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;
91 pub mod rvalue_scopes;
96 use check::{check_abi, check_fn, check_mod_item_types};
97 pub use diverges::Diverges;
98 pub use expectation::Expectation;
100 use hir::def::CtorOf;
101 pub use inherited::{Inherited, InheritedBuilder};
103 use crate::astconv::AstConv;
104 use crate::check::gather_locals::GatherLocalsVisitor;
105 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
107 pluralize, struct_span_err, Applicability, DiagnosticBuilder, EmissionGuarantee, MultiSpan,
109 use rustc_hir as hir;
110 use rustc_hir::def::Res;
111 use rustc_hir::def_id::{DefId, LocalDefId};
112 use rustc_hir::intravisit::Visitor;
113 use rustc_hir::{HirIdMap, ImplicitSelfKind, Node};
114 use rustc_index::bit_set::BitSet;
115 use rustc_index::vec::Idx;
116 use rustc_infer::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
117 use rustc_middle::ty::query::Providers;
118 use rustc_middle::ty::subst::{InternalSubsts, Subst, SubstsRef};
119 use rustc_middle::ty::{self, Ty, TyCtxt, UserType};
120 use rustc_session::config;
121 use rustc_session::parse::feature_err;
122 use rustc_session::Session;
123 use rustc_span::source_map::DUMMY_SP;
124 use rustc_span::symbol::{kw, Ident};
125 use rustc_span::{self, BytePos, Span};
126 use rustc_target::abi::VariantIdx;
127 use rustc_target::spec::abi::Abi;
128 use rustc_trait_selection::traits;
129 use rustc_trait_selection::traits::error_reporting::recursive_type_with_infinite_size_error;
130 use rustc_trait_selection::traits::error_reporting::suggestions::ReturnsVisitor;
132 use std::cell::{Ref, RefCell, RefMut};
134 use crate::require_c_abi_if_c_variadic;
135 use crate::util::common::indenter;
137 use self::coercion::DynamicCoerceMany;
138 use self::region::region_scope_tree;
139 pub use self::Expectation::*;
142 macro_rules! type_error_struct {
143 ($session:expr, $span:expr, $typ:expr, $code:ident, $($message:tt)*) => ({
144 let mut err = rustc_errors::struct_span_err!($session, $span, $code, $($message)*);
146 if $typ.references_error() {
147 err.downgrade_to_delayed_bug();
154 /// The type of a local binding, including the revealed type for anon types.
155 #[derive(Copy, Clone, Debug)]
156 pub struct LocalTy<'tcx> {
158 revealed_ty: Ty<'tcx>,
161 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
168 fn maybe_mut_place(m: hir::Mutability) -> Self {
170 hir::Mutability::Mut => Needs::MutPlace,
171 hir::Mutability::Not => Needs::None,
176 #[derive(Copy, Clone)]
177 pub struct UnsafetyState {
179 pub unsafety: hir::Unsafety,
184 pub fn function(unsafety: hir::Unsafety, def: hir::HirId) -> UnsafetyState {
185 UnsafetyState { def, unsafety, from_fn: true }
188 pub fn recurse(self, blk: &hir::Block<'_>) -> UnsafetyState {
189 use hir::BlockCheckMode;
190 match self.unsafety {
191 // If this unsafe, then if the outer function was already marked as
192 // unsafe we shouldn't attribute the unsafe'ness to the block. This
193 // way the block can be warned about instead of ignoring this
194 // extraneous block (functions are never warned about).
