5 Within the check phase of type check, we check each item one at a time
6 (bodies of function expressions are checked as part of the containing
7 function). Inference is used to supply types wherever they are unknown.
9 By far the most complex case is checking the body of a function. This
10 can be broken down into several distinct phases:
12 - gather: creates type variables to represent the type of each local
13 variable and pattern binding.
15 - main: the main pass does the lion's share of the work: it
16 determines the types of all expressions, resolves
17 methods, checks for most invalid conditions, and so forth. In
18 some cases, where a type is unknown, it may create a type or region
19 variable and use that as the type of an expression.
21 In the process of checking, various constraints will be placed on
22 these type variables through the subtyping relationships requested
23 through the `demand` module. The `infer` module is in charge
24 of resolving those constraints.
26 - regionck: after main is complete, the regionck pass goes over all
27 types looking for regions and making sure that they did not escape
28 into places where they are not in scope. This may also influence the
29 final assignments of the various region variables if there is some
32 - writeback: writes the final types within a function body, replacing
33 type variables with their final inferred types. These final types
34 are written into the `tcx.node_types` table, which should *never* contain
35 any reference to a type variable.
39 While type checking a function, the intermediate types for the
40 expressions, blocks, and so forth contained within the function are
41 stored in `fcx.node_types` and `fcx.node_substs`. These types
42 may contain unresolved type variables. After type checking is
43 complete, the functions in the writeback module are used to take the
44 types from this table, resolve them, and then write them into their
45 permanent home in the type context `tcx`.
47 This means that during inferencing you should use `fcx.write_ty()`
48 and `fcx.expr_ty()` / `fcx.node_ty()` to write/obtain the types of
49 nodes within the function.
51 The types of top-level items, which never contain unbound type
52 variables, are stored directly into the `tcx` typeck_results.
54 N.B., a type variable is not the same thing as a type parameter. A
55 type variable is an instance of a type parameter. That is,
56 given a generic function `fn foo<T>(t: T)`, while checking the
57 function `foo`, the type `ty_param(0)` refers to the type `T`, which
58 is treated in abstract. However, when `foo()` is called, `T` will be
59 substituted for a fresh type variable `N`. This variable will
60 eventually be resolved to some concrete type (which might itself be
81 mod generator_interior;
90 pub mod rvalue_scopes;
95 use check::{check_abi, check_fn, check_mod_item_types};
96 pub use diverges::Diverges;
97 pub use expectation::Expectation;
99 pub use inherited::{Inherited, InheritedBuilder};
101 use crate::astconv::AstConv;
102 use crate::check::gather_locals::GatherLocalsVisitor;
103 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
105 pluralize, struct_span_err, Applicability, Diagnostic, DiagnosticBuilder, MultiSpan,
107 use rustc_hir as hir;
108 use rustc_hir::def::Res;
109 use rustc_hir::def_id::{DefId, LocalDefId};
110 use rustc_hir::intravisit::Visitor;
111 use rustc_hir::{HirIdMap, ImplicitSelfKind, Node};
112 use rustc_index::bit_set::BitSet;
113 use rustc_infer::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
114 use rustc_middle::ty::query::Providers;
115 use rustc_middle::ty::subst::{InternalSubsts, Subst, SubstsRef};
116 use rustc_middle::ty::{self, Ty, TyCtxt, UserType};
117 use rustc_session::config;
118 use rustc_session::parse::feature_err;
119 use rustc_session::Session;
120 use rustc_span::source_map::DUMMY_SP;
121 use rustc_span::symbol::{kw, Ident};
122 use rustc_span::{self, BytePos, Span, Symbol};
123 use rustc_target::abi::VariantIdx;
124 use rustc_target::spec::abi::Abi;
125 use rustc_trait_selection::traits;
126 use rustc_trait_selection::traits::error_reporting::recursive_type_with_infinite_size_error;
127 use rustc_trait_selection::traits::error_reporting::suggestions::ReturnsVisitor;
128 use std::cell::RefCell;
129 use std::num::NonZeroU32;
131 use crate::require_c_abi_if_c_variadic;
132 use crate::util::common::indenter;
134 use self::coercion::DynamicCoerceMany;
135 use self::region::region_scope_tree;
136 pub use self::Expectation::*;
139 macro_rules! type_error_struct {
140 ($session:expr, $span:expr, $typ:expr, $code:ident, $($message:tt)*) => ({
141 let mut err = rustc_errors::struct_span_err!($session, $span, $code, $($message)*);
143 if $typ.references_error() {
144 err.downgrade_to_delayed_bug();
151 /// The type of a local binding, including the revealed type for anon types.
