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.item_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::coercion::{CoerceMany, DynamicCoerceMany};
81 pub use self::compare_method::{compare_impl_method, compare_const_impl};
82 use self::TupleArgumentsFlag::*;
85 use dep_graph::DepNode;
86 use fmt_macros::{Parser, Piece, Position};
87 use hir::def::{Def, CtorKind};
88 use hir::def_id::{CrateNum, DefId, LOCAL_CRATE};
89 use rustc_back::slice::ref_slice;
90 use rustc::infer::{self, InferCtxt, InferOk, RegionVariableOrigin};
91 use rustc::infer::type_variable::{TypeVariableOrigin};
92 use rustc::ty::subst::{Kind, Subst, Substs};
93 use rustc::traits::{self, ObligationCause, ObligationCauseCode, Reveal};
94 use rustc::ty::{ParamTy, ParameterEnvironment};
95 use rustc::ty::{LvaluePreference, NoPreference, PreferMutLvalue};
96 use rustc::ty::{self, Ty, TyCtxt, Visibility};
97 use rustc::ty::{MethodCall, MethodCallee};
98 use rustc::ty::adjustment;
99 use rustc::ty::fold::{BottomUpFolder, TypeFoldable};
100 use rustc::ty::maps::Providers;
101 use rustc::ty::util::{Representability, IntTypeExt};
102 use errors::DiagnosticBuilder;
103 use require_c_abi_if_variadic;
104 use session::{Session, CompileResult};
107 use util::common::{ErrorReported, indenter};
108 use util::nodemap::{DefIdMap, FxHashMap, NodeMap};
110 use std::cell::{Cell, RefCell};
112 use std::mem::replace;
113 use std::ops::{self, Deref};
114 use syntax::abi::Abi;
116 use syntax::codemap::{self, original_sp, Spanned};
117 use syntax::feature_gate::{GateIssue, emit_feature_err};
119 use syntax::symbol::{Symbol, InternedString, keywords};
120 use syntax::util::lev_distance::find_best_match_for_name;
121 use syntax_pos::{self, BytePos, Span, DUMMY_SP};
123 use rustc::hir::intravisit::{self, Visitor, NestedVisitorMap};
124 use rustc::hir::itemlikevisit::ItemLikeVisitor;
125 use rustc::hir::{self, PatKind};
126 use rustc::middle::lang_items;
127 use rustc_back::slice;
128 use rustc_const_eval::eval_length;
129 use rustc_const_math::ConstInt;
149 /// closures defined within the function. For example:
152 /// bar(move|| { ... })
155 /// Here, the function `foo()` and the closure passed to
156 /// `bar()` will each have their own `FnCtxt`, but they will
157 /// share the inherited fields.
158 pub struct Inherited<'a, 'gcx: 'a+'tcx, 'tcx: 'a> {
159 infcx: InferCtxt<'a, 'gcx, 'tcx>,
161 locals: RefCell<NodeMap<Ty<'tcx>>>,
163 fulfillment_cx: RefCell<traits::FulfillmentContext<'tcx>>,
165 // When we process a call like `c()` where `c` is a closure type,
166 // we may not have decided yet whether `c` is a `Fn`, `FnMut`, or
167 // `FnOnce` closure. In that case, we defer full resolution of the
168 // call until upvar inference can kick in and make the
169 // decision. We keep these deferred resolutions grouped by the
170 // def-id of the closure, so that once we decide, we can easily go
171 // back and process them.
172 deferred_call_resolutions: RefCell<DefIdMap<Vec<DeferredCallResolutionHandler<'gcx, 'tcx>>>>,
174 deferred_cast_checks: RefCell<Vec<cast::CastCheck<'tcx>>>,
176 // Anonymized types found in explicit return types and their
177 // associated fresh inference variable. Writeback resolves these
178 // variables to get the concrete type, which can be used to
179 // deanonymize TyAnon, after typeck is done with all functions.
180 anon_types: RefCell<NodeMap<Ty<'tcx>>>,
183 impl<'a, 'gcx, 'tcx> Deref for Inherited<'a, 'gcx, 'tcx> {
184 type Target = InferCtxt<'a, 'gcx, 'tcx>;
185 fn deref(&self) -> &Self::Target {
190 trait DeferredCallResolution<'gcx, 'tcx> {
191 fn resolve<'a>(&mut self, fcx: &FnCtxt<'a, 'gcx, 'tcx>);
194 type DeferredCallResolutionHandler<'gcx, 'tcx> = Box<DeferredCallResolution<'gcx, 'tcx>+'tcx>;
196 /// When type-checking an expression, we propagate downward
197 /// whatever type hint we are able in the form of an `Expectation`.
198 #[derive(Copy, Clone, Debug)]
199 pub enum Expectation<'tcx> {
200 /// We know nothing about what type this expression should have.
203 /// This expression should have the type given (or some subtype)
204 ExpectHasType(Ty<'tcx>),
206 /// This expression will be cast to the `Ty`
207 ExpectCastableToType(Ty<'tcx>),
209 /// This rvalue expression will be wrapped in `&` or `Box` and coerced
210 /// to `&Ty` or `Box<Ty>`, respectively. `Ty` is `[A]` or `Trait`.
211 ExpectRvalueLikeUnsized(Ty<'tcx>),
214 impl<'a, 'gcx, 'tcx> Expectation<'tcx> {
215 // Disregard "castable to" expectations because they
216 // can lead us astray. Consider for example `if cond
217 // {22} else {c} as u8` -- if we propagate the
218 // "castable to u8" constraint to 22, it will pick the
219 // type 22u8, which is overly constrained (c might not
220 // be a u8). In effect, the problem is that the
221 // "castable to" expectation is not the tightest thing
222 // we can say, so we want to drop it in this case.
223 // The tightest thing we can say is "must unify with
224 // else branch". Note that in the case of a "has type"
225 // constraint, this limitation does not hold.
227 // If the expected type is just a type variable, then don't use
228 // an expected type. Otherwise, we might write parts of the type
229 // when checking the 'then' block which are incompatible with the
231 fn adjust_for_branches(&self, fcx: &FnCtxt<'a, 'gcx, 'tcx>) -> Expectation<'tcx> {
233 ExpectHasType(ety) => {
234 let ety = fcx.shallow_resolve(ety);
235 if !ety.is_ty_var() {
241 ExpectRvalueLikeUnsized(ety) => {
242 ExpectRvalueLikeUnsized(ety)
248 /// Provide an expectation for an rvalue expression given an *optional*
249 /// hint, which is not required for type safety (the resulting type might
250 /// be checked higher up, as is the case with `&expr` and `box expr`), but
251 /// is useful in determining the concrete type.
253 /// The primary use case is where the expected type is a fat pointer,
254 /// like `&[isize]`. For example, consider the following statement:
256 /// let x: &[isize] = &[1, 2, 3];
258 /// In this case, the expected type for the `&[1, 2, 3]` expression is
259 /// `&[isize]`. If however we were to say that `[1, 2, 3]` has the
260 /// expectation `ExpectHasType([isize])`, that would be too strong --
261 /// `[1, 2, 3]` does not have the type `[isize]` but rather `[isize; 3]`.
262 /// It is only the `&[1, 2, 3]` expression as a whole that can be coerced
263 /// to the type `&[isize]`. Therefore, we propagate this more limited hint,
264 /// which still is useful, because it informs integer literals and the like.
265 /// See the test case `test/run-pass/coerce-expect-unsized.rs` and #20169
266 /// for examples of where this comes up,.
267 fn rvalue_hint(fcx: &FnCtxt<'a, 'gcx, 'tcx>, ty: Ty<'tcx>) -> Expectation<'tcx> {
268 match fcx.tcx.struct_tail(ty).sty {
269 ty::TySlice(_) | ty::TyStr | ty::TyDynamic(..) => {
270 ExpectRvalueLikeUnsized(ty)
272 _ => ExpectHasType(ty)
276 // Resolves `expected` by a single level if it is a variable. If
277 // there is no expected type or resolution is not possible (e.g.,
278 // no constraints yet present), just returns `None`.
279 fn resolve(self, fcx: &FnCtxt<'a, 'gcx, 'tcx>) -> Expectation<'tcx> {
284 ExpectCastableToType(t) => {
285 ExpectCastableToType(fcx.resolve_type_vars_if_possible(&t))
287 ExpectHasType(t) => {
288 ExpectHasType(fcx.resolve_type_vars_if_possible(&t))
290 ExpectRvalueLikeUnsized(t) => {
291 ExpectRvalueLikeUnsized(fcx.resolve_type_vars_if_possible(&t))
296 fn to_option(self, fcx: &FnCtxt<'a, 'gcx, 'tcx>) -> Option<Ty<'tcx>> {
297 match self.resolve(fcx) {
298 NoExpectation => None,
299 ExpectCastableToType(ty) |
301 ExpectRvalueLikeUnsized(ty) => Some(ty),
305 /// It sometimes happens that we want to turn an expectation into
306 /// a **hard constraint** (i.e., something that must be satisfied
307 /// for the program to type-check). `only_has_type` will return
308 /// such a constraint, if it exists.
309 fn only_has_type(self, fcx: &FnCtxt<'a, 'gcx, 'tcx>) -> Option<Ty<'tcx>> {
310 match self.resolve(fcx) {
311 ExpectHasType(ty) => Some(ty),
316 /// Like `only_has_type`, but instead of returning `None` if no
317 /// hard constraint exists, creates a fresh type variable.
318 fn coercion_target_type(self, fcx: &FnCtxt<'a, 'gcx, 'tcx>, span: Span) -> Ty<'tcx> {
319 self.only_has_type(fcx)
320 .unwrap_or_else(|| fcx.next_ty_var(TypeVariableOrigin::MiscVariable(span)))
324 #[derive(Copy, Clone)]
325 pub struct UnsafetyState {
326 pub def: ast::NodeId,
327 pub unsafety: hir::Unsafety,
328 pub unsafe_push_count: u32,
333 pub fn function(unsafety: hir::Unsafety, def: ast::NodeId) -> UnsafetyState {
334 UnsafetyState { def: def, unsafety: unsafety, unsafe_push_count: 0, from_fn: true }
337 pub fn recurse(&mut self, blk: &hir::Block) -> UnsafetyState {
338 match self.unsafety {
339 // If this unsafe, then if the outer function was already marked as
340 // unsafe we shouldn't attribute the unsafe'ness to the block. This
341 // way the block can be warned about instead of ignoring this
342 // extraneous block (functions are never warned about).
343 hir::Unsafety::Unsafe if self.from_fn => *self,
346 let (unsafety, def, count) = match blk.rules {
347 hir::PushUnsafeBlock(..) =>
348 (unsafety, blk.id, self.unsafe_push_count.checked_add(1).unwrap()),
349 hir::PopUnsafeBlock(..) =>
350 (unsafety, blk.id, self.unsafe_push_count.checked_sub(1).unwrap()),
351 hir::UnsafeBlock(..) =>
352 (hir::Unsafety::Unsafe, blk.id, self.unsafe_push_count),
354 (unsafety, self.def, self.unsafe_push_count),
356 UnsafetyState{ def: def,
358 unsafe_push_count: count,
365 /// Tracks whether executing a node may exit normally (versus
366 /// return/break/panic, which "diverge", leaving dead code in their
367 /// wake). Tracked semi-automatically (through type variables marked
368 /// as diverging), with some manual adjustments for control-flow
369 /// primitives (approximating a CFG).
370 #[derive(Copy, Clone, Debug, PartialEq, Eq, PartialOrd, Ord)]
372 /// Potentially unknown, some cases converge,
373 /// others require a CFG to determine them.
376 /// Definitely known to diverge and therefore
377 /// not reach the next sibling or its parent.
380 /// Same as `Always` but with a reachability
381 /// warning already emitted
385 // Convenience impls for combinig `Diverges`.
387 impl ops::BitAnd for Diverges {
389 fn bitand(self, other: Self) -> Self {
390 cmp::min(self, other)
394 impl ops::BitOr for Diverges {
396 fn bitor(self, other: Self) -> Self {
397 cmp::max(self, other)
401 impl ops::BitAndAssign for Diverges {
402 fn bitand_assign(&mut self, other: Self) {
403 *self = *self & other;
407 impl ops::BitOrAssign for Diverges {
408 fn bitor_assign(&mut self, other: Self) {
409 *self = *self | other;
414 fn always(self) -> bool {
415 self >= Diverges::Always
419 pub struct BreakableCtxt<'gcx: 'tcx, 'tcx> {
422 // this is `null` for loops where break with a value is illegal,
423 // such as `while`, `for`, and `while let`
424 coerce: Option<DynamicCoerceMany<'gcx, 'tcx>>,
427 pub struct EnclosingBreakables<'gcx: 'tcx, 'tcx> {
428 stack: Vec<BreakableCtxt<'gcx, 'tcx>>,
429 by_id: NodeMap<usize>,
432 impl<'gcx, 'tcx> EnclosingBreakables<'gcx, 'tcx> {
433 fn find_breakable(&mut self, target_id: ast::NodeId) -> &mut BreakableCtxt<'gcx, 'tcx> {
434 let ix = *self.by_id.get(&target_id).unwrap_or_else(|| {
435 bug!("could not find enclosing breakable with id {}", target_id);
441 pub struct FnCtxt<'a, 'gcx: 'a+'tcx, 'tcx: 'a> {
442 ast_ty_to_ty_cache: RefCell<NodeMap<Ty<'tcx>>>,
444 body_id: ast::NodeId,
446 // Number of errors that had been reported when we started
447 // checking this function. On exit, if we find that *more* errors
448 // have been reported, we will skip regionck and other work that
449 // expects the types within the function to be consistent.
450 err_count_on_creation: usize,
452 ret_coercion: Option<RefCell<DynamicCoerceMany<'gcx, 'tcx>>>,
454 ps: RefCell<UnsafetyState>,
456 /// Whether the last checked node generates a divergence (e.g.,
457 /// `return` will set this to Always). In general, when entering
458 /// an expression or other node in the tree, the initial value
459 /// indicates whether prior parts of the containing expression may
460 /// have diverged. It is then typically set to `Maybe` (and the
461 /// old value remembered) for processing the subparts of the
462 /// current expression. As each subpart is processed, they may set
463 /// the flag to `Always` etc. Finally, at the end, we take the
464 /// result and "union" it with the original value, so that when we
465 /// return the flag indicates if any subpart of the the parent
466 /// expression (up to and including this part) has diverged. So,
467 /// if you read it after evaluating a subexpression `X`, the value
468 /// you get indicates whether any subexpression that was
469 /// evaluating up to and including `X` diverged.
471 /// We use this flag for two purposes:
473 /// - To warn about unreachable code: if, after processing a
474 /// sub-expression but before we have applied the effects of the
475 /// current node, we see that the flag is set to `Always`, we
476 /// can issue a warning. This corresponds to something like
477 /// `foo(return)`; we warn on the `foo()` expression. (We then
478 /// update the flag to `WarnedAlways` to suppress duplicate
479 /// reports.) Similarly, if we traverse to a fresh statement (or
480 /// tail expression) from a `Always` setting, we will isssue a
481 /// warning. This corresponds to something like `{return;
482 /// foo();}` or `{return; 22}`, where we would warn on the
485 /// - To permit assignment into a local variable or other lvalue
486 /// (including the "return slot") of type `!`. This is allowed
487 /// if **either** the type of value being assigned is `!`, which
488 /// means the current code is dead, **or** the expression's
489 /// divering flag is true, which means that a divering value was
490 /// wrapped (e.g., `let x: ! = foo(return)`).
492 /// To repeat the last point: an expression represents dead-code
493 /// if, after checking it, **either** its type is `!` OR the
494 /// diverges flag is set to something other than `Maybe`.
495 diverges: Cell<Diverges>,
497 /// Whether any child nodes have any type errors.
498 has_errors: Cell<bool>,
500 enclosing_breakables: RefCell<EnclosingBreakables<'gcx, 'tcx>>,
502 inh: &'a Inherited<'a, 'gcx, 'tcx>,
505 impl<'a, 'gcx, 'tcx> Deref for FnCtxt<'a, 'gcx, 'tcx> {
506 type Target = Inherited<'a, 'gcx, 'tcx>;
507 fn deref(&self) -> &Self::Target {
512 /// Helper type of a temporary returned by Inherited::build(...).
513 /// Necessary because we can't write the following bound:
514 /// F: for<'b, 'tcx> where 'gcx: 'tcx FnOnce(Inherited<'b, 'gcx, 'tcx>).
