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, body_ty, fn_sig))`. Otherwise, returns `None`.
262 /// If this function returns `Some`, then `typeck_results(def_id)` will
263 /// succeed; if it returns `None`, then `typeck_results(def_id)` may or
264 /// may not succeed. In some cases where this function returns `None`
265 /// (notably closures), `typeck_results(def_id)` would wind up
266 /// redirecting to the owning function.
270 ) -> Option<(hir::BodyId, Option<&hir::Ty<'_>>, Option<&hir::FnSig<'_>>)> {
271 match tcx.hir().get(id) {
272 Node::Item(item) => match item.kind {
273 hir::ItemKind::Const(ref ty, body) | hir::ItemKind::Static(ref ty, _, body) => {
274 Some((body, Some(ty), None))
276 hir::ItemKind::Fn(ref sig, .., body) => Some((body, None, Some(&sig))),
279 Node::TraitItem(item) => match item.kind {
280 hir::TraitItemKind::Const(ref ty, Some(body)) => Some((body, Some(ty), None)),
281 hir::TraitItemKind::Fn(ref sig, hir::TraitFn::Provided(body)) => {
282 Some((body, None, Some(&sig)))
286 Node::ImplItem(item) => match item.kind {
287 hir::ImplItemKind::Const(ref ty, body) => Some((body, Some(ty), None)),
288 hir::ImplItemKind::Fn(ref sig, body) => Some((body, None, Some(&sig))),
291 Node::AnonConst(constant) => Some((constant.body, None, None)),
296 fn has_typeck_results(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
297 // Closures' typeck results come from their outermost function,
298 // as they are part of the same "inference environment".
299 let outer_def_id = tcx.closure_base_def_id(def_id);
300 if outer_def_id != def_id {
301 return tcx.has_typeck_results(outer_def_id);
304 if let Some(def_id) = def_id.as_local() {
305 let id = tcx.hir().local_def_id_to_hir_id(def_id);
306 primary_body_of(tcx, id).is_some()
312 fn used_trait_imports(tcx: TyCtxt<'_>, def_id: LocalDefId) -> &FxHashSet<LocalDefId> {
313 &*tcx.typeck(def_id).used_trait_imports
316 fn typeck_const_arg<'tcx>(
318 (did, param_did): (LocalDefId, DefId),
319 ) -> &ty::TypeckResults<'tcx> {
320 let fallback = move || tcx.type_of(param_did);
321 typeck_with_fallback(tcx, did, fallback)
324 fn typeck<'tcx>(tcx: TyCtxt<'tcx>, def_id: LocalDefId) -> &ty::TypeckResults<'tcx> {
325 if let Some(param_did) = tcx.opt_const_param_of(def_id) {
326 tcx.typeck_const_arg((def_id, param_did))
328 let fallback = move || tcx.type_of(def_id.to_def_id());
329 typeck_with_fallback(tcx, def_id, fallback)
333 /// Used only to get `TypeckResults` for type inference during error recovery.
334 /// Currently only used for type inference of `static`s and `const`s to avoid type cycle errors.
335 fn diagnostic_only_typeck<'tcx>(tcx: TyCtxt<'tcx>, def_id: LocalDefId) -> &ty::TypeckResults<'tcx> {
336 let fallback = move || {
337 let span = tcx.hir().span(tcx.hir().local_def_id_to_hir_id(def_id));
338 tcx.ty_error_with_message(span, "diagnostic only typeck table used")
340 typeck_with_fallback(tcx, def_id, fallback)
343 fn typeck_with_fallback<'tcx>(
346 fallback: impl Fn() -> Ty<'tcx> + 'tcx,
347 ) -> &'tcx ty::TypeckResults<'tcx> {
348 // Closures' typeck results come from their outermost function,
349 // as they are part of the same "inference environment".
350 let outer_def_id = tcx.closure_base_def_id(def_id.to_def_id()).expect_local();
351 if outer_def_id != def_id {
352 return tcx.typeck(outer_def_id);
355 let id = tcx.hir().local_def_id_to_hir_id(def_id);
356 let span = tcx.hir().span(id);
358 // Figure out what primary body this item has.
