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Commit | Line | Data |
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3c0e092e XL |
1 | use crate::infer::{InferCtxt, InferOk}; |
2 | use crate::traits; | |
5e7ed085 FG |
3 | use hir::def_id::{DefId, LocalDefId}; |
4 | use hir::{HirId, OpaqueTyOrigin}; | |
3c0e092e | 5 | use rustc_data_structures::sync::Lrc; |
94222f64 XL |
6 | use rustc_data_structures::vec_map::VecMap; |
7 | use rustc_hir as hir; | |
923072b8 | 8 | use rustc_middle::traits::{ObligationCause, ObligationCauseCode}; |
3c0e092e XL |
9 | use rustc_middle::ty::fold::BottomUpFolder; |
10 | use rustc_middle::ty::subst::{GenericArgKind, Subst}; | |
5e7ed085 | 11 | use rustc_middle::ty::{ |
923072b8 | 12 | self, OpaqueHiddenType, OpaqueTypeKey, Ty, TyCtxt, TypeFoldable, TypeSuperFoldable, TypeVisitor, |
5e7ed085 | 13 | }; |
94222f64 XL |
14 | use rustc_span::Span; |
15 | ||
3c0e092e XL |
16 | use std::ops::ControlFlow; |
17 | ||
94222f64 XL |
18 | pub type OpaqueTypeMap<'tcx> = VecMap<OpaqueTypeKey<'tcx>, OpaqueTypeDecl<'tcx>>; |
19 | ||
5e7ed085 FG |
20 | mod table; |
21 | ||
22 | pub use table::{OpaqueTypeStorage, OpaqueTypeTable}; | |
23 | ||
24 | use super::type_variable::{TypeVariableOrigin, TypeVariableOriginKind}; | |
25 | use super::InferResult; | |
26 | ||
94222f64 XL |
27 | /// Information about the opaque types whose values we |
28 | /// are inferring in this function (these are the `impl Trait` that | |
29 | /// appear in the return type). | |
5e7ed085 | 30 | #[derive(Clone, Debug)] |
94222f64 | 31 | pub struct OpaqueTypeDecl<'tcx> { |
5e7ed085 FG |
32 | /// The hidden types that have been inferred for this opaque type. |
33 | /// There can be multiple, but they are all `lub`ed together at the end | |
34 | /// to obtain the canonical hidden type. | |
35 | pub hidden_type: OpaqueHiddenType<'tcx>, | |
94222f64 XL |
36 | |
37 | /// The origin of the opaque type. | |
38 | pub origin: hir::OpaqueTyOrigin, | |
39 | } | |
3c0e092e XL |
40 | |
41 | impl<'a, 'tcx> InferCtxt<'a, 'tcx> { | |
5e7ed085 FG |
42 | /// This is a backwards compatibility hack to prevent breaking changes from |
43 | /// lazy TAIT around RPIT handling. | |
44 | pub fn replace_opaque_types_with_inference_vars<T: TypeFoldable<'tcx>>( | |
3c0e092e | 45 | &self, |
3c0e092e | 46 | value: T, |
5e7ed085 FG |
47 | body_id: HirId, |
48 | span: Span, | |
923072b8 | 49 | code: ObligationCauseCode<'tcx>, |
5e7ed085 | 50 | param_env: ty::ParamEnv<'tcx>, |
3c0e092e | 51 | ) -> InferOk<'tcx, T> { |
5e7ed085 FG |
52 | if !value.has_opaque_types() { |
53 | return InferOk { value, obligations: vec![] }; | |
54 | } | |
55 | let mut obligations = vec![]; | |
56 | let value = value.fold_with(&mut ty::fold::BottomUpFolder { | |
57 | tcx: self.tcx, | |
58 | lt_op: |lt| lt, | |
59 | ct_op: |ct| ct, | |
60 | ty_op: |ty| match *ty.kind() { | |
61 | // Closures can't create hidden types for opaque types of their parent, as they | |
62 | // do not have all the outlives information available. Also `type_of` looks for | |
63 | // hidden types in the owner (so the closure's parent), so it would not find these | |
64 | // definitions. | |
65 | ty::Opaque(def_id, _substs) | |
66 | if matches!( | |
67 | self.opaque_type_origin(def_id, span), | |
68 | Some(OpaqueTyOrigin::FnReturn(..)) | |
69 | ) => | |
70 | { | |
71 | let span = if span.is_dummy() { self.tcx.def_span(def_id) } else { span }; | |
923072b8 FG |
72 | let cause = ObligationCause::new(span, body_id, code.clone()); |