515 pub struct InheritedBuilder<'a, 'gcx: 'a+'tcx, 'tcx: 'a> {
516 infcx: infer::InferCtxtBuilder<'a, 'gcx, 'tcx>
519 impl<'a, 'gcx, 'tcx> Inherited<'a, 'gcx, 'tcx> {
520 pub fn build(tcx: TyCtxt<'a, 'gcx, 'gcx>, id: ast::NodeId)
521 -> InheritedBuilder<'a, 'gcx, 'tcx> {
522 let tables = ty::TypeckTables::empty();
523 let param_env = ParameterEnvironment::for_item(tcx, id);
525 infcx: tcx.infer_ctxt((tables, param_env), Reveal::UserFacing)
530 impl<'a, 'gcx, 'tcx> InheritedBuilder<'a, 'gcx, 'tcx> {
531 fn enter<F, R>(&'tcx mut self, f: F) -> R
532 where F: for<'b> FnOnce(Inherited<'b, 'gcx, 'tcx>) -> R
534 self.infcx.enter(|infcx| f(Inherited::new(infcx)))
538 impl<'a, 'gcx, 'tcx> Inherited<'a, 'gcx, 'tcx> {
539 pub fn new(infcx: InferCtxt<'a, 'gcx, 'tcx>) -> Self {
542 fulfillment_cx: RefCell::new(traits::FulfillmentContext::new()),
543 locals: RefCell::new(NodeMap()),
544 deferred_call_resolutions: RefCell::new(DefIdMap()),
545 deferred_cast_checks: RefCell::new(Vec::new()),
546 anon_types: RefCell::new(NodeMap()),
550 fn normalize_associated_types_in<T>(&self,
552 body_id: ast::NodeId,
555 where T : TypeFoldable<'tcx>
557 assoc::normalize_associated_types_in(self,
558 &mut self.fulfillment_cx.borrow_mut(),
566 struct CheckItemTypesVisitor<'a, 'tcx: 'a> { tcx: TyCtxt<'a, 'tcx, 'tcx> }
568 impl<'a, 'tcx> ItemLikeVisitor<'tcx> for CheckItemTypesVisitor<'a, 'tcx> {
569 fn visit_item(&mut self, i: &'tcx hir::Item) {
570 check_item_type(self.tcx, i);
572 fn visit_trait_item(&mut self, _: &'tcx hir::TraitItem) { }
573 fn visit_impl_item(&mut self, _: &'tcx hir::ImplItem) { }
576 pub fn check_wf_new<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>) -> CompileResult {
577 tcx.sess.track_errors(|| {
578 let mut visit = wfcheck::CheckTypeWellFormedVisitor::new(tcx);
579 tcx.visit_all_item_likes_in_krate(DepNode::WfCheck, &mut visit.as_deep_visitor());
583 pub fn check_item_types<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>) -> CompileResult {
584 tcx.sess.track_errors(|| {
585 tcx.visit_all_item_likes_in_krate(DepNode::TypeckItemType,
586 &mut CheckItemTypesVisitor { tcx });
590 pub fn check_item_bodies<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>) -> CompileResult {
591 ty::queries::typeck_item_bodies::get(tcx, DUMMY_SP, LOCAL_CRATE)
594 fn typeck_item_bodies<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, crate_num: CrateNum) -> CompileResult {
595 debug_assert!(crate_num == LOCAL_CRATE);
596 tcx.sess.track_errors(|| {
597 tcx.visit_all_bodies_in_krate(|body_owner_def_id, _body_id| {
598 tcx.item_tables(body_owner_def_id);
603 pub fn provide(providers: &mut Providers) {
604 *providers = Providers {
614 fn closure_type<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
616 -> ty::PolyFnSig<'tcx> {
617 let node_id = tcx.hir.as_local_node_id(def_id).unwrap();
618 tcx.item_tables(def_id).closure_tys[&node_id]
621 fn closure_kind<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
624 let node_id = tcx.hir.as_local_node_id(def_id).unwrap();
625 tcx.item_tables(def_id).closure_kinds[&node_id]
628 fn adt_destructor<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
630 -> Option<ty::Destructor> {
631 tcx.calculate_dtor(def_id, &mut dropck::check_drop_impl)
634 fn typeck_tables<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
636 -> &'tcx ty::TypeckTables<'tcx> {
637 // Closures' tables come from their outermost function,
638 // as they are part of the same "inference environment".
639 let outer_def_id = tcx.closure_base_def_id(def_id);
640 if outer_def_id != def_id {
641 return tcx.item_tables(outer_def_id);
644 let id = tcx.hir.as_local_node_id(def_id).unwrap();
645 let span = tcx.hir.span(id);
646 let unsupported = || {
647 span_bug!(span, "can't type-check body of {:?}", def_id);
650 // Figure out what primary body this item has.
651 let mut fn_decl = None;
652 let body_id = match tcx.hir.get(id) {
653 hir::map::NodeItem(item) => {
655 hir::ItemConst(_, body) |
656 hir::ItemStatic(_, _, body) => body,
657 hir::ItemFn(ref decl, .., body) => {
658 fn_decl = Some(decl);
664 hir::map::NodeTraitItem(item) => {
666 hir::TraitItemKind::Const(_, Some(body)) => body,
667 hir::TraitItemKind::Method(ref sig,
668 hir::TraitMethod::Provided(body)) => {
669 fn_decl = Some(&sig.decl);
675 hir::map::NodeImplItem(item) => {
677 hir::ImplItemKind::Const(_, body) => body,
678 hir::ImplItemKind::Method(ref sig, body) => {
679 fn_decl = Some(&sig.decl);
685 hir::map::NodeExpr(expr) => {
686 // FIXME(eddyb) Closures should have separate
687 // function definition IDs and expression IDs.
688 // Type-checking should not let closures get
689 // this far in a constant position.
690 // Assume that everything other than closures
691 // is a constant "initializer" expression.
693 hir::ExprClosure(..) => {
694 // We should've bailed out above for closures.
695 span_bug!(expr.span, "unexpected closure")
697 _ => hir::BodyId { node_id: expr.id }
702 let body = tcx.hir.body(body_id);
704 Inherited::build(tcx, id).enter(|inh| {
705 let fcx = if let Some(decl) = fn_decl {
706 let fn_sig = tcx.item_type(def_id).fn_sig();
708 check_abi(tcx, span, fn_sig.abi());
710 // Compute the fty from point of view of inside fn.
711 let fn_scope = inh.tcx.region_maps.call_site_extent(id, body_id.node_id);
713 fn_sig.subst(inh.tcx, &inh.parameter_environment.free_substs);
715 inh.tcx.liberate_late_bound_regions(fn_scope, &fn_sig);
717 inh.normalize_associated_types_in(body.value.span, body_id.node_id, &fn_sig);
719 check_fn(&inh, fn_sig, decl, id, body)
721 let fcx = FnCtxt::new(&inh, body.value.id);
722 let expected_type = tcx.item_type(def_id);
723 let expected_type = fcx.normalize_associated_types_in(body.value.span, &expected_type);
724 fcx.require_type_is_sized(expected_type, body.value.span, traits::ConstSized);
726 // Gather locals in statics (because of block expressions).
727 // This is technically unnecessary because locals in static items are forbidden,
728 // but prevents type checking from blowing up before const checking can properly
730 GatherLocalsVisitor { fcx: &fcx }.visit_body(body);
732 fcx.check_expr_coercable_to_type(&body.value, expected_type);
737 fcx.select_all_obligations_and_apply_defaults();
738 fcx.closure_analyze(body);
739 fcx.select_obligations_where_possible();
741 fcx.select_all_obligations_or_error();
743 if fn_decl.is_some() {
744 fcx.regionck_fn(id, body);
746 fcx.regionck_expr(body);
749 fcx.resolve_type_vars_in_body(body)
753 fn check_abi<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, span: Span, abi: Abi) {
754 if !tcx.sess.target.target.is_abi_supported(abi) {
755 struct_span_err!(tcx.sess, span, E0570,
756 "The ABI `{}` is not supported for the current target", abi).emit()
760 struct GatherLocalsVisitor<'a, 'gcx: 'a+'tcx, 'tcx: 'a> {
761 fcx: &'a FnCtxt<'a, 'gcx, 'tcx>
764 impl<'a, 'gcx, 'tcx> GatherLocalsVisitor<'a, 'gcx, 'tcx> {
765 fn assign(&mut self, span: Span, nid: ast::NodeId, ty_opt: Option<Ty<'tcx>>) -> Ty<'tcx> {
768 // infer the variable's type
769 let var_ty = self.fcx.next_ty_var(TypeVariableOrigin::TypeInference(span));
770 self.fcx.locals.borrow_mut().insert(nid, var_ty);
774 // take type that the user specified
775 self.fcx.locals.borrow_mut().insert(nid, typ);
782 impl<'a, 'gcx, 'tcx> Visitor<'gcx> for GatherLocalsVisitor<'a, 'gcx, 'tcx> {
783 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'gcx> {
784 NestedVisitorMap::None
787 // Add explicitly-declared locals.
788 fn visit_local(&mut self, local: &'gcx hir::Local) {
789 let o_ty = match local.ty {
790 Some(ref ty) => Some(self.fcx.to_ty(&ty)),
793 self.assign(local.span, local.id, o_ty);
794 debug!("Local variable {:?} is assigned type {}",
796 self.fcx.ty_to_string(
797 self.fcx.locals.borrow().get(&local.id).unwrap().clone()));
798 intravisit::walk_local(self, local);
801 // Add pattern bindings.
802 fn visit_pat(&mut self, p: &'gcx hir::Pat) {
803 if let PatKind::Binding(_, _, ref path1, _) = p.node {
804 let var_ty = self.assign(p.span, p.id, None);
806 self.fcx.require_type_is_sized(var_ty, p.span,
807 traits::VariableType(p.id));
809 debug!("Pattern binding {} is assigned to {} with type {:?}",
811 self.fcx.ty_to_string(
812 self.fcx.locals.borrow().get(&p.id).unwrap().clone()),
815 intravisit::walk_pat(self, p);
818 // Don't descend into the bodies of nested closures
819 fn visit_fn(&mut self, _: intravisit::FnKind<'gcx>, _: &'gcx hir::FnDecl,
820 _: hir::BodyId, _: Span, _: ast::NodeId) { }
823 /// Helper used for fns and closures. Does the grungy work of checking a function
824 /// body and returns the function context used for that purpose, since in the case of a fn item
825 /// there is still a bit more to do.
828 /// * inherited: other fields inherited from the enclosing fn (if any)
829 fn check_fn<'a, 'gcx, 'tcx>(inherited: &'a Inherited<'a, 'gcx, 'tcx>,
830 fn_sig: ty::FnSig<'tcx>,
831 decl: &'gcx hir::FnDecl,
833 body: &'gcx hir::Body)
834 -> FnCtxt<'a, 'gcx, 'tcx>
836 let mut fn_sig = fn_sig.clone();
838 debug!("check_fn(sig={:?}, fn_id={})", fn_sig, fn_id);
840 // Create the function context. This is either derived from scratch or,
841 // in the case of function expressions, based on the outer context.
842 let mut fcx = FnCtxt::new(inherited, body.value.id);
843 *fcx.ps.borrow_mut() = UnsafetyState::function(fn_sig.unsafety, fn_id);
845 let ret_ty = fn_sig.output();
846 fcx.require_type_is_sized(ret_ty, decl.output.span(), traits::ReturnType);
847 let ret_ty = fcx.instantiate_anon_types(&ret_ty);
848 fcx.ret_coercion = Some(RefCell::new(CoerceMany::new(ret_ty)));
849 fn_sig = fcx.tcx.mk_fn_sig(
850 fn_sig.inputs().iter().cloned(),
857 GatherLocalsVisitor { fcx: &fcx, }.visit_body(body);
859 // Add formal parameters.
860 for (arg_ty, arg) in fn_sig.inputs().iter().zip(&body.arguments) {
861 // The type of the argument must be well-formed.
863 // NB -- this is now checked in wfcheck, but that
864 // currently only results in warnings, so we issue an
865 // old-style WF obligation here so that we still get the
866 // errors that we used to get.
867 fcx.register_old_wf_obligation(arg_ty, arg.pat.span, traits::MiscObligation);
869 // Check the pattern.
870 fcx.check_pat_arg(&arg.pat, arg_ty, true);
871 fcx.write_ty(arg.id, arg_ty);
874 inherited.tables.borrow_mut().liberated_fn_sigs.insert(fn_id, fn_sig);
876 fcx.check_return_expr(&body.value);
878 // Finalize the return check by taking the LUB of the return types
879 // we saw and assigning it to the expected return type. This isn't
880 // really expected to fail, since the coercions would have failed
881 // earlier when trying to find a LUB.
883 // However, the behavior around `!` is sort of complex. In the
884 // event that the `actual_return_ty` comes back as `!`, that
885 // indicates that the fn either does not return or "returns" only
886 // values of type `!`. In this case, if there is an expected
887 // return type that is *not* `!`, that should be ok. But if the
888 // return type is being inferred, we want to "fallback" to `!`:
890 // let x = move || panic!();
892 // To allow for that, I am creating a type variable with diverging
893 // fallback. This was deemed ever so slightly better than unifying
894 // the return value with `!` because it allows for the caller to
895 // make more assumptions about the return type (e.g., they could do
897 // let y: Option<u32> = Some(x());
899 // which would then cause this return type to become `u32`, not
901 let coercion = fcx.ret_coercion.take().unwrap().into_inner();
902 let mut actual_return_ty = coercion.complete(&fcx);
903 if actual_return_ty.is_never() {
904 actual_return_ty = fcx.next_diverging_ty_var(
905 TypeVariableOrigin::DivergingFn(body.value.span));
907 fcx.demand_suptype(body.value.span, ret_ty, actual_return_ty);
912 fn check_struct<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
915 let def_id = tcx.hir.local_def_id(id);
916 let def = tcx.lookup_adt_def(def_id);
917 def.destructor(tcx); // force the destructor to be evaluated
918 check_representable(tcx, span, def_id);
921 check_simd(tcx, span, def_id);
925 fn check_union<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
928 let def_id = tcx.hir.local_def_id(id);
929 let def = tcx.lookup_adt_def(def_id);
930 def.destructor(tcx); // force the destructor to be evaluated
931 check_representable(tcx, span, def_id);
934 pub fn check_item_type<'a,'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, it: &'tcx hir::Item) {
935 debug!("check_item_type(it.id={}, it.name={})",
937 tcx.item_path_str(tcx.hir.local_def_id(it.id)));
938 let _indenter = indenter();
940 // Consts can play a role in type-checking, so they are included here.
941 hir::ItemStatic(..) |
942 hir::ItemConst(..) => {
943 tcx.item_tables(tcx.hir.local_def_id(it.id));
945 hir::ItemEnum(ref enum_definition, _) => {
948 &enum_definition.variants,
951 hir::ItemFn(..) => {} // entirely within check_item_body
952 hir::ItemImpl(.., ref impl_item_refs) => {
953 debug!("ItemImpl {} with id {}", it.name, it.id);
954 let impl_def_id = tcx.hir.local_def_id(it.id);
955 if let Some(impl_trait_ref) = tcx.impl_trait_ref(impl_def_id) {
956 check_impl_items_against_trait(tcx,
961 let trait_def_id = impl_trait_ref.def_id;
962 check_on_unimplemented(tcx, trait_def_id, it);
965 hir::ItemTrait(..) => {
966 let def_id = tcx.hir.local_def_id(it.id);
967 check_on_unimplemented(tcx, def_id, it);
969 hir::ItemStruct(..) => {
970 check_struct(tcx, it.id, it.span);
972 hir::ItemUnion(..) => {
973 check_union(tcx, it.id, it.span);
975 hir::ItemTy(_, ref generics) => {
976 let def_id = tcx.hir.local_def_id(it.id);
977 let pty_ty = tcx.item_type(def_id);
978 check_bounds_are_used(tcx, generics, pty_ty);
980 hir::ItemForeignMod(ref m) => {
981 check_abi(tcx, it.span, m.abi);
983 if m.abi == Abi::RustIntrinsic {
984 for item in &m.items {
985 intrinsic::check_intrinsic_type(tcx, item);
987 } else if m.abi == Abi::PlatformIntrinsic {
988 for item in &m.items {
989 intrinsic::check_platform_intrinsic_type(tcx, item);
992 for item in &m.items {
993 let generics = tcx.item_generics(tcx.hir.local_def_id(item.id));
994 if !generics.types.is_empty() {
995 let mut err = struct_span_err!(tcx.sess, item.span, E0044,
996 "foreign items may not have type parameters");
997 span_help!(&mut err, item.span,
998 "consider using specialization instead of \
1003 if let hir::ForeignItemFn(ref fn_decl, _, _) = item.node {
1004 require_c_abi_if_variadic(tcx, fn_decl, m.abi, item.span);
1009 _ => {/* nothing to do */ }
1013 fn check_on_unimplemented<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
1016 let generics = tcx.item_generics(def_id);
1017 if let Some(ref attr) = item.attrs.iter().find(|a| {
1018 a.check_name("rustc_on_unimplemented")
1020 if let Some(istring) = attr.value_str() {
1021 let istring = istring.as_str();
1022 let parser = Parser::new(&istring);
1023 let types = &generics.types;
1024 for token in parser {
1026 Piece::String(_) => (), // Normal string, no need to check it
1027 Piece::NextArgument(a) => match a.position {
1028 // `{Self}` is allowed
1029 Position::ArgumentNamed(s) if s == "Self" => (),
1030 // So is `{A}` if A is a type parameter
1031 Position::ArgumentNamed(s) => match types.iter().find(|t| {
1036 let name = tcx.item_name(def_id);
1037 span_err!(tcx.sess, attr.span, E0230,
1038 "there is no type parameter \
1043 // `{:1}` and `{}` are not to be used
1044 Position::ArgumentIs(_) => {
1045 span_err!(tcx.sess, attr.span, E0231,
1046 "only named substitution \
1047 parameters are allowed");
1054 tcx.sess, attr.span, E0232,
1055 "this attribute must have a value")
1056 .span_label(attr.span, &format!("attribute requires a value"))
1057 .note(&format!("eg `#[rustc_on_unimplemented = \"foo\"]`"))
1063 fn report_forbidden_specialization<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
1064 impl_item: &hir::ImplItem,
1067 let mut err = struct_span_err!(
1068 tcx.sess, impl_item.span, E0520,
1069 "`{}` specializes an item from a parent `impl`, but \
1070 that item is not marked `default`",
1072 err.span_label(impl_item.span, &format!("cannot specialize default item `{}`",
1075 match tcx.span_of_impl(parent_impl) {
1077 err.span_label(span, &"parent `impl` is here");
1078 err.note(&format!("to specialize, `{}` in the parent `impl` must be marked `default`",
1082 err.note(&format!("parent implementation is in crate `{}`", cname));
1089 fn check_specialization_validity<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
1090 trait_def: &ty::TraitDef,
1092 impl_item: &hir::ImplItem)
1094 let ancestors = trait_def.ancestors(impl_id);
1096 let kind = match impl_item.node {
1097 hir::ImplItemKind::Const(..) => ty::AssociatedKind::Const,
1098 hir::ImplItemKind::Method(..) => ty::AssociatedKind::Method,
1099 hir::ImplItemKind::Type(_) => ty::AssociatedKind::Type
1101 let parent = ancestors.defs(tcx, impl_item.name, kind).skip(1).next()
1102 .map(|node_item| node_item.map(|parent| parent.defaultness));
1104 if let Some(parent) = parent {
1105 if parent.item.is_final() {
1106 report_forbidden_specialization(tcx, impl_item, parent.node.def_id());
1112 fn check_impl_items_against_trait<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
1115 impl_trait_ref: ty::TraitRef<'tcx>,
1116 impl_item_refs: &[hir::ImplItemRef]) {
1117 // If the trait reference itself is erroneous (so the compilation is going
1118 // to fail), skip checking the items here -- the `impl_item` table in `tcx`
1119 // isn't populated for such impls.
1120 if impl_trait_ref.references_error() { return; }
1122 // Locate trait definition and items
1123 let trait_def = tcx.lookup_trait_def(impl_trait_ref.def_id);
1124 let mut overridden_associated_type = None;
1126 let impl_items = || impl_item_refs.iter().map(|iiref| tcx.hir.impl_item(iiref.id));
1128 // Check existing impl methods to see if they are both present in trait
1129 // and compatible with trait signature
1130 for impl_item in impl_items() {
1131 let ty_impl_item = tcx.associated_item(tcx.hir.local_def_id(impl_item.id));
1132 let ty_trait_item = tcx.associated_items(impl_trait_ref.def_id)
1133 .find(|ac| ac.name == ty_impl_item.name);
1135 // Check that impl definition matches trait definition
1136 if let Some(ty_trait_item) = ty_trait_item {
1137 match impl_item.node {
1138 hir::ImplItemKind::Const(..) => {
1139 // Find associated const definition.
