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::TupleArgumentsFlag::*;
87 use fmt_macros::{Parser, Piece, Position};
88 use hir::def::{Def, CtorKind};
89 use hir::def_id::{CrateNum, DefId, LOCAL_CRATE};
90 use rustc_back::slice::ref_slice;
91 use rustc::infer::{self, InferCtxt, InferOk, RegionVariableOrigin};
92 use rustc::infer::type_variable::{TypeVariableOrigin};
93 use rustc::middle::region::CodeExtent;
94 use rustc::ty::subst::{Kind, Subst, Substs};
95 use rustc::traits::{self, FulfillmentContext, ObligationCause, ObligationCauseCode, Reveal};
96 use rustc::ty::{ParamTy, LvaluePreference, NoPreference, PreferMutLvalue};
97 use rustc::ty::{self, Ty, TyCtxt, Visibility};
98 use rustc::ty::{MethodCallee};
99 use rustc::ty::adjustment::{Adjust, Adjustment, AutoBorrow};
100 use rustc::ty::fold::{BottomUpFolder, TypeFoldable};
101 use rustc::ty::maps::Providers;
102 use rustc::ty::util::{Representability, IntTypeExt};
103 use errors::DiagnosticBuilder;
104 use require_c_abi_if_variadic;
105 use session::{Session, CompileResult};
108 use util::common::{ErrorReported, indenter};
109 use util::nodemap::{DefIdMap, FxHashMap, NodeMap};
111 use std::cell::{Cell, RefCell};
112 use std::collections::hash_map::Entry;
114 use std::mem::replace;
115 use std::ops::{self, Deref};
116 use syntax::abi::Abi;
118 use syntax::codemap::{self, original_sp, Spanned};
119 use syntax::feature_gate::{GateIssue, emit_feature_err};
121 use syntax::symbol::{Symbol, InternedString, keywords};
122 use syntax::util::lev_distance::find_best_match_for_name;
123 use syntax_pos::{self, BytePos, Span, DUMMY_SP};
125 use rustc::hir::intravisit::{self, Visitor, NestedVisitorMap};
126 use rustc::hir::itemlikevisit::ItemLikeVisitor;
127 use rustc::hir::{self, PatKind};
128 use rustc::middle::lang_items;
129 use rustc_back::slice;
130 use rustc::middle::const_val::eval_length;
131 use rustc_const_math::ConstInt;
150 /// closures defined within the function. For example:
153 /// bar(move|| { ... })
156 /// Here, the function `foo()` and the closure passed to
157 /// `bar()` will each have their own `FnCtxt`, but they will
158 /// share the inherited fields.
159 pub struct Inherited<'a, 'gcx: 'a+'tcx, 'tcx: 'a> {
160 infcx: InferCtxt<'a, 'gcx, 'tcx>,
162 locals: RefCell<NodeMap<Ty<'tcx>>>,
164 fulfillment_cx: RefCell<traits::FulfillmentContext<'tcx>>,
166 // When we process a call like `c()` where `c` is a closure type,
167 // we may not have decided yet whether `c` is a `Fn`, `FnMut`, or
168 // `FnOnce` closure. In that case, we defer full resolution of the
169 // call until upvar inference can kick in and make the
170 // decision. We keep these deferred resolutions grouped by the
171 // def-id of the closure, so that once we decide, we can easily go
172 // back and process them.
173 deferred_call_resolutions: RefCell<DefIdMap<Vec<DeferredCallResolution<'gcx, 'tcx>>>>,
175 deferred_cast_checks: RefCell<Vec<cast::CastCheck<'tcx>>>,
177 // Anonymized types found in explicit return types and their
178 // associated fresh inference variable. Writeback resolves these
179 // variables to get the concrete type, which can be used to
180 // deanonymize TyAnon, after typeck is done with all functions.
181 anon_types: RefCell<NodeMap<Ty<'tcx>>>,
183 /// Each type parameter has an implicit region bound that
184 /// indicates it must outlive at least the function body (the user
185 /// may specify stronger requirements). This field indicates the
186 /// region of the callee. If it is `None`, then the parameter
187 /// environment is for an item or something where the "callee" is
189 implicit_region_bound: Option<ty::Region<'tcx>>,
192 impl<'a, 'gcx, 'tcx> Deref for Inherited<'a, 'gcx, 'tcx> {
193 type Target = InferCtxt<'a, 'gcx, 'tcx>;
194 fn deref(&self) -> &Self::Target {
199 /// When type-checking an expression, we propagate downward
200 /// whatever type hint we are able in the form of an `Expectation`.
201 #[derive(Copy, Clone, Debug)]
202 pub enum Expectation<'tcx> {
203 /// We know nothing about what type this expression should have.
206 /// This expression should have the type given (or some subtype)
207 ExpectHasType(Ty<'tcx>),
209 /// This expression will be cast to the `Ty`
210 ExpectCastableToType(Ty<'tcx>),
212 /// This rvalue expression will be wrapped in `&` or `Box` and coerced
213 /// to `&Ty` or `Box<Ty>`, respectively. `Ty` is `[A]` or `Trait`.
214 ExpectRvalueLikeUnsized(Ty<'tcx>),
217 impl<'a, 'gcx, 'tcx> Expectation<'tcx> {
218 // Disregard "castable to" expectations because they
219 // can lead us astray. Consider for example `if cond
220 // {22} else {c} as u8` -- if we propagate the
221 // "castable to u8" constraint to 22, it will pick the
222 // type 22u8, which is overly constrained (c might not
223 // be a u8). In effect, the problem is that the
224 // "castable to" expectation is not the tightest thing
225 // we can say, so we want to drop it in this case.
226 // The tightest thing we can say is "must unify with
227 // else branch". Note that in the case of a "has type"
228 // constraint, this limitation does not hold.
230 // If the expected type is just a type variable, then don't use
231 // an expected type. Otherwise, we might write parts of the type
232 // when checking the 'then' block which are incompatible with the
234 fn adjust_for_branches(&self, fcx: &FnCtxt<'a, 'gcx, 'tcx>) -> Expectation<'tcx> {
236 ExpectHasType(ety) => {
237 let ety = fcx.shallow_resolve(ety);
238 if !ety.is_ty_var() {
244 ExpectRvalueLikeUnsized(ety) => {
245 ExpectRvalueLikeUnsized(ety)
251 /// Provide an expectation for an rvalue expression given an *optional*
252 /// hint, which is not required for type safety (the resulting type might
253 /// be checked higher up, as is the case with `&expr` and `box expr`), but
254 /// is useful in determining the concrete type.
256 /// The primary use case is where the expected type is a fat pointer,
257 /// like `&[isize]`. For example, consider the following statement:
259 /// let x: &[isize] = &[1, 2, 3];
261 /// In this case, the expected type for the `&[1, 2, 3]` expression is
262 /// `&[isize]`. If however we were to say that `[1, 2, 3]` has the
263 /// expectation `ExpectHasType([isize])`, that would be too strong --
264 /// `[1, 2, 3]` does not have the type `[isize]` but rather `[isize; 3]`.
265 /// It is only the `&[1, 2, 3]` expression as a whole that can be coerced
266 /// to the type `&[isize]`. Therefore, we propagate this more limited hint,
267 /// which still is useful, because it informs integer literals and the like.
268 /// See the test case `test/run-pass/coerce-expect-unsized.rs` and #20169
269 /// for examples of where this comes up,.
270 fn rvalue_hint(fcx: &FnCtxt<'a, 'gcx, 'tcx>, ty: Ty<'tcx>) -> Expectation<'tcx> {
271 match fcx.tcx.struct_tail(ty).sty {
272 ty::TySlice(_) | ty::TyStr | ty::TyDynamic(..) => {
273 ExpectRvalueLikeUnsized(ty)
275 _ => ExpectHasType(ty)
279 // Resolves `expected` by a single level if it is a variable. If
280 // there is no expected type or resolution is not possible (e.g.,
281 // no constraints yet present), just returns `None`.
282 fn resolve(self, fcx: &FnCtxt<'a, 'gcx, 'tcx>) -> Expectation<'tcx> {
287 ExpectCastableToType(t) => {
288 ExpectCastableToType(fcx.resolve_type_vars_if_possible(&t))
290 ExpectHasType(t) => {
291 ExpectHasType(fcx.resolve_type_vars_if_possible(&t))
293 ExpectRvalueLikeUnsized(t) => {
294 ExpectRvalueLikeUnsized(fcx.resolve_type_vars_if_possible(&t))
299 fn to_option(self, fcx: &FnCtxt<'a, 'gcx, 'tcx>) -> Option<Ty<'tcx>> {
300 match self.resolve(fcx) {
301 NoExpectation => None,
302 ExpectCastableToType(ty) |
304 ExpectRvalueLikeUnsized(ty) => Some(ty),
308 /// It sometimes happens that we want to turn an expectation into
309 /// a **hard constraint** (i.e., something that must be satisfied
310 /// for the program to type-check). `only_has_type` will return
311 /// such a constraint, if it exists.
312 fn only_has_type(self, fcx: &FnCtxt<'a, 'gcx, 'tcx>) -> Option<Ty<'tcx>> {
313 match self.resolve(fcx) {
314 ExpectHasType(ty) => Some(ty),
319 /// Like `only_has_type`, but instead of returning `None` if no
320 /// hard constraint exists, creates a fresh type variable.
321 fn coercion_target_type(self, fcx: &FnCtxt<'a, 'gcx, 'tcx>, span: Span) -> Ty<'tcx> {
322 self.only_has_type(fcx)
323 .unwrap_or_else(|| fcx.next_ty_var(TypeVariableOrigin::MiscVariable(span)))
327 #[derive(Copy, Clone)]
328 pub struct UnsafetyState {
329 pub def: ast::NodeId,
330 pub unsafety: hir::Unsafety,
331 pub unsafe_push_count: u32,
336 pub fn function(unsafety: hir::Unsafety, def: ast::NodeId) -> UnsafetyState {
337 UnsafetyState { def: def, unsafety: unsafety, unsafe_push_count: 0, from_fn: true }
340 pub fn recurse(&mut self, blk: &hir::Block) -> UnsafetyState {
341 match self.unsafety {
342 // If this unsafe, then if the outer function was already marked as
343 // unsafe we shouldn't attribute the unsafe'ness to the block. This
344 // way the block can be warned about instead of ignoring this
345 // extraneous block (functions are never warned about).
346 hir::Unsafety::Unsafe if self.from_fn => *self,
349 let (unsafety, def, count) = match blk.rules {
350 hir::PushUnsafeBlock(..) =>
351 (unsafety, blk.id, self.unsafe_push_count.checked_add(1).unwrap()),
352 hir::PopUnsafeBlock(..) =>
353 (unsafety, blk.id, self.unsafe_push_count.checked_sub(1).unwrap()),
354 hir::UnsafeBlock(..) =>
355 (hir::Unsafety::Unsafe, blk.id, self.unsafe_push_count),
357 (unsafety, self.def, self.unsafe_push_count),
359 UnsafetyState{ def: def,
361 unsafe_push_count: count,
368 #[derive(Debug, Copy, Clone)]
374 /// Tracks whether executing a node may exit normally (versus
375 /// return/break/panic, which "diverge", leaving dead code in their
376 /// wake). Tracked semi-automatically (through type variables marked
377 /// as diverging), with some manual adjustments for control-flow
378 /// primitives (approximating a CFG).
379 #[derive(Copy, Clone, Debug, PartialEq, Eq, PartialOrd, Ord)]
381 /// Potentially unknown, some cases converge,
382 /// others require a CFG to determine them.
385 /// Definitely known to diverge and therefore
386 /// not reach the next sibling or its parent.
389 /// Same as `Always` but with a reachability
390 /// warning already emitted
394 // Convenience impls for combinig `Diverges`.
396 impl ops::BitAnd for Diverges {
398 fn bitand(self, other: Self) -> Self {
399 cmp::min(self, other)
403 impl ops::BitOr for Diverges {
405 fn bitor(self, other: Self) -> Self {
406 cmp::max(self, other)
410 impl ops::BitAndAssign for Diverges {
411 fn bitand_assign(&mut self, other: Self) {
412 *self = *self & other;
416 impl ops::BitOrAssign for Diverges {
417 fn bitor_assign(&mut self, other: Self) {
418 *self = *self | other;
423 fn always(self) -> bool {
424 self >= Diverges::Always
428 pub struct BreakableCtxt<'gcx: 'tcx, 'tcx> {
431 // this is `null` for loops where break with a value is illegal,
432 // such as `while`, `for`, and `while let`
433 coerce: Option<DynamicCoerceMany<'gcx, 'tcx>>,
436 pub struct EnclosingBreakables<'gcx: 'tcx, 'tcx> {
437 stack: Vec<BreakableCtxt<'gcx, 'tcx>>,
438 by_id: NodeMap<usize>,
441 impl<'gcx, 'tcx> EnclosingBreakables<'gcx, 'tcx> {
442 fn find_breakable(&mut self, target_id: ast::NodeId) -> &mut BreakableCtxt<'gcx, 'tcx> {
443 let ix = *self.by_id.get(&target_id).unwrap_or_else(|| {
444 bug!("could not find enclosing breakable with id {}", target_id);
450 pub struct FnCtxt<'a, 'gcx: 'a+'tcx, 'tcx: 'a> {
451 body_id: ast::NodeId,
453 // Number of errors that had been reported when we started
454 // checking this function. On exit, if we find that *more* errors
455 // have been reported, we will skip regionck and other work that
456 // expects the types within the function to be consistent.
457 err_count_on_creation: usize,
459 ret_coercion: Option<RefCell<DynamicCoerceMany<'gcx, 'tcx>>>,
461 ps: RefCell<UnsafetyState>,
463 /// Whether the last checked node generates a divergence (e.g.,
464 /// `return` will set this to Always). In general, when entering
465 /// an expression or other node in the tree, the initial value
466 /// indicates whether prior parts of the containing expression may
467 /// have diverged. It is then typically set to `Maybe` (and the
468 /// old value remembered) for processing the subparts of the
469 /// current expression. As each subpart is processed, they may set
470 /// the flag to `Always` etc. Finally, at the end, we take the
471 /// result and "union" it with the original value, so that when we
472 /// return the flag indicates if any subpart of the the parent
473 /// expression (up to and including this part) has diverged. So,
474 /// if you read it after evaluating a subexpression `X`, the value
475 /// you get indicates whether any subexpression that was
476 /// evaluating up to and including `X` diverged.