73 | // FIXME(compiler-errors): We probably should add a new TypeVariableOriginKind | |
74 | // for opaque types, and then use that kind to fix the spans for type errors | |
75 | // that we see later on. | |
5e7ed085 FG |
76 | let ty_var = self.next_ty_var(TypeVariableOrigin { |
77 | kind: TypeVariableOriginKind::TypeInference, | |
923072b8 | 78 | span, |
5e7ed085 FG |
79 | }); |
80 | obligations.extend( | |
81 | self.handle_opaque_type(ty, ty_var, true, &cause, param_env) | |
82 | .unwrap() | |
83 | .obligations, | |
84 | ); | |
85 | ty_var | |
86 | } | |
87 | _ => ty, | |
88 | }, | |
89 | }); | |
90 | InferOk { value, obligations } | |
91 | } | |
92 | ||
93 | pub fn handle_opaque_type( | |
94 | &self, | |
95 | a: Ty<'tcx>, | |
96 | b: Ty<'tcx>, | |
97 | a_is_expected: bool, | |
98 | cause: &ObligationCause<'tcx>, | |
99 | param_env: ty::ParamEnv<'tcx>, | |
100 | ) -> InferResult<'tcx, ()> { | |
101 | if a.references_error() || b.references_error() { | |
102 | return Ok(InferOk { value: (), obligations: vec![] }); | |
103 | } | |
104 | let (a, b) = if a_is_expected { (a, b) } else { (b, a) }; | |
105 | let process = |a: Ty<'tcx>, b: Ty<'tcx>| match *a.kind() { | |
04454e1e | 106 | ty::Opaque(def_id, substs) if def_id.is_local() => { |
5e7ed085 FG |
107 | let origin = if self.defining_use_anchor.is_some() { |
108 | // Check that this is `impl Trait` type is | |
109 | // declared by `parent_def_id` -- i.e., one whose | |
110 | // value we are inferring. At present, this is | |
111 | // always true during the first phase of | |
112 | // type-check, but not always true later on during | |
113 | // NLL. Once we support named opaque types more fully, | |
114 | // this same scenario will be able to arise during all phases. | |
115 | // | |
116 | // Here is an example using type alias `impl Trait` | |
117 | // that indicates the distinction we are checking for: | |
118 | // | |
119 | // ```rust | |
120 | // mod a { | |
121 | // pub type Foo = impl Iterator; | |
122 | // pub fn make_foo() -> Foo { .. } | |
123 | // } | |
124 | // | |
125 | // mod b { | |
126 | // fn foo() -> a::Foo { a::make_foo() } | |
127 | // } | |
128 | // ``` | |
129 | // | |
130 | // Here, the return type of `foo` references an | |
131 | // `Opaque` indeed, but not one whose value is | |
132 | // presently being inferred. You can get into a | |
133 | // similar situation with closure return types | |
134 | // today: | |
135 | // | |
136 | // ```rust | |
137 | // fn foo() -> impl Iterator { .. } | |
138 | // fn bar() { | |
139 | // let x = || foo(); // returns the Opaque assoc with `foo` | |
140 | // } | |
141 | // ``` | |
142 | self.opaque_type_origin(def_id, cause.span)? | |
143 | } else { | |
144 | self.opaque_ty_origin_unchecked(def_id, cause.span) | |
145 | }; | |
146 | if let ty::Opaque(did2, _) = *b.kind() { | |
147 | // We could accept this, but there are various ways to handle this situation, and we don't | |
148 | // want to make a decision on it right now. Likely this case is so super rare anyway, that | |
149 | // no one encounters it in practice. | |
150 | // It does occur however in `fn fut() -> impl Future<Output = i32> { async { 42 } }`, | |
151 | // where it is of no concern, so we only check for TAITs. | |
152 | if let Some(OpaqueTyOrigin::TyAlias) = self.opaque_type_origin(did2, cause.span) | |
153 | { | |
154 | self.tcx | |
155 | .sess | |
156 | .struct_span_err( | |
157 | cause.span, | |
158 | "opaque type's hidden type cannot be another opaque type from the same scope", | |
159 | ) | |
