1 // Copyright 2012-2015 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution and at
3 // http://rust-lang.org/COPYRIGHT.
5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8 // option. This file may not be copied, modified, or distributed
9 // except according to those terms.
15 Within the check phase of type check, we check each item one at a time
16 (bodies of function expressions are checked as part of the containing
17 function). Inference is used to supply types wherever they are
20 By far the most complex case is checking the body of a function. This
21 can be broken down into several distinct phases:
23 - gather: creates type variables to represent the type of each local
24 variable and pattern binding.
26 - main: the main pass does the lion's share of the work: it
27 determines the types of all expressions, resolves
28 methods, checks for most invalid conditions, and so forth. In
29 some cases, where a type is unknown, it may create a type or region
30 variable and use that as the type of an expression.
32 In the process of checking, various constraints will be placed on
33 these type variables through the subtyping relationships requested
34 through the `demand` module. The `infer` module is in charge
35 of resolving those constraints.
37 - regionck: after main is complete, the regionck pass goes over all
38 types looking for regions and making sure that they did not escape
39 into places they are not in scope. This may also influence the
40 final assignments of the various region variables if there is some
43 - vtable: find and records the impls to use for each trait bound that
44 appears on a type parameter.
46 - writeback: writes the final types within a function body, replacing
47 type variables with their final inferred types. These final types
48 are written into the `tcx.node_types` table, which should *never* contain
49 any reference to a type variable.
53 While type checking a function, the intermediate types for the
54 expressions, blocks, and so forth contained within the function are
55 stored in `fcx.node_types` and `fcx.node_substs`. These types
56 may contain unresolved type variables. After type checking is
57 complete, the functions in the writeback module are used to take the
58 types from this table, resolve them, and then write them into their
59 permanent home in the type context `tcx`.
61 This means that during inferencing you should use `fcx.write_ty()`
62 and `fcx.expr_ty()` / `fcx.node_ty()` to write/obtain the types of
63 nodes within the function.
65 The types of top-level items, which never contain unbound type
66 variables, are stored directly into the `tcx` tables.
68 n.b.: A type variable is not the same thing as a type parameter. A
69 type variable is rather an "instance" of a type parameter: that is,
70 given a generic function `fn foo<T>(t: T)`: while checking the
71 function `foo`, the type `ty_param(0)` refers to the type `T`, which
72 is treated in abstract. When `foo()` is called, however, `T` will be
73 substituted for a fresh type variable `N`. This variable will
74 eventually be resolved to some concrete type (which might itself be
79 pub use self::Expectation::*;
80 use self::autoderef::Autoderef;
81 use self::callee::DeferredCallResolution;
82 use self::coercion::{CoerceMany, DynamicCoerceMany};
83 pub use self::compare_method::{compare_impl_method, compare_const_impl};
84 use self::method::MethodCallee;
85 use self::TupleArgumentsFlag::*;
88 use fmt_macros::{Parser, Piece, Position};
89 use hir::def::{Def, CtorKind};
90 use hir::def_id::{CrateNum, DefId, LOCAL_CRATE};
91 use rustc_back::slice::ref_slice;
92 use rustc::infer::{self, InferCtxt, InferOk, RegionVariableOrigin};
93 use rustc::infer::type_variable::{TypeVariableOrigin};
94 use rustc::middle::region::CodeExtent;
95 use rustc::ty::subst::{Kind, Subst, Substs};
96 use rustc::traits::{self, FulfillmentContext, ObligationCause, ObligationCauseCode};
97 use rustc::ty::{ParamTy, LvaluePreference, NoPreference, PreferMutLvalue};
98 use rustc::ty::{self, Ty, TyCtxt, Visibility};
99 use rustc::ty::adjustment::{Adjust, Adjustment, AutoBorrow};
100 use rustc::ty::fold::{BottomUpFolder, TypeFoldable};
101 use rustc::ty::maps::Providers;
102 use rustc::ty::util::{Representability, IntTypeExt};
103 use errors::DiagnosticBuilder;
104 use require_c_abi_if_variadic;
105 use session::{Session, CompileResult};
108 use util::common::{ErrorReported, indenter};
109 use util::nodemap::{DefIdMap, FxHashMap, NodeMap};
111 use std::cell::{Cell, RefCell};
112 use std::collections::hash_map::Entry;
114 use std::mem::replace;
115 use std::ops::{self, Deref};
116 use syntax::abi::Abi;
118 use syntax::codemap::{self, original_sp, Spanned};
119 use syntax::feature_gate::{GateIssue, emit_feature_err};
121 use syntax::symbol::{Symbol, InternedString, keywords};
122 use syntax::util::lev_distance::find_best_match_for_name;
123 use syntax_pos::{self, BytePos, Span, DUMMY_SP};
125 use rustc::hir::intravisit::{self, Visitor, NestedVisitorMap};
126 use rustc::hir::itemlikevisit::ItemLikeVisitor;
127 use rustc::hir::{self, PatKind};
128 use rustc::middle::lang_items;
129 use rustc_back::slice;
130 use rustc::middle::const_val::eval_length;
131 use rustc_const_math::ConstInt;
150 /// closures defined within the function. For example:
153 /// bar(move|| { ... })
156 /// Here, the function `foo()` and the closure passed to
157 /// `bar()` will each have their own `FnCtxt`, but they will
158 /// share the inherited fields.
159 pub struct Inherited<'a, 'gcx: 'a+'tcx, 'tcx: 'a> {
160 infcx: InferCtxt<'a, 'gcx, 'tcx>,
162 locals: RefCell<NodeMap<Ty<'tcx>>>,
164 fulfillment_cx: RefCell<traits::FulfillmentContext<'tcx>>,
166 // When we process a call like `c()` where `c` is a closure type,
167 // we may not have decided yet whether `c` is a `Fn`, `FnMut`, or
168 // `FnOnce` closure. In that case, we defer full resolution of the
169 // call until upvar inference can kick in and make the
170 // decision. We keep these deferred resolutions grouped by the
171 // def-id of the closure, so that once we decide, we can easily go
172 // back and process them.
173 deferred_call_resolutions: RefCell<DefIdMap<Vec<DeferredCallResolution<'gcx, 'tcx>>>>,
175 deferred_cast_checks: RefCell<Vec<cast::CastCheck<'tcx>>>,
177 // Anonymized types found in explicit return types and their
178 // associated fresh inference variable. Writeback resolves these
179 // variables to get the concrete type, which can be used to
180 // deanonymize TyAnon, after typeck is done with all functions.
181 anon_types: RefCell<NodeMap<Ty<'tcx>>>,
183 /// Each type parameter has an implicit region bound that
184 /// indicates it must outlive at least the function body (the user
185 /// may specify stronger requirements). This field indicates the
186 /// region of the callee. If it is `None`, then the parameter
187 /// environment is for an item or something where the "callee" is
189 implicit_region_bound: Option<ty::Region<'tcx>>,
192 impl<'a, 'gcx, 'tcx> Deref for Inherited<'a, 'gcx, 'tcx> {
193 type Target = InferCtxt<'a, 'gcx, 'tcx>;
194 fn deref(&self) -> &Self::Target {
199 /// When type-checking an expression, we propagate downward
200 /// whatever type hint we are able in the form of an `Expectation`.
201 #[derive(Copy, Clone, Debug)]
202 pub enum Expectation<'tcx> {
203 /// We know nothing about what type this expression should have.
206 /// This expression should have the type given (or some subtype)
207 ExpectHasType(Ty<'tcx>),
209 /// This expression will be cast to the `Ty`
210 ExpectCastableToType(Ty<'tcx>),
212 /// This rvalue expression will be wrapped in `&` or `Box` and coerced
213 /// to `&Ty` or `Box<Ty>`, respectively. `Ty` is `[A]` or `Trait`.
214 ExpectRvalueLikeUnsized(Ty<'tcx>),
217 impl<'a, 'gcx, 'tcx> Expectation<'tcx> {
218 // Disregard "castable to" expectations because they
219 // can lead us astray. Consider for example `if cond
220 // {22} else {c} as u8` -- if we propagate the
221 // "castable to u8" constraint to 22, it will pick the
222 // type 22u8, which is overly constrained (c might not
223 // be a u8). In effect, the problem is that the
224 // "castable to" expectation is not the tightest thing
225 // we can say, so we want to drop it in this case.
226 // The tightest thing we can say is "must unify with
227 // else branch". Note that in the case of a "has type"
228 // constraint, this limitation does not hold.
230 // If the expected type is just a type variable, then don't use
231 // an expected type. Otherwise, we might write parts of the type
232 // when checking the 'then' block which are incompatible with the
234 fn adjust_for_branches(&self, fcx: &FnCtxt<'a, 'gcx, 'tcx>) -> Expectation<'tcx> {
236 ExpectHasType(ety) => {
237 let ety = fcx.shallow_resolve(ety);
238 if !ety.is_ty_var() {
244 ExpectRvalueLikeUnsized(ety) => {
245 ExpectRvalueLikeUnsized(ety)
251 /// Provide an expectation for an rvalue expression given an *optional*
252 /// hint, which is not required for type safety (the resulting type might
253 /// be checked higher up, as is the case with `&expr` and `box expr`), but
254 /// is useful in determining the concrete type.
256 /// The primary use case is where the expected type is a fat pointer,
257 /// like `&[isize]`. For example, consider the following statement:
259 /// let x: &[isize] = &[1, 2, 3];
261 /// In this case, the expected type for the `&[1, 2, 3]` expression is
262 /// `&[isize]`. If however we were to say that `[1, 2, 3]` has the
263 /// expectation `ExpectHasType([isize])`, that would be too strong --
264 /// `[1, 2, 3]` does not have the type `[isize]` but rather `[isize; 3]`.
265 /// It is only the `&[1, 2, 3]` expression as a whole that can be coerced
266 /// to the type `&[isize]`. Therefore, we propagate this more limited hint,
267 /// which still is useful, because it informs integer literals and the like.
268 /// See the test case `test/run-pass/coerce-expect-unsized.rs` and #20169
269 /// for examples of where this comes up,.
270 fn rvalue_hint(fcx: &FnCtxt<'a, 'gcx, 'tcx>, ty: Ty<'tcx>) -> Expectation<'tcx> {
271 match fcx.tcx.struct_tail(ty).sty {
272 ty::TySlice(_) | ty::TyStr | ty::TyDynamic(..) => {
273 ExpectRvalueLikeUnsized(ty)
275 _ => ExpectHasType(ty)
279 // Resolves `expected` by a single level if it is a variable. If
280 // there is no expected type or resolution is not possible (e.g.,
281 // no constraints yet present), just returns `None`.
282 fn resolve(self, fcx: &FnCtxt<'a, 'gcx, 'tcx>) -> Expectation<'tcx> {
287 ExpectCastableToType(t) => {
288 ExpectCastableToType(fcx.resolve_type_vars_if_possible(&t))
290 ExpectHasType(t) => {
291 ExpectHasType(fcx.resolve_type_vars_if_possible(&t))
293 ExpectRvalueLikeUnsized(t) => {
294 ExpectRvalueLikeUnsized(fcx.resolve_type_vars_if_possible(&t))
299 fn to_option(self, fcx: &FnCtxt<'a, 'gcx, 'tcx>) -> Option<Ty<'tcx>> {
300 match self.resolve(fcx) {
301 NoExpectation => None,
302 ExpectCastableToType(ty) |
304 ExpectRvalueLikeUnsized(ty) => Some(ty),
308 /// It sometimes happens that we want to turn an expectation into
309 /// a **hard constraint** (i.e., something that must be satisfied
310 /// for the program to type-check). `only_has_type` will return
311 /// such a constraint, if it exists.
312 fn only_has_type(self, fcx: &FnCtxt<'a, 'gcx, 'tcx>) -> Option<Ty<'tcx>> {
313 match self.resolve(fcx) {
314 ExpectHasType(ty) => Some(ty),
319 /// Like `only_has_type`, but instead of returning `None` if no
320 /// hard constraint exists, creates a fresh type variable.
321 fn coercion_target_type(self, fcx: &FnCtxt<'a, 'gcx, 'tcx>, span: Span) -> Ty<'tcx> {
322 self.only_has_type(fcx)
323 .unwrap_or_else(|| fcx.next_ty_var(TypeVariableOrigin::MiscVariable(span)))
327 #[derive(Copy, Clone)]
328 pub struct UnsafetyState {
329 pub def: ast::NodeId,
330 pub unsafety: hir::Unsafety,
331 pub unsafe_push_count: u32,
336 pub fn function(unsafety: hir::Unsafety, def: ast::NodeId) -> UnsafetyState {
337 UnsafetyState { def: def, unsafety: unsafety, unsafe_push_count: 0, from_fn: true }
340 pub fn recurse(&mut self, blk: &hir::Block) -> UnsafetyState {
341 match self.unsafety {
342 // If this unsafe, then if the outer function was already marked as
343 // unsafe we shouldn't attribute the unsafe'ness to the block. This
344 // way the block can be warned about instead of ignoring this
345 // extraneous block (functions are never warned about).
346 hir::Unsafety::Unsafe if self.from_fn => *self,
349 let (unsafety, def, count) = match blk.rules {
350 hir::PushUnsafeBlock(..) =>
351 (unsafety, blk.id, self.unsafe_push_count.checked_add(1).unwrap()),
352 hir::PopUnsafeBlock(..) =>
353 (unsafety, blk.id, self.unsafe_push_count.checked_sub(1).unwrap()),
354 hir::UnsafeBlock(..) =>
355 (hir::Unsafety::Unsafe, blk.id, self.unsafe_push_count),
357 (unsafety, self.def, self.unsafe_push_count),
359 UnsafetyState{ def: def,
361 unsafe_push_count: count,
368 #[derive(Debug, Copy, Clone)]
374 /// Tracks whether executing a node may exit normally (versus
375 /// return/break/panic, which "diverge", leaving dead code in their
376 /// wake). Tracked semi-automatically (through type variables marked
377 /// as diverging), with some manual adjustments for control-flow
378 /// primitives (approximating a CFG).
379 #[derive(Copy, Clone, Debug, PartialEq, Eq, PartialOrd, Ord)]
381 /// Potentially unknown, some cases converge,
382 /// others require a CFG to determine them.
385 /// Definitely known to diverge and therefore
386 /// not reach the next sibling or its parent.
389 /// Same as `Always` but with a reachability
390 /// warning already emitted
394 // Convenience impls for combinig `Diverges`.
396 impl ops::BitAnd for Diverges {
398 fn bitand(self, other: Self) -> Self {
399 cmp::min(self, other)
403 impl ops::BitOr for Diverges {
405 fn bitor(self, other: Self) -> Self {
406 cmp::max(self, other)
410 impl ops::BitAndAssign for Diverges {
411 fn bitand_assign(&mut self, other: Self) {
412 *self = *self & other;
416 impl ops::BitOrAssign for Diverges {
417 fn bitor_assign(&mut self, other: Self) {
418 *self = *self | other;
423 fn always(self) -> bool {
424 self >= Diverges::Always
428 pub struct BreakableCtxt<'gcx: 'tcx, 'tcx> {
431 // this is `null` for loops where break with a value is illegal,
432 // such as `while`, `for`, and `while let`
433 coerce: Option<DynamicCoerceMany<'gcx, 'tcx>>,
436 pub struct EnclosingBreakables<'gcx: 'tcx, 'tcx> {
437 stack: Vec<BreakableCtxt<'gcx, 'tcx>>,
438 by_id: NodeMap<usize>,
441 impl<'gcx, 'tcx> EnclosingBreakables<'gcx, 'tcx> {
442 fn find_breakable(&mut self, target_id: ast::NodeId) -> &mut BreakableCtxt<'gcx, 'tcx> {
443 let ix = *self.by_id.get(&target_id).unwrap_or_else(|| {
444 bug!("could not find enclosing breakable with id {}", target_id);
450 pub struct FnCtxt<'a, 'gcx: 'a+'tcx, 'tcx: 'a> {
451 body_id: ast::NodeId,
453 /// The parameter environment used for proving trait obligations
454 /// in this function. This can change when we descend into
455 /// closures (as they bring new things into scope), hence it is
456 /// not part of `Inherited` (as of the time of this writing,
457 /// closures do not yet change the environment, but they will
459 param_env: ty::ParamEnv<'tcx>,
461 // Number of errors that had been reported when we started
462 // checking this function. On exit, if we find that *more* errors
463 // have been reported, we will skip regionck and other work that
464 // expects the types within the function to be consistent.
465 err_count_on_creation: usize,
467 ret_coercion: Option<RefCell<DynamicCoerceMany<'gcx, 'tcx>>>,
469 ps: RefCell<UnsafetyState>,
471 /// Whether the last checked node generates a divergence (e.g.,
472 /// `return` will set this to Always). In general, when entering
473 /// an expression or other node in the tree, the initial value
474 /// indicates whether prior parts of the containing expression may
475 /// have diverged. It is then typically set to `Maybe` (and the
476 /// old value remembered) for processing the subparts of the
477 /// current expression. As each subpart is processed, they may set
478 /// the flag to `Always` etc. Finally, at the end, we take the
479 /// result and "union" it with the original value, so that when we
480 /// return the flag indicates if any subpart of the the parent
481 /// expression (up to and including this part) has diverged. So,
482 /// if you read it after evaluating a subexpression `X`, the value
483 /// you get indicates whether any subexpression that was
484 /// evaluating up to and including `X` diverged.
486 /// We use this flag for two purposes:
488 /// - To warn about unreachable code: if, after processing a
489 /// sub-expression but before we have applied the effects of the
490 /// current node, we see that the flag is set to `Always`, we
491 /// can issue a warning. This corresponds to something like
492 /// `foo(return)`; we warn on the `foo()` expression. (We then
493 /// update the flag to `WarnedAlways` to suppress duplicate
494 /// reports.) Similarly, if we traverse to a fresh statement (or
495 /// tail expression) from a `Always` setting, we will isssue a
496 /// warning. This corresponds to something like `{return;
497 /// foo();}` or `{return; 22}`, where we would warn on the
500 /// - To permit assignment into a local variable or other lvalue
501 /// (including the "return slot") of type `!`. This is allowed
502 /// if **either** the type of value being assigned is `!`, which
503 /// means the current code is dead, **or** the expression's
504 /// divering flag is true, which means that a divering value was
505 /// wrapped (e.g., `let x: ! = foo(return)`).
507 /// To repeat the last point: an expression represents dead-code
508 /// if, after checking it, **either** its type is `!` OR the
509 /// diverges flag is set to something other than `Maybe`.
510 diverges: Cell<Diverges>,
512 /// Whether any child nodes have any type errors.
513 has_errors: Cell<bool>,
515 enclosing_breakables: RefCell<EnclosingBreakables<'gcx, 'tcx>>,
517 inh: &'a Inherited<'a, 'gcx, 'tcx>,
520 impl<'a, 'gcx, 'tcx> Deref for FnCtxt<'a, 'gcx, 'tcx> {
521 type Target = Inherited<'a, 'gcx, 'tcx>;
522 fn deref(&self) -> &Self::Target {
527 /// Helper type of a temporary returned by Inherited::build(...).
528 /// Necessary because we can't write the following bound:
529 /// F: for<'b, 'tcx> where 'gcx: 'tcx FnOnce(Inherited<'b, 'gcx, 'tcx>).
