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, Reveal};
97 use rustc::ty::{ParamTy, LvaluePreference, NoPreference, PreferMutLvalue};
98 use rustc::ty::{self, Ty, TyCtxt, Visibility};
99 use rustc::ty::adjustment::{Adjust, Adjustment, AutoBorrow, OverloadedDeref};
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), Reveal::UserFacing),
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_autoderef_adjustment(&self,
1778 node_id: ast::NodeId,
1779 autoderefs: Vec<Option<OverloadedDeref<'tcx>>>,
1780 adjusted_ty: Ty<'tcx>) {
1781 self.apply_adjustment(node_id, Adjustment {
1782 kind: Adjust::DerefRef {
1791 pub fn apply_adjustment(&self, node_id: ast::NodeId, adj: Adjustment<'tcx>) {
1792 debug!("apply_adjustment(node_id={}, adj={:?})", node_id, adj);
1794 if adj.is_identity() {
1798 match self.tables.borrow_mut().adjustments.entry(node_id) {
1799 Entry::Vacant(entry) => { entry.insert(adj); },
1800 Entry::Occupied(mut entry) => {
1801 debug!(" - composing on top of {:?}", entry.get());
1802 match (&entry.get().kind, &adj.kind) {
1803 // Applying any adjustment on top of a NeverToAny
1804 // is a valid NeverToAny adjustment, because it can't
1806 (&Adjust::NeverToAny, _) => return,
1807 (&Adjust::DerefRef {
1808 autoderefs: ref old,
1809 autoref: Some(AutoBorrow::Ref(..)),
1811 }, &Adjust::DerefRef {
1812 autoderefs: ref new, ..
1813 }) if old.len() == 1 && new.len() >= 1 => {
1814 // A reborrow has no effect before a dereference.
1816 // FIXME: currently we never try to compose autoderefs
1817 // and ReifyFnPointer/UnsafeFnPointer, but we could.
1819 bug!("while adjusting {}, can't compose {:?} and {:?}",
1820 node_id, entry.get(), adj)
1822 *entry.get_mut() = adj;
1827 /// Basically whenever we are converting from a type scheme into
1828 /// the fn body space, we always want to normalize associated
1829 /// types as well. This function combines the two.
1830 fn instantiate_type_scheme<T>(&self,
1832 substs: &Substs<'tcx>,
1835 where T : TypeFoldable<'tcx>
1837 let value = value.subst(self.tcx, substs);
1838 let result = self.normalize_associated_types_in(span, &value);
1839 debug!("instantiate_type_scheme(value={:?}, substs={:?}) = {:?}",
1846 /// As `instantiate_type_scheme`, but for the bounds found in a
1847 /// generic type scheme.
1848 fn instantiate_bounds(&self, span: Span, def_id: DefId, substs: &Substs<'tcx>)
1849 -> ty::InstantiatedPredicates<'tcx> {
1850 let bounds = self.tcx.predicates_of(def_id);
1851 let result = bounds.instantiate(self.tcx, substs);
1852 let result = self.normalize_associated_types_in(span, &result);
1853 debug!("instantiate_bounds(bounds={:?}, substs={:?}) = {:?}",
1860 /// Replace all anonymized types with fresh inference variables
1861 /// and record them for writeback.
1862 fn instantiate_anon_types<T: TypeFoldable<'tcx>>(&self, value: &T) -> T {
1863 value.fold_with(&mut BottomUpFolder { tcx: self.tcx, fldop: |ty| {
1864 if let ty::TyAnon(def_id, substs) = ty.sty {
1865 // Use the same type variable if the exact same TyAnon appears more
1866 // than once in the return type (e.g. if it's pased to a type alias).
1867 let id = self.tcx.hir.as_local_node_id(def_id).unwrap();
1868 if let Some(ty_var) = self.anon_types.borrow().get(&id) {
1871 let span = self.tcx.def_span(def_id);
1872 let ty_var = self.next_ty_var(TypeVariableOrigin::TypeInference(span));
1873 self.anon_types.borrow_mut().insert(id, ty_var);
1875 let predicates_of = self.tcx.predicates_of(def_id);
1876 let bounds = predicates_of.instantiate(self.tcx, substs);
1878 for predicate in bounds.predicates {
1879 // Change the predicate to refer to the type variable,
1880 // which will be the concrete type, instead of the TyAnon.
1881 // This also instantiates nested `impl Trait`.
1882 let predicate = self.instantiate_anon_types(&predicate);
1884 // Require that the predicate holds for the concrete type.
1885 let cause = traits::ObligationCause::new(span, self.body_id,
1886 traits::ReturnType);
1887 self.register_predicate(traits::Obligation::new(cause, predicate));
1897 fn normalize_associated_types_in<T>(&self, span: Span, value: &T) -> T
1898 where T : TypeFoldable<'tcx>
1900 let ok = self.normalize_associated_types_in_as_infer_ok(span, value);
1901 self.register_infer_ok_obligations(ok)
1904 fn normalize_associated_types_in_as_infer_ok<T>(&self, span: Span, value: &T)
1906 where T : TypeFoldable<'tcx>
1908 self.inh.normalize_associated_types_in_as_infer_ok(span, self.body_id, value)
1911 pub fn write_nil(&self, node_id: ast::NodeId) {
1912 self.write_ty(node_id, self.tcx.mk_nil());
1915 pub fn write_error(&self, node_id: ast::NodeId) {
1916 self.write_ty(node_id, self.tcx.types.err);
1919 pub fn require_type_meets(&self,
1922 code: traits::ObligationCauseCode<'tcx>,
1925 self.register_bound(
1928 traits::ObligationCause::new(span, self.body_id, code));
1931 pub fn require_type_is_sized(&self,
1934 code: traits::ObligationCauseCode<'tcx>)
1936 let lang_item = self.tcx.require_lang_item(lang_items::SizedTraitLangItem);
1937 self.require_type_meets(ty, span, code, lang_item);
1940 pub fn register_bound(&self,
1943 cause: traits::ObligationCause<'tcx>)
1945 self.fulfillment_cx.borrow_mut()
1946 .register_bound(self, ty, def_id, cause);
1949 pub fn to_ty(&self, ast_t: &hir::Ty) -> Ty<'tcx> {
1950 let t = AstConv::ast_ty_to_ty(self, ast_t);
1951 self.register_wf_obligation(t, ast_t.span, traits::MiscObligation);
1955 pub fn node_ty(&self, id: ast::NodeId) -> Ty<'tcx> {
1956 match self.tables.borrow().node_types.get(&id) {
1958 None if self.err_count_since_creation() != 0 => self.tcx.types.err,
1960 bug!("no type for node {}: {} in fcx {}",
1961 id, self.tcx.hir.node_to_string(id),
1967 /// Registers an obligation for checking later, during regionck, that the type `ty` must
1968 /// outlive the region `r`.
1969 pub fn register_region_obligation(&self,
1971 region: ty::Region<'tcx>,
1972 cause: traits::ObligationCause<'tcx>)
1974 let mut fulfillment_cx = self.fulfillment_cx.borrow_mut();
1975 fulfillment_cx.register_region_obligation(ty, region, cause);
1978 /// Registers an obligation for checking later, during regionck, that the type `ty` must
1979 /// outlive the region `r`.
1980 pub fn register_wf_obligation(&self,
1983 code: traits::ObligationCauseCode<'tcx>)
1985 // WF obligations never themselves fail, so no real need to give a detailed cause:
1986 let cause = traits::ObligationCause::new(span, self.body_id, code);
1987 self.register_predicate(traits::Obligation::new(cause, ty::Predicate::WellFormed(ty)));
1990 pub fn register_old_wf_obligation(&self,
1993 code: traits::ObligationCauseCode<'tcx>)
1995 // Registers an "old-style" WF obligation that uses the
1996 // implicator code. This is basically a buggy version of
1997 // `register_wf_obligation` that is being kept around
1998 // temporarily just to help with phasing in the newer rules.
2000 // FIXME(#27579) all uses of this should be migrated to register_wf_obligation eventually
2001 let cause = traits::ObligationCause::new(span, self.body_id, code);
2002 self.register_region_obligation(ty, self.tcx.types.re_empty, cause);
2005 /// Registers obligations that all types appearing in `substs` are well-formed.
2006 pub fn add_wf_bounds(&self, substs: &Substs<'tcx>, expr: &hir::Expr)
2008 for ty in substs.types() {
2009 self.register_wf_obligation(ty, expr.span, traits::MiscObligation);
2013 /// Given a fully substituted set of bounds (`generic_bounds`), and the values with which each
2014 /// type/region parameter was instantiated (`substs`), creates and registers suitable
2015 /// trait/region obligations.
2017 /// For example, if there is a function:
2020 /// fn foo<'a,T:'a>(...)
2023 /// and a reference:
2029 /// Then we will create a fresh region variable `'$0` and a fresh type variable `$1` for `'a`
2030 /// and `T`. This routine will add a region obligation `$1:'$0` and register it locally.
2031 pub fn add_obligations_for_parameters(&self,
2032 cause: traits::ObligationCause<'tcx>,
2033 predicates: &ty::InstantiatedPredicates<'tcx>)
2035 assert!(!predicates.has_escaping_regions());
2037 debug!("add_obligations_for_parameters(predicates={:?})",
2040 for obligation in traits::predicates_for_generics(cause, predicates) {
2041 self.register_predicate(obligation);
2045 // FIXME(arielb1): use this instead of field.ty everywhere
2046 // Only for fields! Returns <none> for methods>
2047 // Indifferent to privacy flags
2048 pub fn field_ty(&self,
2050 field: &'tcx ty::FieldDef,
2051 substs: &Substs<'tcx>)
2054 self.normalize_associated_types_in(span,
2055 &field.ty(self.tcx, substs))
2058 fn check_casts(&self) {
2059 let mut deferred_cast_checks = self.deferred_cast_checks.borrow_mut();
2060 for cast in deferred_cast_checks.drain(..) {
2065 /// Apply "fallbacks" to some types
2066 /// unconstrained types get replaced with ! or () (depending on whether
2067 /// feature(never_type) is enabled), unconstrained ints with i32, and
2068 /// unconstrained floats with f64.
2069 fn default_type_parameters(&self) {
2070 use rustc::ty::error::UnconstrainedNumeric::Neither;
2071 use rustc::ty::error::UnconstrainedNumeric::{UnconstrainedInt, UnconstrainedFloat};
2073 // Defaulting inference variables becomes very dubious if we have
2074 // encountered type-checking errors. Therefore, if we think we saw
2075 // some errors in this function, just resolve all uninstanted type
2076 // varibles to TyError.
2077 if self.is_tainted_by_errors() {
2078 for ty in &self.unsolved_variables() {
2079 if let ty::TyInfer(_) = self.shallow_resolve(ty).sty {
2080 debug!("default_type_parameters: defaulting `{:?}` to error", ty);
2081 self.demand_eqtype(syntax_pos::DUMMY_SP, *ty, self.tcx().types.err);
2087 for ty in &self.unsolved_variables() {
2088 let resolved = self.resolve_type_vars_if_possible(ty);
2089 if self.type_var_diverges(resolved) {
2090 debug!("default_type_parameters: defaulting `{:?}` to `!` because it diverges",
2092 self.demand_eqtype(syntax_pos::DUMMY_SP, *ty,
2093 self.tcx.mk_diverging_default());
2095 match self.type_is_unconstrained_numeric(resolved) {
2096 UnconstrainedInt => {
2097 debug!("default_type_parameters: defaulting `{:?}` to `i32`",
2099 self.demand_eqtype(syntax_pos::DUMMY_SP, *ty, self.tcx.types.i32)
2101 UnconstrainedFloat => {
2102 debug!("default_type_parameters: defaulting `{:?}` to `f32`",
2104 self.demand_eqtype(syntax_pos::DUMMY_SP, *ty, self.tcx.types.f64)
2112 // Implements type inference fallback algorithm
2113 fn select_all_obligations_and_apply_defaults(&self) {
2114 self.select_obligations_where_possible();
2115 self.default_type_parameters();
2116 self.select_obligations_where_possible();
2119 fn select_all_obligations_or_error(&self) {
2120 debug!("select_all_obligations_or_error");
2122 // upvar inference should have ensured that all deferred call
2123 // resolutions are handled by now.