359 let (body_id, body_ty, fn_sig) = primary_body_of(tcx, id).unwrap_or_else(|| {
360 span_bug!(span, "can't type-check body of {:?}", def_id);
362 let body = tcx.hir().body(body_id);
364 let typeck_results = Inherited::build(tcx, def_id).enter(|inh| {
365 let param_env = tcx.param_env(def_id);
366 let fcx = if let Some(hir::FnSig { header, decl, .. }) = fn_sig {
367 let fn_sig = if crate::collect::get_infer_ret_ty(&decl.output).is_some() {
368 let fcx = FnCtxt::new(&inh, param_env, body.value.hir_id);
369 <dyn AstConv<'_>>::ty_of_fn(
375 &hir::Generics::empty(),
383 check_abi(tcx, id, span, fn_sig.abi());
385 // Compute the fty from point of view of inside the fn.
386 let fn_sig = tcx.liberate_late_bound_regions(def_id.to_def_id(), fn_sig);
387 let fn_sig = inh.normalize_associated_types_in(
394 let fcx = check_fn(&inh, param_env, fn_sig, decl, id, body, None).0;
397 let fcx = FnCtxt::new(&inh, param_env, body.value.hir_id);
398 let expected_type = body_ty
399 .and_then(|ty| match ty.kind {
400 hir::TyKind::Infer => Some(<dyn AstConv<'_>>::ast_ty_to_ty(&fcx, ty)),
403 .unwrap_or_else(|| match tcx.hir().get(id) {
404 Node::AnonConst(_) => match tcx.hir().get(tcx.hir().get_parent_node(id)) {
405 Node::Expr(&hir::Expr {
406 kind: hir::ExprKind::ConstBlock(ref anon_const),
408 }) if anon_const.hir_id == id => fcx.next_ty_var(TypeVariableOrigin {
409 kind: TypeVariableOriginKind::TypeInference,
413 kind: hir::TyKind::Typeof(ref anon_const), ..
414 }) if anon_const.hir_id == id => fcx.next_ty_var(TypeVariableOrigin {
415 kind: TypeVariableOriginKind::TypeInference,
418 Node::Expr(&hir::Expr { kind: hir::ExprKind::InlineAsm(asm), .. })
419 | Node::Item(&hir::Item { kind: hir::ItemKind::GlobalAsm(asm), .. })
420 if asm.operands.iter().any(|(op, _op_sp)| match op {
421 hir::InlineAsmOperand::Const { anon_const } => {
422 anon_const.hir_id == id
427 // Inline assembly constants must be integers.
435 let expected_type = fcx.normalize_associated_types_in(body.value.span, expected_type);
436 fcx.require_type_is_sized(expected_type, body.value.span, traits::ConstSized);
438 // Gather locals in statics (because of block expressions).
439 GatherLocalsVisitor::new(&fcx).visit_body(body);
441 fcx.check_expr_coercable_to_type(&body.value, expected_type, None);
443 fcx.write_ty(id, expected_type);
448 // All type checking constraints were added, try to fallback unsolved variables.
449 fcx.select_obligations_where_possible(false, |_| {});
450 let mut fallback_has_occurred = false;
452 // We do fallback in two passes, to try to generate
453 // better error messages.
454 // The first time, we do *not* replace opaque types.
455 for ty in &fcx.unsolved_variables() {
456 fallback_has_occurred |= fcx.fallback_if_possible(ty, FallbackMode::NoOpaque);
458 // We now see if we can make progress. This might
459 // cause us to unify inference variables for opaque types,
460 // since we may have unified some other type variables
461 // during the first phase of fallback.
462 // This means that we only replace inference variables with their underlying
463 // opaque types as a last resort.
465 // In code like this:
468 // type MyType = impl Copy;
469 // fn produce() -> MyType { true }
470 // fn bad_produce() -> MyType { panic!() }
473 // we want to unify the opaque inference variable in `bad_produce`
474 // with the diverging fallback for `panic!` (e.g. `()` or `!`).
475 // This will produce a nice error message about conflicting concrete
476 // types for `MyType`.
478 // If we had tried to fallback the opaque inference variable to `MyType`,
479 // we will generate a confusing type-check error that does not explicitly
480 // refer to opaque types.
