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::{self, Ty, TyCtxt, UserType};
116 use rustc_middle::ty::{InternalSubsts, SubstsRef};
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::compare_method::collect_trait_impl_trait_tys;
136 use self::region::region_scope_tree;
137 pub use self::Expectation::*;
140 macro_rules! type_error_struct {
141 ($session:expr, $span:expr, $typ:expr, $code:ident, $($message:tt)*) => ({
142 let mut err = rustc_errors::struct_span_err!($session, $span, $code, $($message)*);
144 if $typ.references_error() {
145 err.downgrade_to_delayed_bug();
152 /// The type of a local binding, including the revealed type for anon types.
153 #[derive(Copy, Clone, Debug)]
154 pub struct LocalTy<'tcx> {
156 revealed_ty: Ty<'tcx>,
159 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
166 fn maybe_mut_place(m: hir::Mutability) -> Self {
168 hir::Mutability::Mut => Needs::MutPlace,
169 hir::Mutability::Not => Needs::None,
174 #[derive(Copy, Clone)]
175 pub struct UnsafetyState {
177 pub unsafety: hir::Unsafety,
182 pub fn function(unsafety: hir::Unsafety, def: hir::HirId) -> UnsafetyState {
183 UnsafetyState { def, unsafety, from_fn: true }
186 pub fn recurse(self, blk: &hir::Block<'_>) -> UnsafetyState {
187 use hir::BlockCheckMode;
188 match self.unsafety {
189 // If this unsafe, then if the outer function was already marked as
190 // unsafe we shouldn't attribute the unsafe'ness to the block. This
191 // way the block can be warned about instead of ignoring this
192 // extraneous block (functions are never warned about).
193 hir::Unsafety::Unsafe if self.from_fn => self,
196 let (unsafety, def) = match blk.rules {
197 BlockCheckMode::UnsafeBlock(..) => (hir::Unsafety::Unsafe, blk.hir_id),
198 BlockCheckMode::DefaultBlock => (unsafety, self.def),
200 UnsafetyState { def, unsafety, from_fn: false }
206 #[derive(Debug, Copy, Clone)]
212 pub struct BreakableCtxt<'tcx> {
215 // this is `null` for loops where break with a value is illegal,
216 // such as `while`, `for`, and `while let`
217 coerce: Option<DynamicCoerceMany<'tcx>>,
220 pub struct EnclosingBreakables<'tcx> {
221 stack: Vec<BreakableCtxt<'tcx>>,
222 by_id: HirIdMap<usize>,
225 impl<'tcx> EnclosingBreakables<'tcx> {
226 fn find_breakable(&mut self, target_id: hir::HirId) -> &mut BreakableCtxt<'tcx> {
227 self.opt_find_breakable(target_id).unwrap_or_else(|| {
228 bug!("could not find enclosing breakable with id {}", target_id);
232 fn opt_find_breakable(&mut self, target_id: hir::HirId) -> Option<&mut BreakableCtxt<'tcx>> {
233 match self.by_id.get(&target_id) {
234 Some(ix) => Some(&mut self.stack[*ix]),
240 pub fn provide(providers: &mut Providers) {
241 method::provide(providers);
242 wfcheck::provide(providers);
243 *providers = Providers {
247 diagnostic_only_typeck,
251 check_mod_item_types,
253 collect_trait_impl_trait_tys,
258 fn adt_destructor(tcx: TyCtxt<'_>, def_id: DefId) -> Option<ty::Destructor> {
259 tcx.calculate_dtor(def_id, dropck::check_drop_impl)
262 /// If this `DefId` is a "primary tables entry", returns
263 /// `Some((body_id, body_ty, fn_sig))`. Otherwise, returns `None`.
265 /// If this function returns `Some`, then `typeck_results(def_id)` will
266 /// succeed; if it returns `None`, then `typeck_results(def_id)` may or
267 /// may not succeed. In some cases where this function returns `None`
268 /// (notably closures), `typeck_results(def_id)` would wind up
269 /// redirecting to the owning function.