2124 assert!(self.deferred_call_resolutions.borrow().is_empty());
2126 self.select_all_obligations_and_apply_defaults();
2128 let mut fulfillment_cx = self.fulfillment_cx.borrow_mut();
2130 match fulfillment_cx.select_all_or_error(self) {
2132 Err(errors) => { self.report_fulfillment_errors(&errors); }
2136 /// Select as many obligations as we can at present.
2137 fn select_obligations_where_possible(&self) {
2138 match self.fulfillment_cx.borrow_mut().select_where_possible(self) {
2140 Err(errors) => { self.report_fulfillment_errors(&errors); }
2144 /// For the overloaded lvalue expressions (`*x`, `x[3]`), the trait
2145 /// returns a type of `&T`, but the actual type we assign to the
2146 /// *expression* is `T`. So this function just peels off the return
2147 /// type by one layer to yield `T`.
2148 fn make_overloaded_lvalue_return_type(&self,
2149 method: MethodCallee<'tcx>)
2150 -> ty::TypeAndMut<'tcx>
2152 // extract method return type, which will be &T;
2153 // all LB regions should have been instantiated during method lookup
2154 let ret_ty = method.sig.output();
2156 // method returns &T, but the type as visible to user is T, so deref
2157 ret_ty.builtin_deref(true, NoPreference).unwrap()
2160 fn lookup_indexing(&self,
2162 base_expr: &'gcx hir::Expr,
2165 lvalue_pref: LvaluePreference)
2166 -> Option<(/*index type*/ Ty<'tcx>, /*element type*/ Ty<'tcx>)>
2168 // FIXME(#18741) -- this is almost but not quite the same as the
2169 // autoderef that normal method probing does. They could likely be
2172 let mut autoderef = self.autoderef(base_expr.span, base_ty);
2173 let mut result = None;
2174 while result.is_none() && autoderef.next().is_some() {
2175 result = self.try_index_step(expr, base_expr, &autoderef, lvalue_pref, idx_ty);
2177 autoderef.finalize();
2181 /// To type-check `base_expr[index_expr]`, we progressively autoderef
2182 /// (and otherwise adjust) `base_expr`, looking for a type which either
2183 /// supports builtin indexing or overloaded indexing.
2184 /// This loop implements one step in that search; the autoderef loop
2185 /// is implemented by `lookup_indexing`.
2186 fn try_index_step(&self,
2188 base_expr: &hir::Expr,
2189 autoderef: &Autoderef<'a, 'gcx, 'tcx>,
2190 lvalue_pref: LvaluePreference,
2192 -> Option<(/*index type*/ Ty<'tcx>, /*element type*/ Ty<'tcx>)>
2194 let mut adjusted_ty = autoderef.unambiguous_final_ty();
2195 debug!("try_index_step(expr={:?}, base_expr={:?}, adjusted_ty={:?}, \
2203 // First, try built-in indexing.
2204 match (adjusted_ty.builtin_index(), &index_ty.sty) {
2205 (Some(ty), &ty::TyUint(ast::UintTy::Us)) | (Some(ty), &ty::TyInfer(ty::IntVar(_))) => {
2206 debug!("try_index_step: success, using built-in indexing");
2207 let autoderefs = autoderef.adjust_steps(lvalue_pref);
2208 self.apply_autoderef_adjustment(
2209 base_expr.id, autoderefs, adjusted_ty);
2210 return Some((self.tcx.types.usize, ty));
2215 for &unsize in &[false, true] {
2217 // We only unsize arrays here.
2218 if let ty::TyArray(element_ty, _) = adjusted_ty.sty {
2219 adjusted_ty = self.tcx.mk_slice(element_ty);
2225 // If some lookup succeeds, write callee into table and extract index/element
2226 // type from the method signature.
2227 // If some lookup succeeded, install method in table
2228 let input_ty = self.next_ty_var(TypeVariableOrigin::AutoDeref(base_expr.span));
2229 let method = self.try_overloaded_lvalue_op(
2230 expr.span, adjusted_ty, &[input_ty], lvalue_pref, LvalueOp::Index);
2232 let result = method.map(|ok| {
2233 debug!("try_index_step: success, using overloaded indexing");
2234 let (autoref, method) = self.register_infer_ok_obligations(ok);
2236 let autoderefs = autoderef.adjust_steps(lvalue_pref);
2237 self.apply_adjustment(base_expr.id, Adjustment {
2238 kind: Adjust::DerefRef {
2243 target: method.sig.inputs()[0]
2246 self.write_method_call(expr.id, method);
2247 (input_ty, self.make_overloaded_lvalue_return_type(method).ty)
2249 if result.is_some() {
2257 fn resolve_lvalue_op(&self, op: LvalueOp, is_mut: bool) -> (Option<DefId>, Symbol) {
2258 let (tr, name) = match (op, is_mut) {
2259 (LvalueOp::Deref, false) =>
2260 (self.tcx.lang_items.deref_trait(), "deref"),
2261 (LvalueOp::Deref, true) =>
2262 (self.tcx.lang_items.deref_mut_trait(), "deref_mut"),
2263 (LvalueOp::Index, false) =>
2264 (self.tcx.lang_items.index_trait(), "index"),
2265 (LvalueOp::Index, true) =>
2266 (self.tcx.lang_items.index_mut_trait(), "index_mut"),
2268 (tr, Symbol::intern(name))
2271 fn try_overloaded_lvalue_op(&self,
2274 arg_tys: &[Ty<'tcx>],
2275 lvalue_pref: LvaluePreference,
2277 -> Option<InferOk<'tcx,
2278 (Option<AutoBorrow<'tcx>>,
2279 MethodCallee<'tcx>)>>
2281 debug!("try_overloaded_lvalue_op({:?},{:?},{:?},{:?})",
2287 // Try Mut first, if preferred.
2288 let (mut_tr, mut_op) = self.resolve_lvalue_op(op, true);
2289 let method = match (lvalue_pref, mut_tr) {
2290 (PreferMutLvalue, Some(trait_did)) => {
2291 self.lookup_method_in_trait_adjusted(span,
2300 // Otherwise, fall back to the immutable version.
2301 let (imm_tr, imm_op) = self.resolve_lvalue_op(op, false);
2302 let method = match (method, imm_tr) {
2303 (None, Some(trait_did)) => {
2304 self.lookup_method_in_trait_adjusted(span,
2310 (method, _) => method,
2316 fn check_method_argument_types(&self,
2318 method: Result<MethodCallee<'tcx>, ()>,
2319 args_no_rcvr: &'gcx [hir::Expr],
2320 tuple_arguments: TupleArgumentsFlag,
2321 expected: Expectation<'tcx>)
2323 let has_error = match method {
2325 method.substs.references_error() || method.sig.references_error()
2330 let err_inputs = self.err_args(args_no_rcvr.len());
2332 let err_inputs = match tuple_arguments {
2333 DontTupleArguments => err_inputs,
2334 TupleArguments => vec![self.tcx.intern_tup(&err_inputs[..], false)],
2337 self.check_argument_types(sp, &err_inputs[..], &[], args_no_rcvr,
2338 false, tuple_arguments, None);
2339 return self.tcx.types.err;
2342 let method = method.unwrap();
2343 // HACK(eddyb) ignore self in the definition (see above).
2344 let expected_arg_tys = self.expected_inputs_for_expected_output(
2347 method.sig.output(),
2348 &method.sig.inputs()[1..]
2350 self.check_argument_types(sp, &method.sig.inputs()[1..], &expected_arg_tys[..],
2351 args_no_rcvr, method.sig.variadic, tuple_arguments,
2352 self.tcx.hir.span_if_local(method.def_id));
2356 /// Generic function that factors out common logic from function calls,
2357 /// method calls and overloaded operators.
2358 fn check_argument_types(&self,
2360 fn_inputs: &[Ty<'tcx>],
2361 expected_arg_tys: &[Ty<'tcx>],
2362 args: &'gcx [hir::Expr],
2364 tuple_arguments: TupleArgumentsFlag,
2365 def_span: Option<Span>) {
2368 // Grab the argument types, supplying fresh type variables
2369 // if the wrong number of arguments were supplied
2370 let supplied_arg_count = if tuple_arguments == DontTupleArguments {
2376 // All the input types from the fn signature must outlive the call
2377 // so as to validate implied bounds.
2378 for &fn_input_ty in fn_inputs {
2379 self.register_wf_obligation(fn_input_ty, sp, traits::MiscObligation);
2382 let mut expected_arg_tys = expected_arg_tys;
2383 let expected_arg_count = fn_inputs.len();
2385 let sp_args = if args.len() > 0 {
2386 let (first, args) = args.split_at(1);
2387 let mut sp_tmp = first[0].span;
2389 let sp_opt = self.sess().codemap().merge_spans(sp_tmp, arg.span);
2390 if ! sp_opt.is_some() {
2393 sp_tmp = sp_opt.unwrap();
2400 fn parameter_count_error<'tcx>(sess: &Session, sp: Span, expected_count: usize,
2401 arg_count: usize, error_code: &str, variadic: bool,
2402 def_span: Option<Span>) {
2403 let mut err = sess.struct_span_err_with_code(sp,
2404 &format!("this function takes {}{} parameter{} but {} parameter{} supplied",
2405 if variadic {"at least "} else {""},
2407 if expected_count == 1 {""} else {"s"},
2409 if arg_count == 1 {" was"} else {"s were"}),
2412 err.span_label(sp, format!("expected {}{} parameter{}",
2413 if variadic {"at least "} else {""},
2415 if expected_count == 1 {""} else {"s"}));
2416 if let Some(def_s) = def_span {
2417 err.span_label(def_s, "defined here");
2422 let formal_tys = if tuple_arguments == TupleArguments {
2423 let tuple_type = self.structurally_resolved_type(sp, fn_inputs[0]);
2424 match tuple_type.sty {
2425 ty::TyTuple(arg_types, _) if arg_types.len() != args.len() => {
2426 parameter_count_error(tcx.sess, sp_args, arg_types.len(), args.len(),
2427 "E0057", false, def_span);
2428 expected_arg_tys = &[];
2429 self.err_args(args.len())
2431 ty::TyTuple(arg_types, _) => {
2432 expected_arg_tys = match expected_arg_tys.get(0) {
2433 Some(&ty) => match ty.sty {
2434 ty::TyTuple(ref tys, _) => &tys,
2442 span_err!(tcx.sess, sp, E0059,
2443 "cannot use call notation; the first type parameter \
2444 for the function trait is neither a tuple nor unit");
2445 expected_arg_tys = &[];
2446 self.err_args(args.len())
2449 } else if expected_arg_count == supplied_arg_count {
2451 } else if variadic {
2452 if supplied_arg_count >= expected_arg_count {
2455 parameter_count_error(tcx.sess, sp_args, expected_arg_count,
2456 supplied_arg_count, "E0060", true, def_span);
2457 expected_arg_tys = &[];
2458 self.err_args(supplied_arg_count)
2461 parameter_count_error(tcx.sess, sp_args, expected_arg_count,
2462 supplied_arg_count, "E0061", false, def_span);
2463 expected_arg_tys = &[];
2464 self.err_args(supplied_arg_count)
2467 debug!("check_argument_types: formal_tys={:?}",
2468 formal_tys.iter().map(|t| self.ty_to_string(*t)).collect::<Vec<String>>());
2470 // Check the arguments.
2471 // We do this in a pretty awful way: first we typecheck any arguments
2472 // that are not closures, then we typecheck the closures. This is so
2473 // that we have more information about the types of arguments when we
2474 // typecheck the functions. This isn't really the right way to do this.
2475 for &check_closures in &[false, true] {
2476 debug!("check_closures={}", check_closures);
2478 // More awful hacks: before we check argument types, try to do
2479 // an "opportunistic" vtable resolution of any trait bounds on
2480 // the call. This helps coercions.
2482 self.select_obligations_where_possible();
2485 // For variadic functions, we don't have a declared type for all of
2486 // the arguments hence we only do our usual type checking with
2487 // the arguments who's types we do know.