195 hir::Unsafety::Unsafe if self.from_fn => self,
198 let (unsafety, def) = match blk.rules {
199 BlockCheckMode::UnsafeBlock(..) => (hir::Unsafety::Unsafe, blk.hir_id),
200 BlockCheckMode::DefaultBlock => (unsafety, self.def),
202 UnsafetyState { def, unsafety, from_fn: false }
208 #[derive(Debug, Copy, Clone)]
214 pub struct BreakableCtxt<'tcx> {
217 // this is `null` for loops where break with a value is illegal,
218 // such as `while`, `for`, and `while let`
219 coerce: Option<DynamicCoerceMany<'tcx>>,
222 pub struct EnclosingBreakables<'tcx> {
223 stack: Vec<BreakableCtxt<'tcx>>,
224 by_id: HirIdMap<usize>,
227 impl<'tcx> EnclosingBreakables<'tcx> {
228 fn find_breakable(&mut self, target_id: hir::HirId) -> &mut BreakableCtxt<'tcx> {
229 self.opt_find_breakable(target_id).unwrap_or_else(|| {
230 bug!("could not find enclosing breakable with id {}", target_id);
234 fn opt_find_breakable(&mut self, target_id: hir::HirId) -> Option<&mut BreakableCtxt<'tcx>> {
235 match self.by_id.get(&target_id) {
236 Some(ix) => Some(&mut self.stack[*ix]),
242 pub fn provide(providers: &mut Providers) {
243 method::provide(providers);
244 wfcheck::provide(providers);
245 *providers = Providers {
249 diagnostic_only_typeck,
253 check_mod_item_types,
259 fn adt_destructor(tcx: TyCtxt<'_>, def_id: DefId) -> Option<ty::Destructor> {
260 tcx.calculate_dtor(def_id, dropck::check_drop_impl)
263 /// If this `DefId` is a "primary tables entry", returns
264 /// `Some((body_id, body_ty, fn_sig))`. Otherwise, returns `None`.
266 /// If this function returns `Some`, then `typeck_results(def_id)` will
267 /// succeed; if it returns `None`, then `typeck_results(def_id)` may or
268 /// may not succeed. In some cases where this function returns `None`
269 /// (notably closures), `typeck_results(def_id)` would wind up
270 /// redirecting to the owning function.
274 ) -> Option<(hir::BodyId, Option<&hir::Ty<'_>>, Option<&hir::FnSig<'_>>)> {
275 match tcx.hir().get(id) {
276 Node::Item(item) => match item.kind {
277 hir::ItemKind::Const(ty, body) | hir::ItemKind::Static(ty, _, body) => {
278 Some((body, Some(ty), None))
280 hir::ItemKind::Fn(ref sig, .., body) => Some((body, None, Some(sig))),
283 Node::TraitItem(item) => match item.kind {
284 hir::TraitItemKind::Const(ty, Some(body)) => Some((body, Some(ty), None)),
285 hir::TraitItemKind::Fn(ref sig, hir::TraitFn::Provided(body)) => {
286 Some((body, None, Some(sig)))
290 Node::ImplItem(item) => match item.kind {
291 hir::ImplItemKind::Const(ty, body) => Some((body, Some(ty), None)),
292 hir::ImplItemKind::Fn(ref sig, body) => Some((body, None, Some(sig))),
295 Node::AnonConst(constant) => Some((constant.body, None, None)),
300 fn has_typeck_results(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
301 // Closures' typeck results come from their outermost function,
302 // as they are part of the same "inference environment".
303 let typeck_root_def_id = tcx.typeck_root_def_id(def_id);
304 if typeck_root_def_id != def_id {
305 return tcx.has_typeck_results(typeck_root_def_id);
308 if let Some(def_id) = def_id.as_local() {
309 let id = tcx.hir().local_def_id_to_hir_id(def_id);
310 primary_body_of(tcx, id).is_some()
316 fn used_trait_imports(tcx: TyCtxt<'_>, def_id: LocalDefId) -> &FxHashSet<LocalDefId> {
317 &*tcx.typeck(def_id).used_trait_imports
320 fn typeck_const_arg<'tcx>(
322 (did, param_did): (LocalDefId, DefId),
323 ) -> &ty::TypeckResults<'tcx> {
324 let fallback = move || tcx.type_of(param_did);
325 typeck_with_fallback(tcx, did, fallback)
328 fn typeck<'tcx>(tcx: TyCtxt<'tcx>, def_id: LocalDefId) -> &ty::TypeckResults<'tcx> {
329 if let Some(param_did) = tcx.opt_const_param_of(def_id) {
330 tcx.typeck_const_arg((def_id, param_did))
332 let fallback = move || tcx.type_of(def_id.to_def_id());
333 typeck_with_fallback(tcx, def_id, fallback)
337 /// Used only to get `TypeckResults` for type inference during error recovery.