160 | .span_label(cause.span, "one of the two opaque types used here has to be outside its defining scope") | |
161 | .span_note( | |
162 | self.tcx.def_span(def_id), | |
163 | "opaque type whose hidden type is being assigned", | |
164 | ) | |
165 | .span_note( | |
166 | self.tcx.def_span(did2), | |
167 | "opaque type being used as hidden type", | |
168 | ) | |
169 | .emit(); | |
170 | } | |
171 | } | |
172 | Some(self.register_hidden_type( | |
173 | OpaqueTypeKey { def_id, substs }, | |
174 | cause.clone(), | |
175 | param_env, | |
176 | b, | |
177 | origin, | |
178 | )) | |
179 | } | |
180 | _ => None, | |
181 | }; | |
182 | if let Some(res) = process(a, b) { | |
183 | res | |
184 | } else if let Some(res) = process(b, a) { | |
185 | res | |
186 | } else { | |
187 | // Rerun equality check, but this time error out due to | |
188 | // different types. | |
189 | match self.at(cause, param_env).define_opaque_types(false).eq(a, b) { | |
190 | Ok(_) => span_bug!( | |
191 | cause.span, | |
192 | "opaque types are never equal to anything but themselves: {:#?}", | |
193 | (a.kind(), b.kind()) | |
194 | ), | |
195 | Err(e) => Err(e), | |
196 | } | |
197 | } | |
3c0e092e XL |
198 | } |
199 | ||
200 | /// Given the map `opaque_types` containing the opaque | |
201 | /// `impl Trait` types whose underlying, hidden types are being | |
202 | /// inferred, this method adds constraints to the regions | |
203 | /// appearing in those underlying hidden types to ensure that they | |
204 | /// at least do not refer to random scopes within the current | |
205 | /// function. These constraints are not (quite) sufficient to | |
206 | /// guarantee that the regions are actually legal values; that | |
207 | /// final condition is imposed after region inference is done. | |
208 | /// | |
209 | /// # The Problem | |
210 | /// | |
211 | /// Let's work through an example to explain how it works. Assume | |
212 | /// the current function is as follows: | |
213 | /// | |
214 | /// ```text | |
215 | /// fn foo<'a, 'b>(..) -> (impl Bar<'a>, impl Bar<'b>) | |
216 | /// ``` | |
217 | /// | |
218 | /// Here, we have two `impl Trait` types whose values are being | |
219 | /// inferred (the `impl Bar<'a>` and the `impl | |
220 | /// Bar<'b>`). Conceptually, this is sugar for a setup where we | |
221 | /// define underlying opaque types (`Foo1`, `Foo2`) and then, in | |
222 | /// the return type of `foo`, we *reference* those definitions: | |
223 | /// | |
224 | /// ```text | |
225 | /// type Foo1<'x> = impl Bar<'x>; | |
226 | /// type Foo2<'x> = impl Bar<'x>; | |
227 | /// fn foo<'a, 'b>(..) -> (Foo1<'a>, Foo2<'b>) { .. } | |
228 | /// // ^^^^ ^^ | |
229 | /// // | | | |
230 | /// // | substs | |
231 | /// // def_id | |
232 | /// ``` | |
233 | /// | |
234 | /// As indicating in the comments above, each of those references | |
235 | /// is (in the compiler) basically a substitution (`substs`) | |
236 | /// applied to the type of a suitable `def_id` (which identifies | |
237 | /// `Foo1` or `Foo2`). | |
238 | /// | |
239 | /// Now, at this point in compilation, what we have done is to | |
240 | /// replace each of the references (`Foo1<'a>`, `Foo2<'b>`) with | |
241 | /// fresh inference variables C1 and C2. We wish to use the values | |
242 | /// of these variables to infer the underlying types of `Foo1` and | |
243 | /// `Foo2`. That is, this gives rise to higher-order (pattern) unification | |
244 | /// constraints like: | |
245 | /// | |
246 | /// ```text | |
247 | /// for<'a> (Foo1<'a> = C1) | |
