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Commit | Line | Data |
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0bf4aa26 | 1 | use rustc::infer::canonical::{Canonical, QueryResponse}; |
60c5eb7d | 2 | use rustc::traits::query::dropck_outlives::trivial_dropck_outlives; |
dfeec247 | 3 | use rustc::traits::query::dropck_outlives::{DropckOutlivesResult, DtorckConstraint}; |
0531ce1d | 4 | use rustc::traits::query::{CanonicalTyGoal, NoSolution}; |
dfeec247 | 5 | use rustc::traits::{Normalized, ObligationCause, TraitEngine, TraitEngineExt}; |
8faf50e0 | 6 | use rustc::ty::query::Providers; |
dfeec247 | 7 | use rustc::ty::subst::{InternalSubsts, Subst}; |
8faf50e0 | 8 | use rustc::ty::{self, ParamEnvAnd, Ty, TyCtxt}; |
dfeec247 XL |
9 | use rustc_data_structures::fx::FxHashSet; |
10 | use rustc_hir::def_id::DefId; | |
11 | use rustc_span::source_map::{Span, DUMMY_SP}; | |
0531ce1d | 12 | |
9fa01778 | 13 | crate fn provide(p: &mut Providers<'_>) { |
dfeec247 | 14 | *p = Providers { dropck_outlives, adt_dtorck_constraint, ..*p }; |
8faf50e0 XL |
15 | } |
16 | ||
17 | fn dropck_outlives<'tcx>( | |
dc9dc135 | 18 | tcx: TyCtxt<'tcx>, |
0bf4aa26 | 19 | canonical_goal: CanonicalTyGoal<'tcx>, |
48663c56 | 20 | ) -> Result<&'tcx Canonical<'tcx, QueryResponse<'tcx, DropckOutlivesResult<'tcx>>>, NoSolution> { |
0bf4aa26 XL |
21 | debug!("dropck_outlives(goal={:#?})", canonical_goal); |
22 | ||
23 | tcx.infer_ctxt().enter_with_canonical( | |
24 | DUMMY_SP, | |
25 | &canonical_goal, | |
26 | |ref infcx, goal, canonical_inference_vars| { | |
27 | let tcx = infcx.tcx; | |
dfeec247 | 28 | let ParamEnvAnd { param_env, value: for_ty } = goal; |
0531ce1d | 29 | |
dfeec247 | 30 | let mut result = DropckOutlivesResult { kinds: vec![], overflows: vec![] }; |
0531ce1d | 31 | |
0bf4aa26 XL |
32 | // A stack of types left to process. Each round, we pop |
33 | // something from the stack and invoke | |
34 | // `dtorck_constraint_for_ty`. This may produce new types that | |
35 | // have to be pushed on the stack. This continues until we have explored | |
36 | // all the reachable types from the type `for_ty`. | |
37 | // | |
38 | // Example: Imagine that we have the following code: | |
39 | // | |
40 | // ```rust | |
41 | // struct A { | |
42 | // value: B, | |
43 | // children: Vec<A>, | |
44 | // } | |
45 | // | |
46 | // struct B { | |
47 | // value: u32 | |
48 | // } | |
49 | // | |
50 | // fn f() { | |
51 | // let a: A = ...; | |
52 | // .. | |
53 | // } // here, `a` is dropped | |
54 | // ``` | |
55 | // | |
56 | // at the point where `a` is dropped, we need to figure out | |
57 | // which types inside of `a` contain region data that may be | |
58 | // accessed by any destructors in `a`. We begin by pushing `A` | |
59 | // onto the stack, as that is the type of `a`. We will then | |
60 | // invoke `dtorck_constraint_for_ty` which will expand `A` | |
61 | // into the types of its fields `(B, Vec<A>)`. These will get | |
62 | // pushed onto the stack. Eventually, expanding `Vec<A>` will | |
63 | // lead to us trying to push `A` a second time -- to prevent | |
64 | // infinite recursion, we notice that `A` was already pushed | |
65 | // once and stop. | |
66 | let mut ty_stack = vec![(for_ty, 0)]; | |
67 | ||
68 | // Set used to detect infinite recursion. | |
69 | let mut ty_set = FxHashSet::default(); | |