1140 if ty_trait_item.kind == ty::AssociatedKind::Const {
1141 compare_const_impl(tcx,
1147 let mut err = struct_span_err!(tcx.sess, impl_item.span, E0323,
1148 "item `{}` is an associated const, \
1149 which doesn't match its trait `{}`",
1152 err.span_label(impl_item.span, &format!("does not match trait"));
1153 // We can only get the spans from local trait definition
1154 // Same for E0324 and E0325
1155 if let Some(trait_span) = tcx.hir.span_if_local(ty_trait_item.def_id) {
1156 err.span_label(trait_span, &format!("item in trait"));
1161 hir::ImplItemKind::Method(_, body_id) => {
1162 let trait_span = tcx.hir.span_if_local(ty_trait_item.def_id);
1163 if ty_trait_item.kind == ty::AssociatedKind::Method {
1164 let err_count = tcx.sess.err_count();
1165 compare_impl_method(tcx,
1172 true); // start with old-broken-mode
1173 if err_count == tcx.sess.err_count() {
1174 // old broken mode did not report an error. Try with the new mode.
1175 compare_impl_method(tcx,
1182 false); // use the new mode
1185 let mut err = struct_span_err!(tcx.sess, impl_item.span, E0324,
1186 "item `{}` is an associated method, \
1187 which doesn't match its trait `{}`",
1190 err.span_label(impl_item.span, &format!("does not match trait"));
1191 if let Some(trait_span) = tcx.hir.span_if_local(ty_trait_item.def_id) {
1192 err.span_label(trait_span, &format!("item in trait"));
1197 hir::ImplItemKind::Type(_) => {
1198 if ty_trait_item.kind == ty::AssociatedKind::Type {
1199 if ty_trait_item.defaultness.has_value() {
1200 overridden_associated_type = Some(impl_item);
1203 let mut err = struct_span_err!(tcx.sess, impl_item.span, E0325,
1204 "item `{}` is an associated type, \
1205 which doesn't match its trait `{}`",
1208 err.span_label(impl_item.span, &format!("does not match trait"));
1209 if let Some(trait_span) = tcx.hir.span_if_local(ty_trait_item.def_id) {
1210 err.span_label(trait_span, &format!("item in trait"));
1218 check_specialization_validity(tcx, trait_def, impl_id, impl_item);
1221 // Check for missing items from trait
1222 let mut missing_items = Vec::new();
1223 let mut invalidated_items = Vec::new();
1224 let associated_type_overridden = overridden_associated_type.is_some();
1225 for trait_item in tcx.associated_items(impl_trait_ref.def_id) {
1226 let is_implemented = trait_def.ancestors(impl_id)
1227 .defs(tcx, trait_item.name, trait_item.kind)
1229 .map(|node_item| !node_item.node.is_from_trait())
1232 if !is_implemented {
1233 if !trait_item.defaultness.has_value() {
1234 missing_items.push(trait_item);
1235 } else if associated_type_overridden {
1236 invalidated_items.push(trait_item.name);
1241 let signature = |item: &ty::AssociatedItem| {
1243 ty::AssociatedKind::Method => {
1244 format!("{}", tcx.item_type(item.def_id).fn_sig().0)
1246 ty::AssociatedKind::Type => format!("type {};", item.name.to_string()),
1247 ty::AssociatedKind::Const => {
1248 format!("const {}: {:?};", item.name.to_string(), tcx.item_type(item.def_id))
1253 if !missing_items.is_empty() {
1254 let mut err = struct_span_err!(tcx.sess, impl_span, E0046,
1255 "not all trait items implemented, missing: `{}`",
1256 missing_items.iter()
1257 .map(|trait_item| trait_item.name.to_string())
1258 .collect::<Vec<_>>().join("`, `"));
1259 err.span_label(impl_span, &format!("missing `{}` in implementation",
1260 missing_items.iter()
1261 .map(|trait_item| trait_item.name.to_string())
1262 .collect::<Vec<_>>().join("`, `")));
1263 for trait_item in missing_items {
1264 if let Some(span) = tcx.hir.span_if_local(trait_item.def_id) {
1265 err.span_label(span, &format!("`{}` from trait", trait_item.name));
1267 err.note(&format!("`{}` from trait: `{}`",
1269 signature(&trait_item)));
1275 if !invalidated_items.is_empty() {
1276 let invalidator = overridden_associated_type.unwrap();
1277 span_err!(tcx.sess, invalidator.span, E0399,
1278 "the following trait items need to be reimplemented \
1279 as `{}` was overridden: `{}`",
1281 invalidated_items.iter()
1282 .map(|name| name.to_string())
1283 .collect::<Vec<_>>().join("`, `"))
1287 /// Checks whether a type can be represented in memory. In particular, it
1288 /// identifies types that contain themselves without indirection through a
1289 /// pointer, which would mean their size is unbounded.
1290 fn check_representable<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
1294 let rty = tcx.item_type(item_def_id);
1296 // Check that it is possible to represent this type. This call identifies
1297 // (1) types that contain themselves and (2) types that contain a different
1298 // recursive type. It is only necessary to throw an error on those that
1299 // contain themselves. For case 2, there must be an inner type that will be
1300 // caught by case 1.
1301 match rty.is_representable(tcx, sp) {
1302 Representability::SelfRecursive => {
1303 tcx.recursive_type_with_infinite_size_error(item_def_id).emit();
1306 Representability::Representable | Representability::ContainsRecursive => (),
1311 pub fn check_simd<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, sp: Span, def_id: DefId) {
1312 let t = tcx.item_type(def_id);
1314 ty::TyAdt(def, substs) if def.is_struct() => {
1315 let fields = &def.struct_variant().fields;
1316 if fields.is_empty() {
1317 span_err!(tcx.sess, sp, E0075, "SIMD vector cannot be empty");
1320 let e = fields[0].ty(tcx, substs);
1321 if !fields.iter().all(|f| f.ty(tcx, substs) == e) {
1322 struct_span_err!(tcx.sess, sp, E0076, "SIMD vector should be homogeneous")
1323 .span_label(sp, &format!("SIMD elements must have the same type"))
1328 ty::TyParam(_) => { /* struct<T>(T, T, T, T) is ok */ }
1329 _ if e.is_machine() => { /* struct(u8, u8, u8, u8) is ok */ }
1331 span_err!(tcx.sess, sp, E0077,
1332 "SIMD vector element type should be machine type");
1341 #[allow(trivial_numeric_casts)]
1342 pub fn check_enum<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
1344 vs: &'tcx [hir::Variant],
1346 let def_id = tcx.hir.local_def_id(id);
1347 let def = tcx.lookup_adt_def(def_id);
1348 def.destructor(tcx); // force the destructor to be evaluated
1350 if vs.is_empty() && tcx.has_attr(def_id, "repr") {
1352 tcx.sess, sp, E0084,
1353 "unsupported representation for zero-variant enum")
1354 .span_label(sp, &format!("unsupported enum representation"))
1358 let repr_type_ty = def.repr.discr_type().to_ty(tcx);
1359 if repr_type_ty == tcx.types.i128 || repr_type_ty == tcx.types.u128 {
1360 if !tcx.sess.features.borrow().i128_type {
1361 emit_feature_err(&tcx.sess.parse_sess,
1362 "i128_type", sp, GateIssue::Language, "128-bit type is unstable");
1367 if let Some(e) = v.node.disr_expr {
1368 tcx.item_tables(tcx.hir.local_def_id(e.node_id));
1372 let mut disr_vals: Vec<ConstInt> = Vec::new();
1373 for (discr, v) in def.discriminants(tcx).zip(vs) {
1374 // Check for duplicate discriminant values
1375 if let Some(i) = disr_vals.iter().position(|&x| x == discr) {
1376 let variant_i_node_id = tcx.hir.as_local_node_id(def.variants[i].did).unwrap();
1377 let variant_i = tcx.hir.expect_variant(variant_i_node_id);
1378 let i_span = match variant_i.node.disr_expr {
1379 Some(expr) => tcx.hir.span(expr.node_id),
1380 None => tcx.hir.span(variant_i_node_id)
1382 let span = match v.node.disr_expr {
1383 Some(expr) => tcx.hir.span(expr.node_id),
1386 struct_span_err!(tcx.sess, span, E0081,
1387 "discriminant value `{}` already exists", disr_vals[i])
1388 .span_label(i_span, &format!("first use of `{}`", disr_vals[i]))
1389 .span_label(span , &format!("enum already has `{}`", disr_vals[i]))
1392 disr_vals.push(discr);
1395 check_representable(tcx, sp, def_id);
1398 impl<'a, 'gcx, 'tcx> AstConv<'gcx, 'tcx> for FnCtxt<'a, 'gcx, 'tcx> {
1399 fn tcx<'b>(&'b self) -> TyCtxt<'b, 'gcx, 'tcx> { self.tcx }
1401 fn ast_ty_to_ty_cache(&self) -> &RefCell<NodeMap<Ty<'tcx>>> {
1402 &self.ast_ty_to_ty_cache
1405 fn get_free_substs(&self) -> Option<&Substs<'tcx>> {
1406 Some(&self.parameter_environment.free_substs)
1409 fn get_type_parameter_bounds(&self, _: Span, def_id: DefId)
1410 -> ty::GenericPredicates<'tcx>
1413 let node_id = tcx.hir.as_local_node_id(def_id).unwrap();
1414 let item_id = tcx.hir.ty_param_owner(node_id);
1415 let item_def_id = tcx.hir.local_def_id(item_id);
1416 let generics = tcx.item_generics(item_def_id);
1417 let index = generics.type_param_to_index[&def_id.index];
1418 ty::GenericPredicates {
1420 predicates: self.parameter_environment.caller_bounds.iter().filter(|predicate| {
1422 ty::Predicate::Trait(ref data) => {
1423 data.0.self_ty().is_param(index)
1427 }).cloned().collect()
1431 fn re_infer(&self, span: Span, def: Option<&ty::RegionParameterDef>)
1432 -> Option<&'tcx ty::Region> {
1434 Some(def) => infer::EarlyBoundRegion(span, def.name, def.issue_32330),
1435 None => infer::MiscVariable(span)
1437 Some(self.next_region_var(v))
1440 fn ty_infer(&self, span: Span) -> Ty<'tcx> {
1441 self.next_ty_var(TypeVariableOrigin::TypeInference(span))
1444 fn ty_infer_for_def(&self,
1445 ty_param_def: &ty::TypeParameterDef,
1446 substs: &[Kind<'tcx>],
1447 span: Span) -> Ty<'tcx> {
1448 self.type_var_for_def(span, ty_param_def, substs)
1451 fn projected_ty_from_poly_trait_ref(&self,
1453 poly_trait_ref: ty::PolyTraitRef<'tcx>,
1454 item_name: ast::Name)
1457 let (trait_ref, _) =
1458 self.replace_late_bound_regions_with_fresh_var(
1460 infer::LateBoundRegionConversionTime::AssocTypeProjection(item_name),
1463 self.tcx().mk_projection(trait_ref, item_name)
1466 fn normalize_ty(&self, span: Span, ty: Ty<'tcx>) -> Ty<'tcx> {
1467 if ty.has_escaping_regions() {
1468 ty // FIXME: normalization and escaping regions
1470 self.normalize_associated_types_in(span, &ty)
1474 fn set_tainted_by_errors(&self) {
1475 self.infcx.set_tainted_by_errors()
1479 /// Controls whether the arguments are tupled. This is used for the call
1482 /// Tupling means that all call-side arguments are packed into a tuple and
1483 /// passed as a single parameter. For example, if tupling is enabled, this
1486 /// fn f(x: (isize, isize))
1488 /// Can be called as:
1495 #[derive(Clone, Eq, PartialEq)]
1496 enum TupleArgumentsFlag {
1501 impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
1502 pub fn new(inh: &'a Inherited<'a, 'gcx, 'tcx>,
1503 body_id: ast::NodeId)
1504 -> FnCtxt<'a, 'gcx, 'tcx> {
1506 ast_ty_to_ty_cache: RefCell::new(NodeMap()),
1508 err_count_on_creation: inh.tcx.sess.err_count(),
1510 ps: RefCell::new(UnsafetyState::function(hir::Unsafety::Normal,
1511 ast::CRATE_NODE_ID)),
1512 diverges: Cell::new(Diverges::Maybe),
1513 has_errors: Cell::new(false),
1514 enclosing_breakables: RefCell::new(EnclosingBreakables {
1522 pub fn sess(&self) -> &Session {
1526 pub fn err_count_since_creation(&self) -> usize {
1527 self.tcx.sess.err_count() - self.err_count_on_creation
1530 /// Produce warning on the given node, if the current point in the
1531 /// function is unreachable, and there hasn't been another warning.
1532 fn warn_if_unreachable(&self, id: ast::NodeId, span: Span, kind: &str) {
1533 if self.diverges.get() == Diverges::Always {
1534 self.diverges.set(Diverges::WarnedAlways);
1536 debug!("warn_if_unreachable: id={:?} span={:?} kind={}", id, span, kind);
1538 self.tables.borrow_mut().lints.add_lint(
1539 lint::builtin::UNREACHABLE_CODE,
1541 format!("unreachable {}", kind));
1547 code: ObligationCauseCode<'tcx>)
1548 -> ObligationCause<'tcx> {
1549 ObligationCause::new(span, self.body_id, code)
1552 pub fn misc(&self, span: Span) -> ObligationCause<'tcx> {
1553 self.cause(span, ObligationCauseCode::MiscObligation)
1556 /// Resolves type variables in `ty` if possible. Unlike the infcx
1557 /// version (resolve_type_vars_if_possible), this version will
1558 /// also select obligations if it seems useful, in an effort
1559 /// to get more type information.
1560 fn resolve_type_vars_with_obligations(&self, mut ty: Ty<'tcx>) -> Ty<'tcx> {
1561 debug!("resolve_type_vars_with_obligations(ty={:?})", ty);
1563 // No TyInfer()? Nothing needs doing.
1564 if !ty.has_infer_types() {
1565 debug!("resolve_type_vars_with_obligations: ty={:?}", ty);
1569 // If `ty` is a type variable, see whether we already know what it is.
1570 ty = self.resolve_type_vars_if_possible(&ty);
1571 if !ty.has_infer_types() {
1572 debug!("resolve_type_vars_with_obligations: ty={:?}", ty);
1576 // If not, try resolving pending obligations as much as
1577 // possible. This can help substantially when there are
1578 // indirect dependencies that don't seem worth tracking
1580 self.select_obligations_where_possible();
1581 ty = self.resolve_type_vars_if_possible(&ty);
1583 debug!("resolve_type_vars_with_obligations: ty={:?}", ty);
1587 fn record_deferred_call_resolution(&self,
1588 closure_def_id: DefId,
1589 r: DeferredCallResolutionHandler<'gcx, 'tcx>) {
1590 let mut deferred_call_resolutions = self.deferred_call_resolutions.borrow_mut();
1591 deferred_call_resolutions.entry(closure_def_id).or_insert(vec![]).push(r);
1594 fn remove_deferred_call_resolutions(&self,
1595 closure_def_id: DefId)
1596 -> Vec<DeferredCallResolutionHandler<'gcx, 'tcx>>
1598 let mut deferred_call_resolutions = self.deferred_call_resolutions.borrow_mut();
1599 deferred_call_resolutions.remove(&closure_def_id).unwrap_or(Vec::new())
1602 pub fn tag(&self) -> String {
1603 let self_ptr: *const FnCtxt = self;
1604 format!("{:?}", self_ptr)
1607 pub fn local_ty(&self, span: Span, nid: ast::NodeId) -> Ty<'tcx> {
1608 match self.locals.borrow().get(&nid) {
1611 span_bug!(span, "no type for local variable {}",
1612 self.tcx.hir.node_to_string(nid));
1618 pub fn write_ty(&self, node_id: ast::NodeId, ty: Ty<'tcx>) {
1619 debug!("write_ty({}, {:?}) in fcx {}",
1620 node_id, self.resolve_type_vars_if_possible(&ty), self.tag());
1621 self.tables.borrow_mut().node_types.insert(node_id, ty);
1623 if ty.references_error() {
1624 self.has_errors.set(true);
1625 self.set_tainted_by_errors();
1629 pub fn write_substs(&self, node_id: ast::NodeId, substs: ty::ItemSubsts<'tcx>) {
1630 if !substs.substs.is_noop() {
1631 debug!("write_substs({}, {:?}) in fcx {}",
1636 self.tables.borrow_mut().item_substs.insert(node_id, substs);
1640 pub fn write_autoderef_adjustment(&self,
1641 node_id: ast::NodeId,
1643 adjusted_ty: Ty<'tcx>) {
1644 self.write_adjustment(node_id, adjustment::Adjustment {
1645 kind: adjustment::Adjust::DerefRef {
1654 pub fn write_adjustment(&self,
1655 node_id: ast::NodeId,
1656 adj: adjustment::Adjustment<'tcx>) {
1657 debug!("write_adjustment(node_id={}, adj={:?})", node_id, adj);
1659 if adj.is_identity() {
1663 self.tables.borrow_mut().adjustments.insert(node_id, adj);
1666 /// Basically whenever we are converting from a type scheme into
1667 /// the fn body space, we always want to normalize associated
1668 /// types as well. This function combines the two.
1669 fn instantiate_type_scheme<T>(&self,
1671 substs: &Substs<'tcx>,
1674 where T : TypeFoldable<'tcx>
1676 let value = value.subst(self.tcx, substs);
1677 let result = self.normalize_associated_types_in(span, &value);
1678 debug!("instantiate_type_scheme(value={:?}, substs={:?}) = {:?}",
1685 /// As `instantiate_type_scheme`, but for the bounds found in a
1686 /// generic type scheme.
1687 fn instantiate_bounds(&self, span: Span, def_id: DefId, substs: &Substs<'tcx>)
1688 -> ty::InstantiatedPredicates<'tcx> {
1689 let bounds = self.tcx.item_predicates(def_id);
1690 let result = bounds.instantiate(self.tcx, substs);
1691 let result = self.normalize_associated_types_in(span, &result.predicates);
1692 debug!("instantiate_bounds(bounds={:?}, substs={:?}) = {:?}",
1696 ty::InstantiatedPredicates {
1701 /// Replace all anonymized types with fresh inference variables
1702 /// and record them for writeback.
