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Commit | Line | Data |
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dfeec247 XL |
1 | use rustc_data_structures::fx::FxHashSet; |
2 | use rustc_hir::def_id::DefId; | |
74b04a01 XL |
3 | use rustc_infer::infer::canonical::{Canonical, QueryResponse}; |
4 | use rustc_infer::infer::TyCtxtInferExt; | |
ba9703b0 | 5 | use rustc_middle::ty::query::Providers; |
2b03887a | 6 | use rustc_middle::ty::InternalSubsts; |
04454e1e | 7 | use rustc_middle::ty::{self, EarlyBinder, ParamEnvAnd, Ty, TyCtxt}; |
dfeec247 | 8 | use rustc_span::source_map::{Span, DUMMY_SP}; |
487cf647 | 9 | use rustc_trait_selection::infer::InferCtxtBuilderExt; |
ba9703b0 XL |
10 | use rustc_trait_selection::traits::query::dropck_outlives::trivial_dropck_outlives; |
11 | use rustc_trait_selection::traits::query::dropck_outlives::{ | |
5e7ed085 | 12 | DropckConstraint, DropckOutlivesResult, |
ba9703b0 | 13 | }; |
487cf647 | 14 | use rustc_trait_selection::traits::query::normalize::QueryNormalizeExt; |
ba9703b0 | 15 | use rustc_trait_selection::traits::query::{CanonicalTyGoal, NoSolution}; |
487cf647 | 16 | use rustc_trait_selection::traits::{Normalized, ObligationCause}; |
0531ce1d | 17 | |
923072b8 | 18 | pub(crate) fn provide(p: &mut Providers) { |
dfeec247 | 19 | *p = Providers { dropck_outlives, adt_dtorck_constraint, ..*p }; |
8faf50e0 XL |
20 | } |
21 | ||
22 | fn dropck_outlives<'tcx>( | |
dc9dc135 | 23 | tcx: TyCtxt<'tcx>, |
0bf4aa26 | 24 | canonical_goal: CanonicalTyGoal<'tcx>, |
48663c56 | 25 | ) -> Result<&'tcx Canonical<'tcx, QueryResponse<'tcx, DropckOutlivesResult<'tcx>>>, NoSolution> { |
0bf4aa26 XL |
26 | debug!("dropck_outlives(goal={:#?})", canonical_goal); |
27 | ||
487cf647 FG |
28 | tcx.infer_ctxt().enter_canonical_trait_query(&canonical_goal, |ocx, goal| { |
29 | let tcx = ocx.infcx.tcx; | |
30 | let ParamEnvAnd { param_env, value: for_ty } = goal; | |
31 | ||
32 | let mut result = DropckOutlivesResult { kinds: vec![], overflows: vec![] }; | |
33 | ||
34 | // A stack of types left to process. Each round, we pop | |
35 | // something from the stack and invoke | |
36 | // `dtorck_constraint_for_ty`. This may produce new types that | |
37 | // have to be pushed on the stack. This continues until we have explored | |
38 | // all the reachable types from the type `for_ty`. | |
39 | // | |
40 | // Example: Imagine that we have the following code: | |
41 | // | |
42 | // ```rust | |
43 | // struct A { | |
44 | // value: B, | |
45 | // children: Vec<A>, | |
46 | // } | |
47 | // | |
48 | // struct B { | |
49 | // value: u32 | |
50 | // } | |
51 | // | |
52 | // fn f() { | |
53 | // let a: A = ...; | |
54 | // .. | |
55 | // } // here, `a` is dropped | |
56 | // ``` | |
57 | // | |
58 | // at the point where `a` is dropped, we need to figure out | |
59 | // which types inside of `a` contain region data that may be | |
60 | // accessed by any destructors in `a`. We begin by pushing `A` | |
61 | // onto the stack, as that is the type of `a`. We will then | |
62 | // invoke `dtorck_constraint_for_ty` which will expand `A` | |
63 | // into the types of its fields `(B, Vec<A>)`. These will get | |
