1 // Copyright 2012-2015 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution and at
3 // http://rust-lang.org/COPYRIGHT.
5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8 // option. This file may not be copied, modified, or distributed
9 // except according to those terms.
15 Within the check phase of type check, we check each item one at a time
16 (bodies of function expressions are checked as part of the containing
17 function). Inference is used to supply types wherever they are
20 By far the most complex case is checking the body of a function. This
21 can be broken down into several distinct phases:
23 - gather: creates type variables to represent the type of each local
24 variable and pattern binding.
26 - main: the main pass does the lion's share of the work: it
27 determines the types of all expressions, resolves
28 methods, checks for most invalid conditions, and so forth. In
29 some cases, where a type is unknown, it may create a type or region
30 variable and use that as the type of an expression.
32 In the process of checking, various constraints will be placed on
33 these type variables through the subtyping relationships requested
34 through the `demand` module. The `infer` module is in charge
35 of resolving those constraints.
37 - regionck: after main is complete, the regionck pass goes over all
38 types looking for regions and making sure that they did not escape
39 into places they are not in scope. This may also influence the
40 final assignments of the various region variables if there is some
43 - vtable: find and records the impls to use for each trait bound that
44 appears on a type parameter.
46 - writeback: writes the final types within a function body, replacing
47 type variables with their final inferred types. These final types
48 are written into the `tcx.node_types` table, which should *never* contain
49 any reference to a type variable.
53 While type checking a function, the intermediate types for the
54 expressions, blocks, and so forth contained within the function are
55 stored in `fcx.node_types` and `fcx.node_substs`. These types
56 may contain unresolved type variables. After type checking is
57 complete, the functions in the writeback module are used to take the
58 types from this table, resolve them, and then write them into their
59 permanent home in the type context `tcx`.
61 This means that during inferencing you should use `fcx.write_ty()`
62 and `fcx.expr_ty()` / `fcx.node_ty()` to write/obtain the types of
63 nodes within the function.
65 The types of top-level items, which never contain unbound type
66 variables, are stored directly into the `tcx` tables.
68 n.b.: A type variable is not the same thing as a type parameter. A
69 type variable is rather an "instance" of a type parameter: that is,
70 given a generic function `fn foo<T>(t: T)`: while checking the
71 function `foo`, the type `ty_param(0)` refers to the type `T`, which
72 is treated in abstract. When `foo()` is called, however, `T` will be
73 substituted for a fresh type variable `N`. This variable will
74 eventually be resolved to some concrete type (which might itself be
79 pub use self::Expectation::*;
80 use self::autoderef::Autoderef;
81 use self::callee::DeferredCallResolution;
82 use self::coercion::{CoerceMany, DynamicCoerceMany};
83 pub use self::compare_method::{compare_impl_method, compare_const_impl};
84 use self::method::MethodCallee;
85 use self::TupleArgumentsFlag::*;
89 use hir::def_id::{CrateNum, DefId, LOCAL_CRATE};
91 use namespace::Namespace;
92 use rustc::infer::{self, InferCtxt, InferOk, RegionVariableOrigin};
93 use rustc::infer::anon_types::AnonTypeDecl;
94 use rustc::infer::type_variable::{TypeVariableOrigin};
95 use rustc::middle::region;
96 use rustc::mir::interpret::{GlobalId};
97 use rustc::ty::subst::{Kind, Subst, Substs};
98 use rustc::traits::{self, ObligationCause, ObligationCauseCode, TraitEngine};
99 use rustc::ty::{self, Ty, TyCtxt, Visibility, ToPredicate};
100 use rustc::ty::adjustment::{Adjust, Adjustment, AllowTwoPhase, AutoBorrow, AutoBorrowMutability};
101 use rustc::ty::fold::TypeFoldable;
102 use rustc::ty::maps::Providers;
103 use rustc::ty::util::{Representability, IntTypeExt, Discr};
104 use errors::{DiagnosticBuilder, DiagnosticId};
106 use require_c_abi_if_variadic;
107 use session::{CompileIncomplete, config, Session};
110 use util::common::{ErrorReported, indenter};
111 use util::nodemap::{DefIdMap, DefIdSet, FxHashMap, NodeMap};
113 use std::cell::{Cell, RefCell, Ref, RefMut};
114 use rustc_data_structures::sync::Lrc;
115 use std::collections::hash_map::Entry;
117 use std::fmt::Display;
118 use std::mem::replace;
120 use std::ops::{self, Deref};
121 use rustc_target::spec::abi::Abi;
124 use syntax::codemap::{original_sp, Spanned};
125 use syntax::feature_gate::{GateIssue, emit_feature_err};
127 use syntax::symbol::{Symbol, LocalInternedString, keywords};
128 use syntax::util::lev_distance::find_best_match_for_name;
129 use syntax_pos::{self, BytePos, Span, MultiSpan};
131 use rustc::hir::intravisit::{self, Visitor, NestedVisitorMap};
132 use rustc::hir::itemlikevisit::ItemLikeVisitor;
133 use rustc::hir::map::Node;
134 use rustc::hir::{self, PatKind};
135 use rustc::middle::lang_items;
151 mod generator_interior;
155 /// A wrapper for InferCtxt's `in_progress_tables` field.
156 #[derive(Copy, Clone)]
157 struct MaybeInProgressTables<'a, 'tcx: 'a> {
158 maybe_tables: Option<&'a RefCell<ty::TypeckTables<'tcx>>>,
161 impl<'a, 'tcx> MaybeInProgressTables<'a, 'tcx> {
162 fn borrow(self) -> Ref<'a, ty::TypeckTables<'tcx>> {
163 match self.maybe_tables {
164 Some(tables) => tables.borrow(),
166 bug!("MaybeInProgressTables: inh/fcx.tables.borrow() with no tables")
171 fn borrow_mut(self) -> RefMut<'a, ty::TypeckTables<'tcx>> {
172 match self.maybe_tables {
173 Some(tables) => tables.borrow_mut(),
175 bug!("MaybeInProgressTables: inh/fcx.tables.borrow_mut() with no tables")
182 /// closures defined within the function. For example:
185 /// bar(move|| { ... })
188 /// Here, the function `foo()` and the closure passed to
189 /// `bar()` will each have their own `FnCtxt`, but they will
190 /// share the inherited fields.
191 pub struct Inherited<'a, 'gcx: 'a+'tcx, 'tcx: 'a> {
192 infcx: InferCtxt<'a, 'gcx, 'tcx>,
194 tables: MaybeInProgressTables<'a, 'tcx>,
196 locals: RefCell<NodeMap<Ty<'tcx>>>,
198 fulfillment_cx: RefCell<Box<dyn TraitEngine<'tcx>>>,
200 // When we process a call like `c()` where `c` is a closure type,
201 // we may not have decided yet whether `c` is a `Fn`, `FnMut`, or
202 // `FnOnce` closure. In that case, we defer full resolution of the
203 // call until upvar inference can kick in and make the
204 // decision. We keep these deferred resolutions grouped by the
205 // def-id of the closure, so that once we decide, we can easily go
206 // back and process them.
207 deferred_call_resolutions: RefCell<DefIdMap<Vec<DeferredCallResolution<'gcx, 'tcx>>>>,
209 deferred_cast_checks: RefCell<Vec<cast::CastCheck<'tcx>>>,
211 deferred_generator_interiors: RefCell<Vec<(hir::BodyId, Ty<'tcx>)>>,
213 // Anonymized types found in explicit return types and their
214 // associated fresh inference variable. Writeback resolves these
215 // variables to get the concrete type, which can be used to
216 // deanonymize TyAnon, after typeck is done with all functions.
217 anon_types: RefCell<DefIdMap<AnonTypeDecl<'tcx>>>,
219 /// Each type parameter has an implicit region bound that
220 /// indicates it must outlive at least the function body (the user
221 /// may specify stronger requirements). This field indicates the
222 /// region of the callee. If it is `None`, then the parameter
223 /// environment is for an item or something where the "callee" is
225 implicit_region_bound: Option<ty::Region<'tcx>>,
227 body_id: Option<hir::BodyId>,
230 impl<'a, 'gcx, 'tcx> Deref for Inherited<'a, 'gcx, 'tcx> {
231 type Target = InferCtxt<'a, 'gcx, 'tcx>;
232 fn deref(&self) -> &Self::Target {
237 /// When type-checking an expression, we propagate downward
238 /// whatever type hint we are able in the form of an `Expectation`.
239 #[derive(Copy, Clone, Debug)]
240 pub enum Expectation<'tcx> {
241 /// We know nothing about what type this expression should have.
244 /// This expression is an `if` condition, it must resolve to `bool`.
247 /// This expression should have the type given (or some subtype)
248 ExpectHasType(Ty<'tcx>),
250 /// This expression will be cast to the `Ty`
251 ExpectCastableToType(Ty<'tcx>),
253 /// This rvalue expression will be wrapped in `&` or `Box` and coerced
254 /// to `&Ty` or `Box<Ty>`, respectively. `Ty` is `[A]` or `Trait`.
255 ExpectRvalueLikeUnsized(Ty<'tcx>),
258 impl<'a, 'gcx, 'tcx> Expectation<'tcx> {
259 // Disregard "castable to" expectations because they
260 // can lead us astray. Consider for example `if cond
261 // {22} else {c} as u8` -- if we propagate the
262 // "castable to u8" constraint to 22, it will pick the
263 // type 22u8, which is overly constrained (c might not
264 // be a u8). In effect, the problem is that the
265 // "castable to" expectation is not the tightest thing
266 // we can say, so we want to drop it in this case.
267 // The tightest thing we can say is "must unify with
268 // else branch". Note that in the case of a "has type"
269 // constraint, this limitation does not hold.
271 // If the expected type is just a type variable, then don't use
272 // an expected type. Otherwise, we might write parts of the type
273 // when checking the 'then' block which are incompatible with the
275 fn adjust_for_branches(&self, fcx: &FnCtxt<'a, 'gcx, 'tcx>) -> Expectation<'tcx> {
277 ExpectHasType(ety) => {
278 let ety = fcx.shallow_resolve(ety);
279 if !ety.is_ty_var() {
285 ExpectRvalueLikeUnsized(ety) => {
286 ExpectRvalueLikeUnsized(ety)
292 /// Provide an expectation for an rvalue expression given an *optional*
293 /// hint, which is not required for type safety (the resulting type might
294 /// be checked higher up, as is the case with `&expr` and `box expr`), but
295 /// is useful in determining the concrete type.
297 /// The primary use case is where the expected type is a fat pointer,
298 /// like `&[isize]`. For example, consider the following statement:
300 /// let x: &[isize] = &[1, 2, 3];
302 /// In this case, the expected type for the `&[1, 2, 3]` expression is
303 /// `&[isize]`. If however we were to say that `[1, 2, 3]` has the
304 /// expectation `ExpectHasType([isize])`, that would be too strong --
305 /// `[1, 2, 3]` does not have the type `[isize]` but rather `[isize; 3]`.
306 /// It is only the `&[1, 2, 3]` expression as a whole that can be coerced
307 /// to the type `&[isize]`. Therefore, we propagate this more limited hint,
308 /// which still is useful, because it informs integer literals and the like.
309 /// See the test case `test/run-pass/coerce-expect-unsized.rs` and #20169
310 /// for examples of where this comes up,.
311 fn rvalue_hint(fcx: &FnCtxt<'a, 'gcx, 'tcx>, ty: Ty<'tcx>) -> Expectation<'tcx> {
312 match fcx.tcx.struct_tail(ty).sty {
313 ty::TySlice(_) | ty::TyStr | ty::TyDynamic(..) => {
314 ExpectRvalueLikeUnsized(ty)
316 _ => ExpectHasType(ty)
320 // Resolves `expected` by a single level if it is a variable. If
321 // there is no expected type or resolution is not possible (e.g.,
322 // no constraints yet present), just returns `None`.
323 fn resolve(self, fcx: &FnCtxt<'a, 'gcx, 'tcx>) -> Expectation<'tcx> {
325 NoExpectation => NoExpectation,
326 ExpectIfCondition => ExpectIfCondition,
327 ExpectCastableToType(t) => {
328 ExpectCastableToType(fcx.resolve_type_vars_if_possible(&t))
330 ExpectHasType(t) => {
331 ExpectHasType(fcx.resolve_type_vars_if_possible(&t))
333 ExpectRvalueLikeUnsized(t) => {
334 ExpectRvalueLikeUnsized(fcx.resolve_type_vars_if_possible(&t))
339 fn to_option(self, fcx: &FnCtxt<'a, 'gcx, 'tcx>) -> Option<Ty<'tcx>> {
340 match self.resolve(fcx) {
341 NoExpectation => None,
342 ExpectIfCondition => Some(fcx.tcx.types.bool),
343 ExpectCastableToType(ty) |
345 ExpectRvalueLikeUnsized(ty) => Some(ty),
349 /// It sometimes happens that we want to turn an expectation into
350 /// a **hard constraint** (i.e., something that must be satisfied
351 /// for the program to type-check). `only_has_type` will return
352 /// such a constraint, if it exists.
353 fn only_has_type(self, fcx: &FnCtxt<'a, 'gcx, 'tcx>) -> Option<Ty<'tcx>> {
354 match self.resolve(fcx) {
355 ExpectHasType(ty) => Some(ty),
356 ExpectIfCondition => Some(fcx.tcx.types.bool),
357 NoExpectation | ExpectCastableToType(_) | ExpectRvalueLikeUnsized(_) => None,
361 /// Like `only_has_type`, but instead of returning `None` if no
362 /// hard constraint exists, creates a fresh type variable.
363 fn coercion_target_type(self, fcx: &FnCtxt<'a, 'gcx, 'tcx>, span: Span) -> Ty<'tcx> {
364 self.only_has_type(fcx)
365 .unwrap_or_else(|| fcx.next_ty_var(TypeVariableOrigin::MiscVariable(span)))
369 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
376 fn maybe_mut_place(m: hir::Mutability) -> Self {
378 hir::MutMutable => Needs::MutPlace,
379 hir::MutImmutable => Needs::None,
384 #[derive(Copy, Clone)]
385 pub struct UnsafetyState {
386 pub def: ast::NodeId,
387 pub unsafety: hir::Unsafety,
388 pub unsafe_push_count: u32,
393 pub fn function(unsafety: hir::Unsafety, def: ast::NodeId) -> UnsafetyState {
394 UnsafetyState { def: def, unsafety: unsafety, unsafe_push_count: 0, from_fn: true }
397 pub fn recurse(&mut self, blk: &hir::Block) -> UnsafetyState {
398 match self.unsafety {
399 // If this unsafe, then if the outer function was already marked as
400 // unsafe we shouldn't attribute the unsafe'ness to the block. This
401 // way the block can be warned about instead of ignoring this
402 // extraneous block (functions are never warned about).
403 hir::Unsafety::Unsafe if self.from_fn => *self,
406 let (unsafety, def, count) = match blk.rules {
407 hir::PushUnsafeBlock(..) =>
408 (unsafety, blk.id, self.unsafe_push_count.checked_add(1).unwrap()),
409 hir::PopUnsafeBlock(..) =>
410 (unsafety, blk.id, self.unsafe_push_count.checked_sub(1).unwrap()),
411 hir::UnsafeBlock(..) =>
412 (hir::Unsafety::Unsafe, blk.id, self.unsafe_push_count),
414 (unsafety, self.def, self.unsafe_push_count),
418 unsafe_push_count: count,
425 #[derive(Debug, Copy, Clone)]
431 /// Tracks whether executing a node may exit normally (versus
432 /// return/break/panic, which "diverge", leaving dead code in their
433 /// wake). Tracked semi-automatically (through type variables marked
434 /// as diverging), with some manual adjustments for control-flow
435 /// primitives (approximating a CFG).
436 #[derive(Copy, Clone, Debug, PartialEq, Eq, PartialOrd, Ord)]
438 /// Potentially unknown, some cases converge,
439 /// others require a CFG to determine them.
442 /// Definitely known to diverge and therefore
443 /// not reach the next sibling or its parent.
446 /// Same as `Always` but with a reachability
447 /// warning already emitted
451 // Convenience impls for combinig `Diverges`.
453 impl ops::BitAnd for Diverges {
455 fn bitand(self, other: Self) -> Self {
456 cmp::min(self, other)
460 impl ops::BitOr for Diverges {
462 fn bitor(self, other: Self) -> Self {
463 cmp::max(self, other)
467 impl ops::BitAndAssign for Diverges {
468 fn bitand_assign(&mut self, other: Self) {
469 *self = *self & other;
473 impl ops::BitOrAssign for Diverges {
474 fn bitor_assign(&mut self, other: Self) {
475 *self = *self | other;
480 fn always(self) -> bool {
481 self >= Diverges::Always
485 pub struct BreakableCtxt<'gcx: 'tcx, 'tcx> {
488 // this is `null` for loops where break with a value is illegal,
489 // such as `while`, `for`, and `while let`
490 coerce: Option<DynamicCoerceMany<'gcx, 'tcx>>,
493 pub struct EnclosingBreakables<'gcx: 'tcx, 'tcx> {
494 stack: Vec<BreakableCtxt<'gcx, 'tcx>>,
495 by_id: NodeMap<usize>,
498 impl<'gcx, 'tcx> EnclosingBreakables<'gcx, 'tcx> {
499 fn find_breakable(&mut self, target_id: ast::NodeId) -> &mut BreakableCtxt<'gcx, 'tcx> {
500 let ix = *self.by_id.get(&target_id).unwrap_or_else(|| {
501 bug!("could not find enclosing breakable with id {}", target_id);
507 pub struct FnCtxt<'a, 'gcx: 'a+'tcx, 'tcx: 'a> {
508 body_id: ast::NodeId,
510 /// The parameter environment used for proving trait obligations
511 /// in this function. This can change when we descend into
512 /// closures (as they bring new things into scope), hence it is
513 /// not part of `Inherited` (as of the time of this writing,
514 /// closures do not yet change the environment, but they will
516 param_env: ty::ParamEnv<'tcx>,
518 // Number of errors that had been reported when we started
519 // checking this function. On exit, if we find that *more* errors
520 // have been reported, we will skip regionck and other work that
521 // expects the types within the function to be consistent.
522 err_count_on_creation: usize,
524 ret_coercion: Option<RefCell<DynamicCoerceMany<'gcx, 'tcx>>>,
526 yield_ty: Option<Ty<'tcx>>,
528 ps: RefCell<UnsafetyState>,
530 /// Whether the last checked node generates a divergence (e.g.,
531 /// `return` will set this to Always). In general, when entering
532 /// an expression or other node in the tree, the initial value
533 /// indicates whether prior parts of the containing expression may
534 /// have diverged. It is then typically set to `Maybe` (and the
535 /// old value remembered) for processing the subparts of the
536 /// current expression. As each subpart is processed, they may set
537 /// the flag to `Always` etc. Finally, at the end, we take the
538 /// result and "union" it with the original value, so that when we
539 /// return the flag indicates if any subpart of the the parent
540 /// expression (up to and including this part) has diverged. So,
541 /// if you read it after evaluating a subexpression `X`, the value
542 /// you get indicates whether any subexpression that was
543 /// evaluating up to and including `X` diverged.
545 /// We use this flag for two purposes:
547 /// - To warn about unreachable code: if, after processing a
548 /// sub-expression but before we have applied the effects of the
549 /// current node, we see that the flag is set to `Always`, we
550 /// can issue a warning. This corresponds to something like
551 /// `foo(return)`; we warn on the `foo()` expression. (We then
552 /// update the flag to `WarnedAlways` to suppress duplicate
553 /// reports.) Similarly, if we traverse to a fresh statement (or
554 /// tail expression) from a `Always` setting, we will issue a
555 /// warning. This corresponds to something like `{return;
556 /// foo();}` or `{return; 22}`, where we would warn on the
559 /// - To permit assignment into a local variable or other place
560 /// (including the "return slot") of type `!`. This is allowed
561 /// if **either** the type of value being assigned is `!`, which
562 /// means the current code is dead, **or** the expression's
563 /// diverging flag is true, which means that a diverging value was
564 /// wrapped (e.g., `let x: ! = foo(return)`).
566 /// To repeat the last point: an expression represents dead-code
567 /// if, after checking it, **either** its type is `!` OR the
568 /// diverges flag is set to something other than `Maybe`.
569 diverges: Cell<Diverges>,
571 /// Whether any child nodes have any type errors.
572 has_errors: Cell<bool>,
574 enclosing_breakables: RefCell<EnclosingBreakables<'gcx, 'tcx>>,
576 inh: &'a Inherited<'a, 'gcx, 'tcx>,
579 impl<'a, 'gcx, 'tcx> Deref for FnCtxt<'a, 'gcx, 'tcx> {
580 type Target = Inherited<'a, 'gcx, 'tcx>;
581 fn deref(&self) -> &Self::Target {
586 /// Helper type of a temporary returned by Inherited::build(...).
587 /// Necessary because we can't write the following bound:
588 /// F: for<'b, 'tcx> where 'gcx: 'tcx FnOnce(Inherited<'b, 'gcx, 'tcx>).