478 /// We use this flag for two purposes:
480 /// - To warn about unreachable code: if, after processing a
481 /// sub-expression but before we have applied the effects of the
482 /// current node, we see that the flag is set to `Always`, we
483 /// can issue a warning. This corresponds to something like
484 /// `foo(return)`; we warn on the `foo()` expression. (We then
485 /// update the flag to `WarnedAlways` to suppress duplicate
486 /// reports.) Similarly, if we traverse to a fresh statement (or
487 /// tail expression) from a `Always` setting, we will isssue a
488 /// warning. This corresponds to something like `{return;
489 /// foo();}` or `{return; 22}`, where we would warn on the
492 /// - To permit assignment into a local variable or other lvalue
493 /// (including the "return slot") of type `!`. This is allowed
494 /// if **either** the type of value being assigned is `!`, which
495 /// means the current code is dead, **or** the expression's
496 /// divering flag is true, which means that a divering value was
497 /// wrapped (e.g., `let x: ! = foo(return)`).
499 /// To repeat the last point: an expression represents dead-code
500 /// if, after checking it, **either** its type is `!` OR the
501 /// diverges flag is set to something other than `Maybe`.
502 diverges: Cell<Diverges>,
504 /// Whether any child nodes have any type errors.
505 has_errors: Cell<bool>,
507 enclosing_breakables: RefCell<EnclosingBreakables<'gcx, 'tcx>>,
509 inh: &'a Inherited<'a, 'gcx, 'tcx>,
512 impl<'a, 'gcx, 'tcx> Deref for FnCtxt<'a, 'gcx, 'tcx> {
513 type Target = Inherited<'a, 'gcx, 'tcx>;
514 fn deref(&self) -> &Self::Target {
519 /// Helper type of a temporary returned by Inherited::build(...).
520 /// Necessary because we can't write the following bound:
521 /// F: for<'b, 'tcx> where 'gcx: 'tcx FnOnce(Inherited<'b, 'gcx, 'tcx>).
522 pub struct InheritedBuilder<'a, 'gcx: 'a+'tcx, 'tcx: 'a> {
523 infcx: infer::InferCtxtBuilder<'a, 'gcx, 'tcx>,
527 impl<'a, 'gcx, 'tcx> Inherited<'a, 'gcx, 'tcx> {
528 pub fn build(tcx: TyCtxt<'a, 'gcx, 'gcx>, def_id: DefId)
529 -> InheritedBuilder<'a, 'gcx, 'tcx> {
530 let tables = ty::TypeckTables::empty();
531 let param_env = tcx.param_env(def_id);
533 infcx: tcx.infer_ctxt((tables, param_env), Reveal::UserFacing),
539 impl<'a, 'gcx, 'tcx> InheritedBuilder<'a, 'gcx, 'tcx> {
540 fn enter<F, R>(&'tcx mut self, f: F) -> R
541 where F: for<'b> FnOnce(Inherited<'b, 'gcx, 'tcx>) -> R
543 let def_id = self.def_id;
544 self.infcx.enter(|infcx| f(Inherited::new(infcx, def_id)))
548 impl<'a, 'gcx, 'tcx> Inherited<'a, 'gcx, 'tcx> {
549 fn new(infcx: InferCtxt<'a, 'gcx, 'tcx>, def_id: DefId) -> Self {
551 let item_id = tcx.hir.as_local_node_id(def_id);
552 let body_id = item_id.and_then(|id| tcx.hir.maybe_body_owned_by(id));
553 let implicit_region_bound = body_id.map(|body| {
554 tcx.mk_region(ty::ReScope(CodeExtent::CallSiteScope(body)))
559 fulfillment_cx: RefCell::new(traits::FulfillmentContext::new()),
560 locals: RefCell::new(NodeMap()),
561 deferred_call_resolutions: RefCell::new(DefIdMap()),
562 deferred_cast_checks: RefCell::new(Vec::new()),
563 anon_types: RefCell::new(NodeMap()),
564 implicit_region_bound,
568 fn register_predicate(&self, obligation: traits::PredicateObligation<'tcx>) {
569 debug!("register_predicate({:?})", obligation);
570 if obligation.has_escaping_regions() {
571 span_bug!(obligation.cause.span, "escaping regions in predicate {:?}",
576 .register_predicate_obligation(self, obligation);
579 fn register_predicates(&self, obligations: Vec<traits::PredicateObligation<'tcx>>) {
580 for obligation in obligations {
581 self.register_predicate(obligation);
585 fn register_infer_ok_obligations<T>(&self, infer_ok: InferOk<'tcx, T>) -> T {
586 self.register_predicates(infer_ok.obligations);
590 fn normalize_associated_types_in<T>(&self,
592 body_id: ast::NodeId,
594 where T : TypeFoldable<'tcx>
596 let ok = self.normalize_associated_types_in_as_infer_ok(span, body_id, value);
597 self.register_infer_ok_obligations(ok)
600 fn normalize_associated_types_in_as_infer_ok<T>(&self,
602 body_id: ast::NodeId,
605 where T : TypeFoldable<'tcx>
607 debug!("normalize_associated_types_in(value={:?})", value);
608 let mut selcx = traits::SelectionContext::new(self);
609 let cause = ObligationCause::misc(span, body_id);
610 let traits::Normalized { value, obligations } =
611 traits::normalize(&mut selcx, cause, value);
612 debug!("normalize_associated_types_in: result={:?} predicates={:?}",
615 InferOk { value, obligations }
618 /// Replace any late-bound regions bound in `value` with
619 /// free variants attached to `all_outlive_scope`.
620 fn liberate_late_bound_regions<T>(&self,
621 all_outlive_scope: DefId,
622 value: &ty::Binder<T>)
624 where T: TypeFoldable<'tcx>
626 self.tcx.replace_late_bound_regions(value, |br| {
627 self.tcx.mk_region(ty::ReFree(ty::FreeRegion {
628 scope: all_outlive_scope,
635 struct CheckItemTypesVisitor<'a, 'tcx: 'a> { tcx: TyCtxt<'a, 'tcx, 'tcx> }
637 impl<'a, 'tcx> ItemLikeVisitor<'tcx> for CheckItemTypesVisitor<'a, 'tcx> {
638 fn visit_item(&mut self, i: &'tcx hir::Item) {
639 check_item_type(self.tcx, i);
641 fn visit_trait_item(&mut self, _: &'tcx hir::TraitItem) { }
642 fn visit_impl_item(&mut self, _: &'tcx hir::ImplItem) { }
645 pub fn check_wf_new<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>) -> CompileResult {
646 tcx.sess.track_errors(|| {
647 let mut visit = wfcheck::CheckTypeWellFormedVisitor::new(tcx);
648 tcx.hir.krate().visit_all_item_likes(&mut visit.as_deep_visitor());
652 pub fn check_item_types<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>) -> CompileResult {
653 tcx.sess.track_errors(|| {
654 tcx.hir.krate().visit_all_item_likes(&mut CheckItemTypesVisitor { tcx });
658 pub fn check_item_bodies<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>) -> CompileResult {
659 tcx.typeck_item_bodies(LOCAL_CRATE)
662 fn typeck_item_bodies<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, crate_num: CrateNum) -> CompileResult {
663 debug_assert!(crate_num == LOCAL_CRATE);
664 tcx.sess.track_errors(|| {
665 for body_owner_def_id in tcx.body_owners() {
666 tcx.typeck_tables_of(body_owner_def_id);
671 pub fn provide(providers: &mut Providers) {
672 *providers = Providers {
683 fn closure_type<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
685 -> ty::PolyFnSig<'tcx> {
686 let node_id = tcx.hir.as_local_node_id(def_id).unwrap();
687 tcx.typeck_tables_of(def_id).closure_tys[&node_id]
690 fn closure_kind<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
693 let node_id = tcx.hir.as_local_node_id(def_id).unwrap();
694 tcx.typeck_tables_of(def_id).closure_kinds[&node_id].0
697 fn adt_destructor<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
699 -> Option<ty::Destructor> {
700 tcx.calculate_dtor(def_id, &mut dropck::check_drop_impl)
703 /// If this def-id is a "primary tables entry", returns `Some((body_id, decl))`
704 /// with information about it's body-id and fn-decl (if any). Otherwise,
707 /// If this function returns "some", then `typeck_tables(def_id)` will
708 /// succeed; if it returns `None`, then `typeck_tables(def_id)` may or
709 /// may not succeed. In some cases where this function returns `None`
710 /// (notably closures), `typeck_tables(def_id)` would wind up
711 /// redirecting to the owning function.
712 fn primary_body_of<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
714 -> Option<(hir::BodyId, Option<&'tcx hir::FnDecl>)>
716 match tcx.hir.get(id) {
717 hir::map::NodeItem(item) => {
719 hir::ItemConst(_, body) |
720 hir::ItemStatic(_, _, body) =>
722 hir::ItemFn(ref decl, .., body) =>
723 Some((body, Some(decl))),
728 hir::map::NodeTraitItem(item) => {
730 hir::TraitItemKind::Const(_, Some(body)) =>
732 hir::TraitItemKind::Method(ref sig, hir::TraitMethod::Provided(body)) =>
733 Some((body, Some(&sig.decl))),
738 hir::map::NodeImplItem(item) => {
740 hir::ImplItemKind::Const(_, body) =>
742 hir::ImplItemKind::Method(ref sig, body) =>
743 Some((body, Some(&sig.decl))),
748 hir::map::NodeExpr(expr) => {
749 // FIXME(eddyb) Closures should have separate
750 // function definition IDs and expression IDs.
751 // Type-checking should not let closures get
752 // this far in a constant position.
753 // Assume that everything other than closures
754 // is a constant "initializer" expression.
756 hir::ExprClosure(..) =>
759 Some((hir::BodyId { node_id: expr.id }, None)),
766 fn has_typeck_tables<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
769 // Closures' tables come from their outermost function,
770 // as they are part of the same "inference environment".
771 let outer_def_id = tcx.closure_base_def_id(def_id);
772 if outer_def_id != def_id {
773 return tcx.has_typeck_tables(outer_def_id);
776 let id = tcx.hir.as_local_node_id(def_id).unwrap();
777 primary_body_of(tcx, id).is_some()
780 fn typeck_tables_of<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
782 -> &'tcx ty::TypeckTables<'tcx> {
783 // Closures' tables come from their outermost function,
784 // as they are part of the same "inference environment".
785 let outer_def_id = tcx.closure_base_def_id(def_id);
786 if outer_def_id != def_id {
787 return tcx.typeck_tables_of(outer_def_id);
790 let id = tcx.hir.as_local_node_id(def_id).unwrap();
791 let span = tcx.hir.span(id);
793 // Figure out what primary body this item has.
794 let (body_id, fn_decl) = primary_body_of(tcx, id).unwrap_or_else(|| {
795 span_bug!(span, "can't type-check body of {:?}", def_id);
797 let body = tcx.hir.body(body_id);
799 Inherited::build(tcx, def_id).enter(|inh| {
800 let fcx = if let Some(decl) = fn_decl {
801 let fn_sig = tcx.type_of(def_id).fn_sig();
803 check_abi(tcx, span, fn_sig.abi());
805 // Compute the fty from point of view of inside fn.
807 inh.liberate_late_bound_regions(def_id, &fn_sig);
809 inh.normalize_associated_types_in(body.value.span, body_id.node_id, &fn_sig);
811 check_fn(&inh, fn_sig, decl, id, body)
813 let fcx = FnCtxt::new(&inh, body.value.id);
814 let expected_type = tcx.type_of(def_id);
815 let expected_type = fcx.normalize_associated_types_in(body.value.span, &expected_type);
816 fcx.require_type_is_sized(expected_type, body.value.span, traits::ConstSized);
818 // Gather locals in statics (because of block expressions).
819 // This is technically unnecessary because locals in static items are forbidden,
820 // but prevents type checking from blowing up before const checking can properly
822 GatherLocalsVisitor { fcx: &fcx }.visit_body(body);
824 fcx.check_expr_coercable_to_type(&body.value, expected_type);
829 fcx.select_all_obligations_and_apply_defaults();
830 fcx.closure_analyze(body);
831 fcx.select_obligations_where_possible();
833 fcx.select_all_obligations_or_error();
835 if fn_decl.is_some() {
836 fcx.regionck_fn(id, body);
838 fcx.regionck_expr(body);
841 fcx.resolve_type_vars_in_body(body)
845 fn check_abi<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, span: Span, abi: Abi) {
846 if !tcx.sess.target.target.is_abi_supported(abi) {
847 struct_span_err!(tcx.sess, span, E0570,
848 "The ABI `{}` is not supported for the current target", abi).emit()
852 struct GatherLocalsVisitor<'a, 'gcx: 'a+'tcx, 'tcx: 'a> {
853 fcx: &'a FnCtxt<'a, 'gcx, 'tcx>
856 impl<'a, 'gcx, 'tcx> GatherLocalsVisitor<'a, 'gcx, 'tcx> {
857 fn assign(&mut self, span: Span, nid: ast::NodeId, ty_opt: Option<Ty<'tcx>>) -> Ty<'tcx> {
860 // infer the variable's type
861 let var_ty = self.fcx.next_ty_var(TypeVariableOrigin::TypeInference(span));
862 self.fcx.locals.borrow_mut().insert(nid, var_ty);
866 // take type that the user specified
867 self.fcx.locals.borrow_mut().insert(nid, typ);
874 impl<'a, 'gcx, 'tcx> Visitor<'gcx> for GatherLocalsVisitor<'a, 'gcx, 'tcx> {
875 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'gcx> {
876 NestedVisitorMap::None
879 // Add explicitly-declared locals.
880 fn visit_local(&mut self, local: &'gcx hir::Local) {
881 let o_ty = match local.ty {
882 Some(ref ty) => Some(self.fcx.to_ty(&ty)),
885 self.assign(local.span, local.id, o_ty);
886 debug!("Local variable {:?} is assigned type {}",
888 self.fcx.ty_to_string(
889 self.fcx.locals.borrow().get(&local.id).unwrap().clone()));
890 intravisit::walk_local(self, local);
893 // Add pattern bindings.
