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 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
80 mod generator_interior;
93 check_abi, check_fn, check_impl_item_well_formed, check_item_well_formed, check_mod_item_types,
94 check_trait_item_well_formed,
96 pub use check::{check_item_type, check_wf_new};
97 pub use diverges::Diverges;
98 pub use expectation::Expectation;
100 pub use inherited::{Inherited, InheritedBuilder};
102 use crate::astconv::AstConv;
103 use crate::check::gather_locals::GatherLocalsVisitor;
104 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
105 use rustc_errors::{pluralize, struct_span_err, Applicability};
106 use rustc_hir as hir;
107 use rustc_hir::def::Res;
108 use rustc_hir::def_id::{DefId, LocalDefId};
109 use rustc_hir::intravisit::Visitor;
110 use rustc_hir::itemlikevisit::ItemLikeVisitor;
111 use rustc_hir::{HirIdMap, ImplicitSelfKind, Node};
112 use rustc_index::bit_set::BitSet;
113 use rustc_index::vec::Idx;
114 use rustc_infer::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
115 use rustc_middle::ty::query::Providers;
116 use rustc_middle::ty::subst::{InternalSubsts, Subst, SubstsRef};
117 use rustc_middle::ty::{self, Ty, TyCtxt, UserType};
118 use rustc_session::config;
119 use rustc_session::parse::feature_err;
120 use rustc_session::Session;
121 use rustc_span::source_map::DUMMY_SP;
122 use rustc_span::symbol::{kw, Ident};
123 use rustc_span::{self, BytePos, MultiSpan, Span};
124 use rustc_target::abi::VariantIdx;
125 use rustc_target::spec::abi::Abi;
126 use rustc_trait_selection::traits;
127 use rustc_trait_selection::traits::error_reporting::recursive_type_with_infinite_size_error;
128 use rustc_trait_selection::traits::error_reporting::suggestions::ReturnsVisitor;
130 use std::cell::{Ref, RefCell, RefMut};
132 use crate::require_c_abi_if_c_variadic;
133 use crate::util::common::indenter;
135 use self::coercion::DynamicCoerceMany;
136 pub use self::Expectation::*;
139 macro_rules! type_error_struct {
140 ($session:expr, $span:expr, $typ:expr, $code:ident, $($message:tt)*) => ({
141 if $typ.references_error() {
142 $session.diagnostic().struct_dummy()
144 rustc_errors::struct_span_err!($session, $span, $code, $($message)*)
149 /// The type of a local binding, including the revealed type for anon types.
150 #[derive(Copy, Clone, Debug)]
151 pub struct LocalTy<'tcx> {
153 revealed_ty: Ty<'tcx>,
156 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
163 fn maybe_mut_place(m: hir::Mutability) -> Self {
165 hir::Mutability::Mut => Needs::MutPlace,
166 hir::Mutability::Not => Needs::None,
171 #[derive(Copy, Clone)]
172 pub struct UnsafetyState {
174 pub unsafety: hir::Unsafety,
179 pub fn function(unsafety: hir::Unsafety, def: hir::HirId) -> UnsafetyState {
180 UnsafetyState { def, unsafety, from_fn: true }
183 pub fn recurse(self, blk: &hir::Block<'_>) -> UnsafetyState {
184 use hir::BlockCheckMode;
185 match self.unsafety {
186 // If this unsafe, then if the outer function was already marked as
187 // unsafe we shouldn't attribute the unsafe'ness to the block. This
188 // way the block can be warned about instead of ignoring this
189 // extraneous block (functions are never warned about).