273 ) -> Option<(hir::BodyId, Option<&hir::Ty<'_>>, Option<&hir::FnSig<'_>>)> {
274 match tcx.hir().get(id) {
275 Node::Item(item) => match item.kind {
276 hir::ItemKind::Const(ty, body) | hir::ItemKind::Static(ty, _, body) => {
277 Some((body, Some(ty), None))
279 hir::ItemKind::Fn(ref sig, .., body) => Some((body, None, Some(sig))),
282 Node::TraitItem(item) => match item.kind {
283 hir::TraitItemKind::Const(ty, Some(body)) => Some((body, Some(ty), None)),
284 hir::TraitItemKind::Fn(ref sig, hir::TraitFn::Provided(body)) => {
285 Some((body, None, Some(sig)))
289 Node::ImplItem(item) => match item.kind {
290 hir::ImplItemKind::Const(ty, body) => Some((body, Some(ty), None)),
291 hir::ImplItemKind::Fn(ref sig, body) => Some((body, None, Some(sig))),
294 Node::AnonConst(constant) => Some((constant.body, None, None)),
299 fn has_typeck_results(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
300 // Closures' typeck results come from their outermost function,
301 // as they are part of the same "inference environment".
302 let typeck_root_def_id = tcx.typeck_root_def_id(def_id);
303 if typeck_root_def_id != def_id {
304 return tcx.has_typeck_results(typeck_root_def_id);
307 if let Some(def_id) = def_id.as_local() {
308 let id = tcx.hir().local_def_id_to_hir_id(def_id);
309 primary_body_of(tcx, id).is_some()
315 fn used_trait_imports(tcx: TyCtxt<'_>, def_id: LocalDefId) -> &FxHashSet<LocalDefId> {
316 &*tcx.typeck(def_id).used_trait_imports
319 fn typeck_const_arg<'tcx>(
321 (did, param_did): (LocalDefId, DefId),
322 ) -> &ty::TypeckResults<'tcx> {
323 let fallback = move || tcx.type_of(param_did);
324 typeck_with_fallback(tcx, did, fallback)
327 fn typeck<'tcx>(tcx: TyCtxt<'tcx>, def_id: LocalDefId) -> &ty::TypeckResults<'tcx> {
328 if let Some(param_did) = tcx.opt_const_param_of(def_id) {
329 tcx.typeck_const_arg((def_id, param_did))
331 let fallback = move || tcx.type_of(def_id.to_def_id());
332 typeck_with_fallback(tcx, def_id, fallback)
336 /// Used only to get `TypeckResults` for type inference during error recovery.
337 /// Currently only used for type inference of `static`s and `const`s to avoid type cycle errors.
338 fn diagnostic_only_typeck<'tcx>(tcx: TyCtxt<'tcx>, def_id: LocalDefId) -> &ty::TypeckResults<'tcx> {
339 let fallback = move || {
340 let span = tcx.hir().span(tcx.hir().local_def_id_to_hir_id(def_id));
341 tcx.ty_error_with_message(span, "diagnostic only typeck table used")
343 typeck_with_fallback(tcx, def_id, fallback)
346 fn typeck_with_fallback<'tcx>(
349 fallback: impl Fn() -> Ty<'tcx> + 'tcx,
350 ) -> &'tcx ty::TypeckResults<'tcx> {
351 // Closures' typeck results come from their outermost function,
352 // as they are part of the same "inference environment".
353 let typeck_root_def_id = tcx.typeck_root_def_id(def_id.to_def_id()).expect_local();
354 if typeck_root_def_id != def_id {
355 return tcx.typeck(typeck_root_def_id);
358 let id = tcx.hir().local_def_id_to_hir_id(def_id);
359 let span = tcx.hir().span(id);
361 // Figure out what primary body this item has.
362 let (body_id, body_ty, fn_sig) = primary_body_of(tcx, id).unwrap_or_else(|| {
363 span_bug!(span, "can't type-check body of {:?}", def_id);
365 let body = tcx.hir().body(body_id);
367 let typeck_results = Inherited::build(tcx, def_id).enter(|inh| {
368 let param_env = tcx.param_env(def_id);
369 let fcx = if let Some(hir::FnSig { header, decl, .. }) = fn_sig {
370 let fn_sig = if crate::collect::get_infer_ret_ty(&decl.output).is_some() {
371 let fcx = FnCtxt::new(&inh, param_env, body.value.hir_id);
372 <dyn AstConv<'_>>::ty_of_fn(&fcx, id, header.unsafety, header.abi, decl, None, None)
377 check_abi(tcx, id, span, fn_sig.abi());
379 // Compute the function signature from point of view of inside the fn.