248 | /// for<'b> (Foo1<'b> = C2) | |
249 | /// ``` | |
250 | /// | |
251 | /// For these equation to be satisfiable, the types `C1` and `C2` | |
252 | /// can only refer to a limited set of regions. For example, `C1` | |
253 | /// can only refer to `'static` and `'a`, and `C2` can only refer | |
254 | /// to `'static` and `'b`. The job of this function is to impose that | |
255 | /// constraint. | |
256 | /// | |
257 | /// Up to this point, C1 and C2 are basically just random type | |
258 | /// inference variables, and hence they may contain arbitrary | |
259 | /// regions. In fact, it is fairly likely that they do! Consider | |
260 | /// this possible definition of `foo`: | |
261 | /// | |
262 | /// ```text | |
263 | /// fn foo<'a, 'b>(x: &'a i32, y: &'b i32) -> (impl Bar<'a>, impl Bar<'b>) { | |
264 | /// (&*x, &*y) | |
265 | /// } | |
266 | /// ``` | |
267 | /// | |
268 | /// Here, the values for the concrete types of the two impl | |
269 | /// traits will include inference variables: | |
270 | /// | |
271 | /// ```text | |
272 | /// &'0 i32 | |
273 | /// &'1 i32 | |
274 | /// ``` | |
275 | /// | |
276 | /// Ordinarily, the subtyping rules would ensure that these are | |
277 | /// sufficiently large. But since `impl Bar<'a>` isn't a specific | |
278 | /// type per se, we don't get such constraints by default. This | |
279 | /// is where this function comes into play. It adds extra | |
280 | /// constraints to ensure that all the regions which appear in the | |
281 | /// inferred type are regions that could validly appear. | |
282 | /// | |
283 | /// This is actually a bit of a tricky constraint in general. We | |
284 | /// want to say that each variable (e.g., `'0`) can only take on | |
285 | /// values that were supplied as arguments to the opaque type | |
286 | /// (e.g., `'a` for `Foo1<'a>`) or `'static`, which is always in | |
287 | /// scope. We don't have a constraint quite of this kind in the current | |
288 | /// region checker. | |
289 | /// | |
290 | /// # The Solution | |
291 | /// | |
292 | /// We generally prefer to make `<=` constraints, since they | |
293 | /// integrate best into the region solver. To do that, we find the | |
294 | /// "minimum" of all the arguments that appear in the substs: that | |
295 | /// is, some region which is less than all the others. In the case | |
296 | /// of `Foo1<'a>`, that would be `'a` (it's the only choice, after | |
297 | /// all). Then we apply that as a least bound to the variables | |
298 | /// (e.g., `'a <= '0`). | |
299 | /// | |
300 | /// In some cases, there is no minimum. Consider this example: | |
301 | /// | |
302 | /// ```text | |
303 | /// fn baz<'a, 'b>() -> impl Trait<'a, 'b> { ... } | |
304 | /// ``` | |
305 | /// | |
306 | /// Here we would report a more complex "in constraint", like `'r | |
307 | /// in ['a, 'b, 'static]` (where `'r` is some region appearing in | |
308 | /// the hidden type). | |
309 | /// | |
310 | /// # Constrain regions, not the hidden concrete type | |
311 | /// | |
312 | /// Note that generating constraints on each region `Rc` is *not* | |
5e7ed085 | 313 | /// the same as generating an outlives constraint on `Tc` itself. |
3c0e092e XL |
314 | /// For example, if we had a function like this: |
315 | /// | |
04454e1e FG |
316 | /// ``` |
317 | /// # #![feature(type_alias_impl_trait)] | |
318 | /// # fn main() {} | |
319 | /// # trait Foo<'a> {} | |
320 | /// # impl<'a, T> Foo<'a> for (&'a u32, T) {} | |
3c0e092e XL |
321 | /// fn foo<'a, T>(x: &'a u32, y: T) -> impl Foo<'a> { |
322 | /// (x, y) | |