530 pub struct InheritedBuilder<'a, 'gcx: 'a+'tcx, 'tcx: 'a> {
531 infcx: infer::InferCtxtBuilder<'a, 'gcx, 'tcx>,
535 impl<'a, 'gcx, 'tcx> Inherited<'a, 'gcx, 'tcx> {
536 pub fn build(tcx: TyCtxt<'a, 'gcx, 'gcx>, def_id: DefId)
537 -> InheritedBuilder<'a, 'gcx, 'tcx> {
538 let tables = ty::TypeckTables::empty();
540 infcx: tcx.infer_ctxt(tables),
546 impl<'a, 'gcx, 'tcx> InheritedBuilder<'a, 'gcx, 'tcx> {
547 fn enter<F, R>(&'tcx mut self, f: F) -> R
548 where F: for<'b> FnOnce(Inherited<'b, 'gcx, 'tcx>) -> R
550 let def_id = self.def_id;
551 self.infcx.enter(|infcx| f(Inherited::new(infcx, def_id)))
555 impl<'a, 'gcx, 'tcx> Inherited<'a, 'gcx, 'tcx> {
556 fn new(infcx: InferCtxt<'a, 'gcx, 'tcx>, def_id: DefId) -> Self {
558 let item_id = tcx.hir.as_local_node_id(def_id);
559 let body_id = item_id.and_then(|id| tcx.hir.maybe_body_owned_by(id));
560 let implicit_region_bound = body_id.map(|body| {
561 tcx.mk_region(ty::ReScope(CodeExtent::CallSiteScope(body)))
566 fulfillment_cx: RefCell::new(traits::FulfillmentContext::new()),
567 locals: RefCell::new(NodeMap()),
568 deferred_call_resolutions: RefCell::new(DefIdMap()),
569 deferred_cast_checks: RefCell::new(Vec::new()),
570 anon_types: RefCell::new(NodeMap()),
571 implicit_region_bound,
575 fn register_predicate(&self, obligation: traits::PredicateObligation<'tcx>) {
576 debug!("register_predicate({:?})", obligation);
577 if obligation.has_escaping_regions() {
578 span_bug!(obligation.cause.span, "escaping regions in predicate {:?}",
583 .register_predicate_obligation(self, obligation);
586 fn register_predicates(&self, obligations: Vec<traits::PredicateObligation<'tcx>>) {
587 for obligation in obligations {
588 self.register_predicate(obligation);
592 fn register_infer_ok_obligations<T>(&self, infer_ok: InferOk<'tcx, T>) -> T {
593 self.register_predicates(infer_ok.obligations);
597 fn normalize_associated_types_in<T>(&self,
599 body_id: ast::NodeId,
600 param_env: ty::ParamEnv<'tcx>,
602 where T : TypeFoldable<'tcx>
604 let ok = self.normalize_associated_types_in_as_infer_ok(span, body_id, param_env, value);
605 self.register_infer_ok_obligations(ok)
608 fn normalize_associated_types_in_as_infer_ok<T>(&self,
610 body_id: ast::NodeId,
611 param_env: ty::ParamEnv<'tcx>,
614 where T : TypeFoldable<'tcx>
616 debug!("normalize_associated_types_in(value={:?})", value);
617 let mut selcx = traits::SelectionContext::new(self);
618 let cause = ObligationCause::misc(span, body_id);
619 let traits::Normalized { value, obligations } =
620 traits::normalize(&mut selcx, param_env, cause, value);
621 debug!("normalize_associated_types_in: result={:?} predicates={:?}",
624 InferOk { value, obligations }
627 /// Replace any late-bound regions bound in `value` with
628 /// free variants attached to `all_outlive_scope`.
629 fn liberate_late_bound_regions<T>(&self,
630 all_outlive_scope: DefId,
631 value: &ty::Binder<T>)
633 where T: TypeFoldable<'tcx>
635 self.tcx.replace_late_bound_regions(value, |br| {
636 self.tcx.mk_region(ty::ReFree(ty::FreeRegion {
637 scope: all_outlive_scope,
644 struct CheckItemTypesVisitor<'a, 'tcx: 'a> { tcx: TyCtxt<'a, 'tcx, 'tcx> }
646 impl<'a, 'tcx> ItemLikeVisitor<'tcx> for CheckItemTypesVisitor<'a, 'tcx> {
647 fn visit_item(&mut self, i: &'tcx hir::Item) {
648 check_item_type(self.tcx, i);
650 fn visit_trait_item(&mut self, _: &'tcx hir::TraitItem) { }
651 fn visit_impl_item(&mut self, _: &'tcx hir::ImplItem) { }
654 pub fn check_wf_new<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>) -> CompileResult {
655 tcx.sess.track_errors(|| {
656 let mut visit = wfcheck::CheckTypeWellFormedVisitor::new(tcx);
657 tcx.hir.krate().visit_all_item_likes(&mut visit.as_deep_visitor());
661 pub fn check_item_types<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>) -> CompileResult {
662 tcx.sess.track_errors(|| {
663 tcx.hir.krate().visit_all_item_likes(&mut CheckItemTypesVisitor { tcx });
667 pub fn check_item_bodies<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>) -> CompileResult {
668 tcx.typeck_item_bodies(LOCAL_CRATE)
671 fn typeck_item_bodies<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, crate_num: CrateNum) -> CompileResult {
672 debug_assert!(crate_num == LOCAL_CRATE);
673 tcx.sess.track_errors(|| {
674 for body_owner_def_id in tcx.body_owners() {
675 tcx.typeck_tables_of(body_owner_def_id);
680 pub fn provide(providers: &mut Providers) {
681 *providers = Providers {
692 fn closure_type<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
694 -> ty::PolyFnSig<'tcx> {
695 let node_id = tcx.hir.as_local_node_id(def_id).unwrap();
696 tcx.typeck_tables_of(def_id).closure_tys[&node_id]
699 fn closure_kind<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
702 let node_id = tcx.hir.as_local_node_id(def_id).unwrap();
703 tcx.typeck_tables_of(def_id).closure_kinds[&node_id].0
706 fn adt_destructor<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
708 -> Option<ty::Destructor> {
709 tcx.calculate_dtor(def_id, &mut dropck::check_drop_impl)
712 /// If this def-id is a "primary tables entry", returns `Some((body_id, decl))`
713 /// with information about it's body-id and fn-decl (if any). Otherwise,
716 /// If this function returns "some", then `typeck_tables(def_id)` will
717 /// succeed; if it returns `None`, then `typeck_tables(def_id)` may or
718 /// may not succeed. In some cases where this function returns `None`
719 /// (notably closures), `typeck_tables(def_id)` would wind up
720 /// redirecting to the owning function.
721 fn primary_body_of<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
723 -> Option<(hir::BodyId, Option<&'tcx hir::FnDecl>)>
725 match tcx.hir.get(id) {
726 hir::map::NodeItem(item) => {
728 hir::ItemConst(_, body) |
729 hir::ItemStatic(_, _, body) =>
731 hir::ItemFn(ref decl, .., body) =>
732 Some((body, Some(decl))),
737 hir::map::NodeTraitItem(item) => {
739 hir::TraitItemKind::Const(_, Some(body)) =>
741 hir::TraitItemKind::Method(ref sig, hir::TraitMethod::Provided(body)) =>
742 Some((body, Some(&sig.decl))),
747 hir::map::NodeImplItem(item) => {
749 hir::ImplItemKind::Const(_, body) =>
751 hir::ImplItemKind::Method(ref sig, body) =>
752 Some((body, Some(&sig.decl))),
757 hir::map::NodeExpr(expr) => {
758 // FIXME(eddyb) Closures should have separate
759 // function definition IDs and expression IDs.
760 // Type-checking should not let closures get
761 // this far in a constant position.
762 // Assume that everything other than closures
763 // is a constant "initializer" expression.
765 hir::ExprClosure(..) =>
768 Some((hir::BodyId { node_id: expr.id }, None)),
775 fn has_typeck_tables<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
778 // Closures' tables come from their outermost function,
779 // as they are part of the same "inference environment".
780 let outer_def_id = tcx.closure_base_def_id(def_id);
781 if outer_def_id != def_id {
782 return tcx.has_typeck_tables(outer_def_id);
785 let id = tcx.hir.as_local_node_id(def_id).unwrap();
786 primary_body_of(tcx, id).is_some()
789 fn typeck_tables_of<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
791 -> &'tcx ty::TypeckTables<'tcx> {
792 // Closures' tables come from their outermost function,
793 // as they are part of the same "inference environment".
794 let outer_def_id = tcx.closure_base_def_id(def_id);
795 if outer_def_id != def_id {
796 return tcx.typeck_tables_of(outer_def_id);
799 let id = tcx.hir.as_local_node_id(def_id).unwrap();
800 let span = tcx.hir.span(id);
802 // Figure out what primary body this item has.
803 let (body_id, fn_decl) = primary_body_of(tcx, id).unwrap_or_else(|| {
804 span_bug!(span, "can't type-check body of {:?}", def_id);
806 let body = tcx.hir.body(body_id);
808 Inherited::build(tcx, def_id).enter(|inh| {
809 let param_env = tcx.param_env(def_id);
810 let fcx = if let Some(decl) = fn_decl {
811 let fn_sig = tcx.type_of(def_id).fn_sig();
813 check_abi(tcx, span, fn_sig.abi());
815 // Compute the fty from point of view of inside fn.
817 inh.liberate_late_bound_regions(def_id, &fn_sig);
819 inh.normalize_associated_types_in(body.value.span,
824 check_fn(&inh, param_env, fn_sig, decl, id, body)
826 let fcx = FnCtxt::new(&inh, param_env, body.value.id);
827 let expected_type = tcx.type_of(def_id);
828 let expected_type = fcx.normalize_associated_types_in(body.value.span, &expected_type);
829 fcx.require_type_is_sized(expected_type, body.value.span, traits::ConstSized);
831 // Gather locals in statics (because of block expressions).
832 // This is technically unnecessary because locals in static items are forbidden,
833 // but prevents type checking from blowing up before const checking can properly
835 GatherLocalsVisitor { fcx: &fcx }.visit_body(body);
837 fcx.check_expr_coercable_to_type(&body.value, expected_type);
842 fcx.select_all_obligations_and_apply_defaults();
843 fcx.closure_analyze(body);
844 fcx.select_obligations_where_possible();
846 fcx.select_all_obligations_or_error();
848 if fn_decl.is_some() {
849 fcx.regionck_fn(id, body);
851 fcx.regionck_expr(body);
854 fcx.resolve_type_vars_in_body(body)
858 fn check_abi<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, span: Span, abi: Abi) {
859 if !tcx.sess.target.target.is_abi_supported(abi) {
860 struct_span_err!(tcx.sess, span, E0570,
861 "The ABI `{}` is not supported for the current target", abi).emit()
865 struct GatherLocalsVisitor<'a, 'gcx: 'a+'tcx, 'tcx: 'a> {
866 fcx: &'a FnCtxt<'a, 'gcx, 'tcx>
869 impl<'a, 'gcx, 'tcx> GatherLocalsVisitor<'a, 'gcx, 'tcx> {
870 fn assign(&mut self, span: Span, nid: ast::NodeId, ty_opt: Option<Ty<'tcx>>) -> Ty<'tcx> {
873 // infer the variable's type
874 let var_ty = self.fcx.next_ty_var(TypeVariableOrigin::TypeInference(span));
875 self.fcx.locals.borrow_mut().insert(nid, var_ty);
879 // take type that the user specified
880 self.fcx.locals.borrow_mut().insert(nid, typ);
887 impl<'a, 'gcx, 'tcx> Visitor<'gcx> for GatherLocalsVisitor<'a, 'gcx, 'tcx> {
888 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'gcx> {
889 NestedVisitorMap::None
892 // Add explicitly-declared locals.
893 fn visit_local(&mut self, local: &'gcx hir::Local) {
894 let o_ty = match local.ty {
895 Some(ref ty) => Some(self.fcx.to_ty(&ty)),
898 self.assign(local.span, local.id, o_ty);
899 debug!("Local variable {:?} is assigned type {}",
901 self.fcx.ty_to_string(
902 self.fcx.locals.borrow().get(&local.id).unwrap().clone()));
903 intravisit::walk_local(self, local);
906 // Add pattern bindings.
907 fn visit_pat(&mut self, p: &'gcx hir::Pat) {
908 if let PatKind::Binding(_, _, ref path1, _) = p.node {
909 let var_ty = self.assign(p.span, p.id, None);
911 self.fcx.require_type_is_sized(var_ty, p.span,
912 traits::VariableType(p.id));
914 debug!("Pattern binding {} is assigned to {} with type {:?}",
916 self.fcx.ty_to_string(
917 self.fcx.locals.borrow().get(&p.id).unwrap().clone()),
920 intravisit::walk_pat(self, p);
923 // Don't descend into the bodies of nested closures
924 fn visit_fn(&mut self, _: intravisit::FnKind<'gcx>, _: &'gcx hir::FnDecl,
925 _: hir::BodyId, _: Span, _: ast::NodeId) { }
928 /// Helper used for fns and closures. Does the grungy work of checking a function
929 /// body and returns the function context used for that purpose, since in the case of a fn item
930 /// there is still a bit more to do.
933 /// * inherited: other fields inherited from the enclosing fn (if any)
934 fn check_fn<'a, 'gcx, 'tcx>(inherited: &'a Inherited<'a, 'gcx, 'tcx>,
935 param_env: ty::ParamEnv<'tcx>,
936 fn_sig: ty::FnSig<'tcx>,
937 decl: &'gcx hir::FnDecl,
939 body: &'gcx hir::Body)
940 -> FnCtxt<'a, 'gcx, 'tcx>
942 let mut fn_sig = fn_sig.clone();
944 debug!("check_fn(sig={:?}, fn_id={}, param_env={:?})", fn_sig, fn_id, param_env);
946 // Create the function context. This is either derived from scratch or,
947 // in the case of function expressions, based on the outer context.
948 let mut fcx = FnCtxt::new(inherited, param_env, body.value.id);
949 *fcx.ps.borrow_mut() = UnsafetyState::function(fn_sig.unsafety, fn_id);
951 let ret_ty = fn_sig.output();
952 fcx.require_type_is_sized(ret_ty, decl.output.span(), traits::ReturnType);
953 let ret_ty = fcx.instantiate_anon_types(&ret_ty);
954 fcx.ret_coercion = Some(RefCell::new(CoerceMany::new(ret_ty)));
955 fn_sig = fcx.tcx.mk_fn_sig(
956 fn_sig.inputs().iter().cloned(),
963 GatherLocalsVisitor { fcx: &fcx, }.visit_body(body);
965 // Add formal parameters.
966 for (arg_ty, arg) in fn_sig.inputs().iter().zip(&body.arguments) {
967 // The type of the argument must be well-formed.
969 // NB -- this is now checked in wfcheck, but that
970 // currently only results in warnings, so we issue an
971 // old-style WF obligation here so that we still get the
972 // errors that we used to get.
973 fcx.register_old_wf_obligation(arg_ty, arg.pat.span, traits::MiscObligation);
975 // Check the pattern.
976 fcx.check_pat_arg(&arg.pat, arg_ty, true);
977 fcx.write_ty(arg.id, arg_ty);
980 inherited.tables.borrow_mut().liberated_fn_sigs.insert(fn_id, fn_sig);
982 fcx.check_return_expr(&body.value);
984 // Finalize the return check by taking the LUB of the return types
985 // we saw and assigning it to the expected return type. This isn't
986 // really expected to fail, since the coercions would have failed
987 // earlier when trying to find a LUB.
989 // However, the behavior around `!` is sort of complex. In the
990 // event that the `actual_return_ty` comes back as `!`, that
991 // indicates that the fn either does not return or "returns" only
992 // values of type `!`. In this case, if there is an expected
993 // return type that is *not* `!`, that should be ok. But if the
994 // return type is being inferred, we want to "fallback" to `!`:
996 // let x = move || panic!();
998 // To allow for that, I am creating a type variable with diverging
999 // fallback. This was deemed ever so slightly better than unifying
1000 // the return value with `!` because it allows for the caller to
1001 // make more assumptions about the return type (e.g., they could do
1003 // let y: Option<u32> = Some(x());
1005 // which would then cause this return type to become `u32`, not
1007 let coercion = fcx.ret_coercion.take().unwrap().into_inner();
1008 let mut actual_return_ty = coercion.complete(&fcx);
1009 if actual_return_ty.is_never() {
1010 actual_return_ty = fcx.next_diverging_ty_var(
1011 TypeVariableOrigin::DivergingFn(body.value.span));
1013 fcx.demand_suptype(body.value.span, ret_ty, actual_return_ty);
1018 fn check_struct<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
1021 let def_id = tcx.hir.local_def_id(id);
1022 let def = tcx.adt_def(def_id);
1023 def.destructor(tcx); // force the destructor to be evaluated
1024 check_representable(tcx, span, def_id);
1026 if def.repr.simd() {
1027 check_simd(tcx, span, def_id);
1030 // if struct is packed and not aligned, check fields for alignment.
1031 // Checks for combining packed and align attrs on single struct are done elsewhere.
1032 if tcx.adt_def(def_id).repr.packed() && tcx.adt_def(def_id).repr.align == 0 {
1033 check_packed(tcx, span, def_id);
1037 fn check_union<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
1040 let def_id = tcx.hir.local_def_id(id);
1041 let def = tcx.adt_def(def_id);
1042 def.destructor(tcx); // force the destructor to be evaluated
1043 check_representable(tcx, span, def_id);
1046 pub fn check_item_type<'a,'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, it: &'tcx hir::Item) {
1047 debug!("check_item_type(it.id={}, it.name={})",
1049 tcx.item_path_str(tcx.hir.local_def_id(it.id)));
1050 let _indenter = indenter();
1052 // Consts can play a role in type-checking, so they are included here.