380 let fn_sig = tcx.liberate_late_bound_regions(def_id.to_def_id(), fn_sig);
381 let fn_sig = inh.normalize_associated_types_in(
387 check_fn(&inh, param_env, fn_sig, decl, id, body, None, true).0
389 let fcx = FnCtxt::new(&inh, param_env, body.value.hir_id);
390 let expected_type = body_ty
391 .and_then(|ty| match ty.kind {
392 hir::TyKind::Infer => Some(<dyn AstConv<'_>>::ast_ty_to_ty(&fcx, ty)),
395 .unwrap_or_else(|| match tcx.hir().get(id) {
396 Node::AnonConst(_) => match tcx.hir().get(tcx.hir().get_parent_node(id)) {
397 Node::Expr(&hir::Expr {
398 kind: hir::ExprKind::ConstBlock(ref anon_const),
400 }) if anon_const.hir_id == id => fcx.next_ty_var(TypeVariableOrigin {
401 kind: TypeVariableOriginKind::TypeInference,
405 kind: hir::TyKind::Typeof(ref anon_const), ..
406 }) if anon_const.hir_id == id => fcx.next_ty_var(TypeVariableOrigin {
407 kind: TypeVariableOriginKind::TypeInference,
410 Node::Expr(&hir::Expr { kind: hir::ExprKind::InlineAsm(asm), .. })
411 | Node::Item(&hir::Item { kind: hir::ItemKind::GlobalAsm(asm), .. }) => {
415 .filter_map(|(op, _op_sp)| match op {
416 hir::InlineAsmOperand::Const { anon_const }
417 if anon_const.hir_id == id =>
419 // Inline assembly constants must be integers.
420 Some(fcx.next_int_var())
422 hir::InlineAsmOperand::SymFn { anon_const }
423 if anon_const.hir_id == id =>
425 Some(fcx.next_ty_var(TypeVariableOrigin {
426 kind: TypeVariableOriginKind::MiscVariable,
433 operand_ty.unwrap_or_else(fallback)
440 let expected_type = fcx.normalize_associated_types_in(body.value.span, expected_type);
441 fcx.require_type_is_sized(expected_type, body.value.span, traits::ConstSized);
443 // Gather locals in statics (because of block expressions).
444 GatherLocalsVisitor::new(&fcx).visit_body(body);
446 fcx.check_expr_coercable_to_type(&body.value, expected_type, None);
448 fcx.write_ty(id, expected_type);
453 let fallback_has_occurred = fcx.type_inference_fallback();
455 // Even though coercion casts provide type hints, we check casts after fallback for
456 // backwards compatibility. This makes fallback a stronger type hint than a cast coercion.
458 fcx.select_obligations_where_possible(fallback_has_occurred, |_| {});
460 // Closure and generator analysis may run after fallback
461 // because they don't constrain other type variables.
462 fcx.closure_analyze(body);
463 assert!(fcx.deferred_call_resolutions.borrow().is_empty());
464 // Before the generator analysis, temporary scopes shall be marked to provide more
465 // precise information on types to be captured.
466 fcx.resolve_rvalue_scopes(def_id.to_def_id());
467 fcx.resolve_generator_interiors(def_id.to_def_id());
469 for (ty, span, code) in fcx.deferred_sized_obligations.borrow_mut().drain(..) {
470 let ty = fcx.normalize_ty(span, ty);
471 fcx.require_type_is_sized(ty, span, code);
474 fcx.select_all_obligations_or_error();
476 if !fcx.infcx.is_tainted_by_errors() {
477 fcx.check_transmutes();
482 fcx.infcx.skip_region_resolution();
484 fcx.resolve_type_vars_in_body(body)
487 // Consistency check our TypeckResults instance can hold all ItemLocalIds
488 // it will need to hold.
489 assert_eq!(typeck_results.hir_owner, id.owner);
494 /// When `check_fn` is invoked on a generator (i.e., a body that
495 /// includes yield), it returns back some information about the yield
497 struct GeneratorTypes<'tcx> {
498 /// Type of generator argument / values returned by `yield`.
501 /// Type of value that is yielded.
504 /// Types that are captured (see `GeneratorInterior` for more).
507 /// Indicates if the generator is movable or static (immovable).
508 movability: hir::Movability,
511 /// Given a `DefId` for an opaque type in return position, find its parent item's return
513 fn get_owner_return_paths<'tcx>(
516 ) -> Option<(LocalDefId, ReturnsVisitor<'tcx>)> {
517 let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
518 let parent_id = tcx.hir().get_parent_item(hir_id);
519 tcx.hir().find_by_def_id(parent_id).and_then(|node| node.body_id()).map(|body_id| {
520 let body = tcx.hir().body(body_id);
521 let mut visitor = ReturnsVisitor::default();
522 visitor.visit_body(body);
527 // Forbid defining intrinsics in Rust code,
528 // as they must always be defined by the compiler.