1703 fn instantiate_anon_types<T: TypeFoldable<'tcx>>(&self, value: &T) -> T {
1704 value.fold_with(&mut BottomUpFolder { tcx: self.tcx, fldop: |ty| {
1705 if let ty::TyAnon(def_id, substs) = ty.sty {
1706 // Use the same type variable if the exact same TyAnon appears more
1707 // than once in the return type (e.g. if it's pased to a type alias).
1708 let id = self.tcx.hir.as_local_node_id(def_id).unwrap();
1709 if let Some(ty_var) = self.anon_types.borrow().get(&id) {
1712 let span = self.tcx.def_span(def_id);
1713 let ty_var = self.next_ty_var(TypeVariableOrigin::TypeInference(span));
1714 self.anon_types.borrow_mut().insert(id, ty_var);
1716 let item_predicates = self.tcx.item_predicates(def_id);
1717 let bounds = item_predicates.instantiate(self.tcx, substs);
1719 for predicate in bounds.predicates {
1720 // Change the predicate to refer to the type variable,
1721 // which will be the concrete type, instead of the TyAnon.
1722 // This also instantiates nested `impl Trait`.
1723 let predicate = self.instantiate_anon_types(&predicate);
1725 // Require that the predicate holds for the concrete type.
1726 let cause = traits::ObligationCause::new(span, self.body_id,
1727 traits::ReturnType);
1728 self.register_predicate(traits::Obligation::new(cause, predicate));
1738 fn normalize_associated_types_in<T>(&self, span: Span, value: &T) -> T
1739 where T : TypeFoldable<'tcx>
1741 self.inh.normalize_associated_types_in(span, self.body_id, value)
1744 pub fn write_nil(&self, node_id: ast::NodeId) {
1745 self.write_ty(node_id, self.tcx.mk_nil());
1748 pub fn write_error(&self, node_id: ast::NodeId) {
1749 self.write_ty(node_id, self.tcx.types.err);
1752 pub fn require_type_meets(&self,
1755 code: traits::ObligationCauseCode<'tcx>,
1758 self.register_bound(
1761 traits::ObligationCause::new(span, self.body_id, code));
1764 pub fn require_type_is_sized(&self,
1767 code: traits::ObligationCauseCode<'tcx>)
1769 let lang_item = self.tcx.require_lang_item(lang_items::SizedTraitLangItem);
1770 self.require_type_meets(ty, span, code, lang_item);
1773 pub fn register_bound(&self,
1776 cause: traits::ObligationCause<'tcx>)
1778 self.fulfillment_cx.borrow_mut()
1779 .register_bound(self, ty, def_id, cause);
1782 pub fn register_predicate(&self,
1783 obligation: traits::PredicateObligation<'tcx>)
1785 debug!("register_predicate({:?})", obligation);
1786 if obligation.has_escaping_regions() {
1787 span_bug!(obligation.cause.span, "escaping regions in predicate {:?}",
1792 .register_predicate_obligation(self, obligation);
1795 pub fn register_predicates(&self,
1796 obligations: Vec<traits::PredicateObligation<'tcx>>)
1798 for obligation in obligations {
1799 self.register_predicate(obligation);
1803 pub fn register_infer_ok_obligations<T>(&self, infer_ok: InferOk<'tcx, T>) -> T {
1804 self.register_predicates(infer_ok.obligations);
1808 pub fn to_ty(&self, ast_t: &hir::Ty) -> Ty<'tcx> {
1809 let t = AstConv::ast_ty_to_ty(self, ast_t);
1810 self.register_wf_obligation(t, ast_t.span, traits::MiscObligation);
1814 pub fn node_ty(&self, id: ast::NodeId) -> Ty<'tcx> {
1815 match self.tables.borrow().node_types.get(&id) {
1817 None if self.err_count_since_creation() != 0 => self.tcx.types.err,
1819 bug!("no type for node {}: {} in fcx {}",
1820 id, self.tcx.hir.node_to_string(id),
1826 pub fn opt_node_ty_substs<F>(&self,
1829 F: FnOnce(&ty::ItemSubsts<'tcx>),
1831 if let Some(s) = self.tables.borrow().item_substs.get(&id) {
1836 /// Registers an obligation for checking later, during regionck, that the type `ty` must
1837 /// outlive the region `r`.
1838 pub fn register_region_obligation(&self,
1840 region: &'tcx ty::Region,
1841 cause: traits::ObligationCause<'tcx>)
1843 let mut fulfillment_cx = self.fulfillment_cx.borrow_mut();
1844 fulfillment_cx.register_region_obligation(ty, region, cause);
1847 /// Registers an obligation for checking later, during regionck, that the type `ty` must
1848 /// outlive the region `r`.
1849 pub fn register_wf_obligation(&self,
1852 code: traits::ObligationCauseCode<'tcx>)
1854 // WF obligations never themselves fail, so no real need to give a detailed cause:
1855 let cause = traits::ObligationCause::new(span, self.body_id, code);
1856 self.register_predicate(traits::Obligation::new(cause, ty::Predicate::WellFormed(ty)));
1859 pub fn register_old_wf_obligation(&self,
1862 code: traits::ObligationCauseCode<'tcx>)
1864 // Registers an "old-style" WF obligation that uses the
1865 // implicator code. This is basically a buggy version of
1866 // `register_wf_obligation` that is being kept around
1867 // temporarily just to help with phasing in the newer rules.
1869 // FIXME(#27579) all uses of this should be migrated to register_wf_obligation eventually
1870 let cause = traits::ObligationCause::new(span, self.body_id, code);
1871 self.register_region_obligation(ty, self.tcx.mk_region(ty::ReEmpty), cause);
1874 /// Registers obligations that all types appearing in `substs` are well-formed.
1875 pub fn add_wf_bounds(&self, substs: &Substs<'tcx>, expr: &hir::Expr)
1877 for ty in substs.types() {
1878 self.register_wf_obligation(ty, expr.span, traits::MiscObligation);
1882 /// Given a fully substituted set of bounds (`generic_bounds`), and the values with which each
1883 /// type/region parameter was instantiated (`substs`), creates and registers suitable
1884 /// trait/region obligations.
1886 /// For example, if there is a function:
1889 /// fn foo<'a,T:'a>(...)
1892 /// and a reference:
1898 /// Then we will create a fresh region variable `'$0` and a fresh type variable `$1` for `'a`
1899 /// and `T`. This routine will add a region obligation `$1:'$0` and register it locally.
1900 pub fn add_obligations_for_parameters(&self,
1901 cause: traits::ObligationCause<'tcx>,
1902 predicates: &ty::InstantiatedPredicates<'tcx>)
1904 assert!(!predicates.has_escaping_regions());
1906 debug!("add_obligations_for_parameters(predicates={:?})",
1909 for obligation in traits::predicates_for_generics(cause, predicates) {
1910 self.register_predicate(obligation);
1914 // FIXME(arielb1): use this instead of field.ty everywhere
1915 // Only for fields! Returns <none> for methods>
1916 // Indifferent to privacy flags
1917 pub fn field_ty(&self,
1919 field: &'tcx ty::FieldDef,
1920 substs: &Substs<'tcx>)
1923 self.normalize_associated_types_in(span,
1924 &field.ty(self.tcx, substs))
1927 fn check_casts(&self) {
1928 let mut deferred_cast_checks = self.deferred_cast_checks.borrow_mut();
1929 for cast in deferred_cast_checks.drain(..) {
1934 /// Apply "fallbacks" to some types
1935 /// unconstrained types get replaced with ! or () (depending on whether
1936 /// feature(never_type) is enabled), unconstrained ints with i32, and
1937 /// unconstrained floats with f64.
1938 fn default_type_parameters(&self) {
1939 use rustc::ty::error::UnconstrainedNumeric::Neither;
1940 use rustc::ty::error::UnconstrainedNumeric::{UnconstrainedInt, UnconstrainedFloat};
1942 // Defaulting inference variables becomes very dubious if we have
1943 // encountered type-checking errors. Therefore, if we think we saw
1944 // some errors in this function, just resolve all uninstanted type
1945 // varibles to TyError.
1946 if self.is_tainted_by_errors() {
1947 for ty in &self.unsolved_variables() {
1948 if let ty::TyInfer(_) = self.shallow_resolve(ty).sty {
1949 debug!("default_type_parameters: defaulting `{:?}` to error", ty);
1950 self.demand_eqtype(syntax_pos::DUMMY_SP, *ty, self.tcx().types.err);
1956 for ty in &self.unsolved_variables() {
1957 let resolved = self.resolve_type_vars_if_possible(ty);
1958 if self.type_var_diverges(resolved) {
1959 debug!("default_type_parameters: defaulting `{:?}` to `!` because it diverges",
1961 self.demand_eqtype(syntax_pos::DUMMY_SP, *ty,
1962 self.tcx.mk_diverging_default());
1964 match self.type_is_unconstrained_numeric(resolved) {
1965 UnconstrainedInt => {
1966 debug!("default_type_parameters: defaulting `{:?}` to `i32`",
1968 self.demand_eqtype(syntax_pos::DUMMY_SP, *ty, self.tcx.types.i32)
1970 UnconstrainedFloat => {
1971 debug!("default_type_parameters: defaulting `{:?}` to `f32`",
1973 self.demand_eqtype(syntax_pos::DUMMY_SP, *ty, self.tcx.types.f64)
1981 // Implements type inference fallback algorithm
1982 fn select_all_obligations_and_apply_defaults(&self) {
1983 self.select_obligations_where_possible();
1984 self.default_type_parameters();
1985 self.select_obligations_where_possible();
1988 fn select_all_obligations_or_error(&self) {
1989 debug!("select_all_obligations_or_error");
1991 // upvar inference should have ensured that all deferred call
1992 // resolutions are handled by now.
1993 assert!(self.deferred_call_resolutions.borrow().is_empty());
1995 self.select_all_obligations_and_apply_defaults();
1997 let mut fulfillment_cx = self.fulfillment_cx.borrow_mut();
1999 match fulfillment_cx.select_all_or_error(self) {
2001 Err(errors) => { self.report_fulfillment_errors(&errors); }
2005 /// Select as many obligations as we can at present.
2006 fn select_obligations_where_possible(&self) {
2007 match self.fulfillment_cx.borrow_mut().select_where_possible(self) {
2009 Err(errors) => { self.report_fulfillment_errors(&errors); }
2013 /// For the overloaded lvalue expressions (`*x`, `x[3]`), the trait
2014 /// returns a type of `&T`, but the actual type we assign to the
2015 /// *expression* is `T`. So this function just peels off the return
2016 /// type by one layer to yield `T`.
2017 fn make_overloaded_lvalue_return_type(&self,
2018 method: MethodCallee<'tcx>)
2019 -> ty::TypeAndMut<'tcx>
2021 // extract method return type, which will be &T;
2022 // all LB regions should have been instantiated during method lookup
2023 let ret_ty = method.ty.fn_ret();
2024 let ret_ty = self.tcx.no_late_bound_regions(&ret_ty).unwrap();
2026 // method returns &T, but the type as visible to user is T, so deref
2027 ret_ty.builtin_deref(true, NoPreference).unwrap()
2030 fn lookup_indexing(&self,
2032 base_expr: &'gcx hir::Expr,
2035 lvalue_pref: LvaluePreference)
2036 -> Option<(/*index type*/ Ty<'tcx>, /*element type*/ Ty<'tcx>)>
2038 // FIXME(#18741) -- this is almost but not quite the same as the
2039 // autoderef that normal method probing does. They could likely be
2042 let mut autoderef = self.autoderef(base_expr.span, base_ty);
2044 while let Some((adj_ty, autoderefs)) = autoderef.next() {
2045 if let Some(final_mt) = self.try_index_step(
2046 MethodCall::expr(expr.id),
2047 expr, base_expr, adj_ty, autoderefs,
2048 false, lvalue_pref, idx_ty)
2050 autoderef.finalize(lvalue_pref, &[base_expr]);
2051 return Some(final_mt);
2054 if let ty::TyArray(element_ty, _) = adj_ty.sty {
2055 autoderef.finalize(lvalue_pref, &[base_expr]);
2056 let adjusted_ty = self.tcx.mk_slice(element_ty);
2057 return self.try_index_step(
2058 MethodCall::expr(expr.id), expr, base_expr,
2059 adjusted_ty, autoderefs, true, lvalue_pref, idx_ty);
2062 autoderef.unambiguous_final_ty();
2066 /// To type-check `base_expr[index_expr]`, we progressively autoderef
2067 /// (and otherwise adjust) `base_expr`, looking for a type which either
2068 /// supports builtin indexing or overloaded indexing.
2069 /// This loop implements one step in that search; the autoderef loop
2070 /// is implemented by `lookup_indexing`.
2071 fn try_index_step(&self,
2072 method_call: MethodCall,
2074 base_expr: &'gcx hir::Expr,
2075 adjusted_ty: Ty<'tcx>,
2078 lvalue_pref: LvaluePreference,
2080 -> Option<(/*index type*/ Ty<'tcx>, /*element type*/ Ty<'tcx>)>
2083 debug!("try_index_step(expr={:?}, base_expr.id={:?}, adjusted_ty={:?}, \
2084 autoderefs={}, unsize={}, index_ty={:?})",
2092 let input_ty = self.next_ty_var(TypeVariableOrigin::AutoDeref(base_expr.span));
2094 // First, try built-in indexing.
2095 match (adjusted_ty.builtin_index(), &index_ty.sty) {
2096 (Some(ty), &ty::TyUint(ast::UintTy::Us)) | (Some(ty), &ty::TyInfer(ty::IntVar(_))) => {
2097 debug!("try_index_step: success, using built-in indexing");
2098 // If we had `[T; N]`, we should've caught it before unsizing to `[T]`.
2100 self.write_autoderef_adjustment(base_expr.id, autoderefs, adjusted_ty);
2101 return Some((tcx.types.usize, ty));
2106 // Try `IndexMut` first, if preferred.
2107 let method = match (lvalue_pref, tcx.lang_items.index_mut_trait()) {
2108 (PreferMutLvalue, Some(trait_did)) => {
2109 self.lookup_method_in_trait_adjusted(expr.span,
2111 Symbol::intern("index_mut"),
2116 Some(vec![input_ty]))
2121 // Otherwise, fall back to `Index`.
2122 let method = match (method, tcx.lang_items.index_trait()) {
2123 (None, Some(trait_did)) => {
2124 self.lookup_method_in_trait_adjusted(expr.span,
2126 Symbol::intern("index"),
2131 Some(vec![input_ty]))
2133 (method, _) => method,
2136 // If some lookup succeeds, write callee into table and extract index/element
2137 // type from the method signature.
2138 // If some lookup succeeded, install method in table
2139 method.map(|method| {
2140 debug!("try_index_step: success, using overloaded indexing");
2141 self.tables.borrow_mut().method_map.insert(method_call, method);
2142 (input_ty, self.make_overloaded_lvalue_return_type(method).ty)
2146 fn check_method_argument_types(&self,
2148 method_fn_ty: Ty<'tcx>,
2149 callee_expr: &'gcx hir::Expr,
2150 args_no_rcvr: &'gcx [hir::Expr],
2151 tuple_arguments: TupleArgumentsFlag,
2152 expected: Expectation<'tcx>)
2154 if method_fn_ty.references_error() {
2155 let err_inputs = self.err_args(args_no_rcvr.len());
2157 let err_inputs = match tuple_arguments {
2158 DontTupleArguments => err_inputs,
2159 TupleArguments => vec![self.tcx.intern_tup(&err_inputs[..], false)],
2162 self.check_argument_types(sp, &err_inputs[..], &[], args_no_rcvr,
2163 false, tuple_arguments, None);
2166 match method_fn_ty.sty {
2167 ty::TyFnDef(def_id, .., ref fty) => {
2168 // HACK(eddyb) ignore self in the definition (see above).
2169 let expected_arg_tys = self.expected_inputs_for_expected_output(
2173 &fty.0.inputs()[1..]
2175 self.check_argument_types(sp, &fty.0.inputs()[1..], &expected_arg_tys[..],
2176 args_no_rcvr, fty.0.variadic, tuple_arguments,
2177 self.tcx.hir.span_if_local(def_id));
2181 span_bug!(callee_expr.span, "method without bare fn type");
2187 /// Generic function that factors out common logic from function calls,
2188 /// method calls and overloaded operators.
2189 fn check_argument_types(&self,
2191 fn_inputs: &[Ty<'tcx>],
2192 expected_arg_tys: &[Ty<'tcx>],
2193 args: &'gcx [hir::Expr],
2195 tuple_arguments: TupleArgumentsFlag,
2196 def_span: Option<Span>) {
2199 // Grab the argument types, supplying fresh type variables
2200 // if the wrong number of arguments were supplied
2201 let supplied_arg_count = if tuple_arguments == DontTupleArguments {
2207 // All the input types from the fn signature must outlive the call
2208 // so as to validate implied bounds.