481 fcx.select_obligations_where_possible(fallback_has_occurred, |_| {});
483 // We now run fallback again, but this time we allow it to replace
484 // unconstrained opaque type variables, in addition to performing
485 // other kinds of fallback.
486 for ty in &fcx.unsolved_variables() {
487 fallback_has_occurred |= fcx.fallback_if_possible(ty, FallbackMode::All);
490 // See if we can make any more progress.
491 fcx.select_obligations_where_possible(fallback_has_occurred, |_| {});
493 // Even though coercion casts provide type hints, we check casts after fallback for
494 // backwards compatibility. This makes fallback a stronger type hint than a cast coercion.
497 // Closure and generator analysis may run after fallback
498 // because they don't constrain other type variables.
499 fcx.closure_analyze(body);
500 assert!(fcx.deferred_call_resolutions.borrow().is_empty());
501 fcx.resolve_generator_interiors(def_id.to_def_id());
503 for (ty, span, code) in fcx.deferred_sized_obligations.borrow_mut().drain(..) {
504 let ty = fcx.normalize_ty(span, ty);
505 fcx.require_type_is_sized(ty, span, code);
508 fcx.select_all_obligations_or_error();
510 if fn_sig.is_some() {
511 fcx.regionck_fn(id, body);
513 fcx.regionck_expr(body);
516 fcx.resolve_type_vars_in_body(body)
519 // Consistency check our TypeckResults instance can hold all ItemLocalIds
520 // it will need to hold.
521 assert_eq!(typeck_results.hir_owner, id.owner);
526 /// When `check_fn` is invoked on a generator (i.e., a body that
527 /// includes yield), it returns back some information about the yield
529 struct GeneratorTypes<'tcx> {
530 /// Type of generator argument / values returned by `yield`.
533 /// Type of value that is yielded.
536 /// Types that are captured (see `GeneratorInterior` for more).
539 /// Indicates if the generator is movable or static (immovable).
540 movability: hir::Movability,
543 /// Given a `DefId` for an opaque type in return position, find its parent item's return
545 fn get_owner_return_paths(
548 ) -> Option<(hir::HirId, ReturnsVisitor<'tcx>)> {
549 let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
550 let id = tcx.hir().get_parent_item(hir_id);
554 .and_then(|(hir_id, node)| node.body_id().map(|b| (hir_id, b)))
555 .map(|(hir_id, body_id)| {
556 let body = tcx.hir().body(body_id);
557 let mut visitor = ReturnsVisitor::default();
558 visitor.visit_body(body);
563 // Forbid defining intrinsics in Rust code,
564 // as they must always be defined by the compiler.
565 fn fn_maybe_err(tcx: TyCtxt<'_>, sp: Span, abi: Abi) {
566 if let Abi::RustIntrinsic | Abi::PlatformIntrinsic = abi {
567 tcx.sess.span_err(sp, "intrinsic must be in `extern \"rust-intrinsic\" { ... }` block");
571 fn maybe_check_static_with_link_section(tcx: TyCtxt<'_>, id: LocalDefId, span: Span) {
572 // Only restricted on wasm32 target for now
573 if !tcx.sess.opts.target_triple.triple().starts_with("wasm32") {
577 // If `#[link_section]` is missing, then nothing to verify
578 let attrs = tcx.codegen_fn_attrs(id);
579 if attrs.link_section.is_none() {
583 // For the wasm32 target statics with `#[link_section]` are placed into custom
584 // sections of the final output file, but this isn't link custom sections of
585 // other executable formats. Namely we can only embed a list of bytes,
586 // nothing with pointers to anything else or relocations. If any relocation
587 // show up, reject them here.
588 // `#[link_section]` may contain arbitrary, or even undefined bytes, but it is
589 // the consumer's responsibility to ensure all bytes that have been read
590 // have defined values.