589 pub struct InheritedBuilder<'a, 'gcx: 'a+'tcx, 'tcx: 'a> {
590 infcx: infer::InferCtxtBuilder<'a, 'gcx, 'tcx>,
594 impl<'a, 'gcx, 'tcx> Inherited<'a, 'gcx, 'tcx> {
595 pub fn build(tcx: TyCtxt<'a, 'gcx, 'gcx>, def_id: DefId)
596 -> InheritedBuilder<'a, 'gcx, 'tcx> {
597 let hir_id_root = if def_id.is_local() {
598 let node_id = tcx.hir.as_local_node_id(def_id).unwrap();
599 let hir_id = tcx.hir.definitions().node_to_hir_id(node_id);
600 DefId::local(hir_id.owner)
606 infcx: tcx.infer_ctxt().with_fresh_in_progress_tables(hir_id_root),
612 impl<'a, 'gcx, 'tcx> InheritedBuilder<'a, 'gcx, 'tcx> {
613 fn enter<F, R>(&'tcx mut self, f: F) -> R
614 where F: for<'b> FnOnce(Inherited<'b, 'gcx, 'tcx>) -> R
616 let def_id = self.def_id;
617 self.infcx.enter(|infcx| f(Inherited::new(infcx, def_id)))
621 impl<'a, 'gcx, 'tcx> Inherited<'a, 'gcx, 'tcx> {
622 fn new(infcx: InferCtxt<'a, 'gcx, 'tcx>, def_id: DefId) -> Self {
624 let item_id = tcx.hir.as_local_node_id(def_id);
625 let body_id = item_id.and_then(|id| tcx.hir.maybe_body_owned_by(id));
626 let implicit_region_bound = body_id.map(|body_id| {
627 let body = tcx.hir.body(body_id);
628 tcx.mk_region(ty::ReScope(region::Scope::CallSite(body.value.hir_id.local_id)))
632 tables: MaybeInProgressTables {
633 maybe_tables: infcx.in_progress_tables,
636 fulfillment_cx: RefCell::new(TraitEngine::new(tcx)),
637 locals: RefCell::new(NodeMap()),
638 deferred_call_resolutions: RefCell::new(DefIdMap()),
639 deferred_cast_checks: RefCell::new(Vec::new()),
640 deferred_generator_interiors: RefCell::new(Vec::new()),
641 anon_types: RefCell::new(DefIdMap()),
642 implicit_region_bound,
647 fn register_predicate(&self, obligation: traits::PredicateObligation<'tcx>) {
648 debug!("register_predicate({:?})", obligation);
649 if obligation.has_escaping_regions() {
650 span_bug!(obligation.cause.span, "escaping regions in predicate {:?}",
655 .register_predicate_obligation(self, obligation);
658 fn register_predicates<I>(&self, obligations: I)
659 where I: IntoIterator<Item = traits::PredicateObligation<'tcx>> {
660 for obligation in obligations {
661 self.register_predicate(obligation);
665 fn register_infer_ok_obligations<T>(&self, infer_ok: InferOk<'tcx, T>) -> T {
666 self.register_predicates(infer_ok.obligations);
670 fn normalize_associated_types_in<T>(&self,
672 body_id: ast::NodeId,
673 param_env: ty::ParamEnv<'tcx>,
675 where T : TypeFoldable<'tcx>
677 let ok = self.partially_normalize_associated_types_in(span, body_id, param_env, value);
678 self.register_infer_ok_obligations(ok)
682 struct CheckItemTypesVisitor<'a, 'tcx: 'a> { tcx: TyCtxt<'a, 'tcx, 'tcx> }
684 impl<'a, 'tcx> ItemLikeVisitor<'tcx> for CheckItemTypesVisitor<'a, 'tcx> {
685 fn visit_item(&mut self, i: &'tcx hir::Item) {
686 check_item_type(self.tcx, i);
688 fn visit_trait_item(&mut self, _: &'tcx hir::TraitItem) { }
689 fn visit_impl_item(&mut self, _: &'tcx hir::ImplItem) { }
692 pub fn check_wf_new<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>) -> Result<(), ErrorReported> {
693 tcx.sess.track_errors(|| {
694 let mut visit = wfcheck::CheckTypeWellFormedVisitor::new(tcx);
695 tcx.hir.krate().visit_all_item_likes(&mut visit.as_deep_visitor());
699 pub fn check_item_types<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>) -> Result<(), ErrorReported> {
700 tcx.sess.track_errors(|| {
701 tcx.hir.krate().visit_all_item_likes(&mut CheckItemTypesVisitor { tcx });
705 pub fn check_item_bodies<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>) -> Result<(), CompileIncomplete> {
706 tcx.typeck_item_bodies(LOCAL_CRATE)
709 fn typeck_item_bodies<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, crate_num: CrateNum)
710 -> Result<(), CompileIncomplete>
712 debug_assert!(crate_num == LOCAL_CRATE);
713 Ok(tcx.sess.track_errors(|| {
714 for body_owner_def_id in tcx.body_owners() {
715 ty::maps::queries::typeck_tables_of::ensure(tcx, body_owner_def_id);
720 fn check_item_well_formed<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, def_id: DefId) {
721 wfcheck::check_item_well_formed(tcx, def_id);
724 fn check_trait_item_well_formed<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, def_id: DefId) {
725 wfcheck::check_trait_item(tcx, def_id);
728 fn check_impl_item_well_formed<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, def_id: DefId) {
729 wfcheck::check_impl_item(tcx, def_id);
732 pub fn provide(providers: &mut Providers) {
733 method::provide(providers);
734 *providers = Providers {
740 check_item_well_formed,
741 check_trait_item_well_formed,
742 check_impl_item_well_formed,
747 fn adt_destructor<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
749 -> Option<ty::Destructor> {
750 tcx.calculate_dtor(def_id, &mut dropck::check_drop_impl)
753 /// If this def-id is a "primary tables entry", returns `Some((body_id, decl))`
754 /// with information about it's body-id and fn-decl (if any). Otherwise,
757 /// If this function returns "some", then `typeck_tables(def_id)` will
758 /// succeed; if it returns `None`, then `typeck_tables(def_id)` may or
759 /// may not succeed. In some cases where this function returns `None`
760 /// (notably closures), `typeck_tables(def_id)` would wind up
761 /// redirecting to the owning function.
762 fn primary_body_of<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
764 -> Option<(hir::BodyId, Option<&'tcx hir::FnDecl>)>
766 match tcx.hir.get(id) {
767 hir::map::NodeItem(item) => {
769 hir::ItemConst(_, body) |
770 hir::ItemStatic(_, _, body) =>
772 hir::ItemFn(ref decl, .., body) =>
773 Some((body, Some(decl))),
778 hir::map::NodeTraitItem(item) => {
780 hir::TraitItemKind::Const(_, Some(body)) =>
782 hir::TraitItemKind::Method(ref sig, hir::TraitMethod::Provided(body)) =>
783 Some((body, Some(&sig.decl))),
788 hir::map::NodeImplItem(item) => {
790 hir::ImplItemKind::Const(_, body) =>
792 hir::ImplItemKind::Method(ref sig, body) =>
793 Some((body, Some(&sig.decl))),
798 hir::map::NodeExpr(expr) => {
799 // FIXME(eddyb) Closures should have separate
800 // function definition IDs and expression IDs.
801 // Type-checking should not let closures get
802 // this far in a constant position.
803 // Assume that everything other than closures
804 // is a constant "initializer" expression.
806 hir::ExprClosure(..) =>
809 Some((hir::BodyId { node_id: expr.id }, None)),
816 fn has_typeck_tables<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
819 // Closures' tables come from their outermost function,
820 // as they are part of the same "inference environment".
821 let outer_def_id = tcx.closure_base_def_id(def_id);
822 if outer_def_id != def_id {
823 return tcx.has_typeck_tables(outer_def_id);
826 let id = tcx.hir.as_local_node_id(def_id).unwrap();
827 primary_body_of(tcx, id).is_some()
830 fn used_trait_imports<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
833 tcx.typeck_tables_of(def_id).used_trait_imports.clone()
836 fn typeck_tables_of<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
838 -> &'tcx ty::TypeckTables<'tcx> {
839 // Closures' tables come from their outermost function,
840 // as they are part of the same "inference environment".
841 let outer_def_id = tcx.closure_base_def_id(def_id);
842 if outer_def_id != def_id {
843 return tcx.typeck_tables_of(outer_def_id);
846 let id = tcx.hir.as_local_node_id(def_id).unwrap();
847 let span = tcx.hir.span(id);
849 // Figure out what primary body this item has.
850 let (body_id, fn_decl) = primary_body_of(tcx, id).unwrap_or_else(|| {
851 span_bug!(span, "can't type-check body of {:?}", def_id);
853 let body = tcx.hir.body(body_id);
855 let tables = Inherited::build(tcx, def_id).enter(|inh| {
856 let param_env = tcx.param_env(def_id);
857 let fcx = if let Some(decl) = fn_decl {
858 let fn_sig = tcx.fn_sig(def_id);
860 check_abi(tcx, span, fn_sig.abi());
862 // Compute the fty from point of view of inside fn.
864 tcx.liberate_late_bound_regions(def_id, &fn_sig);
866 inh.normalize_associated_types_in(body.value.span,
871 let fcx = check_fn(&inh, param_env, fn_sig, decl, id, body, None).0;
874 let fcx = FnCtxt::new(&inh, param_env, body.value.id);
875 let expected_type = tcx.type_of(def_id);
876 let expected_type = fcx.normalize_associated_types_in(body.value.span, &expected_type);
877 fcx.require_type_is_sized(expected_type, body.value.span, traits::ConstSized);
879 // Gather locals in statics (because of block expressions).
880 // This is technically unnecessary because locals in static items are forbidden,
881 // but prevents type checking from blowing up before const checking can properly
883 GatherLocalsVisitor { fcx: &fcx }.visit_body(body);
885 fcx.check_expr_coercable_to_type(&body.value, expected_type);
890 // All type checking constraints were added, try to fallback unsolved variables.
891 fcx.select_obligations_where_possible(false);
892 let mut fallback_has_occurred = false;
893 for ty in &fcx.unsolved_variables() {
894 fallback_has_occurred |= fcx.fallback_if_possible(ty);
896 fcx.select_obligations_where_possible(fallback_has_occurred);
898 // Even though coercion casts provide type hints, we check casts after fallback for
899 // backwards compatibility. This makes fallback a stronger type hint than a cast coercion.
902 // Closure and generater analysis may run after fallback
903 // because they don't constrain other type variables.
904 fcx.closure_analyze(body);
905 assert!(fcx.deferred_call_resolutions.borrow().is_empty());
906 fcx.resolve_generator_interiors(def_id);
907 fcx.select_all_obligations_or_error();
909 if fn_decl.is_some() {
910 fcx.regionck_fn(id, body);
912 fcx.regionck_expr(body);
915 fcx.resolve_type_vars_in_body(body)
918 // Consistency check our TypeckTables instance can hold all ItemLocalIds
919 // it will need to hold.
920 assert_eq!(tables.local_id_root,
921 Some(DefId::local(tcx.hir.definitions().node_to_hir_id(id).owner)));
925 fn check_abi<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, span: Span, abi: Abi) {
926 if !tcx.sess.target.target.is_abi_supported(abi) {
927 struct_span_err!(tcx.sess, span, E0570,
928 "The ABI `{}` is not supported for the current target", abi).emit()
932 struct GatherLocalsVisitor<'a, 'gcx: 'a+'tcx, 'tcx: 'a> {
933 fcx: &'a FnCtxt<'a, 'gcx, 'tcx>
936 impl<'a, 'gcx, 'tcx> GatherLocalsVisitor<'a, 'gcx, 'tcx> {
937 fn assign(&mut self, span: Span, nid: ast::NodeId, ty_opt: Option<Ty<'tcx>>) -> Ty<'tcx> {
940 // infer the variable's type
941 let var_ty = self.fcx.next_ty_var(TypeVariableOrigin::TypeInference(span));
942 self.fcx.locals.borrow_mut().insert(nid, var_ty);
946 // take type that the user specified
947 self.fcx.locals.borrow_mut().insert(nid, typ);
954 impl<'a, 'gcx, 'tcx> Visitor<'gcx> for GatherLocalsVisitor<'a, 'gcx, 'tcx> {
955 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'gcx> {
956 NestedVisitorMap::None
959 // Add explicitly-declared locals.
960 fn visit_local(&mut self, local: &'gcx hir::Local) {
961 let o_ty = match local.ty {
963 let o_ty = self.fcx.to_ty(&ty);
965 let (c_ty, _orig_values) = self.fcx.inh.infcx.canonicalize_response(&o_ty);
966 debug!("visit_local: ty.hir_id={:?} o_ty={:?} c_ty={:?}", ty.hir_id, o_ty, c_ty);
967 self.fcx.tables.borrow_mut().user_provided_tys_mut().insert(ty.hir_id, c_ty);
973 self.assign(local.span, local.id, o_ty);
975 debug!("Local variable {:?} is assigned type {}",
977 self.fcx.ty_to_string(
978 self.fcx.locals.borrow().get(&local.id).unwrap().clone()));
979 intravisit::walk_local(self, local);
982 // Add pattern bindings.
983 fn visit_pat(&mut self, p: &'gcx hir::Pat) {
984 if let PatKind::Binding(_, _, ref path1, _) = p.node {
985 let var_ty = self.assign(p.span, p.id, None);
987 self.fcx.require_type_is_sized(var_ty, p.span,
988 traits::VariableType(p.id));
990 debug!("Pattern binding {} is assigned to {} with type {:?}",
992 self.fcx.ty_to_string(
993 self.fcx.locals.borrow().get(&p.id).unwrap().clone()),
996 intravisit::walk_pat(self, p);
999 // Don't descend into the bodies of nested closures
1000 fn visit_fn(&mut self, _: intravisit::FnKind<'gcx>, _: &'gcx hir::FnDecl,
1001 _: hir::BodyId, _: Span, _: ast::NodeId) { }
1004 /// When `check_fn` is invoked on a generator (i.e., a body that
1005 /// includes yield), it returns back some information about the yield
1007 struct GeneratorTypes<'tcx> {
1008 /// Type of value that is yielded.
1009 yield_ty: ty::Ty<'tcx>,
1011 /// Types that are captured (see `GeneratorInterior` for more).
1012 interior: ty::Ty<'tcx>,
1014 /// Indicates if the generator is movable or static (immovable)
1015 movability: hir::GeneratorMovability,
1018 /// Helper used for fns and closures. Does the grungy work of checking a function
1019 /// body and returns the function context used for that purpose, since in the case of a fn item
1020 /// there is still a bit more to do.
1023 /// * inherited: other fields inherited from the enclosing fn (if any)
1024 fn check_fn<'a, 'gcx, 'tcx>(inherited: &'a Inherited<'a, 'gcx, 'tcx>,
1025 param_env: ty::ParamEnv<'tcx>,
1026 fn_sig: ty::FnSig<'tcx>,
1027 decl: &'gcx hir::FnDecl,
1029 body: &'gcx hir::Body,
1030 can_be_generator: Option<hir::GeneratorMovability>)
1031 -> (FnCtxt<'a, 'gcx, 'tcx>, Option<GeneratorTypes<'tcx>>)
1033 let mut fn_sig = fn_sig.clone();
1035 debug!("check_fn(sig={:?}, fn_id={}, param_env={:?})", fn_sig, fn_id, param_env);
1037 // Create the function context. This is either derived from scratch or,
1038 // in the case of function expressions, based on the outer context.
1039 let mut fcx = FnCtxt::new(inherited, param_env, body.value.id);
1040 *fcx.ps.borrow_mut() = UnsafetyState::function(fn_sig.unsafety, fn_id);
1042 let ret_ty = fn_sig.output();
1043 fcx.require_type_is_sized(ret_ty, decl.output.span(), traits::SizedReturnType);
1044 let ret_ty = fcx.instantiate_anon_types_from_return_value(fn_id, &ret_ty);
1045 fcx.ret_coercion = Some(RefCell::new(CoerceMany::new(ret_ty)));
1046 fn_sig = fcx.tcx.mk_fn_sig(
1047 fn_sig.inputs().iter().cloned(),
1054 let span = body.value.span;
1056 if body.is_generator && can_be_generator.is_some() {
1057 let yield_ty = fcx.next_ty_var(TypeVariableOrigin::TypeInference(span));
1058 fcx.require_type_is_sized(yield_ty, span, traits::SizedYieldType);
1059 fcx.yield_ty = Some(yield_ty);
1062 GatherLocalsVisitor { fcx: &fcx, }.visit_body(body);
1064 // Add formal parameters.
1065 for (arg_ty, arg) in fn_sig.inputs().iter().zip(&body.arguments) {
1066 // Check the pattern.
1067 fcx.check_pat_walk(&arg.pat, arg_ty,
1068 ty::BindingMode::BindByValue(hir::Mutability::MutImmutable), true);
1070 // Check that argument is Sized.
1071 // The check for a non-trivial pattern is a hack to avoid duplicate warnings
1072 // for simple cases like `fn foo(x: Trait)`,
1073 // where we would error once on the parameter as a whole, and once on the binding `x`.
1074 if arg.pat.simple_name().is_none() {
1075 fcx.require_type_is_sized(arg_ty, decl.output.span(), traits::MiscObligation);
1078 fcx.write_ty(arg.hir_id, arg_ty);
1081 let fn_hir_id = fcx.tcx.hir.node_to_hir_id(fn_id);
1082 inherited.tables.borrow_mut().liberated_fn_sigs_mut().insert(fn_hir_id, fn_sig);
1084 fcx.check_return_expr(&body.value);
1086 // We insert the deferred_generator_interiors entry after visiting the body.
1087 // This ensures that all nested generators appear before the entry of this generator.
1088 // resolve_generator_interiors relies on this property.
1089 let gen_ty = if can_be_generator.is_some() && body.is_generator {
1090 let interior = fcx.next_ty_var(TypeVariableOrigin::MiscVariable(span));
1091 fcx.deferred_generator_interiors.borrow_mut().push((body.id(), interior));
1092 Some(GeneratorTypes {
1093 yield_ty: fcx.yield_ty.unwrap(),
1095 movability: can_be_generator.unwrap(),
1101 // Finalize the return check by taking the LUB of the return types
1102 // we saw and assigning it to the expected return type. This isn't
1103 // really expected to fail, since the coercions would have failed
1104 // earlier when trying to find a LUB.
1106 // However, the behavior around `!` is sort of complex. In the
1107 // event that the `actual_return_ty` comes back as `!`, that
1108 // indicates that the fn either does not return or "returns" only
1109 // values of type `!`. In this case, if there is an expected
1110 // return type that is *not* `!`, that should be ok. But if the
1111 // return type is being inferred, we want to "fallback" to `!`:
1113 // let x = move || panic!();
1115 // To allow for that, I am creating a type variable with diverging
1116 // fallback. This was deemed ever so slightly better than unifying
1117 // the return value with `!` because it allows for the caller to
1118 // make more assumptions about the return type (e.g., they could do
1120 // let y: Option<u32> = Some(x());
1122 // which would then cause this return type to become `u32`, not
1124 let coercion = fcx.ret_coercion.take().unwrap().into_inner();
1125 let mut actual_return_ty = coercion.complete(&fcx);
1126 if actual_return_ty.is_never() {
1127 actual_return_ty = fcx.next_diverging_ty_var(
1128 TypeVariableOrigin::DivergingFn(span));
1130 fcx.demand_suptype(span, ret_ty, actual_return_ty);
1132 // Check that the main return type implements the termination trait.
1133 if let Some(term_id) = fcx.tcx.lang_items().termination() {
1134 if let Some((id, _, entry_type)) = *fcx.tcx.sess.entry_fn.borrow() {
1137 config::EntryMain => {
1138 let substs = fcx.tcx.mk_substs(iter::once(Kind::from(ret_ty)));
1139 let trait_ref = ty::TraitRef::new(term_id, substs);
1140 let return_ty_span = decl.output.span();
1141 let cause = traits::ObligationCause::new(
1142 return_ty_span, fn_id, ObligationCauseCode::MainFunctionType);
1144 inherited.register_predicate(
1145 traits::Obligation::new(
1146 cause, param_env, trait_ref.to_predicate()));
1148 config::EntryStart => {},
1157 fn check_struct<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
1160 let def_id = tcx.hir.local_def_id(id);
1161 let def = tcx.adt_def(def_id);
1162 def.destructor(tcx); // force the destructor to be evaluated
1163 check_representable(tcx, span, def_id);
1165 if def.repr.simd() {
1166 check_simd(tcx, span, def_id);
1169 check_transparent(tcx, span, def_id);
1170 check_packed(tcx, span, def_id);
1173 fn check_union<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
1176 let def_id = tcx.hir.local_def_id(id);
1177 let def = tcx.adt_def(def_id);
1178 def.destructor(tcx); // force the destructor to be evaluated
1179 check_representable(tcx, span, def_id);
1181 check_packed(tcx, span, def_id);
1184 pub fn check_item_type<'a,'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, it: &'tcx hir::Item) {
1185 debug!("check_item_type(it.id={}, it.name={})",
1187 tcx.item_path_str(tcx.hir.local_def_id(it.id)));
1188 let _indenter = indenter();
1190 // Consts can play a role in type-checking, so they are included here.