529 fn fn_maybe_err(tcx: TyCtxt<'_>, sp: Span, abi: Abi) {
530 if let Abi::RustIntrinsic | Abi::PlatformIntrinsic = abi {
531 tcx.sess.span_err(sp, "intrinsic must be in `extern \"rust-intrinsic\" { ... }` block");
535 fn maybe_check_static_with_link_section(tcx: TyCtxt<'_>, id: LocalDefId) {
536 // Only restricted on wasm target for now
537 if !tcx.sess.target.is_like_wasm {
541 // If `#[link_section]` is missing, then nothing to verify
542 let attrs = tcx.codegen_fn_attrs(id);
543 if attrs.link_section.is_none() {
547 // For the wasm32 target statics with `#[link_section]` are placed into custom
548 // sections of the final output file, but this isn't link custom sections of
549 // other executable formats. Namely we can only embed a list of bytes,
550 // nothing with provenance (pointers to anything else). If any provenance
551 // show up, reject it here.
552 // `#[link_section]` may contain arbitrary, or even undefined bytes, but it is
553 // the consumer's responsibility to ensure all bytes that have been read
554 // have defined values.
555 if let Ok(alloc) = tcx.eval_static_initializer(id.to_def_id())
556 && alloc.inner().provenance().len() != 0
558 let msg = "statics with a custom `#[link_section]` must be a \
559 simple list of bytes on the wasm target with no \
560 extra levels of indirection such as references";
561 tcx.sess.span_err(tcx.def_span(id), msg);
565 fn report_forbidden_specialization(
567 impl_item: &hir::ImplItemRef,
570 let mut err = struct_span_err!(
574 "`{}` specializes an item from a parent `impl`, but \
575 that item is not marked `default`",
578 err.span_label(impl_item.span, format!("cannot specialize default item `{}`", impl_item.ident));
580 match tcx.span_of_impl(parent_impl) {
582 err.span_label(span, "parent `impl` is here");
584 "to specialize, `{}` in the parent `impl` must be marked `default`",
589 err.note(&format!("parent implementation is in crate `{cname}`"));
596 fn missing_items_err(
599 missing_items: &[&ty::AssocItem],
600 full_impl_span: Span,
602 let missing_items_msg = missing_items
604 .map(|trait_item| trait_item.name.to_string())
608 let mut err = struct_span_err!(
612 "not all trait items implemented, missing: `{missing_items_msg}`",
614 err.span_label(impl_span, format!("missing `{missing_items_msg}` in implementation"));
616 // `Span` before impl block closing brace.
617 let hi = full_impl_span.hi() - BytePos(1);
618 // Point at the place right before the closing brace of the relevant `impl` to suggest
619 // adding the associated item at the end of its body.
620 let sugg_sp = full_impl_span.with_lo(hi).with_hi(hi);
621 // Obtain the level of indentation ending in `sugg_sp`.
623 tcx.sess.source_map().indentation_before(sugg_sp).unwrap_or_else(|| String::new());
625 for trait_item in missing_items {
626 let snippet = suggestion_signature(trait_item, tcx);
627 let code = format!("{}{}\n{}", padding, snippet, padding);
628 let msg = format!("implement the missing item: `{snippet}`");
629 let appl = Applicability::HasPlaceholders;
630 if let Some(span) = tcx.hir().span_if_local(trait_item.def_id) {
631 err.span_label(span, format!("`{}` from trait", trait_item.name));
632 err.tool_only_span_suggestion(sugg_sp, &msg, code, appl);
634 err.span_suggestion_hidden(sugg_sp, &msg, code, appl);
640 fn missing_items_must_implement_one_of_err(
643 missing_items: &[Ident],
644 annotation_span: Option<Span>,
646 let missing_items_msg =
647 missing_items.iter().map(Ident::to_string).collect::<Vec<_>>().join("`, `");
649 let mut err = struct_span_err!(
653 "not all trait items implemented, missing one of: `{missing_items_msg}`",
655 err.span_label(impl_span, format!("missing one of `{missing_items_msg}` in implementation"));
657 if let Some(annotation_span) = annotation_span {
658 err.span_note(annotation_span, "required because of this annotation");
664 fn default_body_is_unstable(
669 reason: Option<Symbol>,
670 issue: Option<NonZeroU32>,
672 let missing_item_name = &tcx.associated_item(item_did).name;
673 let use_of_unstable_library_feature_note = match reason {
674 Some(r) => format!("use of unstable library feature '{feature}': {r}"),
675 None => format!("use of unstable library feature '{feature}'"),
678 let mut err = struct_span_err!(
682 "not all trait items implemented, missing: `{missing_item_name}`",
684 err.note(format!("default implementation of `{missing_item_name}` is unstable"));
685 err.note(use_of_unstable_library_feature_note);
686 rustc_session::parse::add_feature_diagnostics_for_issue(
688 &tcx.sess.parse_sess,
690 rustc_feature::GateIssue::Library(issue),
695 /// Re-sugar `ty::GenericPredicates` in a way suitable to be used in structured suggestions.