152 #[derive(Copy, Clone, Debug)]
153 pub struct LocalTy<'tcx> {
155 revealed_ty: Ty<'tcx>,
158 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
165 fn maybe_mut_place(m: hir::Mutability) -> Self {
167 hir::Mutability::Mut => Needs::MutPlace,
168 hir::Mutability::Not => Needs::None,
173 #[derive(Copy, Clone)]
174 pub struct UnsafetyState {
176 pub unsafety: hir::Unsafety,
181 pub fn function(unsafety: hir::Unsafety, def: hir::HirId) -> UnsafetyState {
182 UnsafetyState { def, unsafety, from_fn: true }
185 pub fn recurse(self, blk: &hir::Block<'_>) -> UnsafetyState {
186 use hir::BlockCheckMode;
187 match self.unsafety {
188 // If this unsafe, then if the outer function was already marked as
189 // unsafe we shouldn't attribute the unsafe'ness to the block. This
190 // way the block can be warned about instead of ignoring this
191 // extraneous block (functions are never warned about).
192 hir::Unsafety::Unsafe if self.from_fn => self,
195 let (unsafety, def) = match blk.rules {
196 BlockCheckMode::UnsafeBlock(..) => (hir::Unsafety::Unsafe, blk.hir_id),
197 BlockCheckMode::DefaultBlock => (unsafety, self.def),
199 UnsafetyState { def, unsafety, from_fn: false }
205 #[derive(Debug, Copy, Clone)]
211 pub struct BreakableCtxt<'tcx> {
214 // this is `null` for loops where break with a value is illegal,
215 // such as `while`, `for`, and `while let`
216 coerce: Option<DynamicCoerceMany<'tcx>>,
219 pub struct EnclosingBreakables<'tcx> {
220 stack: Vec<BreakableCtxt<'tcx>>,
221 by_id: HirIdMap<usize>,
224 impl<'tcx> EnclosingBreakables<'tcx> {
225 fn find_breakable(&mut self, target_id: hir::HirId) -> &mut BreakableCtxt<'tcx> {
226 self.opt_find_breakable(target_id).unwrap_or_else(|| {
227 bug!("could not find enclosing breakable with id {}", target_id);
231 fn opt_find_breakable(&mut self, target_id: hir::HirId) -> Option<&mut BreakableCtxt<'tcx>> {
232 match self.by_id.get(&target_id) {
233 Some(ix) => Some(&mut self.stack[*ix]),
239 pub fn provide(providers: &mut Providers) {
240 method::provide(providers);
241 wfcheck::provide(providers);
242 *providers = Providers {
246 diagnostic_only_typeck,
250 check_mod_item_types,
256 fn adt_destructor(tcx: TyCtxt<'_>, def_id: DefId) -> Option<ty::Destructor> {
257 tcx.calculate_dtor(def_id, dropck::check_drop_impl)
260 /// If this `DefId` is a "primary tables entry", returns
261 /// `Some((body_id, body_ty, fn_sig))`. Otherwise, returns `None`.
263 /// If this function returns `Some`, then `typeck_results(def_id)` will
264 /// succeed; if it returns `None`, then `typeck_results(def_id)` may or
265 /// may not succeed. In some cases where this function returns `None`
266 /// (notably closures), `typeck_results(def_id)` would wind up
267 /// redirecting to the owning function.
271 ) -> Option<(hir::BodyId, Option<&hir::Ty<'_>>, Option<&hir::FnSig<'_>>)> {
272 match tcx.hir().get(id) {
273 Node::Item(item) => match item.kind {
274 hir::ItemKind::Const(ty, body) | hir::ItemKind::Static(ty, _, body) => {
275 Some((body, Some(ty), None))
277 hir::ItemKind::Fn(ref sig, .., body) => Some((body, None, Some(sig))),
280 Node::TraitItem(item) => match item.kind {
281 hir::TraitItemKind::Const(ty, Some(body)) => Some((body, Some(ty), None)),
282 hir::TraitItemKind::Fn(ref sig, hir::TraitFn::Provided(body)) => {
283 Some((body, None, Some(sig)))
287 Node::ImplItem(item) => match item.kind {
288 hir::ImplItemKind::Const(ty, body) => Some((body, Some(ty), None)),
289 hir::ImplItemKind::Fn(ref sig, body) => Some((body, None, Some(sig))),
292 Node::AnonConst(constant) => Some((constant.body, None, None)),
297 fn has_typeck_results(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
298 // Closures' typeck results come from their outermost function,
299 // as they are part of the same "inference environment".