894 fn visit_pat(&mut self, p: &'gcx hir::Pat) {
895 if let PatKind::Binding(_, _, ref path1, _) = p.node {
896 let var_ty = self.assign(p.span, p.id, None);
898 self.fcx.require_type_is_sized(var_ty, p.span,
899 traits::VariableType(p.id));
901 debug!("Pattern binding {} is assigned to {} with type {:?}",
903 self.fcx.ty_to_string(
904 self.fcx.locals.borrow().get(&p.id).unwrap().clone()),
907 intravisit::walk_pat(self, p);
910 // Don't descend into the bodies of nested closures
911 fn visit_fn(&mut self, _: intravisit::FnKind<'gcx>, _: &'gcx hir::FnDecl,
912 _: hir::BodyId, _: Span, _: ast::NodeId) { }
915 /// Helper used for fns and closures. Does the grungy work of checking a function
916 /// body and returns the function context used for that purpose, since in the case of a fn item
917 /// there is still a bit more to do.
920 /// * inherited: other fields inherited from the enclosing fn (if any)
921 fn check_fn<'a, 'gcx, 'tcx>(inherited: &'a Inherited<'a, 'gcx, 'tcx>,
922 fn_sig: ty::FnSig<'tcx>,
923 decl: &'gcx hir::FnDecl,
925 body: &'gcx hir::Body)
926 -> FnCtxt<'a, 'gcx, 'tcx>
928 let mut fn_sig = fn_sig.clone();
930 debug!("check_fn(sig={:?}, fn_id={})", fn_sig, fn_id);
932 // Create the function context. This is either derived from scratch or,
933 // in the case of function expressions, based on the outer context.
934 let mut fcx = FnCtxt::new(inherited, body.value.id);
935 *fcx.ps.borrow_mut() = UnsafetyState::function(fn_sig.unsafety, fn_id);
937 let ret_ty = fn_sig.output();
938 fcx.require_type_is_sized(ret_ty, decl.output.span(), traits::ReturnType);
939 let ret_ty = fcx.instantiate_anon_types(&ret_ty);
940 fcx.ret_coercion = Some(RefCell::new(CoerceMany::new(ret_ty)));
941 fn_sig = fcx.tcx.mk_fn_sig(
942 fn_sig.inputs().iter().cloned(),
949 GatherLocalsVisitor { fcx: &fcx, }.visit_body(body);
951 // Add formal parameters.
952 for (arg_ty, arg) in fn_sig.inputs().iter().zip(&body.arguments) {
953 // The type of the argument must be well-formed.
955 // NB -- this is now checked in wfcheck, but that
956 // currently only results in warnings, so we issue an
957 // old-style WF obligation here so that we still get the
958 // errors that we used to get.
959 fcx.register_old_wf_obligation(arg_ty, arg.pat.span, traits::MiscObligation);
961 // Check the pattern.
962 fcx.check_pat_arg(&arg.pat, arg_ty, true);
963 fcx.write_ty(arg.id, arg_ty);
966 inherited.tables.borrow_mut().liberated_fn_sigs.insert(fn_id, fn_sig);
968 fcx.check_return_expr(&body.value);
970 // Finalize the return check by taking the LUB of the return types
971 // we saw and assigning it to the expected return type. This isn't
972 // really expected to fail, since the coercions would have failed
973 // earlier when trying to find a LUB.
975 // However, the behavior around `!` is sort of complex. In the
976 // event that the `actual_return_ty` comes back as `!`, that
977 // indicates that the fn either does not return or "returns" only
978 // values of type `!`. In this case, if there is an expected
979 // return type that is *not* `!`, that should be ok. But if the
980 // return type is being inferred, we want to "fallback" to `!`:
982 // let x = move || panic!();
984 // To allow for that, I am creating a type variable with diverging
985 // fallback. This was deemed ever so slightly better than unifying
986 // the return value with `!` because it allows for the caller to
987 // make more assumptions about the return type (e.g., they could do
989 // let y: Option<u32> = Some(x());
991 // which would then cause this return type to become `u32`, not
993 let coercion = fcx.ret_coercion.take().unwrap().into_inner();
994 let mut actual_return_ty = coercion.complete(&fcx);
995 if actual_return_ty.is_never() {
996 actual_return_ty = fcx.next_diverging_ty_var(
997 TypeVariableOrigin::DivergingFn(body.value.span));
999 fcx.demand_suptype(body.value.span, ret_ty, actual_return_ty);
1004 fn check_struct<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
1007 let def_id = tcx.hir.local_def_id(id);
1008 let def = tcx.adt_def(def_id);
1009 def.destructor(tcx); // force the destructor to be evaluated
1010 check_representable(tcx, span, def_id);
1012 if def.repr.simd() {
1013 check_simd(tcx, span, def_id);
1016 // if struct is packed and not aligned, check fields for alignment.
1017 // Checks for combining packed and align attrs on single struct are done elsewhere.
1018 if tcx.adt_def(def_id).repr.packed() && tcx.adt_def(def_id).repr.align == 0 {
1019 check_packed(tcx, span, def_id);
1023 fn check_union<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
1026 let def_id = tcx.hir.local_def_id(id);
1027 let def = tcx.adt_def(def_id);
1028 def.destructor(tcx); // force the destructor to be evaluated
1029 check_representable(tcx, span, def_id);
1032 pub fn check_item_type<'a,'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, it: &'tcx hir::Item) {
1033 debug!("check_item_type(it.id={}, it.name={})",
1035 tcx.item_path_str(tcx.hir.local_def_id(it.id)));
1036 let _indenter = indenter();
1038 // Consts can play a role in type-checking, so they are included here.
1039 hir::ItemStatic(..) |
1040 hir::ItemConst(..) => {
1041 tcx.typeck_tables_of(tcx.hir.local_def_id(it.id));
1043 hir::ItemEnum(ref enum_definition, _) => {
1046 &enum_definition.variants,
1049 hir::ItemFn(..) => {} // entirely within check_item_body
1050 hir::ItemImpl(.., ref impl_item_refs) => {
1051 debug!("ItemImpl {} with id {}", it.name, it.id);
1052 let impl_def_id = tcx.hir.local_def_id(it.id);
1053 if let Some(impl_trait_ref) = tcx.impl_trait_ref(impl_def_id) {
1054 check_impl_items_against_trait(tcx,
1059 let trait_def_id = impl_trait_ref.def_id;
1060 check_on_unimplemented(tcx, trait_def_id, it);
1063 hir::ItemTrait(..) => {
1064 let def_id = tcx.hir.local_def_id(it.id);
1065 check_on_unimplemented(tcx, def_id, it);
1067 hir::ItemStruct(..) => {
1068 check_struct(tcx, it.id, it.span);
1070 hir::ItemUnion(..) => {
1071 check_union(tcx, it.id, it.span);
1073 hir::ItemTy(_, ref generics) => {
1074 let def_id = tcx.hir.local_def_id(it.id);
1075 let pty_ty = tcx.type_of(def_id);
1076 check_bounds_are_used(tcx, generics, pty_ty);
1078 hir::ItemForeignMod(ref m) => {
1079 check_abi(tcx, it.span, m.abi);
1081 if m.abi == Abi::RustIntrinsic {
1082 for item in &m.items {
1083 intrinsic::check_intrinsic_type(tcx, item);
1085 } else if m.abi == Abi::PlatformIntrinsic {
1086 for item in &m.items {
1087 intrinsic::check_platform_intrinsic_type(tcx, item);
1090 for item in &m.items {
1091 let generics = tcx.generics_of(tcx.hir.local_def_id(item.id));
1092 if !generics.types.is_empty() {
1093 let mut err = struct_span_err!(tcx.sess, item.span, E0044,
1094 "foreign items may not have type parameters");
1095 span_help!(&mut err, item.span,
1096 "consider using specialization instead of \
1101 if let hir::ForeignItemFn(ref fn_decl, _, _) = item.node {
1102 require_c_abi_if_variadic(tcx, fn_decl, m.abi, item.span);
1107 _ => {/* nothing to do */ }
1111 fn check_on_unimplemented<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
1114 let generics = tcx.generics_of(def_id);
1115 if let Some(ref attr) = item.attrs.iter().find(|a| {
1116 a.check_name("rustc_on_unimplemented")
1118 if let Some(istring) = attr.value_str() {
1119 let istring = istring.as_str();
1120 let parser = Parser::new(&istring);
1121 let types = &generics.types;
1122 for token in parser {
1124 Piece::String(_) => (), // Normal string, no need to check it
1125 Piece::NextArgument(a) => match a.position {
1126 // `{Self}` is allowed
1127 Position::ArgumentNamed(s) if s == "Self" => (),
1128 // So is `{A}` if A is a type parameter
1129 Position::ArgumentNamed(s) => match types.iter().find(|t| {
1134 let name = tcx.item_name(def_id);
1135 span_err!(tcx.sess, attr.span, E0230,
1136 "there is no type parameter \
1141 // `{:1}` and `{}` are not to be used
1142 Position::ArgumentIs(_) => {
1143 span_err!(tcx.sess, attr.span, E0231,
1144 "only named substitution \
1145 parameters are allowed");
1152 tcx.sess, attr.span, E0232,
1153 "this attribute must have a value")
1154 .span_label(attr.span, "attribute requires a value")
1155 .note(&format!("eg `#[rustc_on_unimplemented = \"foo\"]`"))
1161 fn report_forbidden_specialization<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
1162 impl_item: &hir::ImplItem,
1165 let mut err = struct_span_err!(
1166 tcx.sess, impl_item.span, E0520,
1167 "`{}` specializes an item from a parent `impl`, but \
1168 that item is not marked `default`",
1170 err.span_label(impl_item.span, format!("cannot specialize default item `{}`",
1173 match tcx.span_of_impl(parent_impl) {
1175 err.span_label(span, "parent `impl` is here");
1176 err.note(&format!("to specialize, `{}` in the parent `impl` must be marked `default`",
1180 err.note(&format!("parent implementation is in crate `{}`", cname));
1187 fn check_specialization_validity<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
1188 trait_def: &ty::TraitDef,
1190 impl_item: &hir::ImplItem)
1192 let ancestors = trait_def.ancestors(tcx, impl_id);
1194 let kind = match impl_item.node {
1195 hir::ImplItemKind::Const(..) => ty::AssociatedKind::Const,
1196 hir::ImplItemKind::Method(..) => ty::AssociatedKind::Method,
1197 hir::ImplItemKind::Type(_) => ty::AssociatedKind::Type
1199 let parent = ancestors.defs(tcx, impl_item.name, kind).skip(1).next()
1200 .map(|node_item| node_item.map(|parent| parent.defaultness));
1202 if let Some(parent) = parent {
1203 if tcx.impl_item_is_final(&parent) {
1204 report_forbidden_specialization(tcx, impl_item, parent.node.def_id());
1210 fn check_impl_items_against_trait<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
1213 impl_trait_ref: ty::TraitRef<'tcx>,
1214 impl_item_refs: &[hir::ImplItemRef]) {
1215 // If the trait reference itself is erroneous (so the compilation is going
1216 // to fail), skip checking the items here -- the `impl_item` table in `tcx`
1217 // isn't populated for such impls.
1218 if impl_trait_ref.references_error() { return; }
1220 // Locate trait definition and items
1221 let trait_def = tcx.trait_def(impl_trait_ref.def_id);
1222 let mut overridden_associated_type = None;
1224 let impl_items = || impl_item_refs.iter().map(|iiref| tcx.hir.impl_item(iiref.id));
1226 // Check existing impl methods to see if they are both present in trait
1227 // and compatible with trait signature
1228 for impl_item in impl_items() {
1229 let ty_impl_item = tcx.associated_item(tcx.hir.local_def_id(impl_item.id));
1230 let ty_trait_item = tcx.associated_items(impl_trait_ref.def_id)
1231 .find(|ac| ac.name == ty_impl_item.name);
1233 // Check that impl definition matches trait definition
1234 if let Some(ty_trait_item) = ty_trait_item {
1235 match impl_item.node {
1236 hir::ImplItemKind::Const(..) => {
1237 // Find associated const definition.
1238 if ty_trait_item.kind == ty::AssociatedKind::Const {
1239 compare_const_impl(tcx,
1245 let mut err = struct_span_err!(tcx.sess, impl_item.span, E0323,
1246 "item `{}` is an associated const, \
1247 which doesn't match its trait `{}`",
1250 err.span_label(impl_item.span, "does not match trait");
1251 // We can only get the spans from local trait definition
1252 // Same for E0324 and E0325
1253 if let Some(trait_span) = tcx.hir.span_if_local(ty_trait_item.def_id) {
1254 err.span_label(trait_span, "item in trait");
1259 hir::ImplItemKind::Method(..) => {
1260 let trait_span = tcx.hir.span_if_local(ty_trait_item.def_id);
1261 if ty_trait_item.kind == ty::AssociatedKind::Method {
1262 let err_count = tcx.sess.err_count();
1263 compare_impl_method(tcx,
1269 true); // start with old-broken-mode
1270 if err_count == tcx.sess.err_count() {
1271 // old broken mode did not report an error. Try with the new mode.