696 fn bounds_from_generic_predicates<'tcx>(
698 predicates: ty::GenericPredicates<'tcx>,
699 ) -> (String, String) {
700 let mut types: FxHashMap<Ty<'tcx>, Vec<DefId>> = FxHashMap::default();
701 let mut projections = vec![];
702 for (predicate, _) in predicates.predicates {
703 debug!("predicate {:?}", predicate);
704 let bound_predicate = predicate.kind();
705 match bound_predicate.skip_binder() {
706 ty::PredicateKind::Trait(trait_predicate) => {
707 let entry = types.entry(trait_predicate.self_ty()).or_default();
708 let def_id = trait_predicate.def_id();
709 if Some(def_id) != tcx.lang_items().sized_trait() {
710 // Type params are `Sized` by default, do not add that restriction to the list
711 // if it is a positive requirement.
712 entry.push(trait_predicate.def_id());
715 ty::PredicateKind::Projection(projection_pred) => {
716 projections.push(bound_predicate.rebind(projection_pred));
721 let generics = if types.is_empty() {
728 .filter_map(|t| match t.kind() {
729 ty::Param(_) => Some(t.to_string()),
730 // Avoid suggesting the following:
731 // fn foo<T, <T as Trait>::Bar>(_: T) where T: Trait, <T as Trait>::Bar: Other {}
738 let mut where_clauses = vec![];
739 for (ty, bounds) in types {
741 .extend(bounds.into_iter().map(|bound| format!("{}: {}", ty, tcx.def_path_str(bound))));
743 for projection in &projections {
744 let p = projection.skip_binder();
745 // FIXME: this is not currently supported syntax, we should be looking at the `types` and
746 // insert the associated types where they correspond, but for now let's be "lazy" and
747 // propose this instead of the following valid resugaring:
748 // `T: Trait, Trait::Assoc = K` → `T: Trait<Assoc = K>`
749 where_clauses.push(format!(
751 tcx.def_path_str(p.projection_ty.item_def_id),
755 let where_clauses = if where_clauses.is_empty() {
758 format!(" where {}", where_clauses.join(", "))
760 (generics, where_clauses)
763 /// Return placeholder code for the given function.
764 fn fn_sig_suggestion<'tcx>(
766 sig: ty::FnSig<'tcx>,
768 predicates: ty::GenericPredicates<'tcx>,
769 assoc: &ty::AssocItem,
776 Some(match ty.kind() {
777 ty::Param(_) if assoc.fn_has_self_parameter && i == 0 => "self".to_string(),
778 ty::Ref(reg, ref_ty, mutability) if i == 0 => {
779 let reg = format!("{reg} ");
780 let reg = match ®[..] {
784 if assoc.fn_has_self_parameter {
785 match ref_ty.kind() {
786 ty::Param(param) if param.name == kw::SelfUpper => {
787 format!("&{}{}self", reg, mutability.prefix_str())
790 _ => format!("self: {ty}"),
797 if assoc.fn_has_self_parameter && i == 0 {
798 format!("self: {ty}")
805 .chain(std::iter::once(if sig.c_variadic { Some("...".to_string()) } else { None }))
807 .collect::<Vec<String>>()
809 let output = sig.output();
810 let output = if !output.is_unit() { format!(" -> {output}") } else { String::new() };
812 let unsafety = sig.unsafety.prefix_str();
813 let (generics, where_clauses) = bounds_from_generic_predicates(tcx, predicates);
815 // FIXME: this is not entirely correct, as the lifetimes from borrowed params will
816 // not be present in the `fn` definition, not will we account for renamed
817 // lifetimes between the `impl` and the `trait`, but this should be good enough to
818 // fill in a significant portion of the missing code, and other subsequent
819 // suggestions can help the user fix the code.
820 format!("{unsafety}fn {ident}{generics}({args}){output}{where_clauses} {{ todo!() }}")
823 /// Return placeholder code for the given associated item.