190 hir::Unsafety::Unsafe if self.from_fn => self,
193 let (unsafety, def) = match blk.rules {
194 BlockCheckMode::UnsafeBlock(..) => (hir::Unsafety::Unsafe, blk.hir_id),
195 BlockCheckMode::DefaultBlock => (unsafety, self.def),
197 UnsafetyState { def, unsafety, from_fn: false }
203 #[derive(Debug, Copy, Clone)]
209 pub struct BreakableCtxt<'tcx> {
212 // this is `null` for loops where break with a value is illegal,
213 // such as `while`, `for`, and `while let`
214 coerce: Option<DynamicCoerceMany<'tcx>>,
217 pub struct EnclosingBreakables<'tcx> {
218 stack: Vec<BreakableCtxt<'tcx>>,
219 by_id: HirIdMap<usize>,
222 impl<'tcx> EnclosingBreakables<'tcx> {
223 fn find_breakable(&mut self, target_id: hir::HirId) -> &mut BreakableCtxt<'tcx> {
224 self.opt_find_breakable(target_id).unwrap_or_else(|| {
225 bug!("could not find enclosing breakable with id {}", target_id);
229 fn opt_find_breakable(&mut self, target_id: hir::HirId) -> Option<&mut BreakableCtxt<'tcx>> {
230 match self.by_id.get(&target_id) {
231 Some(ix) => Some(&mut self.stack[*ix]),
237 pub fn provide(providers: &mut Providers) {
238 method::provide(providers);
239 *providers = Providers {
243 diagnostic_only_typeck,
247 check_item_well_formed,
248 check_trait_item_well_formed,
249 check_impl_item_well_formed,
250 check_mod_item_types,
255 fn adt_destructor(tcx: TyCtxt<'_>, def_id: DefId) -> Option<ty::Destructor> {
256 tcx.calculate_dtor(def_id, dropck::check_drop_impl)
259 /// If this `DefId` is a "primary tables entry", returns
260 /// `Some((body_id, header, decl))` with information about
261 /// its body-id, fn-header and fn-decl (if any). Otherwise,
264 /// If this function returns `Some`, then `typeck_results(def_id)` will
265 /// succeed; if it returns `None`, then `typeck_results(def_id)` may or
266 /// may not succeed. In some cases where this function returns `None`
267 /// (notably closures), `typeck_results(def_id)` would wind up
268 /// redirecting to the owning function.
272 ) -> Option<(hir::BodyId, Option<&hir::Ty<'_>>, Option<&hir::FnHeader>, Option<&hir::FnDecl<'_>>)> {
273 match tcx.hir().get(id) {
274 Node::Item(item) => match item.kind {
275 hir::ItemKind::Const(ref ty, body) | hir::ItemKind::Static(ref ty, _, body) => {
276 Some((body, Some(ty), None, None))
278 hir::ItemKind::Fn(ref sig, .., body) => {
279 Some((body, None, Some(&sig.header), Some(&sig.decl)))
283 Node::TraitItem(item) => match item.kind {
284 hir::TraitItemKind::Const(ref ty, Some(body)) => Some((body, Some(ty), None, None)),
285 hir::TraitItemKind::Fn(ref sig, hir::TraitFn::Provided(body)) => {
286 Some((body, None, Some(&sig.header), Some(&sig.decl)))
290 Node::ImplItem(item) => match item.kind {
291 hir::ImplItemKind::Const(ref ty, body) => Some((body, Some(ty), None, None)),
292 hir::ImplItemKind::Fn(ref sig, body) => {
293 Some((body, None, Some(&sig.header), Some(&sig.decl)))
297 Node::AnonConst(constant) => Some((constant.body, None, None, None)),
302 fn has_typeck_results(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
303 // Closures' typeck results come from their outermost function,
304 // as they are part of the same "inference environment".
305 let outer_def_id = tcx.closure_base_def_id(def_id);
306 if outer_def_id != def_id {
307 return tcx.has_typeck_results(outer_def_id);
310 if let Some(def_id) = def_id.as_local() {
311 let id = tcx.hir().local_def_id_to_hir_id(def_id);
312 primary_body_of(tcx, id).is_some()
318 fn used_trait_imports(tcx: TyCtxt<'_>, def_id: LocalDefId) -> &FxHashSet<LocalDefId> {
319 &*tcx.typeck(def_id).used_trait_imports
322 fn typeck_const_arg<'tcx>(
324 (did, param_did): (LocalDefId, DefId),
325 ) -> &ty::TypeckResults<'tcx> {
326 let fallback = move || tcx.type_of(param_did);
327 typeck_with_fallback(tcx, did, fallback)
330 fn typeck<'tcx>(tcx: TyCtxt<'tcx>, def_id: LocalDefId) -> &ty::TypeckResults<'tcx> {
331 if let Some(param_did) = tcx.opt_const_param_of(def_id) {
332 tcx.typeck_const_arg((def_id, param_did))
334 let fallback = move || tcx.type_of(def_id.to_def_id());
335 typeck_with_fallback(tcx, def_id, fallback)
339 /// Used only to get `TypeckResults` for type inference during error recovery.