2209 for &fn_input_ty in fn_inputs {
2210 self.register_wf_obligation(fn_input_ty, sp, traits::MiscObligation);
2213 let mut expected_arg_tys = expected_arg_tys;
2214 let expected_arg_count = fn_inputs.len();
2216 let sp_args = if args.len() > 0 {
2217 let (first, args) = args.split_at(1);
2218 let mut sp_tmp = first[0].span;
2220 let sp_opt = self.sess().codemap().merge_spans(sp_tmp, arg.span);
2221 if ! sp_opt.is_some() {
2224 sp_tmp = sp_opt.unwrap();
2231 fn parameter_count_error<'tcx>(sess: &Session, sp: Span, expected_count: usize,
2232 arg_count: usize, error_code: &str, variadic: bool,
2233 def_span: Option<Span>) {
2234 let mut err = sess.struct_span_err_with_code(sp,
2235 &format!("this function takes {}{} parameter{} but {} parameter{} supplied",
2236 if variadic {"at least "} else {""},
2238 if expected_count == 1 {""} else {"s"},
2240 if arg_count == 1 {" was"} else {"s were"}),
2243 err.span_label(sp, &format!("expected {}{} parameter{}",
2244 if variadic {"at least "} else {""},
2246 if expected_count == 1 {""} else {"s"}));
2247 if let Some(def_s) = def_span {
2248 err.span_label(def_s, &format!("defined here"));
2253 let formal_tys = if tuple_arguments == TupleArguments {
2254 let tuple_type = self.structurally_resolved_type(sp, fn_inputs[0]);
2255 match tuple_type.sty {
2256 ty::TyTuple(arg_types, _) if arg_types.len() != args.len() => {
2257 parameter_count_error(tcx.sess, sp_args, arg_types.len(), args.len(),
2258 "E0057", false, def_span);
2259 expected_arg_tys = &[];
2260 self.err_args(args.len())
2262 ty::TyTuple(arg_types, _) => {
2263 expected_arg_tys = match expected_arg_tys.get(0) {
2264 Some(&ty) => match ty.sty {
2265 ty::TyTuple(ref tys, _) => &tys,
2273 span_err!(tcx.sess, sp, E0059,
2274 "cannot use call notation; the first type parameter \
2275 for the function trait is neither a tuple nor unit");
2276 expected_arg_tys = &[];
2277 self.err_args(args.len())
2280 } else if expected_arg_count == supplied_arg_count {
2282 } else if variadic {
2283 if supplied_arg_count >= expected_arg_count {
2286 parameter_count_error(tcx.sess, sp_args, expected_arg_count,
2287 supplied_arg_count, "E0060", true, def_span);
2288 expected_arg_tys = &[];
2289 self.err_args(supplied_arg_count)
2292 parameter_count_error(tcx.sess, sp_args, expected_arg_count,
2293 supplied_arg_count, "E0061", false, def_span);
2294 expected_arg_tys = &[];
2295 self.err_args(supplied_arg_count)
2298 debug!("check_argument_types: formal_tys={:?}",
2299 formal_tys.iter().map(|t| self.ty_to_string(*t)).collect::<Vec<String>>());
2301 // Check the arguments.
2302 // We do this in a pretty awful way: first we typecheck any arguments
2303 // that are not closures, then we typecheck the closures. This is so
2304 // that we have more information about the types of arguments when we
2305 // typecheck the functions. This isn't really the right way to do this.
2306 for &check_closures in &[false, true] {
2307 debug!("check_closures={}", check_closures);
2309 // More awful hacks: before we check argument types, try to do
2310 // an "opportunistic" vtable resolution of any trait bounds on
2311 // the call. This helps coercions.
2313 self.select_obligations_where_possible();
2316 // For variadic functions, we don't have a declared type for all of
2317 // the arguments hence we only do our usual type checking with
2318 // the arguments who's types we do know.
2319 let t = if variadic {
2321 } else if tuple_arguments == TupleArguments {
2326 for (i, arg) in args.iter().take(t).enumerate() {
2327 // Warn only for the first loop (the "no closures" one).
2328 // Closure arguments themselves can't be diverging, but
2329 // a previous argument can, e.g. `foo(panic!(), || {})`.
2330 if !check_closures {
2331 self.warn_if_unreachable(arg.id, arg.span, "expression");
2334 let is_closure = match arg.node {
2335 hir::ExprClosure(..) => true,
2339 if is_closure != check_closures {
2343 debug!("checking the argument");
2344 let formal_ty = formal_tys[i];
2346 // The special-cased logic below has three functions:
2347 // 1. Provide as good of an expected type as possible.
2348 let expected = expected_arg_tys.get(i).map(|&ty| {
2349 Expectation::rvalue_hint(self, ty)
2352 let checked_ty = self.check_expr_with_expectation(
2354 expected.unwrap_or(ExpectHasType(formal_ty)));
2356 // 2. Coerce to the most detailed type that could be coerced
2357 // to, which is `expected_ty` if `rvalue_hint` returns an
2358 // `ExpectHasType(expected_ty)`, or the `formal_ty` otherwise.
2359 let coerce_ty = expected.and_then(|e| e.only_has_type(self));
2360 self.demand_coerce(&arg, checked_ty, coerce_ty.unwrap_or(formal_ty));
2362 // 3. Relate the expected type and the formal one,
2363 // if the expected type was used for the coercion.
2364 coerce_ty.map(|ty| self.demand_suptype(arg.span, formal_ty, ty));
2368 // We also need to make sure we at least write the ty of the other
2369 // arguments which we skipped above.
2371 for arg in args.iter().skip(expected_arg_count) {
2372 let arg_ty = self.check_expr(&arg);
2374 // There are a few types which get autopromoted when passed via varargs
2375 // in C but we just error out instead and require explicit casts.
2376 let arg_ty = self.structurally_resolved_type(arg.span,
2379 ty::TyFloat(ast::FloatTy::F32) => {
2380 self.type_error_message(arg.span, |t| {
2381 format!("can't pass an `{}` to variadic \
2382 function, cast to `c_double`", t)
2385 ty::TyInt(ast::IntTy::I8) | ty::TyInt(ast::IntTy::I16) | ty::TyBool => {
2386 self.type_error_message(arg.span, |t| {
2387 format!("can't pass `{}` to variadic \
2388 function, cast to `c_int`",
2392 ty::TyUint(ast::UintTy::U8) | ty::TyUint(ast::UintTy::U16) => {
2393 self.type_error_message(arg.span, |t| {
2394 format!("can't pass `{}` to variadic \
2395 function, cast to `c_uint`",
2399 ty::TyFnDef(.., f) => {
2400 let ptr_ty = self.tcx.mk_fn_ptr(f);
2401 let ptr_ty = self.resolve_type_vars_if_possible(&ptr_ty);
2402 self.type_error_message(arg.span,
2404 format!("can't pass `{}` to variadic \
2405 function, cast to `{}`", t, ptr_ty)
2414 fn err_args(&self, len: usize) -> Vec<Ty<'tcx>> {
2415 (0..len).map(|_| self.tcx.types.err).collect()
2418 // AST fragment checking
2421 expected: Expectation<'tcx>)
2427 ast::LitKind::Str(..) => tcx.mk_static_str(),
2428 ast::LitKind::ByteStr(ref v) => {
2429 tcx.mk_imm_ref(tcx.mk_region(ty::ReStatic),
2430 tcx.mk_array(tcx.types.u8, v.len()))
2432 ast::LitKind::Byte(_) => tcx.types.u8,
2433 ast::LitKind::Char(_) => tcx.types.char,
2434 ast::LitKind::Int(_, ast::LitIntType::Signed(t)) => tcx.mk_mach_int(t),
2435 ast::LitKind::Int(_, ast::LitIntType::Unsigned(t)) => tcx.mk_mach_uint(t),
2436 ast::LitKind::Int(_, ast::LitIntType::Unsuffixed) => {
2437 let opt_ty = expected.to_option(self).and_then(|ty| {
2439 ty::TyInt(_) | ty::TyUint(_) => Some(ty),
2440 ty::TyChar => Some(tcx.types.u8),
2441 ty::TyRawPtr(..) => Some(tcx.types.usize),
2442 ty::TyFnDef(..) | ty::TyFnPtr(_) => Some(tcx.types.usize),
2446 opt_ty.unwrap_or_else(
2447 || tcx.mk_int_var(self.next_int_var_id()))
2449 ast::LitKind::Float(_, t) => tcx.mk_mach_float(t),
2450 ast::LitKind::FloatUnsuffixed(_) => {
2451 let opt_ty = expected.to_option(self).and_then(|ty| {
2453 ty::TyFloat(_) => Some(ty),
2457 opt_ty.unwrap_or_else(
2458 || tcx.mk_float_var(self.next_float_var_id()))
2460 ast::LitKind::Bool(_) => tcx.types.bool
2464 fn check_expr_eq_type(&self,
2465 expr: &'gcx hir::Expr,
2466 expected: Ty<'tcx>) {
2467 let ty = self.check_expr_with_hint(expr, expected);
2468 self.demand_eqtype(expr.span, expected, ty);
2471 pub fn check_expr_has_type(&self,
2472 expr: &'gcx hir::Expr,
2473 expected: Ty<'tcx>) -> Ty<'tcx> {
2474 let mut ty = self.check_expr_with_hint(expr, expected);
2476 // While we don't allow *arbitrary* coercions here, we *do* allow
2477 // coercions from ! to `expected`.
2479 assert!(!self.tables.borrow().adjustments.contains_key(&expr.id),
2480 "expression with never type wound up being adjusted");
2481 let adj_ty = self.next_diverging_ty_var(
2482 TypeVariableOrigin::AdjustmentType(expr.span));
2483 self.write_adjustment(expr.id, adjustment::Adjustment {
2484 kind: adjustment::Adjust::NeverToAny,
2490 self.demand_suptype(expr.span, expected, ty);
2494 fn check_expr_coercable_to_type(&self,
2495 expr: &'gcx hir::Expr,
2496 expected: Ty<'tcx>) -> Ty<'tcx> {
2497 let ty = self.check_expr_with_hint(expr, expected);
2498 self.demand_coerce(expr, ty, expected);
2502 fn check_expr_with_hint(&self, expr: &'gcx hir::Expr,
2503 expected: Ty<'tcx>) -> Ty<'tcx> {
2504 self.check_expr_with_expectation(expr, ExpectHasType(expected))
2507 fn check_expr_with_expectation(&self,
2508 expr: &'gcx hir::Expr,
2509 expected: Expectation<'tcx>) -> Ty<'tcx> {
2510 self.check_expr_with_expectation_and_lvalue_pref(expr, expected, NoPreference)
2513 fn check_expr(&self, expr: &'gcx hir::Expr) -> Ty<'tcx> {
2514 self.check_expr_with_expectation(expr, NoExpectation)
2517 fn check_expr_with_lvalue_pref(&self, expr: &'gcx hir::Expr,
2518 lvalue_pref: LvaluePreference) -> Ty<'tcx> {
2519 self.check_expr_with_expectation_and_lvalue_pref(expr, NoExpectation, lvalue_pref)
2522 // determine the `self` type, using fresh variables for all variables
2523 // declared on the impl declaration e.g., `impl<A,B> for Vec<(A,B)>`
2524 // would return ($0, $1) where $0 and $1 are freshly instantiated type
2526 pub fn impl_self_ty(&self,
2527 span: Span, // (potential) receiver for this impl
2529 -> TypeAndSubsts<'tcx> {
2530 let ity = self.tcx.item_type(did);
2531 debug!("impl_self_ty: ity={:?}", ity);
2533 let substs = self.fresh_substs_for_item(span, did);
2534 let substd_ty = self.instantiate_type_scheme(span, &substs, &ity);
2536 TypeAndSubsts { substs: substs, ty: substd_ty }
2539 /// Unifies the output type with the expected type early, for more coercions
2540 /// and forward type information on the input expressions.
2541 fn expected_inputs_for_expected_output(&self,
2543 expected_ret: Expectation<'tcx>,
2544 formal_ret: Ty<'tcx>,
2545 formal_args: &[Ty<'tcx>])
2547 let expected_args = expected_ret.only_has_type(self).and_then(|ret_ty| {
2548 self.fudge_regions_if_ok(&RegionVariableOrigin::Coercion(call_span), || {
2549 // Attempt to apply a subtyping relationship between the formal
2550 // return type (likely containing type variables if the function
2551 // is polymorphic) and the expected return type.
2552 // No argument expectations are produced if unification fails.
2553 let origin = self.misc(call_span);
2554 let ures = self.sub_types(false, &origin, formal_ret, ret_ty);
2555 // FIXME(#15760) can't use try! here, FromError doesn't default
2556 // to identity so the resulting type is not constrained.
2558 Ok(ok) => self.register_infer_ok_obligations(ok),
2559 Err(e) => return Err(e),
2562 // Record all the argument types, with the substitutions
2563 // produced from the above subtyping unification.
2564 Ok(formal_args.iter().map(|ty| {
2565 self.resolve_type_vars_if_possible(ty)
2568 }).unwrap_or(vec![]);
2569 debug!("expected_inputs_for_expected_output(formal={:?} -> {:?}, expected={:?} -> {:?})",
2570 formal_args, formal_ret,
2571 expected_args, expected_ret);
2575 // Checks a method call.
2576 fn check_method_call(&self,
2577 expr: &'gcx hir::Expr,
2578 method_name: Spanned<ast::Name>,
2579 args: &'gcx [hir::Expr],
2581 expected: Expectation<'tcx>,
2582 lvalue_pref: LvaluePreference) -> Ty<'tcx> {
2583 let rcvr = &args[0];
2584 let rcvr_t = self.check_expr_with_lvalue_pref(&rcvr, lvalue_pref);
2586 // no need to check for bot/err -- callee does that
2587 let expr_t = self.structurally_resolved_type(expr.span, rcvr_t);
2589 let tps = tps.iter().map(|ast_ty| self.to_ty(&ast_ty)).collect::<Vec<_>>();
2590 let fn_ty = match self.lookup_method(method_name.span,
2597 let method_ty = method.ty;
2598 let method_call = MethodCall::expr(expr.id);
2599 self.tables.borrow_mut().method_map.insert(method_call, method);
2603 if method_name.node != keywords::Invalid.name() {
2604 self.report_method_error(method_name.span,
2611 self.write_error(expr.id);
2616 // Call the generic checker.
2617 let ret_ty = self.check_method_argument_types(method_name.span, fn_ty,
2625 fn check_return_expr(&self, return_expr: &'gcx hir::Expr) {
2629 .unwrap_or_else(|| span_bug!(return_expr.span,
2630 "check_return_expr called outside fn body"));
2632 let ret_ty = ret_coercion.borrow().expected_ty();
2633 let return_expr_ty = self.check_expr_with_hint(return_expr, ret_ty);
2634 ret_coercion.borrow_mut()
2636 &self.misc(return_expr.span),
2639 self.diverges.get());
2643 // A generic function for checking the then and else in an if
2645 fn check_then_else(&self,
2646 cond_expr: &'gcx hir::Expr,
2647 then_expr: &'gcx hir::Expr,
2648 opt_else_expr: Option<&'gcx hir::Expr>,
2650 expected: Expectation<'tcx>) -> Ty<'tcx> {
2651 let cond_ty = self.check_expr_has_type(cond_expr, self.tcx.types.bool);
2652 let cond_diverges = self.diverges.get();
2653 self.diverges.set(Diverges::Maybe);
2655 let expected = expected.adjust_for_branches(self);
2656 let then_ty = self.check_expr_with_expectation(then_expr, expected);
2657 let then_diverges = self.diverges.get();
2658 self.diverges.set(Diverges::Maybe);
2660 // We've already taken the expected type's preferences
2661 // into account when typing the `then` branch. To figure
2662 // out the initial shot at a LUB, we thus only consider
2663 // `expected` if it represents a *hard* constraint
2664 // (`only_has_type`); otherwise, we just go with a
2665 // fresh type variable.
2666 let coerce_to_ty = expected.coercion_target_type(self, sp);
2667 let mut coerce: DynamicCoerceMany = CoerceMany::new(coerce_to_ty);
2669 let if_cause = self.cause(sp, ObligationCauseCode::IfExpression);
2670 coerce.coerce(self, &if_cause, then_expr, then_ty, then_diverges);
2672 if let Some(else_expr) = opt_else_expr {
2673 let else_ty = self.check_expr_with_expectation(else_expr, expected);
2674 let else_diverges = self.diverges.get();
2676 coerce.coerce(self, &if_cause, else_expr, else_ty, else_diverges);
2678 // We won't diverge unless both branches do (or the condition does).
2679 self.diverges.set(cond_diverges | then_diverges & else_diverges);
2681 let else_cause = self.cause(sp, ObligationCauseCode::IfExpressionWithNoElse);
2682 coerce.coerce_forced_unit(self, &else_cause, &mut |_| ());
2684 // If the condition is false we can't diverge.
2685 self.diverges.set(cond_diverges);
2688 let result_ty = coerce.complete(self);
2689 if cond_ty.references_error() {
2696 // Check field access expressions
2697 fn check_field(&self,
2698 expr: &'gcx hir::Expr,
2699 lvalue_pref: LvaluePreference,
2700 base: &'gcx hir::Expr,
2701 field: &Spanned<ast::Name>) -> Ty<'tcx> {
2702 let expr_t = self.check_expr_with_lvalue_pref(base, lvalue_pref);
2703 let expr_t = self.structurally_resolved_type(expr.span,
2705 let mut private_candidate = None;
2706 let mut autoderef = self.autoderef(expr.span, expr_t);
2707 while let Some((base_t, autoderefs)) = autoderef.next() {
2709 ty::TyAdt(base_def, substs) if !base_def.is_enum() => {
2710 debug!("struct named {:?}", base_t);
2711 if let Some(field) = base_def.struct_variant().find_field_named(field.node) {
2712 let field_ty = self.field_ty(expr.span, field, substs);
2713 if self.tcx.vis_is_accessible_from(field.vis, self.body_id) {
2714 autoderef.finalize(lvalue_pref, &[base]);
2715 self.write_autoderef_adjustment(base.id, autoderefs, base_t);
2717 self.tcx.check_stability(field.did, expr.id, expr.span);
2721 private_candidate = Some((base_def.did, field_ty));
2727 autoderef.unambiguous_final_ty();
2729 if let Some((did, field_ty)) = private_candidate {
2730 let struct_path = self.tcx().item_path_str(did);
2731 let msg = format!("field `{}` of struct `{}` is private", field.node, struct_path);
2732 let mut err = self.tcx().sess.struct_span_err(expr.span, &msg);
2733 // Also check if an accessible method exists, which is often what is meant.