591 match tcx.eval_static_initializer(id.to_def_id()) {
593 if alloc.relocations().len() != 0 {
594 let msg = "statics with a custom `#[link_section]` must be a \
595 simple list of bytes on the wasm target with no \
596 extra levels of indirection such as references";
597 tcx.sess.span_err(span, msg);
604 fn report_forbidden_specialization(
606 impl_item: &hir::ImplItem<'_>,
609 let mut err = struct_span_err!(
613 "`{}` specializes an item from a parent `impl`, but \
614 that item is not marked `default`",
617 err.span_label(impl_item.span, format!("cannot specialize default item `{}`", impl_item.ident));
619 match tcx.span_of_impl(parent_impl) {
621 err.span_label(span, "parent `impl` is here");
623 "to specialize, `{}` in the parent `impl` must be marked `default`",
628 err.note(&format!("parent implementation is in crate `{}`", cname));
635 fn missing_items_err(
638 missing_items: &[ty::AssocItem],
639 full_impl_span: Span,
641 let missing_items_msg = missing_items
643 .map(|trait_item| trait_item.ident.to_string())
647 let mut err = struct_span_err!(
651 "not all trait items implemented, missing: `{}`",
654 err.span_label(impl_span, format!("missing `{}` in implementation", missing_items_msg));
656 // `Span` before impl block closing brace.
657 let hi = full_impl_span.hi() - BytePos(1);
658 // Point at the place right before the closing brace of the relevant `impl` to suggest
659 // adding the associated item at the end of its body.
660 let sugg_sp = full_impl_span.with_lo(hi).with_hi(hi);
661 // Obtain the level of indentation ending in `sugg_sp`.
662 let indentation = tcx.sess.source_map().span_to_margin(sugg_sp).unwrap_or(0);
663 // Make the whitespace that will make the suggestion have the right indentation.
664 let padding: String = " ".repeat(indentation);
666 for trait_item in missing_items {
667 let snippet = suggestion_signature(&trait_item, tcx);
668 let code = format!("{}{}\n{}", padding, snippet, padding);
669 let msg = format!("implement the missing item: `{}`", snippet);
670 let appl = Applicability::HasPlaceholders;
671 if let Some(span) = tcx.hir().span_if_local(trait_item.def_id) {
672 err.span_label(span, format!("`{}` from trait", trait_item.ident));
673 err.tool_only_span_suggestion(sugg_sp, &msg, code, appl);
675 err.span_suggestion_hidden(sugg_sp, &msg, code, appl);
681 /// Resugar `ty::GenericPredicates` in a way suitable to be used in structured suggestions.
682 fn bounds_from_generic_predicates<'tcx>(
684 predicates: ty::GenericPredicates<'tcx>,
685 ) -> (String, String) {
686 let mut types: FxHashMap<Ty<'tcx>, Vec<DefId>> = FxHashMap::default();
687 let mut projections = vec![];
688 for (predicate, _) in predicates.predicates {
689 debug!("predicate {:?}", predicate);
690 let bound_predicate = predicate.kind();
691 match bound_predicate.skip_binder() {
692 ty::PredicateKind::Trait(trait_predicate) => {
693 let entry = types.entry(trait_predicate.self_ty()).or_default();
694 let def_id = trait_predicate.def_id();
695 if Some(def_id) != tcx.lang_items().sized_trait() {
696 // Type params are `Sized` by default, do not add that restriction to the list
697 // if it is a positive requirement.
698 entry.push(trait_predicate.def_id());
701 ty::PredicateKind::Projection(projection_pred) => {
702 projections.push(bound_predicate.rebind(projection_pred));
707 let generics = if types.is_empty() {
714 .filter_map(|t| match t.kind() {
715 ty::Param(_) => Some(t.to_string()),
716 // Avoid suggesting the following:
717 // fn foo<T, <T as Trait>::Bar>(_: T) where T: Trait, <T as Trait>::Bar: Other {}
724 let mut where_clauses = vec![];
725 for (ty, bounds) in types {
726 for bound in &bounds {
727 where_clauses.push(format!("{}: {}", ty, tcx.def_path_str(*bound)));
730 for projection in &projections {
731 let p = projection.skip_binder();
732 // FIXME: this is not currently supported syntax, we should be looking at the `types` and
733 // insert the associated types where they correspond, but for now let's be "lazy" and
734 // propose this instead of the following valid resugaring:
735 // `T: Trait, Trait::Assoc = K` → `T: Trait<Assoc = K>`
736 where_clauses.push(format!("{} = {}", tcx.def_path_str(p.projection_ty.item_def_id), p.ty));
738 let where_clauses = if where_clauses.is_empty() {
741 format!(" where {}", where_clauses.join(", "))
743 (generics, where_clauses)
746 /// Return placeholder code for the given function.