338 /// Currently only used for type inference of `static`s and `const`s to avoid type cycle errors.
339 fn diagnostic_only_typeck<'tcx>(tcx: TyCtxt<'tcx>, def_id: LocalDefId) -> &ty::TypeckResults<'tcx> {
340 let fallback = move || {
341 let span = tcx.hir().span(tcx.hir().local_def_id_to_hir_id(def_id));
342 tcx.ty_error_with_message(span, "diagnostic only typeck table used")
344 typeck_with_fallback(tcx, def_id, fallback)
347 #[instrument(skip(tcx, fallback))]
348 fn typeck_with_fallback<'tcx>(
351 fallback: impl Fn() -> Ty<'tcx> + 'tcx,
352 ) -> &'tcx ty::TypeckResults<'tcx> {
353 // Closures' typeck results come from their outermost function,
354 // as they are part of the same "inference environment".
355 let typeck_root_def_id = tcx.typeck_root_def_id(def_id.to_def_id()).expect_local();
356 if typeck_root_def_id != def_id {
357 return tcx.typeck(typeck_root_def_id);
360 let id = tcx.hir().local_def_id_to_hir_id(def_id);
361 let span = tcx.hir().span(id);
363 // Figure out what primary body this item has.
364 let (body_id, body_ty, fn_sig) = primary_body_of(tcx, id).unwrap_or_else(|| {
365 span_bug!(span, "can't type-check body of {:?}", def_id);
367 let body = tcx.hir().body(body_id);
369 let typeck_results = Inherited::build(tcx, def_id).enter(|inh| {
370 let param_env = tcx.param_env(def_id);
371 let fcx = if let Some(hir::FnSig { header, decl, .. }) = fn_sig {
372 let fn_sig = if crate::collect::get_infer_ret_ty(&decl.output).is_some() {
373 let fcx = FnCtxt::new(&inh, param_env, body.value.hir_id);
374 <dyn AstConv<'_>>::ty_of_fn(&fcx, id, header.unsafety, header.abi, decl, None, None)
379 check_abi(tcx, id, span, fn_sig.abi());
381 // Compute the function signature from point of view of inside the fn.
382 let fn_sig = tcx.liberate_late_bound_regions(def_id.to_def_id(), fn_sig);
383 let fn_sig = inh.normalize_associated_types_in(
389 check_fn(&inh, param_env, fn_sig, decl, id, body, None, true).0
391 let fcx = FnCtxt::new(&inh, param_env, body.value.hir_id);
392 let expected_type = body_ty
393 .and_then(|ty| match ty.kind {
394 hir::TyKind::Infer => Some(<dyn AstConv<'_>>::ast_ty_to_ty(&fcx, ty)),
397 .unwrap_or_else(|| match tcx.hir().get(id) {
398 Node::AnonConst(_) => match tcx.hir().get(tcx.hir().get_parent_node(id)) {
399 Node::Expr(&hir::Expr {
400 kind: hir::ExprKind::ConstBlock(ref anon_const),
402 }) if anon_const.hir_id == id => fcx.next_ty_var(TypeVariableOrigin {
403 kind: TypeVariableOriginKind::TypeInference,
407 kind: hir::TyKind::Typeof(ref anon_const), ..
408 }) if anon_const.hir_id == id => fcx.next_ty_var(TypeVariableOrigin {
409 kind: TypeVariableOriginKind::TypeInference,
412 Node::Expr(&hir::Expr { kind: hir::ExprKind::InlineAsm(asm), .. })
413 | Node::Item(&hir::Item { kind: hir::ItemKind::GlobalAsm(asm), .. }) => {
417 .filter_map(|(op, _op_sp)| match op {
418 hir::InlineAsmOperand::Const { anon_const }
419 if anon_const.hir_id == id =>
421 // Inline assembly constants must be integers.
422 Some(fcx.next_int_var())
424 hir::InlineAsmOperand::SymFn { anon_const }
425 if anon_const.hir_id == id =>
427 Some(fcx.next_ty_var(TypeVariableOrigin {
428 kind: TypeVariableOriginKind::MiscVariable,
435 operand_ty.unwrap_or_else(fallback)
442 let expected_type = fcx.normalize_associated_types_in(body.value.span, expected_type);
443 fcx.require_type_is_sized(expected_type, body.value.span, traits::ConstSized);
445 // Gather locals in statics (because of block expressions).