300 let typeck_root_def_id = tcx.typeck_root_def_id(def_id);
301 if typeck_root_def_id != def_id {
302 return tcx.has_typeck_results(typeck_root_def_id);
305 if let Some(def_id) = def_id.as_local() {
306 let id = tcx.hir().local_def_id_to_hir_id(def_id);
307 primary_body_of(tcx, id).is_some()
313 fn used_trait_imports(tcx: TyCtxt<'_>, def_id: LocalDefId) -> &FxHashSet<LocalDefId> {
314 &*tcx.typeck(def_id).used_trait_imports
317 fn typeck_const_arg<'tcx>(
319 (did, param_did): (LocalDefId, DefId),
320 ) -> &ty::TypeckResults<'tcx> {
321 let fallback = move || tcx.type_of(param_did);
322 typeck_with_fallback(tcx, did, fallback)
325 fn typeck<'tcx>(tcx: TyCtxt<'tcx>, def_id: LocalDefId) -> &ty::TypeckResults<'tcx> {
326 if let Some(param_did) = tcx.opt_const_param_of(def_id) {
327 tcx.typeck_const_arg((def_id, param_did))
329 let fallback = move || tcx.type_of(def_id.to_def_id());
330 typeck_with_fallback(tcx, def_id, fallback)
334 /// Used only to get `TypeckResults` for type inference during error recovery.
335 /// Currently only used for type inference of `static`s and `const`s to avoid type cycle errors.
336 fn diagnostic_only_typeck<'tcx>(tcx: TyCtxt<'tcx>, def_id: LocalDefId) -> &ty::TypeckResults<'tcx> {
337 let fallback = move || {
338 let span = tcx.hir().span(tcx.hir().local_def_id_to_hir_id(def_id));
339 tcx.ty_error_with_message(span, "diagnostic only typeck table used")
341 typeck_with_fallback(tcx, def_id, fallback)
344 fn typeck_with_fallback<'tcx>(
347 fallback: impl Fn() -> Ty<'tcx> + 'tcx,
348 ) -> &'tcx ty::TypeckResults<'tcx> {
349 // Closures' typeck results come from their outermost function,
350 // as they are part of the same "inference environment".
351 let typeck_root_def_id = tcx.typeck_root_def_id(def_id.to_def_id()).expect_local();
352 if typeck_root_def_id != def_id {
353 return tcx.typeck(typeck_root_def_id);
356 let id = tcx.hir().local_def_id_to_hir_id(def_id);
357 let span = tcx.hir().span(id);
359 // Figure out what primary body this item has.
360 let (body_id, body_ty, fn_sig) = primary_body_of(tcx, id).unwrap_or_else(|| {
361 span_bug!(span, "can't type-check body of {:?}", def_id);
363 let body = tcx.hir().body(body_id);
365 let typeck_results = Inherited::build(tcx, def_id).enter(|inh| {
366 let param_env = tcx.param_env(def_id);
367 let fcx = if let Some(hir::FnSig { header, decl, .. }) = fn_sig {
368 let fn_sig = if crate::collect::get_infer_ret_ty(&decl.output).is_some() {
369 let fcx = FnCtxt::new(&inh, param_env, body.value.hir_id);
370 <dyn AstConv<'_>>::ty_of_fn(&fcx, id, header.unsafety, header.abi, decl, None, None)
375 check_abi(tcx, id, span, fn_sig.abi());
377 // Compute the function signature from point of view of inside the fn.
378 let fn_sig = tcx.liberate_late_bound_regions(def_id.to_def_id(), fn_sig);
379 let fn_sig = inh.normalize_associated_types_in(
385 check_fn(&inh, param_env, fn_sig, decl, id, body, None, true).0
387 let fcx = FnCtxt::new(&inh, param_env, body.value.hir_id);
388 let expected_type = body_ty
389 .and_then(|ty| match ty.kind {
390 hir::TyKind::Infer => Some(<dyn AstConv<'_>>::ast_ty_to_ty(&fcx, ty)),
393 .unwrap_or_else(|| match tcx.hir().get(id) {
394 Node::AnonConst(_) => match tcx.hir().get(tcx.hir().get_parent_node(id)) {
395 Node::Expr(&hir::Expr {
396 kind: hir::ExprKind::ConstBlock(ref anon_const),
398 }) if anon_const.hir_id == id => fcx.next_ty_var(TypeVariableOrigin {
399 kind: TypeVariableOriginKind::TypeInference,
403 kind: hir::TyKind::Typeof(ref anon_const), ..