2488 let t = if variadic {
2490 } else if tuple_arguments == TupleArguments {
2495 for (i, arg) in args.iter().take(t).enumerate() {
2496 // Warn only for the first loop (the "no closures" one).
2497 // Closure arguments themselves can't be diverging, but
2498 // a previous argument can, e.g. `foo(panic!(), || {})`.
2499 if !check_closures {
2500 self.warn_if_unreachable(arg.id, arg.span, "expression");
2503 let is_closure = match arg.node {
2504 hir::ExprClosure(..) => true,
2508 if is_closure != check_closures {
2512 debug!("checking the argument");
2513 let formal_ty = formal_tys[i];
2515 // The special-cased logic below has three functions:
2516 // 1. Provide as good of an expected type as possible.
2517 let expected = expected_arg_tys.get(i).map(|&ty| {
2518 Expectation::rvalue_hint(self, ty)
2521 let checked_ty = self.check_expr_with_expectation(
2523 expected.unwrap_or(ExpectHasType(formal_ty)));
2525 // 2. Coerce to the most detailed type that could be coerced
2526 // to, which is `expected_ty` if `rvalue_hint` returns an
2527 // `ExpectHasType(expected_ty)`, or the `formal_ty` otherwise.
2528 let coerce_ty = expected.and_then(|e| e.only_has_type(self));
2529 self.demand_coerce(&arg, checked_ty, coerce_ty.unwrap_or(formal_ty));
2531 // 3. Relate the expected type and the formal one,
2532 // if the expected type was used for the coercion.
2533 coerce_ty.map(|ty| self.demand_suptype(arg.span, formal_ty, ty));
2537 // We also need to make sure we at least write the ty of the other
2538 // arguments which we skipped above.
2540 for arg in args.iter().skip(expected_arg_count) {
2541 let arg_ty = self.check_expr(&arg);
2543 // There are a few types which get autopromoted when passed via varargs
2544 // in C but we just error out instead and require explicit casts.
2545 let arg_ty = self.structurally_resolved_type(arg.span,
2548 ty::TyFloat(ast::FloatTy::F32) => {
2549 self.type_error_message(arg.span, |t| {
2550 format!("can't pass an `{}` to variadic \
2551 function, cast to `c_double`", t)
2554 ty::TyInt(ast::IntTy::I8) | ty::TyInt(ast::IntTy::I16) | ty::TyBool => {
2555 self.type_error_message(arg.span, |t| {
2556 format!("can't pass `{}` to variadic \
2557 function, cast to `c_int`",
2561 ty::TyUint(ast::UintTy::U8) | ty::TyUint(ast::UintTy::U16) => {
2562 self.type_error_message(arg.span, |t| {
2563 format!("can't pass `{}` to variadic \
2564 function, cast to `c_uint`",
2568 ty::TyFnDef(.., f) => {
2569 let ptr_ty = self.tcx.mk_fn_ptr(f);
2570 let ptr_ty = self.resolve_type_vars_if_possible(&ptr_ty);
2571 self.type_error_message(arg.span,
2573 format!("can't pass `{}` to variadic \
2574 function, cast to `{}`", t, ptr_ty)
2583 fn err_args(&self, len: usize) -> Vec<Ty<'tcx>> {
2584 (0..len).map(|_| self.tcx.types.err).collect()
2587 // AST fragment checking
2590 expected: Expectation<'tcx>)
2596 ast::LitKind::Str(..) => tcx.mk_static_str(),
2597 ast::LitKind::ByteStr(ref v) => {
2598 tcx.mk_imm_ref(tcx.types.re_static,
2599 tcx.mk_array(tcx.types.u8, v.len()))
2601 ast::LitKind::Byte(_) => tcx.types.u8,
2602 ast::LitKind::Char(_) => tcx.types.char,
2603 ast::LitKind::Int(_, ast::LitIntType::Signed(t)) => tcx.mk_mach_int(t),
2604 ast::LitKind::Int(_, ast::LitIntType::Unsigned(t)) => tcx.mk_mach_uint(t),
2605 ast::LitKind::Int(_, ast::LitIntType::Unsuffixed) => {
2606 let opt_ty = expected.to_option(self).and_then(|ty| {
2608 ty::TyInt(_) | ty::TyUint(_) => Some(ty),
2609 ty::TyChar => Some(tcx.types.u8),
2610 ty::TyRawPtr(..) => Some(tcx.types.usize),
2611 ty::TyFnDef(..) | ty::TyFnPtr(_) => Some(tcx.types.usize),
2615 opt_ty.unwrap_or_else(
2616 || tcx.mk_int_var(self.next_int_var_id()))
2618 ast::LitKind::Float(_, t) => tcx.mk_mach_float(t),
2619 ast::LitKind::FloatUnsuffixed(_) => {
2620 let opt_ty = expected.to_option(self).and_then(|ty| {
2622 ty::TyFloat(_) => Some(ty),
2626 opt_ty.unwrap_or_else(
2627 || tcx.mk_float_var(self.next_float_var_id()))
2629 ast::LitKind::Bool(_) => tcx.types.bool
2633 fn check_expr_eq_type(&self,
2634 expr: &'gcx hir::Expr,
2635 expected: Ty<'tcx>) {
2636 let ty = self.check_expr_with_hint(expr, expected);
2637 self.demand_eqtype(expr.span, expected, ty);
2640 pub fn check_expr_has_type(&self,
2641 expr: &'gcx hir::Expr,
2642 expected: Ty<'tcx>) -> Ty<'tcx> {
2643 let mut ty = self.check_expr_with_hint(expr, expected);
2645 // While we don't allow *arbitrary* coercions here, we *do* allow
2646 // coercions from ! to `expected`.
2648 assert!(!self.tables.borrow().adjustments.contains_key(&expr.id),
2649 "expression with never type wound up being adjusted");
2650 let adj_ty = self.next_diverging_ty_var(
2651 TypeVariableOrigin::AdjustmentType(expr.span));
2652 self.apply_adjustment(expr.id, Adjustment {
2653 kind: Adjust::NeverToAny,
2659 self.demand_suptype(expr.span, expected, ty);
2663 fn check_expr_coercable_to_type(&self,
2664 expr: &'gcx hir::Expr,
2665 expected: Ty<'tcx>) -> Ty<'tcx> {
2666 let ty = self.check_expr_with_hint(expr, expected);
2667 self.demand_coerce(expr, ty, expected);
2671 fn check_expr_with_hint(&self, expr: &'gcx hir::Expr,
2672 expected: Ty<'tcx>) -> Ty<'tcx> {
2673 self.check_expr_with_expectation(expr, ExpectHasType(expected))
2676 fn check_expr_with_expectation(&self,
2677 expr: &'gcx hir::Expr,
2678 expected: Expectation<'tcx>) -> Ty<'tcx> {
2679 self.check_expr_with_expectation_and_lvalue_pref(expr, expected, NoPreference)
2682 fn check_expr(&self, expr: &'gcx hir::Expr) -> Ty<'tcx> {
2683 self.check_expr_with_expectation(expr, NoExpectation)
2686 fn check_expr_with_lvalue_pref(&self, expr: &'gcx hir::Expr,
2687 lvalue_pref: LvaluePreference) -> Ty<'tcx> {
2688 self.check_expr_with_expectation_and_lvalue_pref(expr, NoExpectation, lvalue_pref)
2691 // determine the `self` type, using fresh variables for all variables
2692 // declared on the impl declaration e.g., `impl<A,B> for Vec<(A,B)>`
2693 // would return ($0, $1) where $0 and $1 are freshly instantiated type
2695 pub fn impl_self_ty(&self,
2696 span: Span, // (potential) receiver for this impl
2698 -> TypeAndSubsts<'tcx> {
2699 let ity = self.tcx.type_of(did);
2700 debug!("impl_self_ty: ity={:?}", ity);
2702 let substs = self.fresh_substs_for_item(span, did);
2703 let substd_ty = self.instantiate_type_scheme(span, &substs, &ity);
2705 TypeAndSubsts { substs: substs, ty: substd_ty }
2708 /// Unifies the output type with the expected type early, for more coercions
2709 /// and forward type information on the input expressions.
2710 fn expected_inputs_for_expected_output(&self,
2712 expected_ret: Expectation<'tcx>,
2713 formal_ret: Ty<'tcx>,
2714 formal_args: &[Ty<'tcx>])
2716 let expected_args = expected_ret.only_has_type(self).and_then(|ret_ty| {
2717 self.fudge_regions_if_ok(&RegionVariableOrigin::Coercion(call_span), || {
2718 // Attempt to apply a subtyping relationship between the formal
2719 // return type (likely containing type variables if the function
2720 // is polymorphic) and the expected return type.
2721 // No argument expectations are produced if unification fails.
2722 let origin = self.misc(call_span);
2723 let ures = self.sub_types(false, &origin, formal_ret, ret_ty);
2725 // FIXME(#15760) can't use try! here, FromError doesn't default
2726 // to identity so the resulting type is not constrained.
2729 // Process any obligations locally as much as
2730 // we can. We don't care if some things turn
2731 // out unconstrained or ambiguous, as we're
2732 // just trying to get hints here.
2733 let result = self.save_and_restore_in_snapshot_flag(|_| {
2734 let mut fulfill = FulfillmentContext::new();
2735 let ok = ok; // FIXME(#30046)
2736 for obligation in ok.obligations {
2737 fulfill.register_predicate_obligation(self, obligation);
2739 fulfill.select_where_possible(self)
2744 Err(_) => return Err(()),
2747 Err(_) => return Err(()),
2750 // Record all the argument types, with the substitutions
2751 // produced from the above subtyping unification.
2752 Ok(formal_args.iter().map(|ty| {
2753 self.resolve_type_vars_if_possible(ty)
2756 }).unwrap_or(vec![]);
2757 debug!("expected_inputs_for_expected_output(formal={:?} -> {:?}, expected={:?} -> {:?})",
2758 formal_args, formal_ret,
2759 expected_args, expected_ret);
2763 // Checks a method call.
2764 fn check_method_call(&self,
2765 expr: &'gcx hir::Expr,
2766 method_name: Spanned<ast::Name>,
2767 args: &'gcx [hir::Expr],
2769 expected: Expectation<'tcx>,
2770 lvalue_pref: LvaluePreference) -> Ty<'tcx> {
2771 let rcvr = &args[0];
2772 let rcvr_t = self.check_expr_with_lvalue_pref(&rcvr, lvalue_pref);
2774 // no need to check for bot/err -- callee does that
2775 let expr_t = self.structurally_resolved_type(expr.span, rcvr_t);
2777 let tps = tps.iter().map(|ast_ty| self.to_ty(&ast_ty)).collect::<Vec<_>>();
2778 let method = match self.lookup_method(method_name.span,
2785 self.write_method_call(expr.id, method);
2789 if method_name.node != keywords::Invalid.name() {
2790 self.report_method_error(method_name.span,
2801 // Call the generic checker.
2802 self.check_method_argument_types(method_name.span, method,
2808 fn check_return_expr(&self, return_expr: &'gcx hir::Expr) {
2812 .unwrap_or_else(|| span_bug!(return_expr.span,
2813 "check_return_expr called outside fn body"));
2815 let ret_ty = ret_coercion.borrow().expected_ty();
2816 let return_expr_ty = self.check_expr_with_hint(return_expr, ret_ty);
2817 ret_coercion.borrow_mut()
2819 &self.misc(return_expr.span),
2822 self.diverges.get());
2826 // A generic function for checking the then and else in an if
2828 fn check_then_else(&self,
2829 cond_expr: &'gcx hir::Expr,
2830 then_expr: &'gcx hir::Expr,
2831 opt_else_expr: Option<&'gcx hir::Expr>,
2833 expected: Expectation<'tcx>) -> Ty<'tcx> {
2834 let cond_ty = self.check_expr_has_type(cond_expr, self.tcx.types.bool);
2835 let cond_diverges = self.diverges.get();
2836 self.diverges.set(Diverges::Maybe);
2838 let expected = expected.adjust_for_branches(self);
2839 let then_ty = self.check_expr_with_expectation(then_expr, expected);
2840 let then_diverges = self.diverges.get();
2841 self.diverges.set(Diverges::Maybe);
2843 // We've already taken the expected type's preferences
2844 // into account when typing the `then` branch. To figure
2845 // out the initial shot at a LUB, we thus only consider
2846 // `expected` if it represents a *hard* constraint
2847 // (`only_has_type`); otherwise, we just go with a
2848 // fresh type variable.