747 fn fn_sig_suggestion<'tcx>(
749 sig: ty::FnSig<'tcx>,
751 predicates: ty::GenericPredicates<'tcx>,
752 assoc: &ty::AssocItem,
759 Some(match ty.kind() {
760 ty::Param(_) if assoc.fn_has_self_parameter && i == 0 => "self".to_string(),
761 ty::Ref(reg, ref_ty, mutability) if i == 0 => {
762 let reg = match &format!("{}", reg)[..] {
763 "'_" | "" => String::new(),
764 reg => format!("{} ", reg),
766 if assoc.fn_has_self_parameter {
767 match ref_ty.kind() {
768 ty::Param(param) if param.name == kw::SelfUpper => {
769 format!("&{}{}self", reg, mutability.prefix_str())
772 _ => format!("self: {}", ty),
779 if assoc.fn_has_self_parameter && i == 0 {
780 format!("self: {}", ty)
787 .chain(std::iter::once(if sig.c_variadic { Some("...".to_string()) } else { None }))
789 .collect::<Vec<String>>()
791 let output = sig.output();
792 let output = if !output.is_unit() { format!(" -> {}", output) } else { String::new() };
794 let unsafety = sig.unsafety.prefix_str();
795 let (generics, where_clauses) = bounds_from_generic_predicates(tcx, predicates);
797 // FIXME: this is not entirely correct, as the lifetimes from borrowed params will
798 // not be present in the `fn` definition, not will we account for renamed
799 // lifetimes between the `impl` and the `trait`, but this should be good enough to
800 // fill in a significant portion of the missing code, and other subsequent
801 // suggestions can help the user fix the code.
803 "{}fn {}{}({}){}{} {{ todo!() }}",
804 unsafety, ident, generics, args, output, where_clauses
808 /// Return placeholder code for the given associated item.
809 /// Similar to `ty::AssocItem::suggestion`, but appropriate for use as the code snippet of a
810 /// structured suggestion.
811 fn suggestion_signature(assoc: &ty::AssocItem, tcx: TyCtxt<'_>) -> String {
813 ty::AssocKind::Fn => {
814 // We skip the binder here because the binder would deanonymize all
815 // late-bound regions, and we don't want method signatures to show up
816 // `as for<'r> fn(&'r MyType)`. Pretty-printing handles late-bound
817 // regions just fine, showing `fn(&MyType)`.
820 tcx.fn_sig(assoc.def_id).skip_binder(),
822 tcx.predicates_of(assoc.def_id),
826 ty::AssocKind::Type => format!("type {} = Type;", assoc.ident),
827 ty::AssocKind::Const => {
828 let ty = tcx.type_of(assoc.def_id);
829 let val = expr::ty_kind_suggestion(ty).unwrap_or("value");
830 format!("const {}: {} = {};", assoc.ident, ty, val)
835 /// Emit an error when encountering two or more variants in a transparent enum.