1053 hir::ItemStatic(..) |
1054 hir::ItemConst(..) => {
1055 tcx.typeck_tables_of(tcx.hir.local_def_id(it.id));
1057 hir::ItemEnum(ref enum_definition, _) => {
1060 &enum_definition.variants,
1063 hir::ItemFn(..) => {} // entirely within check_item_body
1064 hir::ItemImpl(.., ref impl_item_refs) => {
1065 debug!("ItemImpl {} with id {}", it.name, it.id);
1066 let impl_def_id = tcx.hir.local_def_id(it.id);
1067 if let Some(impl_trait_ref) = tcx.impl_trait_ref(impl_def_id) {
1068 check_impl_items_against_trait(tcx,
1073 let trait_def_id = impl_trait_ref.def_id;
1074 check_on_unimplemented(tcx, trait_def_id, it);
1077 hir::ItemTrait(..) => {
1078 let def_id = tcx.hir.local_def_id(it.id);
1079 check_on_unimplemented(tcx, def_id, it);
1081 hir::ItemStruct(..) => {
1082 check_struct(tcx, it.id, it.span);
1084 hir::ItemUnion(..) => {
1085 check_union(tcx, it.id, it.span);
1087 hir::ItemTy(_, ref generics) => {
1088 let def_id = tcx.hir.local_def_id(it.id);
1089 let pty_ty = tcx.type_of(def_id);
1090 check_bounds_are_used(tcx, generics, pty_ty);
1092 hir::ItemForeignMod(ref m) => {
1093 check_abi(tcx, it.span, m.abi);
1095 if m.abi == Abi::RustIntrinsic {
1096 for item in &m.items {
1097 intrinsic::check_intrinsic_type(tcx, item);
1099 } else if m.abi == Abi::PlatformIntrinsic {
1100 for item in &m.items {
1101 intrinsic::check_platform_intrinsic_type(tcx, item);
1104 for item in &m.items {
1105 let generics = tcx.generics_of(tcx.hir.local_def_id(item.id));
1106 if !generics.types.is_empty() {
1107 let mut err = struct_span_err!(tcx.sess, item.span, E0044,
1108 "foreign items may not have type parameters");
1109 span_help!(&mut err, item.span,
1110 "consider using specialization instead of \
1115 if let hir::ForeignItemFn(ref fn_decl, _, _) = item.node {
1116 require_c_abi_if_variadic(tcx, fn_decl, m.abi, item.span);
1121 _ => {/* nothing to do */ }
1125 fn check_on_unimplemented<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
1128 let generics = tcx.generics_of(def_id);
1129 if let Some(ref attr) = item.attrs.iter().find(|a| {
1130 a.check_name("rustc_on_unimplemented")
1132 if let Some(istring) = attr.value_str() {
1133 let istring = istring.as_str();
1134 let parser = Parser::new(&istring);
1135 let types = &generics.types;
1136 for token in parser {
1138 Piece::String(_) => (), // Normal string, no need to check it
1139 Piece::NextArgument(a) => match a.position {
1140 // `{Self}` is allowed
1141 Position::ArgumentNamed(s) if s == "Self" => (),
1142 // So is `{A}` if A is a type parameter
1143 Position::ArgumentNamed(s) => match types.iter().find(|t| {
1148 let name = tcx.item_name(def_id);
1149 span_err!(tcx.sess, attr.span, E0230,
1150 "there is no type parameter \
1155 // `{:1}` and `{}` are not to be used
1156 Position::ArgumentIs(_) => {
1157 span_err!(tcx.sess, attr.span, E0231,
1158 "only named substitution \
1159 parameters are allowed");
1166 tcx.sess, attr.span, E0232,
1167 "this attribute must have a value")
1168 .span_label(attr.span, "attribute requires a value")
1169 .note(&format!("eg `#[rustc_on_unimplemented = \"foo\"]`"))
1175 fn report_forbidden_specialization<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
1176 impl_item: &hir::ImplItem,
1179 let mut err = struct_span_err!(
1180 tcx.sess, impl_item.span, E0520,
1181 "`{}` specializes an item from a parent `impl`, but \
1182 that item is not marked `default`",
1184 err.span_label(impl_item.span, format!("cannot specialize default item `{}`",
1187 match tcx.span_of_impl(parent_impl) {
1189 err.span_label(span, "parent `impl` is here");
1190 err.note(&format!("to specialize, `{}` in the parent `impl` must be marked `default`",
1194 err.note(&format!("parent implementation is in crate `{}`", cname));
1201 fn check_specialization_validity<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
1202 trait_def: &ty::TraitDef,
1204 impl_item: &hir::ImplItem)
1206 let ancestors = trait_def.ancestors(tcx, impl_id);
1208 let kind = match impl_item.node {
1209 hir::ImplItemKind::Const(..) => ty::AssociatedKind::Const,
1210 hir::ImplItemKind::Method(..) => ty::AssociatedKind::Method,
1211 hir::ImplItemKind::Type(_) => ty::AssociatedKind::Type
1213 let parent = ancestors.defs(tcx, impl_item.name, kind).skip(1).next()
1214 .map(|node_item| node_item.map(|parent| parent.defaultness));
1216 if let Some(parent) = parent {
1217 if tcx.impl_item_is_final(&parent) {
1218 report_forbidden_specialization(tcx, impl_item, parent.node.def_id());
1224 fn check_impl_items_against_trait<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
1227 impl_trait_ref: ty::TraitRef<'tcx>,
1228 impl_item_refs: &[hir::ImplItemRef]) {
1229 // If the trait reference itself is erroneous (so the compilation is going
1230 // to fail), skip checking the items here -- the `impl_item` table in `tcx`
1231 // isn't populated for such impls.
1232 if impl_trait_ref.references_error() { return; }
1234 // Locate trait definition and items
1235 let trait_def = tcx.trait_def(impl_trait_ref.def_id);
1236 let mut overridden_associated_type = None;
1238 let impl_items = || impl_item_refs.iter().map(|iiref| tcx.hir.impl_item(iiref.id));
1240 // Check existing impl methods to see if they are both present in trait
1241 // and compatible with trait signature
1242 for impl_item in impl_items() {
1243 let ty_impl_item = tcx.associated_item(tcx.hir.local_def_id(impl_item.id));
1244 let ty_trait_item = tcx.associated_items(impl_trait_ref.def_id)
1245 .find(|ac| ac.name == ty_impl_item.name);
1247 // Check that impl definition matches trait definition
1248 if let Some(ty_trait_item) = ty_trait_item {
1249 match impl_item.node {
1250 hir::ImplItemKind::Const(..) => {
1251 // Find associated const definition.
1252 if ty_trait_item.kind == ty::AssociatedKind::Const {
1253 compare_const_impl(tcx,
1259 let mut err = struct_span_err!(tcx.sess, impl_item.span, E0323,
1260 "item `{}` is an associated const, \
1261 which doesn't match its trait `{}`",
1264 err.span_label(impl_item.span, "does not match trait");
1265 // We can only get the spans from local trait definition
1266 // Same for E0324 and E0325
1267 if let Some(trait_span) = tcx.hir.span_if_local(ty_trait_item.def_id) {
1268 err.span_label(trait_span, "item in trait");
1273 hir::ImplItemKind::Method(..) => {
1274 let trait_span = tcx.hir.span_if_local(ty_trait_item.def_id);
1275 if ty_trait_item.kind == ty::AssociatedKind::Method {
1276 let err_count = tcx.sess.err_count();
1277 compare_impl_method(tcx,
1283 true); // start with old-broken-mode
1284 if err_count == tcx.sess.err_count() {
1285 // old broken mode did not report an error. Try with the new mode.
1286 compare_impl_method(tcx,
1292 false); // use the new mode
1295 let mut err = struct_span_err!(tcx.sess, impl_item.span, E0324,
1296 "item `{}` is an associated method, \
1297 which doesn't match its trait `{}`",
1300 err.span_label(impl_item.span, "does not match trait");
1301 if let Some(trait_span) = tcx.hir.span_if_local(ty_trait_item.def_id) {
1302 err.span_label(trait_span, "item in trait");
1307 hir::ImplItemKind::Type(_) => {
1308 if ty_trait_item.kind == ty::AssociatedKind::Type {
1309 if ty_trait_item.defaultness.has_value() {
1310 overridden_associated_type = Some(impl_item);
1313 let mut err = struct_span_err!(tcx.sess, impl_item.span, E0325,
1314 "item `{}` is an associated type, \
1315 which doesn't match its trait `{}`",
1318 err.span_label(impl_item.span, "does not match trait");
1319 if let Some(trait_span) = tcx.hir.span_if_local(ty_trait_item.def_id) {
1320 err.span_label(trait_span, "item in trait");
1328 check_specialization_validity(tcx, trait_def, impl_id, impl_item);
1331 // Check for missing items from trait
1332 let mut missing_items = Vec::new();
1333 let mut invalidated_items = Vec::new();
1334 let associated_type_overridden = overridden_associated_type.is_some();
1335 for trait_item in tcx.associated_items(impl_trait_ref.def_id) {
1336 let is_implemented = trait_def.ancestors(tcx, impl_id)
1337 .defs(tcx, trait_item.name, trait_item.kind)
1339 .map(|node_item| !node_item.node.is_from_trait())
1342 if !is_implemented {
1343 if !trait_item.defaultness.has_value() {
1344 missing_items.push(trait_item);
1345 } else if associated_type_overridden {
1346 invalidated_items.push(trait_item.name);
1351 let signature = |item: &ty::AssociatedItem| {
1353 ty::AssociatedKind::Method => {
1354 format!("{}", tcx.type_of(item.def_id).fn_sig().0)
1356 ty::AssociatedKind::Type => format!("type {};", item.name.to_string()),
1357 ty::AssociatedKind::Const => {
1358 format!("const {}: {:?};", item.name.to_string(), tcx.type_of(item.def_id))
1363 if !missing_items.is_empty() {
1364 let mut err = struct_span_err!(tcx.sess, impl_span, E0046,
1365 "not all trait items implemented, missing: `{}`",
1366 missing_items.iter()
1367 .map(|trait_item| trait_item.name.to_string())
1368 .collect::<Vec<_>>().join("`, `"));
1369 err.span_label(impl_span, format!("missing `{}` in implementation",
1370 missing_items.iter()
1371 .map(|trait_item| trait_item.name.to_string())
1372 .collect::<Vec<_>>().join("`, `")));
1373 for trait_item in missing_items {
1374 if let Some(span) = tcx.hir.span_if_local(trait_item.def_id) {
1375 err.span_label(span, format!("`{}` from trait", trait_item.name));
1377 err.note(&format!("`{}` from trait: `{}`",
1379 signature(&trait_item)));
1385 if !invalidated_items.is_empty() {
1386 let invalidator = overridden_associated_type.unwrap();
1387 span_err!(tcx.sess, invalidator.span, E0399,
1388 "the following trait items need to be reimplemented \
1389 as `{}` was overridden: `{}`",
1391 invalidated_items.iter()
1392 .map(|name| name.to_string())
1393 .collect::<Vec<_>>().join("`, `"))
1397 /// Checks whether a type can be represented in memory. In particular, it
1398 /// identifies types that contain themselves without indirection through a
1399 /// pointer, which would mean their size is unbounded.
1400 fn check_representable<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
1404 let rty = tcx.type_of(item_def_id);
1406 // Check that it is possible to represent this type. This call identifies
1407 // (1) types that contain themselves and (2) types that contain a different
1408 // recursive type. It is only necessary to throw an error on those that
1409 // contain themselves. For case 2, there must be an inner type that will be
1410 // caught by case 1.
1411 match rty.is_representable(tcx, sp) {
1412 Representability::SelfRecursive(spans) => {
1413 let mut err = tcx.recursive_type_with_infinite_size_error(item_def_id);
1415 err.span_label(span, "recursive without indirection");
1420 Representability::Representable | Representability::ContainsRecursive => (),
1425 pub fn check_simd<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, sp: Span, def_id: DefId) {
1426 let t = tcx.type_of(def_id);
1428 ty::TyAdt(def, substs) if def.is_struct() => {
1429 let fields = &def.struct_variant().fields;
1430 if fields.is_empty() {
1431 span_err!(tcx.sess, sp, E0075, "SIMD vector cannot be empty");
1434 let e = fields[0].ty(tcx, substs);
1435 if !fields.iter().all(|f| f.ty(tcx, substs) == e) {
1436 struct_span_err!(tcx.sess, sp, E0076, "SIMD vector should be homogeneous")
1437 .span_label(sp, "SIMD elements must have the same type")
1442 ty::TyParam(_) => { /* struct<T>(T, T, T, T) is ok */ }
1443 _ if e.is_machine() => { /* struct(u8, u8, u8, u8) is ok */ }
1445 span_err!(tcx.sess, sp, E0077,
1446 "SIMD vector element type should be machine type");
1455 fn check_packed<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, sp: Span, def_id: DefId) {
1456 if check_packed_inner(tcx, def_id, &mut Vec::new()) {
1457 struct_span_err!(tcx.sess, sp, E0588,
1458 "packed struct cannot transitively contain a `[repr(align)]` struct").emit();
1462 fn check_packed_inner<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
1464 stack: &mut Vec<DefId>) -> bool {
1465 let t = tcx.type_of(def_id);
1466 if stack.contains(&def_id) {
1467 debug!("check_packed_inner: {:?} is recursive", t);
1471 ty::TyAdt(def, substs) if def.is_struct() => {
1472 if tcx.adt_def(def.did).repr.align > 0 {
1475 // push struct def_id before checking fields
1477 for field in &def.struct_variant().fields {
1478 let f = field.ty(tcx, substs);
1480 ty::TyAdt(def, _) => {
1481 if check_packed_inner(tcx, def.did, stack) {
1488 // only need to pop if not early out
1496 #[allow(trivial_numeric_casts)]
1497 pub fn check_enum<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
1499 vs: &'tcx [hir::Variant],
1501 let def_id = tcx.hir.local_def_id(id);
1502 let def = tcx.adt_def(def_id);
1503 def.destructor(tcx); // force the destructor to be evaluated
1505 if vs.is_empty() && tcx.has_attr(def_id, "repr") {
1507 tcx.sess, sp, E0084,
1508 "unsupported representation for zero-variant enum")
1509 .span_label(sp, "unsupported enum representation")
1513 let repr_type_ty = def.repr.discr_type().to_ty(tcx);
1514 if repr_type_ty == tcx.types.i128 || repr_type_ty == tcx.types.u128 {
1515 if !tcx.sess.features.borrow().i128_type {
1516 emit_feature_err(&tcx.sess.parse_sess,
1517 "i128_type", sp, GateIssue::Language, "128-bit type is unstable");
1522 if let Some(e) = v.node.disr_expr {
1523 tcx.typeck_tables_of(tcx.hir.local_def_id(e.node_id));
1527 let mut disr_vals: Vec<ConstInt> = Vec::new();
1528 for (discr, v) in def.discriminants(tcx).zip(vs) {
1529 // Check for duplicate discriminant values
1530 if let Some(i) = disr_vals.iter().position(|&x| x == discr) {
1531 let variant_i_node_id = tcx.hir.as_local_node_id(def.variants[i].did).unwrap();
1532 let variant_i = tcx.hir.expect_variant(variant_i_node_id);
1533 let i_span = match variant_i.node.disr_expr {
1534 Some(expr) => tcx.hir.span(expr.node_id),
1535 None => tcx.hir.span(variant_i_node_id)
1537 let span = match v.node.disr_expr {
1538 Some(expr) => tcx.hir.span(expr.node_id),
1541 struct_span_err!(tcx.sess, span, E0081,
1542 "discriminant value `{}` already exists", disr_vals[i])
1543 .span_label(i_span, format!("first use of `{}`", disr_vals[i]))
1544 .span_label(span , format!("enum already has `{}`", disr_vals[i]))
1547 disr_vals.push(discr);
1550 check_representable(tcx, sp, def_id);
1553 impl<'a, 'gcx, 'tcx> AstConv<'gcx, 'tcx> for FnCtxt<'a, 'gcx, 'tcx> {
1554 fn tcx<'b>(&'b self) -> TyCtxt<'b, 'gcx, 'tcx> { self.tcx }
1556 fn get_type_parameter_bounds(&self, _: Span, def_id: DefId)
1557 -> ty::GenericPredicates<'tcx>
1560 let node_id = tcx.hir.as_local_node_id(def_id).unwrap();
1561 let item_id = tcx.hir.ty_param_owner(node_id);
1562 let item_def_id = tcx.hir.local_def_id(item_id);
1563 let generics = tcx.generics_of(item_def_id);
1564 let index = generics.type_param_to_index[&def_id.index];
1565 ty::GenericPredicates {
1567 predicates: self.param_env.caller_bounds.iter().filter(|predicate| {
1569 ty::Predicate::Trait(ref data) => {
1570 data.0.self_ty().is_param(index)
1574 }).cloned().collect()
1578 fn re_infer(&self, span: Span, def: Option<&ty::RegionParameterDef>)
1579 -> Option<ty::Region<'tcx>> {
1581 Some(def) => infer::EarlyBoundRegion(span, def.name, def.issue_32330),
1582 None => infer::MiscVariable(span)
1584 Some(self.next_region_var(v))
1587 fn ty_infer(&self, span: Span) -> Ty<'tcx> {
1588 self.next_ty_var(TypeVariableOrigin::TypeInference(span))
1591 fn ty_infer_for_def(&self,
1592 ty_param_def: &ty::TypeParameterDef,
1593 substs: &[Kind<'tcx>],
1594 span: Span) -> Ty<'tcx> {
1595 self.type_var_for_def(span, ty_param_def, substs)
1598 fn projected_ty_from_poly_trait_ref(&self,
1600 poly_trait_ref: ty::PolyTraitRef<'tcx>,
1601 item_name: ast::Name)
1604 let (trait_ref, _) =
1605 self.replace_late_bound_regions_with_fresh_var(
1607 infer::LateBoundRegionConversionTime::AssocTypeProjection(item_name),
1610 self.tcx().mk_projection(trait_ref, item_name)
1613 fn normalize_ty(&self, span: Span, ty: Ty<'tcx>) -> Ty<'tcx> {
1614 if ty.has_escaping_regions() {
1615 ty // FIXME: normalization and escaping regions
1617 self.normalize_associated_types_in(span, &ty)
1621 fn set_tainted_by_errors(&self) {
1622 self.infcx.set_tainted_by_errors()
1626 /// Controls whether the arguments are tupled. This is used for the call
1629 /// Tupling means that all call-side arguments are packed into a tuple and
1630 /// passed as a single parameter. For example, if tupling is enabled, this
1633 /// fn f(x: (isize, isize))
1635 /// Can be called as:
1642 #[derive(Clone, Eq, PartialEq)]
1643 enum TupleArgumentsFlag {
1648 impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
1649 pub fn new(inh: &'a Inherited<'a, 'gcx, 'tcx>,
1650 param_env: ty::ParamEnv<'tcx>,
1651 body_id: ast::NodeId)
1652 -> FnCtxt<'a, 'gcx, 'tcx> {
1656 err_count_on_creation: inh.tcx.sess.err_count(),
1658 ps: RefCell::new(UnsafetyState::function(hir::Unsafety::Normal,
1659 ast::CRATE_NODE_ID)),
1660 diverges: Cell::new(Diverges::Maybe),
1661 has_errors: Cell::new(false),
1662 enclosing_breakables: RefCell::new(EnclosingBreakables {
1670 pub fn sess(&self) -> &Session {
1674 pub fn err_count_since_creation(&self) -> usize {
1675 self.tcx.sess.err_count() - self.err_count_on_creation
1678 /// Produce warning on the given node, if the current point in the
1679 /// function is unreachable, and there hasn't been another warning.
1680 fn warn_if_unreachable(&self, id: ast::NodeId, span: Span, kind: &str) {
1681 if self.diverges.get() == Diverges::Always {
1682 self.diverges.set(Diverges::WarnedAlways);
1684 debug!("warn_if_unreachable: id={:?} span={:?} kind={}", id, span, kind);
1686 self.tables.borrow_mut().lints.add_lint(
1687 lint::builtin::UNREACHABLE_CODE,
1689 format!("unreachable {}", kind));
1695 code: ObligationCauseCode<'tcx>)
1696 -> ObligationCause<'tcx> {
1697 ObligationCause::new(span, self.body_id, code)
1700 pub fn misc(&self, span: Span) -> ObligationCause<'tcx> {
1701 self.cause(span, ObligationCauseCode::MiscObligation)
1704 /// Resolves type variables in `ty` if possible. Unlike the infcx
1705 /// version (resolve_type_vars_if_possible), this version will
1706 /// also select obligations if it seems useful, in an effort
1707 /// to get more type information.
1708 fn resolve_type_vars_with_obligations(&self, mut ty: Ty<'tcx>) -> Ty<'tcx> {
1709 debug!("resolve_type_vars_with_obligations(ty={:?})", ty);
1711 // No TyInfer()? Nothing needs doing.
1712 if !ty.has_infer_types() {
1713 debug!("resolve_type_vars_with_obligations: ty={:?}", ty);
1717 // If `ty` is a type variable, see whether we already know what it is.
