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::*;
88 use fmt_macros::{Parser, Piece, Position};
89 use hir::def::{Def, CtorKind};
90 use hir::def_id::{CrateNum, DefId, LOCAL_CRATE};
91 use rustc_back::slice::ref_slice;
92 use rustc::infer::{self, InferCtxt, InferOk, RegionVariableOrigin};
93 use rustc::infer::type_variable::{TypeVariableOrigin};
94 use rustc::middle::region::CodeExtent;
95 use rustc::ty::subst::{Kind, Subst, Substs};
96 use rustc::traits::{self, FulfillmentContext, ObligationCause, ObligationCauseCode};
97 use rustc::ty::{ParamTy, LvaluePreference, NoPreference, PreferMutLvalue};
98 use rustc::ty::{self, Ty, TyCtxt, Visibility};
99 use rustc::ty::adjustment::{Adjust, Adjustment, AutoBorrow};
100 use rustc::ty::fold::{BottomUpFolder, TypeFoldable};
101 use rustc::ty::maps::Providers;
102 use rustc::ty::util::{Representability, IntTypeExt};
103 use errors::DiagnosticBuilder;
104 use require_c_abi_if_variadic;
105 use session::{Session, CompileResult};
108 use util::common::{ErrorReported, indenter};
109 use util::nodemap::{DefIdMap, FxHashMap, NodeMap};
111 use std::cell::{Cell, RefCell};
112 use std::collections::hash_map::Entry;
114 use std::mem::replace;
115 use std::ops::{self, Deref};
116 use syntax::abi::Abi;
118 use syntax::codemap::{self, original_sp, Spanned};
119 use syntax::feature_gate::{GateIssue, emit_feature_err};
121 use syntax::symbol::{Symbol, InternedString, keywords};
122 use syntax::util::lev_distance::find_best_match_for_name;
123 use syntax_pos::{self, BytePos, Span, DUMMY_SP};
125 use rustc::hir::intravisit::{self, Visitor, NestedVisitorMap};
126 use rustc::hir::itemlikevisit::ItemLikeVisitor;
127 use rustc::hir::{self, PatKind};
128 use rustc::middle::lang_items;
129 use rustc_back::slice;
130 use rustc::middle::const_val::eval_length;
131 use rustc_const_math::ConstInt;
150 /// closures defined within the function. For example:
153 /// bar(move|| { ... })
156 /// Here, the function `foo()` and the closure passed to
157 /// `bar()` will each have their own `FnCtxt`, but they will
158 /// share the inherited fields.
159 pub struct Inherited<'a, 'gcx: 'a+'tcx, 'tcx: 'a> {
160 infcx: InferCtxt<'a, 'gcx, 'tcx>,
162 locals: RefCell<NodeMap<Ty<'tcx>>>,
164 fulfillment_cx: RefCell<traits::FulfillmentContext<'tcx>>,
166 // When we process a call like `c()` where `c` is a closure type,
167 // we may not have decided yet whether `c` is a `Fn`, `FnMut`, or
168 // `FnOnce` closure. In that case, we defer full resolution of the
169 // call until upvar inference can kick in and make the
170 // decision. We keep these deferred resolutions grouped by the
171 // def-id of the closure, so that once we decide, we can easily go
172 // back and process them.
173 deferred_call_resolutions: RefCell<DefIdMap<Vec<DeferredCallResolution<'gcx, 'tcx>>>>,
175 deferred_cast_checks: RefCell<Vec<cast::CastCheck<'tcx>>>,
177 // Anonymized types found in explicit return types and their
178 // associated fresh inference variable. Writeback resolves these
179 // variables to get the concrete type, which can be used to
180 // deanonymize TyAnon, after typeck is done with all functions.
181 anon_types: RefCell<NodeMap<Ty<'tcx>>>,
183 /// Each type parameter has an implicit region bound that
184 /// indicates it must outlive at least the function body (the user
185 /// may specify stronger requirements). This field indicates the
186 /// region of the callee. If it is `None`, then the parameter
187 /// environment is for an item or something where the "callee" is
189 implicit_region_bound: Option<ty::Region<'tcx>>,
192 impl<'a, 'gcx, 'tcx> Deref for Inherited<'a, 'gcx, 'tcx> {
193 type Target = InferCtxt<'a, 'gcx, 'tcx>;
194 fn deref(&self) -> &Self::Target {
199 /// When type-checking an expression, we propagate downward
200 /// whatever type hint we are able in the form of an `Expectation`.
201 #[derive(Copy, Clone, Debug)]
202 pub enum Expectation<'tcx> {
203 /// We know nothing about what type this expression should have.
206 /// This expression should have the type given (or some subtype)
207 ExpectHasType(Ty<'tcx>),
209 /// This expression will be cast to the `Ty`
210 ExpectCastableToType(Ty<'tcx>),
212 /// This rvalue expression will be wrapped in `&` or `Box` and coerced
213 /// to `&Ty` or `Box<Ty>`, respectively. `Ty` is `[A]` or `Trait`.
214 ExpectRvalueLikeUnsized(Ty<'tcx>),
217 impl<'a, 'gcx, 'tcx> Expectation<'tcx> {
218 // Disregard "castable to" expectations because they
219 // can lead us astray. Consider for example `if cond
220 // {22} else {c} as u8` -- if we propagate the
221 // "castable to u8" constraint to 22, it will pick the
222 // type 22u8, which is overly constrained (c might not
223 // be a u8). In effect, the problem is that the
224 // "castable to" expectation is not the tightest thing
225 // we can say, so we want to drop it in this case.
226 // The tightest thing we can say is "must unify with
227 // else branch". Note that in the case of a "has type"
228 // constraint, this limitation does not hold.
230 // If the expected type is just a type variable, then don't use
231 // an expected type. Otherwise, we might write parts of the type
232 // when checking the 'then' block which are incompatible with the
234 fn adjust_for_branches(&self, fcx: &FnCtxt<'a, 'gcx, 'tcx>) -> Expectation<'tcx> {
236 ExpectHasType(ety) => {
237 let ety = fcx.shallow_resolve(ety);
238 if !ety.is_ty_var() {
244 ExpectRvalueLikeUnsized(ety) => {
245 ExpectRvalueLikeUnsized(ety)
251 /// Provide an expectation for an rvalue expression given an *optional*
252 /// hint, which is not required for type safety (the resulting type might
253 /// be checked higher up, as is the case with `&expr` and `box expr`), but
254 /// is useful in determining the concrete type.
256 /// The primary use case is where the expected type is a fat pointer,
257 /// like `&[isize]`. For example, consider the following statement:
259 /// let x: &[isize] = &[1, 2, 3];
261 /// In this case, the expected type for the `&[1, 2, 3]` expression is
262 /// `&[isize]`. If however we were to say that `[1, 2, 3]` has the
263 /// expectation `ExpectHasType([isize])`, that would be too strong --
264 /// `[1, 2, 3]` does not have the type `[isize]` but rather `[isize; 3]`.
265 /// It is only the `&[1, 2, 3]` expression as a whole that can be coerced
266 /// to the type `&[isize]`. Therefore, we propagate this more limited hint,
267 /// which still is useful, because it informs integer literals and the like.
268 /// See the test case `test/run-pass/coerce-expect-unsized.rs` and #20169
269 /// for examples of where this comes up,.
270 fn rvalue_hint(fcx: &FnCtxt<'a, 'gcx, 'tcx>, ty: Ty<'tcx>) -> Expectation<'tcx> {
271 match fcx.tcx.struct_tail(ty).sty {
272 ty::TySlice(_) | ty::TyStr | ty::TyDynamic(..) => {
273 ExpectRvalueLikeUnsized(ty)
275 _ => ExpectHasType(ty)
279 // Resolves `expected` by a single level if it is a variable. If
280 // there is no expected type or resolution is not possible (e.g.,
281 // no constraints yet present), just returns `None`.
282 fn resolve(self, fcx: &FnCtxt<'a, 'gcx, 'tcx>) -> Expectation<'tcx> {
287 ExpectCastableToType(t) => {
288 ExpectCastableToType(fcx.resolve_type_vars_if_possible(&t))
290 ExpectHasType(t) => {
291 ExpectHasType(fcx.resolve_type_vars_if_possible(&t))
293 ExpectRvalueLikeUnsized(t) => {
294 ExpectRvalueLikeUnsized(fcx.resolve_type_vars_if_possible(&t))
299 fn to_option(self, fcx: &FnCtxt<'a, 'gcx, 'tcx>) -> Option<Ty<'tcx>> {
300 match self.resolve(fcx) {
301 NoExpectation => None,
302 ExpectCastableToType(ty) |
304 ExpectRvalueLikeUnsized(ty) => Some(ty),
308 /// It sometimes happens that we want to turn an expectation into
309 /// a **hard constraint** (i.e., something that must be satisfied
310 /// for the program to type-check). `only_has_type` will return
311 /// such a constraint, if it exists.
312 fn only_has_type(self, fcx: &FnCtxt<'a, 'gcx, 'tcx>) -> Option<Ty<'tcx>> {
313 match self.resolve(fcx) {
314 ExpectHasType(ty) => Some(ty),
319 /// Like `only_has_type`, but instead of returning `None` if no
320 /// hard constraint exists, creates a fresh type variable.
321 fn coercion_target_type(self, fcx: &FnCtxt<'a, 'gcx, 'tcx>, span: Span) -> Ty<'tcx> {
322 self.only_has_type(fcx)
323 .unwrap_or_else(|| fcx.next_ty_var(TypeVariableOrigin::MiscVariable(span)))
327 #[derive(Copy, Clone)]
328 pub struct UnsafetyState {
329 pub def: ast::NodeId,
330 pub unsafety: hir::Unsafety,
331 pub unsafe_push_count: u32,
336 pub fn function(unsafety: hir::Unsafety, def: ast::NodeId) -> UnsafetyState {
337 UnsafetyState { def: def, unsafety: unsafety, unsafe_push_count: 0, from_fn: true }
340 pub fn recurse(&mut self, blk: &hir::Block) -> UnsafetyState {
341 match self.unsafety {
342 // If this unsafe, then if the outer function was already marked as
343 // unsafe we shouldn't attribute the unsafe'ness to the block. This
344 // way the block can be warned about instead of ignoring this
345 // extraneous block (functions are never warned about).
346 hir::Unsafety::Unsafe if self.from_fn => *self,
349 let (unsafety, def, count) = match blk.rules {
350 hir::PushUnsafeBlock(..) =>
351 (unsafety, blk.id, self.unsafe_push_count.checked_add(1).unwrap()),
352 hir::PopUnsafeBlock(..) =>
353 (unsafety, blk.id, self.unsafe_push_count.checked_sub(1).unwrap()),
354 hir::UnsafeBlock(..) =>
355 (hir::Unsafety::Unsafe, blk.id, self.unsafe_push_count),
357 (unsafety, self.def, self.unsafe_push_count),
359 UnsafetyState{ def: def,
361 unsafe_push_count: count,
368 #[derive(Debug, Copy, Clone)]
374 /// Tracks whether executing a node may exit normally (versus
375 /// return/break/panic, which "diverge", leaving dead code in their
376 /// wake). Tracked semi-automatically (through type variables marked
377 /// as diverging), with some manual adjustments for control-flow
378 /// primitives (approximating a CFG).
379 #[derive(Copy, Clone, Debug, PartialEq, Eq, PartialOrd, Ord)]
381 /// Potentially unknown, some cases converge,
382 /// others require a CFG to determine them.
385 /// Definitely known to diverge and therefore
386 /// not reach the next sibling or its parent.
389 /// Same as `Always` but with a reachability
390 /// warning already emitted
394 // Convenience impls for combinig `Diverges`.
396 impl ops::BitAnd for Diverges {
398 fn bitand(self, other: Self) -> Self {
399 cmp::min(self, other)
403 impl ops::BitOr for Diverges {
405 fn bitor(self, other: Self) -> Self {
406 cmp::max(self, other)
410 impl ops::BitAndAssign for Diverges {
411 fn bitand_assign(&mut self, other: Self) {
412 *self = *self & other;
416 impl ops::BitOrAssign for Diverges {
417 fn bitor_assign(&mut self, other: Self) {
418 *self = *self | other;
423 fn always(self) -> bool {
424 self >= Diverges::Always
428 pub struct BreakableCtxt<'gcx: 'tcx, 'tcx> {
431 // this is `null` for loops where break with a value is illegal,
432 // such as `while`, `for`, and `while let`
433 coerce: Option<DynamicCoerceMany<'gcx, 'tcx>>,
436 pub struct EnclosingBreakables<'gcx: 'tcx, 'tcx> {
437 stack: Vec<BreakableCtxt<'gcx, 'tcx>>,
438 by_id: NodeMap<usize>,
441 impl<'gcx, 'tcx> EnclosingBreakables<'gcx, 'tcx> {
442 fn find_breakable(&mut self, target_id: ast::NodeId) -> &mut BreakableCtxt<'gcx, 'tcx> {
443 let ix = *self.by_id.get(&target_id).unwrap_or_else(|| {
444 bug!("could not find enclosing breakable with id {}", target_id);
450 pub struct FnCtxt<'a, 'gcx: 'a+'tcx, 'tcx: 'a> {
451 body_id: ast::NodeId,
453 // Number of errors that had been reported when we started
454 // checking this function. On exit, if we find that *more* errors
455 // have been reported, we will skip regionck and other work that
456 // expects the types within the function to be consistent.
457 err_count_on_creation: usize,
459 ret_coercion: Option<RefCell<DynamicCoerceMany<'gcx, 'tcx>>>,
461 ps: RefCell<UnsafetyState>,
463 /// Whether the last checked node generates a divergence (e.g.,
464 /// `return` will set this to Always). In general, when entering
465 /// an expression or other node in the tree, the initial value
466 /// indicates whether prior parts of the containing expression may
467 /// have diverged. It is then typically set to `Maybe` (and the
468 /// old value remembered) for processing the subparts of the
469 /// current expression. As each subpart is processed, they may set
470 /// the flag to `Always` etc. Finally, at the end, we take the
471 /// result and "union" it with the original value, so that when we
472 /// return the flag indicates if any subpart of the the parent
473 /// expression (up to and including this part) has diverged. So,
474 /// if you read it after evaluating a subexpression `X`, the value
475 /// you get indicates whether any subexpression that was
476 /// evaluating up to and including `X` diverged.
478 /// We use this flag for two purposes:
480 /// - To warn about unreachable code: if, after processing a
481 /// sub-expression but before we have applied the effects of the
482 /// current node, we see that the flag is set to `Always`, we
483 /// can issue a warning. This corresponds to something like
484 /// `foo(return)`; we warn on the `foo()` expression. (We then
485 /// update the flag to `WarnedAlways` to suppress duplicate
486 /// reports.) Similarly, if we traverse to a fresh statement (or
487 /// tail expression) from a `Always` setting, we will isssue a
488 /// warning. This corresponds to something like `{return;
489 /// foo();}` or `{return; 22}`, where we would warn on the
492 /// - To permit assignment into a local variable or other lvalue
493 /// (including the "return slot") of type `!`. This is allowed
494 /// if **either** the type of value being assigned is `!`, which
495 /// means the current code is dead, **or** the expression's
496 /// divering flag is true, which means that a divering value was
497 /// wrapped (e.g., `let x: ! = foo(return)`).
499 /// To repeat the last point: an expression represents dead-code
500 /// if, after checking it, **either** its type is `!` OR the
501 /// diverges flag is set to something other than `Maybe`.
502 diverges: Cell<Diverges>,
504 /// Whether any child nodes have any type errors.
505 has_errors: Cell<bool>,
507 enclosing_breakables: RefCell<EnclosingBreakables<'gcx, 'tcx>>,
509 inh: &'a Inherited<'a, 'gcx, 'tcx>,
512 impl<'a, 'gcx, 'tcx> Deref for FnCtxt<'a, 'gcx, 'tcx> {
513 type Target = Inherited<'a, 'gcx, 'tcx>;
514 fn deref(&self) -> &Self::Target {
519 /// Helper type of a temporary returned by Inherited::build(...).
520 /// Necessary because we can't write the following bound:
521 /// F: for<'b, 'tcx> where 'gcx: 'tcx FnOnce(Inherited<'b, 'gcx, 'tcx>).
522 pub struct InheritedBuilder<'a, 'gcx: 'a+'tcx, 'tcx: 'a> {
523 infcx: infer::InferCtxtBuilder<'a, 'gcx, 'tcx>,
527 impl<'a, 'gcx, 'tcx> Inherited<'a, 'gcx, 'tcx> {
528 pub fn build(tcx: TyCtxt<'a, 'gcx, 'gcx>, def_id: DefId)
529 -> InheritedBuilder<'a, 'gcx, 'tcx> {
530 let tables = ty::TypeckTables::empty();
531 let param_env = tcx.param_env(def_id);
533 infcx: tcx.infer_ctxt((tables, param_env)),
539 impl<'a, 'gcx, 'tcx> InheritedBuilder<'a, 'gcx, 'tcx> {
540 fn enter<F, R>(&'tcx mut self, f: F) -> R
541 where F: for<'b> FnOnce(Inherited<'b, 'gcx, 'tcx>) -> R
543 let def_id = self.def_id;
544 self.infcx.enter(|infcx| f(Inherited::new(infcx, def_id)))
548 impl<'a, 'gcx, 'tcx> Inherited<'a, 'gcx, 'tcx> {
549 fn new(infcx: InferCtxt<'a, 'gcx, 'tcx>, def_id: DefId) -> Self {
551 let item_id = tcx.hir.as_local_node_id(def_id);
552 let body_id = item_id.and_then(|id| tcx.hir.maybe_body_owned_by(id));
553 let implicit_region_bound = body_id.map(|body| {
554 tcx.mk_region(ty::ReScope(CodeExtent::CallSiteScope(body)))
559 fulfillment_cx: RefCell::new(traits::FulfillmentContext::new()),
560 locals: RefCell::new(NodeMap()),
561 deferred_call_resolutions: RefCell::new(DefIdMap()),
562 deferred_cast_checks: RefCell::new(Vec::new()),
563 anon_types: RefCell::new(NodeMap()),
564 implicit_region_bound,
568 fn register_predicate(&self, obligation: traits::PredicateObligation<'tcx>) {
569 debug!("register_predicate({:?})", obligation);
570 if obligation.has_escaping_regions() {
571 span_bug!(obligation.cause.span, "escaping regions in predicate {:?}",
576 .register_predicate_obligation(self, obligation);
579 fn register_predicates(&self, obligations: Vec<traits::PredicateObligation<'tcx>>) {
580 for obligation in obligations {
581 self.register_predicate(obligation);
585 fn register_infer_ok_obligations<T>(&self, infer_ok: InferOk<'tcx, T>) -> T {
586 self.register_predicates(infer_ok.obligations);
590 fn normalize_associated_types_in<T>(&self,
592 body_id: ast::NodeId,
594 where T : TypeFoldable<'tcx>
596 let ok = self.normalize_associated_types_in_as_infer_ok(span, body_id, value);
597 self.register_infer_ok_obligations(ok)
600 fn normalize_associated_types_in_as_infer_ok<T>(&self,
602 body_id: ast::NodeId,
605 where T : TypeFoldable<'tcx>
607 debug!("normalize_associated_types_in(value={:?})", value);
608 let mut selcx = traits::SelectionContext::new(self);
609 let cause = ObligationCause::misc(span, body_id);
610 let traits::Normalized { value, obligations } =
611 traits::normalize(&mut selcx, cause, value);
612 debug!("normalize_associated_types_in: result={:?} predicates={:?}",
615 InferOk { value, obligations }
618 /// Replace any late-bound regions bound in `value` with
619 /// free variants attached to `all_outlive_scope`.