1191 hir::ItemStatic(..) => {
1192 tcx.typeck_tables_of(tcx.hir.local_def_id(it.id));
1194 hir::ItemConst(..) => {
1195 tcx.typeck_tables_of(tcx.hir.local_def_id(it.id));
1196 if it.attrs.iter().any(|a| a.check_name("wasm_custom_section")) {
1197 let def_id = tcx.hir.local_def_id(it.id);
1198 check_const_is_u8_array(tcx, def_id, it.span);
1201 hir::ItemEnum(ref enum_definition, _) => {
1204 &enum_definition.variants,
1207 hir::ItemFn(..) => {} // entirely within check_item_body
1208 hir::ItemImpl(.., ref impl_item_refs) => {
1209 debug!("ItemImpl {} with id {}", it.name, it.id);
1210 let impl_def_id = tcx.hir.local_def_id(it.id);
1211 if let Some(impl_trait_ref) = tcx.impl_trait_ref(impl_def_id) {
1212 check_impl_items_against_trait(tcx,
1217 let trait_def_id = impl_trait_ref.def_id;
1218 check_on_unimplemented(tcx, trait_def_id, it);
1221 hir::ItemTrait(..) => {
1222 let def_id = tcx.hir.local_def_id(it.id);
1223 check_on_unimplemented(tcx, def_id, it);
1225 hir::ItemStruct(..) => {
1226 check_struct(tcx, it.id, it.span);
1228 hir::ItemUnion(..) => {
1229 check_union(tcx, it.id, it.span);
1231 hir::ItemTy(_, ref generics) => {
1232 let def_id = tcx.hir.local_def_id(it.id);
1233 let pty_ty = tcx.type_of(def_id);
1234 check_bounds_are_used(tcx, generics, pty_ty);
1236 hir::ItemForeignMod(ref m) => {
1237 check_abi(tcx, it.span, m.abi);
1239 if m.abi == Abi::RustIntrinsic {
1240 for item in &m.items {
1241 intrinsic::check_intrinsic_type(tcx, item);
1243 } else if m.abi == Abi::PlatformIntrinsic {
1244 for item in &m.items {
1245 intrinsic::check_platform_intrinsic_type(tcx, item);
1248 for item in &m.items {
1249 let generics = tcx.generics_of(tcx.hir.local_def_id(item.id));
1250 if !generics.types.is_empty() {
1251 let mut err = struct_span_err!(tcx.sess, item.span, E0044,
1252 "foreign items may not have type parameters");
1253 err.span_label(item.span, "can't have type parameters");
1254 // FIXME: once we start storing spans for type arguments, turn this into a
1256 err.help("use specialization instead of type parameters by replacing them \
1257 with concrete types like `u32`");
1261 if let hir::ForeignItemFn(ref fn_decl, _, _) = item.node {
1262 require_c_abi_if_variadic(tcx, fn_decl, m.abi, item.span);
1267 _ => {/* nothing to do */ }
1271 fn check_const_is_u8_array<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
1274 match tcx.type_of(def_id).sty {
1275 ty::TyArray(t, _) => {
1277 ty::TyUint(ast::UintTy::U8) => return,
1283 tcx.sess.span_err(span, "must be an array of bytes like `[u8; N]`");
1286 fn check_on_unimplemented<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
1287 trait_def_id: DefId,
1289 let item_def_id = tcx.hir.local_def_id(item.id);
1290 // an error would be reported if this fails.
1291 let _ = traits::OnUnimplementedDirective::of_item(tcx, trait_def_id, item_def_id);
1294 fn report_forbidden_specialization<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
1295 impl_item: &hir::ImplItem,
1298 let mut err = struct_span_err!(
1299 tcx.sess, impl_item.span, E0520,
1300 "`{}` specializes an item from a parent `impl`, but \
1301 that item is not marked `default`",
1303 err.span_label(impl_item.span, format!("cannot specialize default item `{}`",
1306 match tcx.span_of_impl(parent_impl) {
1308 err.span_label(span, "parent `impl` is here");
1309 err.note(&format!("to specialize, `{}` in the parent `impl` must be marked `default`",
1313 err.note(&format!("parent implementation is in crate `{}`", cname));
1320 fn check_specialization_validity<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
1321 trait_def: &ty::TraitDef,
1322 trait_item: &ty::AssociatedItem,
1324 impl_item: &hir::ImplItem)
1326 let ancestors = trait_def.ancestors(tcx, impl_id);
1328 let kind = match impl_item.node {
1329 hir::ImplItemKind::Const(..) => ty::AssociatedKind::Const,
1330 hir::ImplItemKind::Method(..) => ty::AssociatedKind::Method,
1331 hir::ImplItemKind::Type(_) => ty::AssociatedKind::Type
1334 let parent = ancestors.defs(tcx, trait_item.name, kind, trait_def.def_id).skip(1).next()
1335 .map(|node_item| node_item.map(|parent| parent.defaultness));
1337 if let Some(parent) = parent {
1338 if tcx.impl_item_is_final(&parent) {
1339 report_forbidden_specialization(tcx, impl_item, parent.node.def_id());
1345 fn check_impl_items_against_trait<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
1348 impl_trait_ref: ty::TraitRef<'tcx>,
1349 impl_item_refs: &[hir::ImplItemRef]) {
1350 let impl_span = tcx.sess.codemap().def_span(impl_span);
1352 // If the trait reference itself is erroneous (so the compilation is going
1353 // to fail), skip checking the items here -- the `impl_item` table in `tcx`
1354 // isn't populated for such impls.
1355 if impl_trait_ref.references_error() { return; }
1357 // Locate trait definition and items
1358 let trait_def = tcx.trait_def(impl_trait_ref.def_id);
1359 let mut overridden_associated_type = None;
1361 let impl_items = || impl_item_refs.iter().map(|iiref| tcx.hir.impl_item(iiref.id));
1363 // Check existing impl methods to see if they are both present in trait
1364 // and compatible with trait signature
1365 for impl_item in impl_items() {
1366 let ty_impl_item = tcx.associated_item(tcx.hir.local_def_id(impl_item.id));
1367 let ty_trait_item = tcx.associated_items(impl_trait_ref.def_id)
1368 .find(|ac| Namespace::from(&impl_item.node) == Namespace::from(ac.kind) &&
1369 tcx.hygienic_eq(ty_impl_item.name, ac.name, impl_trait_ref.def_id))
1371 // Not compatible, but needed for the error message
1372 tcx.associated_items(impl_trait_ref.def_id)
1373 .find(|ac| tcx.hygienic_eq(ty_impl_item.name, ac.name, impl_trait_ref.def_id))
1376 // Check that impl definition matches trait definition
1377 if let Some(ty_trait_item) = ty_trait_item {
1378 match impl_item.node {
1379 hir::ImplItemKind::Const(..) => {
1380 // Find associated const definition.
1381 if ty_trait_item.kind == ty::AssociatedKind::Const {
1382 compare_const_impl(tcx,
1388 let mut err = struct_span_err!(tcx.sess, impl_item.span, E0323,
1389 "item `{}` is an associated const, \
1390 which doesn't match its trait `{}`",
1393 err.span_label(impl_item.span, "does not match trait");
1394 // We can only get the spans from local trait definition
1395 // Same for E0324 and E0325
1396 if let Some(trait_span) = tcx.hir.span_if_local(ty_trait_item.def_id) {
1397 err.span_label(trait_span, "item in trait");
1402 hir::ImplItemKind::Method(..) => {
1403 let trait_span = tcx.hir.span_if_local(ty_trait_item.def_id);
1404 if ty_trait_item.kind == ty::AssociatedKind::Method {
1405 compare_impl_method(tcx,
1412 let mut err = struct_span_err!(tcx.sess, impl_item.span, E0324,
1413 "item `{}` is an associated method, \
1414 which doesn't match its trait `{}`",
1417 err.span_label(impl_item.span, "does not match trait");
1418 if let Some(trait_span) = tcx.hir.span_if_local(ty_trait_item.def_id) {
1419 err.span_label(trait_span, "item in trait");
1424 hir::ImplItemKind::Type(_) => {
1425 if ty_trait_item.kind == ty::AssociatedKind::Type {
1426 if ty_trait_item.defaultness.has_value() {
1427 overridden_associated_type = Some(impl_item);
1430 let mut err = struct_span_err!(tcx.sess, impl_item.span, E0325,
1431 "item `{}` is an associated type, \
1432 which doesn't match its trait `{}`",
1435 err.span_label(impl_item.span, "does not match trait");
1436 if let Some(trait_span) = tcx.hir.span_if_local(ty_trait_item.def_id) {
1437 err.span_label(trait_span, "item in trait");
1444 check_specialization_validity(tcx, trait_def, &ty_trait_item, impl_id, impl_item);
1448 // Check for missing items from trait
1449 let mut missing_items = Vec::new();
1450 let mut invalidated_items = Vec::new();
1451 let associated_type_overridden = overridden_associated_type.is_some();
1452 for trait_item in tcx.associated_items(impl_trait_ref.def_id) {
1453 let is_implemented = trait_def.ancestors(tcx, impl_id)
1454 .defs(tcx, trait_item.name, trait_item.kind, impl_trait_ref.def_id)
1456 .map(|node_item| !node_item.node.is_from_trait())
1459 if !is_implemented && !tcx.impl_is_default(impl_id) {
1460 if !trait_item.defaultness.has_value() {
1461 missing_items.push(trait_item);
1462 } else if associated_type_overridden {
1463 invalidated_items.push(trait_item.name);
1468 if !missing_items.is_empty() {
1469 let mut err = struct_span_err!(tcx.sess, impl_span, E0046,
1470 "not all trait items implemented, missing: `{}`",
1471 missing_items.iter()
1472 .map(|trait_item| trait_item.name.to_string())
1473 .collect::<Vec<_>>().join("`, `"));
1474 err.span_label(impl_span, format!("missing `{}` in implementation",
1475 missing_items.iter()
1476 .map(|trait_item| trait_item.name.to_string())
1477 .collect::<Vec<_>>().join("`, `")));
1478 for trait_item in missing_items {
1479 if let Some(span) = tcx.hir.span_if_local(trait_item.def_id) {
1480 err.span_label(span, format!("`{}` from trait", trait_item.name));
1482 err.note_trait_signature(trait_item.name.to_string(),
1483 trait_item.signature(&tcx));
1489 if !invalidated_items.is_empty() {
1490 let invalidator = overridden_associated_type.unwrap();
1491 span_err!(tcx.sess, invalidator.span, E0399,
1492 "the following trait items need to be reimplemented \
1493 as `{}` was overridden: `{}`",
1495 invalidated_items.iter()
1496 .map(|name| name.to_string())
1497 .collect::<Vec<_>>().join("`, `"))
1501 /// Checks whether a type can be represented in memory. In particular, it
1502 /// identifies types that contain themselves without indirection through a
1503 /// pointer, which would mean their size is unbounded.
1504 fn check_representable<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
1508 let rty = tcx.type_of(item_def_id);
1510 // Check that it is possible to represent this type. This call identifies
1511 // (1) types that contain themselves and (2) types that contain a different
1512 // recursive type. It is only necessary to throw an error on those that
1513 // contain themselves. For case 2, there must be an inner type that will be
1514 // caught by case 1.
1515 match rty.is_representable(tcx, sp) {
1516 Representability::SelfRecursive(spans) => {
1517 let mut err = tcx.recursive_type_with_infinite_size_error(item_def_id);
1519 err.span_label(span, "recursive without indirection");
1524 Representability::Representable | Representability::ContainsRecursive => (),
1529 pub fn check_simd<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, sp: Span, def_id: DefId) {
1530 let t = tcx.type_of(def_id);
1532 ty::TyAdt(def, substs) if def.is_struct() => {
1533 let fields = &def.non_enum_variant().fields;
1534 if fields.is_empty() {
1535 span_err!(tcx.sess, sp, E0075, "SIMD vector cannot be empty");
1538 let e = fields[0].ty(tcx, substs);
1539 if !fields.iter().all(|f| f.ty(tcx, substs) == e) {
1540 struct_span_err!(tcx.sess, sp, E0076, "SIMD vector should be homogeneous")
1541 .span_label(sp, "SIMD elements must have the same type")
1546 ty::TyParam(_) => { /* struct<T>(T, T, T, T) is ok */ }
1547 _ if e.is_machine() => { /* struct(u8, u8, u8, u8) is ok */ }
1549 span_err!(tcx.sess, sp, E0077,
1550 "SIMD vector element type should be machine type");
1559 fn check_packed<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, sp: Span, def_id: DefId) {
1560 let repr = tcx.adt_def(def_id).repr;
1562 for attr in tcx.get_attrs(def_id).iter() {
1563 for r in attr::find_repr_attrs(tcx.sess.diagnostic(), attr) {
1564 if let attr::ReprPacked(pack) = r {
1565 if pack != repr.pack {
1566 struct_span_err!(tcx.sess, sp, E0634,
1567 "type has conflicting packed representation hints").emit();
1573 struct_span_err!(tcx.sess, sp, E0587,
1574 "type has conflicting packed and align representation hints").emit();
1576 else if check_packed_inner(tcx, def_id, &mut Vec::new()) {
1577 struct_span_err!(tcx.sess, sp, E0588,
1578 "packed type cannot transitively contain a `[repr(align)]` type").emit();
1583 fn check_packed_inner<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
1585 stack: &mut Vec<DefId>) -> bool {
1586 let t = tcx.type_of(def_id);
1587 if stack.contains(&def_id) {
1588 debug!("check_packed_inner: {:?} is recursive", t);
1592 ty::TyAdt(def, substs) if def.is_struct() || def.is_union() => {
1593 if tcx.adt_def(def.did).repr.align > 0 {
1596 // push struct def_id before checking fields
1598 for field in &def.non_enum_variant().fields {
1599 let f = field.ty(tcx, substs);
1601 ty::TyAdt(def, _) => {
1602 if check_packed_inner(tcx, def.did, stack) {
1609 // only need to pop if not early out
1617 fn check_transparent<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, sp: Span, def_id: DefId) {
1618 let adt = tcx.adt_def(def_id);
1619 if !adt.repr.transparent() {
1623 // For each field, figure out if it's known to be a ZST and align(1)
1624 let field_infos: Vec<_> = adt.non_enum_variant().fields.iter().map(|field| {
1625 let ty = field.ty(tcx, Substs::identity_for_item(tcx, field.did));
1626 let param_env = tcx.param_env(field.did);
1627 let layout = tcx.layout_of(param_env.and(ty));
1628 // We are currently checking the type this field came from, so it must be local
1629 let span = tcx.hir.span_if_local(field.did).unwrap();
1630 let zst = layout.map(|layout| layout.is_zst()).unwrap_or(false);
1631 let align1 = layout.map(|layout| layout.align.abi() == 1).unwrap_or(false);
1635 let non_zst_fields = field_infos.iter().filter(|(_span, zst, _align1)| !*zst);
1636 let non_zst_count = non_zst_fields.clone().count();
1637 if non_zst_count != 1 {
1638 let field_spans: Vec<_> = non_zst_fields.map(|(span, _zst, _align1)| *span).collect();
1639 struct_span_err!(tcx.sess, sp, E0690,
1640 "transparent struct needs exactly one non-zero-sized field, but has {}",
1642 .span_note(field_spans, "non-zero-sized field")
1645 for &(span, zst, align1) in &field_infos {
1647 span_err!(tcx.sess, span, E0691,
1648 "zero-sized field in transparent struct has alignment larger than 1");
1653 #[allow(trivial_numeric_casts)]
1654 pub fn check_enum<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
1656 vs: &'tcx [hir::Variant],
1658 let def_id = tcx.hir.local_def_id(id);
1659 let def = tcx.adt_def(def_id);
1660 def.destructor(tcx); // force the destructor to be evaluated
1663 let attributes = tcx.get_attrs(def_id);
1664 if let Some(attr) = attr::find_by_name(&attributes, "repr") {
1666 tcx.sess, attr.span, E0084,
1667 "unsupported representation for zero-variant enum")
1668 .span_label(sp, "zero-variant enum")
1673 let repr_type_ty = def.repr.discr_type().to_ty(tcx);
1674 if repr_type_ty == tcx.types.i128 || repr_type_ty == tcx.types.u128 {
1675 if !tcx.features().repr128 {
1676 emit_feature_err(&tcx.sess.parse_sess,
1679 GateIssue::Language,
1680 "repr with 128-bit type is unstable");
1685 if let Some(e) = v.node.disr_expr {
1686 tcx.typeck_tables_of(tcx.hir.local_def_id(e.node_id));
1690 let mut disr_vals: Vec<Discr<'tcx>> = Vec::new();
1691 for (discr, v) in def.discriminants(tcx).zip(vs) {
1692 // Check for duplicate discriminant values
1693 if let Some(i) = disr_vals.iter().position(|&x| x.val == discr.val) {
1694 let variant_i_node_id = tcx.hir.as_local_node_id(def.variants[i].did).unwrap();
1695 let variant_i = tcx.hir.expect_variant(variant_i_node_id);
1696 let i_span = match variant_i.node.disr_expr {
1697 Some(expr) => tcx.hir.span(expr.node_id),
1698 None => tcx.hir.span(variant_i_node_id)
1700 let span = match v.node.disr_expr {
1701 Some(expr) => tcx.hir.span(expr.node_id),
1704 struct_span_err!(tcx.sess, span, E0081,
1705 "discriminant value `{}` already exists", disr_vals[i])
1706 .span_label(i_span, format!("first use of `{}`", disr_vals[i]))
1707 .span_label(span , format!("enum already has `{}`", disr_vals[i]))
1710 disr_vals.push(discr);
1713 check_representable(tcx, sp, def_id);
1716 impl<'a, 'gcx, 'tcx> AstConv<'gcx, 'tcx> for FnCtxt<'a, 'gcx, 'tcx> {
1717 fn tcx<'b>(&'b self) -> TyCtxt<'b, 'gcx, 'tcx> { self.tcx }
1719 fn get_type_parameter_bounds(&self, _: Span, def_id: DefId)
1720 -> ty::GenericPredicates<'tcx>
1723 let node_id = tcx.hir.as_local_node_id(def_id).unwrap();
1724 let item_id = tcx.hir.ty_param_owner(node_id);
1725 let item_def_id = tcx.hir.local_def_id(item_id);
1726 let generics = tcx.generics_of(item_def_id);
1727 let index = generics.type_param_to_index[&def_id];
1728 ty::GenericPredicates {
1730 predicates: self.param_env.caller_bounds.iter().filter(|predicate| {
1732 ty::Predicate::Trait(ref data) => {
1733 data.skip_binder().self_ty().is_param(index)
1737 }).cloned().collect()
1741 fn re_infer(&self, span: Span, def: Option<&ty::RegionParameterDef>)
1742 -> Option<ty::Region<'tcx>> {
1744 Some(def) => infer::EarlyBoundRegion(span, def.name),
1745 None => infer::MiscVariable(span)
1747 Some(self.next_region_var(v))
1750 fn ty_infer(&self, span: Span) -> Ty<'tcx> {
1751 self.next_ty_var(TypeVariableOrigin::TypeInference(span))
1754 fn ty_infer_for_def(&self,
1755 ty_param_def: &ty::TypeParameterDef,
1756 span: Span) -> Ty<'tcx> {
1757 self.type_var_for_def(span, ty_param_def)
1760 fn projected_ty_from_poly_trait_ref(&self,
1763 poly_trait_ref: ty::PolyTraitRef<'tcx>)
1766 let (trait_ref, _) =
1767 self.replace_late_bound_regions_with_fresh_var(
1769 infer::LateBoundRegionConversionTime::AssocTypeProjection(item_def_id),
1772 self.tcx().mk_projection(item_def_id, trait_ref.substs)
1775 fn normalize_ty(&self, span: Span, ty: Ty<'tcx>) -> Ty<'tcx> {
1776 if ty.has_escaping_regions() {
1777 ty // FIXME: normalization and escaping regions
1779 self.normalize_associated_types_in(span, &ty)
1783 fn set_tainted_by_errors(&self) {
1784 self.infcx.set_tainted_by_errors()
1787 fn record_ty(&self, hir_id: hir::HirId, ty: Ty<'tcx>, _span: Span) {
1788 self.write_ty(hir_id, ty)
1792 /// Controls whether the arguments are tupled. This is used for the call
1795 /// Tupling means that all call-side arguments are packed into a tuple and
1796 /// passed as a single parameter. For example, if tupling is enabled, this
1799 /// fn f(x: (isize, isize))
1801 /// Can be called as:
1808 #[derive(Clone, Eq, PartialEq)]
1809 enum TupleArgumentsFlag {
1814 impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
1815 pub fn new(inh: &'a Inherited<'a, 'gcx, 'tcx>,
1816 param_env: ty::ParamEnv<'tcx>,
1817 body_id: ast::NodeId)
1818 -> FnCtxt<'a, 'gcx, 'tcx> {
1822 err_count_on_creation: inh.tcx.sess.err_count(),
1825 ps: RefCell::new(UnsafetyState::function(hir::Unsafety::Normal,
1826 ast::CRATE_NODE_ID)),
1827 diverges: Cell::new(Diverges::Maybe),
1828 has_errors: Cell::new(false),
1829 enclosing_breakables: RefCell::new(EnclosingBreakables {
1837 pub fn sess(&self) -> &Session {
1841 pub fn err_count_since_creation(&self) -> usize {
1842 self.tcx.sess.err_count() - self.err_count_on_creation
1845 /// Produce warning on the given node, if the current point in the
1846 /// function is unreachable, and there hasn't been another warning.
1847 fn warn_if_unreachable(&self, id: ast::NodeId, span: Span, kind: &str) {
1848 if self.diverges.get() == Diverges::Always {
1849 self.diverges.set(Diverges::WarnedAlways);
1851 debug!("warn_if_unreachable: id={:?} span={:?} kind={}", id, span, kind);
1853 self.tcx().lint_node(
1854 lint::builtin::UNREACHABLE_CODE,
1856 &format!("unreachable {}", kind));
1862 code: ObligationCauseCode<'tcx>)
1863 -> ObligationCause<'tcx> {
1864 ObligationCause::new(span, self.body_id, code)
1867 pub fn misc(&self, span: Span) -> ObligationCause<'tcx> {
1868 self.cause(span, ObligationCauseCode::MiscObligation)
1871 /// Resolves type variables in `ty` if possible. Unlike the infcx
1872 /// version (resolve_type_vars_if_possible), this version will
1873 /// also select obligations if it seems useful, in an effort
1874 /// to get more type information.
1875 fn resolve_type_vars_with_obligations(&self, mut ty: Ty<'tcx>) -> Ty<'tcx> {
1876 debug!("resolve_type_vars_with_obligations(ty={:?})", ty);
1878 // No TyInfer()? Nothing needs doing.
1879 if !ty.has_infer_types() {
1880 debug!("resolve_type_vars_with_obligations: ty={:?}", ty);
1884 // If `ty` is a type variable, see whether we already know what it is.