70 | ||
0731742a | 71 | let mut fulfill_cx = TraitEngine::new(infcx.tcx); |
0bf4aa26 XL |
72 | |
73 | let cause = ObligationCause::dummy(); | |
e74abb32 | 74 | let mut constraints = DtorckConstraint::empty(); |
0bf4aa26 | 75 | while let Some((ty, depth)) = ty_stack.pop() { |
dfeec247 XL |
76 | info!( |
77 | "{} kinds, {} overflows, {} ty_stack", | |
78 | result.kinds.len(), | |
79 | result.overflows.len(), | |
80 | ty_stack.len() | |
81 | ); | |
e74abb32 | 82 | dtorck_constraint_for_ty(tcx, DUMMY_SP, for_ty, depth, ty, &mut constraints)?; |
0bf4aa26 XL |
83 | |
84 | // "outlives" represent types/regions that may be touched | |
85 | // by a destructor. | |
e74abb32 XL |
86 | result.kinds.extend(constraints.outlives.drain(..)); |
87 | result.overflows.extend(constraints.overflows.drain(..)); | |
88 | ||
89 | // If we have even one overflow, we should stop trying to evaluate further -- | |
90 | // chances are, the subsequent overflows for this evaluation won't provide useful | |
91 | // information and will just decrease the speed at which we can emit these errors | |
92 | // (since we'll be printing for just that much longer for the often enormous types | |
93 | // that result here). | |
94 | if result.overflows.len() >= 1 { | |
95 | break; | |
96 | } | |
0bf4aa26 XL |
97 | |
98 | // dtorck types are "types that will get dropped but which | |
99 | // do not themselves define a destructor", more or less. We have | |
100 | // to push them onto the stack to be expanded. | |
e74abb32 | 101 | for ty in constraints.dtorck_types.drain(..) { |
0bf4aa26 | 102 | match infcx.at(&cause, param_env).normalize(&ty) { |
dfeec247 | 103 | Ok(Normalized { value: ty, obligations }) => { |
0bf4aa26 XL |
104 | fulfill_cx.register_predicate_obligations(infcx, obligations); |
105 | ||
106 | debug!("dropck_outlives: ty from dtorck_types = {:?}", ty); | |
107 | ||
e74abb32 | 108 | match ty.kind { |
0bf4aa26 XL |
109 | // All parameters live for the duration of the |
110 | // function. | |
111 | ty::Param(..) => {} | |
112 | ||
113 | // A projection that we couldn't resolve - it | |
114 | // might have a destructor. | |
115 | ty::Projection(..) | ty::Opaque(..) => { | |
116 | result.kinds.push(ty.into()); | |
117 | } | |
0531ce1d | 118 | |
0bf4aa26 XL |
119 | _ => { |
120 | if ty_set.insert(ty) { | |
121 | ty_stack.push((ty, depth + 1)); | |
122 | } | |
0531ce1d XL |
123 | } |
124 | } | |
125 | } | |
0531ce1d | 126 | |
0bf4aa26 XL |
127 | // We don't actually expect to fail to normalize. |
128 | // That implies a WF error somewhere else. | |
129 | Err(NoSolution) => { | |
130 | return Err(NoSolution); | |
131 | } | |
0531ce1d XL |
132 | } |
133 | } | |
134 | } | |
0531ce1d | 135 | |
0bf4aa26 | 136 | debug!("dropck_outlives: result = {:#?}", result); |
0531ce1d | 137 | |
0731742a XL |
138 | infcx.make_canonicalized_query_response( |
139 | canonical_inference_vars, | |
140 | result, | |
dfeec247 | 141 | &mut *fulfill_cx, |
0731742a | 142 | ) |
0bf4aa26 XL |
143 | }, |
144 | ) | |
0531ce1d XL |
145 | } |
146 | ||
9fa01778 | 147 | /// Returns a set of constraints that needs to be satisfied in |
0531ce1d | 148 | /// order for `ty` to be valid for destruction. |
dc9dc135 XL |
149 | fn dtorck_constraint_for_ty<'tcx>( |
150 | tcx: TyCtxt<'tcx>, | |
0531ce1d XL |
151 | span: Span, |
152 | for_ty: Ty<'tcx>, | |