620 fn liberate_late_bound_regions<T>(&self,
621 all_outlive_scope: DefId,
622 value: &ty::Binder<T>)
624 where T: TypeFoldable<'tcx>
626 self.tcx.replace_late_bound_regions(value, |br| {
627 self.tcx.mk_region(ty::ReFree(ty::FreeRegion {
628 scope: all_outlive_scope,
635 struct CheckItemTypesVisitor<'a, 'tcx: 'a> { tcx: TyCtxt<'a, 'tcx, 'tcx> }
637 impl<'a, 'tcx> ItemLikeVisitor<'tcx> for CheckItemTypesVisitor<'a, 'tcx> {
638 fn visit_item(&mut self, i: &'tcx hir::Item) {
639 check_item_type(self.tcx, i);
641 fn visit_trait_item(&mut self, _: &'tcx hir::TraitItem) { }
642 fn visit_impl_item(&mut self, _: &'tcx hir::ImplItem) { }
645 pub fn check_wf_new<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>) -> CompileResult {
646 tcx.sess.track_errors(|| {
647 let mut visit = wfcheck::CheckTypeWellFormedVisitor::new(tcx);
648 tcx.hir.krate().visit_all_item_likes(&mut visit.as_deep_visitor());
652 pub fn check_item_types<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>) -> CompileResult {
653 tcx.sess.track_errors(|| {
654 tcx.hir.krate().visit_all_item_likes(&mut CheckItemTypesVisitor { tcx });
658 pub fn check_item_bodies<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>) -> CompileResult {
659 tcx.typeck_item_bodies(LOCAL_CRATE)
662 fn typeck_item_bodies<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, crate_num: CrateNum) -> CompileResult {
663 debug_assert!(crate_num == LOCAL_CRATE);
664 tcx.sess.track_errors(|| {
665 for body_owner_def_id in tcx.body_owners() {
666 tcx.typeck_tables_of(body_owner_def_id);
671 pub fn provide(providers: &mut Providers) {
672 *providers = Providers {
683 fn closure_type<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
685 -> ty::PolyFnSig<'tcx> {
686 let node_id = tcx.hir.as_local_node_id(def_id).unwrap();
687 tcx.typeck_tables_of(def_id).closure_tys[&node_id]
690 fn closure_kind<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
693 let node_id = tcx.hir.as_local_node_id(def_id).unwrap();
694 tcx.typeck_tables_of(def_id).closure_kinds[&node_id].0
697 fn adt_destructor<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
699 -> Option<ty::Destructor> {
700 tcx.calculate_dtor(def_id, &mut dropck::check_drop_impl)
703 /// If this def-id is a "primary tables entry", returns `Some((body_id, decl))`
704 /// with information about it's body-id and fn-decl (if any). Otherwise,
707 /// If this function returns "some", then `typeck_tables(def_id)` will
708 /// succeed; if it returns `None`, then `typeck_tables(def_id)` may or
709 /// may not succeed. In some cases where this function returns `None`
710 /// (notably closures), `typeck_tables(def_id)` would wind up
711 /// redirecting to the owning function.
712 fn primary_body_of<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
714 -> Option<(hir::BodyId, Option<&'tcx hir::FnDecl>)>
716 match tcx.hir.get(id) {
717 hir::map::NodeItem(item) => {
719 hir::ItemConst(_, body) |
720 hir::ItemStatic(_, _, body) =>
722 hir::ItemFn(ref decl, .., body) =>
723 Some((body, Some(decl))),
728 hir::map::NodeTraitItem(item) => {
730 hir::TraitItemKind::Const(_, Some(body)) =>
732 hir::TraitItemKind::Method(ref sig, hir::TraitMethod::Provided(body)) =>
733 Some((body, Some(&sig.decl))),
738 hir::map::NodeImplItem(item) => {
740 hir::ImplItemKind::Const(_, body) =>
742 hir::ImplItemKind::Method(ref sig, body) =>
743 Some((body, Some(&sig.decl))),
748 hir::map::NodeExpr(expr) => {
749 // FIXME(eddyb) Closures should have separate
750 // function definition IDs and expression IDs.
751 // Type-checking should not let closures get
752 // this far in a constant position.
753 // Assume that everything other than closures
754 // is a constant "initializer" expression.
756 hir::ExprClosure(..) =>
759 Some((hir::BodyId { node_id: expr.id }, None)),
766 fn has_typeck_tables<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
769 // Closures' tables come from their outermost function,
770 // as they are part of the same "inference environment".
771 let outer_def_id = tcx.closure_base_def_id(def_id);
772 if outer_def_id != def_id {
773 return tcx.has_typeck_tables(outer_def_id);
776 let id = tcx.hir.as_local_node_id(def_id).unwrap();
777 primary_body_of(tcx, id).is_some()
780 fn typeck_tables_of<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
782 -> &'tcx ty::TypeckTables<'tcx> {
783 // Closures' tables come from their outermost function,
784 // as they are part of the same "inference environment".
785 let outer_def_id = tcx.closure_base_def_id(def_id);
786 if outer_def_id != def_id {
787 return tcx.typeck_tables_of(outer_def_id);
790 let id = tcx.hir.as_local_node_id(def_id).unwrap();
791 let span = tcx.hir.span(id);
793 // Figure out what primary body this item has.
794 let (body_id, fn_decl) = primary_body_of(tcx, id).unwrap_or_else(|| {
795 span_bug!(span, "can't type-check body of {:?}", def_id);
797 let body = tcx.hir.body(body_id);
799 Inherited::build(tcx, def_id).enter(|inh| {
800 let fcx = if let Some(decl) = fn_decl {
801 let fn_sig = tcx.type_of(def_id).fn_sig();
803 check_abi(tcx, span, fn_sig.abi());
805 // Compute the fty from point of view of inside fn.
807 inh.liberate_late_bound_regions(def_id, &fn_sig);
809 inh.normalize_associated_types_in(body.value.span, body_id.node_id, &fn_sig);
811 check_fn(&inh, fn_sig, decl, id, body)
813 let fcx = FnCtxt::new(&inh, body.value.id);
814 let expected_type = tcx.type_of(def_id);
815 let expected_type = fcx.normalize_associated_types_in(body.value.span, &expected_type);
816 fcx.require_type_is_sized(expected_type, body.value.span, traits::ConstSized);
818 // Gather locals in statics (because of block expressions).
819 // This is technically unnecessary because locals in static items are forbidden,
820 // but prevents type checking from blowing up before const checking can properly
822 GatherLocalsVisitor { fcx: &fcx }.visit_body(body);
824 fcx.check_expr_coercable_to_type(&body.value, expected_type);
829 fcx.select_all_obligations_and_apply_defaults();
830 fcx.closure_analyze(body);
831 fcx.select_obligations_where_possible();
833 fcx.select_all_obligations_or_error();
835 if fn_decl.is_some() {
836 fcx.regionck_fn(id, body);
838 fcx.regionck_expr(body);
841 fcx.resolve_type_vars_in_body(body)
845 fn check_abi<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, span: Span, abi: Abi) {
846 if !tcx.sess.target.target.is_abi_supported(abi) {
847 struct_span_err!(tcx.sess, span, E0570,
848 "The ABI `{}` is not supported for the current target", abi).emit()
852 struct GatherLocalsVisitor<'a, 'gcx: 'a+'tcx, 'tcx: 'a> {
853 fcx: &'a FnCtxt<'a, 'gcx, 'tcx>
856 impl<'a, 'gcx, 'tcx> GatherLocalsVisitor<'a, 'gcx, 'tcx> {
857 fn assign(&mut self, span: Span, nid: ast::NodeId, ty_opt: Option<Ty<'tcx>>) -> Ty<'tcx> {
860 // infer the variable's type
861 let var_ty = self.fcx.next_ty_var(TypeVariableOrigin::TypeInference(span));
862 self.fcx.locals.borrow_mut().insert(nid, var_ty);
866 // take type that the user specified
867 self.fcx.locals.borrow_mut().insert(nid, typ);
874 impl<'a, 'gcx, 'tcx> Visitor<'gcx> for GatherLocalsVisitor<'a, 'gcx, 'tcx> {
875 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'gcx> {
876 NestedVisitorMap::None
879 // Add explicitly-declared locals.
880 fn visit_local(&mut self, local: &'gcx hir::Local) {
881 let o_ty = match local.ty {
882 Some(ref ty) => Some(self.fcx.to_ty(&ty)),
885 self.assign(local.span, local.id, o_ty);
886 debug!("Local variable {:?} is assigned type {}",
888 self.fcx.ty_to_string(
889 self.fcx.locals.borrow().get(&local.id).unwrap().clone()));
890 intravisit::walk_local(self, local);
893 // Add pattern bindings.
894 fn visit_pat(&mut self, p: &'gcx hir::Pat) {
895 if let PatKind::Binding(_, _, ref path1, _) = p.node {
896 let var_ty = self.assign(p.span, p.id, None);
898 self.fcx.require_type_is_sized(var_ty, p.span,
899 traits::VariableType(p.id));
901 debug!("Pattern binding {} is assigned to {} with type {:?}",
903 self.fcx.ty_to_string(
904 self.fcx.locals.borrow().get(&p.id).unwrap().clone()),
907 intravisit::walk_pat(self, p);
910 // Don't descend into the bodies of nested closures
911 fn visit_fn(&mut self, _: intravisit::FnKind<'gcx>, _: &'gcx hir::FnDecl,
912 _: hir::BodyId, _: Span, _: ast::NodeId) { }
915 /// Helper used for fns and closures. Does the grungy work of checking a function
916 /// body and returns the function context used for that purpose, since in the case of a fn item
917 /// there is still a bit more to do.
920 /// * inherited: other fields inherited from the enclosing fn (if any)
921 fn check_fn<'a, 'gcx, 'tcx>(inherited: &'a Inherited<'a, 'gcx, 'tcx>,
922 fn_sig: ty::FnSig<'tcx>,
923 decl: &'gcx hir::FnDecl,
925 body: &'gcx hir::Body)
926 -> FnCtxt<'a, 'gcx, 'tcx>
928 let mut fn_sig = fn_sig.clone();
930 debug!("check_fn(sig={:?}, fn_id={})", fn_sig, fn_id);
932 // Create the function context. This is either derived from scratch or,
933 // in the case of function expressions, based on the outer context.
934 let mut fcx = FnCtxt::new(inherited, body.value.id);
935 *fcx.ps.borrow_mut() = UnsafetyState::function(fn_sig.unsafety, fn_id);
937 let ret_ty = fn_sig.output();
938 fcx.require_type_is_sized(ret_ty, decl.output.span(), traits::ReturnType);
939 let ret_ty = fcx.instantiate_anon_types(&ret_ty);
940 fcx.ret_coercion = Some(RefCell::new(CoerceMany::new(ret_ty)));
941 fn_sig = fcx.tcx.mk_fn_sig(
942 fn_sig.inputs().iter().cloned(),
949 GatherLocalsVisitor { fcx: &fcx, }.visit_body(body);
951 // Add formal parameters.
952 for (arg_ty, arg) in fn_sig.inputs().iter().zip(&body.arguments) {
953 // The type of the argument must be well-formed.
955 // NB -- this is now checked in wfcheck, but that
956 // currently only results in warnings, so we issue an
957 // old-style WF obligation here so that we still get the
958 // errors that we used to get.
959 fcx.register_old_wf_obligation(arg_ty, arg.pat.span, traits::MiscObligation);
961 // Check the pattern.
962 fcx.check_pat_arg(&arg.pat, arg_ty, true);
963 fcx.write_ty(arg.id, arg_ty);
966 inherited.tables.borrow_mut().liberated_fn_sigs.insert(fn_id, fn_sig);
968 fcx.check_return_expr(&body.value);
970 // Finalize the return check by taking the LUB of the return types
971 // we saw and assigning it to the expected return type. This isn't
972 // really expected to fail, since the coercions would have failed
973 // earlier when trying to find a LUB.
975 // However, the behavior around `!` is sort of complex. In the
976 // event that the `actual_return_ty` comes back as `!`, that
977 // indicates that the fn either does not return or "returns" only
978 // values of type `!`. In this case, if there is an expected
979 // return type that is *not* `!`, that should be ok. But if the
980 // return type is being inferred, we want to "fallback" to `!`:
982 // let x = move || panic!();
984 // To allow for that, I am creating a type variable with diverging
985 // fallback. This was deemed ever so slightly better than unifying
986 // the return value with `!` because it allows for the caller to
987 // make more assumptions about the return type (e.g., they could do
989 // let y: Option<u32> = Some(x());
991 // which would then cause this return type to become `u32`, not
993 let coercion = fcx.ret_coercion.take().unwrap().into_inner();
994 let mut actual_return_ty = coercion.complete(&fcx);
995 if actual_return_ty.is_never() {
996 actual_return_ty = fcx.next_diverging_ty_var(
997 TypeVariableOrigin::DivergingFn(body.value.span));
999 fcx.demand_suptype(body.value.span, ret_ty, actual_return_ty);
1004 fn check_struct<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
1007 let def_id = tcx.hir.local_def_id(id);
1008 let def = tcx.adt_def(def_id);
1009 def.destructor(tcx); // force the destructor to be evaluated
1010 check_representable(tcx, span, def_id);
1012 if def.repr.simd() {
1013 check_simd(tcx, span, def_id);
1016 // if struct is packed and not aligned, check fields for alignment.
1017 // Checks for combining packed and align attrs on single struct are done elsewhere.
1018 if tcx.adt_def(def_id).repr.packed() && tcx.adt_def(def_id).repr.align == 0 {
1019 check_packed(tcx, span, def_id);
1023 fn check_union<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
1026 let def_id = tcx.hir.local_def_id(id);
1027 let def = tcx.adt_def(def_id);
1028 def.destructor(tcx); // force the destructor to be evaluated
1029 check_representable(tcx, span, def_id);
1032 pub fn check_item_type<'a,'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, it: &'tcx hir::Item) {
1033 debug!("check_item_type(it.id={}, it.name={})",
1035 tcx.item_path_str(tcx.hir.local_def_id(it.id)));
1036 let _indenter = indenter();
1038 // Consts can play a role in type-checking, so they are included here.
1039 hir::ItemStatic(..) |
1040 hir::ItemConst(..) => {
1041 tcx.typeck_tables_of(tcx.hir.local_def_id(it.id));
1043 hir::ItemEnum(ref enum_definition, _) => {
1046 &enum_definition.variants,
1049 hir::ItemFn(..) => {} // entirely within check_item_body
1050 hir::ItemImpl(.., ref impl_item_refs) => {
1051 debug!("ItemImpl {} with id {}", it.name, it.id);
1052 let impl_def_id = tcx.hir.local_def_id(it.id);
1053 if let Some(impl_trait_ref) = tcx.impl_trait_ref(impl_def_id) {
1054 check_impl_items_against_trait(tcx,
1059 let trait_def_id = impl_trait_ref.def_id;
1060 check_on_unimplemented(tcx, trait_def_id, it);
1063 hir::ItemTrait(..) => {
1064 let def_id = tcx.hir.local_def_id(it.id);
1065 check_on_unimplemented(tcx, def_id, it);
1067 hir::ItemStruct(..) => {
1068 check_struct(tcx, it.id, it.span);
1070 hir::ItemUnion(..) => {
1071 check_union(tcx, it.id, it.span);
1073 hir::ItemTy(_, ref generics) => {
1074 let def_id = tcx.hir.local_def_id(it.id);
1075 let pty_ty = tcx.type_of(def_id);
1076 check_bounds_are_used(tcx, generics, pty_ty);
1078 hir::ItemForeignMod(ref m) => {
1079 check_abi(tcx, it.span, m.abi);
1081 if m.abi == Abi::RustIntrinsic {
1082 for item in &m.items {
1083 intrinsic::check_intrinsic_type(tcx, item);
1085 } else if m.abi == Abi::PlatformIntrinsic {
1086 for item in &m.items {
1087 intrinsic::check_platform_intrinsic_type(tcx, item);
1090 for item in &m.items {
1091 let generics = tcx.generics_of(tcx.hir.local_def_id(item.id));
1092 if !generics.types.is_empty() {
1093 let mut err = struct_span_err!(tcx.sess, item.span, E0044,
1094 "foreign items may not have type parameters");
1095 span_help!(&mut err, item.span,
1096 "consider using specialization instead of \
1101 if let hir::ForeignItemFn(ref fn_decl, _, _) = item.node {
1102 require_c_abi_if_variadic(tcx, fn_decl, m.abi, item.span);
1107 _ => {/* nothing to do */ }
1111 fn check_on_unimplemented<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
1114 let generics = tcx.generics_of(def_id);
1115 if let Some(ref attr) = item.attrs.iter().find(|a| {
1116 a.check_name("rustc_on_unimplemented")
1118 if let Some(istring) = attr.value_str() {
1119 let istring = istring.as_str();
1120 let parser = Parser::new(&istring);
1121 let types = &generics.types;
1122 for token in parser {
1124 Piece::String(_) => (), // Normal string, no need to check it
1125 Piece::NextArgument(a) => match a.position {
1126 // `{Self}` is allowed
1127 Position::ArgumentNamed(s) if s == "Self" => (),
1128 // So is `{A}` if A is a type parameter
1129 Position::ArgumentNamed(s) => match types.iter().find(|t| {
1134 let name = tcx.item_name(def_id);
1135 span_err!(tcx.sess, attr.span, E0230,
1136 "there is no type parameter \
1141 // `{:1}` and `{}` are not to be used
1142 Position::ArgumentIs(_) => {
1143 span_err!(tcx.sess, attr.span, E0231,
1144 "only named substitution \
1145 parameters are allowed");
1152 tcx.sess, attr.span, E0232,
1153 "this attribute must have a value")
1154 .span_label(attr.span, "attribute requires a value")
1155 .note(&format!("eg `#[rustc_on_unimplemented = \"foo\"]`"))
1161 fn report_forbidden_specialization<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
1162 impl_item: &hir::ImplItem,
1165 let mut err = struct_span_err!(
1166 tcx.sess, impl_item.span, E0520,
1167 "`{}` specializes an item from a parent `impl`, but \
1168 that item is not marked `default`",
1170 err.span_label(impl_item.span, format!("cannot specialize default item `{}`",
1173 match tcx.span_of_impl(parent_impl) {
1175 err.span_label(span, "parent `impl` is here");
1176 err.note(&format!("to specialize, `{}` in the parent `impl` must be marked `default`",
1180 err.note(&format!("parent implementation is in crate `{}`", cname));
1187 fn check_specialization_validity<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
1188 trait_def: &ty::TraitDef,
1190 impl_item: &hir::ImplItem)
1192 let ancestors = trait_def.ancestors(tcx, impl_id);
1194 let kind = match impl_item.node {
1195 hir::ImplItemKind::Const(..) => ty::AssociatedKind::Const,
1196 hir::ImplItemKind::Method(..) => ty::AssociatedKind::Method,
1197 hir::ImplItemKind::Type(_) => ty::AssociatedKind::Type
1199 let parent = ancestors.defs(tcx, impl_item.name, kind).skip(1).next()
1200 .map(|node_item| node_item.map(|parent| parent.defaultness));
1202 if let Some(parent) = parent {
1203 if tcx.impl_item_is_final(&parent) {
1204 report_forbidden_specialization(tcx, impl_item, parent.node.def_id());
1210 fn check_impl_items_against_trait<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
1213 impl_trait_ref: ty::TraitRef<'tcx>,
1214 impl_item_refs: &[hir::ImplItemRef]) {
1215 // If the trait reference itself is erroneous (so the compilation is going
1216 // to fail), skip checking the items here -- the `impl_item` table in `tcx`
1217 // isn't populated for such impls.