446 GatherLocalsVisitor::new(&fcx).visit_body(body);
448 fcx.check_expr_coercable_to_type(&body.value, expected_type, None);
450 fcx.write_ty(id, expected_type);
455 let fallback_has_occurred = fcx.type_inference_fallback();
457 // Even though coercion casts provide type hints, we check casts after fallback for
458 // backwards compatibility. This makes fallback a stronger type hint than a cast coercion.
460 fcx.select_obligations_where_possible(fallback_has_occurred, |_| {});
462 // Closure and generator analysis may run after fallback
463 // because they don't constrain other type variables.
464 fcx.closure_analyze(body);
465 assert!(fcx.deferred_call_resolutions.borrow().is_empty());
466 // Before the generator analysis, temporary scopes shall be marked to provide more
467 // precise information on types to be captured.
468 fcx.resolve_rvalue_scopes(def_id.to_def_id());
469 fcx.resolve_generator_interiors(def_id.to_def_id());
471 for (ty, span, code) in fcx.deferred_sized_obligations.borrow_mut().drain(..) {
472 let ty = fcx.normalize_ty(span, ty);
473 fcx.require_type_is_sized(ty, span, code);
476 fcx.select_all_obligations_or_error();
478 if !fcx.infcx.is_tainted_by_errors() {
479 fcx.check_transmutes();
484 fcx.infcx.skip_region_resolution();
486 fcx.resolve_type_vars_in_body(body)
489 // Consistency check our TypeckResults instance can hold all ItemLocalIds
490 // it will need to hold.
491 assert_eq!(typeck_results.hir_owner, id.owner);
496 /// When `check_fn` is invoked on a generator (i.e., a body that
497 /// includes yield), it returns back some information about the yield
499 struct GeneratorTypes<'tcx> {
500 /// Type of generator argument / values returned by `yield`.
503 /// Type of value that is yielded.
506 /// Types that are captured (see `GeneratorInterior` for more).
509 /// Indicates if the generator is movable or static (immovable).
510 movability: hir::Movability,
513 /// Given a `DefId` for an opaque type in return position, find its parent item's return
515 fn get_owner_return_paths<'tcx>(
518 ) -> Option<(LocalDefId, ReturnsVisitor<'tcx>)> {
519 let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
520 let parent_id = tcx.hir().get_parent_item(hir_id);
521 tcx.hir().find_by_def_id(parent_id).and_then(|node| node.body_id()).map(|body_id| {
522 let body = tcx.hir().body(body_id);
523 let mut visitor = ReturnsVisitor::default();
524 visitor.visit_body(body);
529 // Forbid defining intrinsics in Rust code,
530 // as they must always be defined by the compiler.
531 fn fn_maybe_err(tcx: TyCtxt<'_>, sp: Span, abi: Abi) {
532 if let Abi::RustIntrinsic | Abi::PlatformIntrinsic = abi {
533 tcx.sess.span_err(sp, "intrinsic must be in `extern \"rust-intrinsic\" { ... }` block");
537 fn maybe_check_static_with_link_section(tcx: TyCtxt<'_>, id: LocalDefId) {
538 // Only restricted on wasm target for now
539 if !tcx.sess.target.is_like_wasm {
543 // If `#[link_section]` is missing, then nothing to verify
544 let attrs = tcx.codegen_fn_attrs(id);
545 if attrs.link_section.is_none() {
549 // For the wasm32 target statics with `#[link_section]` are placed into custom
550 // sections of the final output file, but this isn't link custom sections of
551 // other executable formats. Namely we can only embed a list of bytes,
552 // nothing with pointers to anything else or relocations. If any relocation
553 // show up, reject them here.
554 // `#[link_section]` may contain arbitrary, or even undefined bytes, but it is
555 // the consumer's responsibility to ensure all bytes that have been read
556 // have defined values.