2734 if self.method_exists(field.span, field.node, expr_t, expr.id, false) {
2735 err.note(&format!("a method `{}` also exists, perhaps you wish to call it",
2740 } else if field.node == keywords::Invalid.name() {
2741 self.tcx().types.err
2742 } else if self.method_exists(field.span, field.node, expr_t, expr.id, true) {
2743 self.type_error_struct(field.span, |actual| {
2744 format!("attempted to take value of method `{}` on type \
2745 `{}`", field.node, actual)
2747 .help("maybe a `()` to call it is missing? \
2748 If not, try an anonymous function")
2750 self.tcx().types.err
2752 let mut err = self.type_error_struct(field.span, |actual| {
2753 format!("no field `{}` on type `{}`",
2757 ty::TyAdt(def, _) if !def.is_enum() => {
2758 if let Some(suggested_field_name) =
2759 Self::suggest_field_name(def.struct_variant(), field, vec![]) {
2760 err.span_label(field.span,
2761 &format!("did you mean `{}`?", suggested_field_name));
2763 err.span_label(field.span,
2764 &format!("unknown field"));
2767 ty::TyRawPtr(..) => {
2768 err.note(&format!("`{0}` is a native pointer; perhaps you need to deref with \
2770 self.tcx.hir.node_to_pretty_string(base.id),
2776 self.tcx().types.err
2780 // Return an hint about the closest match in field names
2781 fn suggest_field_name(variant: &'tcx ty::VariantDef,
2782 field: &Spanned<ast::Name>,
2783 skip : Vec<InternedString>)
2785 let name = field.node.as_str();
2786 let names = variant.fields.iter().filter_map(|field| {
2787 // ignore already set fields and private fields from non-local crates
2788 if skip.iter().any(|x| *x == field.name.as_str()) ||
2789 (variant.did.krate != LOCAL_CRATE && field.vis != Visibility::Public) {
2796 // only find fits with at least one matching letter
2797 find_best_match_for_name(names, &name, Some(name.len()))
2800 // Check tuple index expressions
2801 fn check_tup_field(&self,
2802 expr: &'gcx hir::Expr,
2803 lvalue_pref: LvaluePreference,
2804 base: &'gcx hir::Expr,
2805 idx: codemap::Spanned<usize>) -> Ty<'tcx> {
2806 let expr_t = self.check_expr_with_lvalue_pref(base, lvalue_pref);
2807 let expr_t = self.structurally_resolved_type(expr.span,
2809 let mut private_candidate = None;
2810 let mut tuple_like = false;
2811 let mut autoderef = self.autoderef(expr.span, expr_t);
2812 while let Some((base_t, autoderefs)) = autoderef.next() {
2813 let field = match base_t.sty {
2814 ty::TyAdt(base_def, substs) if base_def.is_struct() => {
2815 tuple_like = base_def.struct_variant().ctor_kind == CtorKind::Fn;
2816 if !tuple_like { continue }
2818 debug!("tuple struct named {:?}", base_t);
2819 base_def.struct_variant().fields.get(idx.node).and_then(|field| {
2820 let field_ty = self.field_ty(expr.span, field, substs);
2821 private_candidate = Some((base_def.did, field_ty));
2822 if self.tcx.vis_is_accessible_from(field.vis, self.body_id) {
2823 self.tcx.check_stability(field.did, expr.id, expr.span);
2830 ty::TyTuple(ref v, _) => {
2832 v.get(idx.node).cloned()
2837 if let Some(field_ty) = field {
2838 autoderef.finalize(lvalue_pref, &[base]);
2839 self.write_autoderef_adjustment(base.id, autoderefs, base_t);
2843 autoderef.unambiguous_final_ty();
2845 if let Some((did, field_ty)) = private_candidate {
2846 let struct_path = self.tcx().item_path_str(did);
2847 let msg = format!("field `{}` of struct `{}` is private", idx.node, struct_path);
2848 self.tcx().sess.span_err(expr.span, &msg);
2852 self.type_error_message(
2856 format!("attempted out-of-bounds tuple index `{}` on \
2861 format!("attempted tuple index `{}` on type `{}`, but the \
2862 type was not a tuple or tuple struct",
2869 self.tcx().types.err
2872 fn report_unknown_field(&self,
2874 variant: &'tcx ty::VariantDef,
2876 skip_fields: &[hir::Field],
2878 let mut err = self.type_error_struct_with_diag(
2880 |actual| match ty.sty {
2881 ty::TyAdt(adt, ..) if adt.is_enum() => {
2882 struct_span_err!(self.tcx.sess, field.name.span, E0559,
2883 "{} `{}::{}` has no field named `{}`",
2884 kind_name, actual, variant.name, field.name.node)
2887 struct_span_err!(self.tcx.sess, field.name.span, E0560,
2888 "{} `{}` has no field named `{}`",
2889 kind_name, actual, field.name.node)
2893 // prevent all specified fields from being suggested
2894 let skip_fields = skip_fields.iter().map(|ref x| x.name.node.as_str());
2895 if let Some(field_name) = Self::suggest_field_name(variant,
2897 skip_fields.collect()) {
2898 err.span_label(field.name.span,
2899 &format!("field does not exist - did you mean `{}`?", field_name));
2902 ty::TyAdt(adt, ..) if adt.is_enum() => {
2903 err.span_label(field.name.span, &format!("`{}::{}` does not have this field",
2907 err.span_label(field.name.span, &format!("`{}` does not have this field", ty));
2914 fn check_expr_struct_fields(&self,
2916 expected: Expectation<'tcx>,
2917 expr_id: ast::NodeId,
2919 variant: &'tcx ty::VariantDef,
2920 ast_fields: &'gcx [hir::Field],
2921 check_completeness: bool) {
2925 self.expected_inputs_for_expected_output(span, expected, adt_ty, &[adt_ty])
2926 .get(0).cloned().unwrap_or(adt_ty);
2928 let (substs, hint_substs, adt_kind, kind_name) = match (&adt_ty.sty, &adt_ty_hint.sty) {
2929 (&ty::TyAdt(adt, substs), &ty::TyAdt(_, hint_substs)) => {
2930 (substs, hint_substs, adt.adt_kind(), adt.variant_descr())
2932 _ => span_bug!(span, "non-ADT passed to check_expr_struct_fields")
2935 let mut remaining_fields = FxHashMap();
2936 for field in &variant.fields {
2937 remaining_fields.insert(field.name, field);
2940 let mut seen_fields = FxHashMap();
2942 let mut error_happened = false;
2944 // Typecheck each field.
2945 for field in ast_fields {
2946 let final_field_type;
2947 let field_type_hint;
2949 if let Some(v_field) = remaining_fields.remove(&field.name.node) {
2950 final_field_type = self.field_ty(field.span, v_field, substs);
2951 field_type_hint = self.field_ty(field.span, v_field, hint_substs);
2953 seen_fields.insert(field.name.node, field.span);
2955 // we don't look at stability attributes on
2956 // struct-like enums (yet...), but it's definitely not
2957 // a bug to have construct one.
2958 if adt_kind != ty::AdtKind::Enum {
2959 tcx.check_stability(v_field.did, expr_id, field.span);
2962 error_happened = true;
2963 final_field_type = tcx.types.err;
2964 field_type_hint = tcx.types.err;
2965 if let Some(_) = variant.find_field_named(field.name.node) {
2966 let mut err = struct_span_err!(self.tcx.sess,
2969 "field `{}` specified more than once",
2972 err.span_label(field.name.span, &format!("used more than once"));
2974 if let Some(prev_span) = seen_fields.get(&field.name.node) {
2975 err.span_label(*prev_span, &format!("first use of `{}`", field.name.node));
2980 self.report_unknown_field(adt_ty, variant, field, ast_fields, kind_name);
2984 // Make sure to give a type to the field even if there's
2985 // an error, so we can continue typechecking
2986 let ty = self.check_expr_with_hint(&field.expr, field_type_hint);
2987 self.demand_coerce(&field.expr, ty, final_field_type);
2990 // Make sure the programmer specified correct number of fields.
2991 if kind_name == "union" {
2992 if ast_fields.len() != 1 {
2993 tcx.sess.span_err(span, "union expressions should have exactly one field");
2995 } else if check_completeness && !error_happened && !remaining_fields.is_empty() {
2996 let len = remaining_fields.len();
2998 let mut displayable_field_names = remaining_fields
3000 .map(|x| x.as_str())
3001 .collect::<Vec<_>>();
3003 displayable_field_names.sort();
3005 let truncated_fields_error = if len <= 3 {
3008 format!(" and {} other field{}", (len - 3), if len - 3 == 1 {""} else {"s"})
3011 let remaining_fields_names = displayable_field_names.iter().take(3)
3012 .map(|n| format!("`{}`", n))
3013 .collect::<Vec<_>>()
3016 struct_span_err!(tcx.sess, span, E0063,
3017 "missing field{} {}{} in initializer of `{}`",
3018 if remaining_fields.len() == 1 {""} else {"s"},
3019 remaining_fields_names,
3020 truncated_fields_error,
3022 .span_label(span, &format!("missing {}{}",
3023 remaining_fields_names,
3024 truncated_fields_error))
3029 fn check_struct_fields_on_error(&self,
3030 fields: &'gcx [hir::Field],
3031 base_expr: &'gcx Option<P<hir::Expr>>) {
3032 for field in fields {
3033 self.check_expr(&field.expr);
3037 self.check_expr(&base);
3043 pub fn check_struct_path(&self,
3045 node_id: ast::NodeId)
3046 -> Option<(&'tcx ty::VariantDef, Ty<'tcx>)> {
3047 let path_span = match *qpath {
3048 hir::QPath::Resolved(_, ref path) => path.span,
3049 hir::QPath::TypeRelative(ref qself, _) => qself.span
3051 let (def, ty) = self.finish_resolving_struct_path(qpath, path_span, node_id);
3052 let variant = match def {
3054 self.set_tainted_by_errors();
3057 Def::Variant(..) => {
3059 ty::TyAdt(adt, substs) => {
3060 Some((adt.variant_of_def(def), adt.did, substs))
3062 _ => bug!("unexpected type: {:?}", ty.sty)
3065 Def::Struct(..) | Def::Union(..) | Def::TyAlias(..) |
3066 Def::AssociatedTy(..) | Def::SelfTy(..) => {
3068 ty::TyAdt(adt, substs) if !adt.is_enum() => {
3069 Some((adt.struct_variant(), adt.did, substs))
3074 _ => bug!("unexpected definition: {:?}", def)
3077 if let Some((variant, did, substs)) = variant {
3078 // Check bounds on type arguments used in the path.
3079 let bounds = self.instantiate_bounds(path_span, did, substs);
3080 let cause = traits::ObligationCause::new(path_span, self.body_id,
3081 traits::ItemObligation(did));
3082 self.add_obligations_for_parameters(cause, &bounds);
3086 struct_span_err!(self.tcx.sess, path_span, E0071,
3087 "expected struct, variant or union type, found {}",
3088 ty.sort_string(self.tcx))
3089 .span_label(path_span, &format!("not a struct"))
3095 fn check_expr_struct(&self,
3097 expected: Expectation<'tcx>,
3099 fields: &'gcx [hir::Field],
3100 base_expr: &'gcx Option<P<hir::Expr>>) -> Ty<'tcx>
3102 // Find the relevant variant
3103 let (variant, struct_ty) =
3104 if let Some(variant_ty) = self.check_struct_path(qpath, expr.id) {
3107 self.check_struct_fields_on_error(fields, base_expr);
3108 return self.tcx.types.err;
3111 let path_span = match *qpath {
3112 hir::QPath::Resolved(_, ref path) => path.span,
3113 hir::QPath::TypeRelative(ref qself, _) => qself.span
3116 self.check_expr_struct_fields(struct_ty, expected, expr.id, path_span, variant, fields,
3117 base_expr.is_none());
3118 if let &Some(ref base_expr) = base_expr {
3119 self.check_expr_has_type(base_expr, struct_ty);
3120 match struct_ty.sty {
3121 ty::TyAdt(adt, substs) if adt.is_struct() => {
3122 self.tables.borrow_mut().fru_field_types.insert(
3124 adt.struct_variant().fields.iter().map(|f| {
3125 self.normalize_associated_types_in(
3126 expr.span, &f.ty(self.tcx, substs)
3132 span_err!(self.tcx.sess, base_expr.span, E0436,
3133 "functional record update syntax requires a struct");
3137 self.require_type_is_sized(struct_ty, expr.span, traits::StructInitializerSized);
3143 /// If an expression has any sub-expressions that result in a type error,
3144 /// inspecting that expression's type with `ty.references_error()` will return
3145 /// true. Likewise, if an expression is known to diverge, inspecting its
3146 /// type with `ty::type_is_bot` will return true (n.b.: since Rust is
3147 /// strict, _|_ can appear in the type of an expression that does not,
3148 /// itself, diverge: for example, fn() -> _|_.)
3149 /// Note that inspecting a type's structure *directly* may expose the fact
3150 /// that there are actually multiple representations for `TyError`, so avoid
3151 /// that when err needs to be handled differently.
3152 fn check_expr_with_expectation_and_lvalue_pref(&self,
3153 expr: &'gcx hir::Expr,
3154 expected: Expectation<'tcx>,
3155 lvalue_pref: LvaluePreference) -> Ty<'tcx> {
3156 debug!(">> typechecking: expr={:?} expected={:?}",
3159 // Warn for expressions after diverging siblings.
3160 self.warn_if_unreachable(expr.id, expr.span, "expression");
3162 // Hide the outer diverging and has_errors flags.
3163 let old_diverges = self.diverges.get();
3164 let old_has_errors = self.has_errors.get();
3165 self.diverges.set(Diverges::Maybe);
3166 self.has_errors.set(false);
3168 let ty = self.check_expr_kind(expr, expected, lvalue_pref);
3170 // Warn for non-block expressions with diverging children.
3173 hir::ExprLoop(..) | hir::ExprWhile(..) |
3174 hir::ExprIf(..) | hir::ExprMatch(..) => {}
3176 _ => self.warn_if_unreachable(expr.id, expr.span, "expression")
3179 // Any expression that produces a value of type `!` must have diverged
3181 self.diverges.set(self.diverges.get() | Diverges::Always);
3184 // Record the type, which applies it effects.
3185 // We need to do this after the warning above, so that
3186 // we don't warn for the diverging expression itself.
3187 self.write_ty(expr.id, ty);
3189 // Combine the diverging and has_error flags.
3190 self.diverges.set(self.diverges.get() | old_diverges);
3191 self.has_errors.set(self.has_errors.get() | old_has_errors);
3193 debug!("type of {} is...", self.tcx.hir.node_to_string(expr.id));
3194 debug!("... {:?}, expected is {:?}", ty, expected);
3199 fn check_expr_kind(&self,
3200 expr: &'gcx hir::Expr,
3201 expected: Expectation<'tcx>,
3202 lvalue_pref: LvaluePreference) -> Ty<'tcx> {
3206 hir::ExprBox(ref subexpr) => {
3207 let expected_inner = expected.to_option(self).map_or(NoExpectation, |ty| {
3209 ty::TyAdt(def, _) if def.is_box()
3210 => Expectation::rvalue_hint(self, ty.boxed_ty()),
3214 let referent_ty = self.check_expr_with_expectation(subexpr, expected_inner);
3215 tcx.mk_box(referent_ty)
3218 hir::ExprLit(ref lit) => {
3219 self.check_lit(&lit, expected)
3221 hir::ExprBinary(op, ref lhs, ref rhs) => {
3222 self.check_binop(expr, op, lhs, rhs)
3224 hir::ExprAssignOp(op, ref lhs, ref rhs) => {
3225 self.check_binop_assign(expr, op, lhs, rhs)
3227 hir::ExprUnary(unop, ref oprnd) => {
3228 let expected_inner = match unop {
3229 hir::UnNot | hir::UnNeg => {
3236 let lvalue_pref = match unop {
3237 hir::UnDeref => lvalue_pref,
3240 let mut oprnd_t = self.check_expr_with_expectation_and_lvalue_pref(&oprnd,
3244 if !oprnd_t.references_error() {
3247 oprnd_t = self.structurally_resolved_type(expr.span, oprnd_t);
3249 if let Some(mt) = oprnd_t.builtin_deref(true, NoPreference) {
3251 } else if let Some(method) = self.try_overloaded_deref(
3252 expr.span, Some(&oprnd), oprnd_t, lvalue_pref) {
3253 oprnd_t = self.make_overloaded_lvalue_return_type(method).ty;
3254 self.tables.borrow_mut().method_map.insert(MethodCall::expr(expr.id),
3257 self.type_error_message(expr.span, |actual| {
3258 format!("type `{}` cannot be \
3259 dereferenced", actual)
3261 oprnd_t = tcx.types.err;
3265 oprnd_t = self.structurally_resolved_type(oprnd.span,
3267 let result = self.check_user_unop("!", "not",
3268 tcx.lang_items.not_trait(),
3269 expr, &oprnd, oprnd_t, unop);
3270 // If it's builtin, we can reuse the type, this helps inference.
3271 if !(oprnd_t.is_integral() || oprnd_t.sty == ty::TyBool) {
3276 oprnd_t = self.structurally_resolved_type(oprnd.span,
3278 let result = self.check_user_unop("-", "neg",
3279 tcx.lang_items.neg_trait(),
3280 expr, &oprnd, oprnd_t, unop);
3281 // If it's builtin, we can reuse the type, this helps inference.
3282 if !(oprnd_t.is_integral() || oprnd_t.is_fp()) {
3290 hir::ExprAddrOf(mutbl, ref oprnd) => {
3291 let hint = expected.only_has_type(self).map_or(NoExpectation, |ty| {
3293 ty::TyRef(_, ref mt) | ty::TyRawPtr(ref mt) => {
3294 if self.tcx.expr_is_lval(&oprnd) {
3295 // Lvalues may legitimately have unsized types.
3296 // For example, dereferences of a fat pointer and
3297 // the last field of a struct can be unsized.
3298 ExpectHasType(mt.ty)
3300 Expectation::rvalue_hint(self, mt.ty)
3306 let lvalue_pref = LvaluePreference::from_mutbl(mutbl);
3307 let ty = self.check_expr_with_expectation_and_lvalue_pref(&oprnd, hint, lvalue_pref);
3309 let tm = ty::TypeAndMut { ty: ty, mutbl: mutbl };
3310 if tm.ty.references_error() {
3313 // Note: at this point, we cannot say what the best lifetime
3314 // is to use for resulting pointer. We want to use the
3315 // shortest lifetime possible so as to avoid spurious borrowck
3316 // errors. Moreover, the longest lifetime will depend on the
3317 // precise details of the value whose address is being taken
3318 // (and how long it is valid), which we don't know yet until type
3319 // inference is complete.
3321 // Therefore, here we simply generate a region variable. The
3322 // region inferencer will then select the ultimate value.
3323 // Finally, borrowck is charged with guaranteeing that the
3324 // value whose address was taken can actually be made to live
3325 // as long as it needs to live.
3326 let region = self.next_region_var(infer::AddrOfRegion(expr.span));
3327 tcx.mk_ref(region, tm)
3330 hir::ExprPath(ref qpath) => {
3331 let (def, opt_ty, segments) = self.resolve_ty_and_def_ufcs(qpath,
3332 expr.id, expr.span);
3333 let ty = if def != Def::Err {
3334 self.instantiate_value_path(segments, opt_ty, def, expr.span, id)
3336 self.set_tainted_by_errors();
3340 // We always require that the type provided as the value for
3341 // a type parameter outlives the moment of instantiation.