323 | /// } | |
324 | /// | |
325 | /// // Equivalent to: | |
04454e1e | 326 | /// # mod dummy { use super::*; |
3c0e092e | 327 | /// type FooReturn<'a, T> = impl Foo<'a>; |
04454e1e FG |
328 | /// fn foo<'a, T>(x: &'a u32, y: T) -> FooReturn<'a, T> { |
329 | /// (x, y) | |
330 | /// } | |
331 | /// # } | |
3c0e092e XL |
332 | /// ``` |
333 | /// | |
334 | /// then the hidden type `Tc` would be `(&'0 u32, T)` (where `'0` | |
335 | /// is an inference variable). If we generated a constraint that | |
336 | /// `Tc: 'a`, then this would incorrectly require that `T: 'a` -- | |
337 | /// but this is not necessary, because the opaque type we | |
338 | /// create will be allowed to reference `T`. So we only generate a | |
339 | /// constraint that `'0: 'a`. | |
3c0e092e | 340 | #[instrument(level = "debug", skip(self))] |
5e7ed085 | 341 | pub fn register_member_constraints( |
3c0e092e | 342 | &self, |
5e7ed085 | 343 | param_env: ty::ParamEnv<'tcx>, |
3c0e092e | 344 | opaque_type_key: OpaqueTypeKey<'tcx>, |
5e7ed085 FG |
345 | concrete_ty: Ty<'tcx>, |
346 | span: Span, | |
3c0e092e XL |
347 | ) { |
348 | let def_id = opaque_type_key.def_id; | |
349 | ||
350 | let tcx = self.tcx; | |
351 | ||
5e7ed085 | 352 | let concrete_ty = self.resolve_vars_if_possible(concrete_ty); |
3c0e092e XL |
353 | |
354 | debug!(?concrete_ty); | |
355 | ||
5e7ed085 | 356 | let first_own_region = match self.opaque_ty_origin_unchecked(def_id, span) { |
a2a8927a | 357 | hir::OpaqueTyOrigin::FnReturn(..) | hir::OpaqueTyOrigin::AsyncFn(..) => { |
3c0e092e XL |
358 | // We lower |
359 | // | |
360 | // fn foo<'l0..'ln>() -> impl Trait<'l0..'lm> | |
361 | // | |
362 | // into | |
363 | // | |
364 | // type foo::<'p0..'pn>::Foo<'q0..'qm> | |
365 | // fn foo<l0..'ln>() -> foo::<'static..'static>::Foo<'l0..'lm>. | |
366 | // | |
367 | // For these types we only iterate over `'l0..lm` below. | |
368 | tcx.generics_of(def_id).parent_count | |
369 | } | |
370 | // These opaque type inherit all lifetime parameters from their | |
371 | // parent, so we have to check them all. | |
372 | hir::OpaqueTyOrigin::TyAlias => 0, | |
373 | }; | |
374 | ||
375 | // For a case like `impl Foo<'a, 'b>`, we would generate a constraint | |
376 | // `'r in ['a, 'b, 'static]` for each region `'r` that appears in the | |
377 | // hidden type (i.e., it must be equal to `'a`, `'b`, or `'static`). | |
378 | // | |
379 | // `conflict1` and `conflict2` are the two region bounds that we | |
380 | // detected which were unrelated. They are used for diagnostics. | |
381 | ||
382 | // Create the set of choice regions: each region in the hidden | |
383 | // type can be equal to any of the region parameters of the | |
384 | // opaque type definition. | |
385 | let choice_regions: Lrc<Vec<ty::Region<'tcx>>> = Lrc::new( | |
386 | opaque_type_key.substs[first_own_region..] | |
387 | .iter() | |
388 | .filter_map(|arg| match arg.unpack() { | |
389 | GenericArgKind::Lifetime(r) => Some(r), | |
390 | GenericArgKind::Type(_) | GenericArgKind::Const(_) => None, | |
391 | }) | |
392 | .chain(std::iter::once(self.tcx.lifetimes.re_static)) | |
393 | .collect(), | |
394 | ); | |
395 | ||
396 | concrete_ty.visit_with(&mut ConstrainOpaqueTypeRegionVisitor { | |
3c0e092e XL |
397 | op: |r| { |
398 | self.member_constraint( | |
399 | opaque_type_key.def_id, | |
5e7ed085 | 400 | span, |
3c0e092e XL |
401 | concrete_ty, |
402 | r, | |
403 | &choice_regions, | |
404 | ) | |
405 | }, | |
406 | }); | |
407 | } | |
5099ac24 | 408 | |
5e7ed085 FG |