1885 ty = self.resolve_type_vars_if_possible(&ty);
1886 if !ty.has_infer_types() {
1887 debug!("resolve_type_vars_with_obligations: ty={:?}", ty);
1891 // If not, try resolving pending obligations as much as
1892 // possible. This can help substantially when there are
1893 // indirect dependencies that don't seem worth tracking
1895 self.select_obligations_where_possible(false);
1896 ty = self.resolve_type_vars_if_possible(&ty);
1898 debug!("resolve_type_vars_with_obligations: ty={:?}", ty);
1902 fn record_deferred_call_resolution(&self,
1903 closure_def_id: DefId,
1904 r: DeferredCallResolution<'gcx, 'tcx>) {
1905 let mut deferred_call_resolutions = self.deferred_call_resolutions.borrow_mut();
1906 deferred_call_resolutions.entry(closure_def_id).or_insert(vec![]).push(r);
1909 fn remove_deferred_call_resolutions(&self,
1910 closure_def_id: DefId)
1911 -> Vec<DeferredCallResolution<'gcx, 'tcx>>
1913 let mut deferred_call_resolutions = self.deferred_call_resolutions.borrow_mut();
1914 deferred_call_resolutions.remove(&closure_def_id).unwrap_or(vec![])
1917 pub fn tag(&self) -> String {
1918 let self_ptr: *const FnCtxt = self;
1919 format!("{:?}", self_ptr)
1922 pub fn local_ty(&self, span: Span, nid: ast::NodeId) -> Ty<'tcx> {
1923 match self.locals.borrow().get(&nid) {
1926 span_bug!(span, "no type for local variable {}",
1927 self.tcx.hir.node_to_string(nid));
1933 pub fn write_ty(&self, id: hir::HirId, ty: Ty<'tcx>) {
1934 debug!("write_ty({:?}, {:?}) in fcx {}",
1935 id, self.resolve_type_vars_if_possible(&ty), self.tag());
1936 self.tables.borrow_mut().node_types_mut().insert(id, ty);
1938 if ty.references_error() {
1939 self.has_errors.set(true);
1940 self.set_tainted_by_errors();
1944 pub fn write_field_index(&self, node_id: ast::NodeId, index: usize) {
1945 let hir_id = self.tcx.hir.node_to_hir_id(node_id);
1946 self.tables.borrow_mut().field_indices_mut().insert(hir_id, index);
1949 // The NodeId and the ItemLocalId must identify the same item. We just pass
1950 // both of them for consistency checking.
1951 pub fn write_method_call(&self,
1953 method: MethodCallee<'tcx>) {
1956 .type_dependent_defs_mut()
1957 .insert(hir_id, Def::Method(method.def_id));
1958 self.write_substs(hir_id, method.substs);
1961 pub fn write_substs(&self, node_id: hir::HirId, substs: &'tcx Substs<'tcx>) {
1962 if !substs.is_noop() {
1963 debug!("write_substs({:?}, {:?}) in fcx {}",
1968 self.tables.borrow_mut().node_substs_mut().insert(node_id, substs);
1972 pub fn apply_adjustments(&self, expr: &hir::Expr, adj: Vec<Adjustment<'tcx>>) {
1973 debug!("apply_adjustments(expr={:?}, adj={:?})", expr, adj);
1979 match self.tables.borrow_mut().adjustments_mut().entry(expr.hir_id) {
1980 Entry::Vacant(entry) => { entry.insert(adj); },
1981 Entry::Occupied(mut entry) => {
1982 debug!(" - composing on top of {:?}", entry.get());
1983 match (&entry.get()[..], &adj[..]) {
1984 // Applying any adjustment on top of a NeverToAny
1985 // is a valid NeverToAny adjustment, because it can't
1987 (&[Adjustment { kind: Adjust::NeverToAny, .. }], _) => return,
1989 Adjustment { kind: Adjust::Deref(_), .. },
1990 Adjustment { kind: Adjust::Borrow(AutoBorrow::Ref(..)), .. },
1992 Adjustment { kind: Adjust::Deref(_), .. },
1993 .. // Any following adjustments are allowed.
1995 // A reborrow has no effect before a dereference.
1997 // FIXME: currently we never try to compose autoderefs
1998 // and ReifyFnPointer/UnsafeFnPointer, but we could.
2000 bug!("while adjusting {:?}, can't compose {:?} and {:?}",
2001 expr, entry.get(), adj)
2003 *entry.get_mut() = adj;
2008 /// Basically whenever we are converting from a type scheme into
2009 /// the fn body space, we always want to normalize associated
2010 /// types as well. This function combines the two.
2011 fn instantiate_type_scheme<T>(&self,
2013 substs: &Substs<'tcx>,
2016 where T : TypeFoldable<'tcx>
2018 let value = value.subst(self.tcx, substs);
2019 let result = self.normalize_associated_types_in(span, &value);
2020 debug!("instantiate_type_scheme(value={:?}, substs={:?}) = {:?}",
2027 /// As `instantiate_type_scheme`, but for the bounds found in a
2028 /// generic type scheme.
2029 fn instantiate_bounds(&self, span: Span, def_id: DefId, substs: &Substs<'tcx>)
2030 -> ty::InstantiatedPredicates<'tcx> {
2031 let bounds = self.tcx.predicates_of(def_id);
2032 let result = bounds.instantiate(self.tcx, substs);
2033 let result = self.normalize_associated_types_in(span, &result);
2034 debug!("instantiate_bounds(bounds={:?}, substs={:?}) = {:?}",
2041 /// Replace the anonymized types from the return value of the
2042 /// function with type variables and records the `AnonTypeMap` for
2043 /// later use during writeback. See
2044 /// `InferCtxt::instantiate_anon_types` for more details.
2045 fn instantiate_anon_types_from_return_value<T: TypeFoldable<'tcx>>(
2050 let fn_def_id = self.tcx.hir.local_def_id(fn_id);
2052 "instantiate_anon_types_from_return_value(fn_def_id={:?}, value={:?})",
2057 let (value, anon_type_map) = self.register_infer_ok_obligations(
2058 self.instantiate_anon_types(
2066 let mut anon_types = self.anon_types.borrow_mut();
2067 for (ty, decl) in anon_type_map {
2068 let old_value = anon_types.insert(ty, decl);
2069 assert!(old_value.is_none(), "instantiated twice: {:?}/{:?}", ty, decl);
2075 fn normalize_associated_types_in<T>(&self, span: Span, value: &T) -> T
2076 where T : TypeFoldable<'tcx>
2078 self.inh.normalize_associated_types_in(span, self.body_id, self.param_env, value)
2081 fn normalize_associated_types_in_as_infer_ok<T>(&self, span: Span, value: &T)
2083 where T : TypeFoldable<'tcx>
2085 self.inh.partially_normalize_associated_types_in(span,
2091 pub fn require_type_meets(&self,
2094 code: traits::ObligationCauseCode<'tcx>,
2097 self.register_bound(
2100 traits::ObligationCause::new(span, self.body_id, code));
2103 pub fn require_type_is_sized(&self,
2106 code: traits::ObligationCauseCode<'tcx>)
2108 let lang_item = self.tcx.require_lang_item(lang_items::SizedTraitLangItem);
2109 self.require_type_meets(ty, span, code, lang_item);
2112 pub fn register_bound(&self,
2115 cause: traits::ObligationCause<'tcx>)
2117 self.fulfillment_cx.borrow_mut()
2118 .register_bound(self, self.param_env, ty, def_id, cause);
2121 pub fn to_ty(&self, ast_t: &hir::Ty) -> Ty<'tcx> {
2122 let t = AstConv::ast_ty_to_ty(self, ast_t);
2123 self.register_wf_obligation(t, ast_t.span, traits::MiscObligation);
2127 pub fn node_ty(&self, id: hir::HirId) -> Ty<'tcx> {
2128 match self.tables.borrow().node_types().get(id) {
2130 None if self.is_tainted_by_errors() => self.tcx.types.err,
2132 let node_id = self.tcx.hir.definitions().find_node_for_hir_id(id);
2133 bug!("no type for node {}: {} in fcx {}",
2134 node_id, self.tcx.hir.node_to_string(node_id),
2140 /// Registers an obligation for checking later, during regionck, that the type `ty` must
2141 /// outlive the region `r`.
2142 pub fn register_wf_obligation(&self,
2145 code: traits::ObligationCauseCode<'tcx>)
2147 // WF obligations never themselves fail, so no real need to give a detailed cause:
2148 let cause = traits::ObligationCause::new(span, self.body_id, code);
2149 self.register_predicate(traits::Obligation::new(cause,
2151 ty::Predicate::WellFormed(ty)));
2154 /// Registers obligations that all types appearing in `substs` are well-formed.
2155 pub fn add_wf_bounds(&self, substs: &Substs<'tcx>, expr: &hir::Expr)
2157 for ty in substs.types() {
2158 self.register_wf_obligation(ty, expr.span, traits::MiscObligation);
2162 /// Given a fully substituted set of bounds (`generic_bounds`), and the values with which each
2163 /// type/region parameter was instantiated (`substs`), creates and registers suitable
2164 /// trait/region obligations.
2166 /// For example, if there is a function:
2169 /// fn foo<'a,T:'a>(...)
2172 /// and a reference:
2178 /// Then we will create a fresh region variable `'$0` and a fresh type variable `$1` for `'a`
2179 /// and `T`. This routine will add a region obligation `$1:'$0` and register it locally.
2180 pub fn add_obligations_for_parameters(&self,
2181 cause: traits::ObligationCause<'tcx>,
2182 predicates: &ty::InstantiatedPredicates<'tcx>)
2184 assert!(!predicates.has_escaping_regions());
2186 debug!("add_obligations_for_parameters(predicates={:?})",
2189 for obligation in traits::predicates_for_generics(cause, self.param_env, predicates) {
2190 self.register_predicate(obligation);
2194 // FIXME(arielb1): use this instead of field.ty everywhere
2195 // Only for fields! Returns <none> for methods>
2196 // Indifferent to privacy flags
2197 pub fn field_ty(&self,
2199 field: &'tcx ty::FieldDef,
2200 substs: &Substs<'tcx>)
2203 self.normalize_associated_types_in(span,
2204 &field.ty(self.tcx, substs))
2207 fn check_casts(&self) {
2208 let mut deferred_cast_checks = self.deferred_cast_checks.borrow_mut();
2209 for cast in deferred_cast_checks.drain(..) {
2214 fn resolve_generator_interiors(&self, def_id: DefId) {
2215 let mut generators = self.deferred_generator_interiors.borrow_mut();
2216 for (body_id, interior) in generators.drain(..) {
2217 self.select_obligations_where_possible(false);
2218 generator_interior::resolve_interior(self, def_id, body_id, interior);
2222 // Tries to apply a fallback to `ty` if it is an unsolved variable.
2223 // Non-numerics get replaced with ! or () (depending on whether
2224 // feature(never_type) is enabled, unconstrained ints with i32,
2225 // unconstrained floats with f64.
2226 // Fallback becomes very dubious if we have encountered type-checking errors.
2227 // In that case, fallback to TyError.
2228 // The return value indicates whether fallback has occured.
2229 fn fallback_if_possible(&self, ty: Ty<'tcx>) -> bool {
2230 use rustc::ty::error::UnconstrainedNumeric::Neither;
2231 use rustc::ty::error::UnconstrainedNumeric::{UnconstrainedInt, UnconstrainedFloat};
2233 assert!(ty.is_ty_infer());
2234 let fallback = match self.type_is_unconstrained_numeric(ty) {
2235 _ if self.is_tainted_by_errors() => self.tcx().types.err,
2236 UnconstrainedInt => self.tcx.types.i32,
2237 UnconstrainedFloat => self.tcx.types.f64,
2238 Neither if self.type_var_diverges(ty) => self.tcx.mk_diverging_default(),
2239 Neither => return false,
2241 debug!("default_type_parameters: defaulting `{:?}` to `{:?}`", ty, fallback);
2242 self.demand_eqtype(syntax_pos::DUMMY_SP, ty, fallback);
2246 fn select_all_obligations_or_error(&self) {
2247 debug!("select_all_obligations_or_error");
2248 if let Err(errors) = self.fulfillment_cx.borrow_mut().select_all_or_error(&self) {
2249 self.report_fulfillment_errors(&errors, self.inh.body_id, false);
2253 /// Select as many obligations as we can at present.
2254 fn select_obligations_where_possible(&self, fallback_has_occurred: bool) {
2255 match self.fulfillment_cx.borrow_mut().select_where_possible(self) {
2258 self.report_fulfillment_errors(&errors, self.inh.body_id, fallback_has_occurred);
2263 fn is_place_expr(&self, expr: &hir::Expr) -> bool {
2265 hir::ExprPath(hir::QPath::Resolved(_, ref path)) => {
2267 Def::Local(..) | Def::Upvar(..) | Def::Static(..) | Def::Err => true,
2272 hir::ExprType(ref e, _) => {
2273 self.is_place_expr(e)
2276 hir::ExprUnary(hir::UnDeref, _) |
2277 hir::ExprField(..) |
2278 hir::ExprIndex(..) => {
2282 // Partially qualified paths in expressions can only legally
2283 // refer to associated items which are always rvalues.
2284 hir::ExprPath(hir::QPath::TypeRelative(..)) |
2287 hir::ExprMethodCall(..) |
2288 hir::ExprStruct(..) |
2291 hir::ExprMatch(..) |
2292 hir::ExprClosure(..) |
2293 hir::ExprBlock(..) |
2294 hir::ExprRepeat(..) |
2295 hir::ExprArray(..) |
2296 hir::ExprBreak(..) |
2297 hir::ExprAgain(..) |
2299 hir::ExprWhile(..) |
2301 hir::ExprAssign(..) |
2302 hir::ExprInlineAsm(..) |
2303 hir::ExprAssignOp(..) |
2305 hir::ExprUnary(..) |
2307 hir::ExprAddrOf(..) |
2308 hir::ExprBinary(..) |
2309 hir::ExprYield(..) |
2310 hir::ExprCast(..) => {
2316 /// For the overloaded place expressions (`*x`, `x[3]`), the trait
2317 /// returns a type of `&T`, but the actual type we assign to the
2318 /// *expression* is `T`. So this function just peels off the return
2319 /// type by one layer to yield `T`.
2320 fn make_overloaded_place_return_type(&self,
2321 method: MethodCallee<'tcx>)
2322 -> ty::TypeAndMut<'tcx>
2324 // extract method return type, which will be &T;
2325 let ret_ty = method.sig.output();
2327 // method returns &T, but the type as visible to user is T, so deref
2328 ret_ty.builtin_deref(true).unwrap()
2331 fn lookup_indexing(&self,
2333 base_expr: &'gcx hir::Expr,
2337 -> Option<(/*index type*/ Ty<'tcx>, /*element type*/ Ty<'tcx>)>
2339 // FIXME(#18741) -- this is almost but not quite the same as the
2340 // autoderef that normal method probing does. They could likely be
2343 let mut autoderef = self.autoderef(base_expr.span, base_ty);
2344 let mut result = None;
2345 while result.is_none() && autoderef.next().is_some() {
2346 result = self.try_index_step(expr, base_expr, &autoderef, needs, idx_ty);
2348 autoderef.finalize();
2352 /// To type-check `base_expr[index_expr]`, we progressively autoderef
2353 /// (and otherwise adjust) `base_expr`, looking for a type which either
2354 /// supports builtin indexing or overloaded indexing.
2355 /// This loop implements one step in that search; the autoderef loop
2356 /// is implemented by `lookup_indexing`.
2357 fn try_index_step(&self,
2359 base_expr: &hir::Expr,
2360 autoderef: &Autoderef<'a, 'gcx, 'tcx>,
2363 -> Option<(/*index type*/ Ty<'tcx>, /*element type*/ Ty<'tcx>)>
2365 let adjusted_ty = autoderef.unambiguous_final_ty();
2366 debug!("try_index_step(expr={:?}, base_expr={:?}, adjusted_ty={:?}, \
2373 for &unsize in &[false, true] {
2374 let mut self_ty = adjusted_ty;
2376 // We only unsize arrays here.
2377 if let ty::TyArray(element_ty, _) = adjusted_ty.sty {
2378 self_ty = self.tcx.mk_slice(element_ty);
2384 // If some lookup succeeds, write callee into table and extract index/element
2385 // type from the method signature.
2386 // If some lookup succeeded, install method in table
2387 let input_ty = self.next_ty_var(TypeVariableOrigin::AutoDeref(base_expr.span));
2388 let method = self.try_overloaded_place_op(
2389 expr.span, self_ty, &[input_ty], needs, PlaceOp::Index);
2391 let result = method.map(|ok| {
2392 debug!("try_index_step: success, using overloaded indexing");
2393 let method = self.register_infer_ok_obligations(ok);
2395 let mut adjustments = autoderef.adjust_steps(needs);
2396 if let ty::TyRef(region, _, r_mutbl) = method.sig.inputs()[0].sty {
2397 let mutbl = match r_mutbl {
2398 hir::MutImmutable => AutoBorrowMutability::Immutable,
2399 hir::MutMutable => AutoBorrowMutability::Mutable {
2400 // Indexing can be desugared to a method call,
2401 // so maybe we could use two-phase here.
2402 // See the documentation of AllowTwoPhase for why that's
2403 // not the case today.
2404 allow_two_phase_borrow: AllowTwoPhase::No,
2407 adjustments.push(Adjustment {
2408 kind: Adjust::Borrow(AutoBorrow::Ref(region, mutbl)),
2409 target: self.tcx.mk_ref(region, ty::TypeAndMut {
2416 adjustments.push(Adjustment {
2417 kind: Adjust::Unsize,
2418 target: method.sig.inputs()[0]
2421 self.apply_adjustments(base_expr, adjustments);
2423 self.write_method_call(expr.hir_id, method);
2424 (input_ty, self.make_overloaded_place_return_type(method).ty)
2426 if result.is_some() {
2434 fn resolve_place_op(&self, op: PlaceOp, is_mut: bool) -> (Option<DefId>, Symbol) {
2435 let (tr, name) = match (op, is_mut) {
2436 (PlaceOp::Deref, false) =>
2437 (self.tcx.lang_items().deref_trait(), "deref"),
2438 (PlaceOp::Deref, true) =>
2439 (self.tcx.lang_items().deref_mut_trait(), "deref_mut"),
2440 (PlaceOp::Index, false) =>
2441 (self.tcx.lang_items().index_trait(), "index"),
2442 (PlaceOp::Index, true) =>
2443 (self.tcx.lang_items().index_mut_trait(), "index_mut"),
2445 (tr, Symbol::intern(name))
2448 fn try_overloaded_place_op(&self,
2451 arg_tys: &[Ty<'tcx>],
2454 -> Option<InferOk<'tcx, MethodCallee<'tcx>>>
2456 debug!("try_overloaded_place_op({:?},{:?},{:?},{:?})",
2462 // Try Mut first, if needed.
2463 let (mut_tr, mut_op) = self.resolve_place_op(op, true);
2464 let method = match (needs, mut_tr) {
2465 (Needs::MutPlace, Some(trait_did)) => {
2466 self.lookup_method_in_trait(span, mut_op, trait_did, base_ty, Some(arg_tys))
2471 // Otherwise, fall back to the immutable version.
2472 let (imm_tr, imm_op) = self.resolve_place_op(op, false);
2473 let method = match (method, imm_tr) {
2474 (None, Some(trait_did)) => {
2475 self.lookup_method_in_trait(span, imm_op, trait_did, base_ty, Some(arg_tys))
2477 (method, _) => method,
2483 fn check_method_argument_types(&self,
2486 method: Result<MethodCallee<'tcx>, ()>,
2487 args_no_rcvr: &'gcx [hir::Expr],
2488 tuple_arguments: TupleArgumentsFlag,
2489 expected: Expectation<'tcx>)
2491 let has_error = match method {
2493 method.substs.references_error() || method.sig.references_error()
2498 let err_inputs = self.err_args(args_no_rcvr.len());
2500 let err_inputs = match tuple_arguments {
2501 DontTupleArguments => err_inputs,
2502 TupleArguments => vec![self.tcx.intern_tup(&err_inputs[..])],
2505 self.check_argument_types(sp, expr_sp, &err_inputs[..], &[], args_no_rcvr,
2506 false, tuple_arguments, None);
2507 return self.tcx.types.err;
2510 let method = method.unwrap();
2511 // HACK(eddyb) ignore self in the definition (see above).
2512 let expected_arg_tys = self.expected_inputs_for_expected_output(
2515 method.sig.output(),
2516 &method.sig.inputs()[1..]
2518 self.check_argument_types(sp, expr_sp, &method.sig.inputs()[1..], &expected_arg_tys[..],
2519 args_no_rcvr, method.sig.variadic, tuple_arguments,
2520 self.tcx.hir.span_if_local(method.def_id));
2524 /// Generic function that factors out common logic from function calls,
2525 /// method calls and overloaded operators.
2526 fn check_argument_types(&self,
2529 fn_inputs: &[Ty<'tcx>],
2530 mut expected_arg_tys: &[Ty<'tcx>],
2531 args: &'gcx [hir::Expr],
2533 tuple_arguments: TupleArgumentsFlag,
2534 def_span: Option<Span>) {
2537 // Grab the argument types, supplying fresh type variables
2538 // if the wrong number of arguments were supplied
2539 let supplied_arg_count = if tuple_arguments == DontTupleArguments {
2545 // All the input types from the fn signature must outlive the call
2546 // so as to validate implied bounds.