824 /// Similar to `ty::AssocItem::suggestion`, but appropriate for use as the code snippet of a
825 /// structured suggestion.
826 fn suggestion_signature(assoc: &ty::AssocItem, tcx: TyCtxt<'_>) -> String {
828 ty::AssocKind::Fn => {
829 // We skip the binder here because the binder would deanonymize all
830 // late-bound regions, and we don't want method signatures to show up
831 // `as for<'r> fn(&'r MyType)`. Pretty-printing handles late-bound
832 // regions just fine, showing `fn(&MyType)`.
835 tcx.fn_sig(assoc.def_id).skip_binder(),
837 tcx.predicates_of(assoc.def_id),
841 ty::AssocKind::Type => format!("type {} = Type;", assoc.name),
842 ty::AssocKind::Const => {
843 let ty = tcx.type_of(assoc.def_id);
844 let val = expr::ty_kind_suggestion(ty).unwrap_or("value");
845 format!("const {}: {} = {};", assoc.name, ty, val)
850 /// Emit an error when encountering two or more variants in a transparent enum.
851 fn bad_variant_count<'tcx>(tcx: TyCtxt<'tcx>, adt: ty::AdtDef<'tcx>, sp: Span, did: DefId) {
852 let variant_spans: Vec<_> = adt
855 .map(|variant| tcx.hir().span_if_local(variant.def_id).unwrap())
857 let msg = format!("needs exactly one variant, but has {}", adt.variants().len(),);
858 let mut err = struct_span_err!(tcx.sess, sp, E0731, "transparent enum {msg}");
859 err.span_label(sp, &msg);
860 if let [start @ .., end] = &*variant_spans {
861 for variant_span in start {
862 err.span_label(*variant_span, "");
864 err.span_label(*end, &format!("too many variants in `{}`", tcx.def_path_str(did)));
869 /// Emit an error when encountering two or more non-zero-sized fields in a transparent
871 fn bad_non_zero_sized_fields<'tcx>(
873 adt: ty::AdtDef<'tcx>,
875 field_spans: impl Iterator<Item = Span>,
878 let msg = format!("needs at most one non-zero-sized field, but has {field_count}");
879 let mut err = struct_span_err!(
883 "{}transparent {} {}",
884 if adt.is_enum() { "the variant of a " } else { "" },
888 err.span_label(sp, &msg);
889 for sp in field_spans {
890 err.span_label(sp, "this field is non-zero-sized");
895 fn report_unexpected_variant_res(tcx: TyCtxt<'_>, res: Res, qpath: &hir::QPath<'_>, span: Span) {
900 "expected unit struct, unit variant or constant, found {} `{}`",
902 rustc_hir_pretty::qpath_to_string(qpath),
907 /// Controls whether the arguments are tupled. This is used for the call
910 /// Tupling means that all call-side arguments are packed into a tuple and
911 /// passed as a single parameter. For example, if tupling is enabled, this
914 /// fn f(x: (isize, isize)) {}
916 /// Can be called as:
917 /// ```ignore UNSOLVED (can this be done in user code?)
918 /// # fn f(x: (isize, isize)) {}
923 /// # fn f(x: (isize, isize)) {}
926 #[derive(Clone, Eq, PartialEq)]
927 enum TupleArgumentsFlag {
932 fn typeck_item_bodies(tcx: TyCtxt<'_>, (): ()) {
933 tcx.hir().par_body_owners(|body_owner_def_id| tcx.ensure().typeck(body_owner_def_id));
936 fn fatally_break_rust(sess: &Session) {
937 let handler = sess.diagnostic();
938 handler.span_bug_no_panic(
940 "It looks like you're trying to break rust; would you like some ICE?",
942 handler.note_without_error("the compiler expectedly panicked. this is a feature.");
943 handler.note_without_error(
944 "we would appreciate a joke overview: \
945 https://github.com/rust-lang/rust/issues/43162#issuecomment-320764675",
947 handler.note_without_error(&format!(
948 "rustc {} running on {}",
949 option_env!("CFG_VERSION").unwrap_or("unknown_version"),
950 config::host_triple(),
954 fn potentially_plural_count(count: usize, word: &str) -> String {
955 format!("{} {}{}", count, word, pluralize!(count))
958 fn has_expected_num_generic_args<'tcx>(
960 trait_did: Option<DefId>,
963 trait_did.map_or(true, |trait_did| {
964 let generics = tcx.generics_of(trait_did);
965 generics.count() == expected + if generics.has_self { 1 } else { 0 }