2849 let coerce_to_ty = expected.coercion_target_type(self, sp);
2850 let mut coerce: DynamicCoerceMany = CoerceMany::new(coerce_to_ty);
2852 let if_cause = self.cause(sp, ObligationCauseCode::IfExpression);
2853 coerce.coerce(self, &if_cause, then_expr, then_ty, then_diverges);
2855 if let Some(else_expr) = opt_else_expr {
2856 let else_ty = self.check_expr_with_expectation(else_expr, expected);
2857 let else_diverges = self.diverges.get();
2859 coerce.coerce(self, &if_cause, else_expr, else_ty, else_diverges);
2861 // We won't diverge unless both branches do (or the condition does).
2862 self.diverges.set(cond_diverges | then_diverges & else_diverges);
2864 let else_cause = self.cause(sp, ObligationCauseCode::IfExpressionWithNoElse);
2865 coerce.coerce_forced_unit(self, &else_cause, &mut |_| (), true);
2867 // If the condition is false we can't diverge.
2868 self.diverges.set(cond_diverges);
2871 let result_ty = coerce.complete(self);
2872 if cond_ty.references_error() {
2879 // Check field access expressions
2880 fn check_field(&self,
2881 expr: &'gcx hir::Expr,
2882 lvalue_pref: LvaluePreference,
2883 base: &'gcx hir::Expr,
2884 field: &Spanned<ast::Name>) -> Ty<'tcx> {
2885 let expr_t = self.check_expr_with_lvalue_pref(base, lvalue_pref);
2886 let expr_t = self.structurally_resolved_type(expr.span,
2888 let mut private_candidate = None;
2889 let mut autoderef = self.autoderef(expr.span, expr_t);
2890 while let Some((base_t, _)) = autoderef.next() {
2892 ty::TyAdt(base_def, substs) if !base_def.is_enum() => {
2893 debug!("struct named {:?}", base_t);
2894 let (ident, def_scope) =
2895 self.tcx.adjust(field.node, base_def.did, self.body_id);
2896 let fields = &base_def.struct_variant().fields;
2897 if let Some(field) = fields.iter().find(|f| f.name.to_ident() == ident) {
2898 let field_ty = self.field_ty(expr.span, field, substs);
2899 if field.vis.is_accessible_from(def_scope, self.tcx) {
2900 let autoderefs = autoderef.adjust_steps(lvalue_pref);
2901 self.apply_autoderef_adjustment(base.id, autoderefs, base_t);
2902 autoderef.finalize();
2904 self.tcx.check_stability(field.did, expr.id, expr.span);
2908 private_candidate = Some((base_def.did, field_ty));
2914 autoderef.unambiguous_final_ty();
2916 if let Some((did, field_ty)) = private_candidate {
2917 let struct_path = self.tcx().item_path_str(did);
2918 let msg = format!("field `{}` of struct `{}` is private", field.node, struct_path);
2919 let mut err = self.tcx().sess.struct_span_err(expr.span, &msg);
2920 // Also check if an accessible method exists, which is often what is meant.
2921 if self.method_exists(field.span, field.node, expr_t, expr.id, false) {
2922 err.note(&format!("a method `{}` also exists, perhaps you wish to call it",
2927 } else if field.node == keywords::Invalid.name() {
2928 self.tcx().types.err
2929 } else if self.method_exists(field.span, field.node, expr_t, expr.id, true) {
2930 self.type_error_struct(field.span, |actual| {
2931 format!("attempted to take value of method `{}` on type \
2932 `{}`", field.node, actual)
2934 .help("maybe a `()` to call it is missing? \
2935 If not, try an anonymous function")
2937 self.tcx().types.err
2939 let mut err = self.type_error_struct(field.span, |actual| {
2940 format!("no field `{}` on type `{}`",
2944 ty::TyAdt(def, _) if !def.is_enum() => {
2945 if let Some(suggested_field_name) =
2946 Self::suggest_field_name(def.struct_variant(), field, vec![]) {
2947 err.span_label(field.span,
2948 format!("did you mean `{}`?", suggested_field_name));
2950 err.span_label(field.span,
2954 ty::TyRawPtr(..) => {
2955 err.note(&format!("`{0}` is a native pointer; perhaps you need to deref with \
2957 self.tcx.hir.node_to_pretty_string(base.id),
2963 self.tcx().types.err
2967 // Return an hint about the closest match in field names
2968 fn suggest_field_name(variant: &'tcx ty::VariantDef,
2969 field: &Spanned<ast::Name>,
2970 skip : Vec<InternedString>)
2972 let name = field.node.as_str();
2973 let names = variant.fields.iter().filter_map(|field| {
2974 // ignore already set fields and private fields from non-local crates
2975 if skip.iter().any(|x| *x == field.name.as_str()) ||
2976 (variant.did.krate != LOCAL_CRATE && field.vis != Visibility::Public) {
2983 // only find fits with at least one matching letter
2984 find_best_match_for_name(names, &name, Some(name.len()))
2987 // Check tuple index expressions
2988 fn check_tup_field(&self,
2989 expr: &'gcx hir::Expr,
2990 lvalue_pref: LvaluePreference,
2991 base: &'gcx hir::Expr,
2992 idx: codemap::Spanned<usize>) -> Ty<'tcx> {
2993 let expr_t = self.check_expr_with_lvalue_pref(base, lvalue_pref);
2994 let expr_t = self.structurally_resolved_type(expr.span,
2996 let mut private_candidate = None;
2997 let mut tuple_like = false;
2998 let mut autoderef = self.autoderef(expr.span, expr_t);
2999 while let Some((base_t, _)) = autoderef.next() {
3000 let field = match base_t.sty {
3001 ty::TyAdt(base_def, substs) if base_def.is_struct() => {
3002 tuple_like = base_def.struct_variant().ctor_kind == CtorKind::Fn;
3003 if !tuple_like { continue }
3005 debug!("tuple struct named {:?}", base_t);
3006 let ident = ast::Ident {
3007 name: Symbol::intern(&idx.node.to_string()),
3008 ctxt: idx.span.ctxt.modern(),
3010 let (ident, def_scope) =
3011 self.tcx.adjust_ident(ident, base_def.did, self.body_id);
3012 let fields = &base_def.struct_variant().fields;
3013 if let Some(field) = fields.iter().find(|f| f.name.to_ident() == ident) {
3014 let field_ty = self.field_ty(expr.span, field, substs);
3015 if field.vis.is_accessible_from(def_scope, self.tcx) {
3016 self.tcx.check_stability(field.did, expr.id, expr.span);
3019 private_candidate = Some((base_def.did, field_ty));
3026 ty::TyTuple(ref v, _) => {
3028 v.get(idx.node).cloned()
3033 if let Some(field_ty) = field {
3034 let autoderefs = autoderef.adjust_steps(lvalue_pref);
3035 self.apply_autoderef_adjustment(base.id, autoderefs, base_t);
3036 autoderef.finalize();
3040 autoderef.unambiguous_final_ty();
3042 if let Some((did, field_ty)) = private_candidate {
3043 let struct_path = self.tcx().item_path_str(did);
3044 let msg = format!("field `{}` of struct `{}` is private", idx.node, struct_path);
3045 self.tcx().sess.span_err(expr.span, &msg);
3049 self.type_error_message(
3053 format!("attempted out-of-bounds tuple index `{}` on \
3058 format!("attempted tuple index `{}` on type `{}`, but the \
3059 type was not a tuple or tuple struct",
3066 self.tcx().types.err
3069 fn report_unknown_field(&self,
3071 variant: &'tcx ty::VariantDef,
3073 skip_fields: &[hir::Field],
3075 let mut err = self.type_error_struct_with_diag(
3077 |actual| match ty.sty {
3078 ty::TyAdt(adt, ..) if adt.is_enum() => {
3079 struct_span_err!(self.tcx.sess, field.name.span, E0559,
3080 "{} `{}::{}` has no field named `{}`",
3081 kind_name, actual, variant.name, field.name.node)
3084 struct_span_err!(self.tcx.sess, field.name.span, E0560,
3085 "{} `{}` has no field named `{}`",
3086 kind_name, actual, field.name.node)
3090 // prevent all specified fields from being suggested
3091 let skip_fields = skip_fields.iter().map(|ref x| x.name.node.as_str());
3092 if let Some(field_name) = Self::suggest_field_name(variant,
3094 skip_fields.collect()) {
3095 err.span_label(field.name.span,
3096 format!("field does not exist - did you mean `{}`?", field_name));
3099 ty::TyAdt(adt, ..) if adt.is_enum() => {
3100 err.span_label(field.name.span, format!("`{}::{}` does not have this field",
3104 err.span_label(field.name.span, format!("`{}` does not have this field", ty));
3111 fn check_expr_struct_fields(&self,
3113 expected: Expectation<'tcx>,
3114 expr_id: ast::NodeId,
3116 variant: &'tcx ty::VariantDef,
3117 ast_fields: &'gcx [hir::Field],
3118 check_completeness: bool) {
3122 self.expected_inputs_for_expected_output(span, expected, adt_ty, &[adt_ty])
3123 .get(0).cloned().unwrap_or(adt_ty);
3125 let (substs, hint_substs, adt_kind, kind_name) = match (&adt_ty.sty, &adt_ty_hint.sty) {
3126 (&ty::TyAdt(adt, substs), &ty::TyAdt(_, hint_substs)) => {
3127 (substs, hint_substs, adt.adt_kind(), adt.variant_descr())
3129 _ => span_bug!(span, "non-ADT passed to check_expr_struct_fields")
3132 let mut remaining_fields = FxHashMap();
3133 for field in &variant.fields {
3134 remaining_fields.insert(field.name.to_ident(), field);
3137 let mut seen_fields = FxHashMap();
3139 let mut error_happened = false;
3141 // Typecheck each field.
3142 for field in ast_fields {
3143 let final_field_type;
3144 let field_type_hint;
3146 let ident = tcx.adjust(field.name.node, variant.did, self.body_id).0;
3147 if let Some(v_field) = remaining_fields.remove(&ident) {
3148 final_field_type = self.field_ty(field.span, v_field, substs);
3149 field_type_hint = self.field_ty(field.span, v_field, hint_substs);
3151 seen_fields.insert(field.name.node, field.span);
3153 // we don't look at stability attributes on
3154 // struct-like enums (yet...), but it's definitely not
3155 // a bug to have construct one.
3156 if adt_kind != ty::AdtKind::Enum {
3157 tcx.check_stability(v_field.did, expr_id, field.span);
3160 error_happened = true;
3161 final_field_type = tcx.types.err;
3162 field_type_hint = tcx.types.err;
3163 if let Some(_) = variant.find_field_named(field.name.node) {
3164 let mut err = struct_span_err!(self.tcx.sess,
3167 "field `{}` specified more than once",
3170 err.span_label(field.name.span, "used more than once");
3172 if let Some(prev_span) = seen_fields.get(&field.name.node) {
3173 err.span_label(*prev_span, format!("first use of `{}`", field.name.node));
3178 self.report_unknown_field(adt_ty, variant, field, ast_fields, kind_name);
3182 // Make sure to give a type to the field even if there's
3183 // an error, so we can continue typechecking
3184 let ty = self.check_expr_with_hint(&field.expr, field_type_hint);
3185 self.demand_coerce(&field.expr, ty, final_field_type);
3188 // Make sure the programmer specified correct number of fields.