340 /// Currently only used for type inference of `static`s and `const`s to avoid type cycle errors.
341 fn diagnostic_only_typeck<'tcx>(tcx: TyCtxt<'tcx>, def_id: LocalDefId) -> &ty::TypeckResults<'tcx> {
342 let fallback = move || {
343 let span = tcx.hir().span(tcx.hir().local_def_id_to_hir_id(def_id));
344 tcx.ty_error_with_message(span, "diagnostic only typeck table used")
346 typeck_with_fallback(tcx, def_id, fallback)
349 fn typeck_with_fallback<'tcx>(
352 fallback: impl Fn() -> Ty<'tcx> + 'tcx,
353 ) -> &'tcx ty::TypeckResults<'tcx> {
354 // Closures' typeck results come from their outermost function,
355 // as they are part of the same "inference environment".
356 let outer_def_id = tcx.closure_base_def_id(def_id.to_def_id()).expect_local();
357 if outer_def_id != def_id {
358 return tcx.typeck(outer_def_id);
361 let id = tcx.hir().local_def_id_to_hir_id(def_id);
362 let span = tcx.hir().span(id);
364 // Figure out what primary body this item has.
365 let (body_id, body_ty, fn_header, fn_decl) = primary_body_of(tcx, id).unwrap_or_else(|| {
366 span_bug!(span, "can't type-check body of {:?}", def_id);
368 let body = tcx.hir().body(body_id);
370 let typeck_results = Inherited::build(tcx, def_id).enter(|inh| {
371 let param_env = tcx.param_env(def_id);
372 let fcx = if let (Some(header), Some(decl)) = (fn_header, fn_decl) {
373 let fn_sig = if crate::collect::get_infer_ret_ty(&decl.output).is_some() {
374 let fcx = FnCtxt::new(&inh, param_env, body.value.hir_id);
375 <dyn AstConv<'_>>::ty_of_fn(
381 &hir::Generics::empty(),
389 check_abi(tcx, id, span, fn_sig.abi());
391 // Compute the fty from point of view of inside the fn.
392 let fn_sig = tcx.liberate_late_bound_regions(def_id.to_def_id(), fn_sig);
393 let fn_sig = inh.normalize_associated_types_in(
400 let fcx = check_fn(&inh, param_env, fn_sig, decl, id, body, None).0;
403 let fcx = FnCtxt::new(&inh, param_env, body.value.hir_id);
404 let expected_type = body_ty
405 .and_then(|ty| match ty.kind {
406 hir::TyKind::Infer => Some(<dyn AstConv<'_>>::ast_ty_to_ty(&fcx, ty)),
409 .unwrap_or_else(|| match tcx.hir().get(id) {
410 Node::AnonConst(_) => match tcx.hir().get(tcx.hir().get_parent_node(id)) {
411 Node::Expr(&hir::Expr {
412 kind: hir::ExprKind::ConstBlock(ref anon_const),
414 }) if anon_const.hir_id == id => fcx.next_ty_var(TypeVariableOrigin {
415 kind: TypeVariableOriginKind::TypeInference,
419 kind: hir::TyKind::Typeof(ref anon_const), ..
420 }) if anon_const.hir_id == id => fcx.next_ty_var(TypeVariableOrigin {
421 kind: TypeVariableOriginKind::TypeInference,
424 Node::Expr(&hir::Expr { kind: hir::ExprKind::InlineAsm(asm), .. })
425 | Node::Item(&hir::Item { kind: hir::ItemKind::GlobalAsm(asm), .. })
426 if asm.operands.iter().any(|(op, _op_sp)| match op {
427 hir::InlineAsmOperand::Const { anon_const } => {
428 anon_const.hir_id == id
433 // Inline assembly constants must be integers.
441 let expected_type = fcx.normalize_associated_types_in(body.value.span, expected_type);
442 fcx.require_type_is_sized(expected_type, body.value.span, traits::ConstSized);
444 // Gather locals in statics (because of block expressions).
445 GatherLocalsVisitor::new(&fcx).visit_body(body);
447 fcx.check_expr_coercable_to_type(&body.value, expected_type, None);
449 fcx.write_ty(id, expected_type);
454 // All type checking constraints were added, try to fallback unsolved variables.