409 | #[instrument(skip(self), level = "trace")] |
410 | pub fn opaque_type_origin(&self, opaque_def_id: DefId, span: Span) -> Option<OpaqueTyOrigin> { | |
411 | let def_id = opaque_def_id.as_local()?; | |
412 | let opaque_hir_id = self.tcx.hir().local_def_id_to_hir_id(def_id); | |
5099ac24 | 413 | let parent_def_id = self.defining_use_anchor?; |
5e7ed085 FG |
414 | let item_kind = &self.tcx.hir().expect_item(def_id).kind; |
415 | ||
5099ac24 FG |
416 | let hir::ItemKind::OpaqueTy(hir::OpaqueTy { origin, .. }) = item_kind else { |
417 | span_bug!( | |
5e7ed085 FG |
418 | span, |
419 | "weird opaque type: {:#?}, {:#?}", | |
420 | opaque_def_id, | |
5099ac24 FG |
421 | item_kind |
422 | ) | |
423 | }; | |
424 | let in_definition_scope = match *origin { | |
425 | // Async `impl Trait` | |
426 | hir::OpaqueTyOrigin::AsyncFn(parent) => parent == parent_def_id, | |
427 | // Anonymous `impl Trait` | |
428 | hir::OpaqueTyOrigin::FnReturn(parent) => parent == parent_def_id, | |
429 | // Named `type Foo = impl Bar;` | |
430 | hir::OpaqueTyOrigin::TyAlias => { | |
5e7ed085 | 431 | may_define_opaque_type(self.tcx, parent_def_id, opaque_hir_id) |
5099ac24 FG |
432 | } |
433 | }; | |
5e7ed085 | 434 | trace!(?origin); |
5099ac24 FG |
435 | in_definition_scope.then_some(*origin) |
436 | } | |
5e7ed085 FG |
437 | |
438 | #[instrument(skip(self), level = "trace")] | |
439 | fn opaque_ty_origin_unchecked(&self, opaque_def_id: DefId, span: Span) -> OpaqueTyOrigin { | |
440 | let def_id = opaque_def_id.as_local().unwrap(); | |
441 | let origin = match self.tcx.hir().expect_item(def_id).kind { | |
442 | hir::ItemKind::OpaqueTy(hir::OpaqueTy { origin, .. }) => origin, | |
443 | ref itemkind => { | |
444 | span_bug!(span, "weird opaque type: {:?}, {:#?}", opaque_def_id, itemkind) | |
445 | } | |
446 | }; | |
447 | trace!(?origin); | |
448 | origin | |
449 | } | |
3c0e092e XL |
450 | } |
451 | ||
452 | // Visitor that requires that (almost) all regions in the type visited outlive | |
453 | // `least_region`. We cannot use `push_outlives_components` because regions in | |
454 | // closure signatures are not included in their outlives components. We need to | |
455 | // ensure all regions outlive the given bound so that we don't end up with, | |
456 | // say, `ReVar` appearing in a return type and causing ICEs when other | |
457 | // functions end up with region constraints involving regions from other | |
458 | // functions. | |
459 | // | |
460 | // We also cannot use `for_each_free_region` because for closures it includes | |
461 | // the regions parameters from the enclosing item. | |
462 | // | |
463 | // We ignore any type parameters because impl trait values are assumed to | |
464 | // capture all the in-scope type parameters. | |
5099ac24 | 465 | struct ConstrainOpaqueTypeRegionVisitor<OP> { |
3c0e092e XL |
466 | op: OP, |
467 | } | |
468 | ||
5099ac24 | 469 | impl<'tcx, OP> TypeVisitor<'tcx> for ConstrainOpaqueTypeRegionVisitor<OP> |
3c0e092e XL |
470 | where |
471 | OP: FnMut(ty::Region<'tcx>), | |
472 | { | |
3c0e092e XL |
473 | fn visit_binder<T: TypeFoldable<'tcx>>( |
474 | &mut self, | |
475 | t: &ty::Binder<'tcx, T>, | |
476 | ) -> ControlFlow<Self::BreakTy> { | |
923072b8 | 477 | t.super_visit_with(self); |
3c0e092e XL |
478 | ControlFlow::CONTINUE |
479 | } | |
480 | ||
481 | fn visit_region(&mut self, r: ty::Region<'tcx>) -> ControlFlow<Self::BreakTy> { | |
482 | match *r { | |
483 | // ignore bound regions, keep visiting | |
484 | ty::ReLateBound(_, _) => ControlFlow::CONTINUE, | |