404 }) if anon_const.hir_id == id => fcx.next_ty_var(TypeVariableOrigin {
405 kind: TypeVariableOriginKind::TypeInference,
408 Node::Expr(&hir::Expr { kind: hir::ExprKind::InlineAsm(asm), .. })
409 | Node::Item(&hir::Item { kind: hir::ItemKind::GlobalAsm(asm), .. }) => {
413 .filter_map(|(op, _op_sp)| match op {
414 hir::InlineAsmOperand::Const { anon_const }
415 if anon_const.hir_id == id =>
417 // Inline assembly constants must be integers.
418 Some(fcx.next_int_var())
420 hir::InlineAsmOperand::SymFn { anon_const }
421 if anon_const.hir_id == id =>
423 Some(fcx.next_ty_var(TypeVariableOrigin {
424 kind: TypeVariableOriginKind::MiscVariable,
431 operand_ty.unwrap_or_else(fallback)
438 let expected_type = fcx.normalize_associated_types_in(body.value.span, expected_type);
439 fcx.require_type_is_sized(expected_type, body.value.span, traits::ConstSized);
441 // Gather locals in statics (because of block expressions).
442 GatherLocalsVisitor::new(&fcx).visit_body(body);
444 fcx.check_expr_coercable_to_type(&body.value, expected_type, None);
446 fcx.write_ty(id, expected_type);
451 let fallback_has_occurred = fcx.type_inference_fallback();
453 // Even though coercion casts provide type hints, we check casts after fallback for
454 // backwards compatibility. This makes fallback a stronger type hint than a cast coercion.
456 fcx.select_obligations_where_possible(fallback_has_occurred, |_| {});
458 // Closure and generator analysis may run after fallback
459 // because they don't constrain other type variables.
460 fcx.closure_analyze(body);
461 assert!(fcx.deferred_call_resolutions.borrow().is_empty());
462 // Before the generator analysis, temporary scopes shall be marked to provide more
463 // precise information on types to be captured.
464 fcx.resolve_rvalue_scopes(def_id.to_def_id());
465 fcx.resolve_generator_interiors(def_id.to_def_id());
467 fcx.select_all_obligations_or_error();
469 if !fcx.infcx.is_tainted_by_errors() {
470 fcx.check_transmutes();
475 fcx.infcx.skip_region_resolution();
477 fcx.resolve_type_vars_in_body(body)
480 // Consistency check our TypeckResults instance can hold all ItemLocalIds
481 // it will need to hold.
482 assert_eq!(typeck_results.hir_owner, id.owner);
487 /// When `check_fn` is invoked on a generator (i.e., a body that
488 /// includes yield), it returns back some information about the yield
490 struct GeneratorTypes<'tcx> {
491 /// Type of generator argument / values returned by `yield`.
494 /// Type of value that is yielded.
497 /// Types that are captured (see `GeneratorInterior` for more).
500 /// Indicates if the generator is movable or static (immovable).
501 movability: hir::Movability,
504 /// Given a `DefId` for an opaque type in return position, find its parent item's return
506 fn get_owner_return_paths<'tcx>(
509 ) -> Option<(LocalDefId, ReturnsVisitor<'tcx>)> {
510 let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
511 let parent_id = tcx.hir().get_parent_item(hir_id);
512 tcx.hir().find_by_def_id(parent_id).and_then(|node| node.body_id()).map(|body_id| {
513 let body = tcx.hir().body(body_id);
514 let mut visitor = ReturnsVisitor::default();
515 visitor.visit_body(body);
520 // Forbid defining intrinsics in Rust code,
521 // as they must always be defined by the compiler.
