1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721 722 723 724 725
use crate::astconv::AstConv;
use crate::errors::{
AssocTypeBindingNotAllowed, ManualImplementation, MissingTypeParams,
ParenthesizedFnTraitExpansion,
};
use rustc_data_structures::fx::FxHashMap;
use rustc_errors::{pluralize, struct_span_err, Applicability, Diagnostic, ErrorGuaranteed};
use rustc_hir as hir;
use rustc_hir::def_id::DefId;
use rustc_infer::traits::FulfillmentError;
use rustc_middle::ty::TyCtxt;
use rustc_middle::ty::{self, Ty};
use rustc_session::parse::feature_err;
use rustc_span::edit_distance::find_best_match_for_name;
use rustc_span::symbol::{sym, Ident};
use rustc_span::{Span, Symbol, DUMMY_SP};
use std::collections::BTreeSet;
impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
/// On missing type parameters, emit an E0393 error and provide a structured suggestion using
/// the type parameter's name as a placeholder.
pub(crate) fn complain_about_missing_type_params(
&self,
missing_type_params: Vec<Symbol>,
def_id: DefId,
span: Span,
empty_generic_args: bool,
) {
if missing_type_params.is_empty() {
return;
}
self.tcx().sess.emit_err(MissingTypeParams {
span,
def_span: self.tcx().def_span(def_id),
span_snippet: self.tcx().sess.source_map().span_to_snippet(span).ok(),
missing_type_params,
empty_generic_args,
});
}
/// When the code is using the `Fn` traits directly, instead of the `Fn(A) -> B` syntax, emit
/// an error and attempt to build a reasonable structured suggestion.
pub(crate) fn complain_about_internal_fn_trait(
&self,
span: Span,
trait_def_id: DefId,
trait_segment: &'_ hir::PathSegment<'_>,
is_impl: bool,
) {
if self.tcx().features().unboxed_closures {
return;
}
let trait_def = self.tcx().trait_def(trait_def_id);
if !trait_def.paren_sugar {
if trait_segment.args().parenthesized == hir::GenericArgsParentheses::ParenSugar {
// For now, require that parenthetical notation be used only with `Fn()` etc.
let mut err = feature_err(
&self.tcx().sess.parse_sess,
sym::unboxed_closures,
span,
"parenthetical notation is only stable when used with `Fn`-family traits",
);
err.emit();
}
return;
}
let sess = self.tcx().sess;
if trait_segment.args().parenthesized != hir::GenericArgsParentheses::ParenSugar {
// For now, require that parenthetical notation be used only with `Fn()` etc.
let mut err = feature_err(
&sess.parse_sess,
sym::unboxed_closures,
span,
"the precise format of `Fn`-family traits' type parameters is subject to change",
);
// Do not suggest the other syntax if we are in trait impl:
// the desugaring would contain an associated type constraint.
if !is_impl {
err.span_suggestion(
span,
"use parenthetical notation instead",
fn_trait_to_string(self.tcx(), trait_segment, true),
Applicability::MaybeIncorrect,
);
}
err.emit();
}
if is_impl {
let trait_name = self.tcx().def_path_str(trait_def_id);
self.tcx().sess.emit_err(ManualImplementation { span, trait_name });
}
}
pub(crate) fn complain_about_assoc_type_not_found<I>(
&self,
all_candidates: impl Fn() -> I,
ty_param_name: &str,
assoc_name: Ident,
span: Span,
) -> ErrorGuaranteed
where
I: Iterator<Item = ty::PolyTraitRef<'tcx>>,
{
// The fallback span is needed because `assoc_name` might be an `Fn()`'s `Output` without a
// valid span, so we point at the whole path segment instead.