3189 if kind_name == "union" {
3190 if ast_fields.len() != 1 {
3191 tcx.sess.span_err(span, "union expressions should have exactly one field");
3193 } else if check_completeness && !error_happened && !remaining_fields.is_empty() {
3194 let len = remaining_fields.len();
3196 let mut displayable_field_names = remaining_fields
3198 .map(|ident| ident.name.as_str())
3199 .collect::<Vec<_>>();
3201 displayable_field_names.sort();
3203 let truncated_fields_error = if len <= 3 {
3206 format!(" and {} other field{}", (len - 3), if len - 3 == 1 {""} else {"s"})
3209 let remaining_fields_names = displayable_field_names.iter().take(3)
3210 .map(|n| format!("`{}`", n))
3211 .collect::<Vec<_>>()
3214 struct_span_err!(tcx.sess, span, E0063,
3215 "missing field{} {}{} in initializer of `{}`",
3216 if remaining_fields.len() == 1 {""} else {"s"},
3217 remaining_fields_names,
3218 truncated_fields_error,
3220 .span_label(span, format!("missing {}{}",
3221 remaining_fields_names,
3222 truncated_fields_error))
3227 fn check_struct_fields_on_error(&self,
3228 fields: &'gcx [hir::Field],
3229 base_expr: &'gcx Option<P<hir::Expr>>) {
3230 for field in fields {
3231 self.check_expr(&field.expr);
3235 self.check_expr(&base);
3241 pub fn check_struct_path(&self,
3243 node_id: ast::NodeId)
3244 -> Option<(&'tcx ty::VariantDef, Ty<'tcx>)> {
3245 let path_span = match *qpath {
3246 hir::QPath::Resolved(_, ref path) => path.span,
3247 hir::QPath::TypeRelative(ref qself, _) => qself.span
3249 let (def, ty) = self.finish_resolving_struct_path(qpath, path_span, node_id);
3250 let variant = match def {
3252 self.set_tainted_by_errors();
3255 Def::Variant(..) => {
3257 ty::TyAdt(adt, substs) => {
3258 Some((adt.variant_of_def(def), adt.did, substs))
3260 _ => bug!("unexpected type: {:?}", ty.sty)
3263 Def::Struct(..) | Def::Union(..) | Def::TyAlias(..) |
3264 Def::AssociatedTy(..) | Def::SelfTy(..) => {
3266 ty::TyAdt(adt, substs) if !adt.is_enum() => {
3267 Some((adt.struct_variant(), adt.did, substs))
3272 _ => bug!("unexpected definition: {:?}", def)
3275 if let Some((variant, did, substs)) = variant {
3276 // Check bounds on type arguments used in the path.
3277 let bounds = self.instantiate_bounds(path_span, did, substs);
3278 let cause = traits::ObligationCause::new(path_span, self.body_id,
3279 traits::ItemObligation(did));
3280 self.add_obligations_for_parameters(cause, &bounds);
3284 struct_span_err!(self.tcx.sess, path_span, E0071,
3285 "expected struct, variant or union type, found {}",
3286 ty.sort_string(self.tcx))
3287 .span_label(path_span, "not a struct")
3293 fn check_expr_struct(&self,
3295 expected: Expectation<'tcx>,
3297 fields: &'gcx [hir::Field],
3298 base_expr: &'gcx Option<P<hir::Expr>>) -> Ty<'tcx>
3300 // Find the relevant variant
3301 let (variant, struct_ty) =
3302 if let Some(variant_ty) = self.check_struct_path(qpath, expr.id) {
3305 self.check_struct_fields_on_error(fields, base_expr);
3306 return self.tcx.types.err;
3309 let path_span = match *qpath {
3310 hir::QPath::Resolved(_, ref path) => path.span,
3311 hir::QPath::TypeRelative(ref qself, _) => qself.span
3314 self.check_expr_struct_fields(struct_ty, expected, expr.id, path_span, variant, fields,
3315 base_expr.is_none());
3316 if let &Some(ref base_expr) = base_expr {
3317 self.check_expr_has_type(base_expr, struct_ty);
3318 match struct_ty.sty {
3319 ty::TyAdt(adt, substs) if adt.is_struct() => {
3320 self.tables.borrow_mut().fru_field_types.insert(
3322 adt.struct_variant().fields.iter().map(|f| {
3323 self.normalize_associated_types_in(
3324 expr.span, &f.ty(self.tcx, substs)
3330 span_err!(self.tcx.sess, base_expr.span, E0436,
3331 "functional record update syntax requires a struct");
3335 self.require_type_is_sized(struct_ty, expr.span, traits::StructInitializerSized);
3341 /// If an expression has any sub-expressions that result in a type error,
3342 /// inspecting that expression's type with `ty.references_error()` will return
3343 /// true. Likewise, if an expression is known to diverge, inspecting its
3344 /// type with `ty::type_is_bot` will return true (n.b.: since Rust is
3345 /// strict, _|_ can appear in the type of an expression that does not,
3346 /// itself, diverge: for example, fn() -> _|_.)
3347 /// Note that inspecting a type's structure *directly* may expose the fact
3348 /// that there are actually multiple representations for `TyError`, so avoid
3349 /// that when err needs to be handled differently.
3350 fn check_expr_with_expectation_and_lvalue_pref(&self,
3351 expr: &'gcx hir::Expr,
3352 expected: Expectation<'tcx>,
3353 lvalue_pref: LvaluePreference) -> Ty<'tcx> {
3354 debug!(">> typechecking: expr={:?} expected={:?}",
3357 // Warn for expressions after diverging siblings.
3358 self.warn_if_unreachable(expr.id, expr.span, "expression");
3360 // Hide the outer diverging and has_errors flags.
3361 let old_diverges = self.diverges.get();
3362 let old_has_errors = self.has_errors.get();
3363 self.diverges.set(Diverges::Maybe);
3364 self.has_errors.set(false);
3366 let ty = self.check_expr_kind(expr, expected, lvalue_pref);
3368 // Warn for non-block expressions with diverging children.
3371 hir::ExprLoop(..) | hir::ExprWhile(..) |
3372 hir::ExprIf(..) | hir::ExprMatch(..) => {}
3374 _ => self.warn_if_unreachable(expr.id, expr.span, "expression")
3377 // Any expression that produces a value of type `!` must have diverged
3379 self.diverges.set(self.diverges.get() | Diverges::Always);
3382 // Record the type, which applies it effects.
3383 // We need to do this after the warning above, so that
3384 // we don't warn for the diverging expression itself.
3385 self.write_ty(expr.id, ty);
3387 // Combine the diverging and has_error flags.
3388 self.diverges.set(self.diverges.get() | old_diverges);
3389 self.has_errors.set(self.has_errors.get() | old_has_errors);
3391 debug!("type of {} is...", self.tcx.hir.node_to_string(expr.id));
3392 debug!("... {:?}, expected is {:?}", ty, expected);
3397 fn check_expr_kind(&self,
3398 expr: &'gcx hir::Expr,
3399 expected: Expectation<'tcx>,
3400 lvalue_pref: LvaluePreference) -> Ty<'tcx> {
3404 hir::ExprBox(ref subexpr) => {
3405 let expected_inner = expected.to_option(self).map_or(NoExpectation, |ty| {
3407 ty::TyAdt(def, _) if def.is_box()
3408 => Expectation::rvalue_hint(self, ty.boxed_ty()),
3412 let referent_ty = self.check_expr_with_expectation(subexpr, expected_inner);
3413 tcx.mk_box(referent_ty)
3416 hir::ExprLit(ref lit) => {
3417 self.check_lit(&lit, expected)
3419 hir::ExprBinary(op, ref lhs, ref rhs) => {
3420 self.check_binop(expr, op, lhs, rhs)
3422 hir::ExprAssignOp(op, ref lhs, ref rhs) => {
3423 self.check_binop_assign(expr, op, lhs, rhs)
3425 hir::ExprUnary(unop, ref oprnd) => {
3426 let expected_inner = match unop {
3427 hir::UnNot | hir::UnNeg => {
3434 let lvalue_pref = match unop {
3435 hir::UnDeref => lvalue_pref,
3438 let mut oprnd_t = self.check_expr_with_expectation_and_lvalue_pref(&oprnd,
3442 if !oprnd_t.references_error() {
3445 oprnd_t = self.structurally_resolved_type(expr.span, oprnd_t);
3447 if let Some(mt) = oprnd_t.builtin_deref(true, NoPreference) {
3449 } else if let Some(ok) = self.try_overloaded_deref(
3450 expr.span, oprnd_t, lvalue_pref) {
3451 let (autoref, method) = self.register_infer_ok_obligations(ok);
3452 self.apply_adjustment(oprnd.id, Adjustment {
3453 kind: Adjust::DerefRef {
3458 target: method.sig.inputs()[0]
3460 oprnd_t = self.make_overloaded_lvalue_return_type(method).ty;
3461 self.write_method_call(expr.id, method);
3463 self.type_error_message(expr.span, |actual| {
3464 format!("type `{}` cannot be \
3465 dereferenced", actual)
3467 oprnd_t = tcx.types.err;
3471 oprnd_t = self.structurally_resolved_type(oprnd.span,
3473 let result = self.check_user_unop("!", "not",
3474 tcx.lang_items.not_trait(),
3475 expr, &oprnd, oprnd_t, unop);
3476 // If it's builtin, we can reuse the type, this helps inference.
3477 if !(oprnd_t.is_integral() || oprnd_t.sty == ty::TyBool) {
3482 oprnd_t = self.structurally_resolved_type(oprnd.span,
3484 let result = self.check_user_unop("-", "neg",
3485 tcx.lang_items.neg_trait(),
3486 expr, &oprnd, oprnd_t, unop);
3487 // If it's builtin, we can reuse the type, this helps inference.
3488 if !(oprnd_t.is_integral() || oprnd_t.is_fp()) {
3496 hir::ExprAddrOf(mutbl, ref oprnd) => {
3497 let hint = expected.only_has_type(self).map_or(NoExpectation, |ty| {
3499 ty::TyRef(_, ref mt) | ty::TyRawPtr(ref mt) => {
3500 if self.tcx.expr_is_lval(&oprnd) {
3501 // Lvalues may legitimately have unsized types.
3502 // For example, dereferences of a fat pointer and
3503 // the last field of a struct can be unsized.
3504 ExpectHasType(mt.ty)
3506 Expectation::rvalue_hint(self, mt.ty)
3512 let lvalue_pref = LvaluePreference::from_mutbl(mutbl);
3513 let ty = self.check_expr_with_expectation_and_lvalue_pref(&oprnd, hint, lvalue_pref);
3515 let tm = ty::TypeAndMut { ty: ty, mutbl: mutbl };
3516 if tm.ty.references_error() {
3519 // Note: at this point, we cannot say what the best lifetime
3520 // is to use for resulting pointer. We want to use the
3521 // shortest lifetime possible so as to avoid spurious borrowck
3522 // errors. Moreover, the longest lifetime will depend on the
3523 // precise details of the value whose address is being taken
3524 // (and how long it is valid), which we don't know yet until type
3525 // inference is complete.
3527 // Therefore, here we simply generate a region variable. The
3528 // region inferencer will then select the ultimate value.
3529 // Finally, borrowck is charged with guaranteeing that the
3530 // value whose address was taken can actually be made to live
3531 // as long as it needs to live.
3532 let region = self.next_region_var(infer::AddrOfRegion(expr.span));
3533 tcx.mk_ref(region, tm)
3536 hir::ExprPath(ref qpath) => {
3537 let (def, opt_ty, segments) = self.resolve_ty_and_def_ufcs(qpath,
3538 expr.id, expr.span);
3539 let ty = if def != Def::Err {
3540 self.instantiate_value_path(segments, opt_ty, def, expr.span, id)
3542 self.set_tainted_by_errors();
3546 // We always require that the type provided as the value for
3547 // a type parameter outlives the moment of instantiation.
3548 let substs = self.tables.borrow().node_substs(expr.id);
3549 self.add_wf_bounds(substs, expr);
3553 hir::ExprInlineAsm(_, ref outputs, ref inputs) => {
3554 for output in outputs {
3555 self.check_expr(output);
3557 for input in inputs {
3558 self.check_expr(input);
3562 hir::ExprBreak(destination, ref expr_opt) => {
3563 if let Some(target_id) = destination.target_id.opt_id() {
3564 let (e_ty, e_diverges, cause);
3565 if let Some(ref e) = *expr_opt {
3566 // If this is a break with a value, we need to type-check
3567 // the expression. Get an expected type from the loop context.