522 fn fn_maybe_err(tcx: TyCtxt<'_>, sp: Span, abi: Abi) {
523 if let Abi::RustIntrinsic | Abi::PlatformIntrinsic = abi {
524 tcx.sess.span_err(sp, "intrinsic must be in `extern \"rust-intrinsic\" { ... }` block");
528 fn maybe_check_static_with_link_section(tcx: TyCtxt<'_>, id: LocalDefId) {
529 // Only restricted on wasm target for now
530 if !tcx.sess.target.is_like_wasm {
534 // If `#[link_section]` is missing, then nothing to verify
535 let attrs = tcx.codegen_fn_attrs(id);
536 if attrs.link_section.is_none() {
540 // For the wasm32 target statics with `#[link_section]` are placed into custom
541 // sections of the final output file, but this isn't link custom sections of
542 // other executable formats. Namely we can only embed a list of bytes,
543 // nothing with provenance (pointers to anything else). If any provenance
544 // show up, reject it here.
545 // `#[link_section]` may contain arbitrary, or even undefined bytes, but it is
546 // the consumer's responsibility to ensure all bytes that have been read
547 // have defined values.
548 if let Ok(alloc) = tcx.eval_static_initializer(id.to_def_id())
549 && alloc.inner().provenance().len() != 0
551 let msg = "statics with a custom `#[link_section]` must be a \
552 simple list of bytes on the wasm target with no \
553 extra levels of indirection such as references";
554 tcx.sess.span_err(tcx.def_span(id), msg);
558 fn report_forbidden_specialization(
560 impl_item: &hir::ImplItemRef,
563 let mut err = struct_span_err!(
567 "`{}` specializes an item from a parent `impl`, but \
568 that item is not marked `default`",
571 err.span_label(impl_item.span, format!("cannot specialize default item `{}`", impl_item.ident));
573 match tcx.span_of_impl(parent_impl) {
575 err.span_label(span, "parent `impl` is here");
577 "to specialize, `{}` in the parent `impl` must be marked `default`",
582 err.note(&format!("parent implementation is in crate `{cname}`"));
589 fn missing_items_err(
592 missing_items: &[&ty::AssocItem],
593 full_impl_span: Span,
595 let missing_items_msg = missing_items
597 .map(|trait_item| trait_item.name.to_string())
601 let mut err = struct_span_err!(
605 "not all trait items implemented, missing: `{missing_items_msg}`",
607 err.span_label(impl_span, format!("missing `{missing_items_msg}` in implementation"));
609 // `Span` before impl block closing brace.
610 let hi = full_impl_span.hi() - BytePos(1);
611 // Point at the place right before the closing brace of the relevant `impl` to suggest
612 // adding the associated item at the end of its body.
613 let sugg_sp = full_impl_span.with_lo(hi).with_hi(hi);
614 // Obtain the level of indentation ending in `sugg_sp`.
616 tcx.sess.source_map().indentation_before(sugg_sp).unwrap_or_else(|| String::new());
618 for trait_item in missing_items {
619 let snippet = suggestion_signature(trait_item, tcx);
620 let code = format!("{}{}\n{}", padding, snippet, padding);
621 let msg = format!("implement the missing item: `{snippet}`");
622 let appl = Applicability::HasPlaceholders;
623 if let Some(span) = tcx.hir().span_if_local(trait_item.def_id) {
624 err.span_label(span, format!("`{}` from trait", trait_item.name));
625 err.tool_only_span_suggestion(sugg_sp, &msg, code, appl);
627 err.span_suggestion_hidden(sugg_sp, &msg, code, appl);
633 fn missing_items_must_implement_one_of_err(
636 missing_items: &[Ident],
637 annotation_span: Option<Span>,
639 let missing_items_msg =
640 missing_items.iter().map(Ident::to_string).collect::<Vec<_>>().join("`, `");
642 let mut err = struct_span_err!(
646 "not all trait items implemented, missing one of: `{missing_items_msg}`",
648 err.span_label(impl_span, format!("missing one of `{missing_items_msg}` in implementation"));
650 if let Some(annotation_span) = annotation_span {
651 err.span_note(annotation_span, "required because of this annotation");
657 fn default_body_is_unstable(
662 reason: Option<Symbol>,
663 issue: Option<NonZeroU32>,
665 let missing_item_name = &tcx.associated_item(item_did).name;
666 let use_of_unstable_library_feature_note = match reason {
667 Some(r) => format!("use of unstable library feature '{feature}': {r}"),
668 None => format!("use of unstable library feature '{feature}'"),
671 let mut err = struct_span_err!(
675 "not all trait items implemented, missing: `{missing_item_name}`",
677 err.note(format!("default implementation of `{missing_item_name}` is unstable"));
678 err.note(use_of_unstable_library_feature_note);
679 rustc_session::parse::add_feature_diagnostics_for_issue(
681 &tcx.sess.parse_sess,
683 rustc_feature::GateIssue::Library(issue),
688 /// Re-sugar `ty::GenericPredicates` in a way suitable to be used in structured suggestions.