1218 if impl_trait_ref.references_error() { return; }
1220 // Locate trait definition and items
1221 let trait_def = tcx.trait_def(impl_trait_ref.def_id);
1222 let mut overridden_associated_type = None;
1224 let impl_items = || impl_item_refs.iter().map(|iiref| tcx.hir.impl_item(iiref.id));
1226 // Check existing impl methods to see if they are both present in trait
1227 // and compatible with trait signature
1228 for impl_item in impl_items() {
1229 let ty_impl_item = tcx.associated_item(tcx.hir.local_def_id(impl_item.id));
1230 let ty_trait_item = tcx.associated_items(impl_trait_ref.def_id)
1231 .find(|ac| ac.name == ty_impl_item.name);
1233 // Check that impl definition matches trait definition
1234 if let Some(ty_trait_item) = ty_trait_item {
1235 match impl_item.node {
1236 hir::ImplItemKind::Const(..) => {
1237 // Find associated const definition.
1238 if ty_trait_item.kind == ty::AssociatedKind::Const {
1239 compare_const_impl(tcx,
1245 let mut err = struct_span_err!(tcx.sess, impl_item.span, E0323,
1246 "item `{}` is an associated const, \
1247 which doesn't match its trait `{}`",
1250 err.span_label(impl_item.span, "does not match trait");
1251 // We can only get the spans from local trait definition
1252 // Same for E0324 and E0325
1253 if let Some(trait_span) = tcx.hir.span_if_local(ty_trait_item.def_id) {
1254 err.span_label(trait_span, "item in trait");
1259 hir::ImplItemKind::Method(..) => {
1260 let trait_span = tcx.hir.span_if_local(ty_trait_item.def_id);
1261 if ty_trait_item.kind == ty::AssociatedKind::Method {
1262 let err_count = tcx.sess.err_count();
1263 compare_impl_method(tcx,
1269 true); // start with old-broken-mode
1270 if err_count == tcx.sess.err_count() {
1271 // old broken mode did not report an error. Try with the new mode.
1272 compare_impl_method(tcx,
1278 false); // use the new mode
1281 let mut err = struct_span_err!(tcx.sess, impl_item.span, E0324,
1282 "item `{}` is an associated method, \
1283 which doesn't match its trait `{}`",
1286 err.span_label(impl_item.span, "does not match trait");
1287 if let Some(trait_span) = tcx.hir.span_if_local(ty_trait_item.def_id) {
1288 err.span_label(trait_span, "item in trait");
1293 hir::ImplItemKind::Type(_) => {
1294 if ty_trait_item.kind == ty::AssociatedKind::Type {
1295 if ty_trait_item.defaultness.has_value() {
1296 overridden_associated_type = Some(impl_item);
1299 let mut err = struct_span_err!(tcx.sess, impl_item.span, E0325,
1300 "item `{}` is an associated type, \
1301 which doesn't match its trait `{}`",
1304 err.span_label(impl_item.span, "does not match trait");
1305 if let Some(trait_span) = tcx.hir.span_if_local(ty_trait_item.def_id) {
1306 err.span_label(trait_span, "item in trait");
1314 check_specialization_validity(tcx, trait_def, impl_id, impl_item);
1317 // Check for missing items from trait
1318 let mut missing_items = Vec::new();
1319 let mut invalidated_items = Vec::new();
1320 let associated_type_overridden = overridden_associated_type.is_some();
1321 for trait_item in tcx.associated_items(impl_trait_ref.def_id) {
1322 let is_implemented = trait_def.ancestors(tcx, impl_id)
1323 .defs(tcx, trait_item.name, trait_item.kind)
1325 .map(|node_item| !node_item.node.is_from_trait())
1328 if !is_implemented {
1329 if !trait_item.defaultness.has_value() {
1330 missing_items.push(trait_item);
1331 } else if associated_type_overridden {
1332 invalidated_items.push(trait_item.name);
1337 let signature = |item: &ty::AssociatedItem| {
1339 ty::AssociatedKind::Method => {
1340 format!("{}", tcx.type_of(item.def_id).fn_sig().0)
1342 ty::AssociatedKind::Type => format!("type {};", item.name.to_string()),
1343 ty::AssociatedKind::Const => {
1344 format!("const {}: {:?};", item.name.to_string(), tcx.type_of(item.def_id))
1349 if !missing_items.is_empty() {
1350 let mut err = struct_span_err!(tcx.sess, impl_span, E0046,
1351 "not all trait items implemented, missing: `{}`",
1352 missing_items.iter()
1353 .map(|trait_item| trait_item.name.to_string())
1354 .collect::<Vec<_>>().join("`, `"));
1355 err.span_label(impl_span, format!("missing `{}` in implementation",
1356 missing_items.iter()
1357 .map(|trait_item| trait_item.name.to_string())
1358 .collect::<Vec<_>>().join("`, `")));
1359 for trait_item in missing_items {
1360 if let Some(span) = tcx.hir.span_if_local(trait_item.def_id) {
1361 err.span_label(span, format!("`{}` from trait", trait_item.name));
1363 err.note(&format!("`{}` from trait: `{}`",
1365 signature(&trait_item)));
1371 if !invalidated_items.is_empty() {
1372 let invalidator = overridden_associated_type.unwrap();
1373 span_err!(tcx.sess, invalidator.span, E0399,
1374 "the following trait items need to be reimplemented \
1375 as `{}` was overridden: `{}`",
1377 invalidated_items.iter()
1378 .map(|name| name.to_string())
1379 .collect::<Vec<_>>().join("`, `"))
1383 /// Checks whether a type can be represented in memory. In particular, it
1384 /// identifies types that contain themselves without indirection through a
1385 /// pointer, which would mean their size is unbounded.
1386 fn check_representable<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
1390 let rty = tcx.type_of(item_def_id);
1392 // Check that it is possible to represent this type. This call identifies
1393 // (1) types that contain themselves and (2) types that contain a different
1394 // recursive type. It is only necessary to throw an error on those that
1395 // contain themselves. For case 2, there must be an inner type that will be
1396 // caught by case 1.
1397 match rty.is_representable(tcx, sp) {
1398 Representability::SelfRecursive(spans) => {
1399 let mut err = tcx.recursive_type_with_infinite_size_error(item_def_id);
1401 err.span_label(span, "recursive without indirection");
1406 Representability::Representable | Representability::ContainsRecursive => (),
1411 pub fn check_simd<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, sp: Span, def_id: DefId) {
1412 let t = tcx.type_of(def_id);
1414 ty::TyAdt(def, substs) if def.is_struct() => {
1415 let fields = &def.struct_variant().fields;
1416 if fields.is_empty() {
1417 span_err!(tcx.sess, sp, E0075, "SIMD vector cannot be empty");
1420 let e = fields[0].ty(tcx, substs);
1421 if !fields.iter().all(|f| f.ty(tcx, substs) == e) {
1422 struct_span_err!(tcx.sess, sp, E0076, "SIMD vector should be homogeneous")
1423 .span_label(sp, "SIMD elements must have the same type")
1428 ty::TyParam(_) => { /* struct<T>(T, T, T, T) is ok */ }
1429 _ if e.is_machine() => { /* struct(u8, u8, u8, u8) is ok */ }
1431 span_err!(tcx.sess, sp, E0077,
1432 "SIMD vector element type should be machine type");
1441 fn check_packed<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, sp: Span, def_id: DefId) {
1442 if check_packed_inner(tcx, def_id, &mut Vec::new()) {
1443 struct_span_err!(tcx.sess, sp, E0588,
1444 "packed struct cannot transitively contain a `[repr(align)]` struct").emit();
1448 fn check_packed_inner<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
1450 stack: &mut Vec<DefId>) -> bool {
1451 let t = tcx.type_of(def_id);
1452 if stack.contains(&def_id) {
1453 debug!("check_packed_inner: {:?} is recursive", t);
1457 ty::TyAdt(def, substs) if def.is_struct() => {
1458 if tcx.adt_def(def.did).repr.align > 0 {
1461 // push struct def_id before checking fields
1463 for field in &def.struct_variant().fields {
1464 let f = field.ty(tcx, substs);
1466 ty::TyAdt(def, _) => {
1467 if check_packed_inner(tcx, def.did, stack) {
1474 // only need to pop if not early out
1482 #[allow(trivial_numeric_casts)]
1483 pub fn check_enum<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
1485 vs: &'tcx [hir::Variant],
1487 let def_id = tcx.hir.local_def_id(id);
1488 let def = tcx.adt_def(def_id);
1489 def.destructor(tcx); // force the destructor to be evaluated
1491 if vs.is_empty() && tcx.has_attr(def_id, "repr") {
1493 tcx.sess, sp, E0084,
1494 "unsupported representation for zero-variant enum")
1495 .span_label(sp, "unsupported enum representation")
1499 let repr_type_ty = def.repr.discr_type().to_ty(tcx);
1500 if repr_type_ty == tcx.types.i128 || repr_type_ty == tcx.types.u128 {
1501 if !tcx.sess.features.borrow().i128_type {
1502 emit_feature_err(&tcx.sess.parse_sess,
1503 "i128_type", sp, GateIssue::Language, "128-bit type is unstable");
1508 if let Some(e) = v.node.disr_expr {
1509 tcx.typeck_tables_of(tcx.hir.local_def_id(e.node_id));
1513 let mut disr_vals: Vec<ConstInt> = Vec::new();
1514 for (discr, v) in def.discriminants(tcx).zip(vs) {
1515 // Check for duplicate discriminant values
1516 if let Some(i) = disr_vals.iter().position(|&x| x == discr) {
1517 let variant_i_node_id = tcx.hir.as_local_node_id(def.variants[i].did).unwrap();
1518 let variant_i = tcx.hir.expect_variant(variant_i_node_id);
1519 let i_span = match variant_i.node.disr_expr {
1520 Some(expr) => tcx.hir.span(expr.node_id),
1521 None => tcx.hir.span(variant_i_node_id)
1523 let span = match v.node.disr_expr {
1524 Some(expr) => tcx.hir.span(expr.node_id),
1527 struct_span_err!(tcx.sess, span, E0081,
1528 "discriminant value `{}` already exists", disr_vals[i])
1529 .span_label(i_span, format!("first use of `{}`", disr_vals[i]))
1530 .span_label(span , format!("enum already has `{}`", disr_vals[i]))
1533 disr_vals.push(discr);
1536 check_representable(tcx, sp, def_id);
1539 impl<'a, 'gcx, 'tcx> AstConv<'gcx, 'tcx> for FnCtxt<'a, 'gcx, 'tcx> {
1540 fn tcx<'b>(&'b self) -> TyCtxt<'b, 'gcx, 'tcx> { self.tcx }
1542 fn get_type_parameter_bounds(&self, _: Span, def_id: DefId)
1543 -> ty::GenericPredicates<'tcx>
1546 let node_id = tcx.hir.as_local_node_id(def_id).unwrap();
1547 let item_id = tcx.hir.ty_param_owner(node_id);
1548 let item_def_id = tcx.hir.local_def_id(item_id);
1549 let generics = tcx.generics_of(item_def_id);
1550 let index = generics.type_param_to_index[&def_id.index];
1551 ty::GenericPredicates {
1553 predicates: self.param_env.caller_bounds.iter().filter(|predicate| {
1555 ty::Predicate::Trait(ref data) => {
1556 data.0.self_ty().is_param(index)
1560 }).cloned().collect()
1564 fn re_infer(&self, span: Span, def: Option<&ty::RegionParameterDef>)
1565 -> Option<ty::Region<'tcx>> {
1567 Some(def) => infer::EarlyBoundRegion(span, def.name, def.issue_32330),
1568 None => infer::MiscVariable(span)
1570 Some(self.next_region_var(v))
1573 fn ty_infer(&self, span: Span) -> Ty<'tcx> {
1574 self.next_ty_var(TypeVariableOrigin::TypeInference(span))
1577 fn ty_infer_for_def(&self,
1578 ty_param_def: &ty::TypeParameterDef,
1579 substs: &[Kind<'tcx>],
1580 span: Span) -> Ty<'tcx> {
1581 self.type_var_for_def(span, ty_param_def, substs)
1584 fn projected_ty_from_poly_trait_ref(&self,
1586 poly_trait_ref: ty::PolyTraitRef<'tcx>,
1587 item_name: ast::Name)
1590 let (trait_ref, _) =
1591 self.replace_late_bound_regions_with_fresh_var(
1593 infer::LateBoundRegionConversionTime::AssocTypeProjection(item_name),
1596 self.tcx().mk_projection(trait_ref, item_name)
1599 fn normalize_ty(&self, span: Span, ty: Ty<'tcx>) -> Ty<'tcx> {
1600 if ty.has_escaping_regions() {
1601 ty // FIXME: normalization and escaping regions
1603 self.normalize_associated_types_in(span, &ty)
1607 fn set_tainted_by_errors(&self) {
1608 self.infcx.set_tainted_by_errors()
1612 /// Controls whether the arguments are tupled. This is used for the call
1615 /// Tupling means that all call-side arguments are packed into a tuple and
1616 /// passed as a single parameter. For example, if tupling is enabled, this
1619 /// fn f(x: (isize, isize))
1621 /// Can be called as:
1628 #[derive(Clone, Eq, PartialEq)]
1629 enum TupleArgumentsFlag {
1634 impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
1635 pub fn new(inh: &'a Inherited<'a, 'gcx, 'tcx>,
1636 body_id: ast::NodeId)
1637 -> FnCtxt<'a, 'gcx, 'tcx> {
1640 err_count_on_creation: inh.tcx.sess.err_count(),
1642 ps: RefCell::new(UnsafetyState::function(hir::Unsafety::Normal,
1643 ast::CRATE_NODE_ID)),
1644 diverges: Cell::new(Diverges::Maybe),
1645 has_errors: Cell::new(false),
1646 enclosing_breakables: RefCell::new(EnclosingBreakables {
1654 pub fn sess(&self) -> &Session {
1658 pub fn err_count_since_creation(&self) -> usize {
1659 self.tcx.sess.err_count() - self.err_count_on_creation
1662 /// Produce warning on the given node, if the current point in the
1663 /// function is unreachable, and there hasn't been another warning.
1664 fn warn_if_unreachable(&self, id: ast::NodeId, span: Span, kind: &str) {
1665 if self.diverges.get() == Diverges::Always {
1666 self.diverges.set(Diverges::WarnedAlways);
1668 debug!("warn_if_unreachable: id={:?} span={:?} kind={}", id, span, kind);
1670 self.tables.borrow_mut().lints.add_lint(
1671 lint::builtin::UNREACHABLE_CODE,
1673 format!("unreachable {}", kind));
1679 code: ObligationCauseCode<'tcx>)
1680 -> ObligationCause<'tcx> {
1681 ObligationCause::new(span, self.body_id, code)
1684 pub fn misc(&self, span: Span) -> ObligationCause<'tcx> {
1685 self.cause(span, ObligationCauseCode::MiscObligation)
1688 /// Resolves type variables in `ty` if possible. Unlike the infcx
1689 /// version (resolve_type_vars_if_possible), this version will
1690 /// also select obligations if it seems useful, in an effort
1691 /// to get more type information.
1692 fn resolve_type_vars_with_obligations(&self, mut ty: Ty<'tcx>) -> Ty<'tcx> {
1693 debug!("resolve_type_vars_with_obligations(ty={:?})", ty);
1695 // No TyInfer()? Nothing needs doing.
1696 if !ty.has_infer_types() {
1697 debug!("resolve_type_vars_with_obligations: ty={:?}", ty);
1701 // If `ty` is a type variable, see whether we already know what it is.
1702 ty = self.resolve_type_vars_if_possible(&ty);
1703 if !ty.has_infer_types() {
1704 debug!("resolve_type_vars_with_obligations: ty={:?}", ty);
1708 // If not, try resolving pending obligations as much as
1709 // possible. This can help substantially when there are
1710 // indirect dependencies that don't seem worth tracking
1712 self.select_obligations_where_possible();
1713 ty = self.resolve_type_vars_if_possible(&ty);
1715 debug!("resolve_type_vars_with_obligations: ty={:?}", ty);
1719 fn record_deferred_call_resolution(&self,
1720 closure_def_id: DefId,
1721 r: DeferredCallResolution<'gcx, 'tcx>) {
1722 let mut deferred_call_resolutions = self.deferred_call_resolutions.borrow_mut();
1723 deferred_call_resolutions.entry(closure_def_id).or_insert(vec![]).push(r);
1726 fn remove_deferred_call_resolutions(&self,
1727 closure_def_id: DefId)
1728 -> Vec<DeferredCallResolution<'gcx, 'tcx>>
1730 let mut deferred_call_resolutions = self.deferred_call_resolutions.borrow_mut();
1731 deferred_call_resolutions.remove(&closure_def_id).unwrap_or(vec![])
1734 pub fn tag(&self) -> String {
1735 let self_ptr: *const FnCtxt = self;
1736 format!("{:?}", self_ptr)
1739 pub fn local_ty(&self, span: Span, nid: ast::NodeId) -> Ty<'tcx> {
1740 match self.locals.borrow().get(&nid) {
1743 span_bug!(span, "no type for local variable {}",
1744 self.tcx.hir.node_to_string(nid));
1750 pub fn write_ty(&self, node_id: ast::NodeId, ty: Ty<'tcx>) {
1751 debug!("write_ty({}, {:?}) in fcx {}",
1752 node_id, self.resolve_type_vars_if_possible(&ty), self.tag());
1753 self.tables.borrow_mut().node_types.insert(node_id, ty);
1755 if ty.references_error() {
1756 self.has_errors.set(true);
1757 self.set_tainted_by_errors();
1761 pub fn write_method_call(&self, node_id: ast::NodeId, method: MethodCallee<'tcx>) {
1762 self.tables.borrow_mut().type_dependent_defs.insert(node_id, Def::Method(method.def_id));
1763 self.write_substs(node_id, method.substs);
1766 pub fn write_substs(&self, node_id: ast::NodeId, substs: &'tcx Substs<'tcx>) {
1767 if !substs.is_noop() {
1768 debug!("write_substs({}, {:?}) in fcx {}",
1773 self.tables.borrow_mut().node_substs.insert(node_id, substs);
1777 pub fn apply_adjustments(&self, expr: &hir::Expr, adj: Vec<Adjustment<'tcx>>) {
1778 debug!("apply_adjustments(expr={:?}, adj={:?})", expr, adj);
1784 match self.tables.borrow_mut().adjustments.entry(expr.id) {
1785 Entry::Vacant(entry) => { entry.insert(adj); },
1786 Entry::Occupied(mut entry) => {
1787 debug!(" - composing on top of {:?}", entry.get());
1788 match (&entry.get()[..], &adj[..]) {
1789 // Applying any adjustment on top of a NeverToAny
1790 // is a valid NeverToAny adjustment, because it can't
1792 (&[Adjustment { kind: Adjust::NeverToAny, .. }], _) => return,
1794 Adjustment { kind: Adjust::Deref(_), .. },
1795 Adjustment { kind: Adjust::Borrow(AutoBorrow::Ref(..)), .. },
1797 Adjustment { kind: Adjust::Deref(_), .. },
1798 .. // Any following adjustments are allowed.