557 if let Ok(alloc) = tcx.eval_static_initializer(id.to_def_id())
558 && alloc.inner().relocations().len() != 0
560 let msg = "statics with a custom `#[link_section]` must be a \
561 simple list of bytes on the wasm target with no \
562 extra levels of indirection such as references";
563 tcx.sess.span_err(tcx.def_span(id), msg);
567 fn report_forbidden_specialization(
569 impl_item: &hir::ImplItemRef,
572 let mut err = struct_span_err!(
576 "`{}` specializes an item from a parent `impl`, but \
577 that item is not marked `default`",
580 err.span_label(impl_item.span, format!("cannot specialize default item `{}`", impl_item.ident));
582 match tcx.span_of_impl(parent_impl) {
584 err.span_label(span, "parent `impl` is here");
586 "to specialize, `{}` in the parent `impl` must be marked `default`",
591 err.note(&format!("parent implementation is in crate `{cname}`"));
598 fn missing_items_err(
601 missing_items: &[&ty::AssocItem],
602 full_impl_span: Span,
604 let missing_items_msg = missing_items
606 .map(|trait_item| trait_item.name.to_string())
610 let mut err = struct_span_err!(
614 "not all trait items implemented, missing: `{missing_items_msg}`",
616 err.span_label(impl_span, format!("missing `{missing_items_msg}` in implementation"));
618 // `Span` before impl block closing brace.
619 let hi = full_impl_span.hi() - BytePos(1);
620 // Point at the place right before the closing brace of the relevant `impl` to suggest
621 // adding the associated item at the end of its body.
622 let sugg_sp = full_impl_span.with_lo(hi).with_hi(hi);
623 // Obtain the level of indentation ending in `sugg_sp`.
625 tcx.sess.source_map().indentation_before(sugg_sp).unwrap_or_else(|| String::new());
627 for trait_item in missing_items {
628 let snippet = suggestion_signature(trait_item, tcx);
629 let code = format!("{}{}\n{}", padding, snippet, padding);
630 let msg = format!("implement the missing item: `{snippet}`");
631 let appl = Applicability::HasPlaceholders;
632 if let Some(span) = tcx.hir().span_if_local(trait_item.def_id) {
633 err.span_label(span, format!("`{}` from trait", trait_item.name));
634 err.tool_only_span_suggestion(sugg_sp, &msg, code, appl);
636 err.span_suggestion_hidden(sugg_sp, &msg, code, appl);
642 fn missing_items_must_implement_one_of_err(
645 missing_items: &[Ident],
646 annotation_span: Option<Span>,
648 let missing_items_msg =
649 missing_items.iter().map(Ident::to_string).collect::<Vec<_>>().join("`, `");
651 let mut err = struct_span_err!(
655 "not all trait items implemented, missing one of: `{missing_items_msg}`",
657 err.span_label(impl_span, format!("missing one of `{missing_items_msg}` in implementation"));
659 if let Some(annotation_span) = annotation_span {
660 err.span_note(annotation_span, "required because of this annotation");
666 /// Re-sugar `ty::GenericPredicates` in a way suitable to be used in structured suggestions.
667 fn bounds_from_generic_predicates<'tcx>(
669 predicates: ty::GenericPredicates<'tcx>,
670 ) -> (String, String) {
671 let mut types: FxHashMap<Ty<'tcx>, Vec<DefId>> = FxHashMap::default();
672 let mut projections = vec![];
673 for (predicate, _) in predicates.predicates {
674 debug!("predicate {:?}", predicate);
675 let bound_predicate = predicate.kind();
676 match bound_predicate.skip_binder() {
677 ty::PredicateKind::Trait(trait_predicate) => {
678 let entry = types.entry(trait_predicate.self_ty()).or_default();
679 let def_id = trait_predicate.def_id();
680 if Some(def_id) != tcx.lang_items().sized_trait() {
681 // Type params are `Sized` by default, do not add that restriction to the list
682 // if it is a positive requirement.