689 fn bounds_from_generic_predicates<'tcx>(
691 predicates: ty::GenericPredicates<'tcx>,
692 ) -> (String, String) {
693 let mut types: FxHashMap<Ty<'tcx>, Vec<DefId>> = FxHashMap::default();
694 let mut projections = vec![];
695 for (predicate, _) in predicates.predicates {
696 debug!("predicate {:?}", predicate);
697 let bound_predicate = predicate.kind();
698 match bound_predicate.skip_binder() {
699 ty::PredicateKind::Trait(trait_predicate) => {
700 let entry = types.entry(trait_predicate.self_ty()).or_default();
701 let def_id = trait_predicate.def_id();
702 if Some(def_id) != tcx.lang_items().sized_trait() {
703 // Type params are `Sized` by default, do not add that restriction to the list
704 // if it is a positive requirement.
705 entry.push(trait_predicate.def_id());
708 ty::PredicateKind::Projection(projection_pred) => {
709 projections.push(bound_predicate.rebind(projection_pred));
714 let generics = if types.is_empty() {
721 .filter_map(|t| match t.kind() {
722 ty::Param(_) => Some(t.to_string()),
723 // Avoid suggesting the following:
724 // fn foo<T, <T as Trait>::Bar>(_: T) where T: Trait, <T as Trait>::Bar: Other {}
731 let mut where_clauses = vec![];
732 for (ty, bounds) in types {
734 .extend(bounds.into_iter().map(|bound| format!("{}: {}", ty, tcx.def_path_str(bound))));
736 for projection in &projections {
737 let p = projection.skip_binder();
738 // FIXME: this is not currently supported syntax, we should be looking at the `types` and
739 // insert the associated types where they correspond, but for now let's be "lazy" and
740 // propose this instead of the following valid resugaring:
741 // `T: Trait, Trait::Assoc = K` → `T: Trait<Assoc = K>`
742 where_clauses.push(format!(
744 tcx.def_path_str(p.projection_ty.item_def_id),
748 let where_clauses = if where_clauses.is_empty() {
751 format!(" where {}", where_clauses.join(", "))
753 (generics, where_clauses)
756 /// Return placeholder code for the given function.
757 fn fn_sig_suggestion<'tcx>(
759 sig: ty::FnSig<'tcx>,
761 predicates: ty::GenericPredicates<'tcx>,
762 assoc: &ty::AssocItem,
769 Some(match ty.kind() {
770 ty::Param(_) if assoc.fn_has_self_parameter && i == 0 => "self".to_string(),
771 ty::Ref(reg, ref_ty, mutability) if i == 0 => {
772 let reg = format!("{reg} ");
773 let reg = match ®[..] {
777 if assoc.fn_has_self_parameter {
778 match ref_ty.kind() {
779 ty::Param(param) if param.name == kw::SelfUpper => {
780 format!("&{}{}self", reg, mutability.prefix_str())
783 _ => format!("self: {ty}"),
790 if assoc.fn_has_self_parameter && i == 0 {
791 format!("self: {ty}")
798 .chain(std::iter::once(if sig.c_variadic { Some("...".to_string()) } else { None }))
800 .collect::<Vec<String>>()
802 let output = sig.output();
803 let output = if !output.is_unit() { format!(" -> {output}") } else { String::new() };
805 let unsafety = sig.unsafety.prefix_str();
806 let (generics, where_clauses) = bounds_from_generic_predicates(tcx, predicates);
808 // FIXME: this is not entirely correct, as the lifetimes from borrowed params will
809 // not be present in the `fn` definition, not will we account for renamed
810 // lifetimes between the `impl` and the `trait`, but this should be good enough to
811 // fill in a significant portion of the missing code, and other subsequent
812 // suggestions can help the user fix the code.
813 format!("{unsafety}fn {ident}{generics}({args}){output}{where_clauses} {{ todo!() }}")
816 /// Return placeholder code for the given associated item.
817 /// Similar to `ty::AssocItem::suggestion`, but appropriate for use as the code snippet of a
818 /// structured suggestion.