1800 // A reborrow has no effect before a dereference.
1802 // FIXME: currently we never try to compose autoderefs
1803 // and ReifyFnPointer/UnsafeFnPointer, but we could.
1805 bug!("while adjusting {:?}, can't compose {:?} and {:?}",
1806 expr, entry.get(), adj)
1808 *entry.get_mut() = adj;
1813 /// Basically whenever we are converting from a type scheme into
1814 /// the fn body space, we always want to normalize associated
1815 /// types as well. This function combines the two.
1816 fn instantiate_type_scheme<T>(&self,
1818 substs: &Substs<'tcx>,
1821 where T : TypeFoldable<'tcx>
1823 let value = value.subst(self.tcx, substs);
1824 let result = self.normalize_associated_types_in(span, &value);
1825 debug!("instantiate_type_scheme(value={:?}, substs={:?}) = {:?}",
1832 /// As `instantiate_type_scheme`, but for the bounds found in a
1833 /// generic type scheme.
1834 fn instantiate_bounds(&self, span: Span, def_id: DefId, substs: &Substs<'tcx>)
1835 -> ty::InstantiatedPredicates<'tcx> {
1836 let bounds = self.tcx.predicates_of(def_id);
1837 let result = bounds.instantiate(self.tcx, substs);
1838 let result = self.normalize_associated_types_in(span, &result);
1839 debug!("instantiate_bounds(bounds={:?}, substs={:?}) = {:?}",
1846 /// Replace all anonymized types with fresh inference variables
1847 /// and record them for writeback.
1848 fn instantiate_anon_types<T: TypeFoldable<'tcx>>(&self, value: &T) -> T {
1849 value.fold_with(&mut BottomUpFolder { tcx: self.tcx, fldop: |ty| {
1850 if let ty::TyAnon(def_id, substs) = ty.sty {
1851 // Use the same type variable if the exact same TyAnon appears more
1852 // than once in the return type (e.g. if it's pased to a type alias).
1853 let id = self.tcx.hir.as_local_node_id(def_id).unwrap();
1854 if let Some(ty_var) = self.anon_types.borrow().get(&id) {
1857 let span = self.tcx.def_span(def_id);
1858 let ty_var = self.next_ty_var(TypeVariableOrigin::TypeInference(span));
1859 self.anon_types.borrow_mut().insert(id, ty_var);
1861 let predicates_of = self.tcx.predicates_of(def_id);
1862 let bounds = predicates_of.instantiate(self.tcx, substs);
1864 for predicate in bounds.predicates {
1865 // Change the predicate to refer to the type variable,
1866 // which will be the concrete type, instead of the TyAnon.
1867 // This also instantiates nested `impl Trait`.
1868 let predicate = self.instantiate_anon_types(&predicate);
1870 // Require that the predicate holds for the concrete type.
1871 let cause = traits::ObligationCause::new(span, self.body_id,
1872 traits::ReturnType);
1873 self.register_predicate(traits::Obligation::new(cause, predicate));
1883 fn normalize_associated_types_in<T>(&self, span: Span, value: &T) -> T
1884 where T : TypeFoldable<'tcx>
1886 let ok = self.normalize_associated_types_in_as_infer_ok(span, value);
1887 self.register_infer_ok_obligations(ok)
1890 fn normalize_associated_types_in_as_infer_ok<T>(&self, span: Span, value: &T)
1892 where T : TypeFoldable<'tcx>
1894 self.inh.normalize_associated_types_in_as_infer_ok(span, self.body_id, value)
1897 pub fn write_nil(&self, node_id: ast::NodeId) {
1898 self.write_ty(node_id, self.tcx.mk_nil());
1901 pub fn write_error(&self, node_id: ast::NodeId) {
1902 self.write_ty(node_id, self.tcx.types.err);
1905 pub fn require_type_meets(&self,
1908 code: traits::ObligationCauseCode<'tcx>,
1911 self.register_bound(
1914 traits::ObligationCause::new(span, self.body_id, code));
1917 pub fn require_type_is_sized(&self,
1920 code: traits::ObligationCauseCode<'tcx>)
1922 let lang_item = self.tcx.require_lang_item(lang_items::SizedTraitLangItem);
1923 self.require_type_meets(ty, span, code, lang_item);
1926 pub fn register_bound(&self,
1929 cause: traits::ObligationCause<'tcx>)
1931 self.fulfillment_cx.borrow_mut()
1932 .register_bound(self, ty, def_id, cause);
1935 pub fn to_ty(&self, ast_t: &hir::Ty) -> Ty<'tcx> {
1936 let t = AstConv::ast_ty_to_ty(self, ast_t);
1937 self.register_wf_obligation(t, ast_t.span, traits::MiscObligation);
1941 pub fn node_ty(&self, id: ast::NodeId) -> Ty<'tcx> {
1942 match self.tables.borrow().node_types.get(&id) {
1944 None if self.err_count_since_creation() != 0 => self.tcx.types.err,
1946 bug!("no type for node {}: {} in fcx {}",
1947 id, self.tcx.hir.node_to_string(id),
1953 /// Registers an obligation for checking later, during regionck, that the type `ty` must
1954 /// outlive the region `r`.
1955 pub fn register_region_obligation(&self,
1957 region: ty::Region<'tcx>,
1958 cause: traits::ObligationCause<'tcx>)
1960 let mut fulfillment_cx = self.fulfillment_cx.borrow_mut();
1961 fulfillment_cx.register_region_obligation(ty, region, cause);
1964 /// Registers an obligation for checking later, during regionck, that the type `ty` must
1965 /// outlive the region `r`.
1966 pub fn register_wf_obligation(&self,
1969 code: traits::ObligationCauseCode<'tcx>)
1971 // WF obligations never themselves fail, so no real need to give a detailed cause:
1972 let cause = traits::ObligationCause::new(span, self.body_id, code);
1973 self.register_predicate(traits::Obligation::new(cause, ty::Predicate::WellFormed(ty)));
1976 pub fn register_old_wf_obligation(&self,
1979 code: traits::ObligationCauseCode<'tcx>)
1981 // Registers an "old-style" WF obligation that uses the
1982 // implicator code. This is basically a buggy version of
1983 // `register_wf_obligation` that is being kept around
1984 // temporarily just to help with phasing in the newer rules.
1986 // FIXME(#27579) all uses of this should be migrated to register_wf_obligation eventually
1987 let cause = traits::ObligationCause::new(span, self.body_id, code);
1988 self.register_region_obligation(ty, self.tcx.types.re_empty, cause);
1991 /// Registers obligations that all types appearing in `substs` are well-formed.
1992 pub fn add_wf_bounds(&self, substs: &Substs<'tcx>, expr: &hir::Expr)
1994 for ty in substs.types() {
1995 self.register_wf_obligation(ty, expr.span, traits::MiscObligation);
1999 /// Given a fully substituted set of bounds (`generic_bounds`), and the values with which each
2000 /// type/region parameter was instantiated (`substs`), creates and registers suitable
2001 /// trait/region obligations.
2003 /// For example, if there is a function:
2006 /// fn foo<'a,T:'a>(...)
2009 /// and a reference:
2015 /// Then we will create a fresh region variable `'$0` and a fresh type variable `$1` for `'a`
2016 /// and `T`. This routine will add a region obligation `$1:'$0` and register it locally.
2017 pub fn add_obligations_for_parameters(&self,
2018 cause: traits::ObligationCause<'tcx>,
2019 predicates: &ty::InstantiatedPredicates<'tcx>)
2021 assert!(!predicates.has_escaping_regions());
2023 debug!("add_obligations_for_parameters(predicates={:?})",
2026 for obligation in traits::predicates_for_generics(cause, predicates) {
2027 self.register_predicate(obligation);
2031 // FIXME(arielb1): use this instead of field.ty everywhere
2032 // Only for fields! Returns <none> for methods>
2033 // Indifferent to privacy flags
2034 pub fn field_ty(&self,
2036 field: &'tcx ty::FieldDef,
2037 substs: &Substs<'tcx>)
2040 self.normalize_associated_types_in(span,
2041 &field.ty(self.tcx, substs))
2044 fn check_casts(&self) {
2045 let mut deferred_cast_checks = self.deferred_cast_checks.borrow_mut();
2046 for cast in deferred_cast_checks.drain(..) {
2051 /// Apply "fallbacks" to some types
2052 /// unconstrained types get replaced with ! or () (depending on whether
2053 /// feature(never_type) is enabled), unconstrained ints with i32, and
2054 /// unconstrained floats with f64.
2055 fn default_type_parameters(&self) {
2056 use rustc::ty::error::UnconstrainedNumeric::Neither;
2057 use rustc::ty::error::UnconstrainedNumeric::{UnconstrainedInt, UnconstrainedFloat};
2059 // Defaulting inference variables becomes very dubious if we have
2060 // encountered type-checking errors. Therefore, if we think we saw
2061 // some errors in this function, just resolve all uninstanted type
2062 // varibles to TyError.
2063 if self.is_tainted_by_errors() {
2064 for ty in &self.unsolved_variables() {
2065 if let ty::TyInfer(_) = self.shallow_resolve(ty).sty {
2066 debug!("default_type_parameters: defaulting `{:?}` to error", ty);
2067 self.demand_eqtype(syntax_pos::DUMMY_SP, *ty, self.tcx().types.err);
2073 for ty in &self.unsolved_variables() {
2074 let resolved = self.resolve_type_vars_if_possible(ty);
2075 if self.type_var_diverges(resolved) {
2076 debug!("default_type_parameters: defaulting `{:?}` to `!` because it diverges",
2078 self.demand_eqtype(syntax_pos::DUMMY_SP, *ty,
2079 self.tcx.mk_diverging_default());
2081 match self.type_is_unconstrained_numeric(resolved) {
2082 UnconstrainedInt => {
2083 debug!("default_type_parameters: defaulting `{:?}` to `i32`",
2085 self.demand_eqtype(syntax_pos::DUMMY_SP, *ty, self.tcx.types.i32)
2087 UnconstrainedFloat => {
2088 debug!("default_type_parameters: defaulting `{:?}` to `f32`",
2090 self.demand_eqtype(syntax_pos::DUMMY_SP, *ty, self.tcx.types.f64)
2098 // Implements type inference fallback algorithm
2099 fn select_all_obligations_and_apply_defaults(&self) {
2100 self.select_obligations_where_possible();
2101 self.default_type_parameters();
2102 self.select_obligations_where_possible();
2105 fn select_all_obligations_or_error(&self) {
2106 debug!("select_all_obligations_or_error");
2108 // upvar inference should have ensured that all deferred call
2109 // resolutions are handled by now.
2110 assert!(self.deferred_call_resolutions.borrow().is_empty());
2112 self.select_all_obligations_and_apply_defaults();
2114 let mut fulfillment_cx = self.fulfillment_cx.borrow_mut();
2116 match fulfillment_cx.select_all_or_error(self) {
2118 Err(errors) => { self.report_fulfillment_errors(&errors); }
2122 /// Select as many obligations as we can at present.
2123 fn select_obligations_where_possible(&self) {
2124 match self.fulfillment_cx.borrow_mut().select_where_possible(self) {
2126 Err(errors) => { self.report_fulfillment_errors(&errors); }
2130 /// For the overloaded lvalue expressions (`*x`, `x[3]`), the trait
2131 /// returns a type of `&T`, but the actual type we assign to the
2132 /// *expression* is `T`. So this function just peels off the return
2133 /// type by one layer to yield `T`.
2134 fn make_overloaded_lvalue_return_type(&self,
2135 method: MethodCallee<'tcx>)
2136 -> ty::TypeAndMut<'tcx>
2138 // extract method return type, which will be &T;
2139 // all LB regions should have been instantiated during method lookup
2140 let ret_ty = method.sig.output();
2142 // method returns &T, but the type as visible to user is T, so deref
2143 ret_ty.builtin_deref(true, NoPreference).unwrap()
2146 fn lookup_indexing(&self,
2148 base_expr: &'gcx hir::Expr,
2151 lvalue_pref: LvaluePreference)
2152 -> Option<(/*index type*/ Ty<'tcx>, /*element type*/ Ty<'tcx>)>
2154 // FIXME(#18741) -- this is almost but not quite the same as the
2155 // autoderef that normal method probing does. They could likely be
2158 let mut autoderef = self.autoderef(base_expr.span, base_ty);
2159 let mut result = None;
2160 while result.is_none() && autoderef.next().is_some() {
2161 result = self.try_index_step(expr, base_expr, &autoderef, lvalue_pref, idx_ty);
2163 autoderef.finalize();
2167 /// To type-check `base_expr[index_expr]`, we progressively autoderef
2168 /// (and otherwise adjust) `base_expr`, looking for a type which either
2169 /// supports builtin indexing or overloaded indexing.
2170 /// This loop implements one step in that search; the autoderef loop
2171 /// is implemented by `lookup_indexing`.
2172 fn try_index_step(&self,
2174 base_expr: &hir::Expr,
2175 autoderef: &Autoderef<'a, 'gcx, 'tcx>,
2176 lvalue_pref: LvaluePreference,
2178 -> Option<(/*index type*/ Ty<'tcx>, /*element type*/ Ty<'tcx>)>
2180 let adjusted_ty = autoderef.unambiguous_final_ty();
2181 debug!("try_index_step(expr={:?}, base_expr={:?}, adjusted_ty={:?}, \
2189 // First, try built-in indexing.
2190 match (adjusted_ty.builtin_index(), &index_ty.sty) {
2191 (Some(ty), &ty::TyUint(ast::UintTy::Us)) | (Some(ty), &ty::TyInfer(ty::IntVar(_))) => {
2192 debug!("try_index_step: success, using built-in indexing");
2193 let adjustments = autoderef.adjust_steps(lvalue_pref);
2194 self.apply_adjustments(base_expr, adjustments);
2195 return Some((self.tcx.types.usize, ty));
2200 for &unsize in &[false, true] {
2201 let mut self_ty = adjusted_ty;
2203 // We only unsize arrays here.
2204 if let ty::TyArray(element_ty, _) = adjusted_ty.sty {
2205 self_ty = self.tcx.mk_slice(element_ty);
2211 // If some lookup succeeds, write callee into table and extract index/element
2212 // type from the method signature.
2213 // If some lookup succeeded, install method in table
2214 let input_ty = self.next_ty_var(TypeVariableOrigin::AutoDeref(base_expr.span));
2215 let method = self.try_overloaded_lvalue_op(
2216 expr.span, self_ty, &[input_ty], lvalue_pref, LvalueOp::Index);
2218 let result = method.map(|ok| {
2219 debug!("try_index_step: success, using overloaded indexing");
2220 let method = self.register_infer_ok_obligations(ok);
2222 let mut adjustments = autoderef.adjust_steps(lvalue_pref);
2223 if let ty::TyRef(region, mt) = method.sig.inputs()[0].sty {
2224 adjustments.push(Adjustment {
2225 kind: Adjust::Borrow(AutoBorrow::Ref(region, mt.mutbl)),
2226 target: self.tcx.mk_ref(region, ty::TypeAndMut {
2233 adjustments.push(Adjustment {
2234 kind: Adjust::Unsize,
2235 target: method.sig.inputs()[0]
2238 self.apply_adjustments(base_expr, adjustments);
2240 self.write_method_call(expr.id, method);
2241 (input_ty, self.make_overloaded_lvalue_return_type(method).ty)
2243 if result.is_some() {
2251 fn resolve_lvalue_op(&self, op: LvalueOp, is_mut: bool) -> (Option<DefId>, Symbol) {
2252 let (tr, name) = match (op, is_mut) {
2253 (LvalueOp::Deref, false) =>
2254 (self.tcx.lang_items.deref_trait(), "deref"),
2255 (LvalueOp::Deref, true) =>
2256 (self.tcx.lang_items.deref_mut_trait(), "deref_mut"),
2257 (LvalueOp::Index, false) =>
2258 (self.tcx.lang_items.index_trait(), "index"),
2259 (LvalueOp::Index, true) =>
2260 (self.tcx.lang_items.index_mut_trait(), "index_mut"),
2262 (tr, Symbol::intern(name))
2265 fn try_overloaded_lvalue_op(&self,
2268 arg_tys: &[Ty<'tcx>],
2269 lvalue_pref: LvaluePreference,
2271 -> Option<InferOk<'tcx, MethodCallee<'tcx>>>
2273 debug!("try_overloaded_lvalue_op({:?},{:?},{:?},{:?})",
2279 // Try Mut first, if preferred.
2280 let (mut_tr, mut_op) = self.resolve_lvalue_op(op, true);
2281 let method = match (lvalue_pref, mut_tr) {
2282 (PreferMutLvalue, Some(trait_did)) => {
2283 self.lookup_method_in_trait(span, mut_op, trait_did, base_ty, Some(arg_tys))
2288 // Otherwise, fall back to the immutable version.
2289 let (imm_tr, imm_op) = self.resolve_lvalue_op(op, false);
2290 let method = match (method, imm_tr) {
2291 (None, Some(trait_did)) => {
2292 self.lookup_method_in_trait(span, imm_op, trait_did, base_ty, Some(arg_tys))
2294 (method, _) => method,
2300 fn check_method_argument_types(&self,
2302 method: Result<MethodCallee<'tcx>, ()>,
2303 args_no_rcvr: &'gcx [hir::Expr],
2304 tuple_arguments: TupleArgumentsFlag,
2305 expected: Expectation<'tcx>)
2307 let has_error = match method {
2309 method.substs.references_error() || method.sig.references_error()
2314 let err_inputs = self.err_args(args_no_rcvr.len());
2316 let err_inputs = match tuple_arguments {
2317 DontTupleArguments => err_inputs,
2318 TupleArguments => vec![self.tcx.intern_tup(&err_inputs[..], false)],
2321 self.check_argument_types(sp, &err_inputs[..], &[], args_no_rcvr,
2322 false, tuple_arguments, None);
2323 return self.tcx.types.err;
2326 let method = method.unwrap();
2327 // HACK(eddyb) ignore self in the definition (see above).
2328 let expected_arg_tys = self.expected_inputs_for_expected_output(
2331 method.sig.output(),
2332 &method.sig.inputs()[1..]