455 fcx.select_obligations_where_possible(false, |_| {});
456 let mut fallback_has_occurred = false;
458 // We do fallback in two passes, to try to generate
459 // better error messages.
460 // The first time, we do *not* replace opaque types.
461 for ty in &fcx.unsolved_variables() {
462 fallback_has_occurred |= fcx.fallback_if_possible(ty, FallbackMode::NoOpaque);
464 // We now see if we can make progress. This might
465 // cause us to unify inference variables for opaque types,
466 // since we may have unified some other type variables
467 // during the first phase of fallback.
468 // This means that we only replace inference variables with their underlying
469 // opaque types as a last resort.
471 // In code like this:
474 // type MyType = impl Copy;
475 // fn produce() -> MyType { true }
476 // fn bad_produce() -> MyType { panic!() }
479 // we want to unify the opaque inference variable in `bad_produce`
480 // with the diverging fallback for `panic!` (e.g. `()` or `!`).
481 // This will produce a nice error message about conflicting concrete
482 // types for `MyType`.
484 // If we had tried to fallback the opaque inference variable to `MyType`,
485 // we will generate a confusing type-check error that does not explicitly
486 // refer to opaque types.
487 fcx.select_obligations_where_possible(fallback_has_occurred, |_| {});
489 // We now run fallback again, but this time we allow it to replace
490 // unconstrained opaque type variables, in addition to performing
491 // other kinds of fallback.
492 for ty in &fcx.unsolved_variables() {
493 fallback_has_occurred |= fcx.fallback_if_possible(ty, FallbackMode::All);
496 // See if we can make any more progress.
497 fcx.select_obligations_where_possible(fallback_has_occurred, |_| {});
499 // Even though coercion casts provide type hints, we check casts after fallback for
500 // backwards compatibility. This makes fallback a stronger type hint than a cast coercion.
503 // Closure and generator analysis may run after fallback
504 // because they don't constrain other type variables.
505 fcx.closure_analyze(body);
506 assert!(fcx.deferred_call_resolutions.borrow().is_empty());
507 fcx.resolve_generator_interiors(def_id.to_def_id());
509 for (ty, span, code) in fcx.deferred_sized_obligations.borrow_mut().drain(..) {
510 let ty = fcx.normalize_ty(span, ty);
511 fcx.require_type_is_sized(ty, span, code);
514 fcx.select_all_obligations_or_error();
516 if fn_decl.is_some() {
517 fcx.regionck_fn(id, body);
519 fcx.regionck_expr(body);
522 fcx.resolve_type_vars_in_body(body)
525 // Consistency check our TypeckResults instance can hold all ItemLocalIds
526 // it will need to hold.
527 assert_eq!(typeck_results.hir_owner, id.owner);
532 /// When `check_fn` is invoked on a generator (i.e., a body that
533 /// includes yield), it returns back some information about the yield
535 struct GeneratorTypes<'tcx> {
536 /// Type of generator argument / values returned by `yield`.
539 /// Type of value that is yielded.
542 /// Types that are captured (see `GeneratorInterior` for more).
545 /// Indicates if the generator is movable or static (immovable).
546 movability: hir::Movability,
549 /// Given a `DefId` for an opaque type in return position, find its parent item's return
551 fn get_owner_return_paths(
554 ) -> Option<(hir::HirId, ReturnsVisitor<'tcx>)> {
555 let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
556 let id = tcx.hir().get_parent_item(hir_id);
560 .and_then(|(hir_id, node)| node.body_id().map(|b| (hir_id, b)))
561 .map(|(hir_id, body_id)| {
562 let body = tcx.hir().body(body_id);
563 let mut visitor = ReturnsVisitor::default();
564 visitor.visit_body(body);
569 // Forbid defining intrinsics in Rust code,
570 // as they must always be defined by the compiler.
571 fn fn_maybe_err(tcx: TyCtxt<'_>, sp: Span, abi: Abi) {
572 if let Abi::RustIntrinsic | Abi::PlatformIntrinsic = abi {
573 tcx.sess.span_err(sp, "intrinsic must be in `extern \"rust-intrinsic\" { ... }` block");
577 fn maybe_check_static_with_link_section(tcx: TyCtxt<'_>, id: LocalDefId, span: Span) {
578 // Only restricted on wasm32 target for now
579 if !tcx.sess.opts.target_triple.triple().starts_with("wasm32") {
583 // If `#[link_section]` is missing, then nothing to verify
584 let attrs = tcx.codegen_fn_attrs(id);
585 if attrs.link_section.is_none() {
589 // For the wasm32 target statics with `#[link_section]` are placed into custom
590 // sections of the final output file, but this isn't link custom sections of
591 // other executable formats. Namely we can only embed a list of bytes,
592 // nothing with pointers to anything else or relocations. If any relocation
593 // show up, reject them here.