3342 self.opt_node_ty_substs(expr.id, |item_substs| {
3343 self.add_wf_bounds(&item_substs.substs, expr);
3348 hir::ExprInlineAsm(_, ref outputs, ref inputs) => {
3349 for output in outputs {
3350 self.check_expr(output);
3352 for input in inputs {
3353 self.check_expr(input);
3357 hir::ExprBreak(destination, ref expr_opt) => {
3358 if let Some(target_id) = destination.target_id.opt_id() {
3359 let (e_ty, e_diverges, cause);
3360 if let Some(ref e) = *expr_opt {
3361 // If this is a break with a value, we need to type-check
3362 // the expression. Get an expected type from the loop context.
3363 let opt_coerce_to = {
3364 let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
3365 enclosing_breakables.find_breakable(target_id)
3368 .map(|coerce| coerce.expected_ty())
3371 // If the loop context is not a `loop { }`, then break with
3372 // a value is illegal, and `opt_coerce_to` will be `None`.
3373 // Just set expectation to error in that case.
3374 let coerce_to = opt_coerce_to.unwrap_or(tcx.types.err);
3376 // Recurse without `enclosing_breakables` borrowed.
3377 e_ty = self.check_expr_with_hint(e, coerce_to);
3378 e_diverges = self.diverges.get();
3379 cause = self.misc(e.span);
3381 // Otherwise, this is a break *without* a value. That's
3382 // always legal, and is equivalent to `break ()`.
3383 e_ty = tcx.mk_nil();
3384 e_diverges = Diverges::Maybe;
3385 cause = self.misc(expr.span);
3388 // Now that we have type-checked `expr_opt`, borrow
3389 // the `enclosing_loops` field and let's coerce the
3390 // type of `expr_opt` into what is expected.
3391 let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
3392 let ctxt = enclosing_breakables.find_breakable(target_id);
3393 if let Some(ref mut coerce) = ctxt.coerce {
3394 if let Some(ref e) = *expr_opt {
3395 coerce.coerce(self, &cause, e, e_ty, e_diverges);
3397 assert!(e_ty.is_nil());
3398 coerce.coerce_forced_unit(self, &cause, &mut |_| ());
3401 // If `ctxt.coerce` is `None`, we can just ignore
3402 // the type of the expresison. This is because
3403 // either this was a break *without* a value, in
3404 // which case it is always a legal type (`()`), or
3405 // else an error would have been flagged by the
3406 // `loops` pass for using break with an expression
3407 // where you are not supposed to.
3408 assert!(expr_opt.is_none() || self.tcx.sess.err_count() > 0);
3411 ctxt.may_break = true;
3413 // Otherwise, we failed to find the enclosing loop;
3414 // this can only happen if the `break` was not
3415 // inside a loop at all, which is caught by the
3416 // loop-checking pass.
3417 assert!(self.tcx.sess.err_count() > 0);
3420 // the type of a `break` is always `!`, since it diverges
3423 hir::ExprAgain(_) => { tcx.types.never }
3424 hir::ExprRet(ref expr_opt) => {
3425 if self.ret_coercion.is_none() {
3426 struct_span_err!(self.tcx.sess, expr.span, E0572,
3427 "return statement outside of function body").emit();
3428 } else if let Some(ref e) = *expr_opt {
3429 self.check_return_expr(e);
3431 let mut coercion = self.ret_coercion.as_ref().unwrap().borrow_mut();
3432 let cause = self.cause(expr.span, ObligationCauseCode::ReturnNoExpression);
3433 coercion.coerce_forced_unit(self, &cause, &mut |_| ());
3437 hir::ExprAssign(ref lhs, ref rhs) => {
3438 let lhs_ty = self.check_expr_with_lvalue_pref(&lhs, PreferMutLvalue);
3441 if !tcx.expr_is_lval(&lhs) {
3443 tcx.sess, expr.span, E0070,
3444 "invalid left-hand side expression")
3447 &format!("left-hand of expression not valid"))
3451 let rhs_ty = self.check_expr_coercable_to_type(&rhs, lhs_ty);
3453 self.require_type_is_sized(lhs_ty, lhs.span, traits::AssignmentLhsSized);
3455 if lhs_ty.references_error() || rhs_ty.references_error() {
3461 hir::ExprIf(ref cond, ref then_expr, ref opt_else_expr) => {
3462 self.check_then_else(&cond, then_expr, opt_else_expr.as_ref().map(|e| &**e),
3463 expr.span, expected)
3465 hir::ExprWhile(ref cond, ref body, _) => {
3466 let ctxt = BreakableCtxt {
3467 // cannot use break with a value from a while loop
3472 self.with_breakable_ctxt(expr.id, ctxt, || {
3473 self.check_expr_has_type(&cond, tcx.types.bool);
3474 let cond_diverging = self.diverges.get();
3475 self.check_block_no_value(&body);
3477 // We may never reach the body so it diverging means nothing.
3478 self.diverges.set(cond_diverging);
3483 hir::ExprLoop(ref body, _, source) => {
3484 let coerce = match source {
3485 // you can only use break with a value from a normal `loop { }`
3486 hir::LoopSource::Loop => {
3487 let coerce_to = expected.coercion_target_type(self, body.span);
3488 Some(CoerceMany::new(coerce_to))
3491 hir::LoopSource::WhileLet |
3492 hir::LoopSource::ForLoop => {
3497 let ctxt = BreakableCtxt {
3499 may_break: false, // will get updated if/when we find a `break`
3502 let (ctxt, ()) = self.with_breakable_ctxt(expr.id, ctxt, || {
3503 self.check_block_no_value(&body);
3507 // No way to know whether it's diverging because
3508 // of a `break` or an outer `break` or `return.
3509 self.diverges.set(Diverges::Maybe);
3512 // If we permit break with a value, then result type is
3513 // the LUB of the breaks (possibly ! if none); else, it
3514 // is nil. This makes sense because infinite loops
3515 // (which would have type !) are only possible iff we
3516 // permit break with a value [1].
3517 assert!(ctxt.coerce.is_some() || ctxt.may_break); // [1]
3518 ctxt.coerce.map(|c| c.complete(self)).unwrap_or(self.tcx.mk_nil())
3520 hir::ExprMatch(ref discrim, ref arms, match_src) => {
3521 self.check_match(expr, &discrim, arms, expected, match_src)
3523 hir::ExprClosure(capture, ref decl, body_id, _) => {
3524 self.check_expr_closure(expr, capture, &decl, body_id, expected)
3526 hir::ExprBlock(ref body) => {
3527 self.check_block_with_expected(&body, expected)
3529 hir::ExprCall(ref callee, ref args) => {
3530 self.check_call(expr, &callee, args, expected)
3532 hir::ExprMethodCall(name, ref tps, ref args) => {
3533 self.check_method_call(expr, name, args, &tps[..], expected, lvalue_pref)
3535 hir::ExprCast(ref e, ref t) => {
3536 // Find the type of `e`. Supply hints based on the type we are casting to,
3538 let t_cast = self.to_ty(t);
3539 let t_cast = self.resolve_type_vars_if_possible(&t_cast);
3540 let t_expr = self.check_expr_with_expectation(e, ExpectCastableToType(t_cast));
3541 let t_cast = self.resolve_type_vars_if_possible(&t_cast);
3542 let diverges = self.diverges.get();
3544 // Eagerly check for some obvious errors.
3545 if t_expr.references_error() || t_cast.references_error() {
3548 // Defer other checks until we're done type checking.
3549 let mut deferred_cast_checks = self.deferred_cast_checks.borrow_mut();
3550 match cast::CastCheck::new(self, e, t_expr, diverges, t_cast, t.span, expr.span) {
3552 deferred_cast_checks.push(cast_check);
3555 Err(ErrorReported) => {
3561 hir::ExprType(ref e, ref t) => {
3562 let typ = self.to_ty(&t);
3563 self.check_expr_eq_type(&e, typ);
3566 hir::ExprArray(ref args) => {
3567 let uty = expected.to_option(self).and_then(|uty| {
3569 ty::TyArray(ty, _) | ty::TySlice(ty) => Some(ty),
3574 let element_ty = if !args.is_empty() {
3575 let coerce_to = uty.unwrap_or_else(
3576 || self.next_ty_var(TypeVariableOrigin::TypeInference(expr.span)));
3577 let mut coerce = CoerceMany::with_coercion_sites(coerce_to, args);
3578 assert_eq!(self.diverges.get(), Diverges::Maybe);
3580 let e_ty = self.check_expr_with_hint(e, coerce_to);
3581 let cause = self.misc(e.span);
3582 coerce.coerce(self, &cause, e, e_ty, self.diverges.get());
3584 coerce.complete(self)
3586 self.next_ty_var(TypeVariableOrigin::TypeInference(expr.span))
3588 tcx.mk_array(element_ty, args.len())
3590 hir::ExprRepeat(ref element, count) => {
3591 let count = eval_length(self.tcx.global_tcx(), count, "repeat count")
3594 let uty = match expected {
3595 ExpectHasType(uty) => {
3597 ty::TyArray(ty, _) | ty::TySlice(ty) => Some(ty),
3604 let (element_ty, t) = match uty {
3606 self.check_expr_coercable_to_type(&element, uty);
3610 let t: Ty = self.next_ty_var(TypeVariableOrigin::MiscVariable(element.span));
3611 let element_ty = self.check_expr_has_type(&element, t);
3617 // For [foo, ..n] where n > 1, `foo` must have
3619 let lang_item = self.tcx.require_lang_item(lang_items::CopyTraitLangItem);
3620 self.require_type_meets(t, expr.span, traits::RepeatVec, lang_item);
3623 if element_ty.references_error() {
3626 tcx.mk_array(t, count)
3629 hir::ExprTup(ref elts) => {
3630 let flds = expected.only_has_type(self).and_then(|ty| {
3632 ty::TyTuple(ref flds, _) => Some(&flds[..]),
3637 let elt_ts_iter = elts.iter().enumerate().map(|(i, e)| {
3638 let t = match flds {
3639 Some(ref fs) if i < fs.len() => {
3641 self.check_expr_coercable_to_type(&e, ety);
3645 self.check_expr_with_expectation(&e, NoExpectation)
3650 let tuple = tcx.mk_tup(elt_ts_iter, false);
3651 if tuple.references_error() {
3657 hir::ExprStruct(ref qpath, ref fields, ref base_expr) => {
3658 self.check_expr_struct(expr, expected, qpath, fields, base_expr)
3660 hir::ExprField(ref base, ref field) => {
3661 self.check_field(expr, lvalue_pref, &base, field)
3663 hir::ExprTupField(ref base, idx) => {
3664 self.check_tup_field(expr, lvalue_pref, &base, idx)
3666 hir::ExprIndex(ref base, ref idx) => {
3667 let base_t = self.check_expr_with_lvalue_pref(&base, lvalue_pref);
3668 let idx_t = self.check_expr(&idx);
3670 if base_t.references_error() {
3672 } else if idx_t.references_error() {
3675 let base_t = self.structurally_resolved_type(expr.span, base_t);
3676 match self.lookup_indexing(expr, base, base_t, idx_t, lvalue_pref) {
3677 Some((index_ty, element_ty)) => {
3678 self.demand_coerce(idx, idx_t, index_ty);
3682 let mut err = self.type_error_struct(
3685 format!("cannot index a value of type `{}`",
3689 // Try to give some advice about indexing tuples.
3690 if let ty::TyTuple(..) = base_t.sty {
3691 let mut needs_note = true;
3692 // If the index is an integer, we can show the actual
3693 // fixed expression:
3694 if let hir::ExprLit(ref lit) = idx.node {
3695 if let ast::LitKind::Int(i,
3696 ast::LitIntType::Unsuffixed) = lit.node {
3697 let snip = tcx.sess.codemap().span_to_snippet(base.span);
3698 if let Ok(snip) = snip {
3699 err.span_suggestion(expr.span,
3700 "to access tuple elements, \
3701 use tuple indexing syntax \
3703 format!("{}.{}", snip, i));
3709 err.help("to access tuple elements, use tuple indexing \
3710 syntax (e.g. `tuple.0`)");
3722 // Finish resolving a path in a struct expression or pattern `S::A { .. }` if necessary.
3723 // The newly resolved definition is written into `type_relative_path_defs`.
3724 fn finish_resolving_struct_path(&self,
3727 node_id: ast::NodeId)
3731 hir::QPath::Resolved(ref maybe_qself, ref path) => {
3732 let opt_self_ty = maybe_qself.as_ref().map(|qself| self.to_ty(qself));
3733 let ty = AstConv::def_to_ty(self, opt_self_ty, path, true);
3736 hir::QPath::TypeRelative(ref qself, ref segment) => {
3737 let ty = self.to_ty(qself);
3739 let def = if let hir::TyPath(hir::QPath::Resolved(_, ref path)) = qself.node {
3744 let (ty, def) = AstConv::associated_path_def_to_ty(self, node_id, path_span,
3747 // Write back the new resolution.
3748 self.tables.borrow_mut().type_relative_path_defs.insert(node_id, def);
3755 // Resolve associated value path into a base type and associated constant or method definition.
3756 // The newly resolved definition is written into `type_relative_path_defs`.
3757 pub fn resolve_ty_and_def_ufcs<'b>(&self,
3758 qpath: &'b hir::QPath,
3759 node_id: ast::NodeId,
3761 -> (Def, Option<Ty<'tcx>>, &'b [hir::PathSegment])
3763 let (ty, item_segment) = match *qpath {
3764 hir::QPath::Resolved(ref opt_qself, ref path) => {
3766 opt_qself.as_ref().map(|qself| self.to_ty(qself)),
3767 &path.segments[..]);
3769 hir::QPath::TypeRelative(ref qself, ref segment) => {
3770 (self.to_ty(qself), segment)
3773 let item_name = item_segment.name;
3774 let def = match self.resolve_ufcs(span, item_name, ty, node_id) {
3777 let def = match error {
3778 method::MethodError::PrivateMatch(def) => def,
3781 if item_name != keywords::Invalid.name() {
3782 self.report_method_error(span, ty, item_name, None, error, None);
3788 // Write back the new resolution.
3789 self.tables.borrow_mut().type_relative_path_defs.insert(node_id, def);
3790 (def, Some(ty), slice::ref_slice(&**item_segment))
3793 pub fn check_decl_initializer(&self,
3794 local: &'gcx hir::Local,
3795 init: &'gcx hir::Expr) -> Ty<'tcx>
3797 let ref_bindings = local.pat.contains_ref_binding();
3799 let local_ty = self.local_ty(init.span, local.id);
3800 if let Some(m) = ref_bindings {
3801 // Somewhat subtle: if we have a `ref` binding in the pattern,
3802 // we want to avoid introducing coercions for the RHS. This is
3803 // both because it helps preserve sanity and, in the case of
3804 // ref mut, for soundness (issue #23116). In particular, in
3805 // the latter case, we need to be clear that the type of the
3806 // referent for the reference that results is *equal to* the
3807 // type of the lvalue it is referencing, and not some
3808 // supertype thereof.
3809 let init_ty = self.check_expr_with_lvalue_pref(init, LvaluePreference::from_mutbl(m));
3810 self.demand_eqtype(init.span, init_ty, local_ty);
3813 self.check_expr_coercable_to_type(init, local_ty)
3817 pub fn check_decl_local(&self, local: &'gcx hir::Local) {
3818 let t = self.local_ty(local.span, local.id);
3819 self.write_ty(local.id, t);
3821 if let Some(ref init) = local.init {
3822 let init_ty = self.check_decl_initializer(local, &init);
3823 if init_ty.references_error() {
3824 self.write_ty(local.id, init_ty);
3828 self.check_pat(&local.pat, t);
3829 let pat_ty = self.node_ty(local.pat.id);
3830 if pat_ty.references_error() {
3831 self.write_ty(local.id, pat_ty);
3835 pub fn check_stmt(&self, stmt: &'gcx hir::Stmt) {
3836 // Don't do all the complex logic below for DeclItem.
3838 hir::StmtDecl(ref decl, id) => {
3840 hir::DeclLocal(_) => {}
3841 hir::DeclItem(_) => {
3847 hir::StmtExpr(..) | hir::StmtSemi(..) => {}
3850 self.warn_if_unreachable(stmt.node.id(), stmt.span, "statement");
3852 // Hide the outer diverging and has_errors flags.
3853 let old_diverges = self.diverges.get();
3854 let old_has_errors = self.has_errors.get();
3855 self.diverges.set(Diverges::Maybe);
3856 self.has_errors.set(false);
3858 let (node_id, _span) = match stmt.node {
3859 hir::StmtDecl(ref decl, id) => {
3860 let span = match decl.node {
3861 hir::DeclLocal(ref l) => {
3862 self.check_decl_local(&l);
3865 hir::DeclItem(_) => {/* ignore for now */
3871 hir::StmtExpr(ref expr, id) => {
3872 // Check with expected type of ()
3873 self.check_expr_has_type(&expr, self.tcx.mk_nil());
3876 hir::StmtSemi(ref expr, id) => {
3877 self.check_expr(&expr);
3882 if self.has_errors.get() {
3883 self.write_error(node_id);
3885 self.write_nil(node_id);
3888 // Combine the diverging and has_error flags.
3889 self.diverges.set(self.diverges.get() | old_diverges);
3890 self.has_errors.set(self.has_errors.get() | old_has_errors);
3893 pub fn check_block_no_value(&self, blk: &'gcx hir::Block) {
3894 let unit = self.tcx.mk_nil();
3895 let ty = self.check_block_with_expected(blk, ExpectHasType(unit));
3897 // if the block produces a `!` value, that can always be
3898 // (effectively) coerced to unit.
3900 self.demand_suptype(blk.span, unit, ty);
3904 fn check_block_with_expected(&self,
3905 blk: &'gcx hir::Block,
3906 expected: Expectation<'tcx>) -> Ty<'tcx> {
3908 let mut fcx_ps = self.ps.borrow_mut();
3909 let unsafety_state = fcx_ps.recurse(blk);
3910 replace(&mut *fcx_ps, unsafety_state)
3913 // In some cases, blocks have just one exit, but other blocks
3914 // can be targeted by multiple breaks. This cannot happen in
3915 // normal Rust syntax today, but it can happen when we desugar
3916 // a `do catch { ... }` expression.