836 fn bad_variant_count<'tcx>(tcx: TyCtxt<'tcx>, adt: &'tcx ty::AdtDef, sp: Span, did: DefId) {
837 let variant_spans: Vec<_> = adt
840 .map(|variant| tcx.hir().span_if_local(variant.def_id).unwrap())
842 let msg = format!("needs exactly one variant, but has {}", adt.variants.len(),);
843 let mut err = struct_span_err!(tcx.sess, sp, E0731, "transparent enum {}", msg);
844 err.span_label(sp, &msg);
845 if let [start @ .., end] = &*variant_spans {
846 for variant_span in start {
847 err.span_label(*variant_span, "");
849 err.span_label(*end, &format!("too many variants in `{}`", tcx.def_path_str(did)));
854 /// Emit an error when encountering two or more non-zero-sized fields in a transparent
856 fn bad_non_zero_sized_fields<'tcx>(
858 adt: &'tcx ty::AdtDef,
860 field_spans: impl Iterator<Item = Span>,
863 let msg = format!("needs at most one non-zero-sized field, but has {}", field_count);
864 let mut err = struct_span_err!(
868 "{}transparent {} {}",
869 if adt.is_enum() { "the variant of a " } else { "" },
873 err.span_label(sp, &msg);
874 for sp in field_spans {
875 err.span_label(sp, "this field is non-zero-sized");
880 fn report_unexpected_variant_res(tcx: TyCtxt<'_>, res: Res, span: Span) {
885 "expected unit struct, unit variant or constant, found {}{}",
889 .span_to_snippet(span)
890 .map_or_else(|_| String::new(), |s| format!(" `{}`", s)),
895 /// Controls whether the arguments are tupled. This is used for the call
898 /// Tupling means that all call-side arguments are packed into a tuple and
899 /// passed as a single parameter. For example, if tupling is enabled, this
902 /// fn f(x: (isize, isize))
904 /// Can be called as:
911 #[derive(Clone, Eq, PartialEq)]
912 enum TupleArgumentsFlag {
917 /// Controls how we perform fallback for unconstrained
920 /// Do not fallback type variables to opaque types.
922 /// Perform all possible kinds of fallback, including
923 /// turning type variables to opaque types.
927 /// A wrapper for `InferCtxt`'s `in_progress_typeck_results` field.
928 #[derive(Copy, Clone)]
929 struct MaybeInProgressTables<'a, 'tcx> {
930 maybe_typeck_results: Option<&'a RefCell<ty::TypeckResults<'tcx>>>,
933 impl<'a, 'tcx> MaybeInProgressTables<'a, 'tcx> {
934 fn borrow(self) -> Ref<'a, ty::TypeckResults<'tcx>> {
935 match self.maybe_typeck_results {
936 Some(typeck_results) => typeck_results.borrow(),
938 "MaybeInProgressTables: inh/fcx.typeck_results.borrow() with no typeck results"
943 fn borrow_mut(self) -> RefMut<'a, ty::TypeckResults<'tcx>> {
944 match self.maybe_typeck_results {
945 Some(typeck_results) => typeck_results.borrow_mut(),
947 "MaybeInProgressTables: inh/fcx.typeck_results.borrow_mut() with no typeck results"
953 struct CheckItemTypesVisitor<'tcx> {
957 impl ItemLikeVisitor<'tcx> for CheckItemTypesVisitor<'tcx> {
958 fn visit_item(&mut self, i: &'tcx hir::Item<'tcx>) {
959 check_item_type(self.tcx, i);
961 fn visit_trait_item(&mut self, _: &'tcx hir::TraitItem<'tcx>) {}
962 fn visit_impl_item(&mut self, _: &'tcx hir::ImplItem<'tcx>) {}
963 fn visit_foreign_item(&mut self, _: &'tcx hir::ForeignItem<'tcx>) {}
966 fn typeck_item_bodies(tcx: TyCtxt<'_>, (): ()) {
967 tcx.par_body_owners(|body_owner_def_id| {
968 tcx.ensure().typeck(body_owner_def_id);
972 fn fatally_break_rust(sess: &Session) {
973 let handler = sess.diagnostic();
974 handler.span_bug_no_panic(
976 "It looks like you're trying to break rust; would you like some ICE?",
978 handler.note_without_error("the compiler expectedly panicked. this is a feature.");
979 handler.note_without_error(
980 "we would appreciate a joke overview: \
981 https://github.com/rust-lang/rust/issues/43162#issuecomment-320764675",
983 handler.note_without_error(&format!(
984 "rustc {} running on {}",
985 option_env!("CFG_VERSION").unwrap_or("unknown_version"),
986 config::host_triple(),
990 fn potentially_plural_count(count: usize, word: &str) -> String {
991 format!("{} {}{}", count, word, pluralize!(count))
994 fn has_expected_num_generic_args<'tcx>(
996 trait_did: Option<DefId>,
999 trait_did.map_or(true, |trait_did| {
1000 let generics = tcx.generics_of(trait_did);
1001 generics.count() == expected + if generics.has_self { 1 } else { 0 }