closure arguments).
pub fn type_implements_fn_trait(
&self,
param_env: ty::ParamEnv<'tcx>,
ty: ty::Binder<'tcx, Ty<'tcx>>,
polarity: ty::PredicatePolarity,
) -> Result<(ty::ClosureKind, ty::Binder<'tcx, Ty<'tcx>>), ()> {
self.commit_if_ok(|_| {
for trait_def_id in [
self.tcx.lang_items().fn_trait(),
self.tcx.lang_items().fn_mut_trait(),
self.tcx.lang_items().fn_once_trait(),
] {
let Some(trait_def_id) = trait_def_id else { continue };
// Make a fresh inference variable so we can determine what the generic parameters
// of the trait are.
let var = self.next_ty_var(DUMMY_SP);
// FIXME(const_trait_impl)
let trait_ref = ty::TraitRef::new(self.tcx, trait_def_id, [ty.skip_binder(), var]);
let obligation = Obligation::new(
self.tcx,
ObligationCause::dummy(),
param_env,
ty.rebind(ty::TraitPredicate { trait_ref, polarity }),
);
let ocx = ObligationCtxt::new(self);
ocx.register_obligation(obligation);
if ocx.select_all_or_error().is_empty() {
return Ok((
self.tcx
.fn_trait_kind_from_def_id(trait_def_id)
.expect("expected to map DefId to ClosureKind"),
ty.rebind(self.resolve_vars_if_possible(var)),
));
}
}
Err(())
})
}
fn report_not_const_evaluatable_error(
&self,
obligation: &PredicateObligation<'tcx>,
span: Span,
) -> Result<Diag<'a>, ErrorGuaranteed> {
if !self.tcx.features().generic_const_exprs() {
let guar = self
.dcx()
.struct_span_err(span, "constant expression depends on a generic parameter")
// FIXME(const_generics): we should suggest to the user how they can resolve this
// issue. However, this is currently not actually possible
// (see https://github.com/rust-lang/rust/issues/66962#issuecomment-575907083).
//
// Note that with `feature(generic_const_exprs)` this case should not
// be reachable.
.with_note("this may fail depending on what value the parameter takes")
.emit();
return Err(guar);
}
match obligation.predicate.kind().skip_binder() {
ty::PredicateKind::Clause(ty::ClauseKind::ConstEvaluatable(ct)) => match ct.kind() {
ty::ConstKind::Unevaluated(uv) => {
let mut err =
self.dcx().struct_span_err(span, "unconstrained generic constant");
let const_span = self.tcx.def_span(uv.def);
let const_ty = self.tcx.type_of(uv.def).instantiate(self.tcx, uv.args);
let cast = if const_ty != self.tcx.types.usize { " as usize" } else { "" };
let msg = "try adding a `where` bound";
match self.tcx.sess.source_map().span_to_snippet(const_span) {
Ok(snippet) => {
let code = format!("[(); {snippet}{cast}]:");
let def_id = if let ObligationCauseCode::CompareImplItem {
trait_item_def_id,
..
} = obligation.cause.code()
{
trait_item_def_id.as_local()
} else {
Some(obligation.cause.body_id)
};
if let Some(def_id) = def_id
&& let Some(generics) = self.tcx.hir().get_generics(def_id)
{
err.span_suggestion_verbose(
generics.tail_span_for_predicate_suggestion(),
msg,
format!("{} {code}", generics.add_where_or_trailing_comma()),
Applicability::MaybeIncorrect,
);
} else {
err.help(format!("{msg}: where {code}"));
};
}
_ => {
err.help(msg);
}
};
Ok(err)
}
ty::ConstKind::Expr(_) => {
let err = self
.dcx()
.struct_span_err(span, format!("unconstrained generic constant `{ct}`"));
Ok(err)
}
_ => {
bug!("const evaluatable failed for non-unevaluated const `{ct:?}`");
}
},
_ => {
span_bug!(
span,
"unexpected non-ConstEvaluatable predicate, this should not be reachable"
)
}
}
}
}