594 // `#[link_section]` may contain arbitrary, or even undefined bytes, but it is
595 // the consumer's responsibility to ensure all bytes that have been read
596 // have defined values.
597 match tcx.eval_static_initializer(id.to_def_id()) {
599 if alloc.relocations().len() != 0 {
600 let msg = "statics with a custom `#[link_section]` must be a \
601 simple list of bytes on the wasm target with no \
602 extra levels of indirection such as references";
603 tcx.sess.span_err(span, msg);
610 fn report_forbidden_specialization(
612 impl_item: &hir::ImplItem<'_>,
615 let mut err = struct_span_err!(
619 "`{}` specializes an item from a parent `impl`, but \
620 that item is not marked `default`",
623 err.span_label(impl_item.span, format!("cannot specialize default item `{}`", impl_item.ident));
625 match tcx.span_of_impl(parent_impl) {
627 err.span_label(span, "parent `impl` is here");
629 "to specialize, `{}` in the parent `impl` must be marked `default`",
634 err.note(&format!("parent implementation is in crate `{}`", cname));
641 fn missing_items_err(
644 missing_items: &[ty::AssocItem],
645 full_impl_span: Span,
647 let missing_items_msg = missing_items
649 .map(|trait_item| trait_item.ident.to_string())
653 let mut err = struct_span_err!(
657 "not all trait items implemented, missing: `{}`",
660 err.span_label(impl_span, format!("missing `{}` in implementation", missing_items_msg));
662 // `Span` before impl block closing brace.
663 let hi = full_impl_span.hi() - BytePos(1);
664 // Point at the place right before the closing brace of the relevant `impl` to suggest
665 // adding the associated item at the end of its body.
666 let sugg_sp = full_impl_span.with_lo(hi).with_hi(hi);
667 // Obtain the level of indentation ending in `sugg_sp`.
668 let indentation = tcx.sess.source_map().span_to_margin(sugg_sp).unwrap_or(0);
669 // Make the whitespace that will make the suggestion have the right indentation.
670 let padding: String = " ".repeat(indentation);
672 for trait_item in missing_items {
673 let snippet = suggestion_signature(&trait_item, tcx);
674 let code = format!("{}{}\n{}", padding, snippet, padding);
675 let msg = format!("implement the missing item: `{}`", snippet);
676 let appl = Applicability::HasPlaceholders;
677 if let Some(span) = tcx.hir().span_if_local(trait_item.def_id) {
678 err.span_label(span, format!("`{}` from trait", trait_item.ident));
679 err.tool_only_span_suggestion(sugg_sp, &msg, code, appl);
681 err.span_suggestion_hidden(sugg_sp, &msg, code, appl);
687 /// Resugar `ty::GenericPredicates` in a way suitable to be used in structured suggestions.
688 fn bounds_from_generic_predicates<'tcx>(
690 predicates: ty::GenericPredicates<'tcx>,
691 ) -> (String, String) {
692 let mut types: FxHashMap<Ty<'tcx>, Vec<DefId>> = FxHashMap::default();
693 let mut projections = vec![];
694 for (predicate, _) in predicates.predicates {
695 debug!("predicate {:?}", predicate);
696 let bound_predicate = predicate.kind();
697 match bound_predicate.skip_binder() {
698 ty::PredicateKind::Trait(trait_predicate, _) => {
699 let entry = types.entry(trait_predicate.self_ty()).or_default();
700 let def_id = trait_predicate.def_id();
701 if Some(def_id) != tcx.lang_items().sized_trait() {
702 // Type params are `Sized` by default, do not add that restriction to the list
703 // if it is a positive requirement.