1718 ty = self.resolve_type_vars_if_possible(&ty);
1719 if !ty.has_infer_types() {
1720 debug!("resolve_type_vars_with_obligations: ty={:?}", ty);
1724 // If not, try resolving pending obligations as much as
1725 // possible. This can help substantially when there are
1726 // indirect dependencies that don't seem worth tracking
1728 self.select_obligations_where_possible();
1729 ty = self.resolve_type_vars_if_possible(&ty);
1731 debug!("resolve_type_vars_with_obligations: ty={:?}", ty);
1735 fn record_deferred_call_resolution(&self,
1736 closure_def_id: DefId,
1737 r: DeferredCallResolution<'gcx, 'tcx>) {
1738 let mut deferred_call_resolutions = self.deferred_call_resolutions.borrow_mut();
1739 deferred_call_resolutions.entry(closure_def_id).or_insert(vec![]).push(r);
1742 fn remove_deferred_call_resolutions(&self,
1743 closure_def_id: DefId)
1744 -> Vec<DeferredCallResolution<'gcx, 'tcx>>
1746 let mut deferred_call_resolutions = self.deferred_call_resolutions.borrow_mut();
1747 deferred_call_resolutions.remove(&closure_def_id).unwrap_or(vec![])
1750 pub fn tag(&self) -> String {
1751 let self_ptr: *const FnCtxt = self;
1752 format!("{:?}", self_ptr)
1755 pub fn local_ty(&self, span: Span, nid: ast::NodeId) -> Ty<'tcx> {
1756 match self.locals.borrow().get(&nid) {
1759 span_bug!(span, "no type for local variable {}",
1760 self.tcx.hir.node_to_string(nid));
1766 pub fn write_ty(&self, node_id: ast::NodeId, ty: Ty<'tcx>) {
1767 debug!("write_ty({}, {:?}) in fcx {}",
1768 node_id, self.resolve_type_vars_if_possible(&ty), self.tag());
1769 self.tables.borrow_mut().node_types.insert(node_id, ty);
1771 if ty.references_error() {
1772 self.has_errors.set(true);
1773 self.set_tainted_by_errors();
1777 pub fn write_method_call(&self, node_id: ast::NodeId, method: MethodCallee<'tcx>) {
1778 self.tables.borrow_mut().type_dependent_defs.insert(node_id, Def::Method(method.def_id));
1779 self.write_substs(node_id, method.substs);
1782 pub fn write_substs(&self, node_id: ast::NodeId, substs: &'tcx Substs<'tcx>) {
1783 if !substs.is_noop() {
1784 debug!("write_substs({}, {:?}) in fcx {}",
1789 self.tables.borrow_mut().node_substs.insert(node_id, substs);
1793 pub fn apply_adjustments(&self, expr: &hir::Expr, adj: Vec<Adjustment<'tcx>>) {
1794 debug!("apply_adjustments(expr={:?}, adj={:?})", expr, adj);
1800 match self.tables.borrow_mut().adjustments.entry(expr.id) {
1801 Entry::Vacant(entry) => { entry.insert(adj); },
1802 Entry::Occupied(mut entry) => {
1803 debug!(" - composing on top of {:?}", entry.get());
1804 match (&entry.get()[..], &adj[..]) {
1805 // Applying any adjustment on top of a NeverToAny
1806 // is a valid NeverToAny adjustment, because it can't
1808 (&[Adjustment { kind: Adjust::NeverToAny, .. }], _) => return,
1810 Adjustment { kind: Adjust::Deref(_), .. },
1811 Adjustment { kind: Adjust::Borrow(AutoBorrow::Ref(..)), .. },
1813 Adjustment { kind: Adjust::Deref(_), .. },
1814 .. // Any following adjustments are allowed.
1816 // A reborrow has no effect before a dereference.
1818 // FIXME: currently we never try to compose autoderefs
1819 // and ReifyFnPointer/UnsafeFnPointer, but we could.
1821 bug!("while adjusting {:?}, can't compose {:?} and {:?}",
1822 expr, entry.get(), adj)
1824 *entry.get_mut() = adj;
1829 /// Basically whenever we are converting from a type scheme into
1830 /// the fn body space, we always want to normalize associated
1831 /// types as well. This function combines the two.
1832 fn instantiate_type_scheme<T>(&self,
1834 substs: &Substs<'tcx>,
1837 where T : TypeFoldable<'tcx>
1839 let value = value.subst(self.tcx, substs);
1840 let result = self.normalize_associated_types_in(span, &value);
1841 debug!("instantiate_type_scheme(value={:?}, substs={:?}) = {:?}",
1848 /// As `instantiate_type_scheme`, but for the bounds found in a
1849 /// generic type scheme.
1850 fn instantiate_bounds(&self, span: Span, def_id: DefId, substs: &Substs<'tcx>)
1851 -> ty::InstantiatedPredicates<'tcx> {
1852 let bounds = self.tcx.predicates_of(def_id);
1853 let result = bounds.instantiate(self.tcx, substs);
1854 let result = self.normalize_associated_types_in(span, &result);
1855 debug!("instantiate_bounds(bounds={:?}, substs={:?}) = {:?}",
1862 /// Replace all anonymized types with fresh inference variables
1863 /// and record them for writeback.
1864 fn instantiate_anon_types<T: TypeFoldable<'tcx>>(&self, value: &T) -> T {
1865 value.fold_with(&mut BottomUpFolder { tcx: self.tcx, fldop: |ty| {
1866 if let ty::TyAnon(def_id, substs) = ty.sty {
1867 // Use the same type variable if the exact same TyAnon appears more
1868 // than once in the return type (e.g. if it's pased to a type alias).
1869 let id = self.tcx.hir.as_local_node_id(def_id).unwrap();
1870 if let Some(ty_var) = self.anon_types.borrow().get(&id) {
1873 let span = self.tcx.def_span(def_id);
1874 let ty_var = self.next_ty_var(TypeVariableOrigin::TypeInference(span));
1875 self.anon_types.borrow_mut().insert(id, ty_var);
1877 let predicates_of = self.tcx.predicates_of(def_id);
1878 let bounds = predicates_of.instantiate(self.tcx, substs);
1880 for predicate in bounds.predicates {
1881 // Change the predicate to refer to the type variable,
1882 // which will be the concrete type, instead of the TyAnon.
1883 // This also instantiates nested `impl Trait`.
1884 let predicate = self.instantiate_anon_types(&predicate);
1886 // Require that the predicate holds for the concrete type.
1887 let cause = traits::ObligationCause::new(span, self.body_id,
1888 traits::ReturnType);
1889 self.register_predicate(traits::Obligation::new(cause,
1901 fn normalize_associated_types_in<T>(&self, span: Span, value: &T) -> T
1902 where T : TypeFoldable<'tcx>
1904 self.inh.normalize_associated_types_in(span, self.body_id, self.param_env, value)
1907 fn normalize_associated_types_in_as_infer_ok<T>(&self, span: Span, value: &T)
1909 where T : TypeFoldable<'tcx>
1911 self.inh.normalize_associated_types_in_as_infer_ok(span,
1917 pub fn write_nil(&self, node_id: ast::NodeId) {
1918 self.write_ty(node_id, self.tcx.mk_nil());
1921 pub fn write_error(&self, node_id: ast::NodeId) {
1922 self.write_ty(node_id, self.tcx.types.err);
1925 pub fn require_type_meets(&self,
1928 code: traits::ObligationCauseCode<'tcx>,
1931 self.register_bound(
1934 traits::ObligationCause::new(span, self.body_id, code));
1937 pub fn require_type_is_sized(&self,
1940 code: traits::ObligationCauseCode<'tcx>)
1942 let lang_item = self.tcx.require_lang_item(lang_items::SizedTraitLangItem);
1943 self.require_type_meets(ty, span, code, lang_item);
1946 pub fn register_bound(&self,
1949 cause: traits::ObligationCause<'tcx>)
1951 self.fulfillment_cx.borrow_mut()
1952 .register_bound(self, self.param_env, ty, def_id, cause);
1955 pub fn to_ty(&self, ast_t: &hir::Ty) -> Ty<'tcx> {
1956 let t = AstConv::ast_ty_to_ty(self, ast_t);
1957 self.register_wf_obligation(t, ast_t.span, traits::MiscObligation);
1961 pub fn node_ty(&self, id: ast::NodeId) -> Ty<'tcx> {
1962 match self.tables.borrow().node_types.get(&id) {
1964 None if self.err_count_since_creation() != 0 => self.tcx.types.err,
1966 bug!("no type for node {}: {} in fcx {}",
1967 id, self.tcx.hir.node_to_string(id),
1973 /// Registers an obligation for checking later, during regionck, that the type `ty` must
1974 /// outlive the region `r`.
1975 pub fn register_region_obligation(&self,
1977 region: ty::Region<'tcx>,
1978 cause: traits::ObligationCause<'tcx>)
1980 let mut fulfillment_cx = self.fulfillment_cx.borrow_mut();
1981 fulfillment_cx.register_region_obligation(ty, region, cause);
1984 /// Registers an obligation for checking later, during regionck, that the type `ty` must
1985 /// outlive the region `r`.
1986 pub fn register_wf_obligation(&self,
1989 code: traits::ObligationCauseCode<'tcx>)
1991 // WF obligations never themselves fail, so no real need to give a detailed cause:
1992 let cause = traits::ObligationCause::new(span, self.body_id, code);
1993 self.register_predicate(traits::Obligation::new(cause,
1995 ty::Predicate::WellFormed(ty)));
1998 pub fn register_old_wf_obligation(&self,
2001 code: traits::ObligationCauseCode<'tcx>)
2003 // Registers an "old-style" WF obligation that uses the
2004 // implicator code. This is basically a buggy version of
2005 // `register_wf_obligation` that is being kept around
2006 // temporarily just to help with phasing in the newer rules.
2008 // FIXME(#27579) all uses of this should be migrated to register_wf_obligation eventually
2009 let cause = traits::ObligationCause::new(span, self.body_id, code);
2010 self.register_region_obligation(ty, self.tcx.types.re_empty, cause);
2013 /// Registers obligations that all types appearing in `substs` are well-formed.
2014 pub fn add_wf_bounds(&self, substs: &Substs<'tcx>, expr: &hir::Expr)
2016 for ty in substs.types() {
2017 self.register_wf_obligation(ty, expr.span, traits::MiscObligation);
2021 /// Given a fully substituted set of bounds (`generic_bounds`), and the values with which each
2022 /// type/region parameter was instantiated (`substs`), creates and registers suitable
2023 /// trait/region obligations.
2025 /// For example, if there is a function:
2028 /// fn foo<'a,T:'a>(...)
2031 /// and a reference:
2037 /// Then we will create a fresh region variable `'$0` and a fresh type variable `$1` for `'a`
2038 /// and `T`. This routine will add a region obligation `$1:'$0` and register it locally.
2039 pub fn add_obligations_for_parameters(&self,
2040 cause: traits::ObligationCause<'tcx>,
2041 predicates: &ty::InstantiatedPredicates<'tcx>)
2043 assert!(!predicates.has_escaping_regions());
2045 debug!("add_obligations_for_parameters(predicates={:?})",
2048 for obligation in traits::predicates_for_generics(cause, self.param_env, predicates) {
2049 self.register_predicate(obligation);
2053 // FIXME(arielb1): use this instead of field.ty everywhere
2054 // Only for fields! Returns <none> for methods>
2055 // Indifferent to privacy flags
2056 pub fn field_ty(&self,
2058 field: &'tcx ty::FieldDef,
2059 substs: &Substs<'tcx>)
2062 self.normalize_associated_types_in(span,
2063 &field.ty(self.tcx, substs))
2066 fn check_casts(&self) {
2067 let mut deferred_cast_checks = self.deferred_cast_checks.borrow_mut();
2068 for cast in deferred_cast_checks.drain(..) {
2073 /// Apply "fallbacks" to some types
2074 /// unconstrained types get replaced with ! or () (depending on whether
2075 /// feature(never_type) is enabled), unconstrained ints with i32, and
2076 /// unconstrained floats with f64.
2077 fn default_type_parameters(&self) {
2078 use rustc::ty::error::UnconstrainedNumeric::Neither;
2079 use rustc::ty::error::UnconstrainedNumeric::{UnconstrainedInt, UnconstrainedFloat};
2081 // Defaulting inference variables becomes very dubious if we have
2082 // encountered type-checking errors. Therefore, if we think we saw
2083 // some errors in this function, just resolve all uninstanted type
2084 // varibles to TyError.
2085 if self.is_tainted_by_errors() {
2086 for ty in &self.unsolved_variables() {
2087 if let ty::TyInfer(_) = self.shallow_resolve(ty).sty {
2088 debug!("default_type_parameters: defaulting `{:?}` to error", ty);
2089 self.demand_eqtype(syntax_pos::DUMMY_SP, *ty, self.tcx().types.err);
2095 for ty in &self.unsolved_variables() {
2096 let resolved = self.resolve_type_vars_if_possible(ty);
2097 if self.type_var_diverges(resolved) {
2098 debug!("default_type_parameters: defaulting `{:?}` to `!` because it diverges",
2100 self.demand_eqtype(syntax_pos::DUMMY_SP, *ty,
2101 self.tcx.mk_diverging_default());
2103 match self.type_is_unconstrained_numeric(resolved) {
2104 UnconstrainedInt => {
2105 debug!("default_type_parameters: defaulting `{:?}` to `i32`",
2107 self.demand_eqtype(syntax_pos::DUMMY_SP, *ty, self.tcx.types.i32)
2109 UnconstrainedFloat => {
2110 debug!("default_type_parameters: defaulting `{:?}` to `f32`",
2112 self.demand_eqtype(syntax_pos::DUMMY_SP, *ty, self.tcx.types.f64)
2120 // Implements type inference fallback algorithm
2121 fn select_all_obligations_and_apply_defaults(&self) {
2122 self.select_obligations_where_possible();
2123 self.default_type_parameters();
2124 self.select_obligations_where_possible();
2127 fn select_all_obligations_or_error(&self) {
2128 debug!("select_all_obligations_or_error");
2130 // upvar inference should have ensured that all deferred call
2131 // resolutions are handled by now.
2132 assert!(self.deferred_call_resolutions.borrow().is_empty());
2134 self.select_all_obligations_and_apply_defaults();
2136 let mut fulfillment_cx = self.fulfillment_cx.borrow_mut();
2138 match fulfillment_cx.select_all_or_error(self) {
2140 Err(errors) => { self.report_fulfillment_errors(&errors); }
2144 /// Select as many obligations as we can at present.
2145 fn select_obligations_where_possible(&self) {
2146 match self.fulfillment_cx.borrow_mut().select_where_possible(self) {
2148 Err(errors) => { self.report_fulfillment_errors(&errors); }
2152 /// For the overloaded lvalue expressions (`*x`, `x[3]`), the trait
2153 /// returns a type of `&T`, but the actual type we assign to the
2154 /// *expression* is `T`. So this function just peels off the return
2155 /// type by one layer to yield `T`.
2156 fn make_overloaded_lvalue_return_type(&self,
2157 method: MethodCallee<'tcx>)
2158 -> ty::TypeAndMut<'tcx>
2160 // extract method return type, which will be &T;
2161 // all LB regions should have been instantiated during method lookup
2162 let ret_ty = method.sig.output();
2164 // method returns &T, but the type as visible to user is T, so deref
2165 ret_ty.builtin_deref(true, NoPreference).unwrap()
2168 fn lookup_indexing(&self,
2170 base_expr: &'gcx hir::Expr,
2173 lvalue_pref: LvaluePreference)
2174 -> Option<(/*index type*/ Ty<'tcx>, /*element type*/ Ty<'tcx>)>
2176 // FIXME(#18741) -- this is almost but not quite the same as the
2177 // autoderef that normal method probing does. They could likely be
2180 let mut autoderef = self.autoderef(base_expr.span, base_ty);
2181 let mut result = None;
2182 while result.is_none() && autoderef.next().is_some() {
2183 result = self.try_index_step(expr, base_expr, &autoderef, lvalue_pref, idx_ty);
2185 autoderef.finalize();
2189 /// To type-check `base_expr[index_expr]`, we progressively autoderef
2190 /// (and otherwise adjust) `base_expr`, looking for a type which either
2191 /// supports builtin indexing or overloaded indexing.
2192 /// This loop implements one step in that search; the autoderef loop
2193 /// is implemented by `lookup_indexing`.
2194 fn try_index_step(&self,
2196 base_expr: &hir::Expr,
2197 autoderef: &Autoderef<'a, 'gcx, 'tcx>,
2198 lvalue_pref: LvaluePreference,
2200 -> Option<(/*index type*/ Ty<'tcx>, /*element type*/ Ty<'tcx>)>
2202 let adjusted_ty = autoderef.unambiguous_final_ty();
2203 debug!("try_index_step(expr={:?}, base_expr={:?}, adjusted_ty={:?}, \
2211 // First, try built-in indexing.
2212 match (adjusted_ty.builtin_index(), &index_ty.sty) {
2213 (Some(ty), &ty::TyUint(ast::UintTy::Us)) | (Some(ty), &ty::TyInfer(ty::IntVar(_))) => {
2214 debug!("try_index_step: success, using built-in indexing");
2215 let adjustments = autoderef.adjust_steps(lvalue_pref);
2216 self.apply_adjustments(base_expr, adjustments);
2217 return Some((self.tcx.types.usize, ty));
2222 for &unsize in &[false, true] {
2223 let mut self_ty = adjusted_ty;
2225 // We only unsize arrays here.
2226 if let ty::TyArray(element_ty, _) = adjusted_ty.sty {
2227 self_ty = self.tcx.mk_slice(element_ty);
2233 // If some lookup succeeds, write callee into table and extract index/element
2234 // type from the method signature.
2235 // If some lookup succeeded, install method in table
2236 let input_ty = self.next_ty_var(TypeVariableOrigin::AutoDeref(base_expr.span));
2237 let method = self.try_overloaded_lvalue_op(
2238 expr.span, self_ty, &[input_ty], lvalue_pref, LvalueOp::Index);
2240 let result = method.map(|ok| {
2241 debug!("try_index_step: success, using overloaded indexing");
2242 let method = self.register_infer_ok_obligations(ok);
2244 let mut adjustments = autoderef.adjust_steps(lvalue_pref);
2245 if let ty::TyRef(region, mt) = method.sig.inputs()[0].sty {
2246 adjustments.push(Adjustment {
2247 kind: Adjust::Borrow(AutoBorrow::Ref(region, mt.mutbl)),
2248 target: self.tcx.mk_ref(region, ty::TypeAndMut {
2255 adjustments.push(Adjustment {
2256 kind: Adjust::Unsize,
2257 target: method.sig.inputs()[0]
2260 self.apply_adjustments(base_expr, adjustments);
2262 self.write_method_call(expr.id, method);
2263 (input_ty, self.make_overloaded_lvalue_return_type(method).ty)
2265 if result.is_some() {
2273 fn resolve_lvalue_op(&self, op: LvalueOp, is_mut: bool) -> (Option<DefId>, Symbol) {
2274 let (tr, name) = match (op, is_mut) {
2275 (LvalueOp::Deref, false) =>
2276 (self.tcx.lang_items.deref_trait(), "deref"),
2277 (LvalueOp::Deref, true) =>
2278 (self.tcx.lang_items.deref_mut_trait(), "deref_mut"),
2279 (LvalueOp::Index, false) =>
2280 (self.tcx.lang_items.index_trait(), "index"),
2281 (LvalueOp::Index, true) =>
2282 (self.tcx.lang_items.index_mut_trait(), "index_mut"),
2284 (tr, Symbol::intern(name))
2287 fn try_overloaded_lvalue_op(&self,
2290 arg_tys: &[Ty<'tcx>],
2291 lvalue_pref: LvaluePreference,
2293 -> Option<InferOk<'tcx, MethodCallee<'tcx>>>
2295 debug!("try_overloaded_lvalue_op({:?},{:?},{:?},{:?})",
2301 // Try Mut first, if preferred.