153 | depth: usize, | |
154 | ty: Ty<'tcx>, | |
e74abb32 XL |
155 | constraints: &mut DtorckConstraint<'tcx>, |
156 | ) -> Result<(), NoSolution> { | |
dfeec247 | 157 | debug!("dtorck_constraint_for_ty({:?}, {:?}, {:?}, {:?})", span, for_ty, depth, ty); |
0531ce1d | 158 | |
83c7162d | 159 | if depth >= *tcx.sess.recursion_limit.get() { |
e74abb32 XL |
160 | constraints.overflows.push(ty); |
161 | return Ok(()); | |
0531ce1d XL |
162 | } |
163 | ||
60c5eb7d | 164 | if trivial_dropck_outlives(tcx, ty) { |
e74abb32 XL |
165 | return Ok(()); |
166 | } | |
167 | ||
168 | match ty.kind { | |
b7449926 XL |
169 | ty::Bool |
170 | | ty::Char | |
171 | | ty::Int(_) | |
172 | | ty::Uint(_) | |
173 | | ty::Float(_) | |
174 | | ty::Str | |
175 | | ty::Never | |
176 | | ty::Foreign(..) | |
177 | | ty::RawPtr(..) | |
178 | | ty::Ref(..) | |
179 | | ty::FnDef(..) | |
180 | | ty::FnPtr(_) | |
181 | | ty::GeneratorWitness(..) => { | |
0531ce1d | 182 | // these types never have a destructor |
0531ce1d XL |
183 | } |
184 | ||
b7449926 | 185 | ty::Array(ety, _) | ty::Slice(ety) => { |
0531ce1d | 186 | // single-element containers, behave like their element |
e74abb32 | 187 | dtorck_constraint_for_ty(tcx, span, for_ty, depth + 1, ety, constraints)?; |
0531ce1d XL |
188 | } |
189 | ||
dfeec247 XL |
190 | ty::Tuple(tys) => { |
191 | for ty in tys.iter() { | |
192 | dtorck_constraint_for_ty( | |
193 | tcx, | |
194 | span, | |
195 | for_ty, | |
196 | depth + 1, | |
197 | ty.expect_ty(), | |
198 | constraints, | |
199 | )?; | |
200 | } | |
201 | } | |
0531ce1d | 202 | |
dfeec247 XL |
203 | ty::Closure(def_id, substs) => { |
204 | for ty in substs.as_closure().upvar_tys(def_id, tcx) { | |
205 | dtorck_constraint_for_ty(tcx, span, for_ty, depth + 1, ty, constraints)?; | |
206 | } | |
e74abb32 | 207 | } |
0531ce1d | 208 | |
b7449926 | 209 | ty::Generator(def_id, substs, _movability) => { |
83c7162d XL |
210 | // rust-lang/rust#49918: types can be constructed, stored |
211 | // in the interior, and sit idle when generator yields | |
212 | // (and is subsequently dropped). | |
213 | // | |
214 | // It would be nice to descend into interior of a | |
215 | // generator to determine what effects dropping it might | |
216 | // have (by looking at any drop effects associated with | |
217 | // its interior). | |
218 | // | |
219 | // However, the interior's representation uses things like | |
b7449926 | 220 | // GeneratorWitness that explicitly assume they are not |
83c7162d XL |
221 | // traversed in such a manner. So instead, we will |
222 | // simplify things for now by treating all generators as | |
223 | // if they were like trait objects, where its upvars must | |
224 | // all be alive for the generator's (potential) | |
225 | // destructor. | |
226 | // | |
227 | // In particular, skipping over `_interior` is safe | |
228 | // because any side-effects from dropping `_interior` can | |
229 | // only take place through references with lifetimes | |
230 | // derived from lifetimes attached to the upvars, and we | |
231 | // *do* incorporate the upvars here. | |
232 | ||
dfeec247 XL |
233 | constraints.outlives.extend( |
234 | substs | |
235 | .as_generator() | |
236 | .upvar_tys(def_id, tcx) | |
237 | .map(|t| -> ty::subst::GenericArg<'tcx> { t.into() }), | |
238 | ); | |
0531ce1d XL |
239 | } |
240 | ||
b7449926 | 241 | ty::Adt(def, substs) => { |