683 entry.push(trait_predicate.def_id());
686 ty::PredicateKind::Projection(projection_pred) => {
687 projections.push(bound_predicate.rebind(projection_pred));
692 let generics = if types.is_empty() {
699 .filter_map(|t| match t.kind() {
700 ty::Param(_) => Some(t.to_string()),
701 // Avoid suggesting the following:
702 // fn foo<T, <T as Trait>::Bar>(_: T) where T: Trait, <T as Trait>::Bar: Other {}
709 let mut where_clauses = vec![];
710 for (ty, bounds) in types {
712 .extend(bounds.into_iter().map(|bound| format!("{}: {}", ty, tcx.def_path_str(bound))));
714 for projection in &projections {
715 let p = projection.skip_binder();
716 // FIXME: this is not currently supported syntax, we should be looking at the `types` and
717 // insert the associated types where they correspond, but for now let's be "lazy" and
718 // propose this instead of the following valid resugaring:
719 // `T: Trait, Trait::Assoc = K` → `T: Trait<Assoc = K>`
720 where_clauses.push(format!(
722 tcx.def_path_str(p.projection_ty.item_def_id),
726 let where_clauses = if where_clauses.is_empty() {
729 format!(" where {}", where_clauses.join(", "))
731 (generics, where_clauses)
734 /// Return placeholder code for the given function.
735 fn fn_sig_suggestion<'tcx>(
737 sig: ty::FnSig<'tcx>,
739 predicates: ty::GenericPredicates<'tcx>,
740 assoc: &ty::AssocItem,
747 Some(match ty.kind() {
748 ty::Param(_) if assoc.fn_has_self_parameter && i == 0 => "self".to_string(),
749 ty::Ref(reg, ref_ty, mutability) if i == 0 => {
750 let reg = format!("{reg} ");
751 let reg = match ®[..] {
755 if assoc.fn_has_self_parameter {
756 match ref_ty.kind() {
757 ty::Param(param) if param.name == kw::SelfUpper => {
758 format!("&{}{}self", reg, mutability.prefix_str())
761 _ => format!("self: {ty}"),
768 if assoc.fn_has_self_parameter && i == 0 {
769 format!("self: {ty}")
776 .chain(std::iter::once(if sig.c_variadic { Some("...".to_string()) } else { None }))
778 .collect::<Vec<String>>()
780 let output = sig.output();
781 let output = if !output.is_unit() { format!(" -> {output}") } else { String::new() };
783 let unsafety = sig.unsafety.prefix_str();
784 let (generics, where_clauses) = bounds_from_generic_predicates(tcx, predicates);
786 // FIXME: this is not entirely correct, as the lifetimes from borrowed params will
787 // not be present in the `fn` definition, not will we account for renamed
788 // lifetimes between the `impl` and the `trait`, but this should be good enough to
789 // fill in a significant portion of the missing code, and other subsequent
790 // suggestions can help the user fix the code.
791 format!("{unsafety}fn {ident}{generics}({args}){output}{where_clauses} {{ todo!() }}")
794 /// Return placeholder code for the given associated item.
795 /// Similar to `ty::AssocItem::suggestion`, but appropriate for use as the code snippet of a
796 /// structured suggestion.
797 fn suggestion_signature(assoc: &ty::AssocItem, tcx: TyCtxt<'_>) -> String {
799 ty::AssocKind::Fn => {
800 // We skip the binder here because the binder would deanonymize all
801 // late-bound regions, and we don't want method signatures to show up
802 // `as for<'r> fn(&'r MyType)`. Pretty-printing handles late-bound
803 // regions just fine, showing `fn(&MyType)`.
806 tcx.fn_sig(assoc.def_id).skip_binder(),
808 tcx.predicates_of(assoc.def_id),
812 ty::AssocKind::Type => format!("type {} = Type;", assoc.name),
813 ty::AssocKind::Const => {
814 let ty = tcx.type_of(assoc.def_id);
815 let val = expr::ty_kind_suggestion(ty).unwrap_or("value");
816 format!("const {}: {} = {};", assoc.name, ty, val)
821 /// Emit an error when encountering two or more variants in a transparent enum.