1272 compare_impl_method(tcx,
1278 false); // use the new mode
1281 let mut err = struct_span_err!(tcx.sess, impl_item.span, E0324,
1282 "item `{}` is an associated method, \
1283 which doesn't match its trait `{}`",
1286 err.span_label(impl_item.span, "does not match trait");
1287 if let Some(trait_span) = tcx.hir.span_if_local(ty_trait_item.def_id) {
1288 err.span_label(trait_span, "item in trait");
1293 hir::ImplItemKind::Type(_) => {
1294 if ty_trait_item.kind == ty::AssociatedKind::Type {
1295 if ty_trait_item.defaultness.has_value() {
1296 overridden_associated_type = Some(impl_item);
1299 let mut err = struct_span_err!(tcx.sess, impl_item.span, E0325,
1300 "item `{}` is an associated type, \
1301 which doesn't match its trait `{}`",
1304 err.span_label(impl_item.span, "does not match trait");
1305 if let Some(trait_span) = tcx.hir.span_if_local(ty_trait_item.def_id) {
1306 err.span_label(trait_span, "item in trait");
1314 check_specialization_validity(tcx, trait_def, impl_id, impl_item);
1317 // Check for missing items from trait
1318 let mut missing_items = Vec::new();
1319 let mut invalidated_items = Vec::new();
1320 let associated_type_overridden = overridden_associated_type.is_some();
1321 for trait_item in tcx.associated_items(impl_trait_ref.def_id) {
1322 let is_implemented = trait_def.ancestors(tcx, impl_id)
1323 .defs(tcx, trait_item.name, trait_item.kind)
1325 .map(|node_item| !node_item.node.is_from_trait())
1328 if !is_implemented {
1329 if !trait_item.defaultness.has_value() {
1330 missing_items.push(trait_item);
1331 } else if associated_type_overridden {
1332 invalidated_items.push(trait_item.name);
1337 let signature = |item: &ty::AssociatedItem| {
1339 ty::AssociatedKind::Method => {
1340 format!("{}", tcx.type_of(item.def_id).fn_sig().0)
1342 ty::AssociatedKind::Type => format!("type {};", item.name.to_string()),
1343 ty::AssociatedKind::Const => {
1344 format!("const {}: {:?};", item.name.to_string(), tcx.type_of(item.def_id))
1349 if !missing_items.is_empty() {
1350 let mut err = struct_span_err!(tcx.sess, impl_span, E0046,
1351 "not all trait items implemented, missing: `{}`",
1352 missing_items.iter()
1353 .map(|trait_item| trait_item.name.to_string())
1354 .collect::<Vec<_>>().join("`, `"));
1355 err.span_label(impl_span, format!("missing `{}` in implementation",
1356 missing_items.iter()
1357 .map(|trait_item| trait_item.name.to_string())
1358 .collect::<Vec<_>>().join("`, `")));
1359 for trait_item in missing_items {
1360 if let Some(span) = tcx.hir.span_if_local(trait_item.def_id) {
1361 err.span_label(span, format!("`{}` from trait", trait_item.name));
1363 err.note(&format!("`{}` from trait: `{}`",
1365 signature(&trait_item)));
1371 if !invalidated_items.is_empty() {
1372 let invalidator = overridden_associated_type.unwrap();
1373 span_err!(tcx.sess, invalidator.span, E0399,
1374 "the following trait items need to be reimplemented \
1375 as `{}` was overridden: `{}`",
1377 invalidated_items.iter()
1378 .map(|name| name.to_string())
1379 .collect::<Vec<_>>().join("`, `"))
1383 /// Checks whether a type can be represented in memory. In particular, it
1384 /// identifies types that contain themselves without indirection through a
1385 /// pointer, which would mean their size is unbounded.
1386 fn check_representable<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
1390 let rty = tcx.type_of(item_def_id);
1392 // Check that it is possible to represent this type. This call identifies
1393 // (1) types that contain themselves and (2) types that contain a different
1394 // recursive type. It is only necessary to throw an error on those that
1395 // contain themselves. For case 2, there must be an inner type that will be
1396 // caught by case 1.
1397 match rty.is_representable(tcx, sp) {
1398 Representability::SelfRecursive(spans) => {
1399 let mut err = tcx.recursive_type_with_infinite_size_error(item_def_id);
1401 err.span_label(span, "recursive without indirection");
1406 Representability::Representable | Representability::ContainsRecursive => (),
1411 pub fn check_simd<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, sp: Span, def_id: DefId) {
1412 let t = tcx.type_of(def_id);
1414 ty::TyAdt(def, substs) if def.is_struct() => {
1415 let fields = &def.struct_variant().fields;
1416 if fields.is_empty() {
1417 span_err!(tcx.sess, sp, E0075, "SIMD vector cannot be empty");
1420 let e = fields[0].ty(tcx, substs);
1421 if !fields.iter().all(|f| f.ty(tcx, substs) == e) {
1422 struct_span_err!(tcx.sess, sp, E0076, "SIMD vector should be homogeneous")
1423 .span_label(sp, "SIMD elements must have the same type")
1428 ty::TyParam(_) => { /* struct<T>(T, T, T, T) is ok */ }
1429 _ if e.is_machine() => { /* struct(u8, u8, u8, u8) is ok */ }
1431 span_err!(tcx.sess, sp, E0077,
1432 "SIMD vector element type should be machine type");
1441 fn check_packed<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, sp: Span, def_id: DefId) {
1442 if check_packed_inner(tcx, def_id, &mut Vec::new()) {
1443 struct_span_err!(tcx.sess, sp, E0588,
1444 "packed struct cannot transitively contain a `[repr(align)]` struct").emit();
1448 fn check_packed_inner<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
1450 stack: &mut Vec<DefId>) -> bool {
1451 let t = tcx.type_of(def_id);
1452 if stack.contains(&def_id) {
1453 debug!("check_packed_inner: {:?} is recursive", t);
1457 ty::TyAdt(def, substs) if def.is_struct() => {
1458 if tcx.adt_def(def.did).repr.align > 0 {
1461 // push struct def_id before checking fields
1463 for field in &def.struct_variant().fields {
1464 let f = field.ty(tcx, substs);
1466 ty::TyAdt(def, _) => {
1467 if check_packed_inner(tcx, def.did, stack) {
1474 // only need to pop if not early out
1482 #[allow(trivial_numeric_casts)]
1483 pub fn check_enum<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
1485 vs: &'tcx [hir::Variant],
1487 let def_id = tcx.hir.local_def_id(id);
1488 let def = tcx.adt_def(def_id);
1489 def.destructor(tcx); // force the destructor to be evaluated
1491 if vs.is_empty() && tcx.has_attr(def_id, "repr") {
1493 tcx.sess, sp, E0084,
1494 "unsupported representation for zero-variant enum")
1495 .span_label(sp, "unsupported enum representation")
1499 let repr_type_ty = def.repr.discr_type().to_ty(tcx);
1500 if repr_type_ty == tcx.types.i128 || repr_type_ty == tcx.types.u128 {
1501 if !tcx.sess.features.borrow().i128_type {
1502 emit_feature_err(&tcx.sess.parse_sess,
1503 "i128_type", sp, GateIssue::Language, "128-bit type is unstable");
1508 if let Some(e) = v.node.disr_expr {
1509 tcx.typeck_tables_of(tcx.hir.local_def_id(e.node_id));
1513 let mut disr_vals: Vec<ConstInt> = Vec::new();
1514 for (discr, v) in def.discriminants(tcx).zip(vs) {
1515 // Check for duplicate discriminant values
1516 if let Some(i) = disr_vals.iter().position(|&x| x == discr) {
1517 let variant_i_node_id = tcx.hir.as_local_node_id(def.variants[i].did).unwrap();
1518 let variant_i = tcx.hir.expect_variant(variant_i_node_id);
1519 let i_span = match variant_i.node.disr_expr {
1520 Some(expr) => tcx.hir.span(expr.node_id),
1521 None => tcx.hir.span(variant_i_node_id)
1523 let span = match v.node.disr_expr {
1524 Some(expr) => tcx.hir.span(expr.node_id),
1527 struct_span_err!(tcx.sess, span, E0081,
1528 "discriminant value `{}` already exists", disr_vals[i])
1529 .span_label(i_span, format!("first use of `{}`", disr_vals[i]))
1530 .span_label(span , format!("enum already has `{}`", disr_vals[i]))
1533 disr_vals.push(discr);
1536 check_representable(tcx, sp, def_id);
1539 impl<'a, 'gcx, 'tcx> AstConv<'gcx, 'tcx> for FnCtxt<'a, 'gcx, 'tcx> {
1540 fn tcx<'b>(&'b self) -> TyCtxt<'b, 'gcx, 'tcx> { self.tcx }
1542 fn get_type_parameter_bounds(&self, _: Span, def_id: DefId)
1543 -> ty::GenericPredicates<'tcx>
1546 let node_id = tcx.hir.as_local_node_id(def_id).unwrap();
1547 let item_id = tcx.hir.ty_param_owner(node_id);
1548 let item_def_id = tcx.hir.local_def_id(item_id);
1549 let generics = tcx.generics_of(item_def_id);
1550 let index = generics.type_param_to_index[&def_id.index];
1551 ty::GenericPredicates {
1553 predicates: self.param_env.caller_bounds.iter().filter(|predicate| {
1555 ty::Predicate::Trait(ref data) => {
1556 data.0.self_ty().is_param(index)
1560 }).cloned().collect()
1564 fn re_infer(&self, span: Span, def: Option<&ty::RegionParameterDef>)
1565 -> Option<ty::Region<'tcx>> {
1567 Some(def) => infer::EarlyBoundRegion(span, def.name, def.issue_32330),
1568 None => infer::MiscVariable(span)
1570 Some(self.next_region_var(v))
1573 fn ty_infer(&self, span: Span) -> Ty<'tcx> {
1574 self.next_ty_var(TypeVariableOrigin::TypeInference(span))
1577 fn ty_infer_for_def(&self,
1578 ty_param_def: &ty::TypeParameterDef,
1579 substs: &[Kind<'tcx>],
1580 span: Span) -> Ty<'tcx> {
1581 self.type_var_for_def(span, ty_param_def, substs)
1584 fn projected_ty_from_poly_trait_ref(&self,
1586 poly_trait_ref: ty::PolyTraitRef<'tcx>,
1587 item_name: ast::Name)
1590 let (trait_ref, _) =
1591 self.replace_late_bound_regions_with_fresh_var(
1593 infer::LateBoundRegionConversionTime::AssocTypeProjection(item_name),
1596 self.tcx().mk_projection(trait_ref, item_name)
1599 fn normalize_ty(&self, span: Span, ty: Ty<'tcx>) -> Ty<'tcx> {
1600 if ty.has_escaping_regions() {
1601 ty // FIXME: normalization and escaping regions
1603 self.normalize_associated_types_in(span, &ty)
1607 fn set_tainted_by_errors(&self) {
1608 self.infcx.set_tainted_by_errors()
1612 /// Controls whether the arguments are tupled. This is used for the call
1615 /// Tupling means that all call-side arguments are packed into a tuple and
1616 /// passed as a single parameter. For example, if tupling is enabled, this
1619 /// fn f(x: (isize, isize))
1621 /// Can be called as:
1628 #[derive(Clone, Eq, PartialEq)]
1629 enum TupleArgumentsFlag {
1634 impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
1635 pub fn new(inh: &'a Inherited<'a, 'gcx, 'tcx>,
1636 body_id: ast::NodeId)
1637 -> FnCtxt<'a, 'gcx, 'tcx> {
1640 err_count_on_creation: inh.tcx.sess.err_count(),
1642 ps: RefCell::new(UnsafetyState::function(hir::Unsafety::Normal,
1643 ast::CRATE_NODE_ID)),
1644 diverges: Cell::new(Diverges::Maybe),
1645 has_errors: Cell::new(false),
1646 enclosing_breakables: RefCell::new(EnclosingBreakables {
1654 pub fn sess(&self) -> &Session {
1658 pub fn err_count_since_creation(&self) -> usize {
1659 self.tcx.sess.err_count() - self.err_count_on_creation
1662 /// Produce warning on the given node, if the current point in the
1663 /// function is unreachable, and there hasn't been another warning.
1664 fn warn_if_unreachable(&self, id: ast::NodeId, span: Span, kind: &str) {
1665 if self.diverges.get() == Diverges::Always {
1666 self.diverges.set(Diverges::WarnedAlways);
1668 debug!("warn_if_unreachable: id={:?} span={:?} kind={}", id, span, kind);
1670 self.tables.borrow_mut().lints.add_lint(
1671 lint::builtin::UNREACHABLE_CODE,
1673 format!("unreachable {}", kind));
1679 code: ObligationCauseCode<'tcx>)
1680 -> ObligationCause<'tcx> {
1681 ObligationCause::new(span, self.body_id, code)
1684 pub fn misc(&self, span: Span) -> ObligationCause<'tcx> {
1685 self.cause(span, ObligationCauseCode::MiscObligation)
1688 /// Resolves type variables in `ty` if possible. Unlike the infcx
1689 /// version (resolve_type_vars_if_possible), this version will
1690 /// also select obligations if it seems useful, in an effort
1691 /// to get more type information.
1692 fn resolve_type_vars_with_obligations(&self, mut ty: Ty<'tcx>) -> Ty<'tcx> {
1693 debug!("resolve_type_vars_with_obligations(ty={:?})", ty);
1695 // No TyInfer()? Nothing needs doing.
1696 if !ty.has_infer_types() {
1697 debug!("resolve_type_vars_with_obligations: ty={:?}", ty);
1701 // If `ty` is a type variable, see whether we already know what it is.
1702 ty = self.resolve_type_vars_if_possible(&ty);
1703 if !ty.has_infer_types() {
1704 debug!("resolve_type_vars_with_obligations: ty={:?}", ty);
1708 // If not, try resolving pending obligations as much as
1709 // possible. This can help substantially when there are
1710 // indirect dependencies that don't seem worth tracking
1712 self.select_obligations_where_possible();
1713 ty = self.resolve_type_vars_if_possible(&ty);
1715 debug!("resolve_type_vars_with_obligations: ty={:?}", ty);
1719 fn record_deferred_call_resolution(&self,
1720 closure_def_id: DefId,
1721 r: DeferredCallResolution<'gcx, 'tcx>) {
1722 let mut deferred_call_resolutions = self.deferred_call_resolutions.borrow_mut();
1723 deferred_call_resolutions.entry(closure_def_id).or_insert(vec![]).push(r);
1726 fn remove_deferred_call_resolutions(&self,
1727 closure_def_id: DefId)
1728 -> Vec<DeferredCallResolution<'gcx, 'tcx>>
1730 let mut deferred_call_resolutions = self.deferred_call_resolutions.borrow_mut();
1731 deferred_call_resolutions.remove(&closure_def_id).unwrap_or(vec![])
1734 pub fn tag(&self) -> String {
1735 let self_ptr: *const FnCtxt = self;
1736 format!("{:?}", self_ptr)
1739 pub fn local_ty(&self, span: Span, nid: ast::NodeId) -> Ty<'tcx> {
1740 match self.locals.borrow().get(&nid) {
1743 span_bug!(span, "no type for local variable {}",
1744 self.tcx.hir.node_to_string(nid));
1750 pub fn write_ty(&self, node_id: ast::NodeId, ty: Ty<'tcx>) {
1751 debug!("write_ty({}, {:?}) in fcx {}",
1752 node_id, self.resolve_type_vars_if_possible(&ty), self.tag());
1753 self.tables.borrow_mut().node_types.insert(node_id, ty);
1755 if ty.references_error() {
1756 self.has_errors.set(true);
1757 self.set_tainted_by_errors();
1761 pub fn write_substs(&self, node_id: ast::NodeId, substs: &'tcx Substs<'tcx>) {
1762 if !substs.is_noop() {
1763 debug!("write_substs({}, {:?}) in fcx {}",
1768 self.tables.borrow_mut().node_substs.insert(node_id, substs);
1772 pub fn apply_autoderef_adjustment(&self,
1773 node_id: ast::NodeId,
1774 autoderefs: Vec<Option<ty::MethodCallee<'tcx>>>,
1775 adjusted_ty: Ty<'tcx>) {
1776 self.apply_adjustment(node_id, Adjustment {
1777 kind: Adjust::DerefRef {
1786 pub fn apply_adjustment(&self, node_id: ast::NodeId, adj: Adjustment<'tcx>) {
1787 debug!("apply_adjustment(node_id={}, adj={:?})", node_id, adj);
1789 if adj.is_identity() {
1793 match self.tables.borrow_mut().adjustments.entry(node_id) {
1794 Entry::Vacant(entry) => { entry.insert(adj); },
1795 Entry::Occupied(mut entry) => {
1796 debug!(" - composing on top of {:?}", entry.get());
1797 match (&entry.get().kind, &adj.kind) {
1798 // Applying any adjustment on top of a NeverToAny
1799 // is a valid NeverToAny adjustment, because it can't
1801 (&Adjust::NeverToAny, _) => return,
1802 (&Adjust::DerefRef {
1803 autoderefs: ref old,
1804 autoref: Some(AutoBorrow::Ref(..)),
1806 }, &Adjust::DerefRef {
1807 autoderefs: ref new, ..