3920 // 'a: { if true { break 'a Err(()); } Ok(()) }
3922 // Here we would wind up with two coercions, one from
3923 // `Err(())` and the other from the tail expression
3924 // `Ok(())`. If the tail expression is omitted, that's a
3925 // "forced unit" -- unless the block diverges, in which
3926 // case we can ignore the tail expression (e.g., `'a: {
3927 // break 'a 22; }` would not force the type of the block
3929 let tail_expr = blk.expr.as_ref();
3930 let coerce_to_ty = expected.coercion_target_type(self, blk.span);
3931 let coerce = if blk.targeted_by_break {
3932 CoerceMany::new(coerce_to_ty)
3934 let tail_expr: &[P<hir::Expr>] = match tail_expr {
3935 Some(e) => ref_slice(e),
3938 CoerceMany::with_coercion_sites(coerce_to_ty, tail_expr)
3941 let ctxt = BreakableCtxt {
3942 coerce: Some(coerce),
3946 let (ctxt, ()) = self.with_breakable_ctxt(blk.id, ctxt, || {
3947 for s in &blk.stmts {
3951 // check the tail expression **without** holding the
3952 // `enclosing_breakables` lock below.
3953 let tail_expr_ty = tail_expr.map(|t| self.check_expr_with_expectation(t, expected));
3955 let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
3956 let mut ctxt = enclosing_breakables.find_breakable(blk.id);
3957 let mut coerce = ctxt.coerce.as_mut().unwrap();
3958 if let Some(tail_expr_ty) = tail_expr_ty {
3959 let tail_expr = tail_expr.unwrap();
3961 &self.misc(tail_expr.span),
3964 self.diverges.get());
3966 // Subtle: if there is no explicit tail expression,
3967 // that is typically equivalent to a tail expression
3968 // of `()` -- except if the block diverges. In that
3969 // case, there is no value supplied from the tail
3970 // expression (assuming there are no other breaks,
3971 // this implies that the type of the block will be
3973 if !self.diverges.get().always() {
3974 coerce.coerce_forced_unit(self, &self.misc(blk.span), &mut |err| {
3975 if let Some(expected_ty) = expected.only_has_type(self) {
3976 self.consider_hint_about_removing_semicolon(blk,
3985 let mut ty = ctxt.coerce.unwrap().complete(self);
3987 if self.has_errors.get() || ty.references_error() {
3988 ty = self.tcx.types.err
3991 self.write_ty(blk.id, ty);
3993 *self.ps.borrow_mut() = prev;
3997 /// A common error is to add an extra semicolon:
4000 /// fn foo() -> usize {
4005 /// This routine checks if the final statement in a block is an
4006 /// expression with an explicit semicolon whose type is compatible
4007 /// with `expected_ty`. If so, it suggests removing the semicolon.
4008 fn consider_hint_about_removing_semicolon(&self,
4009 blk: &'gcx hir::Block,
4010 expected_ty: Ty<'tcx>,
4011 err: &mut DiagnosticBuilder) {
4012 // Be helpful when the user wrote `{... expr;}` and
4013 // taking the `;` off is enough to fix the error.
4014 let last_stmt = match blk.stmts.last() {
4018 let last_expr = match last_stmt.node {
4019 hir::StmtSemi(ref e, _) => e,
4022 let last_expr_ty = self.expr_ty(last_expr);
4023 if self.can_sub_types(last_expr_ty, expected_ty).is_err() {
4026 let original_span = original_sp(last_stmt.span, blk.span);
4027 let span_semi = Span {
4028 lo: original_span.hi - BytePos(1),
4029 hi: original_span.hi,
4030 ctxt: original_span.ctxt,
4032 err.span_help(span_semi, "consider removing this semicolon:");
4035 // Instantiates the given path, which must refer to an item with the given
4036 // number of type parameters and type.
4037 pub fn instantiate_value_path(&self,
4038 segments: &[hir::PathSegment],
4039 opt_self_ty: Option<Ty<'tcx>>,
4042 node_id: ast::NodeId)
4044 debug!("instantiate_value_path(path={:?}, def={:?}, node_id={})",
4049 // We need to extract the type parameters supplied by the user in
4050 // the path `path`. Due to the current setup, this is a bit of a
4051 // tricky-process; the problem is that resolve only tells us the
4052 // end-point of the path resolution, and not the intermediate steps.
4053 // Luckily, we can (at least for now) deduce the intermediate steps
4054 // just from the end-point.
4056 // There are basically four cases to consider:
4058 // 1. Reference to a constructor of enum variant or struct:
4060 // struct Foo<T>(...)
4061 // enum E<T> { Foo(...) }
4063 // In these cases, the parameters are declared in the type
4066 // 2. Reference to a fn item or a free constant:
4070 // In this case, the path will again always have the form
4071 // `a::b::foo::<T>` where only the final segment should have
4072 // type parameters. However, in this case, those parameters are
4073 // declared on a value, and hence are in the `FnSpace`.
4075 // 3. Reference to a method or an associated constant:
4077 // impl<A> SomeStruct<A> {
4081 // Here we can have a path like
4082 // `a::b::SomeStruct::<A>::foo::<B>`, in which case parameters
4083 // may appear in two places. The penultimate segment,
4084 // `SomeStruct::<A>`, contains parameters in TypeSpace, and the
4085 // final segment, `foo::<B>` contains parameters in fn space.
4087 // 4. Reference to a local variable
4089 // Local variables can't have any type parameters.
4091 // The first step then is to categorize the segments appropriately.
4093 assert!(!segments.is_empty());
4095 let mut ufcs_associated = None;
4096 let mut type_segment = None;
4097 let mut fn_segment = None;
4099 // Case 1. Reference to a struct/variant constructor.
4100 Def::StructCtor(def_id, ..) |
4101 Def::VariantCtor(def_id, ..) => {
4102 // Everything but the final segment should have no
4103 // parameters at all.
4104 let mut generics = self.tcx.item_generics(def_id);
4105 if let Some(def_id) = generics.parent {
4106 // Variant and struct constructors use the
4107 // generics of their parent type definition.
4108 generics = self.tcx.item_generics(def_id);
4110 type_segment = Some((segments.last().unwrap(), generics));
4113 // Case 2. Reference to a top-level value.
4115 Def::Const(def_id) |
4116 Def::Static(def_id, _) => {
4117 fn_segment = Some((segments.last().unwrap(),
4118 self.tcx.item_generics(def_id)));
4121 // Case 3. Reference to a method or associated const.
4122 Def::Method(def_id) |
4123 Def::AssociatedConst(def_id) => {
4124 let container = self.tcx.associated_item(def_id).container;
4126 ty::TraitContainer(trait_did) => {
4127 callee::check_legal_trait_for_method_call(self.tcx, span, trait_did)
4129 ty::ImplContainer(_) => {}
4132 let generics = self.tcx.item_generics(def_id);
4133 if segments.len() >= 2 {
4134 let parent_generics = self.tcx.item_generics(generics.parent.unwrap());
4135 type_segment = Some((&segments[segments.len() - 2], parent_generics));
4137 // `<T>::assoc` will end up here, and so can `T::assoc`.
4138 let self_ty = opt_self_ty.expect("UFCS sugared assoc missing Self");
4139 ufcs_associated = Some((container, self_ty));
4141 fn_segment = Some((segments.last().unwrap(), generics));
4144 // Case 4. Local variable, no generics.
4145 Def::Local(..) | Def::Upvar(..) => {}
4147 _ => bug!("unexpected definition: {:?}", def),
4150 debug!("type_segment={:?} fn_segment={:?}", type_segment, fn_segment);
4152 // Now that we have categorized what space the parameters for each
4153 // segment belong to, let's sort out the parameters that the user
4154 // provided (if any) into their appropriate spaces. We'll also report
4155 // errors if type parameters are provided in an inappropriate place.
4156 let poly_segments = type_segment.is_some() as usize +
4157 fn_segment.is_some() as usize;
4158 AstConv::prohibit_type_params(self, &segments[..segments.len() - poly_segments]);
4161 Def::Local(def_id) | Def::Upvar(def_id, ..) => {
4162 let nid = self.tcx.hir.as_local_node_id(def_id).unwrap();
4163 let ty = self.local_ty(span, nid);
4164 let ty = self.normalize_associated_types_in(span, &ty);
4165 self.write_ty(node_id, ty);
4166 self.write_substs(node_id, ty::ItemSubsts {
4167 substs: self.tcx.intern_substs(&[])
4174 // Now we have to compare the types that the user *actually*
4175 // provided against the types that were *expected*. If the user
4176 // did not provide any types, then we want to substitute inference
4177 // variables. If the user provided some types, we may still need
4178 // to add defaults. If the user provided *too many* types, that's
4180 self.check_path_parameter_count(span, &mut type_segment);
4181 self.check_path_parameter_count(span, &mut fn_segment);
4183 let (fn_start, has_self) = match (type_segment, fn_segment) {
4184 (_, Some((_, generics))) => {
4185 (generics.parent_count(), generics.has_self)
4187 (Some((_, generics)), None) => {
4188 (generics.own_count(), generics.has_self)
4190 (None, None) => (0, false)
4192 let substs = Substs::for_item(self.tcx, def.def_id(), |def, _| {
4193 let mut i = def.index as usize;
4195 let segment = if i < fn_start {
4196 i -= has_self as usize;
4202 let lifetimes = match segment.map(|(s, _)| &s.parameters) {
4203 Some(&hir::AngleBracketedParameters(ref data)) => &data.lifetimes[..],
4204 Some(&hir::ParenthesizedParameters(_)) => bug!(),
4208 if let Some(lifetime) = lifetimes.get(i) {
4209 AstConv::ast_region_to_region(self, lifetime, Some(def))
4211 self.re_infer(span, Some(def)).unwrap()
4214 let mut i = def.index as usize;
4216 let segment = if i < fn_start {
4217 // Handle Self first, so we can adjust the index to match the AST.
4218 if has_self && i == 0 {
4219 return opt_self_ty.unwrap_or_else(|| {
4220 self.type_var_for_def(span, def, substs)
4223 i -= has_self as usize;
4229 let (types, infer_types) = match segment.map(|(s, _)| &s.parameters) {
4230 Some(&hir::AngleBracketedParameters(ref data)) => {
4231 (&data.types[..], data.infer_types)
4233 Some(&hir::ParenthesizedParameters(_)) => bug!(),
4234 None => (&[][..], true)
4237 // Skip over the lifetimes in the same segment.
4238 if let Some((_, generics)) = segment {
4239 i -= generics.regions.len();
4242 if let Some(ast_ty) = types.get(i) {
4243 // A provided type parameter.
4245 } else if !infer_types && def.has_default {
4246 // No type parameter provided, but a default exists.
4247 let default = self.tcx.item_type(def.def_id);
4250 default.subst_spanned(self.tcx, substs, Some(span))
4253 // No type parameters were provided, we can infer all.
4254 // This can also be reached in some error cases:
4255 // We prefer to use inference variables instead of
4256 // TyError to let type inference recover somewhat.
4257 self.type_var_for_def(span, def, substs)
4261 // The things we are substituting into the type should not contain
4262 // escaping late-bound regions, and nor should the base type scheme.
4263 let ty = self.tcx.item_type(def.def_id());
4264 assert!(!substs.has_escaping_regions());
4265 assert!(!ty.has_escaping_regions());
4267 // Add all the obligations that are required, substituting and
4268 // normalized appropriately.
4269 let bounds = self.instantiate_bounds(span, def.def_id(), &substs);
4270 self.add_obligations_for_parameters(
4271 traits::ObligationCause::new(span, self.body_id, traits::ItemObligation(def.def_id())),
4274 // Substitute the values for the type parameters into the type of
4275 // the referenced item.
4276 let ty_substituted = self.instantiate_type_scheme(span, &substs, &ty);
4278 if let Some((ty::ImplContainer(impl_def_id), self_ty)) = ufcs_associated {
4279 // In the case of `Foo<T>::method` and `<Foo<T>>::method`, if `method`
4280 // is inherent, there is no `Self` parameter, instead, the impl needs
4281 // type parameters, which we can infer by unifying the provided `Self`
4282 // with the substituted impl type.
4283 let ty = self.tcx.item_type(impl_def_id);
4285 let impl_ty = self.instantiate_type_scheme(span, &substs, &ty);
4286 match self.sub_types(false, &self.misc(span), self_ty, impl_ty) {
4287 Ok(ok) => self.register_infer_ok_obligations(ok),
4290 "instantiate_value_path: (UFCS) {:?} was a subtype of {:?} but now is not?",
4297 debug!("instantiate_value_path: type of {:?} is {:?}",
4300 self.write_substs(node_id, ty::ItemSubsts {
4306 /// Report errors if the provided parameters are too few or too many.
4307 fn check_path_parameter_count(&self,
4309 segment: &mut Option<(&hir::PathSegment, &ty::Generics)>) {
4310 let (lifetimes, types, infer_types, bindings) = {
4311 match segment.map(|(s, _)| &s.parameters) {
4312 Some(&hir::AngleBracketedParameters(ref data)) => {
4313 (&data.lifetimes[..], &data.types[..], data.infer_types, &data.bindings[..])
4315 Some(&hir::ParenthesizedParameters(_)) => {
4316 span_bug!(span, "parenthesized parameters cannot appear in ExprPath");
4318 None => (&[][..], &[][..], true, &[][..])
4322 let count_lifetime_params = |n| {
4323 format!("{} lifetime parameter{}", n, if n == 1 { "" } else { "s" })
4325 let count_type_params = |n| {
4326 format!("{} type parameter{}", n, if n == 1 { "" } else { "s" })
4329 // Check provided lifetime parameters.
4330 let lifetime_defs = segment.map_or(&[][..], |(_, generics)| &generics.regions);
4331 if lifetimes.len() > lifetime_defs.len() {
4332 let expected_text = count_lifetime_params(lifetime_defs.len());
4333 let actual_text = count_lifetime_params(lifetimes.len());
4334 struct_span_err!(self.tcx.sess, span, E0088,
4335 "too many lifetime parameters provided: \
4336 expected at most {}, found {}",
4337 expected_text, actual_text)
4338 .span_label(span, &format!("expected {}", expected_text))
4340 } else if lifetimes.len() > 0 && lifetimes.len() < lifetime_defs.len() {
4341 let expected_text = count_lifetime_params(lifetime_defs.len());
4342 let actual_text = count_lifetime_params(lifetimes.len());
4343 struct_span_err!(self.tcx.sess, span, E0090,
4344 "too few lifetime parameters provided: \
4345 expected {}, found {}",
4346 expected_text, actual_text)
4347 .span_label(span, &format!("expected {}", expected_text))
4351 // The case where there is not enough lifetime parameters is not checked,
4352 // because this is not possible - a function never takes lifetime parameters.
4353 // See discussion for Pull Request 36208.
4355 // Check provided type parameters.
4356 let type_defs = segment.map_or(&[][..], |(_, generics)| {
4357 if generics.parent.is_none() {
4358 &generics.types[generics.has_self as usize..]
4363 let required_len = type_defs.iter().take_while(|d| !d.has_default).count();
4364 if types.len() > type_defs.len() {
4365 let span = types[type_defs.len()].span;
4366 let expected_text = count_type_params(type_defs.len());
4367 let actual_text = count_type_params(types.len());
4368 struct_span_err!(self.tcx.sess, span, E0087,
4369 "too many type parameters provided: \
4370 expected at most {}, found {}",
4371 expected_text, actual_text)
4372 .span_label(span, &format!("expected {}", expected_text))
4375 // To prevent derived errors to accumulate due to extra
4376 // type parameters, we force instantiate_value_path to
4377 // use inference variables instead of the provided types.
4379 } else if !infer_types && types.len() < required_len {
4380 let expected_text = count_type_params(required_len);
4381 let actual_text = count_type_params(types.len());
4382 struct_span_err!(self.tcx.sess, span, E0089,
4383 "too few type parameters provided: \
4384 expected {}, found {}",
4385 expected_text, actual_text)
4386 .span_label(span, &format!("expected {}", expected_text))
4390 if !bindings.is_empty() {
4391 span_err!(self.tcx.sess, bindings[0].span, E0182,
4392 "unexpected binding of associated item in expression path \
4393 (only allowed in type paths)");
4397 fn structurally_resolve_type_or_else<F>(&self, sp: Span, ty: Ty<'tcx>, f: F)
4399 where F: Fn() -> Ty<'tcx>
4401 let mut ty = self.resolve_type_vars_with_obligations(ty);
4404 let alternative = f();
4407 if alternative.is_ty_var() || alternative.references_error() {
4408 if !self.is_tainted_by_errors() {
4409 self.type_error_message(sp, |_actual| {
4410 "the type of this value must be known in this context".to_string()
4413 self.demand_suptype(sp, self.tcx.types.err, ty);
4414 ty = self.tcx.types.err;
4416 self.demand_suptype(sp, alternative, ty);
4424 // Resolves `typ` by a single level if `typ` is a type variable. If no
4425 // resolution is possible, then an error is reported.
4426 pub fn structurally_resolved_type(&self, sp: Span, ty: Ty<'tcx>) -> Ty<'tcx> {
4427 self.structurally_resolve_type_or_else(sp, ty, || {
4432 fn with_breakable_ctxt<F: FnOnce() -> R, R>(&self, id: ast::NodeId,
4433 ctxt: BreakableCtxt<'gcx, 'tcx>, f: F)
4434 -> (BreakableCtxt<'gcx, 'tcx>, R) {
4437 let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
4438 index = enclosing_breakables.stack.len();
4439 enclosing_breakables.by_id.insert(id, index);
4440 enclosing_breakables.stack.push(ctxt);
4444 let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
4445 debug_assert!(enclosing_breakables.stack.len() == index + 1);
4446 enclosing_breakables.by_id.remove(&id).expect("missing breakable context");
4447 enclosing_breakables.stack.pop().expect("missing breakable context")
4453 pub fn check_bounds_are_used<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
4454 generics: &hir::Generics,
4456 debug!("check_bounds_are_used(n_tps={}, ty={:?})",
4457 generics.ty_params.len(), ty);
4459 // make a vector of booleans initially false, set to true when used
4460 if generics.ty_params.is_empty() { return; }
4461 let mut tps_used = vec![false; generics.ty_params.len()];
4463 for leaf_ty in ty.walk() {
4464 if let ty::TyParam(ParamTy {idx, ..}) = leaf_ty.sty {
4465 debug!("Found use of ty param num {}", idx);
4466 tps_used[idx as usize - generics.lifetimes.len()] = true;
4470 for (&used, param) in tps_used.iter().zip(&generics.ty_params) {
4472 struct_span_err!(tcx.sess, param.span, E0091,
4473 "type parameter `{}` is unused",
4475 .span_label(param.span, &format!("unused type parameter"))