2334 self.check_argument_types(sp, &method.sig.inputs()[1..], &expected_arg_tys[..],
2335 args_no_rcvr, method.sig.variadic, tuple_arguments,
2336 self.tcx.hir.span_if_local(method.def_id));
2340 /// Generic function that factors out common logic from function calls,
2341 /// method calls and overloaded operators.
2342 fn check_argument_types(&self,
2344 fn_inputs: &[Ty<'tcx>],
2345 expected_arg_tys: &[Ty<'tcx>],
2346 args: &'gcx [hir::Expr],
2348 tuple_arguments: TupleArgumentsFlag,
2349 def_span: Option<Span>) {
2352 // Grab the argument types, supplying fresh type variables
2353 // if the wrong number of arguments were supplied
2354 let supplied_arg_count = if tuple_arguments == DontTupleArguments {
2360 // All the input types from the fn signature must outlive the call
2361 // so as to validate implied bounds.
2362 for &fn_input_ty in fn_inputs {
2363 self.register_wf_obligation(fn_input_ty, sp, traits::MiscObligation);
2366 let mut expected_arg_tys = expected_arg_tys;
2367 let expected_arg_count = fn_inputs.len();
2369 let sp_args = if args.len() > 0 {
2370 let (first, args) = args.split_at(1);
2371 let mut sp_tmp = first[0].span;
2373 let sp_opt = self.sess().codemap().merge_spans(sp_tmp, arg.span);
2374 if ! sp_opt.is_some() {
2377 sp_tmp = sp_opt.unwrap();
2384 fn parameter_count_error<'tcx>(sess: &Session, sp: Span, expected_count: usize,
2385 arg_count: usize, error_code: &str, variadic: bool,
2386 def_span: Option<Span>) {
2387 let mut err = sess.struct_span_err_with_code(sp,
2388 &format!("this function takes {}{} parameter{} but {} parameter{} supplied",
2389 if variadic {"at least "} else {""},
2391 if expected_count == 1 {""} else {"s"},
2393 if arg_count == 1 {" was"} else {"s were"}),
2396 err.span_label(sp, format!("expected {}{} parameter{}",
2397 if variadic {"at least "} else {""},
2399 if expected_count == 1 {""} else {"s"}));
2400 if let Some(def_s) = def_span {
2401 err.span_label(def_s, "defined here");
2406 let formal_tys = if tuple_arguments == TupleArguments {
2407 let tuple_type = self.structurally_resolved_type(sp, fn_inputs[0]);
2408 match tuple_type.sty {
2409 ty::TyTuple(arg_types, _) if arg_types.len() != args.len() => {
2410 parameter_count_error(tcx.sess, sp_args, arg_types.len(), args.len(),
2411 "E0057", false, def_span);
2412 expected_arg_tys = &[];
2413 self.err_args(args.len())
2415 ty::TyTuple(arg_types, _) => {
2416 expected_arg_tys = match expected_arg_tys.get(0) {
2417 Some(&ty) => match ty.sty {
2418 ty::TyTuple(ref tys, _) => &tys,
2426 span_err!(tcx.sess, sp, E0059,
2427 "cannot use call notation; the first type parameter \
2428 for the function trait is neither a tuple nor unit");
2429 expected_arg_tys = &[];
2430 self.err_args(args.len())
2433 } else if expected_arg_count == supplied_arg_count {
2435 } else if variadic {
2436 if supplied_arg_count >= expected_arg_count {
2439 parameter_count_error(tcx.sess, sp_args, expected_arg_count,
2440 supplied_arg_count, "E0060", true, def_span);
2441 expected_arg_tys = &[];
2442 self.err_args(supplied_arg_count)
2445 parameter_count_error(tcx.sess, sp_args, expected_arg_count,
2446 supplied_arg_count, "E0061", false, def_span);
2447 expected_arg_tys = &[];
2448 self.err_args(supplied_arg_count)
2451 debug!("check_argument_types: formal_tys={:?}",
2452 formal_tys.iter().map(|t| self.ty_to_string(*t)).collect::<Vec<String>>());
2454 // Check the arguments.
2455 // We do this in a pretty awful way: first we typecheck any arguments
2456 // that are not closures, then we typecheck the closures. This is so
2457 // that we have more information about the types of arguments when we
2458 // typecheck the functions. This isn't really the right way to do this.
2459 for &check_closures in &[false, true] {
2460 debug!("check_closures={}", check_closures);
2462 // More awful hacks: before we check argument types, try to do
2463 // an "opportunistic" vtable resolution of any trait bounds on
2464 // the call. This helps coercions.
2466 self.select_obligations_where_possible();
2469 // For variadic functions, we don't have a declared type for all of
2470 // the arguments hence we only do our usual type checking with
2471 // the arguments who's types we do know.
2472 let t = if variadic {
2474 } else if tuple_arguments == TupleArguments {
2479 for (i, arg) in args.iter().take(t).enumerate() {
2480 // Warn only for the first loop (the "no closures" one).
2481 // Closure arguments themselves can't be diverging, but
2482 // a previous argument can, e.g. `foo(panic!(), || {})`.
2483 if !check_closures {
2484 self.warn_if_unreachable(arg.id, arg.span, "expression");
2487 let is_closure = match arg.node {
2488 hir::ExprClosure(..) => true,
2492 if is_closure != check_closures {
2496 debug!("checking the argument");
2497 let formal_ty = formal_tys[i];
2499 // The special-cased logic below has three functions:
2500 // 1. Provide as good of an expected type as possible.
2501 let expected = expected_arg_tys.get(i).map(|&ty| {
2502 Expectation::rvalue_hint(self, ty)
2505 let checked_ty = self.check_expr_with_expectation(
2507 expected.unwrap_or(ExpectHasType(formal_ty)));
2509 // 2. Coerce to the most detailed type that could be coerced
2510 // to, which is `expected_ty` if `rvalue_hint` returns an
2511 // `ExpectHasType(expected_ty)`, or the `formal_ty` otherwise.
2512 let coerce_ty = expected.and_then(|e| e.only_has_type(self));
2513 self.demand_coerce(&arg, checked_ty, coerce_ty.unwrap_or(formal_ty));
2515 // 3. Relate the expected type and the formal one,
2516 // if the expected type was used for the coercion.
2517 coerce_ty.map(|ty| self.demand_suptype(arg.span, formal_ty, ty));
2521 // We also need to make sure we at least write the ty of the other
2522 // arguments which we skipped above.
2524 for arg in args.iter().skip(expected_arg_count) {
2525 let arg_ty = self.check_expr(&arg);
2527 // There are a few types which get autopromoted when passed via varargs
2528 // in C but we just error out instead and require explicit casts.
2529 let arg_ty = self.structurally_resolved_type(arg.span,
2532 ty::TyFloat(ast::FloatTy::F32) => {
2533 self.type_error_message(arg.span, |t| {
2534 format!("can't pass an `{}` to variadic \
2535 function, cast to `c_double`", t)
2538 ty::TyInt(ast::IntTy::I8) | ty::TyInt(ast::IntTy::I16) | ty::TyBool => {
2539 self.type_error_message(arg.span, |t| {
2540 format!("can't pass `{}` to variadic \
2541 function, cast to `c_int`",
2545 ty::TyUint(ast::UintTy::U8) | ty::TyUint(ast::UintTy::U16) => {
2546 self.type_error_message(arg.span, |t| {
2547 format!("can't pass `{}` to variadic \
2548 function, cast to `c_uint`",
2552 ty::TyFnDef(.., f) => {
2553 let ptr_ty = self.tcx.mk_fn_ptr(f);
2554 let ptr_ty = self.resolve_type_vars_if_possible(&ptr_ty);
2555 self.type_error_message(arg.span,
2557 format!("can't pass `{}` to variadic \
2558 function, cast to `{}`", t, ptr_ty)
2567 fn err_args(&self, len: usize) -> Vec<Ty<'tcx>> {
2568 (0..len).map(|_| self.tcx.types.err).collect()
2571 // AST fragment checking
2574 expected: Expectation<'tcx>)
2580 ast::LitKind::Str(..) => tcx.mk_static_str(),
2581 ast::LitKind::ByteStr(ref v) => {
2582 tcx.mk_imm_ref(tcx.types.re_static,
2583 tcx.mk_array(tcx.types.u8, v.len()))
2585 ast::LitKind::Byte(_) => tcx.types.u8,
2586 ast::LitKind::Char(_) => tcx.types.char,
2587 ast::LitKind::Int(_, ast::LitIntType::Signed(t)) => tcx.mk_mach_int(t),
2588 ast::LitKind::Int(_, ast::LitIntType::Unsigned(t)) => tcx.mk_mach_uint(t),
2589 ast::LitKind::Int(_, ast::LitIntType::Unsuffixed) => {
2590 let opt_ty = expected.to_option(self).and_then(|ty| {
2592 ty::TyInt(_) | ty::TyUint(_) => Some(ty),
2593 ty::TyChar => Some(tcx.types.u8),
2594 ty::TyRawPtr(..) => Some(tcx.types.usize),
2595 ty::TyFnDef(..) | ty::TyFnPtr(_) => Some(tcx.types.usize),
2599 opt_ty.unwrap_or_else(
2600 || tcx.mk_int_var(self.next_int_var_id()))
2602 ast::LitKind::Float(_, t) => tcx.mk_mach_float(t),
2603 ast::LitKind::FloatUnsuffixed(_) => {
2604 let opt_ty = expected.to_option(self).and_then(|ty| {
2606 ty::TyFloat(_) => Some(ty),
2610 opt_ty.unwrap_or_else(
2611 || tcx.mk_float_var(self.next_float_var_id()))
2613 ast::LitKind::Bool(_) => tcx.types.bool
2617 fn check_expr_eq_type(&self,
2618 expr: &'gcx hir::Expr,
2619 expected: Ty<'tcx>) {
2620 let ty = self.check_expr_with_hint(expr, expected);
2621 self.demand_eqtype(expr.span, expected, ty);
2624 pub fn check_expr_has_type(&self,
2625 expr: &'gcx hir::Expr,
2626 expected: Ty<'tcx>) -> Ty<'tcx> {
2627 let mut ty = self.check_expr_with_hint(expr, expected);
2629 // While we don't allow *arbitrary* coercions here, we *do* allow
2630 // coercions from ! to `expected`.
2632 assert!(!self.tables.borrow().adjustments.contains_key(&expr.id),
2633 "expression with never type wound up being adjusted");
2634 let adj_ty = self.next_diverging_ty_var(
2635 TypeVariableOrigin::AdjustmentType(expr.span));
2636 self.apply_adjustments(expr, vec![Adjustment {
2637 kind: Adjust::NeverToAny,
2643 self.demand_suptype(expr.span, expected, ty);
2647 fn check_expr_coercable_to_type(&self,
2648 expr: &'gcx hir::Expr,
2649 expected: Ty<'tcx>) -> Ty<'tcx> {
2650 let ty = self.check_expr_with_hint(expr, expected);
2651 self.demand_coerce(expr, ty, expected);
2655 fn check_expr_with_hint(&self, expr: &'gcx hir::Expr,
2656 expected: Ty<'tcx>) -> Ty<'tcx> {
2657 self.check_expr_with_expectation(expr, ExpectHasType(expected))
2660 fn check_expr_with_expectation(&self,
2661 expr: &'gcx hir::Expr,
2662 expected: Expectation<'tcx>) -> Ty<'tcx> {
2663 self.check_expr_with_expectation_and_lvalue_pref(expr, expected, NoPreference)
2666 fn check_expr(&self, expr: &'gcx hir::Expr) -> Ty<'tcx> {
2667 self.check_expr_with_expectation(expr, NoExpectation)
2670 fn check_expr_with_lvalue_pref(&self, expr: &'gcx hir::Expr,
2671 lvalue_pref: LvaluePreference) -> Ty<'tcx> {
2672 self.check_expr_with_expectation_and_lvalue_pref(expr, NoExpectation, lvalue_pref)
2675 // determine the `self` type, using fresh variables for all variables
2676 // declared on the impl declaration e.g., `impl<A,B> for Vec<(A,B)>`
2677 // would return ($0, $1) where $0 and $1 are freshly instantiated type
2679 pub fn impl_self_ty(&self,
2680 span: Span, // (potential) receiver for this impl
2682 -> TypeAndSubsts<'tcx> {
2683 let ity = self.tcx.type_of(did);
2684 debug!("impl_self_ty: ity={:?}", ity);
2686 let substs = self.fresh_substs_for_item(span, did);
2687 let substd_ty = self.instantiate_type_scheme(span, &substs, &ity);
2689 TypeAndSubsts { substs: substs, ty: substd_ty }
2692 /// Unifies the output type with the expected type early, for more coercions
2693 /// and forward type information on the input expressions.
2694 fn expected_inputs_for_expected_output(&self,
2696 expected_ret: Expectation<'tcx>,
2697 formal_ret: Ty<'tcx>,
2698 formal_args: &[Ty<'tcx>])
2700 let expected_args = expected_ret.only_has_type(self).and_then(|ret_ty| {
2701 self.fudge_regions_if_ok(&RegionVariableOrigin::Coercion(call_span), || {
2702 // Attempt to apply a subtyping relationship between the formal
2703 // return type (likely containing type variables if the function
2704 // is polymorphic) and the expected return type.
2705 // No argument expectations are produced if unification fails.
2706 let origin = self.misc(call_span);
2707 let ures = self.sub_types(false, &origin, formal_ret, ret_ty);
2709 // FIXME(#15760) can't use try! here, FromError doesn't default
2710 // to identity so the resulting type is not constrained.
2713 // Process any obligations locally as much as
2714 // we can. We don't care if some things turn
2715 // out unconstrained or ambiguous, as we're
2716 // just trying to get hints here.
2717 let result = self.save_and_restore_in_snapshot_flag(|_| {
2718 let mut fulfill = FulfillmentContext::new();
2719 let ok = ok; // FIXME(#30046)
2720 for obligation in ok.obligations {
2721 fulfill.register_predicate_obligation(self, obligation);
2723 fulfill.select_where_possible(self)
2728 Err(_) => return Err(()),
2731 Err(_) => return Err(()),
2734 // Record all the argument types, with the substitutions
2735 // produced from the above subtyping unification.
2736 Ok(formal_args.iter().map(|ty| {
2737 self.resolve_type_vars_if_possible(ty)
2740 }).unwrap_or(vec![]);
2741 debug!("expected_inputs_for_expected_output(formal={:?} -> {:?}, expected={:?} -> {:?})",
2742 formal_args, formal_ret,
2743 expected_args, expected_ret);
2747 // Checks a method call.
2748 fn check_method_call(&self,
2749 expr: &'gcx hir::Expr,
2750 method_name: Spanned<ast::Name>,
2751 args: &'gcx [hir::Expr],
2753 expected: Expectation<'tcx>,
2754 lvalue_pref: LvaluePreference) -> Ty<'tcx> {
2755 let rcvr = &args[0];
2756 let rcvr_t = self.check_expr_with_lvalue_pref(&rcvr, lvalue_pref);
2758 // no need to check for bot/err -- callee does that
2759 let expr_t = self.structurally_resolved_type(expr.span, rcvr_t);
2761 let tps = tps.iter().map(|ast_ty| self.to_ty(&ast_ty)).collect::<Vec<_>>();
2762 let method = match self.lookup_method(method_name.span,
2769 self.write_method_call(expr.id, method);
2773 if method_name.node != keywords::Invalid.name() {
2774 self.report_method_error(method_name.span,
2785 // Call the generic checker.
2786 self.check_method_argument_types(method_name.span, method,
2792 fn check_return_expr(&self, return_expr: &'gcx hir::Expr) {
2796 .unwrap_or_else(|| span_bug!(return_expr.span,
2797 "check_return_expr called outside fn body"));
2799 let ret_ty = ret_coercion.borrow().expected_ty();
2800 let return_expr_ty = self.check_expr_with_hint(return_expr, ret_ty);
2801 ret_coercion.borrow_mut()
2803 &self.misc(return_expr.span),
2806 self.diverges.get());
2810 // A generic function for checking the then and else in an if
2812 fn check_then_else(&self,
2813 cond_expr: &'gcx hir::Expr,
2814 then_expr: &'gcx hir::Expr,
2815 opt_else_expr: Option<&'gcx hir::Expr>,
2817 expected: Expectation<'tcx>) -> Ty<'tcx> {
2818 let cond_ty = self.check_expr_has_type(cond_expr, self.tcx.types.bool);
2819 let cond_diverges = self.diverges.get();
2820 self.diverges.set(Diverges::Maybe);
2822 let expected = expected.adjust_for_branches(self);
2823 let then_ty = self.check_expr_with_expectation(then_expr, expected);
2824 let then_diverges = self.diverges.get();
2825 self.diverges.set(Diverges::Maybe);
2827 // We've already taken the expected type's preferences
2828 // into account when typing the `then` branch. To figure
2829 // out the initial shot at a LUB, we thus only consider
2830 // `expected` if it represents a *hard* constraint
2831 // (`only_has_type`); otherwise, we just go with a
2832 // fresh type variable.
2833 let coerce_to_ty = expected.coercion_target_type(self, sp);
2834 let mut coerce: DynamicCoerceMany = CoerceMany::new(coerce_to_ty);
2836 let if_cause = self.cause(sp, ObligationCauseCode::IfExpression);
2837 coerce.coerce(self, &if_cause, then_expr, then_ty, then_diverges);
2839 if let Some(else_expr) = opt_else_expr {
2840 let else_ty = self.check_expr_with_expectation(else_expr, expected);
2841 let else_diverges = self.diverges.get();
2843 coerce.coerce(self, &if_cause, else_expr, else_ty, else_diverges);
2845 // We won't diverge unless both branches do (or the condition does).
2846 self.diverges.set(cond_diverges | then_diverges & else_diverges);
2848 let else_cause = self.cause(sp, ObligationCauseCode::IfExpressionWithNoElse);
2849 coerce.coerce_forced_unit(self, &else_cause, &mut |_| (), true);
2851 // If the condition is false we can't diverge.
2852 self.diverges.set(cond_diverges);
2855 let result_ty = coerce.complete(self);
2856 if cond_ty.references_error() {
2863 // Check field access expressions
2864 fn check_field(&self,
2865 expr: &'gcx hir::Expr,
2866 lvalue_pref: LvaluePreference,
2867 base: &'gcx hir::Expr,
2868 field: &Spanned<ast::Name>) -> Ty<'tcx> {
2869 let expr_t = self.check_expr_with_lvalue_pref(base, lvalue_pref);
2870 let expr_t = self.structurally_resolved_type(expr.span,
2872 let mut private_candidate = None;
2873 let mut autoderef = self.autoderef(expr.span, expr_t);
2874 while let Some((base_t, _)) = autoderef.next() {
2876 ty::TyAdt(base_def, substs) if !base_def.is_enum() => {
2877 debug!("struct named {:?}", base_t);
2878 let (ident, def_scope) =
2879 self.tcx.adjust(field.node, base_def.did, self.body_id);
2880 let fields = &base_def.struct_variant().fields;
2881 if let Some(field) = fields.iter().find(|f| f.name.to_ident() == ident) {
2882 let field_ty = self.field_ty(expr.span, field, substs);
2883 if field.vis.is_accessible_from(def_scope, self.tcx) {
2884 let adjustments = autoderef.adjust_steps(lvalue_pref);
2885 self.apply_adjustments(base, adjustments);
2886 autoderef.finalize();
2888 self.tcx.check_stability(field.did, expr.id, expr.span);
2892 private_candidate = Some((base_def.did, field_ty));
2898 autoderef.unambiguous_final_ty();
2900 if let Some((did, field_ty)) = private_candidate {
2901 let struct_path = self.tcx().item_path_str(did);
2902 let msg = format!("field `{}` of struct `{}` is private", field.node, struct_path);
2903 let mut err = self.tcx().sess.struct_span_err(expr.span, &msg);
2904 // Also check if an accessible method exists, which is often what is meant.