3568 let opt_coerce_to = {
3569 let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
3570 enclosing_breakables.find_breakable(target_id)
3573 .map(|coerce| coerce.expected_ty())
3576 // If the loop context is not a `loop { }`, then break with
3577 // a value is illegal, and `opt_coerce_to` will be `None`.
3578 // Just set expectation to error in that case.
3579 let coerce_to = opt_coerce_to.unwrap_or(tcx.types.err);
3581 // Recurse without `enclosing_breakables` borrowed.
3582 e_ty = self.check_expr_with_hint(e, coerce_to);
3583 e_diverges = self.diverges.get();
3584 cause = self.misc(e.span);
3586 // Otherwise, this is a break *without* a value. That's
3587 // always legal, and is equivalent to `break ()`.
3588 e_ty = tcx.mk_nil();
3589 e_diverges = Diverges::Maybe;
3590 cause = self.misc(expr.span);
3593 // Now that we have type-checked `expr_opt`, borrow
3594 // the `enclosing_loops` field and let's coerce the
3595 // type of `expr_opt` into what is expected.
3596 let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
3597 let ctxt = enclosing_breakables.find_breakable(target_id);
3598 if let Some(ref mut coerce) = ctxt.coerce {
3599 if let Some(ref e) = *expr_opt {
3600 coerce.coerce(self, &cause, e, e_ty, e_diverges);
3602 assert!(e_ty.is_nil());
3603 coerce.coerce_forced_unit(self, &cause, &mut |_| (), true);
3606 // If `ctxt.coerce` is `None`, we can just ignore
3607 // the type of the expresison. This is because
3608 // either this was a break *without* a value, in
3609 // which case it is always a legal type (`()`), or
3610 // else an error would have been flagged by the
3611 // `loops` pass for using break with an expression
3612 // where you are not supposed to.
3613 assert!(expr_opt.is_none() || self.tcx.sess.err_count() > 0);
3616 ctxt.may_break = true;
3618 // Otherwise, we failed to find the enclosing loop;
3619 // this can only happen if the `break` was not
3620 // inside a loop at all, which is caught by the
3621 // loop-checking pass.
3622 assert!(self.tcx.sess.err_count() > 0);
3625 // the type of a `break` is always `!`, since it diverges
3628 hir::ExprAgain(_) => { tcx.types.never }
3629 hir::ExprRet(ref expr_opt) => {
3630 if self.ret_coercion.is_none() {
3631 struct_span_err!(self.tcx.sess, expr.span, E0572,
3632 "return statement outside of function body").emit();
3633 } else if let Some(ref e) = *expr_opt {
3634 self.check_return_expr(e);
3636 let mut coercion = self.ret_coercion.as_ref().unwrap().borrow_mut();
3637 let cause = self.cause(expr.span, ObligationCauseCode::ReturnNoExpression);
3638 coercion.coerce_forced_unit(self, &cause, &mut |_| (), true);
3642 hir::ExprAssign(ref lhs, ref rhs) => {
3643 let lhs_ty = self.check_expr_with_lvalue_pref(&lhs, PreferMutLvalue);
3646 if !tcx.expr_is_lval(&lhs) {
3648 tcx.sess, expr.span, E0070,
3649 "invalid left-hand side expression")
3652 "left-hand of expression not valid")
3656 let rhs_ty = self.check_expr_coercable_to_type(&rhs, lhs_ty);
3658 self.require_type_is_sized(lhs_ty, lhs.span, traits::AssignmentLhsSized);
3660 if lhs_ty.references_error() || rhs_ty.references_error() {
3666 hir::ExprIf(ref cond, ref then_expr, ref opt_else_expr) => {
3667 self.check_then_else(&cond, then_expr, opt_else_expr.as_ref().map(|e| &**e),
3668 expr.span, expected)
3670 hir::ExprWhile(ref cond, ref body, _) => {
3671 let ctxt = BreakableCtxt {
3672 // cannot use break with a value from a while loop
3677 self.with_breakable_ctxt(expr.id, ctxt, || {
3678 self.check_expr_has_type(&cond, tcx.types.bool);
3679 let cond_diverging = self.diverges.get();
3680 self.check_block_no_value(&body);
3682 // We may never reach the body so it diverging means nothing.
3683 self.diverges.set(cond_diverging);
3688 hir::ExprLoop(ref body, _, source) => {
3689 let coerce = match source {
3690 // you can only use break with a value from a normal `loop { }`
3691 hir::LoopSource::Loop => {
3692 let coerce_to = expected.coercion_target_type(self, body.span);
3693 Some(CoerceMany::new(coerce_to))
3696 hir::LoopSource::WhileLet |
3697 hir::LoopSource::ForLoop => {
3702 let ctxt = BreakableCtxt {
3704 may_break: false, // will get updated if/when we find a `break`
3707 let (ctxt, ()) = self.with_breakable_ctxt(expr.id, ctxt, || {
3708 self.check_block_no_value(&body);
3712 // No way to know whether it's diverging because
3713 // of a `break` or an outer `break` or `return.
3714 self.diverges.set(Diverges::Maybe);
3717 // If we permit break with a value, then result type is
3718 // the LUB of the breaks (possibly ! if none); else, it
3719 // is nil. This makes sense because infinite loops
3720 // (which would have type !) are only possible iff we
3721 // permit break with a value [1].
3722 assert!(ctxt.coerce.is_some() || ctxt.may_break); // [1]
3723 ctxt.coerce.map(|c| c.complete(self)).unwrap_or(self.tcx.mk_nil())
3725 hir::ExprMatch(ref discrim, ref arms, match_src) => {
3726 self.check_match(expr, &discrim, arms, expected, match_src)
3728 hir::ExprClosure(capture, ref decl, body_id, _) => {
3729 self.check_expr_closure(expr, capture, &decl, body_id, expected)
3731 hir::ExprBlock(ref body) => {
3732 self.check_block_with_expected(&body, expected)
3734 hir::ExprCall(ref callee, ref args) => {
3735 self.check_call(expr, &callee, args, expected)
3737 hir::ExprMethodCall(name, ref tps, ref args) => {
3738 self.check_method_call(expr, name, args, &tps[..], expected, lvalue_pref)
3740 hir::ExprCast(ref e, ref t) => {
3741 // Find the type of `e`. Supply hints based on the type we are casting to,
3743 let t_cast = self.to_ty(t);
3744 let t_cast = self.resolve_type_vars_if_possible(&t_cast);
3745 let t_expr = self.check_expr_with_expectation(e, ExpectCastableToType(t_cast));
3746 let t_cast = self.resolve_type_vars_if_possible(&t_cast);
3747 let diverges = self.diverges.get();
3749 // Eagerly check for some obvious errors.
3750 if t_expr.references_error() || t_cast.references_error() {
3753 // Defer other checks until we're done type checking.
3754 let mut deferred_cast_checks = self.deferred_cast_checks.borrow_mut();
3755 match cast::CastCheck::new(self, e, t_expr, diverges, t_cast, t.span, expr.span) {
3757 deferred_cast_checks.push(cast_check);
3760 Err(ErrorReported) => {
3766 hir::ExprType(ref e, ref t) => {
3767 let typ = self.to_ty(&t);
3768 self.check_expr_eq_type(&e, typ);
3771 hir::ExprArray(ref args) => {
3772 let uty = expected.to_option(self).and_then(|uty| {
3774 ty::TyArray(ty, _) | ty::TySlice(ty) => Some(ty),
3779 let element_ty = if !args.is_empty() {
3780 let coerce_to = uty.unwrap_or_else(
3781 || self.next_ty_var(TypeVariableOrigin::TypeInference(expr.span)));
3782 let mut coerce = CoerceMany::with_coercion_sites(coerce_to, args);
3783 assert_eq!(self.diverges.get(), Diverges::Maybe);
3785 let e_ty = self.check_expr_with_hint(e, coerce_to);
3786 let cause = self.misc(e.span);
3787 coerce.coerce(self, &cause, e, e_ty, self.diverges.get());
3789 coerce.complete(self)
3791 self.next_ty_var(TypeVariableOrigin::TypeInference(expr.span))
3793 tcx.mk_array(element_ty, args.len())
3795 hir::ExprRepeat(ref element, count) => {
3796 let count = eval_length(self.tcx, count, "repeat count")
3799 let uty = match expected {
3800 ExpectHasType(uty) => {
3802 ty::TyArray(ty, _) | ty::TySlice(ty) => Some(ty),
3809 let (element_ty, t) = match uty {
3811 self.check_expr_coercable_to_type(&element, uty);
3815 let t: Ty = self.next_ty_var(TypeVariableOrigin::MiscVariable(element.span));
3816 let element_ty = self.check_expr_has_type(&element, t);
3822 // For [foo, ..n] where n > 1, `foo` must have
3824 let lang_item = self.tcx.require_lang_item(lang_items::CopyTraitLangItem);
3825 self.require_type_meets(t, expr.span, traits::RepeatVec, lang_item);
3828 if element_ty.references_error() {
3831 tcx.mk_array(t, count)
3834 hir::ExprTup(ref elts) => {
3835 let flds = expected.only_has_type(self).and_then(|ty| {
3837 ty::TyTuple(ref flds, _) => Some(&flds[..]),
3842 let elt_ts_iter = elts.iter().enumerate().map(|(i, e)| {
3843 let t = match flds {
3844 Some(ref fs) if i < fs.len() => {
3846 self.check_expr_coercable_to_type(&e, ety);
3850 self.check_expr_with_expectation(&e, NoExpectation)
3855 let tuple = tcx.mk_tup(elt_ts_iter, false);
3856 if tuple.references_error() {
3862 hir::ExprStruct(ref qpath, ref fields, ref base_expr) => {
3863 self.check_expr_struct(expr, expected, qpath, fields, base_expr)
3865 hir::ExprField(ref base, ref field) => {
3866 self.check_field(expr, lvalue_pref, &base, field)
3868 hir::ExprTupField(ref base, idx) => {
3869 self.check_tup_field(expr, lvalue_pref, &base, idx)
3871 hir::ExprIndex(ref base, ref idx) => {
3872 let base_t = self.check_expr_with_lvalue_pref(&base, lvalue_pref);
3873 let idx_t = self.check_expr(&idx);
3875 if base_t.references_error() {
3877 } else if idx_t.references_error() {
3880 let base_t = self.structurally_resolved_type(expr.span, base_t);
3881 match self.lookup_indexing(expr, base, base_t, idx_t, lvalue_pref) {
3882 Some((index_ty, element_ty)) => {
3883 self.demand_coerce(idx, idx_t, index_ty);
3887 let mut err = self.type_error_struct(
3890 format!("cannot index a value of type `{}`",
3894 // Try to give some advice about indexing tuples.
3895 if let ty::TyTuple(..) = base_t.sty {
3896 let mut needs_note = true;
3897 // If the index is an integer, we can show the actual
3898 // fixed expression:
3899 if let hir::ExprLit(ref lit) = idx.node {
3900 if let ast::LitKind::Int(i,
3901 ast::LitIntType::Unsuffixed) = lit.node {
3902 let snip = tcx.sess.codemap().span_to_snippet(base.span);
3903 if let Ok(snip) = snip {
3904 err.span_suggestion(expr.span,
3905 "to access tuple elements, use",
3906 format!("{}.{}", snip, i));
3912 err.help("to access tuple elements, use tuple indexing \
3913 syntax (e.g. `tuple.0`)");
3925 // Finish resolving a path in a struct expression or pattern `S::A { .. }` if necessary.
3926 // The newly resolved definition is written into `type_dependent_defs`.
3927 fn finish_resolving_struct_path(&self,
3930 node_id: ast::NodeId)
3934 hir::QPath::Resolved(ref maybe_qself, ref path) => {
3935 let opt_self_ty = maybe_qself.as_ref().map(|qself| self.to_ty(qself));
3936 let ty = AstConv::def_to_ty(self, opt_self_ty, path, true);
3939 hir::QPath::TypeRelative(ref qself, ref segment) => {
3940 let ty = self.to_ty(qself);
3942 let def = if let hir::TyPath(hir::QPath::Resolved(_, ref path)) = qself.node {
3947 let (ty, def) = AstConv::associated_path_def_to_ty(self, node_id, path_span,
3950 // Write back the new resolution.