2302 let (mut_tr, mut_op) = self.resolve_lvalue_op(op, true);
2303 let method = match (lvalue_pref, mut_tr) {
2304 (PreferMutLvalue, Some(trait_did)) => {
2305 self.lookup_method_in_trait(span, mut_op, trait_did, base_ty, Some(arg_tys))
2310 // Otherwise, fall back to the immutable version.
2311 let (imm_tr, imm_op) = self.resolve_lvalue_op(op, false);
2312 let method = match (method, imm_tr) {
2313 (None, Some(trait_did)) => {
2314 self.lookup_method_in_trait(span, imm_op, trait_did, base_ty, Some(arg_tys))
2316 (method, _) => method,
2322 fn check_method_argument_types(&self,
2324 method: Result<MethodCallee<'tcx>, ()>,
2325 args_no_rcvr: &'gcx [hir::Expr],
2326 tuple_arguments: TupleArgumentsFlag,
2327 expected: Expectation<'tcx>)
2329 let has_error = match method {
2331 method.substs.references_error() || method.sig.references_error()
2336 let err_inputs = self.err_args(args_no_rcvr.len());
2338 let err_inputs = match tuple_arguments {
2339 DontTupleArguments => err_inputs,
2340 TupleArguments => vec![self.tcx.intern_tup(&err_inputs[..], false)],
2343 self.check_argument_types(sp, &err_inputs[..], &[], args_no_rcvr,
2344 false, tuple_arguments, None);
2345 return self.tcx.types.err;
2348 let method = method.unwrap();
2349 // HACK(eddyb) ignore self in the definition (see above).
2350 let expected_arg_tys = self.expected_inputs_for_expected_output(
2353 method.sig.output(),
2354 &method.sig.inputs()[1..]
2356 self.check_argument_types(sp, &method.sig.inputs()[1..], &expected_arg_tys[..],
2357 args_no_rcvr, method.sig.variadic, tuple_arguments,
2358 self.tcx.hir.span_if_local(method.def_id));
2362 /// Generic function that factors out common logic from function calls,
2363 /// method calls and overloaded operators.
2364 fn check_argument_types(&self,
2366 fn_inputs: &[Ty<'tcx>],
2367 expected_arg_tys: &[Ty<'tcx>],
2368 args: &'gcx [hir::Expr],
2370 tuple_arguments: TupleArgumentsFlag,
2371 def_span: Option<Span>) {
2374 // Grab the argument types, supplying fresh type variables
2375 // if the wrong number of arguments were supplied
2376 let supplied_arg_count = if tuple_arguments == DontTupleArguments {
2382 // All the input types from the fn signature must outlive the call
2383 // so as to validate implied bounds.
2384 for &fn_input_ty in fn_inputs {
2385 self.register_wf_obligation(fn_input_ty, sp, traits::MiscObligation);
2388 let mut expected_arg_tys = expected_arg_tys;
2389 let expected_arg_count = fn_inputs.len();
2391 let sp_args = if args.len() > 0 {
2392 let (first, args) = args.split_at(1);
2393 let mut sp_tmp = first[0].span;
2395 let sp_opt = self.sess().codemap().merge_spans(sp_tmp, arg.span);
2396 if ! sp_opt.is_some() {
2399 sp_tmp = sp_opt.unwrap();
2406 fn parameter_count_error<'tcx>(sess: &Session, sp: Span, expected_count: usize,
2407 arg_count: usize, error_code: &str, variadic: bool,
2408 def_span: Option<Span>) {
2409 let mut err = sess.struct_span_err_with_code(sp,
2410 &format!("this function takes {}{} parameter{} but {} parameter{} supplied",
2411 if variadic {"at least "} else {""},
2413 if expected_count == 1 {""} else {"s"},
2415 if arg_count == 1 {" was"} else {"s were"}),
2418 err.span_label(sp, format!("expected {}{} parameter{}",
2419 if variadic {"at least "} else {""},
2421 if expected_count == 1 {""} else {"s"}));
2422 if let Some(def_s) = def_span {
2423 err.span_label(def_s, "defined here");
2428 let formal_tys = if tuple_arguments == TupleArguments {
2429 let tuple_type = self.structurally_resolved_type(sp, fn_inputs[0]);
2430 match tuple_type.sty {
2431 ty::TyTuple(arg_types, _) if arg_types.len() != args.len() => {
2432 parameter_count_error(tcx.sess, sp_args, arg_types.len(), args.len(),
2433 "E0057", false, def_span);
2434 expected_arg_tys = &[];
2435 self.err_args(args.len())
2437 ty::TyTuple(arg_types, _) => {
2438 expected_arg_tys = match expected_arg_tys.get(0) {
2439 Some(&ty) => match ty.sty {
2440 ty::TyTuple(ref tys, _) => &tys,
2448 span_err!(tcx.sess, sp, E0059,
2449 "cannot use call notation; the first type parameter \
2450 for the function trait is neither a tuple nor unit");
2451 expected_arg_tys = &[];
2452 self.err_args(args.len())
2455 } else if expected_arg_count == supplied_arg_count {
2457 } else if variadic {
2458 if supplied_arg_count >= expected_arg_count {
2461 parameter_count_error(tcx.sess, sp_args, expected_arg_count,
2462 supplied_arg_count, "E0060", true, def_span);
2463 expected_arg_tys = &[];
2464 self.err_args(supplied_arg_count)
2467 parameter_count_error(tcx.sess, sp_args, expected_arg_count,
2468 supplied_arg_count, "E0061", false, def_span);
2469 expected_arg_tys = &[];
2470 self.err_args(supplied_arg_count)
2473 debug!("check_argument_types: formal_tys={:?}",
2474 formal_tys.iter().map(|t| self.ty_to_string(*t)).collect::<Vec<String>>());
2476 // Check the arguments.
2477 // We do this in a pretty awful way: first we typecheck any arguments
2478 // that are not closures, then we typecheck the closures. This is so
2479 // that we have more information about the types of arguments when we
2480 // typecheck the functions. This isn't really the right way to do this.
2481 for &check_closures in &[false, true] {
2482 debug!("check_closures={}", check_closures);
2484 // More awful hacks: before we check argument types, try to do
2485 // an "opportunistic" vtable resolution of any trait bounds on
2486 // the call. This helps coercions.
2488 self.select_obligations_where_possible();
2491 // For variadic functions, we don't have a declared type for all of
2492 // the arguments hence we only do our usual type checking with
2493 // the arguments who's types we do know.
2494 let t = if variadic {
2496 } else if tuple_arguments == TupleArguments {
2501 for (i, arg) in args.iter().take(t).enumerate() {
2502 // Warn only for the first loop (the "no closures" one).
2503 // Closure arguments themselves can't be diverging, but
2504 // a previous argument can, e.g. `foo(panic!(), || {})`.
2505 if !check_closures {
2506 self.warn_if_unreachable(arg.id, arg.span, "expression");
2509 let is_closure = match arg.node {
2510 hir::ExprClosure(..) => true,
2514 if is_closure != check_closures {
2518 debug!("checking the argument");
2519 let formal_ty = formal_tys[i];
2521 // The special-cased logic below has three functions:
2522 // 1. Provide as good of an expected type as possible.
2523 let expected = expected_arg_tys.get(i).map(|&ty| {
2524 Expectation::rvalue_hint(self, ty)
2527 let checked_ty = self.check_expr_with_expectation(
2529 expected.unwrap_or(ExpectHasType(formal_ty)));
2531 // 2. Coerce to the most detailed type that could be coerced
2532 // to, which is `expected_ty` if `rvalue_hint` returns an
2533 // `ExpectHasType(expected_ty)`, or the `formal_ty` otherwise.
2534 let coerce_ty = expected.and_then(|e| e.only_has_type(self));
2535 self.demand_coerce(&arg, checked_ty, coerce_ty.unwrap_or(formal_ty));
2537 // 3. Relate the expected type and the formal one,
2538 // if the expected type was used for the coercion.
2539 coerce_ty.map(|ty| self.demand_suptype(arg.span, formal_ty, ty));
2543 // We also need to make sure we at least write the ty of the other
2544 // arguments which we skipped above.
2546 for arg in args.iter().skip(expected_arg_count) {
2547 let arg_ty = self.check_expr(&arg);
2549 // There are a few types which get autopromoted when passed via varargs
2550 // in C but we just error out instead and require explicit casts.
2551 let arg_ty = self.structurally_resolved_type(arg.span,
2554 ty::TyFloat(ast::FloatTy::F32) => {
2555 self.type_error_message(arg.span, |t| {
2556 format!("can't pass an `{}` to variadic \
2557 function, cast to `c_double`", t)
2560 ty::TyInt(ast::IntTy::I8) | ty::TyInt(ast::IntTy::I16) | ty::TyBool => {
2561 self.type_error_message(arg.span, |t| {
2562 format!("can't pass `{}` to variadic \
2563 function, cast to `c_int`",
2567 ty::TyUint(ast::UintTy::U8) | ty::TyUint(ast::UintTy::U16) => {
2568 self.type_error_message(arg.span, |t| {
2569 format!("can't pass `{}` to variadic \
2570 function, cast to `c_uint`",
2574 ty::TyFnDef(.., f) => {
2575 let ptr_ty = self.tcx.mk_fn_ptr(f);
2576 let ptr_ty = self.resolve_type_vars_if_possible(&ptr_ty);
2577 self.type_error_message(arg.span,
2579 format!("can't pass `{}` to variadic \
2580 function, cast to `{}`", t, ptr_ty)
2589 fn err_args(&self, len: usize) -> Vec<Ty<'tcx>> {
2590 (0..len).map(|_| self.tcx.types.err).collect()
2593 // AST fragment checking
2596 expected: Expectation<'tcx>)
2602 ast::LitKind::Str(..) => tcx.mk_static_str(),
2603 ast::LitKind::ByteStr(ref v) => {
2604 tcx.mk_imm_ref(tcx.types.re_static,
2605 tcx.mk_array(tcx.types.u8, v.len()))
2607 ast::LitKind::Byte(_) => tcx.types.u8,
2608 ast::LitKind::Char(_) => tcx.types.char,
2609 ast::LitKind::Int(_, ast::LitIntType::Signed(t)) => tcx.mk_mach_int(t),
2610 ast::LitKind::Int(_, ast::LitIntType::Unsigned(t)) => tcx.mk_mach_uint(t),
2611 ast::LitKind::Int(_, ast::LitIntType::Unsuffixed) => {
2612 let opt_ty = expected.to_option(self).and_then(|ty| {
2614 ty::TyInt(_) | ty::TyUint(_) => Some(ty),
2615 ty::TyChar => Some(tcx.types.u8),
2616 ty::TyRawPtr(..) => Some(tcx.types.usize),
2617 ty::TyFnDef(..) | ty::TyFnPtr(_) => Some(tcx.types.usize),
2621 opt_ty.unwrap_or_else(
2622 || tcx.mk_int_var(self.next_int_var_id()))
2624 ast::LitKind::Float(_, t) => tcx.mk_mach_float(t),
2625 ast::LitKind::FloatUnsuffixed(_) => {
2626 let opt_ty = expected.to_option(self).and_then(|ty| {
2628 ty::TyFloat(_) => Some(ty),
2632 opt_ty.unwrap_or_else(
2633 || tcx.mk_float_var(self.next_float_var_id()))
2635 ast::LitKind::Bool(_) => tcx.types.bool
2639 fn check_expr_eq_type(&self,
2640 expr: &'gcx hir::Expr,
2641 expected: Ty<'tcx>) {
2642 let ty = self.check_expr_with_hint(expr, expected);
2643 self.demand_eqtype(expr.span, expected, ty);
2646 pub fn check_expr_has_type(&self,
2647 expr: &'gcx hir::Expr,
2648 expected: Ty<'tcx>) -> Ty<'tcx> {
2649 let mut ty = self.check_expr_with_hint(expr, expected);
2651 // While we don't allow *arbitrary* coercions here, we *do* allow
2652 // coercions from ! to `expected`.
2654 assert!(!self.tables.borrow().adjustments.contains_key(&expr.id),
2655 "expression with never type wound up being adjusted");
2656 let adj_ty = self.next_diverging_ty_var(
2657 TypeVariableOrigin::AdjustmentType(expr.span));
2658 self.apply_adjustments(expr, vec![Adjustment {
2659 kind: Adjust::NeverToAny,
2665 self.demand_suptype(expr.span, expected, ty);
2669 fn check_expr_coercable_to_type(&self,
2670 expr: &'gcx hir::Expr,
2671 expected: Ty<'tcx>) -> Ty<'tcx> {
2672 let ty = self.check_expr_with_hint(expr, expected);
2673 self.demand_coerce(expr, ty, expected);
2677 fn check_expr_with_hint(&self, expr: &'gcx hir::Expr,
2678 expected: Ty<'tcx>) -> Ty<'tcx> {
2679 self.check_expr_with_expectation(expr, ExpectHasType(expected))
2682 fn check_expr_with_expectation(&self,
2683 expr: &'gcx hir::Expr,
2684 expected: Expectation<'tcx>) -> Ty<'tcx> {
2685 self.check_expr_with_expectation_and_lvalue_pref(expr, expected, NoPreference)
2688 fn check_expr(&self, expr: &'gcx hir::Expr) -> Ty<'tcx> {
2689 self.check_expr_with_expectation(expr, NoExpectation)
2692 fn check_expr_with_lvalue_pref(&self, expr: &'gcx hir::Expr,
2693 lvalue_pref: LvaluePreference) -> Ty<'tcx> {
2694 self.check_expr_with_expectation_and_lvalue_pref(expr, NoExpectation, lvalue_pref)
2697 // determine the `self` type, using fresh variables for all variables
2698 // declared on the impl declaration e.g., `impl<A,B> for Vec<(A,B)>`
2699 // would return ($0, $1) where $0 and $1 are freshly instantiated type
2701 pub fn impl_self_ty(&self,
2702 span: Span, // (potential) receiver for this impl
2704 -> TypeAndSubsts<'tcx> {
2705 let ity = self.tcx.type_of(did);
2706 debug!("impl_self_ty: ity={:?}", ity);
2708 let substs = self.fresh_substs_for_item(span, did);
2709 let substd_ty = self.instantiate_type_scheme(span, &substs, &ity);
2711 TypeAndSubsts { substs: substs, ty: substd_ty }
2714 /// Unifies the output type with the expected type early, for more coercions
2715 /// and forward type information on the input expressions.
2716 fn expected_inputs_for_expected_output(&self,
2718 expected_ret: Expectation<'tcx>,
2719 formal_ret: Ty<'tcx>,
2720 formal_args: &[Ty<'tcx>])
2722 let expected_args = expected_ret.only_has_type(self).and_then(|ret_ty| {
2723 self.fudge_regions_if_ok(&RegionVariableOrigin::Coercion(call_span), || {
2724 // Attempt to apply a subtyping relationship between the formal
2725 // return type (likely containing type variables if the function
2726 // is polymorphic) and the expected return type.
2727 // No argument expectations are produced if unification fails.
2728 let origin = self.misc(call_span);
2729 let ures = self.at(&origin, self.param_env).sup(ret_ty, formal_ret);
2731 // FIXME(#15760) can't use try! here, FromError doesn't default
2732 // to identity so the resulting type is not constrained.
2735 // Process any obligations locally as much as
2736 // we can. We don't care if some things turn
2737 // out unconstrained or ambiguous, as we're
2738 // just trying to get hints here.
2739 let result = self.save_and_restore_in_snapshot_flag(|_| {
2740 let mut fulfill = FulfillmentContext::new();
2741 let ok = ok; // FIXME(#30046)
2742 for obligation in ok.obligations {
2743 fulfill.register_predicate_obligation(self, obligation);
2745 fulfill.select_where_possible(self)
2750 Err(_) => return Err(()),
2753 Err(_) => return Err(()),
2756 // Record all the argument types, with the substitutions
2757 // produced from the above subtyping unification.
2758 Ok(formal_args.iter().map(|ty| {
2759 self.resolve_type_vars_if_possible(ty)
2762 }).unwrap_or(vec![]);
2763 debug!("expected_inputs_for_expected_output(formal={:?} -> {:?}, expected={:?} -> {:?})",
2764 formal_args, formal_ret,
2765 expected_args, expected_ret);
2769 // Checks a method call.
2770 fn check_method_call(&self,
2771 expr: &'gcx hir::Expr,
2772 method_name: Spanned<ast::Name>,
2773 args: &'gcx [hir::Expr],
2775 expected: Expectation<'tcx>,
2776 lvalue_pref: LvaluePreference) -> Ty<'tcx> {
2777 let rcvr = &args[0];
2778 let rcvr_t = self.check_expr_with_lvalue_pref(&rcvr, lvalue_pref);
2780 // no need to check for bot/err -- callee does that
2781 let expr_t = self.structurally_resolved_type(expr.span, rcvr_t);
2783 let tps = tps.iter().map(|ast_ty| self.to_ty(&ast_ty)).collect::<Vec<_>>();
2784 let method = match self.lookup_method(method_name.span,
2791 self.write_method_call(expr.id, method);
2795 if method_name.node != keywords::Invalid.name() {
2796 self.report_method_error(method_name.span,
2807 // Call the generic checker.
2808 self.check_method_argument_types(method_name.span, method,
2814 fn check_return_expr(&self, return_expr: &'gcx hir::Expr) {
2818 .unwrap_or_else(|| span_bug!(return_expr.span,
2819 "check_return_expr called outside fn body"));
2821 let ret_ty = ret_coercion.borrow().expected_ty();
2822 let return_expr_ty = self.check_expr_with_hint(return_expr, ret_ty);
2823 ret_coercion.borrow_mut()
2825 &self.misc(return_expr.span),
2828 self.diverges.get());
2832 // A generic function for checking the then and else in an if
2834 fn check_then_else(&self,
2835 cond_expr: &'gcx hir::Expr,
2836 then_expr: &'gcx hir::Expr,
2837 opt_else_expr: Option<&'gcx hir::Expr>,
2839 expected: Expectation<'tcx>) -> Ty<'tcx> {
2840 let cond_ty = self.check_expr_has_type(cond_expr, self.tcx.types.bool);
2841 let cond_diverges = self.diverges.get();
2842 self.diverges.set(Diverges::Maybe);
2844 let expected = expected.adjust_for_branches(self);
2845 let then_ty = self.check_expr_with_expectation(then_expr, expected);
2846 let then_diverges = self.diverges.get();
2847 self.diverges.set(Diverges::Maybe);
2849 // We've already taken the expected type's preferences
2850 // into account when typing the `then` branch. To figure
2851 // out the initial shot at a LUB, we thus only consider
2852 // `expected` if it represents a *hard* constraint
2853 // (`only_has_type`); otherwise, we just go with a
2854 // fresh type variable.
2855 let coerce_to_ty = expected.coercion_target_type(self, sp);
2856 let mut coerce: DynamicCoerceMany = CoerceMany::new(coerce_to_ty);
2858 let if_cause = self.cause(sp, ObligationCauseCode::IfExpression);
2859 coerce.coerce(self, &if_cause, then_expr, then_ty, then_diverges);
2861 if let Some(else_expr) = opt_else_expr {
2862 let else_ty = self.check_expr_with_expectation(else_expr, expected);
2863 let else_diverges = self.diverges.get();
2865 coerce.coerce(self, &if_cause, else_expr, else_ty, else_diverges);
2867 // We won't diverge unless both branches do (or the condition does).
2868 self.diverges.set(cond_diverges | then_diverges & else_diverges);
2870 let else_cause = self.cause(sp, ObligationCauseCode::IfExpressionWithNoElse);
2871 coerce.coerce_forced_unit(self, &else_cause, &mut |_| (), true);
2873 // If the condition is false we can't diverge.