2905 if self.method_exists(field.span, field.node, expr_t, expr.id, false) {
2906 err.note(&format!("a method `{}` also exists, perhaps you wish to call it",
2911 } else if field.node == keywords::Invalid.name() {
2912 self.tcx().types.err
2913 } else if self.method_exists(field.span, field.node, expr_t, expr.id, true) {
2914 self.type_error_struct(field.span, |actual| {
2915 format!("attempted to take value of method `{}` on type \
2916 `{}`", field.node, actual)
2918 .help("maybe a `()` to call it is missing? \
2919 If not, try an anonymous function")
2921 self.tcx().types.err
2923 let mut err = self.type_error_struct(field.span, |actual| {
2924 format!("no field `{}` on type `{}`",
2928 ty::TyAdt(def, _) if !def.is_enum() => {
2929 if let Some(suggested_field_name) =
2930 Self::suggest_field_name(def.struct_variant(), field, vec![]) {
2931 err.span_label(field.span,
2932 format!("did you mean `{}`?", suggested_field_name));
2934 err.span_label(field.span,
2938 ty::TyRawPtr(..) => {
2939 err.note(&format!("`{0}` is a native pointer; perhaps you need to deref with \
2941 self.tcx.hir.node_to_pretty_string(base.id),
2947 self.tcx().types.err
2951 // Return an hint about the closest match in field names
2952 fn suggest_field_name(variant: &'tcx ty::VariantDef,
2953 field: &Spanned<ast::Name>,
2954 skip : Vec<InternedString>)
2956 let name = field.node.as_str();
2957 let names = variant.fields.iter().filter_map(|field| {
2958 // ignore already set fields and private fields from non-local crates
2959 if skip.iter().any(|x| *x == field.name.as_str()) ||
2960 (variant.did.krate != LOCAL_CRATE && field.vis != Visibility::Public) {
2967 // only find fits with at least one matching letter
2968 find_best_match_for_name(names, &name, Some(name.len()))
2971 // Check tuple index expressions
2972 fn check_tup_field(&self,
2973 expr: &'gcx hir::Expr,
2974 lvalue_pref: LvaluePreference,
2975 base: &'gcx hir::Expr,
2976 idx: codemap::Spanned<usize>) -> Ty<'tcx> {
2977 let expr_t = self.check_expr_with_lvalue_pref(base, lvalue_pref);
2978 let expr_t = self.structurally_resolved_type(expr.span,
2980 let mut private_candidate = None;
2981 let mut tuple_like = false;
2982 let mut autoderef = self.autoderef(expr.span, expr_t);
2983 while let Some((base_t, _)) = autoderef.next() {
2984 let field = match base_t.sty {
2985 ty::TyAdt(base_def, substs) if base_def.is_struct() => {
2986 tuple_like = base_def.struct_variant().ctor_kind == CtorKind::Fn;
2987 if !tuple_like { continue }
2989 debug!("tuple struct named {:?}", base_t);
2990 let ident = ast::Ident {
2991 name: Symbol::intern(&idx.node.to_string()),
2992 ctxt: idx.span.ctxt.modern(),
2994 let (ident, def_scope) =
2995 self.tcx.adjust_ident(ident, base_def.did, self.body_id);
2996 let fields = &base_def.struct_variant().fields;
2997 if let Some(field) = fields.iter().find(|f| f.name.to_ident() == ident) {
2998 let field_ty = self.field_ty(expr.span, field, substs);
2999 if field.vis.is_accessible_from(def_scope, self.tcx) {
3000 self.tcx.check_stability(field.did, expr.id, expr.span);
3003 private_candidate = Some((base_def.did, field_ty));
3010 ty::TyTuple(ref v, _) => {
3012 v.get(idx.node).cloned()
3017 if let Some(field_ty) = field {
3018 let adjustments = autoderef.adjust_steps(lvalue_pref);
3019 self.apply_adjustments(base, adjustments);
3020 autoderef.finalize();
3024 autoderef.unambiguous_final_ty();
3026 if let Some((did, field_ty)) = private_candidate {
3027 let struct_path = self.tcx().item_path_str(did);
3028 let msg = format!("field `{}` of struct `{}` is private", idx.node, struct_path);
3029 self.tcx().sess.span_err(expr.span, &msg);
3033 self.type_error_message(
3037 format!("attempted out-of-bounds tuple index `{}` on \
3042 format!("attempted tuple index `{}` on type `{}`, but the \
3043 type was not a tuple or tuple struct",
3050 self.tcx().types.err
3053 fn report_unknown_field(&self,
3055 variant: &'tcx ty::VariantDef,
3057 skip_fields: &[hir::Field],
3059 let mut err = self.type_error_struct_with_diag(
3061 |actual| match ty.sty {
3062 ty::TyAdt(adt, ..) if adt.is_enum() => {
3063 struct_span_err!(self.tcx.sess, field.name.span, E0559,
3064 "{} `{}::{}` has no field named `{}`",
3065 kind_name, actual, variant.name, field.name.node)
3068 struct_span_err!(self.tcx.sess, field.name.span, E0560,
3069 "{} `{}` has no field named `{}`",
3070 kind_name, actual, field.name.node)
3074 // prevent all specified fields from being suggested
3075 let skip_fields = skip_fields.iter().map(|ref x| x.name.node.as_str());
3076 if let Some(field_name) = Self::suggest_field_name(variant,
3078 skip_fields.collect()) {
3079 err.span_label(field.name.span,
3080 format!("field does not exist - did you mean `{}`?", field_name));
3083 ty::TyAdt(adt, ..) if adt.is_enum() => {
3084 err.span_label(field.name.span, format!("`{}::{}` does not have this field",
3088 err.span_label(field.name.span, format!("`{}` does not have this field", ty));
3095 fn check_expr_struct_fields(&self,
3097 expected: Expectation<'tcx>,
3098 expr_id: ast::NodeId,
3100 variant: &'tcx ty::VariantDef,
3101 ast_fields: &'gcx [hir::Field],
3102 check_completeness: bool) {
3106 self.expected_inputs_for_expected_output(span, expected, adt_ty, &[adt_ty])
3107 .get(0).cloned().unwrap_or(adt_ty);
3109 let (substs, hint_substs, adt_kind, kind_name) = match (&adt_ty.sty, &adt_ty_hint.sty) {
3110 (&ty::TyAdt(adt, substs), &ty::TyAdt(_, hint_substs)) => {
3111 (substs, hint_substs, adt.adt_kind(), adt.variant_descr())
3113 _ => span_bug!(span, "non-ADT passed to check_expr_struct_fields")
3116 let mut remaining_fields = FxHashMap();
3117 for field in &variant.fields {
3118 remaining_fields.insert(field.name.to_ident(), field);
3121 let mut seen_fields = FxHashMap();
3123 let mut error_happened = false;
3125 // Typecheck each field.
3126 for field in ast_fields {
3127 let final_field_type;
3128 let field_type_hint;
3130 let ident = tcx.adjust(field.name.node, variant.did, self.body_id).0;
3131 if let Some(v_field) = remaining_fields.remove(&ident) {
3132 final_field_type = self.field_ty(field.span, v_field, substs);
3133 field_type_hint = self.field_ty(field.span, v_field, hint_substs);
3135 seen_fields.insert(field.name.node, field.span);
3137 // we don't look at stability attributes on
3138 // struct-like enums (yet...), but it's definitely not
3139 // a bug to have construct one.
3140 if adt_kind != ty::AdtKind::Enum {
3141 tcx.check_stability(v_field.did, expr_id, field.span);
3144 error_happened = true;
3145 final_field_type = tcx.types.err;
3146 field_type_hint = tcx.types.err;
3147 if let Some(_) = variant.find_field_named(field.name.node) {
3148 let mut err = struct_span_err!(self.tcx.sess,
3151 "field `{}` specified more than once",
3154 err.span_label(field.name.span, "used more than once");
3156 if let Some(prev_span) = seen_fields.get(&field.name.node) {
3157 err.span_label(*prev_span, format!("first use of `{}`", field.name.node));
3162 self.report_unknown_field(adt_ty, variant, field, ast_fields, kind_name);
3166 // Make sure to give a type to the field even if there's
3167 // an error, so we can continue typechecking
3168 let ty = self.check_expr_with_hint(&field.expr, field_type_hint);
3169 self.demand_coerce(&field.expr, ty, final_field_type);
3172 // Make sure the programmer specified correct number of fields.
3173 if kind_name == "union" {
3174 if ast_fields.len() != 1 {
3175 tcx.sess.span_err(span, "union expressions should have exactly one field");
3177 } else if check_completeness && !error_happened && !remaining_fields.is_empty() {
3178 let len = remaining_fields.len();
3180 let mut displayable_field_names = remaining_fields
3182 .map(|ident| ident.name.as_str())
3183 .collect::<Vec<_>>();
3185 displayable_field_names.sort();
3187 let truncated_fields_error = if len <= 3 {
3190 format!(" and {} other field{}", (len - 3), if len - 3 == 1 {""} else {"s"})
3193 let remaining_fields_names = displayable_field_names.iter().take(3)
3194 .map(|n| format!("`{}`", n))
3195 .collect::<Vec<_>>()
3198 struct_span_err!(tcx.sess, span, E0063,
3199 "missing field{} {}{} in initializer of `{}`",
3200 if remaining_fields.len() == 1 {""} else {"s"},
3201 remaining_fields_names,
3202 truncated_fields_error,
3204 .span_label(span, format!("missing {}{}",
3205 remaining_fields_names,
3206 truncated_fields_error))
3211 fn check_struct_fields_on_error(&self,
3212 fields: &'gcx [hir::Field],
3213 base_expr: &'gcx Option<P<hir::Expr>>) {
3214 for field in fields {
3215 self.check_expr(&field.expr);
3219 self.check_expr(&base);
3225 pub fn check_struct_path(&self,
3227 node_id: ast::NodeId)
3228 -> Option<(&'tcx ty::VariantDef, Ty<'tcx>)> {
3229 let path_span = match *qpath {
3230 hir::QPath::Resolved(_, ref path) => path.span,
3231 hir::QPath::TypeRelative(ref qself, _) => qself.span
3233 let (def, ty) = self.finish_resolving_struct_path(qpath, path_span, node_id);
3234 let variant = match def {
3236 self.set_tainted_by_errors();
3239 Def::Variant(..) => {
3241 ty::TyAdt(adt, substs) => {
3242 Some((adt.variant_of_def(def), adt.did, substs))
3244 _ => bug!("unexpected type: {:?}", ty.sty)
3247 Def::Struct(..) | Def::Union(..) | Def::TyAlias(..) |
3248 Def::AssociatedTy(..) | Def::SelfTy(..) => {
3250 ty::TyAdt(adt, substs) if !adt.is_enum() => {
3251 Some((adt.struct_variant(), adt.did, substs))
3256 _ => bug!("unexpected definition: {:?}", def)
3259 if let Some((variant, did, substs)) = variant {
3260 // Check bounds on type arguments used in the path.
3261 let bounds = self.instantiate_bounds(path_span, did, substs);
3262 let cause = traits::ObligationCause::new(path_span, self.body_id,
3263 traits::ItemObligation(did));
3264 self.add_obligations_for_parameters(cause, &bounds);
3268 struct_span_err!(self.tcx.sess, path_span, E0071,
3269 "expected struct, variant or union type, found {}",
3270 ty.sort_string(self.tcx))
3271 .span_label(path_span, "not a struct")
3277 fn check_expr_struct(&self,
3279 expected: Expectation<'tcx>,
3281 fields: &'gcx [hir::Field],
3282 base_expr: &'gcx Option<P<hir::Expr>>) -> Ty<'tcx>
3284 // Find the relevant variant
3285 let (variant, struct_ty) =
3286 if let Some(variant_ty) = self.check_struct_path(qpath, expr.id) {
3289 self.check_struct_fields_on_error(fields, base_expr);
3290 return self.tcx.types.err;
3293 let path_span = match *qpath {
3294 hir::QPath::Resolved(_, ref path) => path.span,
3295 hir::QPath::TypeRelative(ref qself, _) => qself.span
3298 self.check_expr_struct_fields(struct_ty, expected, expr.id, path_span, variant, fields,
3299 base_expr.is_none());
3300 if let &Some(ref base_expr) = base_expr {
3301 self.check_expr_has_type(base_expr, struct_ty);
3302 match struct_ty.sty {
3303 ty::TyAdt(adt, substs) if adt.is_struct() => {
3304 self.tables.borrow_mut().fru_field_types.insert(
3306 adt.struct_variant().fields.iter().map(|f| {
3307 self.normalize_associated_types_in(
3308 expr.span, &f.ty(self.tcx, substs)
3314 span_err!(self.tcx.sess, base_expr.span, E0436,
3315 "functional record update syntax requires a struct");
3319 self.require_type_is_sized(struct_ty, expr.span, traits::StructInitializerSized);
3325 /// If an expression has any sub-expressions that result in a type error,
3326 /// inspecting that expression's type with `ty.references_error()` will return
3327 /// true. Likewise, if an expression is known to diverge, inspecting its
3328 /// type with `ty::type_is_bot` will return true (n.b.: since Rust is
3329 /// strict, _|_ can appear in the type of an expression that does not,
3330 /// itself, diverge: for example, fn() -> _|_.)
3331 /// Note that inspecting a type's structure *directly* may expose the fact
3332 /// that there are actually multiple representations for `TyError`, so avoid
3333 /// that when err needs to be handled differently.
3334 fn check_expr_with_expectation_and_lvalue_pref(&self,
3335 expr: &'gcx hir::Expr,
3336 expected: Expectation<'tcx>,
3337 lvalue_pref: LvaluePreference) -> Ty<'tcx> {
3338 debug!(">> typechecking: expr={:?} expected={:?}",
3341 // Warn for expressions after diverging siblings.
3342 self.warn_if_unreachable(expr.id, expr.span, "expression");
3344 // Hide the outer diverging and has_errors flags.
3345 let old_diverges = self.diverges.get();
3346 let old_has_errors = self.has_errors.get();
3347 self.diverges.set(Diverges::Maybe);
3348 self.has_errors.set(false);
3350 let ty = self.check_expr_kind(expr, expected, lvalue_pref);
3352 // Warn for non-block expressions with diverging children.
3355 hir::ExprLoop(..) | hir::ExprWhile(..) |
3356 hir::ExprIf(..) | hir::ExprMatch(..) => {}
3358 _ => self.warn_if_unreachable(expr.id, expr.span, "expression")
3361 // Any expression that produces a value of type `!` must have diverged
3363 self.diverges.set(self.diverges.get() | Diverges::Always);
3366 // Record the type, which applies it effects.
3367 // We need to do this after the warning above, so that
3368 // we don't warn for the diverging expression itself.
3369 self.write_ty(expr.id, ty);
3371 // Combine the diverging and has_error flags.
3372 self.diverges.set(self.diverges.get() | old_diverges);
3373 self.has_errors.set(self.has_errors.get() | old_has_errors);
3375 debug!("type of {} is...", self.tcx.hir.node_to_string(expr.id));
3376 debug!("... {:?}, expected is {:?}", ty, expected);
3381 fn check_expr_kind(&self,
3382 expr: &'gcx hir::Expr,
3383 expected: Expectation<'tcx>,
3384 lvalue_pref: LvaluePreference) -> Ty<'tcx> {
3388 hir::ExprBox(ref subexpr) => {
3389 let expected_inner = expected.to_option(self).map_or(NoExpectation, |ty| {
3391 ty::TyAdt(def, _) if def.is_box()
3392 => Expectation::rvalue_hint(self, ty.boxed_ty()),
3396 let referent_ty = self.check_expr_with_expectation(subexpr, expected_inner);
3397 tcx.mk_box(referent_ty)
3400 hir::ExprLit(ref lit) => {
3401 self.check_lit(&lit, expected)
3403 hir::ExprBinary(op, ref lhs, ref rhs) => {
3404 self.check_binop(expr, op, lhs, rhs)
3406 hir::ExprAssignOp(op, ref lhs, ref rhs) => {
3407 self.check_binop_assign(expr, op, lhs, rhs)
3409 hir::ExprUnary(unop, ref oprnd) => {
3410 let expected_inner = match unop {
3411 hir::UnNot | hir::UnNeg => {
3418 let lvalue_pref = match unop {
3419 hir::UnDeref => lvalue_pref,
3422 let mut oprnd_t = self.check_expr_with_expectation_and_lvalue_pref(&oprnd,
3426 if !oprnd_t.references_error() {
3427 oprnd_t = self.structurally_resolved_type(expr.span, oprnd_t);
3430 if let Some(mt) = oprnd_t.builtin_deref(true, NoPreference) {
3432 } else if let Some(ok) = self.try_overloaded_deref(
3433 expr.span, oprnd_t, lvalue_pref) {
3434 let method = self.register_infer_ok_obligations(ok);
3435 if let ty::TyRef(region, mt) = method.sig.inputs()[0].sty {
3436 self.apply_adjustments(oprnd, vec![Adjustment {
3437 kind: Adjust::Borrow(AutoBorrow::Ref(region, mt.mutbl)),
3438 target: method.sig.inputs()[0]
3441 oprnd_t = self.make_overloaded_lvalue_return_type(method).ty;
3442 self.write_method_call(expr.id, method);
3444 self.type_error_message(expr.span, |actual| {
3445 format!("type `{}` cannot be \
3446 dereferenced", actual)
3448 oprnd_t = tcx.types.err;
3452 let result = self.check_user_unop(expr, oprnd_t, unop);
3453 // If it's builtin, we can reuse the type, this helps inference.
3454 if !(oprnd_t.is_integral() || oprnd_t.sty == ty::TyBool) {
3459 let result = self.check_user_unop(expr, oprnd_t, unop);
3460 // If it's builtin, we can reuse the type, this helps inference.
3461 if !(oprnd_t.is_integral() || oprnd_t.is_fp()) {
3469 hir::ExprAddrOf(mutbl, ref oprnd) => {
3470 let hint = expected.only_has_type(self).map_or(NoExpectation, |ty| {
3472 ty::TyRef(_, ref mt) | ty::TyRawPtr(ref mt) => {
3473 if self.tcx.expr_is_lval(&oprnd) {
3474 // Lvalues may legitimately have unsized types.
3475 // For example, dereferences of a fat pointer and
3476 // the last field of a struct can be unsized.