3951 self.tables.borrow_mut().type_dependent_defs.insert(node_id, def);
3958 // Resolve associated value path into a base type and associated constant or method definition.
3959 // The newly resolved definition is written into `type_dependent_defs`.
3960 pub fn resolve_ty_and_def_ufcs<'b>(&self,
3961 qpath: &'b hir::QPath,
3962 node_id: ast::NodeId,
3964 -> (Def, Option<Ty<'tcx>>, &'b [hir::PathSegment])
3966 let (ty, item_segment) = match *qpath {
3967 hir::QPath::Resolved(ref opt_qself, ref path) => {
3969 opt_qself.as_ref().map(|qself| self.to_ty(qself)),
3970 &path.segments[..]);
3972 hir::QPath::TypeRelative(ref qself, ref segment) => {
3973 (self.to_ty(qself), segment)
3976 let item_name = item_segment.name;
3977 let def = match self.resolve_ufcs(span, item_name, ty, node_id) {
3980 let def = match error {
3981 method::MethodError::PrivateMatch(def) => def,
3984 if item_name != keywords::Invalid.name() {
3985 self.report_method_error(span, ty, item_name, None, error, None);
3991 // Write back the new resolution.
3992 self.tables.borrow_mut().type_dependent_defs.insert(node_id, def);
3993 (def, Some(ty), slice::ref_slice(&**item_segment))
3996 pub fn check_decl_initializer(&self,
3997 local: &'gcx hir::Local,
3998 init: &'gcx hir::Expr) -> Ty<'tcx>
4000 let ref_bindings = local.pat.contains_ref_binding();
4002 let local_ty = self.local_ty(init.span, local.id);
4003 if let Some(m) = ref_bindings {
4004 // Somewhat subtle: if we have a `ref` binding in the pattern,
4005 // we want to avoid introducing coercions for the RHS. This is
4006 // both because it helps preserve sanity and, in the case of
4007 // ref mut, for soundness (issue #23116). In particular, in
4008 // the latter case, we need to be clear that the type of the
4009 // referent for the reference that results is *equal to* the
4010 // type of the lvalue it is referencing, and not some
4011 // supertype thereof.
4012 let init_ty = self.check_expr_with_lvalue_pref(init, LvaluePreference::from_mutbl(m));
4013 self.demand_eqtype(init.span, init_ty, local_ty);
4016 self.check_expr_coercable_to_type(init, local_ty)
4020 pub fn check_decl_local(&self, local: &'gcx hir::Local) {
4021 let t = self.local_ty(local.span, local.id);
4022 self.write_ty(local.id, t);
4024 if let Some(ref init) = local.init {
4025 let init_ty = self.check_decl_initializer(local, &init);
4026 if init_ty.references_error() {
4027 self.write_ty(local.id, init_ty);
4031 self.check_pat(&local.pat, t);
4032 let pat_ty = self.node_ty(local.pat.id);
4033 if pat_ty.references_error() {
4034 self.write_ty(local.id, pat_ty);
4038 pub fn check_stmt(&self, stmt: &'gcx hir::Stmt) {
4039 // Don't do all the complex logic below for DeclItem.
4041 hir::StmtDecl(ref decl, id) => {
4043 hir::DeclLocal(_) => {}
4044 hir::DeclItem(_) => {
4050 hir::StmtExpr(..) | hir::StmtSemi(..) => {}
4053 self.warn_if_unreachable(stmt.node.id(), stmt.span, "statement");
4055 // Hide the outer diverging and has_errors flags.
4056 let old_diverges = self.diverges.get();
4057 let old_has_errors = self.has_errors.get();
4058 self.diverges.set(Diverges::Maybe);
4059 self.has_errors.set(false);
4061 let (node_id, _span) = match stmt.node {
4062 hir::StmtDecl(ref decl, id) => {
4063 let span = match decl.node {
4064 hir::DeclLocal(ref l) => {
4065 self.check_decl_local(&l);
4068 hir::DeclItem(_) => {/* ignore for now */
4074 hir::StmtExpr(ref expr, id) => {
4075 // Check with expected type of ()
4076 self.check_expr_has_type(&expr, self.tcx.mk_nil());
4079 hir::StmtSemi(ref expr, id) => {
4080 self.check_expr(&expr);
4085 if self.has_errors.get() {
4086 self.write_error(node_id);
4088 self.write_nil(node_id);
4091 // Combine the diverging and has_error flags.
4092 self.diverges.set(self.diverges.get() | old_diverges);
4093 self.has_errors.set(self.has_errors.get() | old_has_errors);
4096 pub fn check_block_no_value(&self, blk: &'gcx hir::Block) {
4097 let unit = self.tcx.mk_nil();
4098 let ty = self.check_block_with_expected(blk, ExpectHasType(unit));
4100 // if the block produces a `!` value, that can always be
4101 // (effectively) coerced to unit.
4103 self.demand_suptype(blk.span, unit, ty);
4107 fn check_block_with_expected(&self,
4108 blk: &'gcx hir::Block,
4109 expected: Expectation<'tcx>) -> Ty<'tcx> {
4111 let mut fcx_ps = self.ps.borrow_mut();
4112 let unsafety_state = fcx_ps.recurse(blk);
4113 replace(&mut *fcx_ps, unsafety_state)
4116 // In some cases, blocks have just one exit, but other blocks
4117 // can be targeted by multiple breaks. This cannot happen in
4118 // normal Rust syntax today, but it can happen when we desugar
4119 // a `do catch { ... }` expression.
4123 // 'a: { if true { break 'a Err(()); } Ok(()) }
4125 // Here we would wind up with two coercions, one from
4126 // `Err(())` and the other from the tail expression
4127 // `Ok(())`. If the tail expression is omitted, that's a
4128 // "forced unit" -- unless the block diverges, in which
4129 // case we can ignore the tail expression (e.g., `'a: {
4130 // break 'a 22; }` would not force the type of the block
4132 let tail_expr = blk.expr.as_ref();
4133 let coerce_to_ty = expected.coercion_target_type(self, blk.span);
4134 let coerce = if blk.targeted_by_break {
4135 CoerceMany::new(coerce_to_ty)
4137 let tail_expr: &[P<hir::Expr>] = match tail_expr {
4138 Some(e) => ref_slice(e),
4141 CoerceMany::with_coercion_sites(coerce_to_ty, tail_expr)
4144 let ctxt = BreakableCtxt {
4145 coerce: Some(coerce),
4149 let (ctxt, ()) = self.with_breakable_ctxt(blk.id, ctxt, || {
4150 for s in &blk.stmts {
4154 // check the tail expression **without** holding the
4155 // `enclosing_breakables` lock below.
4156 let tail_expr_ty = tail_expr.map(|t| self.check_expr_with_expectation(t, expected));
4158 let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
4159 let mut ctxt = enclosing_breakables.find_breakable(blk.id);
4160 let mut coerce = ctxt.coerce.as_mut().unwrap();
4161 if let Some(tail_expr_ty) = tail_expr_ty {
4162 let tail_expr = tail_expr.unwrap();
4164 &self.misc(tail_expr.span),
4167 self.diverges.get());
4169 // Subtle: if there is no explicit tail expression,
4170 // that is typically equivalent to a tail expression
4171 // of `()` -- except if the block diverges. In that
4172 // case, there is no value supplied from the tail
4173 // expression (assuming there are no other breaks,
4174 // this implies that the type of the block will be
4177 // #41425 -- label the implicit `()` as being the
4178 // "found type" here, rather than the "expected type".
4179 if !self.diverges.get().always() {
4180 coerce.coerce_forced_unit(self, &self.misc(blk.span), &mut |err| {
4181 if let Some(expected_ty) = expected.only_has_type(self) {
4182 self.consider_hint_about_removing_semicolon(blk,
4191 let mut ty = ctxt.coerce.unwrap().complete(self);
4193 if self.has_errors.get() || ty.references_error() {
4194 ty = self.tcx.types.err
4197 self.write_ty(blk.id, ty);
4199 *self.ps.borrow_mut() = prev;
4203 /// A common error is to add an extra semicolon:
4206 /// fn foo() -> usize {
4211 /// This routine checks if the final statement in a block is an
4212 /// expression with an explicit semicolon whose type is compatible
4213 /// with `expected_ty`. If so, it suggests removing the semicolon.
4214 fn consider_hint_about_removing_semicolon(&self,
4215 blk: &'gcx hir::Block,
4216 expected_ty: Ty<'tcx>,
4217 err: &mut DiagnosticBuilder) {
4218 // Be helpful when the user wrote `{... expr;}` and
4219 // taking the `;` off is enough to fix the error.
4220 let last_stmt = match blk.stmts.last() {
4224 let last_expr = match last_stmt.node {
4225 hir::StmtSemi(ref e, _) => e,
4228 let last_expr_ty = self.expr_ty(last_expr);
4229 if self.can_sub_types(last_expr_ty, expected_ty).is_err() {
4232 let original_span = original_sp(last_stmt.span, blk.span);
4233 let span_semi = Span {
4234 lo: original_span.hi - BytePos(1),
4235 hi: original_span.hi,
4236 ctxt: original_span.ctxt,
4238 err.span_help(span_semi, "consider removing this semicolon:");
4241 // Instantiates the given path, which must refer to an item with the given
4242 // number of type parameters and type.
4243 pub fn instantiate_value_path(&self,
4244 segments: &[hir::PathSegment],
4245 opt_self_ty: Option<Ty<'tcx>>,
4248 node_id: ast::NodeId)
4250 debug!("instantiate_value_path(path={:?}, def={:?}, node_id={})",
4255 // We need to extract the type parameters supplied by the user in
4256 // the path `path`. Due to the current setup, this is a bit of a
4257 // tricky-process; the problem is that resolve only tells us the
4258 // end-point of the path resolution, and not the intermediate steps.
4259 // Luckily, we can (at least for now) deduce the intermediate steps
4260 // just from the end-point.
4262 // There are basically four cases to consider:
4264 // 1. Reference to a constructor of enum variant or struct:
4266 // struct Foo<T>(...)
4267 // enum E<T> { Foo(...) }
4269 // In these cases, the parameters are declared in the type
4272 // 2. Reference to a fn item or a free constant:
4276 // In this case, the path will again always have the form
4277 // `a::b::foo::<T>` where only the final segment should have
4278 // type parameters. However, in this case, those parameters are
4279 // declared on a value, and hence are in the `FnSpace`.
4281 // 3. Reference to a method or an associated constant:
4283 // impl<A> SomeStruct<A> {
4287 // Here we can have a path like
4288 // `a::b::SomeStruct::<A>::foo::<B>`, in which case parameters
4289 // may appear in two places. The penultimate segment,
4290 // `SomeStruct::<A>`, contains parameters in TypeSpace, and the
4291 // final segment, `foo::<B>` contains parameters in fn space.
4293 // 4. Reference to a local variable
4295 // Local variables can't have any type parameters.
4297 // The first step then is to categorize the segments appropriately.
4299 assert!(!segments.is_empty());
4301 let mut ufcs_associated = None;
4302 let mut type_segment = None;
4303 let mut fn_segment = None;
4305 // Case 1. Reference to a struct/variant constructor.
4306 Def::StructCtor(def_id, ..) |
4307 Def::VariantCtor(def_id, ..) => {
4308 // Everything but the final segment should have no
4309 // parameters at all.
4310 let mut generics = self.tcx.generics_of(def_id);
4311 if let Some(def_id) = generics.parent {
4312 // Variant and struct constructors use the
4313 // generics of their parent type definition.
4314 generics = self.tcx.generics_of(def_id);
4316 type_segment = Some((segments.last().unwrap(), generics));
4319 // Case 2. Reference to a top-level value.
4321 Def::Const(def_id) |
4322 Def::Static(def_id, _) => {
4323 fn_segment = Some((segments.last().unwrap(),
4324 self.tcx.generics_of(def_id)));
4327 // Case 3. Reference to a method or associated const.