2874 self.diverges.set(cond_diverges);
2877 let result_ty = coerce.complete(self);
2878 if cond_ty.references_error() {
2885 // Check field access expressions
2886 fn check_field(&self,
2887 expr: &'gcx hir::Expr,
2888 lvalue_pref: LvaluePreference,
2889 base: &'gcx hir::Expr,
2890 field: &Spanned<ast::Name>) -> Ty<'tcx> {
2891 let expr_t = self.check_expr_with_lvalue_pref(base, lvalue_pref);
2892 let expr_t = self.structurally_resolved_type(expr.span,
2894 let mut private_candidate = None;
2895 let mut autoderef = self.autoderef(expr.span, expr_t);
2896 while let Some((base_t, _)) = autoderef.next() {
2898 ty::TyAdt(base_def, substs) if !base_def.is_enum() => {
2899 debug!("struct named {:?}", base_t);
2900 let (ident, def_scope) =
2901 self.tcx.adjust(field.node, base_def.did, self.body_id);
2902 let fields = &base_def.struct_variant().fields;
2903 if let Some(field) = fields.iter().find(|f| f.name.to_ident() == ident) {
2904 let field_ty = self.field_ty(expr.span, field, substs);
2905 if field.vis.is_accessible_from(def_scope, self.tcx) {
2906 let adjustments = autoderef.adjust_steps(lvalue_pref);
2907 self.apply_adjustments(base, adjustments);
2908 autoderef.finalize();
2910 self.tcx.check_stability(field.did, expr.id, expr.span);
2914 private_candidate = Some((base_def.did, field_ty));
2920 autoderef.unambiguous_final_ty();
2922 if let Some((did, field_ty)) = private_candidate {
2923 let struct_path = self.tcx().item_path_str(did);
2924 let msg = format!("field `{}` of struct `{}` is private", field.node, struct_path);
2925 let mut err = self.tcx().sess.struct_span_err(expr.span, &msg);
2926 // Also check if an accessible method exists, which is often what is meant.
2927 if self.method_exists(field.span, field.node, expr_t, expr.id, false) {
2928 err.note(&format!("a method `{}` also exists, perhaps you wish to call it",
2933 } else if field.node == keywords::Invalid.name() {
2934 self.tcx().types.err
2935 } else if self.method_exists(field.span, field.node, expr_t, expr.id, true) {
2936 self.type_error_struct(field.span, |actual| {
2937 format!("attempted to take value of method `{}` on type \
2938 `{}`", field.node, actual)
2940 .help("maybe a `()` to call it is missing? \
2941 If not, try an anonymous function")
2943 self.tcx().types.err
2945 let mut err = self.type_error_struct(field.span, |actual| {
2946 format!("no field `{}` on type `{}`",
2950 ty::TyAdt(def, _) if !def.is_enum() => {
2951 if let Some(suggested_field_name) =
2952 Self::suggest_field_name(def.struct_variant(), field, vec![]) {
2953 err.span_label(field.span,
2954 format!("did you mean `{}`?", suggested_field_name));
2956 err.span_label(field.span,
2960 ty::TyRawPtr(..) => {
2961 err.note(&format!("`{0}` is a native pointer; perhaps you need to deref with \
2963 self.tcx.hir.node_to_pretty_string(base.id),
2969 self.tcx().types.err
2973 // Return an hint about the closest match in field names
2974 fn suggest_field_name(variant: &'tcx ty::VariantDef,
2975 field: &Spanned<ast::Name>,
2976 skip : Vec<InternedString>)
2978 let name = field.node.as_str();
2979 let names = variant.fields.iter().filter_map(|field| {
2980 // ignore already set fields and private fields from non-local crates
2981 if skip.iter().any(|x| *x == field.name.as_str()) ||
2982 (variant.did.krate != LOCAL_CRATE && field.vis != Visibility::Public) {
2989 // only find fits with at least one matching letter
2990 find_best_match_for_name(names, &name, Some(name.len()))
2993 // Check tuple index expressions
2994 fn check_tup_field(&self,
2995 expr: &'gcx hir::Expr,
2996 lvalue_pref: LvaluePreference,
2997 base: &'gcx hir::Expr,
2998 idx: codemap::Spanned<usize>) -> Ty<'tcx> {
2999 let expr_t = self.check_expr_with_lvalue_pref(base, lvalue_pref);
3000 let expr_t = self.structurally_resolved_type(expr.span,
3002 let mut private_candidate = None;
3003 let mut tuple_like = false;
3004 let mut autoderef = self.autoderef(expr.span, expr_t);
3005 while let Some((base_t, _)) = autoderef.next() {
3006 let field = match base_t.sty {
3007 ty::TyAdt(base_def, substs) if base_def.is_struct() => {
3008 tuple_like = base_def.struct_variant().ctor_kind == CtorKind::Fn;
3009 if !tuple_like { continue }
3011 debug!("tuple struct named {:?}", base_t);
3012 let ident = ast::Ident {
3013 name: Symbol::intern(&idx.node.to_string()),
3014 ctxt: idx.span.ctxt.modern(),
3016 let (ident, def_scope) =
3017 self.tcx.adjust_ident(ident, base_def.did, self.body_id);
3018 let fields = &base_def.struct_variant().fields;
3019 if let Some(field) = fields.iter().find(|f| f.name.to_ident() == ident) {
3020 let field_ty = self.field_ty(expr.span, field, substs);
3021 if field.vis.is_accessible_from(def_scope, self.tcx) {
3022 self.tcx.check_stability(field.did, expr.id, expr.span);
3025 private_candidate = Some((base_def.did, field_ty));
3032 ty::TyTuple(ref v, _) => {
3034 v.get(idx.node).cloned()
3039 if let Some(field_ty) = field {
3040 let adjustments = autoderef.adjust_steps(lvalue_pref);
3041 self.apply_adjustments(base, adjustments);
3042 autoderef.finalize();
3046 autoderef.unambiguous_final_ty();
3048 if let Some((did, field_ty)) = private_candidate {
3049 let struct_path = self.tcx().item_path_str(did);
3050 let msg = format!("field `{}` of struct `{}` is private", idx.node, struct_path);
3051 self.tcx().sess.span_err(expr.span, &msg);
3055 self.type_error_message(
3059 format!("attempted out-of-bounds tuple index `{}` on \
3064 format!("attempted tuple index `{}` on type `{}`, but the \
3065 type was not a tuple or tuple struct",
3072 self.tcx().types.err
3075 fn report_unknown_field(&self,
3077 variant: &'tcx ty::VariantDef,
3079 skip_fields: &[hir::Field],
3081 let mut err = self.type_error_struct_with_diag(
3083 |actual| match ty.sty {
3084 ty::TyAdt(adt, ..) if adt.is_enum() => {
3085 struct_span_err!(self.tcx.sess, field.name.span, E0559,
3086 "{} `{}::{}` has no field named `{}`",
3087 kind_name, actual, variant.name, field.name.node)
3090 struct_span_err!(self.tcx.sess, field.name.span, E0560,
3091 "{} `{}` has no field named `{}`",
3092 kind_name, actual, field.name.node)
3096 // prevent all specified fields from being suggested
3097 let skip_fields = skip_fields.iter().map(|ref x| x.name.node.as_str());
3098 if let Some(field_name) = Self::suggest_field_name(variant,
3100 skip_fields.collect()) {
3101 err.span_label(field.name.span,
3102 format!("field does not exist - did you mean `{}`?", field_name));
3105 ty::TyAdt(adt, ..) if adt.is_enum() => {
3106 err.span_label(field.name.span, format!("`{}::{}` does not have this field",
3110 err.span_label(field.name.span, format!("`{}` does not have this field", ty));
3117 fn check_expr_struct_fields(&self,
3119 expected: Expectation<'tcx>,
3120 expr_id: ast::NodeId,
3122 variant: &'tcx ty::VariantDef,
3123 ast_fields: &'gcx [hir::Field],
3124 check_completeness: bool) {
3128 self.expected_inputs_for_expected_output(span, expected, adt_ty, &[adt_ty])
3129 .get(0).cloned().unwrap_or(adt_ty);
3131 let (substs, hint_substs, adt_kind, kind_name) = match (&adt_ty.sty, &adt_ty_hint.sty) {
3132 (&ty::TyAdt(adt, substs), &ty::TyAdt(_, hint_substs)) => {
3133 (substs, hint_substs, adt.adt_kind(), adt.variant_descr())
3135 _ => span_bug!(span, "non-ADT passed to check_expr_struct_fields")
3138 let mut remaining_fields = FxHashMap();
3139 for field in &variant.fields {
3140 remaining_fields.insert(field.name.to_ident(), field);
3143 let mut seen_fields = FxHashMap();
3145 let mut error_happened = false;
3147 // Typecheck each field.
3148 for field in ast_fields {
3149 let final_field_type;
3150 let field_type_hint;
3152 let ident = tcx.adjust(field.name.node, variant.did, self.body_id).0;
3153 if let Some(v_field) = remaining_fields.remove(&ident) {
3154 final_field_type = self.field_ty(field.span, v_field, substs);
3155 field_type_hint = self.field_ty(field.span, v_field, hint_substs);
3157 seen_fields.insert(field.name.node, field.span);
3159 // we don't look at stability attributes on
3160 // struct-like enums (yet...), but it's definitely not
3161 // a bug to have construct one.
3162 if adt_kind != ty::AdtKind::Enum {
3163 tcx.check_stability(v_field.did, expr_id, field.span);
3166 error_happened = true;
3167 final_field_type = tcx.types.err;
3168 field_type_hint = tcx.types.err;
3169 if let Some(_) = variant.find_field_named(field.name.node) {
3170 let mut err = struct_span_err!(self.tcx.sess,
3173 "field `{}` specified more than once",
3176 err.span_label(field.name.span, "used more than once");
3178 if let Some(prev_span) = seen_fields.get(&field.name.node) {
3179 err.span_label(*prev_span, format!("first use of `{}`", field.name.node));
3184 self.report_unknown_field(adt_ty, variant, field, ast_fields, kind_name);
3188 // Make sure to give a type to the field even if there's
3189 // an error, so we can continue typechecking
3190 let ty = self.check_expr_with_hint(&field.expr, field_type_hint);
3191 self.demand_coerce(&field.expr, ty, final_field_type);
3194 // Make sure the programmer specified correct number of fields.
3195 if kind_name == "union" {
3196 if ast_fields.len() != 1 {
3197 tcx.sess.span_err(span, "union expressions should have exactly one field");
3199 } else if check_completeness && !error_happened && !remaining_fields.is_empty() {
3200 let len = remaining_fields.len();
3202 let mut displayable_field_names = remaining_fields
3204 .map(|ident| ident.name.as_str())
3205 .collect::<Vec<_>>();
3207 displayable_field_names.sort();
3209 let truncated_fields_error = if len <= 3 {
3212 format!(" and {} other field{}", (len - 3), if len - 3 == 1 {""} else {"s"})
3215 let remaining_fields_names = displayable_field_names.iter().take(3)
3216 .map(|n| format!("`{}`", n))
3217 .collect::<Vec<_>>()
3220 struct_span_err!(tcx.sess, span, E0063,
3221 "missing field{} {}{} in initializer of `{}`",
3222 if remaining_fields.len() == 1 {""} else {"s"},
3223 remaining_fields_names,
3224 truncated_fields_error,
3226 .span_label(span, format!("missing {}{}",
3227 remaining_fields_names,
3228 truncated_fields_error))
3233 fn check_struct_fields_on_error(&self,
3234 fields: &'gcx [hir::Field],
3235 base_expr: &'gcx Option<P<hir::Expr>>) {
3236 for field in fields {
3237 self.check_expr(&field.expr);
3241 self.check_expr(&base);
3247 pub fn check_struct_path(&self,
3249 node_id: ast::NodeId)
3250 -> Option<(&'tcx ty::VariantDef, Ty<'tcx>)> {
3251 let path_span = match *qpath {
3252 hir::QPath::Resolved(_, ref path) => path.span,
3253 hir::QPath::TypeRelative(ref qself, _) => qself.span
3255 let (def, ty) = self.finish_resolving_struct_path(qpath, path_span, node_id);
3256 let variant = match def {
3258 self.set_tainted_by_errors();
3261 Def::Variant(..) => {
3263 ty::TyAdt(adt, substs) => {
3264 Some((adt.variant_of_def(def), adt.did, substs))
3266 _ => bug!("unexpected type: {:?}", ty.sty)
3269 Def::Struct(..) | Def::Union(..) | Def::TyAlias(..) |
3270 Def::AssociatedTy(..) | Def::SelfTy(..) => {
3272 ty::TyAdt(adt, substs) if !adt.is_enum() => {
3273 Some((adt.struct_variant(), adt.did, substs))
3278 _ => bug!("unexpected definition: {:?}", def)
3281 if let Some((variant, did, substs)) = variant {
3282 // Check bounds on type arguments used in the path.
3283 let bounds = self.instantiate_bounds(path_span, did, substs);
3284 let cause = traits::ObligationCause::new(path_span, self.body_id,
3285 traits::ItemObligation(did));
3286 self.add_obligations_for_parameters(cause, &bounds);
3290 struct_span_err!(self.tcx.sess, path_span, E0071,
3291 "expected struct, variant or union type, found {}",
3292 ty.sort_string(self.tcx))
3293 .span_label(path_span, "not a struct")
3299 fn check_expr_struct(&self,
3301 expected: Expectation<'tcx>,
3303 fields: &'gcx [hir::Field],
3304 base_expr: &'gcx Option<P<hir::Expr>>) -> Ty<'tcx>
3306 // Find the relevant variant
3307 let (variant, struct_ty) =
3308 if let Some(variant_ty) = self.check_struct_path(qpath, expr.id) {
3311 self.check_struct_fields_on_error(fields, base_expr);
3312 return self.tcx.types.err;
3315 let path_span = match *qpath {
3316 hir::QPath::Resolved(_, ref path) => path.span,
3317 hir::QPath::TypeRelative(ref qself, _) => qself.span
3320 self.check_expr_struct_fields(struct_ty, expected, expr.id, path_span, variant, fields,
3321 base_expr.is_none());
3322 if let &Some(ref base_expr) = base_expr {
3323 self.check_expr_has_type(base_expr, struct_ty);
3324 match struct_ty.sty {
3325 ty::TyAdt(adt, substs) if adt.is_struct() => {
3326 self.tables.borrow_mut().fru_field_types.insert(
3328 adt.struct_variant().fields.iter().map(|f| {
3329 self.normalize_associated_types_in(
3330 expr.span, &f.ty(self.tcx, substs)
3336 span_err!(self.tcx.sess, base_expr.span, E0436,
3337 "functional record update syntax requires a struct");
3341 self.require_type_is_sized(struct_ty, expr.span, traits::StructInitializerSized);
3347 /// If an expression has any sub-expressions that result in a type error,
3348 /// inspecting that expression's type with `ty.references_error()` will return
3349 /// true. Likewise, if an expression is known to diverge, inspecting its
3350 /// type with `ty::type_is_bot` will return true (n.b.: since Rust is
3351 /// strict, _|_ can appear in the type of an expression that does not,
3352 /// itself, diverge: for example, fn() -> _|_.)
3353 /// Note that inspecting a type's structure *directly* may expose the fact
3354 /// that there are actually multiple representations for `TyError`, so avoid
3355 /// that when err needs to be handled differently.
3356 fn check_expr_with_expectation_and_lvalue_pref(&self,
3357 expr: &'gcx hir::Expr,
3358 expected: Expectation<'tcx>,
3359 lvalue_pref: LvaluePreference) -> Ty<'tcx> {
3360 debug!(">> typechecking: expr={:?} expected={:?}",
3363 // Warn for expressions after diverging siblings.
3364 self.warn_if_unreachable(expr.id, expr.span, "expression");
3366 // Hide the outer diverging and has_errors flags.
3367 let old_diverges = self.diverges.get();
3368 let old_has_errors = self.has_errors.get();
3369 self.diverges.set(Diverges::Maybe);
3370 self.has_errors.set(false);
3372 let ty = self.check_expr_kind(expr, expected, lvalue_pref);
3374 // Warn for non-block expressions with diverging children.
3377 hir::ExprLoop(..) | hir::ExprWhile(..) |
3378 hir::ExprIf(..) | hir::ExprMatch(..) => {}
3380 _ => self.warn_if_unreachable(expr.id, expr.span, "expression")
3383 // Any expression that produces a value of type `!` must have diverged
3385 self.diverges.set(self.diverges.get() | Diverges::Always);
3388 // Record the type, which applies it effects.
3389 // We need to do this after the warning above, so that
3390 // we don't warn for the diverging expression itself.
3391 self.write_ty(expr.id, ty);
3393 // Combine the diverging and has_error flags.
3394 self.diverges.set(self.diverges.get() | old_diverges);
3395 self.has_errors.set(self.has_errors.get() | old_has_errors);
3397 debug!("type of {} is...", self.tcx.hir.node_to_string(expr.id));
3398 debug!("... {:?}, expected is {:?}", ty, expected);
3403 fn check_expr_kind(&self,
3404 expr: &'gcx hir::Expr,
3405 expected: Expectation<'tcx>,
3406 lvalue_pref: LvaluePreference) -> Ty<'tcx> {
3410 hir::ExprBox(ref subexpr) => {
3411 let expected_inner = expected.to_option(self).map_or(NoExpectation, |ty| {
3413 ty::TyAdt(def, _) if def.is_box()
3414 => Expectation::rvalue_hint(self, ty.boxed_ty()),
3418 let referent_ty = self.check_expr_with_expectation(subexpr, expected_inner);
3419 tcx.mk_box(referent_ty)
3422 hir::ExprLit(ref lit) => {
3423 self.check_lit(&lit, expected)
3425 hir::ExprBinary(op, ref lhs, ref rhs) => {
3426 self.check_binop(expr, op, lhs, rhs)
3428 hir::ExprAssignOp(op, ref lhs, ref rhs) => {
3429 self.check_binop_assign(expr, op, lhs, rhs)
3431 hir::ExprUnary(unop, ref oprnd) => {
3432 let expected_inner = match unop {
3433 hir::UnNot | hir::UnNeg => {
3440 let lvalue_pref = match unop {
3441 hir::UnDeref => lvalue_pref,
3444 let mut oprnd_t = self.check_expr_with_expectation_and_lvalue_pref(&oprnd,
3448 if !oprnd_t.references_error() {
3449 oprnd_t = self.structurally_resolved_type(expr.span, oprnd_t);
3452 if let Some(mt) = oprnd_t.builtin_deref(true, NoPreference) {
3454 } else if let Some(ok) = self.try_overloaded_deref(
3455 expr.span, oprnd_t, lvalue_pref) {
3456 let method = self.register_infer_ok_obligations(ok);
3457 if let ty::TyRef(region, mt) = method.sig.inputs()[0].sty {
3458 self.apply_adjustments(oprnd, vec![Adjustment {
3459 kind: Adjust::Borrow(AutoBorrow::Ref(region, mt.mutbl)),
3460 target: method.sig.inputs()[0]
3463 oprnd_t = self.make_overloaded_lvalue_return_type(method).ty;
3464 self.write_method_call(expr.id, method);
3466 self.type_error_message(expr.span, |actual| {
3467 format!("type `{}` cannot be \
3468 dereferenced", actual)
3470 oprnd_t = tcx.types.err;
3474 let result = self.check_user_unop(expr, oprnd_t, unop);
3475 // If it's builtin, we can reuse the type, this helps inference.
3476 if !(oprnd_t.is_integral() || oprnd_t.sty == ty::TyBool) {
3481 let result = self.check_user_unop(expr, oprnd_t, unop);
3482 // If it's builtin, we can reuse the type, this helps inference.