704 entry.push(trait_predicate.def_id());
707 ty::PredicateKind::Projection(projection_pred) => {
708 projections.push(bound_predicate.rebind(projection_pred));
713 let generics = if types.is_empty() {
720 .filter_map(|t| match t.kind() {
721 ty::Param(_) => Some(t.to_string()),
722 // Avoid suggesting the following:
723 // fn foo<T, <T as Trait>::Bar>(_: T) where T: Trait, <T as Trait>::Bar: Other {}
730 let mut where_clauses = vec![];
731 for (ty, bounds) in types {
732 for bound in &bounds {
733 where_clauses.push(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!("{} = {}", tcx.def_path_str(p.projection_ty.item_def_id), p.ty));
744 let where_clauses = if where_clauses.is_empty() {
747 format!(" where {}", where_clauses.join(", "))
749 (generics, where_clauses)
752 /// Return placeholder code for the given function.
753 fn fn_sig_suggestion<'tcx>(
755 sig: ty::FnSig<'tcx>,
757 predicates: ty::GenericPredicates<'tcx>,
758 assoc: &ty::AssocItem,
765 Some(match ty.kind() {
766 ty::Param(_) if assoc.fn_has_self_parameter && i == 0 => "self".to_string(),
767 ty::Ref(reg, ref_ty, mutability) if i == 0 => {
768 let reg = match &format!("{}", reg)[..] {
769 "'_" | "" => String::new(),
770 reg => format!("{} ", reg),
772 if assoc.fn_has_self_parameter {
773 match ref_ty.kind() {
774 ty::Param(param) if param.name == kw::SelfUpper => {
775 format!("&{}{}self", reg, mutability.prefix_str())
778 _ => format!("self: {}", ty),
785 if assoc.fn_has_self_parameter && i == 0 {
786 format!("self: {}", ty)
793 .chain(std::iter::once(if sig.c_variadic { Some("...".to_string()) } else { None }))
794 .filter_map(|arg| arg)
795 .collect::<Vec<String>>()
797 let output = sig.output();
798 let output = if !output.is_unit() { format!(" -> {}", output) } else { String::new() };
800 let unsafety = sig.unsafety.prefix_str();
801 let (generics, where_clauses) = bounds_from_generic_predicates(tcx, predicates);
803 // FIXME: this is not entirely correct, as the lifetimes from borrowed params will
804 // not be present in the `fn` definition, not will we account for renamed
805 // lifetimes between the `impl` and the `trait`, but this should be good enough to
806 // fill in a significant portion of the missing code, and other subsequent
807 // suggestions can help the user fix the code.
809 "{}fn {}{}({}){}{} {{ todo!() }}",
810 unsafety, ident, generics, args, output, where_clauses
814 /// Return placeholder code for the given associated item.
815 /// Similar to `ty::AssocItem::suggestion`, but appropriate for use as the code snippet of a
816 /// structured suggestion.
817 fn suggestion_signature(assoc: &ty::AssocItem, tcx: TyCtxt<'_>) -> String {
819 ty::AssocKind::Fn => {
820 // We skip the binder here because the binder would deanonymize all
821 // late-bound regions, and we don't want method signatures to show up
822 // `as for<'r> fn(&'r MyType)`. Pretty-printing handles late-bound
823 // regions just fine, showing `fn(&MyType)`.
826 tcx.fn_sig(assoc.def_id).skip_binder(),
828 tcx.predicates_of(assoc.def_id),
832 ty::AssocKind::Type => format!("type {} = Type;", assoc.ident),
833 ty::AssocKind::Const => {
834 let ty = tcx.type_of(assoc.def_id);
835 let val = expr::ty_kind_suggestion(ty).unwrap_or("value");
836 format!("const {}: {} = {};", assoc.ident, ty, val)
841 /// Emit an error when encountering two or more variants in a transparent enum.