822 fn bad_variant_count<'tcx>(tcx: TyCtxt<'tcx>, adt: ty::AdtDef<'tcx>, sp: Span, did: DefId) {
823 let variant_spans: Vec<_> = adt
826 .map(|variant| tcx.hir().span_if_local(variant.def_id).unwrap())
828 let msg = format!("needs exactly one variant, but has {}", adt.variants().len(),);
829 let mut err = struct_span_err!(tcx.sess, sp, E0731, "transparent enum {msg}");
830 err.span_label(sp, &msg);
831 if let [start @ .., end] = &*variant_spans {
832 for variant_span in start {
833 err.span_label(*variant_span, "");
835 err.span_label(*end, &format!("too many variants in `{}`", tcx.def_path_str(did)));
840 /// Emit an error when encountering two or more non-zero-sized fields in a transparent
842 fn bad_non_zero_sized_fields<'tcx>(
844 adt: ty::AdtDef<'tcx>,
846 field_spans: impl Iterator<Item = Span>,
849 let msg = format!("needs at most one non-zero-sized field, but has {field_count}");
850 let mut err = struct_span_err!(
854 "{}transparent {} {}",
855 if adt.is_enum() { "the variant of a " } else { "" },
859 err.span_label(sp, &msg);
860 for sp in field_spans {
861 err.span_label(sp, "this field is non-zero-sized");
866 fn report_unexpected_variant_res(tcx: TyCtxt<'_>, res: Res, span: Span) {
871 "expected unit struct, unit variant or constant, found {}{}",
875 .span_to_snippet(span)
876 .map_or_else(|_| String::new(), |s| format!(" `{s}`",)),
881 /// Controls whether the arguments are tupled. This is used for the call
884 /// Tupling means that all call-side arguments are packed into a tuple and
885 /// passed as a single parameter. For example, if tupling is enabled, this
888 /// fn f(x: (isize, isize)) {}
890 /// Can be called as:
891 /// ```ignore UNSOLVED (can this be done in user code?)
892 /// # fn f(x: (isize, isize)) {}
897 /// # fn f(x: (isize, isize)) {}
900 #[derive(Clone, Eq, PartialEq)]
901 enum TupleArgumentsFlag {
906 /// A wrapper for `InferCtxt`'s `in_progress_typeck_results` field.
907 #[derive(Copy, Clone)]
908 struct MaybeInProgressTables<'a, 'tcx> {
909 maybe_typeck_results: Option<&'a RefCell<ty::TypeckResults<'tcx>>>,
912 impl<'a, 'tcx> MaybeInProgressTables<'a, 'tcx> {
913 fn borrow(self) -> Ref<'a, ty::TypeckResults<'tcx>> {
914 match self.maybe_typeck_results {
915 Some(typeck_results) => typeck_results.borrow(),
917 "MaybeInProgressTables: inh/fcx.typeck_results.borrow() with no typeck results"
922 fn borrow_mut(self) -> RefMut<'a, ty::TypeckResults<'tcx>> {
923 match self.maybe_typeck_results {
924 Some(typeck_results) => typeck_results.borrow_mut(),
926 "MaybeInProgressTables: inh/fcx.typeck_results.borrow_mut() with no typeck results"
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 }
969 /// Suggests calling the constructor of a tuple struct or enum variant
971 /// * `snippet` - The snippet of code that references the constructor
972 /// * `span` - The span of the snippet
973 /// * `params` - The number of parameters the constructor accepts
974 /// * `err` - A mutable diagnostic builder to add the suggestion to
975 fn suggest_call_constructor<G: EmissionGuarantee>(
979 err: &mut DiagnosticBuilder<'_, G>,
981 // Note: tuple-structs don't have named fields, so just use placeholders
982 let args = vec!["_"; params].join(", ");
983 let applicable = if params > 0 {
984 Applicability::HasPlaceholders
986 // When n = 0, it's an empty-tuple struct/enum variant
987 // so we trivially know how to construct it
988 Applicability::MachineApplicable
990 let kind = match kind {
991 CtorOf::Struct => "a struct",
992 CtorOf::Variant => "an enum variant",
994 err.span_label(span, &format!("this is the constructor of {kind}"));
995 err.multipart_suggestion(
996 "call the constructor",
997 vec![(span.shrink_to_lo(), "(".to_string()), (span.shrink_to_hi(), format!(")({args})"))],