2547 for &fn_input_ty in fn_inputs {
2548 self.register_wf_obligation(fn_input_ty, sp, traits::MiscObligation);
2551 let expected_arg_count = fn_inputs.len();
2553 let param_count_error = |expected_count: usize,
2558 let mut err = tcx.sess.struct_span_err_with_code(sp,
2559 &format!("this function takes {}{} parameter{} but {} parameter{} supplied",
2560 if variadic {"at least "} else {""},
2562 if expected_count == 1 {""} else {"s"},
2564 if arg_count == 1 {" was"} else {"s were"}),
2565 DiagnosticId::Error(error_code.to_owned()));
2567 if let Some(def_s) = def_span.map(|sp| tcx.sess.codemap().def_span(sp)) {
2568 err.span_label(def_s, "defined here");
2571 let sugg_span = tcx.sess.codemap().end_point(expr_sp);
2572 // remove closing `)` from the span
2573 let sugg_span = sugg_span.shrink_to_lo();
2574 err.span_suggestion(
2576 "expected the unit value `()`; create it with empty parentheses",
2577 String::from("()"));
2579 err.span_label(sp, format!("expected {}{} parameter{}",
2580 if variadic {"at least "} else {""},
2582 if expected_count == 1 {""} else {"s"}));
2587 let formal_tys = if tuple_arguments == TupleArguments {
2588 let tuple_type = self.structurally_resolved_type(sp, fn_inputs[0]);
2589 match tuple_type.sty {
2590 ty::TyTuple(arg_types) if arg_types.len() != args.len() => {
2591 param_count_error(arg_types.len(), args.len(), "E0057", false, false);
2592 expected_arg_tys = &[];
2593 self.err_args(args.len())
2595 ty::TyTuple(arg_types) => {
2596 expected_arg_tys = match expected_arg_tys.get(0) {
2597 Some(&ty) => match ty.sty {
2598 ty::TyTuple(ref tys) => &tys,
2606 span_err!(tcx.sess, sp, E0059,
2607 "cannot use call notation; the first type parameter \
2608 for the function trait is neither a tuple nor unit");
2609 expected_arg_tys = &[];
2610 self.err_args(args.len())
2613 } else if expected_arg_count == supplied_arg_count {
2615 } else if variadic {
2616 if supplied_arg_count >= expected_arg_count {
2619 param_count_error(expected_arg_count, supplied_arg_count, "E0060", true, false);
2620 expected_arg_tys = &[];
2621 self.err_args(supplied_arg_count)
2624 // is the missing argument of type `()`?
2625 let sugg_unit = if expected_arg_tys.len() == 1 && supplied_arg_count == 0 {
2626 self.resolve_type_vars_if_possible(&expected_arg_tys[0]).is_nil()
2627 } else if fn_inputs.len() == 1 && supplied_arg_count == 0 {
2628 self.resolve_type_vars_if_possible(&fn_inputs[0]).is_nil()
2632 param_count_error(expected_arg_count, supplied_arg_count, "E0061", false, sugg_unit);
2634 expected_arg_tys = &[];
2635 self.err_args(supplied_arg_count)
2637 // If there is no expectation, expect formal_tys.
2638 let expected_arg_tys = if !expected_arg_tys.is_empty() {
2644 debug!("check_argument_types: formal_tys={:?}",
2645 formal_tys.iter().map(|t| self.ty_to_string(*t)).collect::<Vec<String>>());
2647 // Check the arguments.
2648 // We do this in a pretty awful way: first we typecheck any arguments
2649 // that are not closures, then we typecheck the closures. This is so
2650 // that we have more information about the types of arguments when we
2651 // typecheck the functions. This isn't really the right way to do this.
2652 for &check_closures in &[false, true] {
2653 debug!("check_closures={}", check_closures);
2655 // More awful hacks: before we check argument types, try to do
2656 // an "opportunistic" vtable resolution of any trait bounds on
2657 // the call. This helps coercions.
2659 self.select_obligations_where_possible(false);
2662 // For variadic functions, we don't have a declared type for all of
2663 // the arguments hence we only do our usual type checking with
2664 // the arguments who's types we do know.
2665 let t = if variadic {
2667 } else if tuple_arguments == TupleArguments {
2672 for (i, arg) in args.iter().take(t).enumerate() {
2673 // Warn only for the first loop (the "no closures" one).
2674 // Closure arguments themselves can't be diverging, but
2675 // a previous argument can, e.g. `foo(panic!(), || {})`.
2676 if !check_closures {
2677 self.warn_if_unreachable(arg.id, arg.span, "expression");
2680 let is_closure = match arg.node {
2681 hir::ExprClosure(..) => true,
2685 if is_closure != check_closures {
2689 debug!("checking the argument");
2690 let formal_ty = formal_tys[i];
2692 // The special-cased logic below has three functions:
2693 // 1. Provide as good of an expected type as possible.
2694 let expected = Expectation::rvalue_hint(self, expected_arg_tys[i]);
2696 let checked_ty = self.check_expr_with_expectation(&arg, expected);
2698 // 2. Coerce to the most detailed type that could be coerced
2699 // to, which is `expected_ty` if `rvalue_hint` returns an
2700 // `ExpectHasType(expected_ty)`, or the `formal_ty` otherwise.
2701 let coerce_ty = expected.only_has_type(self).unwrap_or(formal_ty);
2702 // We're processing function arguments so we definitely want to use
2703 // two-phase borrows.
2704 self.demand_coerce(&arg, checked_ty, coerce_ty, AllowTwoPhase::Yes);
2706 // 3. Relate the expected type and the formal one,
2707 // if the expected type was used for the coercion.
2708 self.demand_suptype(arg.span, formal_ty, coerce_ty);
2712 // We also need to make sure we at least write the ty of the other
2713 // arguments which we skipped above.
2715 fn variadic_error<'tcx>(s: &Session, span: Span, t: Ty<'tcx>, cast_ty: &str) {
2716 use structured_errors::{VariadicError, StructuredDiagnostic};
2717 VariadicError::new(s, span, t, cast_ty).diagnostic().emit();
2720 for arg in args.iter().skip(expected_arg_count) {
2721 let arg_ty = self.check_expr(&arg);
2723 // There are a few types which get autopromoted when passed via varargs
2724 // in C but we just error out instead and require explicit casts.
2725 let arg_ty = self.structurally_resolved_type(arg.span, arg_ty);
2727 ty::TyFloat(ast::FloatTy::F32) => {
2728 variadic_error(tcx.sess, arg.span, arg_ty, "c_double");
2730 ty::TyInt(ast::IntTy::I8) | ty::TyInt(ast::IntTy::I16) | ty::TyBool => {
2731 variadic_error(tcx.sess, arg.span, arg_ty, "c_int");
2733 ty::TyUint(ast::UintTy::U8) | ty::TyUint(ast::UintTy::U16) => {
2734 variadic_error(tcx.sess, arg.span, arg_ty, "c_uint");
2736 ty::TyFnDef(..) => {
2737 let ptr_ty = self.tcx.mk_fn_ptr(arg_ty.fn_sig(self.tcx));
2738 let ptr_ty = self.resolve_type_vars_if_possible(&ptr_ty);
2739 variadic_error(tcx.sess, arg.span, arg_ty, &format!("{}", ptr_ty));
2747 fn err_args(&self, len: usize) -> Vec<Ty<'tcx>> {
2748 (0..len).map(|_| self.tcx.types.err).collect()
2751 // AST fragment checking
2754 expected: Expectation<'tcx>)
2760 ast::LitKind::Str(..) => tcx.mk_static_str(),
2761 ast::LitKind::ByteStr(ref v) => {
2762 tcx.mk_imm_ref(tcx.types.re_static,
2763 tcx.mk_array(tcx.types.u8, v.len() as u64))
2765 ast::LitKind::Byte(_) => tcx.types.u8,
2766 ast::LitKind::Char(_) => tcx.types.char,
2767 ast::LitKind::Int(_, ast::LitIntType::Signed(t)) => tcx.mk_mach_int(t),
2768 ast::LitKind::Int(_, ast::LitIntType::Unsigned(t)) => tcx.mk_mach_uint(t),
2769 ast::LitKind::Int(_, ast::LitIntType::Unsuffixed) => {
2770 let opt_ty = expected.to_option(self).and_then(|ty| {
2772 ty::TyInt(_) | ty::TyUint(_) => Some(ty),
2773 ty::TyChar => Some(tcx.types.u8),
2774 ty::TyRawPtr(..) => Some(tcx.types.usize),
2775 ty::TyFnDef(..) | ty::TyFnPtr(_) => Some(tcx.types.usize),
2779 opt_ty.unwrap_or_else(
2780 || tcx.mk_int_var(self.next_int_var_id()))
2782 ast::LitKind::Float(_, t) => tcx.mk_mach_float(t),
2783 ast::LitKind::FloatUnsuffixed(_) => {
2784 let opt_ty = expected.to_option(self).and_then(|ty| {
2786 ty::TyFloat(_) => Some(ty),
2790 opt_ty.unwrap_or_else(
2791 || tcx.mk_float_var(self.next_float_var_id()))
2793 ast::LitKind::Bool(_) => tcx.types.bool
2797 fn check_expr_eq_type(&self,
2798 expr: &'gcx hir::Expr,
2799 expected: Ty<'tcx>) {
2800 let ty = self.check_expr_with_hint(expr, expected);
2801 self.demand_eqtype(expr.span, expected, ty);
2804 pub fn check_expr_has_type_or_error(&self,
2805 expr: &'gcx hir::Expr,
2806 expected: Ty<'tcx>) -> Ty<'tcx> {
2807 self.check_expr_meets_expectation_or_error(expr, ExpectHasType(expected))
2810 fn check_expr_meets_expectation_or_error(&self,
2811 expr: &'gcx hir::Expr,
2812 expected: Expectation<'tcx>) -> Ty<'tcx> {
2813 let expected_ty = expected.to_option(&self).unwrap_or(self.tcx.types.bool);
2814 let mut ty = self.check_expr_with_expectation(expr, expected);
2816 // While we don't allow *arbitrary* coercions here, we *do* allow
2817 // coercions from ! to `expected`.
2819 assert!(!self.tables.borrow().adjustments().contains_key(expr.hir_id),
2820 "expression with never type wound up being adjusted");
2821 let adj_ty = self.next_diverging_ty_var(
2822 TypeVariableOrigin::AdjustmentType(expr.span));
2823 self.apply_adjustments(expr, vec![Adjustment {
2824 kind: Adjust::NeverToAny,
2830 if let Some(mut err) = self.demand_suptype_diag(expr.span, expected_ty, ty) {
2831 // Add help to type error if this is an `if` condition with an assignment
2832 match (expected, &expr.node) {
2833 (ExpectIfCondition, &hir::ExprAssign(ref lhs, ref rhs)) => {
2834 let msg = "try comparing for equality";
2835 if let (Ok(left), Ok(right)) = (
2836 self.tcx.sess.codemap().span_to_snippet(lhs.span),
2837 self.tcx.sess.codemap().span_to_snippet(rhs.span))
2839 err.span_suggestion(expr.span, msg, format!("{} == {}", left, right));
2851 fn check_expr_coercable_to_type(&self,
2852 expr: &'gcx hir::Expr,
2853 expected: Ty<'tcx>) -> Ty<'tcx> {
2854 let ty = self.check_expr_with_hint(expr, expected);
2855 // checks don't need two phase
2856 self.demand_coerce(expr, ty, expected, AllowTwoPhase::No)
2859 fn check_expr_with_hint(&self, expr: &'gcx hir::Expr,
2860 expected: Ty<'tcx>) -> Ty<'tcx> {
2861 self.check_expr_with_expectation(expr, ExpectHasType(expected))
2864 fn check_expr_with_expectation(&self,
2865 expr: &'gcx hir::Expr,
2866 expected: Expectation<'tcx>) -> Ty<'tcx> {
2867 self.check_expr_with_expectation_and_needs(expr, expected, Needs::None)
2870 fn check_expr(&self, expr: &'gcx hir::Expr) -> Ty<'tcx> {
2871 self.check_expr_with_expectation(expr, NoExpectation)
2874 fn check_expr_with_needs(&self, expr: &'gcx hir::Expr, needs: Needs) -> Ty<'tcx> {
2875 self.check_expr_with_expectation_and_needs(expr, NoExpectation, needs)
2878 // determine the `self` type, using fresh variables for all variables
2879 // declared on the impl declaration e.g., `impl<A,B> for Vec<(A,B)>`
2880 // would return ($0, $1) where $0 and $1 are freshly instantiated type
2882 pub fn impl_self_ty(&self,
2883 span: Span, // (potential) receiver for this impl
2885 -> TypeAndSubsts<'tcx> {
2886 let ity = self.tcx.type_of(did);
2887 debug!("impl_self_ty: ity={:?}", ity);
2889 let substs = self.fresh_substs_for_item(span, did);
2890 let substd_ty = self.instantiate_type_scheme(span, &substs, &ity);
2892 TypeAndSubsts { substs: substs, ty: substd_ty }
2895 /// Unifies the output type with the expected type early, for more coercions
2896 /// and forward type information on the input expressions.
2897 fn expected_inputs_for_expected_output(&self,
2899 expected_ret: Expectation<'tcx>,
2900 formal_ret: Ty<'tcx>,
2901 formal_args: &[Ty<'tcx>])
2903 let formal_ret = self.resolve_type_vars_with_obligations(formal_ret);
2904 let ret_ty = match expected_ret.only_has_type(self) {
2906 None => return Vec::new()
2908 let expect_args = self.fudge_regions_if_ok(&RegionVariableOrigin::Coercion(call_span), || {
2909 // Attempt to apply a subtyping relationship between the formal
2910 // return type (likely containing type variables if the function
2911 // is polymorphic) and the expected return type.
2912 // No argument expectations are produced if unification fails.
2913 let origin = self.misc(call_span);
2914 let ures = self.at(&origin, self.param_env).sup(ret_ty, &formal_ret);
2916 // FIXME(#27336) can't use ? here, Try::from_error doesn't default
2917 // to identity so the resulting type is not constrained.
2920 // Process any obligations locally as much as
2921 // we can. We don't care if some things turn
2922 // out unconstrained or ambiguous, as we're
2923 // just trying to get hints here.
2924 self.save_and_restore_in_snapshot_flag(|_| {
2925 let mut fulfill = TraitEngine::new(self.tcx);
2926 for obligation in ok.obligations {
2927 fulfill.register_predicate_obligation(self, obligation);
2929 fulfill.select_where_possible(self)
2930 }).map_err(|_| ())?;
2932 Err(_) => return Err(()),
2935 // Record all the argument types, with the substitutions
2936 // produced from the above subtyping unification.
2937 Ok(formal_args.iter().map(|ty| {
2938 self.resolve_type_vars_if_possible(ty)
2940 }).unwrap_or(Vec::new());
2941 debug!("expected_inputs_for_expected_output(formal={:?} -> {:?}, expected={:?} -> {:?})",
2942 formal_args, formal_ret,
2943 expect_args, expected_ret);
2947 // Checks a method call.
2948 fn check_method_call(&self,
2949 expr: &'gcx hir::Expr,
2950 segment: &hir::PathSegment,
2952 args: &'gcx [hir::Expr],
2953 expected: Expectation<'tcx>,
2954 needs: Needs) -> Ty<'tcx> {
2955 let rcvr = &args[0];
2956 let rcvr_t = self.check_expr_with_needs(&rcvr, needs);
2957 // no need to check for bot/err -- callee does that
2958 let rcvr_t = self.structurally_resolved_type(args[0].span, rcvr_t);
2960 let method = match self.lookup_method(rcvr_t,
2966 self.write_method_call(expr.hir_id, method);
2970 if segment.name != keywords::Invalid.name() {
2971 self.report_method_error(span,
2982 // Call the generic checker.
2983 self.check_method_argument_types(span,
2991 fn check_return_expr(&self, return_expr: &'gcx hir::Expr) {
2995 .unwrap_or_else(|| span_bug!(return_expr.span,
2996 "check_return_expr called outside fn body"));
2998 let ret_ty = ret_coercion.borrow().expected_ty();
2999 let return_expr_ty = self.check_expr_with_hint(return_expr, ret_ty.clone());
3000 ret_coercion.borrow_mut()
3002 &self.cause(return_expr.span,
3003 ObligationCauseCode::ReturnType(return_expr.id)),
3006 self.diverges.get());
3010 // A generic function for checking the then and else in an if
3012 fn check_then_else(&self,
3013 cond_expr: &'gcx hir::Expr,
3014 then_expr: &'gcx hir::Expr,
3015 opt_else_expr: Option<&'gcx hir::Expr>,
3017 expected: Expectation<'tcx>) -> Ty<'tcx> {
3018 let cond_ty = self.check_expr_meets_expectation_or_error(cond_expr, ExpectIfCondition);
3019 let cond_diverges = self.diverges.get();
3020 self.diverges.set(Diverges::Maybe);
3022 let expected = expected.adjust_for_branches(self);
3023 let then_ty = self.check_expr_with_expectation(then_expr, expected);
3024 let then_diverges = self.diverges.get();
3025 self.diverges.set(Diverges::Maybe);
3027 // We've already taken the expected type's preferences
3028 // into account when typing the `then` branch. To figure
3029 // out the initial shot at a LUB, we thus only consider
3030 // `expected` if it represents a *hard* constraint
3031 // (`only_has_type`); otherwise, we just go with a
3032 // fresh type variable.
3033 let coerce_to_ty = expected.coercion_target_type(self, sp);
3034 let mut coerce: DynamicCoerceMany = CoerceMany::new(coerce_to_ty);
3036 let if_cause = self.cause(sp, ObligationCauseCode::IfExpression);
3037 coerce.coerce(self, &if_cause, then_expr, then_ty, then_diverges);
3039 if let Some(else_expr) = opt_else_expr {
3040 let else_ty = self.check_expr_with_expectation(else_expr, expected);
3041 let else_diverges = self.diverges.get();
3043 coerce.coerce(self, &if_cause, else_expr, else_ty, else_diverges);
3045 // We won't diverge unless both branches do (or the condition does).
3046 self.diverges.set(cond_diverges | then_diverges & else_diverges);
3048 let else_cause = self.cause(sp, ObligationCauseCode::IfExpressionWithNoElse);
3049 coerce.coerce_forced_unit(self, &else_cause, &mut |_| (), true);
3051 // If the condition is false we can't diverge.
3052 self.diverges.set(cond_diverges);
3055 let result_ty = coerce.complete(self);
3056 if cond_ty.references_error() {
3063 // Check field access expressions
3064 fn check_field(&self,
3065 expr: &'gcx hir::Expr,
3067 base: &'gcx hir::Expr,
3068 field: &Spanned<ast::Name>) -> Ty<'tcx> {
3069 let expr_t = self.check_expr_with_needs(base, needs);
3070 let expr_t = self.structurally_resolved_type(expr.span,
3072 let mut private_candidate = None;
3073 let mut autoderef = self.autoderef(expr.span, expr_t);
3074 while let Some((base_t, _)) = autoderef.next() {
3076 ty::TyAdt(base_def, substs) if !base_def.is_enum() => {
3077 debug!("struct named {:?}", base_t);
3078 let (ident, def_scope) =
3079 self.tcx.adjust(field.node, base_def.did, self.body_id);
3080 let fields = &base_def.non_enum_variant().fields;
3081 if let Some(index) = fields.iter().position(|f| f.name.to_ident() == ident) {
3082 let field = &fields[index];
3083 let field_ty = self.field_ty(expr.span, field, substs);
3084 // Save the index of all fields regardless of their visibility in case
3085 // of error recovery.
3086 self.write_field_index(expr.id, index);
3087 if field.vis.is_accessible_from(def_scope, self.tcx) {
3088 let adjustments = autoderef.adjust_steps(needs);
3089 self.apply_adjustments(base, adjustments);
3090 autoderef.finalize();
3092 self.tcx.check_stability(field.did, Some(expr.id), expr.span);
3095 private_candidate = Some((base_def.did, field_ty));
3098 ty::TyTuple(ref tys) => {
3099 let fstr = field.node.as_str();
3100 if let Ok(index) = fstr.parse::<usize>() {
3101 if fstr == index.to_string() {
3102 if let Some(field_ty) = tys.get(index) {
3103 let adjustments = autoderef.adjust_steps(needs);
3104 self.apply_adjustments(base, adjustments);
3105 autoderef.finalize();
3107 self.write_field_index(expr.id, index);
3116 autoderef.unambiguous_final_ty();
3118 if let Some((did, field_ty)) = private_candidate {
3119 let struct_path = self.tcx().item_path_str(did);
3120 let mut err = struct_span_err!(self.tcx().sess, expr.span, E0616,
3121 "field `{}` of struct `{}` is private",
3122 field.node, struct_path);
3123 // Also check if an accessible method exists, which is often what is meant.
3124 if self.method_exists(field.span, field.node, expr_t, expr.id, false) {
3125 err.note(&format!("a method `{}` also exists, perhaps you wish to call it",
3130 } else if field.node == keywords::Invalid.name() {
3131 self.tcx().types.err
3132 } else if self.method_exists(field.span, field.node, expr_t, expr.id, true) {
3133 type_error_struct!(self.tcx().sess, field.span, expr_t, E0615,
3134 "attempted to take value of method `{}` on type `{}`",
3136 .help("maybe a `()` to call it is missing?")