let is_dummy = assoc_name.span == DUMMY_SP;
let mut err = struct_span_err!(
self.tcx().sess,
if is_dummy { span } else { assoc_name.span },
E0220,
"associated type `{}` not found for `{}`",
assoc_name,
ty_param_name
);
if is_dummy {
err.span_label(span, format!("associated type `{assoc_name}` not found"));
return err.emit();
}
let all_candidate_names: Vec<_> = all_candidates()
.flat_map(|r| self.tcx().associated_items(r.def_id()).in_definition_order())
.filter_map(|item| {
if !item.is_impl_trait_in_trait() && item.kind == ty::AssocKind::Type {
Some(item.name)
} else {
None
}
})
.collect();
if let Some(suggested_name) =
find_best_match_for_name(&all_candidate_names, assoc_name.name, None)
{
err.span_suggestion(
assoc_name.span,
"there is an associated type with a similar name",
suggested_name,
Applicability::MaybeIncorrect,
);
return err.emit();
}
// If we didn't find a good item in the supertraits (or couldn't get
// the supertraits), like in ItemCtxt, then look more generally from
// all visible traits. If there's one clear winner, just suggest that.
let visible_traits: Vec<_> = self
.tcx()
.all_traits()
.filter(|trait_def_id| {
let viz = self.tcx().visibility(*trait_def_id);
let def_id = self.item_def_id();
viz.is_accessible_from(def_id, self.tcx())
})
.collect();
let wider_candidate_names: Vec<_> = visible_traits
.iter()
.flat_map(|trait_def_id| {
self.tcx().associated_items(*trait_def_id).in_definition_order()
})
.filter_map(|item| {
if !item.is_impl_trait_in_trait() && item.kind == ty::AssocKind::Type {
Some(item.name)
} else {
None
}
})
.collect();
if let Some(suggested_name) =
find_best_match_for_name(&wider_candidate_names, assoc_name.name, None)
{
if let [best_trait] = visible_traits
.iter()
.filter(|trait_def_id| {
self.tcx()
.associated_items(*trait_def_id)
.filter_by_name_unhygienic(suggested_name)
.any(|item| item.kind == ty::AssocKind::Type)
})
.collect::<Vec<_>>()[..]
{
err.span_label(
assoc_name.span,
format!(
"there is a similarly named associated type `{suggested_name}` in the trait `{}`",
self.tcx().def_path_str(*best_trait)
),
);
return err.emit();
}
}
// If we still couldn't find any associated type, and only one associated type exists,
// suggests using it.
if all_candidate_names.len() == 1 {
// this should still compile, except on `#![feature(associated_type_defaults)]`
// where it could suggests `type A = Self::A`, thus recursing infinitely
let applicability = if self.tcx().features().associated_type_defaults {
Applicability::Unspecified
} else {
Applicability::MaybeIncorrect
};
err.span_suggestion(
assoc_name.span,
format!("`{ty_param_name}` has the following associated type"),
all_candidate_names.first().unwrap().to_string(),
applicability,
);
} else {
err.span_label(assoc_name.span, format!("associated type `{assoc_name}` not found"));
}
err.emit()
}
pub(crate) fn complain_about_ambiguous_inherent_assoc_type(
&self,
name: Ident,
candidates: Vec<DefId>,
span: Span,
) -> ErrorGuaranteed {
let mut err = struct_span_err!(
self.tcx().sess,
name.span,
E0034,
"multiple applicable items in scope"
);
err.span_label(name.span, format!("multiple `{name}` found"));
self.note_ambiguous_inherent_assoc_type(&mut err, candidates, span);
err.emit()
}
// FIXME(fmease): Heavily adapted from `rustc_hir_typeck::method::suggest`. Deduplicate.
fn note_ambiguous_inherent_assoc_type(
&self,
err: &mut Diagnostic,
candidates: Vec<DefId>,
span: Span,
) {
let tcx = self.tcx();
// Dynamic limit to avoid hiding just one candidate, which is silly.