1808 }) if old.len() == 1 && new.len() >= 1 => {
1809 // A reborrow has no effect before a dereference.
1811 // FIXME: currently we never try to compose autoderefs
1812 // and ReifyFnPointer/UnsafeFnPointer, but we could.
1814 bug!("while adjusting {}, can't compose {:?} and {:?}",
1815 node_id, entry.get(), adj)
1817 *entry.get_mut() = adj;
1822 /// Basically whenever we are converting from a type scheme into
1823 /// the fn body space, we always want to normalize associated
1824 /// types as well. This function combines the two.
1825 fn instantiate_type_scheme<T>(&self,
1827 substs: &Substs<'tcx>,
1830 where T : TypeFoldable<'tcx>
1832 let value = value.subst(self.tcx, substs);
1833 let result = self.normalize_associated_types_in(span, &value);
1834 debug!("instantiate_type_scheme(value={:?}, substs={:?}) = {:?}",
1841 /// As `instantiate_type_scheme`, but for the bounds found in a
1842 /// generic type scheme.
1843 fn instantiate_bounds(&self, span: Span, def_id: DefId, substs: &Substs<'tcx>)
1844 -> ty::InstantiatedPredicates<'tcx> {
1845 let bounds = self.tcx.predicates_of(def_id);
1846 let result = bounds.instantiate(self.tcx, substs);
1847 let result = self.normalize_associated_types_in(span, &result);
1848 debug!("instantiate_bounds(bounds={:?}, substs={:?}) = {:?}",
1855 /// Replace all anonymized types with fresh inference variables
1856 /// and record them for writeback.
1857 fn instantiate_anon_types<T: TypeFoldable<'tcx>>(&self, value: &T) -> T {
1858 value.fold_with(&mut BottomUpFolder { tcx: self.tcx, fldop: |ty| {
1859 if let ty::TyAnon(def_id, substs) = ty.sty {
1860 // Use the same type variable if the exact same TyAnon appears more
1861 // than once in the return type (e.g. if it's pased to a type alias).
1862 let id = self.tcx.hir.as_local_node_id(def_id).unwrap();
1863 if let Some(ty_var) = self.anon_types.borrow().get(&id) {
1866 let span = self.tcx.def_span(def_id);
1867 let ty_var = self.next_ty_var(TypeVariableOrigin::TypeInference(span));
1868 self.anon_types.borrow_mut().insert(id, ty_var);
1870 let predicates_of = self.tcx.predicates_of(def_id);
1871 let bounds = predicates_of.instantiate(self.tcx, substs);
1873 for predicate in bounds.predicates {
1874 // Change the predicate to refer to the type variable,
1875 // which will be the concrete type, instead of the TyAnon.
1876 // This also instantiates nested `impl Trait`.
1877 let predicate = self.instantiate_anon_types(&predicate);
1879 // Require that the predicate holds for the concrete type.
1880 let cause = traits::ObligationCause::new(span, self.body_id,
1881 traits::ReturnType);
1882 self.register_predicate(traits::Obligation::new(cause, predicate));
1892 fn normalize_associated_types_in<T>(&self, span: Span, value: &T) -> T
1893 where T : TypeFoldable<'tcx>
1895 let ok = self.normalize_associated_types_in_as_infer_ok(span, value);
1896 self.register_infer_ok_obligations(ok)
1899 fn normalize_associated_types_in_as_infer_ok<T>(&self, span: Span, value: &T)
1901 where T : TypeFoldable<'tcx>
1903 self.inh.normalize_associated_types_in_as_infer_ok(span, self.body_id, value)
1906 pub fn write_nil(&self, node_id: ast::NodeId) {
1907 self.write_ty(node_id, self.tcx.mk_nil());
1910 pub fn write_error(&self, node_id: ast::NodeId) {
1911 self.write_ty(node_id, self.tcx.types.err);
1914 pub fn require_type_meets(&self,
1917 code: traits::ObligationCauseCode<'tcx>,
1920 self.register_bound(
1923 traits::ObligationCause::new(span, self.body_id, code));
1926 pub fn require_type_is_sized(&self,
1929 code: traits::ObligationCauseCode<'tcx>)
1931 let lang_item = self.tcx.require_lang_item(lang_items::SizedTraitLangItem);
1932 self.require_type_meets(ty, span, code, lang_item);
1935 pub fn register_bound(&self,
1938 cause: traits::ObligationCause<'tcx>)
1940 self.fulfillment_cx.borrow_mut()
1941 .register_bound(self, ty, def_id, cause);
1944 pub fn to_ty(&self, ast_t: &hir::Ty) -> Ty<'tcx> {
1945 let t = AstConv::ast_ty_to_ty(self, ast_t);
1946 self.register_wf_obligation(t, ast_t.span, traits::MiscObligation);
1950 pub fn node_ty(&self, id: ast::NodeId) -> Ty<'tcx> {
1951 match self.tables.borrow().node_types.get(&id) {
1953 None if self.err_count_since_creation() != 0 => self.tcx.types.err,
1955 bug!("no type for node {}: {} in fcx {}",
1956 id, self.tcx.hir.node_to_string(id),
1962 /// Registers an obligation for checking later, during regionck, that the type `ty` must
1963 /// outlive the region `r`.
1964 pub fn register_region_obligation(&self,
1966 region: ty::Region<'tcx>,
1967 cause: traits::ObligationCause<'tcx>)
1969 let mut fulfillment_cx = self.fulfillment_cx.borrow_mut();
1970 fulfillment_cx.register_region_obligation(ty, region, cause);
1973 /// Registers an obligation for checking later, during regionck, that the type `ty` must
1974 /// outlive the region `r`.
1975 pub fn register_wf_obligation(&self,
1978 code: traits::ObligationCauseCode<'tcx>)
1980 // WF obligations never themselves fail, so no real need to give a detailed cause:
1981 let cause = traits::ObligationCause::new(span, self.body_id, code);
1982 self.register_predicate(traits::Obligation::new(cause, ty::Predicate::WellFormed(ty)));
1985 pub fn register_old_wf_obligation(&self,
1988 code: traits::ObligationCauseCode<'tcx>)
1990 // Registers an "old-style" WF obligation that uses the
1991 // implicator code. This is basically a buggy version of
1992 // `register_wf_obligation` that is being kept around
1993 // temporarily just to help with phasing in the newer rules.
1995 // FIXME(#27579) all uses of this should be migrated to register_wf_obligation eventually
1996 let cause = traits::ObligationCause::new(span, self.body_id, code);
1997 self.register_region_obligation(ty, self.tcx.types.re_empty, cause);
2000 /// Registers obligations that all types appearing in `substs` are well-formed.
2001 pub fn add_wf_bounds(&self, substs: &Substs<'tcx>, expr: &hir::Expr)
2003 for ty in substs.types() {
2004 self.register_wf_obligation(ty, expr.span, traits::MiscObligation);
2008 /// Given a fully substituted set of bounds (`generic_bounds`), and the values with which each
2009 /// type/region parameter was instantiated (`substs`), creates and registers suitable
2010 /// trait/region obligations.
2012 /// For example, if there is a function:
2015 /// fn foo<'a,T:'a>(...)
2018 /// and a reference:
2024 /// Then we will create a fresh region variable `'$0` and a fresh type variable `$1` for `'a`
2025 /// and `T`. This routine will add a region obligation `$1:'$0` and register it locally.
2026 pub fn add_obligations_for_parameters(&self,
2027 cause: traits::ObligationCause<'tcx>,
2028 predicates: &ty::InstantiatedPredicates<'tcx>)
2030 assert!(!predicates.has_escaping_regions());
2032 debug!("add_obligations_for_parameters(predicates={:?})",
2035 for obligation in traits::predicates_for_generics(cause, predicates) {
2036 self.register_predicate(obligation);
2040 // FIXME(arielb1): use this instead of field.ty everywhere
2041 // Only for fields! Returns <none> for methods>
2042 // Indifferent to privacy flags
2043 pub fn field_ty(&self,
2045 field: &'tcx ty::FieldDef,
2046 substs: &Substs<'tcx>)
2049 self.normalize_associated_types_in(span,
2050 &field.ty(self.tcx, substs))
2053 fn check_casts(&self) {
2054 let mut deferred_cast_checks = self.deferred_cast_checks.borrow_mut();
2055 for cast in deferred_cast_checks.drain(..) {
2060 /// Apply "fallbacks" to some types
2061 /// unconstrained types get replaced with ! or () (depending on whether
2062 /// feature(never_type) is enabled), unconstrained ints with i32, and
2063 /// unconstrained floats with f64.
2064 fn default_type_parameters(&self) {
2065 use rustc::ty::error::UnconstrainedNumeric::Neither;
2066 use rustc::ty::error::UnconstrainedNumeric::{UnconstrainedInt, UnconstrainedFloat};
2068 // Defaulting inference variables becomes very dubious if we have
2069 // encountered type-checking errors. Therefore, if we think we saw
2070 // some errors in this function, just resolve all uninstanted type
2071 // varibles to TyError.
2072 if self.is_tainted_by_errors() {
2073 for ty in &self.unsolved_variables() {
2074 if let ty::TyInfer(_) = self.shallow_resolve(ty).sty {
2075 debug!("default_type_parameters: defaulting `{:?}` to error", ty);
2076 self.demand_eqtype(syntax_pos::DUMMY_SP, *ty, self.tcx().types.err);
2082 for ty in &self.unsolved_variables() {
2083 let resolved = self.resolve_type_vars_if_possible(ty);
2084 if self.type_var_diverges(resolved) {
2085 debug!("default_type_parameters: defaulting `{:?}` to `!` because it diverges",
2087 self.demand_eqtype(syntax_pos::DUMMY_SP, *ty,
2088 self.tcx.mk_diverging_default());
2090 match self.type_is_unconstrained_numeric(resolved) {
2091 UnconstrainedInt => {
2092 debug!("default_type_parameters: defaulting `{:?}` to `i32`",
2094 self.demand_eqtype(syntax_pos::DUMMY_SP, *ty, self.tcx.types.i32)
2096 UnconstrainedFloat => {
2097 debug!("default_type_parameters: defaulting `{:?}` to `f32`",
2099 self.demand_eqtype(syntax_pos::DUMMY_SP, *ty, self.tcx.types.f64)
2107 // Implements type inference fallback algorithm
2108 fn select_all_obligations_and_apply_defaults(&self) {
2109 self.select_obligations_where_possible();
2110 self.default_type_parameters();
2111 self.select_obligations_where_possible();
2114 fn select_all_obligations_or_error(&self) {
2115 debug!("select_all_obligations_or_error");
2117 // upvar inference should have ensured that all deferred call
2118 // resolutions are handled by now.
2119 assert!(self.deferred_call_resolutions.borrow().is_empty());
2121 self.select_all_obligations_and_apply_defaults();
2123 let mut fulfillment_cx = self.fulfillment_cx.borrow_mut();
2125 match fulfillment_cx.select_all_or_error(self) {
2127 Err(errors) => { self.report_fulfillment_errors(&errors); }
2131 /// Select as many obligations as we can at present.
2132 fn select_obligations_where_possible(&self) {
2133 match self.fulfillment_cx.borrow_mut().select_where_possible(self) {
2135 Err(errors) => { self.report_fulfillment_errors(&errors); }
2139 /// For the overloaded lvalue expressions (`*x`, `x[3]`), the trait
2140 /// returns a type of `&T`, but the actual type we assign to the
2141 /// *expression* is `T`. So this function just peels off the return
2142 /// type by one layer to yield `T`.
2143 fn make_overloaded_lvalue_return_type(&self,
2144 method: MethodCallee<'tcx>)
2145 -> ty::TypeAndMut<'tcx>
2147 // extract method return type, which will be &T;
2148 // all LB regions should have been instantiated during method lookup
2149 let ret_ty = method.sig.output();
2151 // method returns &T, but the type as visible to user is T, so deref
2152 ret_ty.builtin_deref(true, NoPreference).unwrap()
2155 fn lookup_indexing(&self,
2157 base_expr: &'gcx hir::Expr,
2160 lvalue_pref: LvaluePreference)
2161 -> Option<(/*index type*/ Ty<'tcx>, /*element type*/ Ty<'tcx>)>
2163 // FIXME(#18741) -- this is almost but not quite the same as the
2164 // autoderef that normal method probing does. They could likely be
2167 let mut autoderef = self.autoderef(base_expr.span, base_ty);
2168 let mut result = None;
2169 while result.is_none() && autoderef.next().is_some() {
2170 result = self.try_index_step(expr, base_expr, &autoderef, lvalue_pref, idx_ty);
2172 autoderef.finalize();
2176 /// To type-check `base_expr[index_expr]`, we progressively autoderef
2177 /// (and otherwise adjust) `base_expr`, looking for a type which either
2178 /// supports builtin indexing or overloaded indexing.
2179 /// This loop implements one step in that search; the autoderef loop
2180 /// is implemented by `lookup_indexing`.