3477 ExpectHasType(mt.ty)
3479 Expectation::rvalue_hint(self, mt.ty)
3485 let lvalue_pref = LvaluePreference::from_mutbl(mutbl);
3486 let ty = self.check_expr_with_expectation_and_lvalue_pref(&oprnd, hint, lvalue_pref);
3488 let tm = ty::TypeAndMut { ty: ty, mutbl: mutbl };
3489 if tm.ty.references_error() {
3492 // Note: at this point, we cannot say what the best lifetime
3493 // is to use for resulting pointer. We want to use the
3494 // shortest lifetime possible so as to avoid spurious borrowck
3495 // errors. Moreover, the longest lifetime will depend on the
3496 // precise details of the value whose address is being taken
3497 // (and how long it is valid), which we don't know yet until type
3498 // inference is complete.
3500 // Therefore, here we simply generate a region variable. The
3501 // region inferencer will then select the ultimate value.
3502 // Finally, borrowck is charged with guaranteeing that the
3503 // value whose address was taken can actually be made to live
3504 // as long as it needs to live.
3505 let region = self.next_region_var(infer::AddrOfRegion(expr.span));
3506 tcx.mk_ref(region, tm)
3509 hir::ExprPath(ref qpath) => {
3510 let (def, opt_ty, segments) = self.resolve_ty_and_def_ufcs(qpath,
3511 expr.id, expr.span);
3512 let ty = if def != Def::Err {
3513 self.instantiate_value_path(segments, opt_ty, def, expr.span, id)
3515 self.set_tainted_by_errors();
3519 // We always require that the type provided as the value for
3520 // a type parameter outlives the moment of instantiation.
3521 let substs = self.tables.borrow().node_substs(expr.id);
3522 self.add_wf_bounds(substs, expr);
3526 hir::ExprInlineAsm(_, ref outputs, ref inputs) => {
3527 for output in outputs {
3528 self.check_expr(output);
3530 for input in inputs {
3531 self.check_expr(input);
3535 hir::ExprBreak(destination, ref expr_opt) => {
3536 if let Some(target_id) = destination.target_id.opt_id() {
3537 let (e_ty, e_diverges, cause);
3538 if let Some(ref e) = *expr_opt {
3539 // If this is a break with a value, we need to type-check
3540 // the expression. Get an expected type from the loop context.
3541 let opt_coerce_to = {
3542 let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
3543 enclosing_breakables.find_breakable(target_id)
3546 .map(|coerce| coerce.expected_ty())
3549 // If the loop context is not a `loop { }`, then break with
3550 // a value is illegal, and `opt_coerce_to` will be `None`.
3551 // Just set expectation to error in that case.
3552 let coerce_to = opt_coerce_to.unwrap_or(tcx.types.err);
3554 // Recurse without `enclosing_breakables` borrowed.
3555 e_ty = self.check_expr_with_hint(e, coerce_to);
3556 e_diverges = self.diverges.get();
3557 cause = self.misc(e.span);
3559 // Otherwise, this is a break *without* a value. That's
3560 // always legal, and is equivalent to `break ()`.
3561 e_ty = tcx.mk_nil();
3562 e_diverges = Diverges::Maybe;
3563 cause = self.misc(expr.span);
3566 // Now that we have type-checked `expr_opt`, borrow
3567 // the `enclosing_loops` field and let's coerce the
3568 // type of `expr_opt` into what is expected.
3569 let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
3570 let ctxt = enclosing_breakables.find_breakable(target_id);
3571 if let Some(ref mut coerce) = ctxt.coerce {
3572 if let Some(ref e) = *expr_opt {
3573 coerce.coerce(self, &cause, e, e_ty, e_diverges);
3575 assert!(e_ty.is_nil());
3576 coerce.coerce_forced_unit(self, &cause, &mut |_| (), true);
3579 // If `ctxt.coerce` is `None`, we can just ignore
3580 // the type of the expresison. This is because
3581 // either this was a break *without* a value, in
3582 // which case it is always a legal type (`()`), or
3583 // else an error would have been flagged by the
3584 // `loops` pass for using break with an expression
3585 // where you are not supposed to.
3586 assert!(expr_opt.is_none() || self.tcx.sess.err_count() > 0);
3589 ctxt.may_break = true;
3591 // Otherwise, we failed to find the enclosing loop;
3592 // this can only happen if the `break` was not
3593 // inside a loop at all, which is caught by the
3594 // loop-checking pass.
3595 assert!(self.tcx.sess.err_count() > 0);
3598 // the type of a `break` is always `!`, since it diverges
3601 hir::ExprAgain(_) => { tcx.types.never }
3602 hir::ExprRet(ref expr_opt) => {
3603 if self.ret_coercion.is_none() {
3604 struct_span_err!(self.tcx.sess, expr.span, E0572,
3605 "return statement outside of function body").emit();
3606 } else if let Some(ref e) = *expr_opt {
3607 self.check_return_expr(e);
3609 let mut coercion = self.ret_coercion.as_ref().unwrap().borrow_mut();
3610 let cause = self.cause(expr.span, ObligationCauseCode::ReturnNoExpression);
3611 coercion.coerce_forced_unit(self, &cause, &mut |_| (), true);
3615 hir::ExprAssign(ref lhs, ref rhs) => {
3616 let lhs_ty = self.check_expr_with_lvalue_pref(&lhs, PreferMutLvalue);
3619 if !tcx.expr_is_lval(&lhs) {
3621 tcx.sess, expr.span, E0070,
3622 "invalid left-hand side expression")
3625 "left-hand of expression not valid")
3629 let rhs_ty = self.check_expr_coercable_to_type(&rhs, lhs_ty);
3631 self.require_type_is_sized(lhs_ty, lhs.span, traits::AssignmentLhsSized);
3633 if lhs_ty.references_error() || rhs_ty.references_error() {
3639 hir::ExprIf(ref cond, ref then_expr, ref opt_else_expr) => {
3640 self.check_then_else(&cond, then_expr, opt_else_expr.as_ref().map(|e| &**e),
3641 expr.span, expected)
3643 hir::ExprWhile(ref cond, ref body, _) => {
3644 let ctxt = BreakableCtxt {
3645 // cannot use break with a value from a while loop
3650 self.with_breakable_ctxt(expr.id, ctxt, || {
3651 self.check_expr_has_type(&cond, tcx.types.bool);
3652 let cond_diverging = self.diverges.get();
3653 self.check_block_no_value(&body);
3655 // We may never reach the body so it diverging means nothing.
3656 self.diverges.set(cond_diverging);
3661 hir::ExprLoop(ref body, _, source) => {
3662 let coerce = match source {
3663 // you can only use break with a value from a normal `loop { }`
3664 hir::LoopSource::Loop => {
3665 let coerce_to = expected.coercion_target_type(self, body.span);
3666 Some(CoerceMany::new(coerce_to))
3669 hir::LoopSource::WhileLet |
3670 hir::LoopSource::ForLoop => {
3675 let ctxt = BreakableCtxt {
3677 may_break: false, // will get updated if/when we find a `break`
3680 let (ctxt, ()) = self.with_breakable_ctxt(expr.id, ctxt, || {
3681 self.check_block_no_value(&body);
3685 // No way to know whether it's diverging because
3686 // of a `break` or an outer `break` or `return.
3687 self.diverges.set(Diverges::Maybe);
3690 // If we permit break with a value, then result type is
3691 // the LUB of the breaks (possibly ! if none); else, it
3692 // is nil. This makes sense because infinite loops
3693 // (which would have type !) are only possible iff we
3694 // permit break with a value [1].
3695 assert!(ctxt.coerce.is_some() || ctxt.may_break); // [1]
3696 ctxt.coerce.map(|c| c.complete(self)).unwrap_or(self.tcx.mk_nil())
3698 hir::ExprMatch(ref discrim, ref arms, match_src) => {
3699 self.check_match(expr, &discrim, arms, expected, match_src)
3701 hir::ExprClosure(capture, ref decl, body_id, _) => {
3702 self.check_expr_closure(expr, capture, &decl, body_id, expected)
3704 hir::ExprBlock(ref body) => {
3705 self.check_block_with_expected(&body, expected)
3707 hir::ExprCall(ref callee, ref args) => {
3708 self.check_call(expr, &callee, args, expected)
3710 hir::ExprMethodCall(name, ref tps, ref args) => {
3711 self.check_method_call(expr, name, args, &tps[..], expected, lvalue_pref)
3713 hir::ExprCast(ref e, ref t) => {
3714 // Find the type of `e`. Supply hints based on the type we are casting to,
3716 let t_cast = self.to_ty(t);
3717 let t_cast = self.resolve_type_vars_if_possible(&t_cast);
3718 let t_expr = self.check_expr_with_expectation(e, ExpectCastableToType(t_cast));
3719 let t_cast = self.resolve_type_vars_if_possible(&t_cast);
3720 let diverges = self.diverges.get();
3722 // Eagerly check for some obvious errors.
3723 if t_expr.references_error() || t_cast.references_error() {
3726 // Defer other checks until we're done type checking.
3727 let mut deferred_cast_checks = self.deferred_cast_checks.borrow_mut();
3728 match cast::CastCheck::new(self, e, t_expr, diverges, t_cast, t.span, expr.span) {
3730 deferred_cast_checks.push(cast_check);
3733 Err(ErrorReported) => {
3739 hir::ExprType(ref e, ref t) => {
3740 let typ = self.to_ty(&t);
3741 self.check_expr_eq_type(&e, typ);
3744 hir::ExprArray(ref args) => {
3745 let uty = expected.to_option(self).and_then(|uty| {
3747 ty::TyArray(ty, _) | ty::TySlice(ty) => Some(ty),
3752 let element_ty = if !args.is_empty() {
3753 let coerce_to = uty.unwrap_or_else(
3754 || self.next_ty_var(TypeVariableOrigin::TypeInference(expr.span)));
3755 let mut coerce = CoerceMany::with_coercion_sites(coerce_to, args);
3756 assert_eq!(self.diverges.get(), Diverges::Maybe);
3758 let e_ty = self.check_expr_with_hint(e, coerce_to);
3759 let cause = self.misc(e.span);
3760 coerce.coerce(self, &cause, e, e_ty, self.diverges.get());
3762 coerce.complete(self)
3764 self.next_ty_var(TypeVariableOrigin::TypeInference(expr.span))
3766 tcx.mk_array(element_ty, args.len())
3768 hir::ExprRepeat(ref element, count) => {
3769 let count = eval_length(self.tcx, count, "repeat count")
3772 let uty = match expected {
3773 ExpectHasType(uty) => {
3775 ty::TyArray(ty, _) | ty::TySlice(ty) => Some(ty),
3782 let (element_ty, t) = match uty {
3784 self.check_expr_coercable_to_type(&element, uty);
3788 let t: Ty = self.next_ty_var(TypeVariableOrigin::MiscVariable(element.span));
3789 let element_ty = self.check_expr_has_type(&element, t);
3795 // For [foo, ..n] where n > 1, `foo` must have
3797 let lang_item = self.tcx.require_lang_item(lang_items::CopyTraitLangItem);
3798 self.require_type_meets(t, expr.span, traits::RepeatVec, lang_item);
3801 if element_ty.references_error() {
3804 tcx.mk_array(t, count)
3807 hir::ExprTup(ref elts) => {
3808 let flds = expected.only_has_type(self).and_then(|ty| {
3810 ty::TyTuple(ref flds, _) => Some(&flds[..]),
3815 let elt_ts_iter = elts.iter().enumerate().map(|(i, e)| {
3816 let t = match flds {
3817 Some(ref fs) if i < fs.len() => {
3819 self.check_expr_coercable_to_type(&e, ety);
3823 self.check_expr_with_expectation(&e, NoExpectation)
3828 let tuple = tcx.mk_tup(elt_ts_iter, false);
3829 if tuple.references_error() {
3835 hir::ExprStruct(ref qpath, ref fields, ref base_expr) => {
3836 self.check_expr_struct(expr, expected, qpath, fields, base_expr)
3838 hir::ExprField(ref base, ref field) => {
3839 self.check_field(expr, lvalue_pref, &base, field)
3841 hir::ExprTupField(ref base, idx) => {
3842 self.check_tup_field(expr, lvalue_pref, &base, idx)
3844 hir::ExprIndex(ref base, ref idx) => {
3845 let base_t = self.check_expr_with_lvalue_pref(&base, lvalue_pref);
3846 let idx_t = self.check_expr(&idx);
3848 if base_t.references_error() {
3850 } else if idx_t.references_error() {
3853 let base_t = self.structurally_resolved_type(expr.span, base_t);
3854 match self.lookup_indexing(expr, base, base_t, idx_t, lvalue_pref) {
3855 Some((index_ty, element_ty)) => {
3856 self.demand_coerce(idx, idx_t, index_ty);
3860 let mut err = self.type_error_struct(
3863 format!("cannot index a value of type `{}`",
3867 // Try to give some advice about indexing tuples.
3868 if let ty::TyTuple(..) = base_t.sty {
3869 let mut needs_note = true;
3870 // If the index is an integer, we can show the actual
3871 // fixed expression:
3872 if let hir::ExprLit(ref lit) = idx.node {
3873 if let ast::LitKind::Int(i,
3874 ast::LitIntType::Unsuffixed) = lit.node {
3875 let snip = tcx.sess.codemap().span_to_snippet(base.span);
3876 if let Ok(snip) = snip {
3877 err.span_suggestion(expr.span,
3878 "to access tuple elements, use",
3879 format!("{}.{}", snip, i));
3885 err.help("to access tuple elements, use tuple indexing \
3886 syntax (e.g. `tuple.0`)");
3898 // Finish resolving a path in a struct expression or pattern `S::A { .. }` if necessary.
3899 // The newly resolved definition is written into `type_dependent_defs`.
3900 fn finish_resolving_struct_path(&self,
3903 node_id: ast::NodeId)
3907 hir::QPath::Resolved(ref maybe_qself, ref path) => {
3908 let opt_self_ty = maybe_qself.as_ref().map(|qself| self.to_ty(qself));
3909 let ty = AstConv::def_to_ty(self, opt_self_ty, path, true);
3912 hir::QPath::TypeRelative(ref qself, ref segment) => {
3913 let ty = self.to_ty(qself);
3915 let def = if let hir::TyPath(hir::QPath::Resolved(_, ref path)) = qself.node {
3920 let (ty, def) = AstConv::associated_path_def_to_ty(self, node_id, path_span,
3923 // Write back the new resolution.
3924 self.tables.borrow_mut().type_dependent_defs.insert(node_id, def);
3931 // Resolve associated value path into a base type and associated constant or method definition.
3932 // The newly resolved definition is written into `type_dependent_defs`.
3933 pub fn resolve_ty_and_def_ufcs<'b>(&self,
3934 qpath: &'b hir::QPath,
3935 node_id: ast::NodeId,
3937 -> (Def, Option<Ty<'tcx>>, &'b [hir::PathSegment])
3939 let (ty, item_segment) = match *qpath {
3940 hir::QPath::Resolved(ref opt_qself, ref path) => {
3942 opt_qself.as_ref().map(|qself| self.to_ty(qself)),
3943 &path.segments[..]);
3945 hir::QPath::TypeRelative(ref qself, ref segment) => {
3946 (self.to_ty(qself), segment)
3949 let item_name = item_segment.name;
3950 let def = match self.resolve_ufcs(span, item_name, ty, node_id) {
3953 let def = match error {
3954 method::MethodError::PrivateMatch(def) => def,
3957 if item_name != keywords::Invalid.name() {
3958 self.report_method_error(span, ty, item_name, None, error, None);
3964 // Write back the new resolution.
3965 self.tables.borrow_mut().type_dependent_defs.insert(node_id, def);
3966 (def, Some(ty), slice::ref_slice(&**item_segment))
3969 pub fn check_decl_initializer(&self,
3970 local: &'gcx hir::Local,
3971 init: &'gcx hir::Expr) -> Ty<'tcx>
3973 let ref_bindings = local.pat.contains_ref_binding();
3975 let local_ty = self.local_ty(init.span, local.id);
3976 if let Some(m) = ref_bindings {
3977 // Somewhat subtle: if we have a `ref` binding in the pattern,
3978 // we want to avoid introducing coercions for the RHS. This is
3979 // both because it helps preserve sanity and, in the case of
3980 // ref mut, for soundness (issue #23116). In particular, in
3981 // the latter case, we need to be clear that the type of the
3982 // referent for the reference that results is *equal to* the
3983 // type of the lvalue it is referencing, and not some
3984 // supertype thereof.
3985 let init_ty = self.check_expr_with_lvalue_pref(init, LvaluePreference::from_mutbl(m));
3986 self.demand_eqtype(init.span, init_ty, local_ty);
3989 self.check_expr_coercable_to_type(init, local_ty)
3993 pub fn check_decl_local(&self, local: &'gcx hir::Local) {
3994 let t = self.local_ty(local.span, local.id);
3995 self.write_ty(local.id, t);
3997 if let Some(ref init) = local.init {
3998 let init_ty = self.check_decl_initializer(local, &init);
3999 if init_ty.references_error() {
4000 self.write_ty(local.id, init_ty);
4004 self.check_pat(&local.pat, t);
4005 let pat_ty = self.node_ty(local.pat.id);
4006 if pat_ty.references_error() {
4007 self.write_ty(local.id, pat_ty);
4011 pub fn check_stmt(&self, stmt: &'gcx hir::Stmt) {
4012 // Don't do all the complex logic below for DeclItem.
4014 hir::StmtDecl(ref decl, id) => {
4016 hir::DeclLocal(_) => {}
4017 hir::DeclItem(_) => {
4023 hir::StmtExpr(..) | hir::StmtSemi(..) => {}
4026 self.warn_if_unreachable(stmt.node.id(), stmt.span, "statement");
4028 // Hide the outer diverging and has_errors flags.
4029 let old_diverges = self.diverges.get();
4030 let old_has_errors = self.has_errors.get();
4031 self.diverges.set(Diverges::Maybe);
4032 self.has_errors.set(false);
4034 let (node_id, _span) = match stmt.node {
4035 hir::StmtDecl(ref decl, id) => {
4036 let span = match decl.node {
4037 hir::DeclLocal(ref l) => {
4038 self.check_decl_local(&l);
4041 hir::DeclItem(_) => {/* ignore for now */
4047 hir::StmtExpr(ref expr, id) => {
4048 // Check with expected type of ()
4049 self.check_expr_has_type(&expr, self.tcx.mk_nil());
4052 hir::StmtSemi(ref expr, id) => {
4053 self.check_expr(&expr);
4058 if self.has_errors.get() {
4059 self.write_error(node_id);
4061 self.write_nil(node_id);
4064 // Combine the diverging and has_error flags.
4065 self.diverges.set(self.diverges.get() | old_diverges);
4066 self.has_errors.set(self.has_errors.get() | old_has_errors);
4069 pub fn check_block_no_value(&self, blk: &'gcx hir::Block) {
4070 let unit = self.tcx.mk_nil();
4071 let ty = self.check_block_with_expected(blk, ExpectHasType(unit));
4073 // if the block produces a `!` value, that can always be
4074 // (effectively) coerced to unit.