819 fn suggestion_signature(assoc: &ty::AssocItem, tcx: TyCtxt<'_>) -> String {
821 ty::AssocKind::Fn => {
822 // We skip the binder here because the binder would deanonymize all
823 // late-bound regions, and we don't want method signatures to show up
824 // `as for<'r> fn(&'r MyType)`. Pretty-printing handles late-bound
825 // regions just fine, showing `fn(&MyType)`.
828 tcx.fn_sig(assoc.def_id).skip_binder(),
830 tcx.predicates_of(assoc.def_id),
834 ty::AssocKind::Type => format!("type {} = Type;", assoc.name),
835 ty::AssocKind::Const => {
836 let ty = tcx.type_of(assoc.def_id);
837 let val = expr::ty_kind_suggestion(ty).unwrap_or("value");
838 format!("const {}: {} = {};", assoc.name, ty, val)
843 /// Emit an error when encountering two or more variants in a transparent enum.
844 fn bad_variant_count<'tcx>(tcx: TyCtxt<'tcx>, adt: ty::AdtDef<'tcx>, sp: Span, did: DefId) {
845 let variant_spans: Vec<_> = adt
848 .map(|variant| tcx.hir().span_if_local(variant.def_id).unwrap())
850 let msg = format!("needs exactly one variant, but has {}", adt.variants().len(),);
851 let mut err = struct_span_err!(tcx.sess, sp, E0731, "transparent enum {msg}");
852 err.span_label(sp, &msg);
853 if let [start @ .., end] = &*variant_spans {
854 for variant_span in start {
855 err.span_label(*variant_span, "");
857 err.span_label(*end, &format!("too many variants in `{}`", tcx.def_path_str(did)));
862 /// Emit an error when encountering two or more non-zero-sized fields in a transparent
864 fn bad_non_zero_sized_fields<'tcx>(
866 adt: ty::AdtDef<'tcx>,
868 field_spans: impl Iterator<Item = Span>,
871 let msg = format!("needs at most one non-zero-sized field, but has {field_count}");
872 let mut err = struct_span_err!(
876 "{}transparent {} {}",
877 if adt.is_enum() { "the variant of a " } else { "" },
881 err.span_label(sp, &msg);
882 for sp in field_spans {
883 err.span_label(sp, "this field is non-zero-sized");
888 fn report_unexpected_variant_res(tcx: TyCtxt<'_>, res: Res, qpath: &hir::QPath<'_>, span: Span) {
893 "expected unit struct, unit variant or constant, found {} `{}`",
895 rustc_hir_pretty::qpath_to_string(qpath),
900 /// Controls whether the arguments are tupled. This is used for the call
903 /// Tupling means that all call-side arguments are packed into a tuple and
904 /// passed as a single parameter. For example, if tupling is enabled, this
907 /// fn f(x: (isize, isize)) {}
909 /// Can be called as:
910 /// ```ignore UNSOLVED (can this be done in user code?)
911 /// # fn f(x: (isize, isize)) {}
916 /// # fn f(x: (isize, isize)) {}
919 #[derive(Clone, Eq, PartialEq)]
920 enum TupleArgumentsFlag {
925 fn typeck_item_bodies(tcx: TyCtxt<'_>, (): ()) {
926 tcx.hir().par_body_owners(|body_owner_def_id| tcx.ensure().typeck(body_owner_def_id));
929 fn fatally_break_rust(sess: &Session) {
930 let handler = sess.diagnostic();
931 handler.span_bug_no_panic(
933 "It looks like you're trying to break rust; would you like some ICE?",
935 handler.note_without_error("the compiler expectedly panicked. this is a feature.");
936 handler.note_without_error(
937 "we would appreciate a joke overview: \
938 https://github.com/rust-lang/rust/issues/43162#issuecomment-320764675",
940 handler.note_without_error(&format!(
941 "rustc {} running on {}",
942 option_env!("CFG_VERSION").unwrap_or("unknown_version"),
943 config::host_triple(),
947 fn potentially_plural_count(count: usize, word: &str) -> String {
948 format!("{} {}{}", count, word, pluralize!(count))
951 fn has_expected_num_generic_args<'tcx>(
953 trait_did: Option<DefId>,
956 trait_did.map_or(true, |trait_did| {
957 let generics = tcx.generics_of(trait_did);
958 generics.count() == expected + if generics.has_self { 1 } else { 0 }