2181 fn try_index_step(&self,
2183 base_expr: &hir::Expr,
2184 autoderef: &Autoderef<'a, 'gcx, 'tcx>,
2185 lvalue_pref: LvaluePreference,
2187 -> Option<(/*index type*/ Ty<'tcx>, /*element type*/ Ty<'tcx>)>
2189 let mut adjusted_ty = autoderef.unambiguous_final_ty();
2190 debug!("try_index_step(expr={:?}, base_expr={:?}, adjusted_ty={:?}, \
2198 // First, try built-in indexing.
2199 match (adjusted_ty.builtin_index(), &index_ty.sty) {
2200 (Some(ty), &ty::TyUint(ast::UintTy::Us)) | (Some(ty), &ty::TyInfer(ty::IntVar(_))) => {
2201 debug!("try_index_step: success, using built-in indexing");
2202 let autoderefs = autoderef.adjust_steps(lvalue_pref);
2203 self.apply_autoderef_adjustment(
2204 base_expr.id, autoderefs, adjusted_ty);
2205 return Some((self.tcx.types.usize, ty));
2210 for &unsize in &[false, true] {
2212 // We only unsize arrays here.
2213 if let ty::TyArray(element_ty, _) = adjusted_ty.sty {
2214 adjusted_ty = self.tcx.mk_slice(element_ty);
2220 // If some lookup succeeds, write callee into table and extract index/element
2221 // type from the method signature.
2222 // If some lookup succeeded, install method in table
2223 let input_ty = self.next_ty_var(TypeVariableOrigin::AutoDeref(base_expr.span));
2224 let method = self.try_overloaded_lvalue_op(
2225 expr.span, adjusted_ty, &[input_ty], lvalue_pref, LvalueOp::Index);
2227 let result = method.map(|ok| {
2228 debug!("try_index_step: success, using overloaded indexing");
2229 let (autoref, method) = self.register_infer_ok_obligations(ok);
2231 let autoderefs = autoderef.adjust_steps(lvalue_pref);
2232 self.apply_adjustment(base_expr.id, Adjustment {
2233 kind: Adjust::DerefRef {
2238 target: method.sig.inputs()[0]
2241 self.tables.borrow_mut().method_map.insert(expr.id, method);
2242 (input_ty, self.make_overloaded_lvalue_return_type(method).ty)
2244 if result.is_some() {
2252 fn resolve_lvalue_op(&self, op: LvalueOp, is_mut: bool) -> (Option<DefId>, Symbol) {
2253 let (tr, name) = match (op, is_mut) {
2254 (LvalueOp::Deref, false) =>
2255 (self.tcx.lang_items.deref_trait(), "deref"),
2256 (LvalueOp::Deref, true) =>
2257 (self.tcx.lang_items.deref_mut_trait(), "deref_mut"),
2258 (LvalueOp::Index, false) =>
2259 (self.tcx.lang_items.index_trait(), "index"),
2260 (LvalueOp::Index, true) =>
2261 (self.tcx.lang_items.index_mut_trait(), "index_mut"),
2263 (tr, Symbol::intern(name))
2266 fn try_overloaded_lvalue_op(&self,
2269 arg_tys: &[Ty<'tcx>],
2270 lvalue_pref: LvaluePreference,
2272 -> Option<InferOk<'tcx,
2273 (Option<AutoBorrow<'tcx>>,
2274 ty::MethodCallee<'tcx>)>>
2276 debug!("try_overloaded_lvalue_op({:?},{:?},{:?},{:?})",
2282 // Try Mut first, if preferred.
2283 let (mut_tr, mut_op) = self.resolve_lvalue_op(op, true);
2284 let method = match (lvalue_pref, mut_tr) {
2285 (PreferMutLvalue, Some(trait_did)) => {
2286 self.lookup_method_in_trait_adjusted(span,
2295 // Otherwise, fall back to the immutable version.
2296 let (imm_tr, imm_op) = self.resolve_lvalue_op(op, false);
2297 let method = match (method, imm_tr) {
2298 (None, Some(trait_did)) => {
2299 self.lookup_method_in_trait_adjusted(span,
2305 (method, _) => method,
2311 fn check_method_argument_types(&self,
2313 method: Result<ty::MethodCallee<'tcx>, ()>,
2314 args_no_rcvr: &'gcx [hir::Expr],
2315 tuple_arguments: TupleArgumentsFlag,
2316 expected: Expectation<'tcx>)
2318 let has_error = match method {
2320 method.substs.references_error() || method.sig.references_error()
2325 let err_inputs = self.err_args(args_no_rcvr.len());
2327 let err_inputs = match tuple_arguments {
2328 DontTupleArguments => err_inputs,
2329 TupleArguments => vec![self.tcx.intern_tup(&err_inputs[..], false)],
2332 self.check_argument_types(sp, &err_inputs[..], &[], args_no_rcvr,
2333 false, tuple_arguments, None);
2334 return self.tcx.types.err;
2337 let method = method.unwrap();
2338 // HACK(eddyb) ignore self in the definition (see above).
2339 let expected_arg_tys = self.expected_inputs_for_expected_output(
2342 method.sig.output(),
2343 &method.sig.inputs()[1..]
2345 self.check_argument_types(sp, &method.sig.inputs()[1..], &expected_arg_tys[..],
2346 args_no_rcvr, method.sig.variadic, tuple_arguments,
2347 self.tcx.hir.span_if_local(method.def_id));
2351 /// Generic function that factors out common logic from function calls,
2352 /// method calls and overloaded operators.
2353 fn check_argument_types(&self,
2355 fn_inputs: &[Ty<'tcx>],
2356 expected_arg_tys: &[Ty<'tcx>],
2357 args: &'gcx [hir::Expr],
2359 tuple_arguments: TupleArgumentsFlag,
2360 def_span: Option<Span>) {
2363 // Grab the argument types, supplying fresh type variables
2364 // if the wrong number of arguments were supplied
2365 let supplied_arg_count = if tuple_arguments == DontTupleArguments {
2371 // All the input types from the fn signature must outlive the call
2372 // so as to validate implied bounds.
2373 for &fn_input_ty in fn_inputs {
2374 self.register_wf_obligation(fn_input_ty, sp, traits::MiscObligation);
2377 let mut expected_arg_tys = expected_arg_tys;
2378 let expected_arg_count = fn_inputs.len();
2380 let sp_args = if args.len() > 0 {
2381 let (first, args) = args.split_at(1);
2382 let mut sp_tmp = first[0].span;
2384 let sp_opt = self.sess().codemap().merge_spans(sp_tmp, arg.span);
2385 if ! sp_opt.is_some() {
2388 sp_tmp = sp_opt.unwrap();
2395 fn parameter_count_error<'tcx>(sess: &Session, sp: Span, expected_count: usize,
2396 arg_count: usize, error_code: &str, variadic: bool,
2397 def_span: Option<Span>) {
2398 let mut err = sess.struct_span_err_with_code(sp,
2399 &format!("this function takes {}{} parameter{} but {} parameter{} supplied",
2400 if variadic {"at least "} else {""},
2402 if expected_count == 1 {""} else {"s"},
2404 if arg_count == 1 {" was"} else {"s were"}),
2407 err.span_label(sp, format!("expected {}{} parameter{}",
2408 if variadic {"at least "} else {""},
2410 if expected_count == 1 {""} else {"s"}));
2411 if let Some(def_s) = def_span {
2412 err.span_label(def_s, "defined here");
2417 let formal_tys = if tuple_arguments == TupleArguments {
2418 let tuple_type = self.structurally_resolved_type(sp, fn_inputs[0]);
2419 match tuple_type.sty {
2420 ty::TyTuple(arg_types, _) if arg_types.len() != args.len() => {
2421 parameter_count_error(tcx.sess, sp_args, arg_types.len(), args.len(),
2422 "E0057", false, def_span);
2423 expected_arg_tys = &[];
2424 self.err_args(args.len())
2426 ty::TyTuple(arg_types, _) => {
2427 expected_arg_tys = match expected_arg_tys.get(0) {
2428 Some(&ty) => match ty.sty {
2429 ty::TyTuple(ref tys, _) => &tys,
2437 span_err!(tcx.sess, sp, E0059,
2438 "cannot use call notation; the first type parameter \
2439 for the function trait is neither a tuple nor unit");
2440 expected_arg_tys = &[];
2441 self.err_args(args.len())
2444 } else if expected_arg_count == supplied_arg_count {
2446 } else if variadic {
2447 if supplied_arg_count >= expected_arg_count {
2450 parameter_count_error(tcx.sess, sp_args, expected_arg_count,
2451 supplied_arg_count, "E0060", true, def_span);
2452 expected_arg_tys = &[];
2453 self.err_args(supplied_arg_count)
2456 parameter_count_error(tcx.sess, sp_args, expected_arg_count,
2457 supplied_arg_count, "E0061", false, def_span);
2458 expected_arg_tys = &[];
2459 self.err_args(supplied_arg_count)
2462 debug!("check_argument_types: formal_tys={:?}",
2463 formal_tys.iter().map(|t| self.ty_to_string(*t)).collect::<Vec<String>>());
2465 // Check the arguments.
2466 // We do this in a pretty awful way: first we typecheck any arguments
2467 // that are not closures, then we typecheck the closures. This is so
2468 // that we have more information about the types of arguments when we
2469 // typecheck the functions. This isn't really the right way to do this.
2470 for &check_closures in &[false, true] {
2471 debug!("check_closures={}", check_closures);
2473 // More awful hacks: before we check argument types, try to do
2474 // an "opportunistic" vtable resolution of any trait bounds on
2475 // the call. This helps coercions.
2477 self.select_obligations_where_possible();
2480 // For variadic functions, we don't have a declared type for all of
2481 // the arguments hence we only do our usual type checking with
2482 // the arguments who's types we do know.
2483 let t = if variadic {
2485 } else if tuple_arguments == TupleArguments {
2490 for (i, arg) in args.iter().take(t).enumerate() {
2491 // Warn only for the first loop (the "no closures" one).
2492 // Closure arguments themselves can't be diverging, but
2493 // a previous argument can, e.g. `foo(panic!(), || {})`.
2494 if !check_closures {
2495 self.warn_if_unreachable(arg.id, arg.span, "expression");
2498 let is_closure = match arg.node {
2499 hir::ExprClosure(..) => true,
2503 if is_closure != check_closures {
2507 debug!("checking the argument");
2508 let formal_ty = formal_tys[i];
2510 // The special-cased logic below has three functions:
2511 // 1. Provide as good of an expected type as possible.
2512 let expected = expected_arg_tys.get(i).map(|&ty| {
2513 Expectation::rvalue_hint(self, ty)
2516 let checked_ty = self.check_expr_with_expectation(
2518 expected.unwrap_or(ExpectHasType(formal_ty)));
2520 // 2. Coerce to the most detailed type that could be coerced
2521 // to, which is `expected_ty` if `rvalue_hint` returns an
2522 // `ExpectHasType(expected_ty)`, or the `formal_ty` otherwise.
2523 let coerce_ty = expected.and_then(|e| e.only_has_type(self));
2524 self.demand_coerce(&arg, checked_ty, coerce_ty.unwrap_or(formal_ty));
2526 // 3. Relate the expected type and the formal one,
2527 // if the expected type was used for the coercion.
2528 coerce_ty.map(|ty| self.demand_suptype(arg.span, formal_ty, ty));
2532 // We also need to make sure we at least write the ty of the other
2533 // arguments which we skipped above.
2535 for arg in args.iter().skip(expected_arg_count) {
2536 let arg_ty = self.check_expr(&arg);
2538 // There are a few types which get autopromoted when passed via varargs
2539 // in C but we just error out instead and require explicit casts.
2540 let arg_ty = self.structurally_resolved_type(arg.span,
2543 ty::TyFloat(ast::FloatTy::F32) => {
2544 self.type_error_message(arg.span, |t| {
2545 format!("can't pass an `{}` to variadic \
2546 function, cast to `c_double`", t)
2549 ty::TyInt(ast::IntTy::I8) | ty::TyInt(ast::IntTy::I16) | ty::TyBool => {
2550 self.type_error_message(arg.span, |t| {
2551 format!("can't pass `{}` to variadic \
2552 function, cast to `c_int`",
2556 ty::TyUint(ast::UintTy::U8) | ty::TyUint(ast::UintTy::U16) => {
2557 self.type_error_message(arg.span, |t| {
2558 format!("can't pass `{}` to variadic \
2559 function, cast to `c_uint`",
2563 ty::TyFnDef(.., f) => {
2564 let ptr_ty = self.tcx.mk_fn_ptr(f);
2565 let ptr_ty = self.resolve_type_vars_if_possible(&ptr_ty);
2566 self.type_error_message(arg.span,
2568 format!("can't pass `{}` to variadic \
2569 function, cast to `{}`", t, ptr_ty)
2578 fn err_args(&self, len: usize) -> Vec<Ty<'tcx>> {
2579 (0..len).map(|_| self.tcx.types.err).collect()
2582 // AST fragment checking
2585 expected: Expectation<'tcx>)
2591 ast::LitKind::Str(..) => tcx.mk_static_str(),
2592 ast::LitKind::ByteStr(ref v) => {
2593 tcx.mk_imm_ref(tcx.types.re_static,
2594 tcx.mk_array(tcx.types.u8, v.len()))
2596 ast::LitKind::Byte(_) => tcx.types.u8,
2597 ast::LitKind::Char(_) => tcx.types.char,
2598 ast::LitKind::Int(_, ast::LitIntType::Signed(t)) => tcx.mk_mach_int(t),
2599 ast::LitKind::Int(_, ast::LitIntType::Unsigned(t)) => tcx.mk_mach_uint(t),
2600 ast::LitKind::Int(_, ast::LitIntType::Unsuffixed) => {
2601 let opt_ty = expected.to_option(self).and_then(|ty| {
2603 ty::TyInt(_) | ty::TyUint(_) => Some(ty),
2604 ty::TyChar => Some(tcx.types.u8),
2605 ty::TyRawPtr(..) => Some(tcx.types.usize),
2606 ty::TyFnDef(..) | ty::TyFnPtr(_) => Some(tcx.types.usize),
2610 opt_ty.unwrap_or_else(
2611 || tcx.mk_int_var(self.next_int_var_id()))
2613 ast::LitKind::Float(_, t) => tcx.mk_mach_float(t),
2614 ast::LitKind::FloatUnsuffixed(_) => {
2615 let opt_ty = expected.to_option(self).and_then(|ty| {
2617 ty::TyFloat(_) => Some(ty),
2621 opt_ty.unwrap_or_else(
2622 || tcx.mk_float_var(self.next_float_var_id()))
2624 ast::LitKind::Bool(_) => tcx.types.bool
2628 fn check_expr_eq_type(&self,
2629 expr: &'gcx hir::Expr,
2630 expected: Ty<'tcx>) {
2631 let ty = self.check_expr_with_hint(expr, expected);
2632 self.demand_eqtype(expr.span, expected, ty);
2635 pub fn check_expr_has_type(&self,
2636 expr: &'gcx hir::Expr,
2637 expected: Ty<'tcx>) -> Ty<'tcx> {
2638 let mut ty = self.check_expr_with_hint(expr, expected);
2640 // While we don't allow *arbitrary* coercions here, we *do* allow
2641 // coercions from ! to `expected`.