3138 self.tcx().types.err
3140 if !expr_t.is_primitive_ty() {
3141 let mut err = self.no_such_field_err(field.span, &field.node, expr_t);
3144 ty::TyAdt(def, _) if !def.is_enum() => {
3145 if let Some(suggested_field_name) =
3146 Self::suggest_field_name(def.non_enum_variant(), field, vec![]) {
3147 err.span_label(field.span,
3148 format!("did you mean `{}`?", suggested_field_name));
3150 err.span_label(field.span, "unknown field");
3151 let struct_variant_def = def.non_enum_variant();
3152 let field_names = self.available_field_names(struct_variant_def);
3153 if !field_names.is_empty() {
3154 err.note(&format!("available fields are: {}",
3155 self.name_series_display(field_names)));
3159 ty::TyRawPtr(..) => {
3160 let base = self.tcx.hir.node_to_pretty_string(base.id);
3161 let msg = format!("`{}` is a native pointer; try dereferencing it", base);
3162 let suggestion = format!("(*{}).{}", base, field.node);
3163 err.span_suggestion(field.span, &msg, suggestion);
3169 type_error_struct!(self.tcx().sess, field.span, expr_t, E0610,
3170 "`{}` is a primitive type and therefore doesn't have fields",
3173 self.tcx().types.err
3177 // Return an hint about the closest match in field names
3178 fn suggest_field_name(variant: &'tcx ty::VariantDef,
3179 field: &Spanned<ast::Name>,
3180 skip: Vec<LocalInternedString>)
3182 let name = field.node.as_str();
3183 let names = variant.fields.iter().filter_map(|field| {
3184 // ignore already set fields and private fields from non-local crates
3185 if skip.iter().any(|x| *x == field.name.as_str()) ||
3186 (variant.did.krate != LOCAL_CRATE && field.vis != Visibility::Public) {
3193 find_best_match_for_name(names, &name, None)
3196 fn available_field_names(&self, variant: &'tcx ty::VariantDef) -> Vec<ast::Name> {
3197 let mut available = Vec::new();
3198 for field in variant.fields.iter() {
3199 let (_, def_scope) = self.tcx.adjust(field.name, variant.did, self.body_id);
3200 if field.vis.is_accessible_from(def_scope, self.tcx) {
3201 available.push(field.name);
3207 fn name_series_display(&self, names: Vec<ast::Name>) -> String {
3208 // dynamic limit, to never omit just one field
3209 let limit = if names.len() == 6 { 6 } else { 5 };
3210 let mut display = names.iter().take(limit)
3211 .map(|n| format!("`{}`", n)).collect::<Vec<_>>().join(", ");
3212 if names.len() > limit {
3213 display = format!("{} ... and {} others", display, names.len() - limit);
3218 fn no_such_field_err<T: Display>(&self, span: Span, field: T, expr_t: &ty::TyS)
3219 -> DiagnosticBuilder {
3220 type_error_struct!(self.tcx().sess, span, expr_t, E0609,
3221 "no field `{}` on type `{}`",
3225 fn report_unknown_field(&self,
3227 variant: &'tcx ty::VariantDef,
3229 skip_fields: &[hir::Field],
3231 let mut err = self.type_error_struct_with_diag(
3233 |actual| match ty.sty {
3234 ty::TyAdt(adt, ..) if adt.is_enum() => {
3235 struct_span_err!(self.tcx.sess, field.name.span, E0559,
3236 "{} `{}::{}` has no field named `{}`",
3237 kind_name, actual, variant.name, field.name.node)
3240 struct_span_err!(self.tcx.sess, field.name.span, E0560,
3241 "{} `{}` has no field named `{}`",
3242 kind_name, actual, field.name.node)
3246 // prevent all specified fields from being suggested
3247 let skip_fields = skip_fields.iter().map(|ref x| x.name.node.as_str());
3248 if let Some(field_name) = Self::suggest_field_name(variant,
3250 skip_fields.collect()) {
3251 err.span_label(field.name.span,
3252 format!("field does not exist - did you mean `{}`?", field_name));
3255 ty::TyAdt(adt, ..) => {
3257 err.span_label(field.name.span,
3258 format!("`{}::{}` does not have this field",
3261 err.span_label(field.name.span,
3262 format!("`{}` does not have this field", ty));
3264 let available_field_names = self.available_field_names(variant);
3265 if !available_field_names.is_empty() {
3266 err.note(&format!("available fields are: {}",
3267 self.name_series_display(available_field_names)));
3270 _ => bug!("non-ADT passed to report_unknown_field")
3276 fn check_expr_struct_fields(&self,
3278 expected: Expectation<'tcx>,
3279 expr_id: ast::NodeId,
3281 variant: &'tcx ty::VariantDef,
3282 ast_fields: &'gcx [hir::Field],
3283 check_completeness: bool) {
3287 self.expected_inputs_for_expected_output(span, expected, adt_ty, &[adt_ty])
3288 .get(0).cloned().unwrap_or(adt_ty);
3289 // re-link the regions that EIfEO can erase.
3290 self.demand_eqtype(span, adt_ty_hint, adt_ty);
3292 let (substs, adt_kind, kind_name) = match &adt_ty.sty{
3293 &ty::TyAdt(adt, substs) => {
3294 (substs, adt.adt_kind(), adt.variant_descr())
3296 _ => span_bug!(span, "non-ADT passed to check_expr_struct_fields")
3299 let mut remaining_fields = FxHashMap();
3300 for (i, field) in variant.fields.iter().enumerate() {
3301 remaining_fields.insert(field.name.to_ident(), (i, field));
3304 let mut seen_fields = FxHashMap();
3306 let mut error_happened = false;
3308 // Typecheck each field.
3309 for field in ast_fields {
3310 let ident = tcx.adjust(field.name.node, variant.did, self.body_id).0;
3311 let field_type = if let Some((i, v_field)) = remaining_fields.remove(&ident) {
3312 seen_fields.insert(ident, field.span);
3313 self.write_field_index(field.id, i);
3315 // we don't look at stability attributes on
3316 // struct-like enums (yet...), but it's definitely not
3317 // a bug to have construct one.
3318 if adt_kind != ty::AdtKind::Enum {
3319 tcx.check_stability(v_field.did, Some(expr_id), field.span);
3322 self.field_ty(field.span, v_field, substs)
3324 error_happened = true;
3325 if let Some(prev_span) = seen_fields.get(&ident) {
3326 let mut err = struct_span_err!(self.tcx.sess,
3329 "field `{}` specified more than once",
3332 err.span_label(field.name.span, "used more than once");
3333 err.span_label(*prev_span, format!("first use of `{}`", ident));
3337 self.report_unknown_field(adt_ty, variant, field, ast_fields, kind_name);
3343 // Make sure to give a type to the field even if there's
3344 // an error, so we can continue typechecking
3345 self.check_expr_coercable_to_type(&field.expr, field_type);
3348 // Make sure the programmer specified correct number of fields.
3349 if kind_name == "union" {
3350 if ast_fields.len() != 1 {
3351 tcx.sess.span_err(span, "union expressions should have exactly one field");
3353 } else if check_completeness && !error_happened && !remaining_fields.is_empty() {
3354 let len = remaining_fields.len();
3356 let mut displayable_field_names = remaining_fields
3358 .map(|ident| ident.name.as_str())
3359 .collect::<Vec<_>>();
3361 displayable_field_names.sort();
3363 let truncated_fields_error = if len <= 3 {
3366 format!(" and {} other field{}", (len - 3), if len - 3 == 1 {""} else {"s"})
3369 let remaining_fields_names = displayable_field_names.iter().take(3)
3370 .map(|n| format!("`{}`", n))
3371 .collect::<Vec<_>>()
3374 struct_span_err!(tcx.sess, span, E0063,
3375 "missing field{} {}{} in initializer of `{}`",
3376 if remaining_fields.len() == 1 { "" } else { "s" },
3377 remaining_fields_names,
3378 truncated_fields_error,
3380 .span_label(span, format!("missing {}{}",
3381 remaining_fields_names,
3382 truncated_fields_error))
3387 fn check_struct_fields_on_error(&self,
3388 fields: &'gcx [hir::Field],
3389 base_expr: &'gcx Option<P<hir::Expr>>) {
3390 for field in fields {
3391 self.check_expr(&field.expr);
3395 self.check_expr(&base);
3401 pub fn check_struct_path(&self,
3403 node_id: ast::NodeId)
3404 -> Option<(&'tcx ty::VariantDef, Ty<'tcx>)> {
3405 let path_span = match *qpath {
3406 hir::QPath::Resolved(_, ref path) => path.span,
3407 hir::QPath::TypeRelative(ref qself, _) => qself.span
3409 let (def, ty) = self.finish_resolving_struct_path(qpath, path_span, node_id);
3410 let variant = match def {
3412 self.set_tainted_by_errors();
3415 Def::Variant(..) => {
3417 ty::TyAdt(adt, substs) => {
3418 Some((adt.variant_of_def(def), adt.did, substs))
3420 _ => bug!("unexpected type: {:?}", ty.sty)
3423 Def::Struct(..) | Def::Union(..) | Def::TyAlias(..) |
3424 Def::AssociatedTy(..) | Def::SelfTy(..) => {
3426 ty::TyAdt(adt, substs) if !adt.is_enum() => {
3427 Some((adt.non_enum_variant(), adt.did, substs))
3432 _ => bug!("unexpected definition: {:?}", def)
3435 if let Some((variant, did, substs)) = variant {
3436 // Check bounds on type arguments used in the path.
3437 let bounds = self.instantiate_bounds(path_span, did, substs);
3438 let cause = traits::ObligationCause::new(path_span, self.body_id,
3439 traits::ItemObligation(did));
3440 self.add_obligations_for_parameters(cause, &bounds);
3444 struct_span_err!(self.tcx.sess, path_span, E0071,
3445 "expected struct, variant or union type, found {}",
3446 ty.sort_string(self.tcx))
3447 .span_label(path_span, "not a struct")
3453 fn check_expr_struct(&self,
3455 expected: Expectation<'tcx>,
3457 fields: &'gcx [hir::Field],
3458 base_expr: &'gcx Option<P<hir::Expr>>) -> Ty<'tcx>
3460 // Find the relevant variant
3461 let (variant, struct_ty) =
3462 if let Some(variant_ty) = self.check_struct_path(qpath, expr.id) {
3465 self.check_struct_fields_on_error(fields, base_expr);
3466 return self.tcx.types.err;
3469 let path_span = match *qpath {
3470 hir::QPath::Resolved(_, ref path) => path.span,
3471 hir::QPath::TypeRelative(ref qself, _) => qself.span
3474 // Prohibit struct expressions when non exhaustive flag is set.
3475 if let ty::TyAdt(adt, _) = struct_ty.sty {
3476 if !adt.did.is_local() && adt.is_non_exhaustive() {
3477 span_err!(self.tcx.sess, expr.span, E0639,
3478 "cannot create non-exhaustive {} using struct expression",
3479 adt.variant_descr());
3483 self.check_expr_struct_fields(struct_ty, expected, expr.id, path_span, variant, fields,
3484 base_expr.is_none());
3485 if let &Some(ref base_expr) = base_expr {
3486 self.check_expr_has_type_or_error(base_expr, struct_ty);
3487 match struct_ty.sty {
3488 ty::TyAdt(adt, substs) if adt.is_struct() => {
3489 let fru_field_types = adt.non_enum_variant().fields.iter().map(|f| {
3490 self.normalize_associated_types_in(expr.span, &f.ty(self.tcx, substs))
3495 .fru_field_types_mut()
3496 .insert(expr.hir_id, fru_field_types);
3499 span_err!(self.tcx.sess, base_expr.span, E0436,
3500 "functional record update syntax requires a struct");
3504 self.require_type_is_sized(struct_ty, expr.span, traits::StructInitializerSized);
3510 /// If an expression has any sub-expressions that result in a type error,
3511 /// inspecting that expression's type with `ty.references_error()` will return
3512 /// true. Likewise, if an expression is known to diverge, inspecting its
3513 /// type with `ty::type_is_bot` will return true (n.b.: since Rust is
3514 /// strict, _|_ can appear in the type of an expression that does not,
3515 /// itself, diverge: for example, fn() -> _|_.)
3516 /// Note that inspecting a type's structure *directly* may expose the fact
3517 /// that there are actually multiple representations for `TyError`, so avoid
3518 /// that when err needs to be handled differently.
3519 fn check_expr_with_expectation_and_needs(&self,
3520 expr: &'gcx hir::Expr,
3521 expected: Expectation<'tcx>,
3522 needs: Needs) -> Ty<'tcx> {
3523 debug!(">> typechecking: expr={:?} expected={:?}",
3526 // Warn for expressions after diverging siblings.
3527 self.warn_if_unreachable(expr.id, expr.span, "expression");
3529 // Hide the outer diverging and has_errors flags.
3530 let old_diverges = self.diverges.get();
3531 let old_has_errors = self.has_errors.get();
3532 self.diverges.set(Diverges::Maybe);
3533 self.has_errors.set(false);
3535 let ty = self.check_expr_kind(expr, expected, needs);
3537 // Warn for non-block expressions with diverging children.
3540 hir::ExprLoop(..) | hir::ExprWhile(..) |
3541 hir::ExprIf(..) | hir::ExprMatch(..) => {}
3543 _ => self.warn_if_unreachable(expr.id, expr.span, "expression")
3546 // Any expression that produces a value of type `!` must have diverged
3548 self.diverges.set(self.diverges.get() | Diverges::Always);
3551 // Record the type, which applies it effects.
3552 // We need to do this after the warning above, so that
3553 // we don't warn for the diverging expression itself.
3554 self.write_ty(expr.hir_id, ty);
3556 // Combine the diverging and has_error flags.
3557 self.diverges.set(self.diverges.get() | old_diverges);
3558 self.has_errors.set(self.has_errors.get() | old_has_errors);
3560 debug!("type of {} is...", self.tcx.hir.node_to_string(expr.id));
3561 debug!("... {:?}, expected is {:?}", ty, expected);
3566 fn check_expr_kind(&self,
3567 expr: &'gcx hir::Expr,
3568 expected: Expectation<'tcx>,
3569 needs: Needs) -> Ty<'tcx> {
3573 hir::ExprBox(ref subexpr) => {
3574 let expected_inner = expected.to_option(self).map_or(NoExpectation, |ty| {
3576 ty::TyAdt(def, _) if def.is_box()
3577 => Expectation::rvalue_hint(self, ty.boxed_ty()),
3581 let referent_ty = self.check_expr_with_expectation(subexpr, expected_inner);
3582 tcx.mk_box(referent_ty)
3585 hir::ExprLit(ref lit) => {
3586 self.check_lit(&lit, expected)
3588 hir::ExprBinary(op, ref lhs, ref rhs) => {
3589 self.check_binop(expr, op, lhs, rhs)
3591 hir::ExprAssignOp(op, ref lhs, ref rhs) => {
3592 self.check_binop_assign(expr, op, lhs, rhs)
3594 hir::ExprUnary(unop, ref oprnd) => {
3595 let expected_inner = match unop {
3596 hir::UnNot | hir::UnNeg => {
3603 let needs = match unop {
3604 hir::UnDeref => needs,
3607 let mut oprnd_t = self.check_expr_with_expectation_and_needs(&oprnd,
3611 if !oprnd_t.references_error() {
3612 oprnd_t = self.structurally_resolved_type(expr.span, oprnd_t);
3615 if let Some(mt) = oprnd_t.builtin_deref(true) {
3617 } else if let Some(ok) = self.try_overloaded_deref(
3618 expr.span, oprnd_t, needs) {
3619 let method = self.register_infer_ok_obligations(ok);
3620 if let ty::TyRef(region, _, mutbl) = method.sig.inputs()[0].sty {
3621 let mutbl = match mutbl {
3622 hir::MutImmutable => AutoBorrowMutability::Immutable,
3623 hir::MutMutable => AutoBorrowMutability::Mutable {
3624 // (It shouldn't actually matter for unary ops whether
3625 // we enable two-phase borrows or not, since a unary
3626 // op has no additional operands.)
3627 allow_two_phase_borrow: AllowTwoPhase::No,
3630 self.apply_adjustments(oprnd, vec![Adjustment {
3631 kind: Adjust::Borrow(AutoBorrow::Ref(region, mutbl)),
3632 target: method.sig.inputs()[0]
3635 oprnd_t = self.make_overloaded_place_return_type(method).ty;
3636 self.write_method_call(expr.hir_id, method);
3638 type_error_struct!(tcx.sess, expr.span, oprnd_t, E0614,
3639 "type `{}` cannot be dereferenced",
3641 oprnd_t = tcx.types.err;
3645 let result = self.check_user_unop(expr, oprnd_t, unop);
3646 // If it's builtin, we can reuse the type, this helps inference.
3647 if !(oprnd_t.is_integral() || oprnd_t.sty == ty::TyBool) {
3652 let result = self.check_user_unop(expr, oprnd_t, unop);
3653 // If it's builtin, we can reuse the type, this helps inference.
3654 if !(oprnd_t.is_integral() || oprnd_t.is_fp()) {
3662 hir::ExprAddrOf(mutbl, ref oprnd) => {
3663 let hint = expected.only_has_type(self).map_or(NoExpectation, |ty| {
3665 ty::TyRef(_, ty, _) | ty::TyRawPtr(ty::TypeAndMut { ty, .. }) => {
3666 if self.is_place_expr(&oprnd) {
3667 // Places may legitimately have unsized types.
3668 // For example, dereferences of a fat pointer and
3669 // the last field of a struct can be unsized.
3672 Expectation::rvalue_hint(self, ty)
3678 let needs = Needs::maybe_mut_place(mutbl);
3679 let ty = self.check_expr_with_expectation_and_needs(&oprnd, hint, needs);
3681 let tm = ty::TypeAndMut { ty: ty, mutbl: mutbl };
3682 if tm.ty.references_error() {
3685 // Note: at this point, we cannot say what the best lifetime
3686 // is to use for resulting pointer. We want to use the
3687 // shortest lifetime possible so as to avoid spurious borrowck
3688 // errors. Moreover, the longest lifetime will depend on the
3689 // precise details of the value whose address is being taken
3690 // (and how long it is valid), which we don't know yet until type
3691 // inference is complete.
3693 // Therefore, here we simply generate a region variable. The
3694 // region inferencer will then select the ultimate value.
3695 // Finally, borrowck is charged with guaranteeing that the
3696 // value whose address was taken can actually be made to live
3697 // as long as it needs to live.
3698 let region = self.next_region_var(infer::AddrOfRegion(expr.span));
3699 tcx.mk_ref(region, tm)
3702 hir::ExprPath(ref qpath) => {
3703 let (def, opt_ty, segments) = self.resolve_ty_and_def_ufcs(qpath,
3704 expr.id, expr.span);
3705 let ty = if def != Def::Err {
3706 self.instantiate_value_path(segments, opt_ty, def, expr.span, id)
3708 self.set_tainted_by_errors();
3712 // We always require that the type provided as the value for
3713 // a type parameter outlives the moment of instantiation.
3714 let substs = self.tables.borrow().node_substs(expr.hir_id);
3715 self.add_wf_bounds(substs, expr);
3719 hir::ExprInlineAsm(_, ref outputs, ref inputs) => {
3720 for output in outputs {
3721 self.check_expr(output);
3723 for input in inputs {
3724 self.check_expr(input);
3728 hir::ExprBreak(destination, ref expr_opt) => {
3729 if let Some(target_id) = destination.target_id.opt_id() {
3730 let (e_ty, e_diverges, cause);
3731 if let Some(ref e) = *expr_opt {
3732 // If this is a break with a value, we need to type-check
3733 // the expression. Get an expected type from the loop context.
3734 let opt_coerce_to = {
3735 let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
3736 enclosing_breakables.find_breakable(target_id)
3739 .map(|coerce| coerce.expected_ty())
3742 // If the loop context is not a `loop { }`, then break with
3743 // a value is illegal, and `opt_coerce_to` will be `None`.
3744 // Just set expectation to error in that case.
3745 let coerce_to = opt_coerce_to.unwrap_or(tcx.types.err);
3747 // Recurse without `enclosing_breakables` borrowed.
3748 e_ty = self.check_expr_with_hint(e, coerce_to);
3749 e_diverges = self.diverges.get();
3750 cause = self.misc(e.span);
3752 // Otherwise, this is a break *without* a value. That's
3753 // always legal, and is equivalent to `break ()`.
3754 e_ty = tcx.mk_nil();
3755 e_diverges = Diverges::Maybe;
3756 cause = self.misc(expr.span);
3759 // Now that we have type-checked `expr_opt`, borrow
3760 // the `enclosing_loops` field and let's coerce the
3761 // type of `expr_opt` into what is expected.
3762 let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
3763 let ctxt = enclosing_breakables.find_breakable(target_id);
3764 if let Some(ref mut coerce) = ctxt.coerce {
3765 if let Some(ref e) = *expr_opt {
3766 coerce.coerce(self, &cause, e, e_ty, e_diverges);
3768 assert!(e_ty.is_nil());
3769 coerce.coerce_forced_unit(self, &cause, &mut |_| (), true);
3772 // If `ctxt.coerce` is `None`, we can just ignore
3773 // the type of the expresison. This is because
3774 // either this was a break *without* a value, in
3775 // which case it is always a legal type (`()`), or
3776 // else an error would have been flagged by the
3777 // `loops` pass for using break with an expression
3778 // where you are not supposed to.
3779 assert!(expr_opt.is_none() || self.tcx.sess.err_count() > 0);
3782 ctxt.may_break = true;
3784 // Otherwise, we failed to find the enclosing loop;
3785 // this can only happen if the `break` was not
3786 // inside a loop at all, which is caught by the
3787 // loop-checking pass.
3788 assert!(self.tcx.sess.err_count() > 0);
3790 // We still need to assign a type to the inner expression to
3791 // prevent the ICE in #43162.
3792 if let Some(ref e) = *expr_opt {
3793 self.check_expr_with_hint(e, tcx.types.err);
3795 // ... except when we try to 'break rust;'.
3796 // ICE this expression in particular (see #43162).