485 | _ => { | |
486 | (self.op)(r); | |
487 | ControlFlow::CONTINUE | |
488 | } | |
489 | } | |
490 | } | |
491 | ||
492 | fn visit_ty(&mut self, ty: Ty<'tcx>) -> ControlFlow<Self::BreakTy> { | |
493 | // We're only interested in types involving regions | |
5099ac24 | 494 | if !ty.flags().intersects(ty::TypeFlags::HAS_FREE_REGIONS) { |
3c0e092e XL |
495 | return ControlFlow::CONTINUE; |
496 | } | |
497 | ||
498 | match ty.kind() { | |
499 | ty::Closure(_, ref substs) => { | |
500 | // Skip lifetime parameters of the enclosing item(s) | |
501 | ||
502 | substs.as_closure().tupled_upvars_ty().visit_with(self); | |
503 | substs.as_closure().sig_as_fn_ptr_ty().visit_with(self); | |
504 | } | |
505 | ||
506 | ty::Generator(_, ref substs, _) => { | |
507 | // Skip lifetime parameters of the enclosing item(s) | |
508 | // Also skip the witness type, because that has no free regions. | |
509 | ||
510 | substs.as_generator().tupled_upvars_ty().visit_with(self); | |
511 | substs.as_generator().return_ty().visit_with(self); | |
512 | substs.as_generator().yield_ty().visit_with(self); | |
513 | substs.as_generator().resume_ty().visit_with(self); | |
514 | } | |
515 | _ => { | |
516 | ty.super_visit_with(self); | |
517 | } | |
518 | } | |
519 | ||
520 | ControlFlow::CONTINUE | |
521 | } | |
522 | } | |
523 | ||
5e7ed085 FG |
524 | pub enum UseKind { |
525 | DefiningUse, | |
526 | OpaqueUse, | |
3c0e092e XL |
527 | } |
528 | ||
5e7ed085 FG |
529 | impl UseKind { |
530 | pub fn is_defining(self) -> bool { | |
531 | match self { | |
532 | UseKind::DefiningUse => true, | |
533 | UseKind::OpaqueUse => false, | |
534 | } | |
3c0e092e | 535 | } |
5e7ed085 | 536 | } |
3c0e092e | 537 | |
5e7ed085 | 538 | impl<'a, 'tcx> InferCtxt<'a, 'tcx> { |
3c0e092e | 539 | #[instrument(skip(self), level = "debug")] |
5e7ed085 FG |
540 | pub fn register_hidden_type( |
541 | &self, | |
3c0e092e | 542 | opaque_type_key: OpaqueTypeKey<'tcx>, |
5e7ed085 FG |
543 | cause: ObligationCause<'tcx>, |
544 | param_env: ty::ParamEnv<'tcx>, | |
545 | hidden_ty: Ty<'tcx>, | |
3c0e092e | 546 | origin: hir::OpaqueTyOrigin, |
5e7ed085 FG |
547 | ) -> InferResult<'tcx, ()> { |
548 | let tcx = self.tcx; | |
3c0e092e XL |
549 | let OpaqueTypeKey { def_id, substs } = opaque_type_key; |
550 | ||
3c0e092e XL |
551 | // Ideally, we'd get the span where *this specific `ty` came |
552 | // from*, but right now we just use the span from the overall | |
553 | // value being folded. In simple cases like `-> impl Foo`, | |
554 | // these are the same span, but not in cases like `-> (impl | |
555 | // Foo, impl Bar)`. | |
5e7ed085 | 556 | let span = cause.span; |
3c0e092e | 557 | |
5e7ed085 FG |
558 | let mut obligations = vec![]; |
559 | let prev = self.inner.borrow_mut().opaque_types().register( | |
560 | OpaqueTypeKey { def_id, substs }, | |
561 | OpaqueHiddenType { ty: hidden_ty, span }, | |
562 | origin, | |
563 | ); | |
564 | if let Some(prev) = prev { | |
565 | obligations = self.at(&cause, param_env).eq(prev, hidden_ty)?.obligations; | |
566 | } | |
3c0e092e | 567 | |
04454e1e | 568 | let item_bounds = tcx.bound_explicit_item_bounds(def_id); |
3c0e092e | 569 | |
04454e1e | 570 | for predicate in item_bounds.transpose_iter().map(|e| e.map_bound(|(p, _)| *p)) { |
3c0e092e XL |
571 | debug!(?predicate); |
572 | let predicate = predicate.subst(tcx, substs); | |
3c0e092e | 573 | |
5099ac24 FG |
574 | let predicate = predicate.fold_with(&mut BottomUpFolder { |
575 | tcx, | |
576 | ty_op: |ty| match *ty.kind() { | |