2643 assert!(!self.tables.borrow().adjustments.contains_key(&expr.id),
2644 "expression with never type wound up being adjusted");
2645 let adj_ty = self.next_diverging_ty_var(
2646 TypeVariableOrigin::AdjustmentType(expr.span));
2647 self.apply_adjustment(expr.id, Adjustment {
2648 kind: Adjust::NeverToAny,
2654 self.demand_suptype(expr.span, expected, ty);
2658 fn check_expr_coercable_to_type(&self,
2659 expr: &'gcx hir::Expr,
2660 expected: Ty<'tcx>) -> Ty<'tcx> {
2661 let ty = self.check_expr_with_hint(expr, expected);
2662 self.demand_coerce(expr, ty, expected);
2666 fn check_expr_with_hint(&self, expr: &'gcx hir::Expr,
2667 expected: Ty<'tcx>) -> Ty<'tcx> {
2668 self.check_expr_with_expectation(expr, ExpectHasType(expected))
2671 fn check_expr_with_expectation(&self,
2672 expr: &'gcx hir::Expr,
2673 expected: Expectation<'tcx>) -> Ty<'tcx> {
2674 self.check_expr_with_expectation_and_lvalue_pref(expr, expected, NoPreference)
2677 fn check_expr(&self, expr: &'gcx hir::Expr) -> Ty<'tcx> {
2678 self.check_expr_with_expectation(expr, NoExpectation)
2681 fn check_expr_with_lvalue_pref(&self, expr: &'gcx hir::Expr,
2682 lvalue_pref: LvaluePreference) -> Ty<'tcx> {
2683 self.check_expr_with_expectation_and_lvalue_pref(expr, NoExpectation, lvalue_pref)
2686 // determine the `self` type, using fresh variables for all variables
2687 // declared on the impl declaration e.g., `impl<A,B> for Vec<(A,B)>`
2688 // would return ($0, $1) where $0 and $1 are freshly instantiated type
2690 pub fn impl_self_ty(&self,
2691 span: Span, // (potential) receiver for this impl
2693 -> TypeAndSubsts<'tcx> {
2694 let ity = self.tcx.type_of(did);
2695 debug!("impl_self_ty: ity={:?}", ity);
2697 let substs = self.fresh_substs_for_item(span, did);
2698 let substd_ty = self.instantiate_type_scheme(span, &substs, &ity);
2700 TypeAndSubsts { substs: substs, ty: substd_ty }
2703 /// Unifies the output type with the expected type early, for more coercions
2704 /// and forward type information on the input expressions.
2705 fn expected_inputs_for_expected_output(&self,
2707 expected_ret: Expectation<'tcx>,
2708 formal_ret: Ty<'tcx>,
2709 formal_args: &[Ty<'tcx>])
2711 let expected_args = expected_ret.only_has_type(self).and_then(|ret_ty| {
2712 self.fudge_regions_if_ok(&RegionVariableOrigin::Coercion(call_span), || {
2713 // Attempt to apply a subtyping relationship between the formal
2714 // return type (likely containing type variables if the function
2715 // is polymorphic) and the expected return type.
2716 // No argument expectations are produced if unification fails.
2717 let origin = self.misc(call_span);
2718 let ures = self.sub_types(false, &origin, formal_ret, ret_ty);
2720 // FIXME(#15760) can't use try! here, FromError doesn't default
2721 // to identity so the resulting type is not constrained.
2724 // Process any obligations locally as much as
2725 // we can. We don't care if some things turn
2726 // out unconstrained or ambiguous, as we're
2727 // just trying to get hints here.
2728 let result = self.save_and_restore_in_snapshot_flag(|_| {
2729 let mut fulfill = FulfillmentContext::new();
2730 let ok = ok; // FIXME(#30046)
2731 for obligation in ok.obligations {
2732 fulfill.register_predicate_obligation(self, obligation);
2734 fulfill.select_where_possible(self)
2739 Err(_) => return Err(()),
2742 Err(_) => return Err(()),
2745 // Record all the argument types, with the substitutions
2746 // produced from the above subtyping unification.
2747 Ok(formal_args.iter().map(|ty| {
2748 self.resolve_type_vars_if_possible(ty)
2751 }).unwrap_or(vec![]);
2752 debug!("expected_inputs_for_expected_output(formal={:?} -> {:?}, expected={:?} -> {:?})",
2753 formal_args, formal_ret,
2754 expected_args, expected_ret);
2758 // Checks a method call.
2759 fn check_method_call(&self,
2760 expr: &'gcx hir::Expr,
2761 method_name: Spanned<ast::Name>,
2762 args: &'gcx [hir::Expr],
2764 expected: Expectation<'tcx>,
2765 lvalue_pref: LvaluePreference) -> Ty<'tcx> {
2766 let rcvr = &args[0];
2767 let rcvr_t = self.check_expr_with_lvalue_pref(&rcvr, lvalue_pref);
2769 // no need to check for bot/err -- callee does that
2770 let expr_t = self.structurally_resolved_type(expr.span, rcvr_t);
2772 let tps = tps.iter().map(|ast_ty| self.to_ty(&ast_ty)).collect::<Vec<_>>();
2773 let method = match self.lookup_method(method_name.span,
2780 self.tables.borrow_mut().method_map.insert(expr.id, method);
2784 if method_name.node != keywords::Invalid.name() {
2785 self.report_method_error(method_name.span,
2796 // Call the generic checker.
2797 self.check_method_argument_types(method_name.span, method,
2803 fn check_return_expr(&self, return_expr: &'gcx hir::Expr) {
2807 .unwrap_or_else(|| span_bug!(return_expr.span,
2808 "check_return_expr called outside fn body"));
2810 let ret_ty = ret_coercion.borrow().expected_ty();
2811 let return_expr_ty = self.check_expr_with_hint(return_expr, ret_ty);
2812 ret_coercion.borrow_mut()
2814 &self.misc(return_expr.span),
2817 self.diverges.get());
2821 // A generic function for checking the then and else in an if
2823 fn check_then_else(&self,
2824 cond_expr: &'gcx hir::Expr,
2825 then_expr: &'gcx hir::Expr,
2826 opt_else_expr: Option<&'gcx hir::Expr>,
2828 expected: Expectation<'tcx>) -> Ty<'tcx> {
2829 let cond_ty = self.check_expr_has_type(cond_expr, self.tcx.types.bool);
2830 let cond_diverges = self.diverges.get();
2831 self.diverges.set(Diverges::Maybe);
2833 let expected = expected.adjust_for_branches(self);
2834 let then_ty = self.check_expr_with_expectation(then_expr, expected);
2835 let then_diverges = self.diverges.get();
2836 self.diverges.set(Diverges::Maybe);
2838 // We've already taken the expected type's preferences
2839 // into account when typing the `then` branch. To figure
2840 // out the initial shot at a LUB, we thus only consider
2841 // `expected` if it represents a *hard* constraint
2842 // (`only_has_type`); otherwise, we just go with a
2843 // fresh type variable.
2844 let coerce_to_ty = expected.coercion_target_type(self, sp);
2845 let mut coerce: DynamicCoerceMany = CoerceMany::new(coerce_to_ty);
2847 let if_cause = self.cause(sp, ObligationCauseCode::IfExpression);
2848 coerce.coerce(self, &if_cause, then_expr, then_ty, then_diverges);
2850 if let Some(else_expr) = opt_else_expr {
2851 let else_ty = self.check_expr_with_expectation(else_expr, expected);
2852 let else_diverges = self.diverges.get();
2854 coerce.coerce(self, &if_cause, else_expr, else_ty, else_diverges);
2856 // We won't diverge unless both branches do (or the condition does).
2857 self.diverges.set(cond_diverges | then_diverges & else_diverges);
2859 let else_cause = self.cause(sp, ObligationCauseCode::IfExpressionWithNoElse);
2860 coerce.coerce_forced_unit(self, &else_cause, &mut |_| (), true);
2862 // If the condition is false we can't diverge.
2863 self.diverges.set(cond_diverges);
2866 let result_ty = coerce.complete(self);
2867 if cond_ty.references_error() {
2874 // Check field access expressions
2875 fn check_field(&self,
2876 expr: &'gcx hir::Expr,
2877 lvalue_pref: LvaluePreference,
2878 base: &'gcx hir::Expr,
2879 field: &Spanned<ast::Name>) -> Ty<'tcx> {
2880 let expr_t = self.check_expr_with_lvalue_pref(base, lvalue_pref);
2881 let expr_t = self.structurally_resolved_type(expr.span,
2883 let mut private_candidate = None;
2884 let mut autoderef = self.autoderef(expr.span, expr_t);
2885 while let Some((base_t, _)) = autoderef.next() {
2887 ty::TyAdt(base_def, substs) if !base_def.is_enum() => {
2888 debug!("struct named {:?}", base_t);
2889 let (ident, def_scope) =
2890 self.tcx.adjust(field.node, base_def.did, self.body_id);
2891 let fields = &base_def.struct_variant().fields;
2892 if let Some(field) = fields.iter().find(|f| f.name.to_ident() == ident) {
2893 let field_ty = self.field_ty(expr.span, field, substs);
2894 if field.vis.is_accessible_from(def_scope, self.tcx) {
2895 let autoderefs = autoderef.adjust_steps(lvalue_pref);
2896 self.apply_autoderef_adjustment(base.id, autoderefs, base_t);
2897 autoderef.finalize();
2899 self.tcx.check_stability(field.did, expr.id, expr.span);
2903 private_candidate = Some((base_def.did, field_ty));
2909 autoderef.unambiguous_final_ty();
2911 if let Some((did, field_ty)) = private_candidate {
2912 let struct_path = self.tcx().item_path_str(did);
2913 let msg = format!("field `{}` of struct `{}` is private", field.node, struct_path);
2914 let mut err = self.tcx().sess.struct_span_err(expr.span, &msg);
2915 // Also check if an accessible method exists, which is often what is meant.
2916 if self.method_exists(field.span, field.node, expr_t, expr.id, false) {
2917 err.note(&format!("a method `{}` also exists, perhaps you wish to call it",
2922 } else if field.node == keywords::Invalid.name() {
2923 self.tcx().types.err
2924 } else if self.method_exists(field.span, field.node, expr_t, expr.id, true) {
2925 self.type_error_struct(field.span, |actual| {
2926 format!("attempted to take value of method `{}` on type \
2927 `{}`", field.node, actual)
2929 .help("maybe a `()` to call it is missing? \
2930 If not, try an anonymous function")
2932 self.tcx().types.err
2934 let mut err = self.type_error_struct(field.span, |actual| {
2935 format!("no field `{}` on type `{}`",
2939 ty::TyAdt(def, _) if !def.is_enum() => {
2940 if let Some(suggested_field_name) =
2941 Self::suggest_field_name(def.struct_variant(), field, vec![]) {
2942 err.span_label(field.span,
2943 format!("did you mean `{}`?", suggested_field_name));
2945 err.span_label(field.span,
2949 ty::TyRawPtr(..) => {
2950 err.note(&format!("`{0}` is a native pointer; perhaps you need to deref with \
2952 self.tcx.hir.node_to_pretty_string(base.id),
2958 self.tcx().types.err
2962 // Return an hint about the closest match in field names
2963 fn suggest_field_name(variant: &'tcx ty::VariantDef,
2964 field: &Spanned<ast::Name>,
2965 skip : Vec<InternedString>)
2967 let name = field.node.as_str();
2968 let names = variant.fields.iter().filter_map(|field| {
2969 // ignore already set fields and private fields from non-local crates
2970 if skip.iter().any(|x| *x == field.name.as_str()) ||
2971 (variant.did.krate != LOCAL_CRATE && field.vis != Visibility::Public) {
2978 // only find fits with at least one matching letter
2979 find_best_match_for_name(names, &name, Some(name.len()))
2982 // Check tuple index expressions
2983 fn check_tup_field(&self,
2984 expr: &'gcx hir::Expr,
2985 lvalue_pref: LvaluePreference,
2986 base: &'gcx hir::Expr,
2987 idx: codemap::Spanned<usize>) -> Ty<'tcx> {
2988 let expr_t = self.check_expr_with_lvalue_pref(base, lvalue_pref);
2989 let expr_t = self.structurally_resolved_type(expr.span,
2991 let mut private_candidate = None;
2992 let mut tuple_like = false;
2993 let mut autoderef = self.autoderef(expr.span, expr_t);
2994 while let Some((base_t, _)) = autoderef.next() {
2995 let field = match base_t.sty {
2996 ty::TyAdt(base_def, substs) if base_def.is_struct() => {
2997 tuple_like = base_def.struct_variant().ctor_kind == CtorKind::Fn;
2998 if !tuple_like { continue }
3000 debug!("tuple struct named {:?}", base_t);
3001 let ident = ast::Ident {
3002 name: Symbol::intern(&idx.node.to_string()),
3003 ctxt: idx.span.ctxt.modern(),
3005 let (ident, def_scope) =
3006 self.tcx.adjust_ident(ident, base_def.did, self.body_id);
3007 let fields = &base_def.struct_variant().fields;
3008 if let Some(field) = fields.iter().find(|f| f.name.to_ident() == ident) {
3009 let field_ty = self.field_ty(expr.span, field, substs);
3010 if field.vis.is_accessible_from(def_scope, self.tcx) {
3011 self.tcx.check_stability(field.did, expr.id, expr.span);
3014 private_candidate = Some((base_def.did, field_ty));
3021 ty::TyTuple(ref v, _) => {
3023 v.get(idx.node).cloned()
3028 if let Some(field_ty) = field {
3029 let autoderefs = autoderef.adjust_steps(lvalue_pref);
3030 self.apply_autoderef_adjustment(base.id, autoderefs, base_t);
3031 autoderef.finalize();
3035 autoderef.unambiguous_final_ty();
3037 if let Some((did, field_ty)) = private_candidate {
3038 let struct_path = self.tcx().item_path_str(did);
3039 let msg = format!("field `{}` of struct `{}` is private", idx.node, struct_path);
3040 self.tcx().sess.span_err(expr.span, &msg);
3044 self.type_error_message(
3048 format!("attempted out-of-bounds tuple index `{}` on \
3053 format!("attempted tuple index `{}` on type `{}`, but the \
3054 type was not a tuple or tuple struct",
3061 self.tcx().types.err
3064 fn report_unknown_field(&self,
3066 variant: &'tcx ty::VariantDef,
3068 skip_fields: &[hir::Field],
3070 let mut err = self.type_error_struct_with_diag(
3072 |actual| match ty.sty {
3073 ty::TyAdt(adt, ..) if adt.is_enum() => {
3074 struct_span_err!(self.tcx.sess, field.name.span, E0559,
3075 "{} `{}::{}` has no field named `{}`",
3076 kind_name, actual, variant.name, field.name.node)
3079 struct_span_err!(self.tcx.sess, field.name.span, E0560,
3080 "{} `{}` has no field named `{}`",
3081 kind_name, actual, field.name.node)
3085 // prevent all specified fields from being suggested
3086 let skip_fields = skip_fields.iter().map(|ref x| x.name.node.as_str());
3087 if let Some(field_name) = Self::suggest_field_name(variant,
3089 skip_fields.collect()) {
3090 err.span_label(field.name.span,
3091 format!("field does not exist - did you mean `{}`?", field_name));
3094 ty::TyAdt(adt, ..) if adt.is_enum() => {
3095 err.span_label(field.name.span, format!("`{}::{}` does not have this field",
3099 err.span_label(field.name.span, format!("`{}` does not have this field", ty));
3106 fn check_expr_struct_fields(&self,
3108 expected: Expectation<'tcx>,
3109 expr_id: ast::NodeId,
3111 variant: &'tcx ty::VariantDef,
3112 ast_fields: &'gcx [hir::Field],
3113 check_completeness: bool) {
3117 self.expected_inputs_for_expected_output(span, expected, adt_ty, &[adt_ty])
3118 .get(0).cloned().unwrap_or(adt_ty);
3120 let (substs, hint_substs, adt_kind, kind_name) = match (&adt_ty.sty, &adt_ty_hint.sty) {
3121 (&ty::TyAdt(adt, substs), &ty::TyAdt(_, hint_substs)) => {
3122 (substs, hint_substs, adt.adt_kind(), adt.variant_descr())
3124 _ => span_bug!(span, "non-ADT passed to check_expr_struct_fields")
3127 let mut remaining_fields = FxHashMap();
3128 for field in &variant.fields {
3129 remaining_fields.insert(field.name.to_ident(), field);
3132 let mut seen_fields = FxHashMap();
3134 let mut error_happened = false;
3136 // Typecheck each field.