let limit = if candidates.len() == 5 { 5 } else { 4 };
for (index, &item) in candidates.iter().take(limit).enumerate() {
let impl_ = tcx.impl_of_method(item).unwrap();
let note_span = if item.is_local() {
Some(tcx.def_span(item))
} else if impl_.is_local() {
Some(tcx.def_span(impl_))
} else {
None
};
let title = if candidates.len() > 1 {
format!("candidate #{}", index + 1)
} else {
"the candidate".into()
};
let impl_ty = tcx.at(span).type_of(impl_).instantiate_identity();
let note = format!("{title} is defined in an impl for the type `{impl_ty}`");
if let Some(span) = note_span {
err.span_note(span, note);
} else {
err.note(note);
}
}
if candidates.len() > limit {
err.note(format!("and {} others", candidates.len() - limit));
}
}
// FIXME(inherent_associated_types): Find similarly named associated types and suggest them.
pub(crate) fn complain_about_inherent_assoc_type_not_found(
&self,
name: Ident,
self_ty: Ty<'tcx>,
candidates: Vec<(DefId, (DefId, DefId))>,
fulfillment_errors: Vec<FulfillmentError<'tcx>>,
span: Span,
) -> ErrorGuaranteed {
// FIXME(fmease): This was copied in parts from an old version of `rustc_hir_typeck::method::suggest`.
// Either
// * update this code by applying changes similar to #106702 or by taking a
// Vec<(DefId, (DefId, DefId), Option<Vec<FulfillmentError<'tcx>>>)> or
// * deduplicate this code across the two crates.
let tcx = self.tcx();
let adt_did = self_ty.ty_adt_def().map(|def| def.did());
let add_def_label = |err: &mut Diagnostic| {
if let Some(did) = adt_did {
err.span_label(
tcx.def_span(did),
format!("associated item `{name}` not found for this {}", tcx.def_descr(did)),
);
}
};
if fulfillment_errors.is_empty() {
// FIXME(fmease): Copied from `rustc_hir_typeck::method::probe`. Deduplicate.
let limit = if candidates.len() == 5 { 5 } else { 4 };
let type_candidates = candidates
.iter()
.take(limit)
.map(|&(impl_, _)| {
format!("- `{}`", tcx.at(span).type_of(impl_).instantiate_identity())
})
.collect::<Vec<_>>()
.join("\n");
let additional_types = if candidates.len() > limit {
format!("\nand {} more types", candidates.len() - limit)
} else {
String::new()
};
let mut err = struct_span_err!(
tcx.sess,
name.span,
E0220,
"associated type `{name}` not found for `{self_ty}` in the current scope"
);
err.span_label(name.span, format!("associated item not found in `{self_ty}`"));
err.note(format!(
"the associated type was found for\n{type_candidates}{additional_types}",
));
add_def_label(&mut err);
return err.emit();
}
let mut bound_spans = Vec::new();
let mut bound_span_label = |self_ty: Ty<'_>, obligation: &str, quiet: &str| {
let msg = format!(
"doesn't satisfy `{}`",
if obligation.len() > 50 { quiet } else { obligation }
);
match &self_ty.kind() {
// Point at the type that couldn't satisfy the bound.
ty::Adt(def, _) => bound_spans.push((tcx.def_span(def.did()), msg)),
// Point at the trait object that couldn't satisfy the bound.
ty::Dynamic(preds, _, _) => {
for pred in preds.iter() {
match pred.skip_binder() {
ty::ExistentialPredicate::Trait(tr) => {
bound_spans.push((tcx.def_span(tr.def_id), msg.clone()))
}
ty::ExistentialPredicate::Projection(_)
| ty::ExistentialPredicate::AutoTrait(_) => {}
}
}
}
// Point at the closure that couldn't satisfy the bound.
ty::Closure(def_id, _) => {
bound_spans.push((tcx.def_span(*def_id), format!("doesn't satisfy `{quiet}`")))
}
_ => {}
}
};
let format_pred = |pred: ty::Predicate<'tcx>| {
let bound_predicate = pred.kind();
match bound_predicate.skip_binder() {
ty::PredicateKind::Clause(ty::ClauseKind::Projection(pred)) => {
let pred = bound_predicate.rebind(pred);
// `<Foo as Iterator>::Item = String`.