842 fn bad_variant_count<'tcx>(tcx: TyCtxt<'tcx>, adt: &'tcx ty::AdtDef, sp: Span, did: DefId) {
843 let variant_spans: Vec<_> = adt
846 .map(|variant| tcx.hir().span_if_local(variant.def_id).unwrap())
848 let msg = format!("needs exactly one variant, but has {}", adt.variants.len(),);
849 let mut err = struct_span_err!(tcx.sess, sp, E0731, "transparent enum {}", msg);
850 err.span_label(sp, &msg);
851 if let [start @ .., end] = &*variant_spans {
852 for variant_span in start {
853 err.span_label(*variant_span, "");
855 err.span_label(*end, &format!("too many variants in `{}`", tcx.def_path_str(did)));
860 /// Emit an error when encountering two or more non-zero-sized fields in a transparent
862 fn bad_non_zero_sized_fields<'tcx>(
864 adt: &'tcx ty::AdtDef,
866 field_spans: impl Iterator<Item = Span>,
869 let msg = format!("needs at most one non-zero-sized field, but has {}", field_count);
870 let mut err = struct_span_err!(
874 "{}transparent {} {}",
875 if adt.is_enum() { "the variant of a " } else { "" },
879 err.span_label(sp, &msg);
880 for sp in field_spans {
881 err.span_label(sp, "this field is non-zero-sized");
886 fn report_unexpected_variant_res(tcx: TyCtxt<'_>, res: Res, span: Span) {
891 "expected unit struct, unit variant or constant, found {}{}",
895 .span_to_snippet(span)
896 .map_or_else(|_| String::new(), |s| format!(" `{}`", s)),
901 /// Controls whether the arguments are tupled. This is used for the call
904 /// Tupling means that all call-side arguments are packed into a tuple and
905 /// passed as a single parameter. For example, if tupling is enabled, this
908 /// fn f(x: (isize, isize))
910 /// Can be called as:
917 #[derive(Clone, Eq, PartialEq)]
918 enum TupleArgumentsFlag {
923 /// Controls how we perform fallback for unconstrained
926 /// Do not fallback type variables to opaque types.
928 /// Perform all possible kinds of fallback, including
929 /// turning type variables to opaque types.
933 /// A wrapper for `InferCtxt`'s `in_progress_typeck_results` field.
934 #[derive(Copy, Clone)]
935 struct MaybeInProgressTables<'a, 'tcx> {
936 maybe_typeck_results: Option<&'a RefCell<ty::TypeckResults<'tcx>>>,
939 impl<'a, 'tcx> MaybeInProgressTables<'a, 'tcx> {
940 fn borrow(self) -> Ref<'a, ty::TypeckResults<'tcx>> {
941 match self.maybe_typeck_results {
942 Some(typeck_results) => typeck_results.borrow(),
944 "MaybeInProgressTables: inh/fcx.typeck_results.borrow() with no typeck results"
949 fn borrow_mut(self) -> RefMut<'a, ty::TypeckResults<'tcx>> {
950 match self.maybe_typeck_results {
951 Some(typeck_results) => typeck_results.borrow_mut(),
953 "MaybeInProgressTables: inh/fcx.typeck_results.borrow_mut() with no typeck results"
959 struct CheckItemTypesVisitor<'tcx> {
963 impl ItemLikeVisitor<'tcx> for CheckItemTypesVisitor<'tcx> {
964 fn visit_item(&mut self, i: &'tcx hir::Item<'tcx>) {
965 check_item_type(self.tcx, i);
967 fn visit_trait_item(&mut self, _: &'tcx hir::TraitItem<'tcx>) {}
968 fn visit_impl_item(&mut self, _: &'tcx hir::ImplItem<'tcx>) {}
969 fn visit_foreign_item(&mut self, _: &'tcx hir::ForeignItem<'tcx>) {}
972 fn typeck_item_bodies(tcx: TyCtxt<'_>, (): ()) {
973 tcx.par_body_owners(|body_owner_def_id| {
974 tcx.ensure().typeck(body_owner_def_id);
978 fn fatally_break_rust(sess: &Session) {
979 let handler = sess.diagnostic();
980 handler.span_bug_no_panic(
982 "It looks like you're trying to break rust; would you like some ICE?",
984 handler.note_without_error("the compiler expectedly panicked. this is a feature.");
985 handler.note_without_error(
986 "we would appreciate a joke overview: \
987 https://github.com/rust-lang/rust/issues/43162#issuecomment-320764675",
989 handler.note_without_error(&format!(
990 "rustc {} running on {}",
991 option_env!("CFG_VERSION").unwrap_or("unknown_version"),
992 config::host_triple(),
996 fn potentially_plural_count(count: usize, word: &str) -> String {
997 format!("{} {}{}", count, word, pluralize!(count))
1000 fn has_expected_num_generic_args<'tcx>(
1002 trait_did: Option<DefId>,
1005 trait_did.map_or(true, |trait_did| {
1006 let generics = tcx.generics_of(trait_did);
1007 generics.count() == expected + if generics.has_self { 1 } else { 0 }