4076 self.demand_suptype(blk.span, unit, ty);
4080 fn check_block_with_expected(&self,
4081 blk: &'gcx hir::Block,
4082 expected: Expectation<'tcx>) -> Ty<'tcx> {
4084 let mut fcx_ps = self.ps.borrow_mut();
4085 let unsafety_state = fcx_ps.recurse(blk);
4086 replace(&mut *fcx_ps, unsafety_state)
4089 // In some cases, blocks have just one exit, but other blocks
4090 // can be targeted by multiple breaks. This cannot happen in
4091 // normal Rust syntax today, but it can happen when we desugar
4092 // a `do catch { ... }` expression.
4096 // 'a: { if true { break 'a Err(()); } Ok(()) }
4098 // Here we would wind up with two coercions, one from
4099 // `Err(())` and the other from the tail expression
4100 // `Ok(())`. If the tail expression is omitted, that's a
4101 // "forced unit" -- unless the block diverges, in which
4102 // case we can ignore the tail expression (e.g., `'a: {
4103 // break 'a 22; }` would not force the type of the block
4105 let tail_expr = blk.expr.as_ref();
4106 let coerce_to_ty = expected.coercion_target_type(self, blk.span);
4107 let coerce = if blk.targeted_by_break {
4108 CoerceMany::new(coerce_to_ty)
4110 let tail_expr: &[P<hir::Expr>] = match tail_expr {
4111 Some(e) => ref_slice(e),
4114 CoerceMany::with_coercion_sites(coerce_to_ty, tail_expr)
4117 let ctxt = BreakableCtxt {
4118 coerce: Some(coerce),
4122 let (ctxt, ()) = self.with_breakable_ctxt(blk.id, ctxt, || {
4123 for s in &blk.stmts {
4127 // check the tail expression **without** holding the
4128 // `enclosing_breakables` lock below.
4129 let tail_expr_ty = tail_expr.map(|t| self.check_expr_with_expectation(t, expected));
4131 let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
4132 let mut ctxt = enclosing_breakables.find_breakable(blk.id);
4133 let mut coerce = ctxt.coerce.as_mut().unwrap();
4134 if let Some(tail_expr_ty) = tail_expr_ty {
4135 let tail_expr = tail_expr.unwrap();
4137 &self.misc(tail_expr.span),
4140 self.diverges.get());
4142 // Subtle: if there is no explicit tail expression,
4143 // that is typically equivalent to a tail expression
4144 // of `()` -- except if the block diverges. In that
4145 // case, there is no value supplied from the tail
4146 // expression (assuming there are no other breaks,
4147 // this implies that the type of the block will be
4150 // #41425 -- label the implicit `()` as being the
4151 // "found type" here, rather than the "expected type".
4152 if !self.diverges.get().always() {
4153 coerce.coerce_forced_unit(self, &self.misc(blk.span), &mut |err| {
4154 if let Some(expected_ty) = expected.only_has_type(self) {
4155 self.consider_hint_about_removing_semicolon(blk,
4164 let mut ty = ctxt.coerce.unwrap().complete(self);
4166 if self.has_errors.get() || ty.references_error() {
4167 ty = self.tcx.types.err
4170 self.write_ty(blk.id, ty);
4172 *self.ps.borrow_mut() = prev;
4176 /// A common error is to add an extra semicolon:
4179 /// fn foo() -> usize {
4184 /// This routine checks if the final statement in a block is an
4185 /// expression with an explicit semicolon whose type is compatible
4186 /// with `expected_ty`. If so, it suggests removing the semicolon.
4187 fn consider_hint_about_removing_semicolon(&self,
4188 blk: &'gcx hir::Block,
4189 expected_ty: Ty<'tcx>,
4190 err: &mut DiagnosticBuilder) {
4191 // Be helpful when the user wrote `{... expr;}` and
4192 // taking the `;` off is enough to fix the error.
4193 let last_stmt = match blk.stmts.last() {
4197 let last_expr = match last_stmt.node {
4198 hir::StmtSemi(ref e, _) => e,
4201 let last_expr_ty = self.expr_ty(last_expr);
4202 if self.can_sub_types(last_expr_ty, expected_ty).is_err() {
4205 let original_span = original_sp(last_stmt.span, blk.span);
4206 let span_semi = Span {
4207 lo: original_span.hi - BytePos(1),
4208 hi: original_span.hi,
4209 ctxt: original_span.ctxt,
4211 err.span_help(span_semi, "consider removing this semicolon:");
4214 // Instantiates the given path, which must refer to an item with the given
4215 // number of type parameters and type.
4216 pub fn instantiate_value_path(&self,
4217 segments: &[hir::PathSegment],
4218 opt_self_ty: Option<Ty<'tcx>>,
4221 node_id: ast::NodeId)
4223 debug!("instantiate_value_path(path={:?}, def={:?}, node_id={})",
4228 // We need to extract the type parameters supplied by the user in
4229 // the path `path`. Due to the current setup, this is a bit of a
4230 // tricky-process; the problem is that resolve only tells us the
4231 // end-point of the path resolution, and not the intermediate steps.
4232 // Luckily, we can (at least for now) deduce the intermediate steps
4233 // just from the end-point.
4235 // There are basically four cases to consider:
4237 // 1. Reference to a constructor of enum variant or struct:
4239 // struct Foo<T>(...)
4240 // enum E<T> { Foo(...) }
4242 // In these cases, the parameters are declared in the type
4245 // 2. Reference to a fn item or a free constant:
4249 // In this case, the path will again always have the form
4250 // `a::b::foo::<T>` where only the final segment should have
4251 // type parameters. However, in this case, those parameters are
4252 // declared on a value, and hence are in the `FnSpace`.
4254 // 3. Reference to a method or an associated constant:
4256 // impl<A> SomeStruct<A> {
4260 // Here we can have a path like
4261 // `a::b::SomeStruct::<A>::foo::<B>`, in which case parameters
4262 // may appear in two places. The penultimate segment,
4263 // `SomeStruct::<A>`, contains parameters in TypeSpace, and the
4264 // final segment, `foo::<B>` contains parameters in fn space.
4266 // 4. Reference to a local variable
4268 // Local variables can't have any type parameters.
4270 // The first step then is to categorize the segments appropriately.
4272 assert!(!segments.is_empty());
4274 let mut ufcs_associated = None;
4275 let mut type_segment = None;
4276 let mut fn_segment = None;
4278 // Case 1. Reference to a struct/variant constructor.
4279 Def::StructCtor(def_id, ..) |
4280 Def::VariantCtor(def_id, ..) => {
4281 // Everything but the final segment should have no
4282 // parameters at all.
4283 let mut generics = self.tcx.generics_of(def_id);
4284 if let Some(def_id) = generics.parent {
4285 // Variant and struct constructors use the
4286 // generics of their parent type definition.
4287 generics = self.tcx.generics_of(def_id);
4289 type_segment = Some((segments.last().unwrap(), generics));
4292 // Case 2. Reference to a top-level value.
4294 Def::Const(def_id) |
4295 Def::Static(def_id, _) => {
4296 fn_segment = Some((segments.last().unwrap(),
4297 self.tcx.generics_of(def_id)));
4300 // Case 3. Reference to a method or associated const.
4301 Def::Method(def_id) |
4302 Def::AssociatedConst(def_id) => {
4303 let container = self.tcx.associated_item(def_id).container;
4305 ty::TraitContainer(trait_did) => {
4306 callee::check_legal_trait_for_method_call(self.tcx, span, trait_did)
4308 ty::ImplContainer(_) => {}
4311 let generics = self.tcx.generics_of(def_id);
4312 if segments.len() >= 2 {
4313 let parent_generics = self.tcx.generics_of(generics.parent.unwrap());
4314 type_segment = Some((&segments[segments.len() - 2], parent_generics));
4316 // `<T>::assoc` will end up here, and so can `T::assoc`.
4317 let self_ty = opt_self_ty.expect("UFCS sugared assoc missing Self");
4318 ufcs_associated = Some((container, self_ty));
4320 fn_segment = Some((segments.last().unwrap(), generics));
4323 // Case 4. Local variable, no generics.
4324 Def::Local(..) | Def::Upvar(..) => {}
4326 _ => bug!("unexpected definition: {:?}", def),
4329 debug!("type_segment={:?} fn_segment={:?}", type_segment, fn_segment);
4331 // Now that we have categorized what space the parameters for each
4332 // segment belong to, let's sort out the parameters that the user
4333 // provided (if any) into their appropriate spaces. We'll also report
4334 // errors if type parameters are provided in an inappropriate place.
4335 let poly_segments = type_segment.is_some() as usize +
4336 fn_segment.is_some() as usize;
4337 AstConv::prohibit_type_params(self, &segments[..segments.len() - poly_segments]);
4340 Def::Local(def_id) | Def::Upvar(def_id, ..) => {
4341 let nid = self.tcx.hir.as_local_node_id(def_id).unwrap();
4342 let ty = self.local_ty(span, nid);
4343 let ty = self.normalize_associated_types_in(span, &ty);
4344 self.write_ty(node_id, ty);
4350 // Now we have to compare the types that the user *actually*
4351 // provided against the types that were *expected*. If the user
4352 // did not provide any types, then we want to substitute inference
4353 // variables. If the user provided some types, we may still need
4354 // to add defaults. If the user provided *too many* types, that's
4356 self.check_path_parameter_count(span, &mut type_segment);
4357 self.check_path_parameter_count(span, &mut fn_segment);
4359 let (fn_start, has_self) = match (type_segment, fn_segment) {
4360 (_, Some((_, generics))) => {
4361 (generics.parent_count(), generics.has_self)
4363 (Some((_, generics)), None) => {
4364 (generics.own_count(), generics.has_self)
4366 (None, None) => (0, false)
4368 let substs = Substs::for_item(self.tcx, def.def_id(), |def, _| {
4369 let mut i = def.index as usize;
4371 let segment = if i < fn_start {
4372 i -= has_self as usize;
4378 let lifetimes = match segment.map(|(s, _)| &s.parameters) {
4379 Some(&hir::AngleBracketedParameters(ref data)) => &data.lifetimes[..],
4380 Some(&hir::ParenthesizedParameters(_)) => bug!(),
4384 if let Some(lifetime) = lifetimes.get(i) {
4385 AstConv::ast_region_to_region(self, lifetime, Some(def))
4387 self.re_infer(span, Some(def)).unwrap()
4390 let mut i = def.index as usize;
4392 let segment = if i < fn_start {
4393 // Handle Self first, so we can adjust the index to match the AST.
4394 if has_self && i == 0 {
4395 return opt_self_ty.unwrap_or_else(|| {
4396 self.type_var_for_def(span, def, substs)
4399 i -= has_self as usize;
4405 let (types, infer_types) = match segment.map(|(s, _)| &s.parameters) {
4406 Some(&hir::AngleBracketedParameters(ref data)) => {
4407 (&data.types[..], data.infer_types)
4409 Some(&hir::ParenthesizedParameters(_)) => bug!(),
4410 None => (&[][..], true)
4413 // Skip over the lifetimes in the same segment.
4414 if let Some((_, generics)) = segment {
4415 i -= generics.regions.len();
4418 if let Some(ast_ty) = types.get(i) {
4419 // A provided type parameter.
4421 } else if !infer_types && def.has_default {
4422 // No type parameter provided, but a default exists.
4423 let default = self.tcx.type_of(def.def_id);
4426 default.subst_spanned(self.tcx, substs, Some(span))
4429 // No type parameters were provided, we can infer all.
4430 // This can also be reached in some error cases:
4431 // We prefer to use inference variables instead of
4432 // TyError to let type inference recover somewhat.
4433 self.type_var_for_def(span, def, substs)
4437 // The things we are substituting into the type should not contain
4438 // escaping late-bound regions, and nor should the base type scheme.
4439 let ty = self.tcx.type_of(def.def_id());
4440 assert!(!substs.has_escaping_regions());
4441 assert!(!ty.has_escaping_regions());
4443 // Add all the obligations that are required, substituting and
4444 // normalized appropriately.
4445 let bounds = self.instantiate_bounds(span, def.def_id(), &substs);
4446 self.add_obligations_for_parameters(
4447 traits::ObligationCause::new(span, self.body_id, traits::ItemObligation(def.def_id())),
4450 // Substitute the values for the type parameters into the type of
4451 // the referenced item.
4452 let ty_substituted = self.instantiate_type_scheme(span, &substs, &ty);
4454 if let Some((ty::ImplContainer(impl_def_id), self_ty)) = ufcs_associated {
4455 // In the case of `Foo<T>::method` and `<Foo<T>>::method`, if `method`
4456 // is inherent, there is no `Self` parameter, instead, the impl needs
4457 // type parameters, which we can infer by unifying the provided `Self`
4458 // with the substituted impl type.
4459 let ty = self.tcx.type_of(impl_def_id);
4461 let impl_ty = self.instantiate_type_scheme(span, &substs, &ty);
4462 match self.sub_types(false, &self.misc(span), self_ty, impl_ty) {
4463 Ok(ok) => self.register_infer_ok_obligations(ok),
4466 "instantiate_value_path: (UFCS) {:?} was a subtype of {:?} but now is not?",
4473 debug!("instantiate_value_path: type of {:?} is {:?}",
4476 self.write_substs(node_id, substs);
4480 /// Report errors if the provided parameters are too few or too many.
4481 fn check_path_parameter_count(&self,
4483 segment: &mut Option<(&hir::PathSegment, &ty::Generics)>) {
4484 let (lifetimes, types, infer_types, bindings) = {
4485 match segment.map(|(s, _)| &s.parameters) {
4486 Some(&hir::AngleBracketedParameters(ref data)) => {
4487 (&data.lifetimes[..], &data.types[..], data.infer_types, &data.bindings[..])
4489 Some(&hir::ParenthesizedParameters(_)) => {
4490 AstConv::prohibit_parenthesized_params(self, &segment.as_ref().unwrap().0,
4492 (&[][..], &[][..], true, &[][..])
4494 None => (&[][..], &[][..], true, &[][..])
4498 let count_lifetime_params = |n| {
4499 format!("{} lifetime parameter{}", n, if n == 1 { "" } else { "s" })
4501 let count_type_params = |n| {
4502 format!("{} type parameter{}", n, if n == 1 { "" } else { "s" })
4505 // Check provided lifetime parameters.
4506 let lifetime_defs = segment.map_or(&[][..], |(_, generics)| &generics.regions);
4507 if lifetimes.len() > lifetime_defs.len() {
4508 let expected_text = count_lifetime_params(lifetime_defs.len());
4509 let actual_text = count_lifetime_params(lifetimes.len());
4510 struct_span_err!(self.tcx.sess, span, E0088,
4511 "too many lifetime parameters provided: \
4512 expected at most {}, found {}",
4513 expected_text, actual_text)
4514 .span_label(span, format!("expected {}", expected_text))
4516 } else if lifetimes.len() > 0 && lifetimes.len() < lifetime_defs.len() {
4517 let expected_text = count_lifetime_params(lifetime_defs.len());
4518 let actual_text = count_lifetime_params(lifetimes.len());
4519 struct_span_err!(self.tcx.sess, span, E0090,
4520 "too few lifetime parameters provided: \
4521 expected {}, found {}",
4522 expected_text, actual_text)
4523 .span_label(span, format!("expected {}", expected_text))
4527 // The case where there is not enough lifetime parameters is not checked,
4528 // because this is not possible - a function never takes lifetime parameters.
4529 // See discussion for Pull Request 36208.
4531 // Check provided type parameters.
4532 let type_defs = segment.map_or(&[][..], |(_, generics)| {
4533 if generics.parent.is_none() {
4534 &generics.types[generics.has_self as usize..]
4539 let required_len = type_defs.iter().take_while(|d| !d.has_default).count();
4540 if types.len() > type_defs.len() {
4541 let span = types[type_defs.len()].span;
4542 let expected_text = count_type_params(type_defs.len());
4543 let actual_text = count_type_params(types.len());
4544 struct_span_err!(self.tcx.sess, span, E0087,
4545 "too many type parameters provided: \
4546 expected at most {}, found {}",
4547 expected_text, actual_text)
4548 .span_label(span, format!("expected {}", expected_text))
4551 // To prevent derived errors to accumulate due to extra
4552 // type parameters, we force instantiate_value_path to
4553 // use inference variables instead of the provided types.
4555 } else if !infer_types && types.len() < required_len {
4556 let expected_text = count_type_params(required_len);
4557 let actual_text = count_type_params(types.len());
4558 struct_span_err!(self.tcx.sess, span, E0089,
4559 "too few type parameters provided: \
4560 expected {}, found {}",
4561 expected_text, actual_text)
4562 .span_label(span, format!("expected {}", expected_text))
4566 if !bindings.is_empty() {
4567 span_err!(self.tcx.sess, bindings[0].span, E0182,
4568 "unexpected binding of associated item in expression path \
4569 (only allowed in type paths)");
4573 fn structurally_resolve_type_or_else<F>(&self, sp: Span, ty: Ty<'tcx>, f: F)
4575 where F: Fn() -> Ty<'tcx>
4577 let mut ty = self.resolve_type_vars_with_obligations(ty);
4580 let alternative = f();
4583 if alternative.is_ty_var() || alternative.references_error() {
4584 if !self.is_tainted_by_errors() {
4585 self.type_error_message(sp, |_actual| {
4586 "the type of this value must be known in this context".to_string()
4589 self.demand_suptype(sp, self.tcx.types.err, ty);
4590 ty = self.tcx.types.err;
4592 self.demand_suptype(sp, alternative, ty);
4600 // Resolves `typ` by a single level if `typ` is a type variable. If no
4601 // resolution is possible, then an error is reported.
4602 pub fn structurally_resolved_type(&self, sp: Span, ty: Ty<'tcx>) -> Ty<'tcx> {
4603 self.structurally_resolve_type_or_else(sp, ty, || {
4608 fn with_breakable_ctxt<F: FnOnce() -> R, R>(&self, id: ast::NodeId,
4609 ctxt: BreakableCtxt<'gcx, 'tcx>, f: F)
4610 -> (BreakableCtxt<'gcx, 'tcx>, R) {
4613 let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
4614 index = enclosing_breakables.stack.len();
4615 enclosing_breakables.by_id.insert(id, index);
4616 enclosing_breakables.stack.push(ctxt);
4620 let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
4621 debug_assert!(enclosing_breakables.stack.len() == index + 1);
4622 enclosing_breakables.by_id.remove(&id).expect("missing breakable context");
4623 enclosing_breakables.stack.pop().expect("missing breakable context")
4629 pub fn check_bounds_are_used<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
4630 generics: &hir::Generics,
4632 debug!("check_bounds_are_used(n_tps={}, ty={:?})",
4633 generics.ty_params.len(), ty);
4635 // make a vector of booleans initially false, set to true when used
4636 if generics.ty_params.is_empty() { return; }
4637 let mut tps_used = vec![false; generics.ty_params.len()];
4639 for leaf_ty in ty.walk() {
4640 if let ty::TyParam(ParamTy {idx, ..}) = leaf_ty.sty {
4641 debug!("Found use of ty param num {}", idx);
4642 tps_used[idx as usize - generics.lifetimes.len()] = true;
4646 for (&used, param) in tps_used.iter().zip(&generics.ty_params) {
4648 struct_span_err!(tcx.sess, param.span, E0091,
4649 "type parameter `{}` is unused",
4651 .span_label(param.span, "unused type parameter")