let projection_ty = pred.skip_binder().projection_ty;
let args_with_infer_self = tcx.mk_args_from_iter(
std::iter::once(Ty::new_var(tcx, ty::TyVid::from_u32(0)).into())
.chain(projection_ty.args.iter().skip(1)),
);
let quiet_projection_ty =
tcx.mk_alias_ty(projection_ty.def_id, args_with_infer_self);
let term = pred.skip_binder().term;
let obligation = format!("{projection_ty} = {term}");
let quiet = format!("{quiet_projection_ty} = {term}");
bound_span_label(projection_ty.self_ty(), &obligation, &quiet);
Some((obligation, projection_ty.self_ty()))
}
ty::PredicateKind::Clause(ty::ClauseKind::Trait(poly_trait_ref)) => {
let p = poly_trait_ref.trait_ref;
let self_ty = p.self_ty();
let path = p.print_only_trait_path();
let obligation = format!("{self_ty}: {path}");
let quiet = format!("_: {path}");
bound_span_label(self_ty, &obligation, &quiet);
Some((obligation, self_ty))
}
_ => None,
}
};
// FIXME(fmease): `rustc_hir_typeck::method::suggest` uses a `skip_list` to filter out some bounds.
// I would do the same here if it didn't mean more code duplication.
let mut bounds: Vec<_> = fulfillment_errors
.into_iter()
.map(|error| error.root_obligation.predicate)
.filter_map(format_pred)
.map(|(p, _)| format!("`{p}`"))
.collect();
bounds.sort();
bounds.dedup();
let mut err = tcx.sess.struct_span_err(
name.span,
format!("the associated type `{name}` exists for `{self_ty}`, but its trait bounds were not satisfied")
);
if !bounds.is_empty() {
err.note(format!(
"the following trait bounds were not satisfied:\n{}",
bounds.join("\n")
));
}
err.span_label(
name.span,
format!("associated type cannot be referenced on `{self_ty}` due to unsatisfied trait bounds")
);
bound_spans.sort();
bound_spans.dedup();
for (span, msg) in bound_spans {
if !tcx.sess.source_map().is_span_accessible(span) {
continue;
}
err.span_label(span, msg);
}
add_def_label(&mut err);
err.emit()
}
/// When there are any missing associated types, emit an E0191 error and attempt to supply a
/// reasonable suggestion on how to write it. For the case of multiple associated types in the
/// same trait bound have the same name (as they come from different supertraits), we instead
/// emit a generic note suggesting using a `where` clause to constraint instead.
pub(crate) fn complain_about_missing_associated_types(
&self,
associated_types: FxHashMap<Span, BTreeSet<DefId>>,
potential_assoc_types: Vec<Span>,
trait_bounds: &[hir::PolyTraitRef<'_>],
) {
if associated_types.values().all(|v| v.is_empty()) {
return;
}
let tcx = self.tcx();
// FIXME: Marked `mut` so that we can replace the spans further below with a more
// appropriate one, but this should be handled earlier in the span assignment.
let mut associated_types: FxHashMap<Span, Vec<_>> = associated_types
.into_iter()
.map(|(span, def_ids)| {
(span, def_ids.into_iter().map(|did| tcx.associated_item(did)).collect())
})
.collect();
let mut names = vec![];
// Account for things like `dyn Foo + 'a`, like in tests `issue-22434.rs` and
// `issue-22560.rs`.
let mut trait_bound_spans: Vec<Span> = vec![];
for (span, items) in &associated_types {
if !items.is_empty() {
trait_bound_spans.push(*span);
}
for assoc_item in items {
let trait_def_id = assoc_item.container_id(tcx);
names.push(format!(
"`{}` (from trait `{}`)",
assoc_item.name,
tcx.def_path_str(trait_def_id),
));
}
}
if let ([], [bound]) = (&potential_assoc_types[..], &trait_bounds) {
match bound.trait_ref.path.segments {
// FIXME: `trait_ref.path.span` can point to a full path with multiple
// segments, even though `trait_ref.path.segments` is of length `1`. Work
// around that bug here, even though it should be fixed elsewhere.