4328 Def::Method(def_id) |
4329 Def::AssociatedConst(def_id) => {
4330 let container = self.tcx.associated_item(def_id).container;
4332 ty::TraitContainer(trait_did) => {
4333 callee::check_legal_trait_for_method_call(self.tcx, span, trait_did)
4335 ty::ImplContainer(_) => {}
4338 let generics = self.tcx.generics_of(def_id);
4339 if segments.len() >= 2 {
4340 let parent_generics = self.tcx.generics_of(generics.parent.unwrap());
4341 type_segment = Some((&segments[segments.len() - 2], parent_generics));
4343 // `<T>::assoc` will end up here, and so can `T::assoc`.
4344 let self_ty = opt_self_ty.expect("UFCS sugared assoc missing Self");
4345 ufcs_associated = Some((container, self_ty));
4347 fn_segment = Some((segments.last().unwrap(), generics));
4350 // Case 4. Local variable, no generics.
4351 Def::Local(..) | Def::Upvar(..) => {}
4353 _ => bug!("unexpected definition: {:?}", def),
4356 debug!("type_segment={:?} fn_segment={:?}", type_segment, fn_segment);
4358 // Now that we have categorized what space the parameters for each
4359 // segment belong to, let's sort out the parameters that the user
4360 // provided (if any) into their appropriate spaces. We'll also report
4361 // errors if type parameters are provided in an inappropriate place.
4362 let poly_segments = type_segment.is_some() as usize +
4363 fn_segment.is_some() as usize;
4364 AstConv::prohibit_type_params(self, &segments[..segments.len() - poly_segments]);
4367 Def::Local(def_id) | Def::Upvar(def_id, ..) => {
4368 let nid = self.tcx.hir.as_local_node_id(def_id).unwrap();
4369 let ty = self.local_ty(span, nid);
4370 let ty = self.normalize_associated_types_in(span, &ty);
4371 self.write_ty(node_id, ty);
4377 // Now we have to compare the types that the user *actually*
4378 // provided against the types that were *expected*. If the user
4379 // did not provide any types, then we want to substitute inference
4380 // variables. If the user provided some types, we may still need
4381 // to add defaults. If the user provided *too many* types, that's
4383 self.check_path_parameter_count(span, &mut type_segment);
4384 self.check_path_parameter_count(span, &mut fn_segment);
4386 let (fn_start, has_self) = match (type_segment, fn_segment) {
4387 (_, Some((_, generics))) => {
4388 (generics.parent_count(), generics.has_self)
4390 (Some((_, generics)), None) => {
4391 (generics.own_count(), generics.has_self)
4393 (None, None) => (0, false)
4395 let substs = Substs::for_item(self.tcx, def.def_id(), |def, _| {
4396 let mut i = def.index as usize;
4398 let segment = if i < fn_start {
4399 i -= has_self as usize;
4405 let lifetimes = match segment.map(|(s, _)| &s.parameters) {
4406 Some(&hir::AngleBracketedParameters(ref data)) => &data.lifetimes[..],
4407 Some(&hir::ParenthesizedParameters(_)) => bug!(),
4411 if let Some(lifetime) = lifetimes.get(i) {
4412 AstConv::ast_region_to_region(self, lifetime, Some(def))
4414 self.re_infer(span, Some(def)).unwrap()
4417 let mut i = def.index as usize;
4419 let segment = if i < fn_start {
4420 // Handle Self first, so we can adjust the index to match the AST.
4421 if has_self && i == 0 {
4422 return opt_self_ty.unwrap_or_else(|| {
4423 self.type_var_for_def(span, def, substs)
4426 i -= has_self as usize;
4432 let (types, infer_types) = match segment.map(|(s, _)| &s.parameters) {
4433 Some(&hir::AngleBracketedParameters(ref data)) => {
4434 (&data.types[..], data.infer_types)
4436 Some(&hir::ParenthesizedParameters(_)) => bug!(),
4437 None => (&[][..], true)
4440 // Skip over the lifetimes in the same segment.
4441 if let Some((_, generics)) = segment {
4442 i -= generics.regions.len();
4445 if let Some(ast_ty) = types.get(i) {
4446 // A provided type parameter.
4448 } else if !infer_types && def.has_default {
4449 // No type parameter provided, but a default exists.
4450 let default = self.tcx.type_of(def.def_id);
4453 default.subst_spanned(self.tcx, substs, Some(span))
4456 // No type parameters were provided, we can infer all.
4457 // This can also be reached in some error cases:
4458 // We prefer to use inference variables instead of
4459 // TyError to let type inference recover somewhat.
4460 self.type_var_for_def(span, def, substs)
4464 // The things we are substituting into the type should not contain
4465 // escaping late-bound regions, and nor should the base type scheme.
4466 let ty = self.tcx.type_of(def.def_id());
4467 assert!(!substs.has_escaping_regions());
4468 assert!(!ty.has_escaping_regions());
4470 // Add all the obligations that are required, substituting and
4471 // normalized appropriately.
4472 let bounds = self.instantiate_bounds(span, def.def_id(), &substs);
4473 self.add_obligations_for_parameters(
4474 traits::ObligationCause::new(span, self.body_id, traits::ItemObligation(def.def_id())),
4477 // Substitute the values for the type parameters into the type of
4478 // the referenced item.
4479 let ty_substituted = self.instantiate_type_scheme(span, &substs, &ty);
4481 if let Some((ty::ImplContainer(impl_def_id), self_ty)) = ufcs_associated {
4482 // In the case of `Foo<T>::method` and `<Foo<T>>::method`, if `method`
4483 // is inherent, there is no `Self` parameter, instead, the impl needs
4484 // type parameters, which we can infer by unifying the provided `Self`
4485 // with the substituted impl type.
4486 let ty = self.tcx.type_of(impl_def_id);
4488 let impl_ty = self.instantiate_type_scheme(span, &substs, &ty);
4489 match self.sub_types(false, &self.misc(span), self_ty, impl_ty) {
4490 Ok(ok) => self.register_infer_ok_obligations(ok),
4493 "instantiate_value_path: (UFCS) {:?} was a subtype of {:?} but now is not?",
4500 debug!("instantiate_value_path: type of {:?} is {:?}",
4503 self.write_substs(node_id, substs);
4507 /// Report errors if the provided parameters are too few or too many.
4508 fn check_path_parameter_count(&self,
4510 segment: &mut Option<(&hir::PathSegment, &ty::Generics)>) {
4511 let (lifetimes, types, infer_types, bindings) = {
4512 match segment.map(|(s, _)| &s.parameters) {
4513 Some(&hir::AngleBracketedParameters(ref data)) => {
4514 (&data.lifetimes[..], &data.types[..], data.infer_types, &data.bindings[..])
4516 Some(&hir::ParenthesizedParameters(_)) => {
4517 AstConv::prohibit_parenthesized_params(self, &segment.as_ref().unwrap().0,
4519 (&[][..], &[][..], true, &[][..])
4521 None => (&[][..], &[][..], true, &[][..])
4525 let count_lifetime_params = |n| {
4526 format!("{} lifetime parameter{}", n, if n == 1 { "" } else { "s" })
4528 let count_type_params = |n| {
4529 format!("{} type parameter{}", n, if n == 1 { "" } else { "s" })
4532 // Check provided lifetime parameters.
4533 let lifetime_defs = segment.map_or(&[][..], |(_, generics)| &generics.regions);
4534 if lifetimes.len() > lifetime_defs.len() {
4535 let expected_text = count_lifetime_params(lifetime_defs.len());
4536 let actual_text = count_lifetime_params(lifetimes.len());
4537 struct_span_err!(self.tcx.sess, span, E0088,
4538 "too many lifetime parameters provided: \
4539 expected at most {}, found {}",
4540 expected_text, actual_text)
4541 .span_label(span, format!("expected {}", expected_text))
4543 } else if lifetimes.len() > 0 && lifetimes.len() < lifetime_defs.len() {
4544 let expected_text = count_lifetime_params(lifetime_defs.len());
4545 let actual_text = count_lifetime_params(lifetimes.len());
4546 struct_span_err!(self.tcx.sess, span, E0090,
4547 "too few lifetime parameters provided: \
4548 expected {}, found {}",
4549 expected_text, actual_text)
4550 .span_label(span, format!("expected {}", expected_text))
4554 // The case where there is not enough lifetime parameters is not checked,
4555 // because this is not possible - a function never takes lifetime parameters.
4556 // See discussion for Pull Request 36208.
4558 // Check provided type parameters.
4559 let type_defs = segment.map_or(&[][..], |(_, generics)| {
4560 if generics.parent.is_none() {
4561 &generics.types[generics.has_self as usize..]
4566 let required_len = type_defs.iter().take_while(|d| !d.has_default).count();
4567 if types.len() > type_defs.len() {
4568 let span = types[type_defs.len()].span;
4569 let expected_text = count_type_params(type_defs.len());
4570 let actual_text = count_type_params(types.len());
4571 struct_span_err!(self.tcx.sess, span, E0087,
4572 "too many type parameters provided: \
4573 expected at most {}, found {}",
4574 expected_text, actual_text)
4575 .span_label(span, format!("expected {}", expected_text))
4578 // To prevent derived errors to accumulate due to extra
4579 // type parameters, we force instantiate_value_path to
4580 // use inference variables instead of the provided types.
4582 } else if !infer_types && types.len() < required_len {
4583 let expected_text = count_type_params(required_len);
4584 let actual_text = count_type_params(types.len());
4585 struct_span_err!(self.tcx.sess, span, E0089,
4586 "too few type parameters provided: \
4587 expected {}, found {}",
4588 expected_text, actual_text)
4589 .span_label(span, format!("expected {}", expected_text))
4593 if !bindings.is_empty() {
4594 span_err!(self.tcx.sess, bindings[0].span, E0182,
4595 "unexpected binding of associated item in expression path \
4596 (only allowed in type paths)");
4600 fn structurally_resolve_type_or_else<F>(&self, sp: Span, ty: Ty<'tcx>, f: F)
4602 where F: Fn() -> Ty<'tcx>
4604 let mut ty = self.resolve_type_vars_with_obligations(ty);
4607 let alternative = f();
4610 if alternative.is_ty_var() || alternative.references_error() {
4611 if !self.is_tainted_by_errors() {
4612 self.type_error_message(sp, |_actual| {
4613 "the type of this value must be known in this context".to_string()
4616 self.demand_suptype(sp, self.tcx.types.err, ty);
4617 ty = self.tcx.types.err;
4619 self.demand_suptype(sp, alternative, ty);
4627 // Resolves `typ` by a single level if `typ` is a type variable. If no
4628 // resolution is possible, then an error is reported.
4629 pub fn structurally_resolved_type(&self, sp: Span, ty: Ty<'tcx>) -> Ty<'tcx> {
4630 self.structurally_resolve_type_or_else(sp, ty, || {
4635 fn with_breakable_ctxt<F: FnOnce() -> R, R>(&self, id: ast::NodeId,
4636 ctxt: BreakableCtxt<'gcx, 'tcx>, f: F)
4637 -> (BreakableCtxt<'gcx, 'tcx>, R) {
4640 let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
4641 index = enclosing_breakables.stack.len();
4642 enclosing_breakables.by_id.insert(id, index);
4643 enclosing_breakables.stack.push(ctxt);
4647 let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
4648 debug_assert!(enclosing_breakables.stack.len() == index + 1);
4649 enclosing_breakables.by_id.remove(&id).expect("missing breakable context");
4650 enclosing_breakables.stack.pop().expect("missing breakable context")
4656 pub fn check_bounds_are_used<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
4657 generics: &hir::Generics,
4659 debug!("check_bounds_are_used(n_tps={}, ty={:?})",
4660 generics.ty_params.len(), ty);
4662 // make a vector of booleans initially false, set to true when used
4663 if generics.ty_params.is_empty() { return; }
4664 let mut tps_used = vec![false; generics.ty_params.len()];
4666 for leaf_ty in ty.walk() {
4667 if let ty::TyParam(ParamTy {idx, ..}) = leaf_ty.sty {
4668 debug!("Found use of ty param num {}", idx);
4669 tps_used[idx as usize - generics.lifetimes.len()] = true;
4673 for (&used, param) in tps_used.iter().zip(&generics.ty_params) {
4675 struct_span_err!(tcx.sess, param.span, E0091,
4676 "type parameter `{}` is unused",
4678 .span_label(param.span, "unused type parameter")