3797 if let hir::ExprPath(hir::QPath::Resolved(_, ref path)) = e.node {
3798 if path.segments.len() == 1 && path.segments[0].name == "rust" {
3799 fatally_break_rust(self.tcx.sess);
3805 // the type of a `break` is always `!`, since it diverges
3808 hir::ExprAgain(_) => { tcx.types.never }
3809 hir::ExprRet(ref expr_opt) => {
3810 if self.ret_coercion.is_none() {
3811 struct_span_err!(self.tcx.sess, expr.span, E0572,
3812 "return statement outside of function body").emit();
3813 } else if let Some(ref e) = *expr_opt {
3814 self.check_return_expr(e);
3816 let mut coercion = self.ret_coercion.as_ref().unwrap().borrow_mut();
3817 let cause = self.cause(expr.span, ObligationCauseCode::ReturnNoExpression);
3818 coercion.coerce_forced_unit(self, &cause, &mut |_| (), true);
3822 hir::ExprAssign(ref lhs, ref rhs) => {
3823 let lhs_ty = self.check_expr_with_needs(&lhs, Needs::MutPlace);
3825 let rhs_ty = self.check_expr_coercable_to_type(&rhs, lhs_ty);
3828 ExpectIfCondition => {
3829 self.tcx.sess.delay_span_bug(lhs.span, "invalid lhs expression in if;\
3830 expected error elsehwere");
3833 // Only check this if not in an `if` condition, as the
3834 // mistyped comparison help is more appropriate.
3835 if !self.is_place_expr(&lhs) {
3836 struct_span_err!(self.tcx.sess, expr.span, E0070,
3837 "invalid left-hand side expression")
3838 .span_label(expr.span, "left-hand of expression not valid")
3844 self.require_type_is_sized(lhs_ty, lhs.span, traits::AssignmentLhsSized);
3846 if lhs_ty.references_error() || rhs_ty.references_error() {
3852 hir::ExprIf(ref cond, ref then_expr, ref opt_else_expr) => {
3853 self.check_then_else(&cond, then_expr, opt_else_expr.as_ref().map(|e| &**e),
3854 expr.span, expected)
3856 hir::ExprWhile(ref cond, ref body, _) => {
3857 let ctxt = BreakableCtxt {
3858 // cannot use break with a value from a while loop
3863 self.with_breakable_ctxt(expr.id, ctxt, || {
3864 self.check_expr_has_type_or_error(&cond, tcx.types.bool);
3865 let cond_diverging = self.diverges.get();
3866 self.check_block_no_value(&body);
3868 // We may never reach the body so it diverging means nothing.
3869 self.diverges.set(cond_diverging);
3874 hir::ExprLoop(ref body, _, source) => {
3875 let coerce = match source {
3876 // you can only use break with a value from a normal `loop { }`
3877 hir::LoopSource::Loop => {
3878 let coerce_to = expected.coercion_target_type(self, body.span);
3879 Some(CoerceMany::new(coerce_to))
3882 hir::LoopSource::WhileLet |
3883 hir::LoopSource::ForLoop => {
3888 let ctxt = BreakableCtxt {
3890 may_break: false, // will get updated if/when we find a `break`
3893 let (ctxt, ()) = self.with_breakable_ctxt(expr.id, ctxt, || {
3894 self.check_block_no_value(&body);
3898 // No way to know whether it's diverging because
3899 // of a `break` or an outer `break` or `return.
3900 self.diverges.set(Diverges::Maybe);
3903 // If we permit break with a value, then result type is
3904 // the LUB of the breaks (possibly ! if none); else, it
3905 // is nil. This makes sense because infinite loops
3906 // (which would have type !) are only possible iff we
3907 // permit break with a value [1].
3908 assert!(ctxt.coerce.is_some() || ctxt.may_break); // [1]
3909 ctxt.coerce.map(|c| c.complete(self)).unwrap_or(self.tcx.mk_nil())
3911 hir::ExprMatch(ref discrim, ref arms, match_src) => {
3912 self.check_match(expr, &discrim, arms, expected, match_src)
3914 hir::ExprClosure(capture, ref decl, body_id, _, gen) => {
3915 self.check_expr_closure(expr, capture, &decl, body_id, gen, expected)
3917 hir::ExprBlock(ref body) => {
3918 self.check_block_with_expected(&body, expected)
3920 hir::ExprCall(ref callee, ref args) => {
3921 self.check_call(expr, &callee, args, expected)
3923 hir::ExprMethodCall(ref segment, span, ref args) => {
3924 self.check_method_call(expr, segment, span, args, expected, needs)
3926 hir::ExprCast(ref e, ref t) => {
3927 // Find the type of `e`. Supply hints based on the type we are casting to,
3929 let t_cast = self.to_ty(t);
3930 let t_cast = self.resolve_type_vars_if_possible(&t_cast);
3931 let t_expr = self.check_expr_with_expectation(e, ExpectCastableToType(t_cast));
3932 let t_cast = self.resolve_type_vars_if_possible(&t_cast);
3934 // Eagerly check for some obvious errors.
3935 if t_expr.references_error() || t_cast.references_error() {
3938 // Defer other checks until we're done type checking.
3939 let mut deferred_cast_checks = self.deferred_cast_checks.borrow_mut();
3940 match cast::CastCheck::new(self, e, t_expr, t_cast, t.span, expr.span) {
3942 deferred_cast_checks.push(cast_check);
3945 Err(ErrorReported) => {
3951 hir::ExprType(ref e, ref t) => {
3952 let typ = self.to_ty(&t);
3953 self.check_expr_eq_type(&e, typ);
3956 hir::ExprArray(ref args) => {
3957 let uty = expected.to_option(self).and_then(|uty| {
3959 ty::TyArray(ty, _) | ty::TySlice(ty) => Some(ty),
3964 let element_ty = if !args.is_empty() {
3965 let coerce_to = uty.unwrap_or_else(
3966 || self.next_ty_var(TypeVariableOrigin::TypeInference(expr.span)));
3967 let mut coerce = CoerceMany::with_coercion_sites(coerce_to, args);
3968 assert_eq!(self.diverges.get(), Diverges::Maybe);
3970 let e_ty = self.check_expr_with_hint(e, coerce_to);
3971 let cause = self.misc(e.span);
3972 coerce.coerce(self, &cause, e, e_ty, self.diverges.get());
3974 coerce.complete(self)
3976 self.next_ty_var(TypeVariableOrigin::TypeInference(expr.span))
3978 tcx.mk_array(element_ty, args.len() as u64)
3980 hir::ExprRepeat(ref element, count) => {
3981 let count_def_id = tcx.hir.body_owner_def_id(count);
3982 let param_env = ty::ParamEnv::empty();
3983 let substs = Substs::identity_for_item(tcx.global_tcx(), count_def_id);
3984 let instance = ty::Instance::resolve(
3990 let global_id = GlobalId {
3994 let count = tcx.const_eval(param_env.and(global_id));
3996 if let Err(ref err) = count {
3997 err.report(tcx, tcx.def_span(count_def_id), "constant expression");
4000 let uty = match expected {
4001 ExpectHasType(uty) => {
4003 ty::TyArray(ty, _) | ty::TySlice(ty) => Some(ty),
4010 let (element_ty, t) = match uty {
4012 self.check_expr_coercable_to_type(&element, uty);
4016 let t: Ty = self.next_ty_var(TypeVariableOrigin::MiscVariable(element.span));
4017 let element_ty = self.check_expr_has_type_or_error(&element, t);
4022 if let Ok(count) = count {
4023 let zero_or_one = count.assert_usize(tcx).map_or(false, |count| count <= 1);
4025 // For [foo, ..n] where n > 1, `foo` must have
4027 let lang_item = self.tcx.require_lang_item(lang_items::CopyTraitLangItem);
4028 self.require_type_meets(t, expr.span, traits::RepeatVec, lang_item);
4032 if element_ty.references_error() {
4034 } else if let Ok(count) = count {
4035 tcx.mk_ty(ty::TyArray(t, count))
4040 hir::ExprTup(ref elts) => {
4041 let flds = expected.only_has_type(self).and_then(|ty| {
4042 let ty = self.resolve_type_vars_with_obligations(ty);
4044 ty::TyTuple(ref flds) => Some(&flds[..]),
4049 let elt_ts_iter = elts.iter().enumerate().map(|(i, e)| {
4050 let t = match flds {
4051 Some(ref fs) if i < fs.len() => {
4053 self.check_expr_coercable_to_type(&e, ety);
4057 self.check_expr_with_expectation(&e, NoExpectation)
4062 let tuple = tcx.mk_tup(elt_ts_iter);
4063 if tuple.references_error() {
4066 self.require_type_is_sized(tuple, expr.span, traits::TupleInitializerSized);
4070 hir::ExprStruct(ref qpath, ref fields, ref base_expr) => {
4071 self.check_expr_struct(expr, expected, qpath, fields, base_expr)
4073 hir::ExprField(ref base, ref field) => {
4074 self.check_field(expr, needs, &base, field)
4076 hir::ExprIndex(ref base, ref idx) => {
4077 let base_t = self.check_expr_with_needs(&base, needs);
4078 let idx_t = self.check_expr(&idx);
4080 if base_t.references_error() {
4082 } else if idx_t.references_error() {
4085 let base_t = self.structurally_resolved_type(expr.span, base_t);
4086 match self.lookup_indexing(expr, base, base_t, idx_t, needs) {
4087 Some((index_ty, element_ty)) => {
4088 // two-phase not needed because index_ty is never mutable
4089 self.demand_coerce(idx, idx_t, index_ty, AllowTwoPhase::No);
4093 let mut err = type_error_struct!(tcx.sess, expr.span, base_t, E0608,
4094 "cannot index into a value of type `{}`",
4096 // Try to give some advice about indexing tuples.
4097 if let ty::TyTuple(..) = base_t.sty {
4098 let mut needs_note = true;
4099 // If the index is an integer, we can show the actual
4100 // fixed expression:
4101 if let hir::ExprLit(ref lit) = idx.node {
4102 if let ast::LitKind::Int(i,
4103 ast::LitIntType::Unsuffixed) = lit.node {
4104 let snip = tcx.sess.codemap().span_to_snippet(base.span);
4105 if let Ok(snip) = snip {
4106 err.span_suggestion(expr.span,
4107 "to access tuple elements, use",
4108 format!("{}.{}", snip, i));
4114 err.help("to access tuple elements, use tuple indexing \
4115 syntax (e.g. `tuple.0`)");
4124 hir::ExprYield(ref value) => {
4125 match self.yield_ty {
4127 self.check_expr_coercable_to_type(&value, ty);
4130 struct_span_err!(self.tcx.sess, expr.span, E0627,
4131 "yield statement outside of generator literal").emit();
4139 // Finish resolving a path in a struct expression or pattern `S::A { .. }` if necessary.
4140 // The newly resolved definition is written into `type_dependent_defs`.
4141 fn finish_resolving_struct_path(&self,
4144 node_id: ast::NodeId)
4148 hir::QPath::Resolved(ref maybe_qself, ref path) => {
4149 let opt_self_ty = maybe_qself.as_ref().map(|qself| self.to_ty(qself));
4150 let ty = AstConv::def_to_ty(self, opt_self_ty, path, true);
4153 hir::QPath::TypeRelative(ref qself, ref segment) => {
4154 let ty = self.to_ty(qself);
4156 let def = if let hir::TyPath(hir::QPath::Resolved(_, ref path)) = qself.node {
4161 let (ty, def) = AstConv::associated_path_def_to_ty(self, node_id, path_span,
4164 // Write back the new resolution.
4165 let hir_id = self.tcx.hir.node_to_hir_id(node_id);
4166 self.tables.borrow_mut().type_dependent_defs_mut().insert(hir_id, def);
4173 // Resolve associated value path into a base type and associated constant or method definition.
4174 // The newly resolved definition is written into `type_dependent_defs`.
4175 pub fn resolve_ty_and_def_ufcs<'b>(&self,
4176 qpath: &'b hir::QPath,
4177 node_id: ast::NodeId,
4179 -> (Def, Option<Ty<'tcx>>, &'b [hir::PathSegment])
4181 let (ty, item_segment) = match *qpath {
4182 hir::QPath::Resolved(ref opt_qself, ref path) => {
4184 opt_qself.as_ref().map(|qself| self.to_ty(qself)),
4185 &path.segments[..]);
4187 hir::QPath::TypeRelative(ref qself, ref segment) => {
4188 (self.to_ty(qself), segment)
4191 let hir_id = self.tcx.hir.node_to_hir_id(node_id);
4192 if let Some(cached_def) = self.tables.borrow().type_dependent_defs().get(hir_id) {
4193 // Return directly on cache hit. This is useful to avoid doubly reporting
4194 // errors with default match binding modes. See #44614.
4195 return (*cached_def, Some(ty), slice::from_ref(&**item_segment))
4197 let item_name = item_segment.name;
4198 let def = match self.resolve_ufcs(span, item_name, ty, node_id) {
4201 let def = match error {
4202 method::MethodError::PrivateMatch(def, _) => def,
4205 if item_name != keywords::Invalid.name() {
4206 self.report_method_error(span, ty, item_name, None, error, None);
4212 // Write back the new resolution.
4213 self.tables.borrow_mut().type_dependent_defs_mut().insert(hir_id, def);
4214 (def, Some(ty), slice::from_ref(&**item_segment))
4217 pub fn check_decl_initializer(&self,
4218 local: &'gcx hir::Local,
4219 init: &'gcx hir::Expr) -> Ty<'tcx>
4221 // FIXME(tschottdorf): contains_explicit_ref_binding() must be removed
4222 // for #42640 (default match binding modes).
4225 let ref_bindings = local.pat.contains_explicit_ref_binding();
4227 let local_ty = self.local_ty(init.span, local.id);
4228 if let Some(m) = ref_bindings {
4229 // Somewhat subtle: if we have a `ref` binding in the pattern,
4230 // we want to avoid introducing coercions for the RHS. This is
4231 // both because it helps preserve sanity and, in the case of
4232 // ref mut, for soundness (issue #23116). In particular, in
4233 // the latter case, we need to be clear that the type of the
4234 // referent for the reference that results is *equal to* the
4235 // type of the place it is referencing, and not some
4236 // supertype thereof.
4237 let init_ty = self.check_expr_with_needs(init, Needs::maybe_mut_place(m));
4238 self.demand_eqtype(init.span, local_ty, init_ty);
4241 self.check_expr_coercable_to_type(init, local_ty)
4245 pub fn check_decl_local(&self, local: &'gcx hir::Local) {
4246 let t = self.local_ty(local.span, local.id);
4247 self.write_ty(local.hir_id, t);
4249 if let Some(ref init) = local.init {
4250 let init_ty = self.check_decl_initializer(local, &init);
4251 if init_ty.references_error() {
4252 self.write_ty(local.hir_id, init_ty);
4256 self.check_pat_walk(&local.pat, t,
4257 ty::BindingMode::BindByValue(hir::Mutability::MutImmutable),
4259 let pat_ty = self.node_ty(local.pat.hir_id);
4260 if pat_ty.references_error() {
4261 self.write_ty(local.hir_id, pat_ty);
4265 pub fn check_stmt(&self, stmt: &'gcx hir::Stmt) {
4266 // Don't do all the complex logic below for DeclItem.
4268 hir::StmtDecl(ref decl, _) => {
4270 hir::DeclLocal(_) => {}
4271 hir::DeclItem(_) => {
4276 hir::StmtExpr(..) | hir::StmtSemi(..) => {}
4279 self.warn_if_unreachable(stmt.node.id(), stmt.span, "statement");
4281 // Hide the outer diverging and has_errors flags.
4282 let old_diverges = self.diverges.get();
4283 let old_has_errors = self.has_errors.get();
4284 self.diverges.set(Diverges::Maybe);
4285 self.has_errors.set(false);
4288 hir::StmtDecl(ref decl, _) => {
4290 hir::DeclLocal(ref l) => {
4291 self.check_decl_local(&l);
4293 hir::DeclItem(_) => {/* ignore for now */}
4296 hir::StmtExpr(ref expr, _) => {
4297 // Check with expected type of ()
4298 self.check_expr_has_type_or_error(&expr, self.tcx.mk_nil());
4300 hir::StmtSemi(ref expr, _) => {
4301 self.check_expr(&expr);
4305 // Combine the diverging and has_error flags.
4306 self.diverges.set(self.diverges.get() | old_diverges);
4307 self.has_errors.set(self.has_errors.get() | old_has_errors);
4310 pub fn check_block_no_value(&self, blk: &'gcx hir::Block) {
4311 let unit = self.tcx.mk_nil();
4312 let ty = self.check_block_with_expected(blk, ExpectHasType(unit));
4314 // if the block produces a `!` value, that can always be
4315 // (effectively) coerced to unit.
4317 self.demand_suptype(blk.span, unit, ty);
4321 fn check_block_with_expected(&self,
4322 blk: &'gcx hir::Block,
4323 expected: Expectation<'tcx>) -> Ty<'tcx> {
4325 let mut fcx_ps = self.ps.borrow_mut();
4326 let unsafety_state = fcx_ps.recurse(blk);
4327 replace(&mut *fcx_ps, unsafety_state)
4330 // In some cases, blocks have just one exit, but other blocks
4331 // can be targeted by multiple breaks. This cannot happen in
4332 // normal Rust syntax today, but it can happen when we desugar
4333 // a `do catch { ... }` expression.
4337 // 'a: { if true { break 'a Err(()); } Ok(()) }
4339 // Here we would wind up with two coercions, one from
4340 // `Err(())` and the other from the tail expression
4341 // `Ok(())`. If the tail expression is omitted, that's a
4342 // "forced unit" -- unless the block diverges, in which
4343 // case we can ignore the tail expression (e.g., `'a: {
4344 // break 'a 22; }` would not force the type of the block
4346 let tail_expr = blk.expr.as_ref();
4347 let coerce_to_ty = expected.coercion_target_type(self, blk.span);
4348 let coerce = if blk.targeted_by_break {
4349 CoerceMany::new(coerce_to_ty)
4351 let tail_expr: &[P<hir::Expr>] = match tail_expr {
4352 Some(e) => slice::from_ref(e),
4355 CoerceMany::with_coercion_sites(coerce_to_ty, tail_expr)
4358 let prev_diverges = self.diverges.get();
4359 let ctxt = BreakableCtxt {
4360 coerce: Some(coerce),
4364 let (ctxt, ()) = self.with_breakable_ctxt(blk.id, ctxt, || {
4365 for s in &blk.stmts {
4369 // check the tail expression **without** holding the
4370 // `enclosing_breakables` lock below.
4371 let tail_expr_ty = tail_expr.map(|t| self.check_expr_with_expectation(t, expected));
4373 let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
4374 let ctxt = enclosing_breakables.find_breakable(blk.id);
4375 let coerce = ctxt.coerce.as_mut().unwrap();
4376 if let Some(tail_expr_ty) = tail_expr_ty {
4377 let tail_expr = tail_expr.unwrap();
4378 let cause = self.cause(tail_expr.span,
4379 ObligationCauseCode::BlockTailExpression(blk.id));
4384 self.diverges.get());
4386 // Subtle: if there is no explicit tail expression,
4387 // that is typically equivalent to a tail expression
4388 // of `()` -- except if the block diverges. In that
4389 // case, there is no value supplied from the tail
4390 // expression (assuming there are no other breaks,
4391 // this implies that the type of the block will be
4394 // #41425 -- label the implicit `()` as being the
4395 // "found type" here, rather than the "expected type".
4397 // #44579 -- if the block was recovered during parsing,
4398 // the type would be nonsensical and it is not worth it
4399 // to perform the type check, so we avoid generating the
4400 // diagnostic output.
4401 if !self.diverges.get().always() && !blk.recovered {
4402 coerce.coerce_forced_unit(self, &self.misc(blk.span), &mut |err| {
4403 if let Some(expected_ty) = expected.only_has_type(self) {
4404 self.consider_hint_about_removing_semicolon(blk,
4414 // If we can break from the block, then the block's exit is always reachable
4415 // (... as long as the entry is reachable) - regardless of the tail of the block.
4416 self.diverges.set(prev_diverges);
4419 let mut ty = ctxt.coerce.unwrap().complete(self);
4421 if self.has_errors.get() || ty.references_error() {
4422 ty = self.tcx.types.err
4425 self.write_ty(blk.hir_id, ty);
4427 *self.ps.borrow_mut() = prev;
4431 /// Given a `NodeId`, return the `FnDecl` of the method it is enclosed by and whether a
4432 /// suggestion can be made, `None` otherwise.
4433 pub fn get_fn_decl(&self, blk_id: ast::NodeId) -> Option<(hir::FnDecl, bool)> {
4434 // Get enclosing Fn, if it is a function or a trait method, unless there's a `loop` or
4435 // `while` before reaching it, as block tail returns are not available in them.
4436 if let Some(fn_id) = self.tcx.hir.get_return_block(blk_id) {
4437 let parent = self.tcx.hir.get(fn_id);
4439 if let Node::NodeItem(&hir::Item {
4440 name, node: hir::ItemFn(ref decl, ..), ..
4442 decl.clone().and_then(|decl| {
4443 // This is less than ideal, it will not suggest a return type span on any
4444 // method called `main`, regardless of whether it is actually the entry point,
4445 // but it will still present it as the reason for the expected type.
4446 Some((decl, name != Symbol::intern("main")))
4448 } else if let Node::NodeTraitItem(&hir::TraitItem {
4449 node: hir::TraitItemKind::Method(hir::MethodSig {
4453 decl.clone().and_then(|decl| {
4456 } else if let Node::NodeImplItem(&hir::ImplItem {
4457 node: hir::ImplItemKind::Method(hir::MethodSig {
4461 decl.clone().and_then(|decl| {
4472 /// On implicit return expressions with mismatched types, provide the following suggestions:
4474 /// - Point out the method's return type as the reason for the expected type
4475 /// - Possible missing semicolon
4476 /// - Possible missing return type if the return type is the default, and not `fn main()`
4477 pub fn suggest_mismatched_types_on_tail(&self,
4478 err: &mut DiagnosticBuilder<'tcx>,
4479 expression: &'gcx hir::Expr,
4483 blk_id: ast::NodeId) {
4484 self.suggest_missing_semicolon(err, expression, expected, cause_span);
4486 if let Some((fn_decl, can_suggest)) = self.get_fn_decl(blk_id) {
4487 self.suggest_missing_return_type(err, &fn_decl, expected, found, can_suggest);
4491 /// A common error is to forget to add a semicolon at the end of a block:
4495 /// bar_that_returns_u32()
4499 /// This routine checks if the return expression in a block would make sense on its own as a
4500 /// statement and the return type has been left as default or has been specified as `()`. If so,
4501 /// it suggests adding a semicolon.