3137 for field in ast_fields {
3138 let final_field_type;
3139 let field_type_hint;
3141 let ident = tcx.adjust(field.name.node, variant.did, self.body_id).0;
3142 if let Some(v_field) = remaining_fields.remove(&ident) {
3143 final_field_type = self.field_ty(field.span, v_field, substs);
3144 field_type_hint = self.field_ty(field.span, v_field, hint_substs);
3146 seen_fields.insert(field.name.node, field.span);
3148 // we don't look at stability attributes on
3149 // struct-like enums (yet...), but it's definitely not
3150 // a bug to have construct one.
3151 if adt_kind != ty::AdtKind::Enum {
3152 tcx.check_stability(v_field.did, expr_id, field.span);
3155 error_happened = true;
3156 final_field_type = tcx.types.err;
3157 field_type_hint = tcx.types.err;
3158 if let Some(_) = variant.find_field_named(field.name.node) {
3159 let mut err = struct_span_err!(self.tcx.sess,
3162 "field `{}` specified more than once",
3165 err.span_label(field.name.span, "used more than once");
3167 if let Some(prev_span) = seen_fields.get(&field.name.node) {
3168 err.span_label(*prev_span, format!("first use of `{}`", field.name.node));
3173 self.report_unknown_field(adt_ty, variant, field, ast_fields, kind_name);
3177 // Make sure to give a type to the field even if there's
3178 // an error, so we can continue typechecking
3179 let ty = self.check_expr_with_hint(&field.expr, field_type_hint);
3180 self.demand_coerce(&field.expr, ty, final_field_type);
3183 // Make sure the programmer specified correct number of fields.
3184 if kind_name == "union" {
3185 if ast_fields.len() != 1 {
3186 tcx.sess.span_err(span, "union expressions should have exactly one field");
3188 } else if check_completeness && !error_happened && !remaining_fields.is_empty() {
3189 let len = remaining_fields.len();
3191 let mut displayable_field_names = remaining_fields
3193 .map(|ident| ident.name.as_str())
3194 .collect::<Vec<_>>();
3196 displayable_field_names.sort();
3198 let truncated_fields_error = if len <= 3 {
3201 format!(" and {} other field{}", (len - 3), if len - 3 == 1 {""} else {"s"})
3204 let remaining_fields_names = displayable_field_names.iter().take(3)
3205 .map(|n| format!("`{}`", n))
3206 .collect::<Vec<_>>()
3209 struct_span_err!(tcx.sess, span, E0063,
3210 "missing field{} {}{} in initializer of `{}`",
3211 if remaining_fields.len() == 1 {""} else {"s"},
3212 remaining_fields_names,
3213 truncated_fields_error,
3215 .span_label(span, format!("missing {}{}",
3216 remaining_fields_names,
3217 truncated_fields_error))
3222 fn check_struct_fields_on_error(&self,
3223 fields: &'gcx [hir::Field],
3224 base_expr: &'gcx Option<P<hir::Expr>>) {
3225 for field in fields {
3226 self.check_expr(&field.expr);
3230 self.check_expr(&base);
3236 pub fn check_struct_path(&self,
3238 node_id: ast::NodeId)
3239 -> Option<(&'tcx ty::VariantDef, Ty<'tcx>)> {
3240 let path_span = match *qpath {
3241 hir::QPath::Resolved(_, ref path) => path.span,
3242 hir::QPath::TypeRelative(ref qself, _) => qself.span
3244 let (def, ty) = self.finish_resolving_struct_path(qpath, path_span, node_id);
3245 let variant = match def {
3247 self.set_tainted_by_errors();
3250 Def::Variant(..) => {
3252 ty::TyAdt(adt, substs) => {
3253 Some((adt.variant_of_def(def), adt.did, substs))
3255 _ => bug!("unexpected type: {:?}", ty.sty)
3258 Def::Struct(..) | Def::Union(..) | Def::TyAlias(..) |
3259 Def::AssociatedTy(..) | Def::SelfTy(..) => {
3261 ty::TyAdt(adt, substs) if !adt.is_enum() => {
3262 Some((adt.struct_variant(), adt.did, substs))
3267 _ => bug!("unexpected definition: {:?}", def)
3270 if let Some((variant, did, substs)) = variant {
3271 // Check bounds on type arguments used in the path.
3272 let bounds = self.instantiate_bounds(path_span, did, substs);
3273 let cause = traits::ObligationCause::new(path_span, self.body_id,
3274 traits::ItemObligation(did));
3275 self.add_obligations_for_parameters(cause, &bounds);
3279 struct_span_err!(self.tcx.sess, path_span, E0071,
3280 "expected struct, variant or union type, found {}",
3281 ty.sort_string(self.tcx))
3282 .span_label(path_span, "not a struct")
3288 fn check_expr_struct(&self,
3290 expected: Expectation<'tcx>,
3292 fields: &'gcx [hir::Field],
3293 base_expr: &'gcx Option<P<hir::Expr>>) -> Ty<'tcx>
3295 // Find the relevant variant
3296 let (variant, struct_ty) =
3297 if let Some(variant_ty) = self.check_struct_path(qpath, expr.id) {
3300 self.check_struct_fields_on_error(fields, base_expr);
3301 return self.tcx.types.err;
3304 let path_span = match *qpath {
3305 hir::QPath::Resolved(_, ref path) => path.span,
3306 hir::QPath::TypeRelative(ref qself, _) => qself.span
3309 self.check_expr_struct_fields(struct_ty, expected, expr.id, path_span, variant, fields,
3310 base_expr.is_none());
3311 if let &Some(ref base_expr) = base_expr {
3312 self.check_expr_has_type(base_expr, struct_ty);
3313 match struct_ty.sty {
3314 ty::TyAdt(adt, substs) if adt.is_struct() => {
3315 self.tables.borrow_mut().fru_field_types.insert(
3317 adt.struct_variant().fields.iter().map(|f| {
3318 self.normalize_associated_types_in(
3319 expr.span, &f.ty(self.tcx, substs)
3325 span_err!(self.tcx.sess, base_expr.span, E0436,
3326 "functional record update syntax requires a struct");
3330 self.require_type_is_sized(struct_ty, expr.span, traits::StructInitializerSized);
3336 /// If an expression has any sub-expressions that result in a type error,
3337 /// inspecting that expression's type with `ty.references_error()` will return
3338 /// true. Likewise, if an expression is known to diverge, inspecting its
3339 /// type with `ty::type_is_bot` will return true (n.b.: since Rust is
3340 /// strict, _|_ can appear in the type of an expression that does not,
3341 /// itself, diverge: for example, fn() -> _|_.)
3342 /// Note that inspecting a type's structure *directly* may expose the fact
3343 /// that there are actually multiple representations for `TyError`, so avoid
3344 /// that when err needs to be handled differently.
3345 fn check_expr_with_expectation_and_lvalue_pref(&self,
3346 expr: &'gcx hir::Expr,
3347 expected: Expectation<'tcx>,
3348 lvalue_pref: LvaluePreference) -> Ty<'tcx> {
3349 debug!(">> typechecking: expr={:?} expected={:?}",
3352 // Warn for expressions after diverging siblings.
3353 self.warn_if_unreachable(expr.id, expr.span, "expression");
3355 // Hide the outer diverging and has_errors flags.
3356 let old_diverges = self.diverges.get();
3357 let old_has_errors = self.has_errors.get();
3358 self.diverges.set(Diverges::Maybe);
3359 self.has_errors.set(false);
3361 let ty = self.check_expr_kind(expr, expected, lvalue_pref);
3363 // Warn for non-block expressions with diverging children.
3366 hir::ExprLoop(..) | hir::ExprWhile(..) |
3367 hir::ExprIf(..) | hir::ExprMatch(..) => {}
3369 _ => self.warn_if_unreachable(expr.id, expr.span, "expression")
3372 // Any expression that produces a value of type `!` must have diverged
3374 self.diverges.set(self.diverges.get() | Diverges::Always);
3377 // Record the type, which applies it effects.
3378 // We need to do this after the warning above, so that
3379 // we don't warn for the diverging expression itself.
3380 self.write_ty(expr.id, ty);
3382 // Combine the diverging and has_error flags.
3383 self.diverges.set(self.diverges.get() | old_diverges);
3384 self.has_errors.set(self.has_errors.get() | old_has_errors);
3386 debug!("type of {} is...", self.tcx.hir.node_to_string(expr.id));
3387 debug!("... {:?}, expected is {:?}", ty, expected);
3392 fn check_expr_kind(&self,
3393 expr: &'gcx hir::Expr,
3394 expected: Expectation<'tcx>,
3395 lvalue_pref: LvaluePreference) -> Ty<'tcx> {
3399 hir::ExprBox(ref subexpr) => {
3400 let expected_inner = expected.to_option(self).map_or(NoExpectation, |ty| {
3402 ty::TyAdt(def, _) if def.is_box()
3403 => Expectation::rvalue_hint(self, ty.boxed_ty()),
3407 let referent_ty = self.check_expr_with_expectation(subexpr, expected_inner);
3408 tcx.mk_box(referent_ty)
3411 hir::ExprLit(ref lit) => {
3412 self.check_lit(&lit, expected)
3414 hir::ExprBinary(op, ref lhs, ref rhs) => {
3415 self.check_binop(expr, op, lhs, rhs)
3417 hir::ExprAssignOp(op, ref lhs, ref rhs) => {
3418 self.check_binop_assign(expr, op, lhs, rhs)
3420 hir::ExprUnary(unop, ref oprnd) => {
3421 let expected_inner = match unop {
3422 hir::UnNot | hir::UnNeg => {
3429 let lvalue_pref = match unop {
3430 hir::UnDeref => lvalue_pref,
3433 let mut oprnd_t = self.check_expr_with_expectation_and_lvalue_pref(&oprnd,
3437 if !oprnd_t.references_error() {
3440 oprnd_t = self.structurally_resolved_type(expr.span, oprnd_t);
3442 if let Some(mt) = oprnd_t.builtin_deref(true, NoPreference) {
3444 } else if let Some(ok) = self.try_overloaded_deref(
3445 expr.span, oprnd_t, lvalue_pref) {
3446 let (autoref, method) = self.register_infer_ok_obligations(ok);
3447 self.apply_adjustment(oprnd.id, Adjustment {
3448 kind: Adjust::DerefRef {
3453 target: method.sig.inputs()[0]
3455 oprnd_t = self.make_overloaded_lvalue_return_type(method).ty;
3456 self.tables.borrow_mut().method_map.insert(expr.id, method);
3458 self.type_error_message(expr.span, |actual| {
3459 format!("type `{}` cannot be \
3460 dereferenced", actual)
3462 oprnd_t = tcx.types.err;
3466 oprnd_t = self.structurally_resolved_type(oprnd.span,
3468 let result = self.check_user_unop("!", "not",
3469 tcx.lang_items.not_trait(),
3470 expr, &oprnd, oprnd_t, unop);
3471 // If it's builtin, we can reuse the type, this helps inference.
3472 if !(oprnd_t.is_integral() || oprnd_t.sty == ty::TyBool) {
3477 oprnd_t = self.structurally_resolved_type(oprnd.span,
3479 let result = self.check_user_unop("-", "neg",
3480 tcx.lang_items.neg_trait(),
3481 expr, &oprnd, 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_relative_path_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_relative_path_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_relative_path_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_relative_path_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_types(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.sub_types(false, &self.misc(span), self_ty, impl_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")