dfeec247 XL |
242 | let DtorckConstraint { dtorck_types, outlives, overflows } = |
243 | tcx.at(span).adt_dtorck_constraint(def.did)?; | |
e74abb32 XL |
244 | // FIXME: we can try to recursively `dtorck_constraint_on_ty` |
245 | // there, but that needs some way to handle cycles. | |
246 | constraints.dtorck_types.extend(dtorck_types.subst(tcx, substs)); | |
247 | constraints.outlives.extend(outlives.subst(tcx, substs)); | |
248 | constraints.overflows.extend(overflows.subst(tcx, substs)); | |
0531ce1d XL |
249 | } |
250 | ||
251 | // Objects must be alive in order for their destructor | |
252 | // to be called. | |
e74abb32 XL |
253 | ty::Dynamic(..) => { |
254 | constraints.outlives.push(ty.into()); | |
dfeec247 | 255 | } |
0531ce1d XL |
256 | |
257 | // Types that can't be resolved. Pass them forward. | |
e74abb32 XL |
258 | ty::Projection(..) | ty::Opaque(..) | ty::Param(..) => { |
259 | constraints.dtorck_types.push(ty); | |
dfeec247 | 260 | } |
0531ce1d | 261 | |
0bf4aa26 XL |
262 | ty::UnnormalizedProjection(..) => bug!("only used with chalk-engine"), |
263 | ||
a1dfa0c6 | 264 | ty::Placeholder(..) | ty::Bound(..) | ty::Infer(..) | ty::Error => { |
0531ce1d XL |
265 | // By the time this code runs, all type variables ought to |
266 | // be fully resolved. | |
dfeec247 | 267 | return Err(NoSolution); |
0531ce1d | 268 | } |
e74abb32 | 269 | } |
0531ce1d | 270 | |
e74abb32 | 271 | Ok(()) |
0531ce1d XL |
272 | } |
273 | ||
274 | /// Calculates the dtorck constraint for a type. | |
416331ca XL |
275 | crate fn adt_dtorck_constraint( |
276 | tcx: TyCtxt<'_>, | |
0531ce1d | 277 | def_id: DefId, |
416331ca | 278 | ) -> Result<DtorckConstraint<'_>, NoSolution> { |
0531ce1d XL |
279 | let def = tcx.adt_def(def_id); |
280 | let span = tcx.def_span(def_id); | |
281 | debug!("dtorck_constraint: {:?}", def); | |
282 | ||
283 | if def.is_phantom_data() { | |
94b46f34 XL |
284 | // The first generic parameter here is guaranteed to be a type because it's |
285 | // `PhantomData`. | |
532ac7d7 | 286 | let substs = InternalSubsts::identity_for_item(tcx, def_id); |
94b46f34 | 287 | assert_eq!(substs.len(), 1); |
0531ce1d XL |
288 | let result = DtorckConstraint { |
289 | outlives: vec![], | |
94b46f34 | 290 | dtorck_types: vec![substs.type_at(0)], |
0531ce1d XL |
291 | overflows: vec![], |
292 | }; | |
293 | debug!("dtorck_constraint: {:?} => {:?}", def, result); | |
294 | return Ok(result); | |
295 | } | |
296 | ||
e74abb32 XL |
297 | let mut result = DtorckConstraint::empty(); |
298 | for field in def.all_fields() { | |
299 | let fty = tcx.type_of(field.did); | |
300 | dtorck_constraint_for_ty(tcx, span, fty, 0, fty, &mut result)?; | |
301 | } | |
0531ce1d XL |
302 | result.outlives.extend(tcx.destructor_constraints(def)); |
303 | dedup_dtorck_constraint(&mut result); | |
304 | ||
305 | debug!("dtorck_constraint: {:?} => {:?}", def, result); | |
306 | ||
307 | Ok(result) | |
308 | } | |
309 | ||
416331ca | 310 | fn dedup_dtorck_constraint(c: &mut DtorckConstraint<'_>) { |
0bf4aa26 XL |
311 | let mut outlives = FxHashSet::default(); |
312 | let mut dtorck_types = FxHashSet::default(); | |
0531ce1d XL |
313 | |
314 | c.outlives.retain(|&val| outlives.replace(val).is_none()); | |
dfeec247 | 315 | c.dtorck_types.retain(|&val| dtorck_types.replace(val).is_none()); |
0531ce1d | 316 | } |