4502 fn suggest_missing_semicolon(&self,
4503 err: &mut DiagnosticBuilder<'tcx>,
4504 expression: &'gcx hir::Expr,
4507 if expected.is_nil() {
4508 // `BlockTailExpression` only relevant if the tail expr would be
4509 // useful on its own.
4510 match expression.node {
4512 hir::ExprMethodCall(..) |
4514 hir::ExprWhile(..) |
4516 hir::ExprMatch(..) |
4517 hir::ExprBlock(..) => {
4518 let sp = self.tcx.sess.codemap().next_point(cause_span);
4519 err.span_suggestion(sp,
4520 "try adding a semicolon",
4529 /// A possible error is to forget to add a return type that is needed:
4533 /// bar_that_returns_u32()
4537 /// This routine checks if the return type is left as default, the method is not part of an
4538 /// `impl` block and that it isn't the `main` method. If so, it suggests setting the return
4540 fn suggest_missing_return_type(&self,
4541 err: &mut DiagnosticBuilder<'tcx>,
4542 fn_decl: &hir::FnDecl,
4545 can_suggest: bool) {
4546 // Only suggest changing the return type for methods that
4547 // haven't set a return type at all (and aren't `fn main()` or an impl).
4548 match (&fn_decl.output, found.is_suggestable(), can_suggest) {
4549 (&hir::FunctionRetTy::DefaultReturn(span), true, true) => {
4550 err.span_suggestion(span,
4551 "try adding a return type",
4553 self.resolve_type_vars_with_obligations(found)));
4555 (&hir::FunctionRetTy::DefaultReturn(span), false, true) => {
4556 err.span_label(span, "possibly return type missing here?");
4558 (&hir::FunctionRetTy::DefaultReturn(span), _, _) => {
4559 // `fn main()` must return `()`, do not suggest changing return type
4560 err.span_label(span, "expected `()` because of default return type");
4562 (&hir::FunctionRetTy::Return(ref ty), _, _) => {
4563 // Only point to return type if the expected type is the return type, as if they
4564 // are not, the expectation must have been caused by something else.
4565 debug!("suggest_missing_return_type: return type {:?} node {:?}", ty, ty.node);
4567 let ty = AstConv::ast_ty_to_ty(self, ty);
4568 debug!("suggest_missing_return_type: return type sty {:?}", ty.sty);
4569 debug!("suggest_missing_return_type: expected type sty {:?}", ty.sty);
4570 if ty.sty == expected.sty {
4571 err.span_label(sp, format!("expected `{}` because of return type",
4579 /// A common error is to add an extra semicolon:
4582 /// fn foo() -> usize {
4587 /// This routine checks if the final statement in a block is an
4588 /// expression with an explicit semicolon whose type is compatible
4589 /// with `expected_ty`. If so, it suggests removing the semicolon.
4590 fn consider_hint_about_removing_semicolon(&self,
4591 blk: &'gcx hir::Block,
4592 expected_ty: Ty<'tcx>,
4593 err: &mut DiagnosticBuilder) {
4594 // Be helpful when the user wrote `{... expr;}` and
4595 // taking the `;` off is enough to fix the error.
4596 let last_stmt = match blk.stmts.last() {
4600 let last_expr = match last_stmt.node {
4601 hir::StmtSemi(ref e, _) => e,
4604 let last_expr_ty = self.node_ty(last_expr.hir_id);
4605 if self.can_sub(self.param_env, last_expr_ty, expected_ty).is_err() {
4608 let original_span = original_sp(last_stmt.span, blk.span);
4609 let span_semi = original_span.with_lo(original_span.hi() - BytePos(1));
4610 err.span_suggestion(span_semi, "consider removing this semicolon", "".to_string());
4613 // Instantiates the given path, which must refer to an item with the given
4614 // number of type parameters and type.
4615 pub fn instantiate_value_path(&self,
4616 segments: &[hir::PathSegment],
4617 opt_self_ty: Option<Ty<'tcx>>,
4620 node_id: ast::NodeId)
4622 debug!("instantiate_value_path(path={:?}, def={:?}, node_id={})",
4627 // We need to extract the type parameters supplied by the user in
4628 // the path `path`. Due to the current setup, this is a bit of a
4629 // tricky-process; the problem is that resolve only tells us the
4630 // end-point of the path resolution, and not the intermediate steps.
4631 // Luckily, we can (at least for now) deduce the intermediate steps
4632 // just from the end-point.
4634 // There are basically four cases to consider:
4636 // 1. Reference to a constructor of enum variant or struct:
4638 // struct Foo<T>(...)
4639 // enum E<T> { Foo(...) }
4641 // In these cases, the parameters are declared in the type
4644 // 2. Reference to a fn item or a free constant:
4648 // In this case, the path will again always have the form
4649 // `a::b::foo::<T>` where only the final segment should have
4650 // type parameters. However, in this case, those parameters are
4651 // declared on a value, and hence are in the `FnSpace`.
4653 // 3. Reference to a method or an associated constant:
4655 // impl<A> SomeStruct<A> {
4659 // Here we can have a path like
4660 // `a::b::SomeStruct::<A>::foo::<B>`, in which case parameters
4661 // may appear in two places. The penultimate segment,
4662 // `SomeStruct::<A>`, contains parameters in TypeSpace, and the
4663 // final segment, `foo::<B>` contains parameters in fn space.
4665 // 4. Reference to a local variable
4667 // Local variables can't have any type parameters.
4669 // The first step then is to categorize the segments appropriately.
4671 assert!(!segments.is_empty());
4673 let mut ufcs_associated = None;
4674 let mut type_segment = None;
4675 let mut fn_segment = None;
4677 // Case 1. Reference to a struct/variant constructor.
4678 Def::StructCtor(def_id, ..) |
4679 Def::VariantCtor(def_id, ..) => {
4680 // Everything but the final segment should have no
4681 // parameters at all.
4682 let mut generics = self.tcx.generics_of(def_id);
4683 if let Some(def_id) = generics.parent {
4684 // Variant and struct constructors use the
4685 // generics of their parent type definition.
4686 generics = self.tcx.generics_of(def_id);
4688 type_segment = Some((segments.last().unwrap(), generics));
4691 // Case 2. Reference to a top-level value.
4693 Def::Const(def_id) |
4694 Def::Static(def_id, _) => {
4695 fn_segment = Some((segments.last().unwrap(),
4696 self.tcx.generics_of(def_id)));
4699 // Case 3. Reference to a method or associated const.
4700 Def::Method(def_id) |
4701 Def::AssociatedConst(def_id) => {
4702 let container = self.tcx.associated_item(def_id).container;
4704 ty::TraitContainer(trait_did) => {
4705 callee::check_legal_trait_for_method_call(self.tcx, span, trait_did)
4707 ty::ImplContainer(_) => {}
4710 let generics = self.tcx.generics_of(def_id);
4711 if segments.len() >= 2 {
4712 let parent_generics = self.tcx.generics_of(generics.parent.unwrap());
4713 type_segment = Some((&segments[segments.len() - 2], parent_generics));
4715 // `<T>::assoc` will end up here, and so can `T::assoc`.
4716 let self_ty = opt_self_ty.expect("UFCS sugared assoc missing Self");
4717 ufcs_associated = Some((container, self_ty));
4719 fn_segment = Some((segments.last().unwrap(), generics));
4722 // Case 4. Local variable, no generics.
4723 Def::Local(..) | Def::Upvar(..) => {}
4725 _ => bug!("unexpected definition: {:?}", def),
4728 debug!("type_segment={:?} fn_segment={:?}", type_segment, fn_segment);
4730 // Now that we have categorized what space the parameters for each
4731 // segment belong to, let's sort out the parameters that the user
4732 // provided (if any) into their appropriate spaces. We'll also report
4733 // errors if type parameters are provided in an inappropriate place.
4734 let poly_segments = type_segment.is_some() as usize +
4735 fn_segment.is_some() as usize;
4736 AstConv::prohibit_type_params(self, &segments[..segments.len() - poly_segments]);
4739 Def::Local(nid) | Def::Upvar(nid, ..) => {
4740 let ty = self.local_ty(span, nid);
4741 let ty = self.normalize_associated_types_in(span, &ty);
4742 self.write_ty(self.tcx.hir.node_to_hir_id(node_id), ty);
4748 // Now we have to compare the types that the user *actually*
4749 // provided against the types that were *expected*. If the user
4750 // did not provide any types, then we want to substitute inference
4751 // variables. If the user provided some types, we may still need
4752 // to add defaults. If the user provided *too many* types, that's
4754 let supress_mismatch = self.check_impl_trait(span, &mut fn_segment);
4755 self.check_path_parameter_count(span, &mut type_segment, false, supress_mismatch);
4756 self.check_path_parameter_count(span, &mut fn_segment, false, supress_mismatch);
4758 let (fn_start, has_self) = match (type_segment, fn_segment) {
4759 (_, Some((_, generics))) => {
4760 (generics.parent_count(), generics.has_self)
4762 (Some((_, generics)), None) => {
4763 (generics.own_count(), generics.has_self)
4765 (None, None) => (0, false)
4767 let substs = Substs::for_item(self.tcx, def.def_id(), |def, _| {
4768 let mut i = def.index as usize;
4770 let segment = if i < fn_start {
4771 i -= has_self as usize;
4777 let lifetimes = segment.map_or(&[][..], |(s, _)| {
4778 s.parameters.as_ref().map_or(&[][..], |p| &p.lifetimes[..])
4781 if let Some(lifetime) = lifetimes.get(i) {
4782 AstConv::ast_region_to_region(self, lifetime, Some(def))
4784 self.re_infer(span, Some(def)).unwrap()
4787 let mut i = def.index as usize;
4789 let segment = if i < fn_start {
4790 // Handle Self first, so we can adjust the index to match the AST.
4791 if has_self && i == 0 {
4792 return opt_self_ty.unwrap_or_else(|| {
4793 self.type_var_for_def(span, def)
4796 i -= has_self as usize;
4802 let (types, infer_types) = segment.map_or((&[][..], true), |(s, _)| {
4803 (s.parameters.as_ref().map_or(&[][..], |p| &p.types[..]), s.infer_types)
4806 // Skip over the lifetimes in the same segment.
4807 if let Some((_, generics)) = segment {
4808 i -= generics.regions.len();
4811 if let Some(ast_ty) = types.get(i) {
4812 // A provided type parameter.
4814 } else if !infer_types && def.has_default {
4815 // No type parameter provided, but a default exists.
4816 let default = self.tcx.type_of(def.def_id);
4819 default.subst_spanned(self.tcx, substs, Some(span))
4822 // No type parameters were provided, we can infer all.
4823 // This can also be reached in some error cases:
4824 // We prefer to use inference variables instead of
4825 // TyError to let type inference recover somewhat.
4826 self.type_var_for_def(span, def)
4830 // The things we are substituting into the type should not contain
4831 // escaping late-bound regions, and nor should the base type scheme.
4832 let ty = self.tcx.type_of(def.def_id());
4833 assert!(!substs.has_escaping_regions());
4834 assert!(!ty.has_escaping_regions());
4836 // Add all the obligations that are required, substituting and
4837 // normalized appropriately.
4838 let bounds = self.instantiate_bounds(span, def.def_id(), &substs);
4839 self.add_obligations_for_parameters(
4840 traits::ObligationCause::new(span, self.body_id, traits::ItemObligation(def.def_id())),
4843 // Substitute the values for the type parameters into the type of
4844 // the referenced item.
4845 let ty_substituted = self.instantiate_type_scheme(span, &substs, &ty);
4847 if let Some((ty::ImplContainer(impl_def_id), self_ty)) = ufcs_associated {
4848 // In the case of `Foo<T>::method` and `<Foo<T>>::method`, if `method`
4849 // is inherent, there is no `Self` parameter, instead, the impl needs
4850 // type parameters, which we can infer by unifying the provided `Self`
4851 // with the substituted impl type.
4852 let ty = self.tcx.type_of(impl_def_id);
4854 let impl_ty = self.instantiate_type_scheme(span, &substs, &ty);
4855 match self.at(&self.misc(span), self.param_env).sup(impl_ty, self_ty) {
4856 Ok(ok) => self.register_infer_ok_obligations(ok),
4859 "instantiate_value_path: (UFCS) {:?} was a subtype of {:?} but now is not?",
4866 self.check_rustc_args_require_const(def.def_id(), node_id, span);
4868 debug!("instantiate_value_path: type of {:?} is {:?}",
4871 self.write_substs(self.tcx.hir.node_to_hir_id(node_id), substs);
4875 fn check_rustc_args_require_const(&self,
4877 node_id: ast::NodeId,
4879 // We're only interested in functions tagged with
4880 // #[rustc_args_required_const], so ignore anything that's not.
4881 if !self.tcx.has_attr(def_id, "rustc_args_required_const") {
4885 // If our calling expression is indeed the function itself, we're good!
4886 // If not, generate an error that this can only be called directly.
4887 match self.tcx.hir.get(self.tcx.hir.get_parent_node(node_id)) {
4888 Node::NodeExpr(expr) => {
4890 hir::ExprCall(ref callee, ..) => {
4891 if callee.id == node_id {
4901 self.tcx.sess.span_err(span, "this function can only be invoked \
4902 directly, not through a function pointer");
4905 /// Report errors if the provided parameters are too few or too many.
4906 fn check_path_parameter_count(&self,
4908 segment: &mut Option<(&hir::PathSegment, &ty::Generics)>,
4909 is_method_call: bool,
4910 supress_mismatch_error: bool) {
4911 let (lifetimes, types, infer_types, bindings) = segment.map_or(
4912 (&[][..], &[][..], true, &[][..]),
4913 |(s, _)| s.parameters.as_ref().map_or(
4914 (&[][..], &[][..], s.infer_types, &[][..]),
4915 |p| (&p.lifetimes[..], &p.types[..],
4916 s.infer_types, &p.bindings[..])));
4917 let infer_lifetimes = lifetimes.len() == 0;
4919 let count_lifetime_params = |n| {
4920 format!("{} lifetime parameter{}", n, if n == 1 { "" } else { "s" })
4922 let count_type_params = |n| {
4923 format!("{} type parameter{}", n, if n == 1 { "" } else { "s" })
4926 // Check provided type parameters.
4927 let type_defs = segment.map_or(&[][..], |(_, generics)| {
4928 if generics.parent.is_none() {
4929 &generics.types[generics.has_self as usize..]
4934 let required_len = type_defs.iter().take_while(|d| !d.has_default).count();
4935 if types.len() > type_defs.len() {
4936 let span = types[type_defs.len()].span;
4937 let expected_text = count_type_params(type_defs.len());
4938 let actual_text = count_type_params(types.len());
4939 struct_span_err!(self.tcx.sess, span, E0087,
4940 "too many type parameters provided: \
4941 expected at most {}, found {}",
4942 expected_text, actual_text)
4943 .span_label(span, format!("expected {}", expected_text))
4946 // To prevent derived errors to accumulate due to extra
4947 // type parameters, we force instantiate_value_path to
4948 // use inference variables instead of the provided types.
4950 } else if types.len() < required_len && !infer_types && !supress_mismatch_error {
4951 let expected_text = count_type_params(required_len);
4952 let actual_text = count_type_params(types.len());
4953 struct_span_err!(self.tcx.sess, span, E0089,
4954 "too few type parameters provided: \
4955 expected {}, found {}",
4956 expected_text, actual_text)
4957 .span_label(span, format!("expected {}", expected_text))
4961 if !bindings.is_empty() {
4962 AstConv::prohibit_projection(self, bindings[0].span);
4965 // Check provided lifetime parameters.
4966 let lifetime_defs = segment.map_or(&[][..], |(_, generics)| &generics.regions);
4967 let required_len = lifetime_defs.len();
4969 // Prohibit explicit lifetime arguments if late bound lifetime parameters are present.
4970 let has_late_bound_lifetime_defs =
4971 segment.map_or(None, |(_, generics)| generics.has_late_bound_regions);
4972 if let (Some(span_late), false) = (has_late_bound_lifetime_defs, lifetimes.is_empty()) {
4973 // Report this as a lint only if no error was reported previously.
4974 let primary_msg = "cannot specify lifetime arguments explicitly \
4975 if late bound lifetime parameters are present";
4976 let note_msg = "the late bound lifetime parameter is introduced here";
4977 if !is_method_call && (lifetimes.len() > lifetime_defs.len() ||
4978 lifetimes.len() < required_len && !infer_lifetimes) {
4979 let mut err = self.tcx.sess.struct_span_err(lifetimes[0].span, primary_msg);
4980 err.span_note(span_late, note_msg);
4984 let mut multispan = MultiSpan::from_span(lifetimes[0].span);
4985 multispan.push_span_label(span_late, note_msg.to_string());
4986 self.tcx.lint_node(lint::builtin::LATE_BOUND_LIFETIME_ARGUMENTS,
4987 lifetimes[0].id, multispan, primary_msg);
4992 if lifetimes.len() > lifetime_defs.len() {
4993 let span = lifetimes[lifetime_defs.len()].span;
4994 let expected_text = count_lifetime_params(lifetime_defs.len());
4995 let actual_text = count_lifetime_params(lifetimes.len());
4996 struct_span_err!(self.tcx.sess, span, E0088,
4997 "too many lifetime parameters provided: \
4998 expected at most {}, found {}",
4999 expected_text, actual_text)
5000 .span_label(span, format!("expected {}", expected_text))
5002 } else if lifetimes.len() < required_len && !infer_lifetimes {
5003 let expected_text = count_lifetime_params(lifetime_defs.len());
5004 let actual_text = count_lifetime_params(lifetimes.len());
5005 struct_span_err!(self.tcx.sess, span, E0090,
5006 "too few lifetime parameters provided: \
5007 expected {}, found {}",
5008 expected_text, actual_text)
5009 .span_label(span, format!("expected {}", expected_text))
5014 /// Report error if there is an explicit type parameter when using `impl Trait`.
5015 fn check_impl_trait(&self,
5017 segment: &mut Option<(&hir::PathSegment, &ty::Generics)>)
5019 use hir::SyntheticTyParamKind::*;
5021 let segment = segment.map(|(path_segment, generics)| {
5022 let explicit = !path_segment.infer_types;
5023 let impl_trait = generics.types.iter()
5025 match ty_param.synthetic {
5026 Some(ImplTrait) => true,
5031 if explicit && impl_trait {
5032 let mut err = struct_span_err! {
5036 "cannot provide explicit type parameters when `impl Trait` is \
5037 used in argument position."
5046 segment.unwrap_or(false)
5049 // Resolves `typ` by a single level if `typ` is a type variable.
5050 // If no resolution is possible, then an error is reported.
5051 // Numeric inference variables may be left unresolved.
5052 pub fn structurally_resolved_type(&self, sp: Span, ty: Ty<'tcx>) -> Ty<'tcx> {
5053 let ty = self.resolve_type_vars_with_obligations(ty);
5054 if !ty.is_ty_var() {
5057 if !self.is_tainted_by_errors() {
5058 self.need_type_info((**self).body_id, sp, ty);
5060 self.demand_suptype(sp, self.tcx.types.err, ty);
5065 fn with_breakable_ctxt<F: FnOnce() -> R, R>(&self, id: ast::NodeId,
5066 ctxt: BreakableCtxt<'gcx, 'tcx>, f: F)
5067 -> (BreakableCtxt<'gcx, 'tcx>, R) {
5070 let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
5071 index = enclosing_breakables.stack.len();
5072 enclosing_breakables.by_id.insert(id, index);
5073 enclosing_breakables.stack.push(ctxt);
5077 let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
5078 debug_assert!(enclosing_breakables.stack.len() == index + 1);
5079 enclosing_breakables.by_id.remove(&id).expect("missing breakable context");
5080 enclosing_breakables.stack.pop().expect("missing breakable context")
5086 pub fn check_bounds_are_used<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
5087 generics: &hir::Generics,
5089 debug!("check_bounds_are_used(n_tps={}, ty={:?})",
5090 generics.ty_params().count(), ty);
5092 // make a vector of booleans initially false, set to true when used
5093 if generics.ty_params().next().is_none() { return; }
5094 let mut tps_used = vec![false; generics.ty_params().count()];
5096 let lifetime_count = generics.lifetimes().count();
5098 for leaf_ty in ty.walk() {
5099 if let ty::TyParam(ty::ParamTy {idx, ..}) = leaf_ty.sty {
5100 debug!("Found use of ty param num {}", idx);
5101 tps_used[idx as usize - lifetime_count] = true;
5102 } else if let ty::TyError = leaf_ty.sty {
5103 // If there already another error, do not emit an error for not using a type Parameter
5104 assert!(tcx.sess.err_count() > 0);
5109 for (&used, param) in tps_used.iter().zip(generics.ty_params()) {
5111 struct_span_err!(tcx.sess, param.span, E0091,
5112 "type parameter `{}` is unused",
5114 .span_label(param.span, "unused type parameter")
5120 fn fatally_break_rust(sess: &Session) {
5121 let handler = sess.diagnostic();
5122 handler.span_bug_no_panic(
5124 "It looks like you're trying to break rust; would you like some ICE?",
5126 handler.note_without_error("the compiler expectedly panicked. this is a feature.");
5127 handler.note_without_error(
5128 "we would appreciate a joke overview: \
5129 https://github.com/rust-lang/rust/issues/43162#issuecomment-320764675"
5131 handler.note_without_error(&format!("rustc {} running on {}",
5132 option_env!("CFG_VERSION").unwrap_or("unknown_version"),
5133 ::session::config::host_triple(),