3483 if !(oprnd_t.is_integral() || oprnd_t.is_fp()) {
3491 hir::ExprAddrOf(mutbl, ref oprnd) => {
3492 let hint = expected.only_has_type(self).map_or(NoExpectation, |ty| {
3494 ty::TyRef(_, ref mt) | ty::TyRawPtr(ref mt) => {
3495 if self.tcx.expr_is_lval(&oprnd) {
3496 // Lvalues may legitimately have unsized types.
3497 // For example, dereferences of a fat pointer and
3498 // the last field of a struct can be unsized.
3499 ExpectHasType(mt.ty)
3501 Expectation::rvalue_hint(self, mt.ty)
3507 let lvalue_pref = LvaluePreference::from_mutbl(mutbl);
3508 let ty = self.check_expr_with_expectation_and_lvalue_pref(&oprnd, hint, lvalue_pref);
3510 let tm = ty::TypeAndMut { ty: ty, mutbl: mutbl };
3511 if tm.ty.references_error() {
3514 // Note: at this point, we cannot say what the best lifetime
3515 // is to use for resulting pointer. We want to use the
3516 // shortest lifetime possible so as to avoid spurious borrowck
3517 // errors. Moreover, the longest lifetime will depend on the
3518 // precise details of the value whose address is being taken
3519 // (and how long it is valid), which we don't know yet until type
3520 // inference is complete.
3522 // Therefore, here we simply generate a region variable. The
3523 // region inferencer will then select the ultimate value.
3524 // Finally, borrowck is charged with guaranteeing that the
3525 // value whose address was taken can actually be made to live
3526 // as long as it needs to live.
3527 let region = self.next_region_var(infer::AddrOfRegion(expr.span));
3528 tcx.mk_ref(region, tm)
3531 hir::ExprPath(ref qpath) => {
3532 let (def, opt_ty, segments) = self.resolve_ty_and_def_ufcs(qpath,
3533 expr.id, expr.span);
3534 let ty = if def != Def::Err {
3535 self.instantiate_value_path(segments, opt_ty, def, expr.span, id)
3537 self.set_tainted_by_errors();
3541 // We always require that the type provided as the value for
3542 // a type parameter outlives the moment of instantiation.
3543 let substs = self.tables.borrow().node_substs(expr.id);
3544 self.add_wf_bounds(substs, expr);
3548 hir::ExprInlineAsm(_, ref outputs, ref inputs) => {
3549 for output in outputs {
3550 self.check_expr(output);
3552 for input in inputs {
3553 self.check_expr(input);
3557 hir::ExprBreak(destination, ref expr_opt) => {
3558 if let Some(target_id) = destination.target_id.opt_id() {
3559 let (e_ty, e_diverges, cause);
3560 if let Some(ref e) = *expr_opt {
3561 // If this is a break with a value, we need to type-check
3562 // the expression. Get an expected type from the loop context.
3563 let opt_coerce_to = {
3564 let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
3565 enclosing_breakables.find_breakable(target_id)
3568 .map(|coerce| coerce.expected_ty())
3571 // If the loop context is not a `loop { }`, then break with
3572 // a value is illegal, and `opt_coerce_to` will be `None`.
3573 // Just set expectation to error in that case.
3574 let coerce_to = opt_coerce_to.unwrap_or(tcx.types.err);
3576 // Recurse without `enclosing_breakables` borrowed.
3577 e_ty = self.check_expr_with_hint(e, coerce_to);
3578 e_diverges = self.diverges.get();
3579 cause = self.misc(e.span);
3581 // Otherwise, this is a break *without* a value. That's
3582 // always legal, and is equivalent to `break ()`.
3583 e_ty = tcx.mk_nil();
3584 e_diverges = Diverges::Maybe;
3585 cause = self.misc(expr.span);
3588 // Now that we have type-checked `expr_opt`, borrow
3589 // the `enclosing_loops` field and let's coerce the
3590 // type of `expr_opt` into what is expected.
3591 let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
3592 let ctxt = enclosing_breakables.find_breakable(target_id);
3593 if let Some(ref mut coerce) = ctxt.coerce {
3594 if let Some(ref e) = *expr_opt {
3595 coerce.coerce(self, &cause, e, e_ty, e_diverges);
3597 assert!(e_ty.is_nil());
3598 coerce.coerce_forced_unit(self, &cause, &mut |_| (), true);
3601 // If `ctxt.coerce` is `None`, we can just ignore
3602 // the type of the expresison. This is because
3603 // either this was a break *without* a value, in
3604 // which case it is always a legal type (`()`), or
3605 // else an error would have been flagged by the
3606 // `loops` pass for using break with an expression
3607 // where you are not supposed to.
3608 assert!(expr_opt.is_none() || self.tcx.sess.err_count() > 0);
3611 ctxt.may_break = true;
3613 // Otherwise, we failed to find the enclosing loop;
3614 // this can only happen if the `break` was not
3615 // inside a loop at all, which is caught by the
3616 // loop-checking pass.
3617 assert!(self.tcx.sess.err_count() > 0);
3620 // the type of a `break` is always `!`, since it diverges
3623 hir::ExprAgain(_) => { tcx.types.never }
3624 hir::ExprRet(ref expr_opt) => {
3625 if self.ret_coercion.is_none() {
3626 struct_span_err!(self.tcx.sess, expr.span, E0572,
3627 "return statement outside of function body").emit();
3628 } else if let Some(ref e) = *expr_opt {
3629 self.check_return_expr(e);
3631 let mut coercion = self.ret_coercion.as_ref().unwrap().borrow_mut();
3632 let cause = self.cause(expr.span, ObligationCauseCode::ReturnNoExpression);
3633 coercion.coerce_forced_unit(self, &cause, &mut |_| (), true);
3637 hir::ExprAssign(ref lhs, ref rhs) => {
3638 let lhs_ty = self.check_expr_with_lvalue_pref(&lhs, PreferMutLvalue);
3641 if !tcx.expr_is_lval(&lhs) {
3643 tcx.sess, expr.span, E0070,
3644 "invalid left-hand side expression")
3647 "left-hand of expression not valid")
3651 let rhs_ty = self.check_expr_coercable_to_type(&rhs, lhs_ty);
3653 self.require_type_is_sized(lhs_ty, lhs.span, traits::AssignmentLhsSized);
3655 if lhs_ty.references_error() || rhs_ty.references_error() {
3661 hir::ExprIf(ref cond, ref then_expr, ref opt_else_expr) => {
3662 self.check_then_else(&cond, then_expr, opt_else_expr.as_ref().map(|e| &**e),
3663 expr.span, expected)
3665 hir::ExprWhile(ref cond, ref body, _) => {
3666 let ctxt = BreakableCtxt {
3667 // cannot use break with a value from a while loop
3672 self.with_breakable_ctxt(expr.id, ctxt, || {
3673 self.check_expr_has_type(&cond, tcx.types.bool);
3674 let cond_diverging = self.diverges.get();
3675 self.check_block_no_value(&body);
3677 // We may never reach the body so it diverging means nothing.
3678 self.diverges.set(cond_diverging);
3683 hir::ExprLoop(ref body, _, source) => {
3684 let coerce = match source {
3685 // you can only use break with a value from a normal `loop { }`
3686 hir::LoopSource::Loop => {
3687 let coerce_to = expected.coercion_target_type(self, body.span);
3688 Some(CoerceMany::new(coerce_to))
3691 hir::LoopSource::WhileLet |
3692 hir::LoopSource::ForLoop => {
3697 let ctxt = BreakableCtxt {
3699 may_break: false, // will get updated if/when we find a `break`
3702 let (ctxt, ()) = self.with_breakable_ctxt(expr.id, ctxt, || {
3703 self.check_block_no_value(&body);
3707 // No way to know whether it's diverging because
3708 // of a `break` or an outer `break` or `return.
3709 self.diverges.set(Diverges::Maybe);
3712 // If we permit break with a value, then result type is
3713 // the LUB of the breaks (possibly ! if none); else, it
3714 // is nil. This makes sense because infinite loops
3715 // (which would have type !) are only possible iff we
3716 // permit break with a value [1].
3717 assert!(ctxt.coerce.is_some() || ctxt.may_break); // [1]
3718 ctxt.coerce.map(|c| c.complete(self)).unwrap_or(self.tcx.mk_nil())
3720 hir::ExprMatch(ref discrim, ref arms, match_src) => {
3721 self.check_match(expr, &discrim, arms, expected, match_src)
3723 hir::ExprClosure(capture, ref decl, body_id, _) => {
3724 self.check_expr_closure(expr, capture, &decl, body_id, expected)
3726 hir::ExprBlock(ref body) => {
3727 self.check_block_with_expected(&body, expected)
3729 hir::ExprCall(ref callee, ref args) => {
3730 self.check_call(expr, &callee, args, expected)
3732 hir::ExprMethodCall(name, ref tps, ref args) => {
3733 self.check_method_call(expr, name, args, &tps[..], expected, lvalue_pref)
3735 hir::ExprCast(ref e, ref t) => {
3736 // Find the type of `e`. Supply hints based on the type we are casting to,
3738 let t_cast = self.to_ty(t);
3739 let t_cast = self.resolve_type_vars_if_possible(&t_cast);
3740 let t_expr = self.check_expr_with_expectation(e, ExpectCastableToType(t_cast));
3741 let t_cast = self.resolve_type_vars_if_possible(&t_cast);
3742 let diverges = self.diverges.get();
3744 // Eagerly check for some obvious errors.
3745 if t_expr.references_error() || t_cast.references_error() {
3748 // Defer other checks until we're done type checking.
3749 let mut deferred_cast_checks = self.deferred_cast_checks.borrow_mut();
3750 match cast::CastCheck::new(self, e, t_expr, diverges, t_cast, t.span, expr.span) {
3752 deferred_cast_checks.push(cast_check);
3755 Err(ErrorReported) => {
3761 hir::ExprType(ref e, ref t) => {
3762 let typ = self.to_ty(&t);
3763 self.check_expr_eq_type(&e, typ);
3766 hir::ExprArray(ref args) => {
3767 let uty = expected.to_option(self).and_then(|uty| {
3769 ty::TyArray(ty, _) | ty::TySlice(ty) => Some(ty),
3774 let element_ty = if !args.is_empty() {
3775 let coerce_to = uty.unwrap_or_else(
3776 || self.next_ty_var(TypeVariableOrigin::TypeInference(expr.span)));
3777 let mut coerce = CoerceMany::with_coercion_sites(coerce_to, args);
3778 assert_eq!(self.diverges.get(), Diverges::Maybe);
3780 let e_ty = self.check_expr_with_hint(e, coerce_to);
3781 let cause = self.misc(e.span);
3782 coerce.coerce(self, &cause, e, e_ty, self.diverges.get());
3784 coerce.complete(self)
3786 self.next_ty_var(TypeVariableOrigin::TypeInference(expr.span))
3788 tcx.mk_array(element_ty, args.len())
3790 hir::ExprRepeat(ref element, count) => {
3791 let count = eval_length(self.tcx, count, "repeat count")
3794 let uty = match expected {
3795 ExpectHasType(uty) => {
3797 ty::TyArray(ty, _) | ty::TySlice(ty) => Some(ty),
3804 let (element_ty, t) = match uty {
3806 self.check_expr_coercable_to_type(&element, uty);
3810 let t: Ty = self.next_ty_var(TypeVariableOrigin::MiscVariable(element.span));
3811 let element_ty = self.check_expr_has_type(&element, t);
3817 // For [foo, ..n] where n > 1, `foo` must have
3819 let lang_item = self.tcx.require_lang_item(lang_items::CopyTraitLangItem);
3820 self.require_type_meets(t, expr.span, traits::RepeatVec, lang_item);
3823 if element_ty.references_error() {
3826 tcx.mk_array(t, count)
3829 hir::ExprTup(ref elts) => {
3830 let flds = expected.only_has_type(self).and_then(|ty| {
3832 ty::TyTuple(ref flds, _) => Some(&flds[..]),
3837 let elt_ts_iter = elts.iter().enumerate().map(|(i, e)| {
3838 let t = match flds {
3839 Some(ref fs) if i < fs.len() => {
3841 self.check_expr_coercable_to_type(&e, ety);
3845 self.check_expr_with_expectation(&e, NoExpectation)
3850 let tuple = tcx.mk_tup(elt_ts_iter, false);
3851 if tuple.references_error() {
3857 hir::ExprStruct(ref qpath, ref fields, ref base_expr) => {
3858 self.check_expr_struct(expr, expected, qpath, fields, base_expr)
3860 hir::ExprField(ref base, ref field) => {
3861 self.check_field(expr, lvalue_pref, &base, field)
3863 hir::ExprTupField(ref base, idx) => {
3864 self.check_tup_field(expr, lvalue_pref, &base, idx)
3866 hir::ExprIndex(ref base, ref idx) => {
3867 let base_t = self.check_expr_with_lvalue_pref(&base, lvalue_pref);
3868 let idx_t = self.check_expr(&idx);
3870 if base_t.references_error() {
3872 } else if idx_t.references_error() {
3875 let base_t = self.structurally_resolved_type(expr.span, base_t);
3876 match self.lookup_indexing(expr, base, base_t, idx_t, lvalue_pref) {
3877 Some((index_ty, element_ty)) => {
3878 self.demand_coerce(idx, idx_t, index_ty);
3882 let mut err = self.type_error_struct(
3885 format!("cannot index a value of type `{}`",
3889 // Try to give some advice about indexing tuples.
3890 if let ty::TyTuple(..) = base_t.sty {
3891 let mut needs_note = true;
3892 // If the index is an integer, we can show the actual
3893 // fixed expression:
3894 if let hir::ExprLit(ref lit) = idx.node {
3895 if let ast::LitKind::Int(i,
3896 ast::LitIntType::Unsuffixed) = lit.node {
3897 let snip = tcx.sess.codemap().span_to_snippet(base.span);
3898 if let Ok(snip) = snip {
3899 err.span_suggestion(expr.span,
3900 "to access tuple elements, use",
3901 format!("{}.{}", snip, i));
3907 err.help("to access tuple elements, use tuple indexing \
3908 syntax (e.g. `tuple.0`)");
3920 // Finish resolving a path in a struct expression or pattern `S::A { .. }` if necessary.
3921 // The newly resolved definition is written into `type_dependent_defs`.
3922 fn finish_resolving_struct_path(&self,
3925 node_id: ast::NodeId)
3929 hir::QPath::Resolved(ref maybe_qself, ref path) => {
3930 let opt_self_ty = maybe_qself.as_ref().map(|qself| self.to_ty(qself));
3931 let ty = AstConv::def_to_ty(self, opt_self_ty, path, true);
3934 hir::QPath::TypeRelative(ref qself, ref segment) => {
3935 let ty = self.to_ty(qself);
3937 let def = if let hir::TyPath(hir::QPath::Resolved(_, ref path)) = qself.node {
3942 let (ty, def) = AstConv::associated_path_def_to_ty(self, node_id, path_span,
3945 // Write back the new resolution.
3946 self.tables.borrow_mut().type_dependent_defs.insert(node_id, def);
3953 // Resolve associated value path into a base type and associated constant or method definition.
3954 // The newly resolved definition is written into `type_dependent_defs`.
3955 pub fn resolve_ty_and_def_ufcs<'b>(&self,
3956 qpath: &'b hir::QPath,
3957 node_id: ast::NodeId,
3959 -> (Def, Option<Ty<'tcx>>, &'b [hir::PathSegment])
3961 let (ty, item_segment) = match *qpath {
3962 hir::QPath::Resolved(ref opt_qself, ref path) => {
3964 opt_qself.as_ref().map(|qself| self.to_ty(qself)),
3965 &path.segments[..]);
3967 hir::QPath::TypeRelative(ref qself, ref segment) => {
3968 (self.to_ty(qself), segment)
3971 let item_name = item_segment.name;
3972 let def = match self.resolve_ufcs(span, item_name, ty, node_id) {
3975 let def = match error {
3976 method::MethodError::PrivateMatch(def) => def,
3979 if item_name != keywords::Invalid.name() {
3980 self.report_method_error(span, ty, item_name, None, error, None);
3986 // Write back the new resolution.
3987 self.tables.borrow_mut().type_dependent_defs.insert(node_id, def);
3988 (def, Some(ty), slice::ref_slice(&**item_segment))
3991 pub fn check_decl_initializer(&self,
3992 local: &'gcx hir::Local,
3993 init: &'gcx hir::Expr) -> Ty<'tcx>
3995 let ref_bindings = local.pat.contains_ref_binding();
3997 let local_ty = self.local_ty(init.span, local.id);
3998 if let Some(m) = ref_bindings {
3999 // Somewhat subtle: if we have a `ref` binding in the pattern,
4000 // we want to avoid introducing coercions for the RHS. This is
4001 // both because it helps preserve sanity and, in the case of
4002 // ref mut, for soundness (issue #23116). In particular, in
4003 // the latter case, we need to be clear that the type of the
4004 // referent for the reference that results is *equal to* the
4005 // type of the lvalue it is referencing, and not some
4006 // supertype thereof.
4007 let init_ty = self.check_expr_with_lvalue_pref(init, LvaluePreference::from_mutbl(m));
4008 self.demand_eqtype(init.span, init_ty, local_ty);
4011 self.check_expr_coercable_to_type(init, local_ty)
4015 pub fn check_decl_local(&self, local: &'gcx hir::Local) {
4016 let t = self.local_ty(local.span, local.id);
4017 self.write_ty(local.id, t);
4019 if let Some(ref init) = local.init {
4020 let init_ty = self.check_decl_initializer(local, &init);
4021 if init_ty.references_error() {
4022 self.write_ty(local.id, init_ty);
4026 self.check_pat(&local.pat, t);
4027 let pat_ty = self.node_ty(local.pat.id);
4028 if pat_ty.references_error() {
4029 self.write_ty(local.id, pat_ty);
4033 pub fn check_stmt(&self, stmt: &'gcx hir::Stmt) {
4034 // Don't do all the complex logic below for DeclItem.
4036 hir::StmtDecl(ref decl, id) => {
4038 hir::DeclLocal(_) => {}
4039 hir::DeclItem(_) => {
4045 hir::StmtExpr(..) | hir::StmtSemi(..) => {}
4048 self.warn_if_unreachable(stmt.node.id(), stmt.span, "statement");
4050 // Hide the outer diverging and has_errors flags.
4051 let old_diverges = self.diverges.get();
4052 let old_has_errors = self.has_errors.get();
4053 self.diverges.set(Diverges::Maybe);
4054 self.has_errors.set(false);
4056 let (node_id, _span) = match stmt.node {
4057 hir::StmtDecl(ref decl, id) => {
4058 let span = match decl.node {
4059 hir::DeclLocal(ref l) => {
4060 self.check_decl_local(&l);
4063 hir::DeclItem(_) => {/* ignore for now */
4069 hir::StmtExpr(ref expr, id) => {
4070 // Check with expected type of ()
4071 self.check_expr_has_type(&expr, self.tcx.mk_nil());
4074 hir::StmtSemi(ref expr, id) => {
4075 self.check_expr(&expr);
4080 if self.has_errors.get() {
4081 self.write_error(node_id);
4083 self.write_nil(node_id);
4086 // Combine the diverging and has_error flags.
4087 self.diverges.set(self.diverges.get() | old_diverges);
4088 self.has_errors.set(self.has_errors.get() | old_has_errors);
4091 pub fn check_block_no_value(&self, blk: &'gcx hir::Block) {
4092 let unit = self.tcx.mk_nil();
4093 let ty = self.check_block_with_expected(blk, ExpectHasType(unit));
4095 // if the block produces a `!` value, that can always be
4096 // (effectively) coerced to unit.