// This would otherwise cause an invalid suggestion. For an example, look at
// `tests/ui/issues/issue-28344.rs` where instead of the following:
//
// error[E0191]: the value of the associated type `Output`
// (from trait `std::ops::BitXor`) must be specified
// --> $DIR/issue-28344.rs:4:17
// |
// LL | let x: u8 = BitXor::bitor(0 as u8, 0 as u8);
// | ^^^^^^ help: specify the associated type:
// | `BitXor<Output = Type>`
//
// we would output:
//
// error[E0191]: the value of the associated type `Output`
// (from trait `std::ops::BitXor`) must be specified
// --> $DIR/issue-28344.rs:4:17
// |
// LL | let x: u8 = BitXor::bitor(0 as u8, 0 as u8);
// | ^^^^^^^^^^^^^ help: specify the associated type:
// | `BitXor::bitor<Output = Type>`
[segment] if segment.args.is_none() => {
trait_bound_spans = vec![segment.ident.span];
associated_types = associated_types
.into_values()
.map(|items| (segment.ident.span, items))
.collect();
}
_ => {}
}
}
names.sort();
trait_bound_spans.sort();
let mut err = struct_span_err!(
tcx.sess,
trait_bound_spans,
E0191,
"the value of the associated type{} {} must be specified",
pluralize!(names.len()),
names.join(", "),
);
let mut suggestions = vec![];
let mut types_count = 0;
let mut where_constraints = vec![];
let mut already_has_generics_args_suggestion = false;
for (span, assoc_items) in &associated_types {
let mut names: FxHashMap<_, usize> = FxHashMap::default();
for item in assoc_items {
types_count += 1;
*names.entry(item.name).or_insert(0) += 1;
}
let mut dupes = false;
for item in assoc_items {
let prefix = if names[&item.name] > 1 {
let trait_def_id = item.container_id(tcx);
dupes = true;
format!("{}::", tcx.def_path_str(trait_def_id))
} else {
String::new()
};
if let Some(sp) = tcx.hir().span_if_local(item.def_id) {
err.span_label(sp, format!("`{}{}` defined here", prefix, item.name));
}
}
if potential_assoc_types.len() == assoc_items.len() {
// When the amount of missing associated types equals the number of
// extra type arguments present. A suggesting to replace the generic args with
// associated types is already emitted.
already_has_generics_args_suggestion = true;
} else if let (Ok(snippet), false) =
(tcx.sess.source_map().span_to_snippet(*span), dupes)
{
let types: Vec<_> =
assoc_items.iter().map(|item| format!("{} = Type", item.name)).collect();
let code = if snippet.ends_with('>') {
// The user wrote `Trait<'a>` or similar and we don't have a type we can
// suggest, but at least we can clue them to the correct syntax
// `Trait<'a, Item = Type>` while accounting for the `<'a>` in the
// suggestion.
format!("{}, {}>", &snippet[..snippet.len() - 1], types.join(", "))
} else {
// The user wrote `Iterator`, so we don't have a type we can suggest, but at
// least we can clue them to the correct syntax `Iterator<Item = Type>`.
format!("{}<{}>", snippet, types.join(", "))
};
suggestions.push((*span, code));
} else if dupes {
where_constraints.push(*span);
}
}
let where_msg = "consider introducing a new type parameter, adding `where` constraints \
using the fully-qualified path to the associated types";
if !where_constraints.is_empty() && suggestions.is_empty() {
// If there are duplicates associated type names and a single trait bound do not
// use structured suggestion, it means that there are multiple supertraits with
// the same associated type name.
err.help(where_msg);
}
if suggestions.len() != 1 || already_has_generics_args_suggestion {
// We don't need this label if there's an inline suggestion, show otherwise.