5e7ed085 FG |
577 | // We can't normalize associated types from `rustc_infer`, |
578 | // but we can eagerly register inference variables for them. | |
5099ac24 | 579 | ty::Projection(projection_ty) if !projection_ty.has_escaping_bound_vars() => { |
5e7ed085 FG |
580 | self.infer_projection( |
581 | param_env, | |
582 | projection_ty, | |
583 | cause.clone(), | |
5099ac24 | 584 | 0, |
5e7ed085 | 585 | &mut obligations, |
5099ac24 FG |
586 | ) |
587 | } | |
5e7ed085 FG |
588 | // Replace all other mentions of the same opaque type with the hidden type, |
589 | // as the bounds must hold on the hidden type after all. | |
590 | ty::Opaque(def_id2, substs2) if def_id == def_id2 && substs == substs2 => { | |
591 | hidden_ty | |
592 | } | |
3c0e092e XL |
593 | _ => ty, |
594 | }, | |
595 | lt_op: |lt| lt, | |
596 | ct_op: |ct| ct, | |
597 | }); | |
3c0e092e XL |
598 | |
599 | if let ty::PredicateKind::Projection(projection) = predicate.kind().skip_binder() { | |
5099ac24 | 600 | if projection.term.references_error() { |
5e7ed085 FG |
601 | // No point on adding these obligations since there's a type error involved. |
602 | return Ok(InferOk { value: (), obligations: vec![] }); | |
3c0e092e | 603 | } |
5e7ed085 | 604 | trace!("{:#?}", projection.term); |
3c0e092e | 605 | } |
3c0e092e XL |
606 | // Require that the predicate holds for the concrete type. |
607 | debug!(?predicate); | |
5e7ed085 | 608 | obligations.push(traits::Obligation::new(cause.clone(), param_env, predicate)); |
3c0e092e | 609 | } |
5e7ed085 | 610 | Ok(InferOk { value: (), obligations }) |
3c0e092e XL |
611 | } |
612 | } | |
613 | ||
614 | /// Returns `true` if `opaque_hir_id` is a sibling or a child of a sibling of `def_id`. | |
615 | /// | |
616 | /// Example: | |
04454e1e FG |
617 | /// ```ignore UNSOLVED (is this a bug?) |
618 | /// # #![feature(type_alias_impl_trait)] | |
3c0e092e XL |
619 | /// pub mod foo { |
620 | /// pub mod bar { | |
04454e1e | 621 | /// pub trait Bar { /* ... */ } |
3c0e092e XL |
622 | /// pub type Baz = impl Bar; |
623 | /// | |
04454e1e FG |
624 | /// # impl Bar for () {} |
625 | /// fn f1() -> Baz { /* ... */ } | |
3c0e092e | 626 | /// } |
04454e1e | 627 | /// fn f2() -> bar::Baz { /* ... */ } |
3c0e092e XL |
628 | /// } |
629 | /// ``` | |
630 | /// | |
631 | /// Here, `def_id` is the `LocalDefId` of the defining use of the opaque type (e.g., `f1` or `f2`), | |
632 | /// and `opaque_hir_id` is the `HirId` of the definition of the opaque type `Baz`. | |
633 | /// For the above example, this function returns `true` for `f1` and `false` for `f2`. | |
634 | fn may_define_opaque_type(tcx: TyCtxt<'_>, def_id: LocalDefId, opaque_hir_id: hir::HirId) -> bool { | |
635 | let mut hir_id = tcx.hir().local_def_id_to_hir_id(def_id); | |
636 | ||
637 | // Named opaque types can be defined by any siblings or children of siblings. | |
638 | let scope = tcx.hir().get_defining_scope(opaque_hir_id); | |
639 | // We walk up the node tree until we hit the root or the scope of the opaque type. | |
640 | while hir_id != scope && hir_id != hir::CRATE_HIR_ID { | |
5099ac24 | 641 | hir_id = tcx.hir().local_def_id_to_hir_id(tcx.hir().get_parent_item(hir_id)); |
3c0e092e XL |
642 | } |
643 | // Syntactically, we are allowed to define the concrete type if: | |
644 | let res = hir_id == scope; | |
645 | trace!( | |
646 | "may_define_opaque_type(def={:?}, opaque_node={:?}) = {}", | |
647 | tcx.hir().find(hir_id), | |
648 | tcx.hir().get(opaque_hir_id), | |
649 | res | |
650 | ); | |
651 | res | |
652 | } |