4098 self.demand_suptype(blk.span, unit, ty);
4102 fn check_block_with_expected(&self,
4103 blk: &'gcx hir::Block,
4104 expected: Expectation<'tcx>) -> Ty<'tcx> {
4106 let mut fcx_ps = self.ps.borrow_mut();
4107 let unsafety_state = fcx_ps.recurse(blk);
4108 replace(&mut *fcx_ps, unsafety_state)
4111 // In some cases, blocks have just one exit, but other blocks
4112 // can be targeted by multiple breaks. This cannot happen in
4113 // normal Rust syntax today, but it can happen when we desugar
4114 // a `do catch { ... }` expression.
4118 // 'a: { if true { break 'a Err(()); } Ok(()) }
4120 // Here we would wind up with two coercions, one from
4121 // `Err(())` and the other from the tail expression
4122 // `Ok(())`. If the tail expression is omitted, that's a
4123 // "forced unit" -- unless the block diverges, in which
4124 // case we can ignore the tail expression (e.g., `'a: {
4125 // break 'a 22; }` would not force the type of the block
4127 let tail_expr = blk.expr.as_ref();
4128 let coerce_to_ty = expected.coercion_target_type(self, blk.span);
4129 let coerce = if blk.targeted_by_break {
4130 CoerceMany::new(coerce_to_ty)
4132 let tail_expr: &[P<hir::Expr>] = match tail_expr {
4133 Some(e) => ref_slice(e),
4136 CoerceMany::with_coercion_sites(coerce_to_ty, tail_expr)
4139 let ctxt = BreakableCtxt {
4140 coerce: Some(coerce),
4144 let (ctxt, ()) = self.with_breakable_ctxt(blk.id, ctxt, || {
4145 for s in &blk.stmts {
4149 // check the tail expression **without** holding the
4150 // `enclosing_breakables` lock below.
4151 let tail_expr_ty = tail_expr.map(|t| self.check_expr_with_expectation(t, expected));
4153 let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
4154 let mut ctxt = enclosing_breakables.find_breakable(blk.id);
4155 let mut coerce = ctxt.coerce.as_mut().unwrap();
4156 if let Some(tail_expr_ty) = tail_expr_ty {
4157 let tail_expr = tail_expr.unwrap();
4159 &self.misc(tail_expr.span),
4162 self.diverges.get());
4164 // Subtle: if there is no explicit tail expression,
4165 // that is typically equivalent to a tail expression
4166 // of `()` -- except if the block diverges. In that
4167 // case, there is no value supplied from the tail
4168 // expression (assuming there are no other breaks,
4169 // this implies that the type of the block will be
4172 // #41425 -- label the implicit `()` as being the
4173 // "found type" here, rather than the "expected type".
4174 if !self.diverges.get().always() {
4175 coerce.coerce_forced_unit(self, &self.misc(blk.span), &mut |err| {
4176 if let Some(expected_ty) = expected.only_has_type(self) {
4177 self.consider_hint_about_removing_semicolon(blk,
4186 let mut ty = ctxt.coerce.unwrap().complete(self);
4188 if self.has_errors.get() || ty.references_error() {
4189 ty = self.tcx.types.err
4192 self.write_ty(blk.id, ty);
4194 *self.ps.borrow_mut() = prev;
4198 /// A common error is to add an extra semicolon:
4201 /// fn foo() -> usize {
4206 /// This routine checks if the final statement in a block is an
4207 /// expression with an explicit semicolon whose type is compatible
4208 /// with `expected_ty`. If so, it suggests removing the semicolon.
4209 fn consider_hint_about_removing_semicolon(&self,
4210 blk: &'gcx hir::Block,
4211 expected_ty: Ty<'tcx>,
4212 err: &mut DiagnosticBuilder) {
4213 // Be helpful when the user wrote `{... expr;}` and
4214 // taking the `;` off is enough to fix the error.
4215 let last_stmt = match blk.stmts.last() {
4219 let last_expr = match last_stmt.node {
4220 hir::StmtSemi(ref e, _) => e,
4223 let last_expr_ty = self.expr_ty(last_expr);
4224 if self.can_sub(self.param_env, last_expr_ty, expected_ty).is_err() {
4227 let original_span = original_sp(last_stmt.span, blk.span);
4228 let span_semi = Span {
4229 lo: original_span.hi - BytePos(1),
4230 hi: original_span.hi,
4231 ctxt: original_span.ctxt,
4233 err.span_help(span_semi, "consider removing this semicolon:");
4236 // Instantiates the given path, which must refer to an item with the given
4237 // number of type parameters and type.
4238 pub fn instantiate_value_path(&self,
4239 segments: &[hir::PathSegment],
4240 opt_self_ty: Option<Ty<'tcx>>,
4243 node_id: ast::NodeId)
4245 debug!("instantiate_value_path(path={:?}, def={:?}, node_id={})",
4250 // We need to extract the type parameters supplied by the user in
4251 // the path `path`. Due to the current setup, this is a bit of a
4252 // tricky-process; the problem is that resolve only tells us the
4253 // end-point of the path resolution, and not the intermediate steps.
4254 // Luckily, we can (at least for now) deduce the intermediate steps
4255 // just from the end-point.
4257 // There are basically four cases to consider:
4259 // 1. Reference to a constructor of enum variant or struct:
4261 // struct Foo<T>(...)
4262 // enum E<T> { Foo(...) }
4264 // In these cases, the parameters are declared in the type
4267 // 2. Reference to a fn item or a free constant:
4271 // In this case, the path will again always have the form
4272 // `a::b::foo::<T>` where only the final segment should have
4273 // type parameters. However, in this case, those parameters are
4274 // declared on a value, and hence are in the `FnSpace`.
4276 // 3. Reference to a method or an associated constant:
4278 // impl<A> SomeStruct<A> {
4282 // Here we can have a path like
4283 // `a::b::SomeStruct::<A>::foo::<B>`, in which case parameters
4284 // may appear in two places. The penultimate segment,
4285 // `SomeStruct::<A>`, contains parameters in TypeSpace, and the
4286 // final segment, `foo::<B>` contains parameters in fn space.
4288 // 4. Reference to a local variable
4290 // Local variables can't have any type parameters.
4292 // The first step then is to categorize the segments appropriately.
4294 assert!(!segments.is_empty());
4296 let mut ufcs_associated = None;
4297 let mut type_segment = None;
4298 let mut fn_segment = None;
4300 // Case 1. Reference to a struct/variant constructor.
4301 Def::StructCtor(def_id, ..) |
4302 Def::VariantCtor(def_id, ..) => {
4303 // Everything but the final segment should have no
4304 // parameters at all.
4305 let mut generics = self.tcx.generics_of(def_id);
4306 if let Some(def_id) = generics.parent {
4307 // Variant and struct constructors use the
4308 // generics of their parent type definition.
4309 generics = self.tcx.generics_of(def_id);
4311 type_segment = Some((segments.last().unwrap(), generics));
4314 // Case 2. Reference to a top-level value.
4316 Def::Const(def_id) |
4317 Def::Static(def_id, _) => {
4318 fn_segment = Some((segments.last().unwrap(),
4319 self.tcx.generics_of(def_id)));
4322 // Case 3. Reference to a method or associated const.
4323 Def::Method(def_id) |
4324 Def::AssociatedConst(def_id) => {
4325 let container = self.tcx.associated_item(def_id).container;
4327 ty::TraitContainer(trait_did) => {
4328 callee::check_legal_trait_for_method_call(self.tcx, span, trait_did)
4330 ty::ImplContainer(_) => {}
4333 let generics = self.tcx.generics_of(def_id);
4334 if segments.len() >= 2 {
4335 let parent_generics = self.tcx.generics_of(generics.parent.unwrap());
4336 type_segment = Some((&segments[segments.len() - 2], parent_generics));
4338 // `<T>::assoc` will end up here, and so can `T::assoc`.
4339 let self_ty = opt_self_ty.expect("UFCS sugared assoc missing Self");
4340 ufcs_associated = Some((container, self_ty));
4342 fn_segment = Some((segments.last().unwrap(), generics));
4345 // Case 4. Local variable, no generics.
4346 Def::Local(..) | Def::Upvar(..) => {}
4348 _ => bug!("unexpected definition: {:?}", def),
4351 debug!("type_segment={:?} fn_segment={:?}", type_segment, fn_segment);
4353 // Now that we have categorized what space the parameters for each
4354 // segment belong to, let's sort out the parameters that the user
4355 // provided (if any) into their appropriate spaces. We'll also report
4356 // errors if type parameters are provided in an inappropriate place.
4357 let poly_segments = type_segment.is_some() as usize +
4358 fn_segment.is_some() as usize;
4359 AstConv::prohibit_type_params(self, &segments[..segments.len() - poly_segments]);
4362 Def::Local(def_id) | Def::Upvar(def_id, ..) => {
4363 let nid = self.tcx.hir.as_local_node_id(def_id).unwrap();
4364 let ty = self.local_ty(span, nid);
4365 let ty = self.normalize_associated_types_in(span, &ty);
4366 self.write_ty(node_id, ty);
4372 // Now we have to compare the types that the user *actually*
4373 // provided against the types that were *expected*. If the user
4374 // did not provide any types, then we want to substitute inference
4375 // variables. If the user provided some types, we may still need
4376 // to add defaults. If the user provided *too many* types, that's
4378 self.check_path_parameter_count(span, &mut type_segment);
4379 self.check_path_parameter_count(span, &mut fn_segment);
4381 let (fn_start, has_self) = match (type_segment, fn_segment) {
4382 (_, Some((_, generics))) => {
4383 (generics.parent_count(), generics.has_self)
4385 (Some((_, generics)), None) => {
4386 (generics.own_count(), generics.has_self)
4388 (None, None) => (0, false)
4390 let substs = Substs::for_item(self.tcx, def.def_id(), |def, _| {
4391 let mut i = def.index as usize;
4393 let segment = if i < fn_start {
4394 i -= has_self as usize;
4400 let lifetimes = match segment.map(|(s, _)| &s.parameters) {
4401 Some(&hir::AngleBracketedParameters(ref data)) => &data.lifetimes[..],
4402 Some(&hir::ParenthesizedParameters(_)) => bug!(),
4406 if let Some(lifetime) = lifetimes.get(i) {
4407 AstConv::ast_region_to_region(self, lifetime, Some(def))
4409 self.re_infer(span, Some(def)).unwrap()
4412 let mut i = def.index as usize;
4414 let segment = if i < fn_start {
4415 // Handle Self first, so we can adjust the index to match the AST.
4416 if has_self && i == 0 {
4417 return opt_self_ty.unwrap_or_else(|| {
4418 self.type_var_for_def(span, def, substs)
4421 i -= has_self as usize;
4427 let (types, infer_types) = match segment.map(|(s, _)| &s.parameters) {
4428 Some(&hir::AngleBracketedParameters(ref data)) => {
4429 (&data.types[..], data.infer_types)
4431 Some(&hir::ParenthesizedParameters(_)) => bug!(),
4432 None => (&[][..], true)
4435 // Skip over the lifetimes in the same segment.
4436 if let Some((_, generics)) = segment {
4437 i -= generics.regions.len();
4440 if let Some(ast_ty) = types.get(i) {
4441 // A provided type parameter.
4443 } else if !infer_types && def.has_default {
4444 // No type parameter provided, but a default exists.
4445 let default = self.tcx.type_of(def.def_id);
4448 default.subst_spanned(self.tcx, substs, Some(span))
4451 // No type parameters were provided, we can infer all.
4452 // This can also be reached in some error cases:
4453 // We prefer to use inference variables instead of
4454 // TyError to let type inference recover somewhat.
4455 self.type_var_for_def(span, def, substs)
4459 // The things we are substituting into the type should not contain
4460 // escaping late-bound regions, and nor should the base type scheme.
4461 let ty = self.tcx.type_of(def.def_id());
4462 assert!(!substs.has_escaping_regions());
4463 assert!(!ty.has_escaping_regions());
4465 // Add all the obligations that are required, substituting and
4466 // normalized appropriately.
4467 let bounds = self.instantiate_bounds(span, def.def_id(), &substs);
4468 self.add_obligations_for_parameters(
4469 traits::ObligationCause::new(span, self.body_id, traits::ItemObligation(def.def_id())),
4472 // Substitute the values for the type parameters into the type of
4473 // the referenced item.
4474 let ty_substituted = self.instantiate_type_scheme(span, &substs, &ty);
4476 if let Some((ty::ImplContainer(impl_def_id), self_ty)) = ufcs_associated {
4477 // In the case of `Foo<T>::method` and `<Foo<T>>::method`, if `method`
4478 // is inherent, there is no `Self` parameter, instead, the impl needs
4479 // type parameters, which we can infer by unifying the provided `Self`
4480 // with the substituted impl type.
4481 let ty = self.tcx.type_of(impl_def_id);
4483 let impl_ty = self.instantiate_type_scheme(span, &substs, &ty);
4484 match self.at(&self.misc(span), self.param_env).sup(impl_ty, self_ty) {
4485 Ok(ok) => self.register_infer_ok_obligations(ok),
4488 "instantiate_value_path: (UFCS) {:?} was a subtype of {:?} but now is not?",
4495 debug!("instantiate_value_path: type of {:?} is {:?}",
4498 self.write_substs(node_id, substs);
4502 /// Report errors if the provided parameters are too few or too many.
4503 fn check_path_parameter_count(&self,
4505 segment: &mut Option<(&hir::PathSegment, &ty::Generics)>) {
4506 let (lifetimes, types, infer_types, bindings) = {
4507 match segment.map(|(s, _)| &s.parameters) {
4508 Some(&hir::AngleBracketedParameters(ref data)) => {
4509 (&data.lifetimes[..], &data.types[..], data.infer_types, &data.bindings[..])
4511 Some(&hir::ParenthesizedParameters(_)) => {
4512 AstConv::prohibit_parenthesized_params(self, &segment.as_ref().unwrap().0,
4514 (&[][..], &[][..], true, &[][..])
4516 None => (&[][..], &[][..], true, &[][..])
4520 let count_lifetime_params = |n| {
4521 format!("{} lifetime parameter{}", n, if n == 1 { "" } else { "s" })
4523 let count_type_params = |n| {
4524 format!("{} type parameter{}", n, if n == 1 { "" } else { "s" })
4527 // Check provided lifetime parameters.
4528 let lifetime_defs = segment.map_or(&[][..], |(_, generics)| &generics.regions);
4529 if lifetimes.len() > lifetime_defs.len() {
4530 let expected_text = count_lifetime_params(lifetime_defs.len());
4531 let actual_text = count_lifetime_params(lifetimes.len());
4532 struct_span_err!(self.tcx.sess, span, E0088,
4533 "too many lifetime parameters provided: \
4534 expected at most {}, found {}",
4535 expected_text, actual_text)
4536 .span_label(span, format!("expected {}", expected_text))
4538 } else if lifetimes.len() > 0 && lifetimes.len() < lifetime_defs.len() {
4539 let expected_text = count_lifetime_params(lifetime_defs.len());
4540 let actual_text = count_lifetime_params(lifetimes.len());
4541 struct_span_err!(self.tcx.sess, span, E0090,
4542 "too few lifetime parameters provided: \
4543 expected {}, found {}",
4544 expected_text, actual_text)
4545 .span_label(span, format!("expected {}", expected_text))
4549 // The case where there is not enough lifetime parameters is not checked,
4550 // because this is not possible - a function never takes lifetime parameters.
4551 // See discussion for Pull Request 36208.
4553 // Check provided type parameters.
4554 let type_defs = segment.map_or(&[][..], |(_, generics)| {
4555 if generics.parent.is_none() {
4556 &generics.types[generics.has_self as usize..]
4561 let required_len = type_defs.iter().take_while(|d| !d.has_default).count();
4562 if types.len() > type_defs.len() {
4563 let span = types[type_defs.len()].span;
4564 let expected_text = count_type_params(type_defs.len());
4565 let actual_text = count_type_params(types.len());
4566 struct_span_err!(self.tcx.sess, span, E0087,
4567 "too many type parameters provided: \
4568 expected at most {}, found {}",
4569 expected_text, actual_text)
4570 .span_label(span, format!("expected {}", expected_text))
4573 // To prevent derived errors to accumulate due to extra
4574 // type parameters, we force instantiate_value_path to
4575 // use inference variables instead of the provided types.
4577 } else if !infer_types && types.len() < required_len {
4578 let expected_text = count_type_params(required_len);
4579 let actual_text = count_type_params(types.len());
4580 struct_span_err!(self.tcx.sess, span, E0089,
4581 "too few type parameters provided: \
4582 expected {}, found {}",
4583 expected_text, actual_text)
4584 .span_label(span, format!("expected {}", expected_text))
4588 if !bindings.is_empty() {
4589 span_err!(self.tcx.sess, bindings[0].span, E0182,
4590 "unexpected binding of associated item in expression path \
4591 (only allowed in type paths)");
4595 fn structurally_resolve_type_or_else<F>(&self, sp: Span, ty: Ty<'tcx>, f: F)
4597 where F: Fn() -> Ty<'tcx>
4599 let mut ty = self.resolve_type_vars_with_obligations(ty);
4602 let alternative = f();
4605 if alternative.is_ty_var() || alternative.references_error() {
4606 if !self.is_tainted_by_errors() {
4607 self.type_error_message(sp, |_actual| {
4608 "the type of this value must be known in this context".to_string()
4611 self.demand_suptype(sp, self.tcx.types.err, ty);
4612 ty = self.tcx.types.err;
4614 self.demand_suptype(sp, alternative, ty);
4622 // Resolves `typ` by a single level if `typ` is a type variable. If no
4623 // resolution is possible, then an error is reported.
4624 pub fn structurally_resolved_type(&self, sp: Span, ty: Ty<'tcx>) -> Ty<'tcx> {
4625 self.structurally_resolve_type_or_else(sp, ty, || {
4630 fn with_breakable_ctxt<F: FnOnce() -> R, R>(&self, id: ast::NodeId,
4631 ctxt: BreakableCtxt<'gcx, 'tcx>, f: F)
4632 -> (BreakableCtxt<'gcx, 'tcx>, R) {
4635 let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
4636 index = enclosing_breakables.stack.len();
4637 enclosing_breakables.by_id.insert(id, index);
4638 enclosing_breakables.stack.push(ctxt);
4642 let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
4643 debug_assert!(enclosing_breakables.stack.len() == index + 1);
4644 enclosing_breakables.by_id.remove(&id).expect("missing breakable context");
4645 enclosing_breakables.stack.pop().expect("missing breakable context")
4651 pub fn check_bounds_are_used<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
4652 generics: &hir::Generics,
4654 debug!("check_bounds_are_used(n_tps={}, ty={:?})",
4655 generics.ty_params.len(), ty);
4657 // make a vector of booleans initially false, set to true when used
4658 if generics.ty_params.is_empty() { return; }
4659 let mut tps_used = vec![false; generics.ty_params.len()];
4661 for leaf_ty in ty.walk() {
4662 if let ty::TyParam(ParamTy {idx, ..}) = leaf_ty.sty {
4663 debug!("Found use of ty param num {}", idx);
4664 tps_used[idx as usize - generics.lifetimes.len()] = true;
4668 for (&used, param) in tps_used.iter().zip(&generics.ty_params) {
4670 struct_span_err!(tcx.sess, param.span, E0091,
4671 "type parameter `{}` is unused",
4673 .span_label(param.span, "unused type parameter")