for (span, assoc_items) in &associated_types {
let mut names: FxHashMap<_, usize> = FxHashMap::default();
for item in assoc_items {
types_count += 1;
*names.entry(item.name).or_insert(0) += 1;
}
let mut label = vec![];
for item in assoc_items {
let postfix = if names[&item.name] > 1 {
let trait_def_id = item.container_id(tcx);
format!(" (from trait `{}`)", tcx.def_path_str(trait_def_id))
} else {
String::new()
};
label.push(format!("`{}`{}", item.name, postfix));
}
if !label.is_empty() {
err.span_label(
*span,
format!(
"associated type{} {} must be specified",
pluralize!(label.len()),
label.join(", "),
),
);
}
}
}
suggestions.sort_by_key(|&(span, _)| span);
// There are cases where one bound points to a span within another bound's span, like when
// you have code like the following (#115019), so we skip providing a suggestion in those
// cases to avoid having a malformed suggestion.
//
// pub struct Flatten<I> {
// inner: <IntoIterator<Item: IntoIterator<Item: >>::IntoIterator as Item>::core,
// ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
// | ^^^^^^^^^^^^^^^^^^^^^
// | |
// | associated types `Item`, `IntoIter` must be specified
// associated types `Item`, `IntoIter` must be specified
// }
let overlaps = suggestions.windows(2).any(|pair| pair[0].0.overlaps(pair[1].0));
if !suggestions.is_empty() && !overlaps {
err.multipart_suggestion(
format!("specify the associated type{}", pluralize!(types_count)),
suggestions,
Applicability::HasPlaceholders,
);
if !where_constraints.is_empty() {
err.span_help(where_constraints, where_msg);
}
}
err.emit();
}
}
/// Emits an error regarding forbidden type binding associations
pub fn prohibit_assoc_ty_binding(
tcx: TyCtxt<'_>,
span: Span,
segment: Option<(&hir::PathSegment<'_>, Span)>,
) {
tcx.sess.emit_err(AssocTypeBindingNotAllowed {
span,
fn_trait_expansion: if let Some((segment, span)) = segment
&& segment.args().parenthesized == hir::GenericArgsParentheses::ParenSugar
{
Some(ParenthesizedFnTraitExpansion {
span,
expanded_type: fn_trait_to_string(tcx, segment, false),
})
} else {
None
},
});
}
pub(crate) fn fn_trait_to_string(
tcx: TyCtxt<'_>,
trait_segment: &hir::PathSegment<'_>,
parenthesized: bool,
) -> String {
let args = trait_segment
.args
.as_ref()
.and_then(|args| args.args.get(0))
.and_then(|arg| match arg {
hir::GenericArg::Type(ty) => match ty.kind {
hir::TyKind::Tup(t) => t
.iter()
.map(|e| tcx.sess.source_map().span_to_snippet(e.span))
.collect::<Result<Vec<_>, _>>()
.map(|a| a.join(", ")),
_ => tcx.sess.source_map().span_to_snippet(ty.span),
}
.map(|s| {
// `s.empty()` checks to see if the type is the unit tuple, if so we don't want a comma
if parenthesized || s.is_empty() { format!("({s})") } else { format!("({s},)") }
})
.ok(),
_ => None,
})
.unwrap_or_else(|| "()".to_string());
let ret = trait_segment
.args()
.bindings
.iter()
.find_map(|b| match (b.ident.name == sym::Output, &b.kind) {
(true, hir::TypeBindingKind::Equality { term }) => {
let span = match term {
hir::Term::Ty(ty) => ty.span,
hir::Term::Const(c) => tcx.hir().span(c.hir_id),
};
(span != tcx.hir().span(trait_segment.hir_id))
.then_some(tcx.sess.source_map().span_to_snippet(span).ok())
.flatten()
}
_ => None,
})
.unwrap_or_else(|| "()".to_string());
if parenthesized {
format!("{}{} -> {}", trait_segment.ident, args, ret)
} else {
format!("{}<{}, Output={}>", trait_segment.ident, args, ret)
}
}