64 | // pushed onto the stack. Eventually, expanding `Vec<A>` will | |
65 | // lead to us trying to push `A` a second time -- to prevent | |
66 | // infinite recursion, we notice that `A` was already pushed | |
67 | // once and stop. | |
68 | let mut ty_stack = vec![(for_ty, 0)]; | |
69 | ||
70 | // Set used to detect infinite recursion. | |
71 | let mut ty_set = FxHashSet::default(); | |
72 | ||
73 | let cause = ObligationCause::dummy(); | |
74 | let mut constraints = DropckConstraint::empty(); | |
75 | while let Some((ty, depth)) = ty_stack.pop() { | |
76 | debug!( | |
77 | "{} kinds, {} overflows, {} ty_stack", | |
78 | result.kinds.len(), | |
79 | result.overflows.len(), | |
80 | ty_stack.len() | |
81 | ); | |
82 | dtorck_constraint_for_ty(tcx, DUMMY_SP, for_ty, depth, ty, &mut constraints)?; | |
83 | ||
84 | // "outlives" represent types/regions that may be touched | |
85 | // by a destructor. | |
86 | result.kinds.append(&mut constraints.outlives); | |
87 | result.overflows.append(&mut constraints.overflows); | |
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.is_empty() { | |
95 | break; | |
96 | } | |
2b03887a | 97 | |
487cf647 FG |
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. | |
101 | for ty in constraints.dtorck_types.drain(..) { | |
102 | let Normalized { value: ty, obligations } = | |
103 | ocx.infcx.at(&cause, param_env).query_normalize(ty)?; | |
104 | ocx.register_obligations(obligations); | |
105 | ||
106 | debug!("dropck_outlives: ty from dtorck_types = {:?}", ty); | |
107 | ||
108 | match ty.kind() { | |
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 | |
487cf647 FG |
119 | _ => { |
120 | if ty_set.insert(ty) { | |
121 | ty_stack.push((ty, depth + 1)); | |
0bf4aa26 | 122 | } |
0531ce1d XL |
123 | } |
124 | } | |
125 | } | |
2b03887a | 126 | } |
0531ce1d | 127 | |
487cf647 FG |
128 | debug!("dropck_outlives: result = {:#?}", result); |
129 | Ok(result) | |
130 | }) | |
0531ce1d XL |
131 | } |
132 | ||
9fa01778 | 133 | /// Returns a set of constraints that needs to be satisfied in |
0531ce1d | 134 | /// order for `ty` to be valid for destruction. |
dc9dc135 XL |
135 | fn dtorck_constraint_for_ty<'tcx>( |
136 | tcx: TyCtxt<'tcx>, | |
0531ce1d XL |
137 | span: Span, |
138 | for_ty: Ty<'tcx>, | |
139 | depth: usize, | |
140 | ty: Ty<'tcx>, | |
5e7ed085 | 141 | constraints: &mut DropckConstraint<'tcx>, |
e74abb32 | 142 | ) -> Result<(), NoSolution> { |
dfeec247 | 143 | debug!("dtorck_constraint_for_ty({:?}, {:?}, {:?}, {:?})", span, for_ty, depth, ty); |
0531ce1d | 144 | |
136023e0 | 145 | if !tcx.recursion_limit().value_within_limit(depth) { |
e74abb32 XL |
146 | constraints.overflows.push(ty); |
147 | return Ok(()); | |
0531ce1d XL |
148 | } |
149 | ||
60c5eb7d | 150 | if trivial_dropck_outlives(tcx, ty) { |
e74abb32 XL |
151 | return Ok(()); |
152 | } | |
153 | ||
1b1a35ee | 154 | match ty.kind() { |
b7449926 XL |
155 | ty::Bool |
156 | | ty::Char | |
157 | | ty::Int(_) | |
158 | | ty::Uint(_) | |
159 | | ty::Float(_) | |
160 | | ty::Str | |
161 | | ty::Never | |
162 | | ty::Foreign(..) | |
163 | | ty::RawPtr(..) | |
164 | | ty::Ref(..) | |
165 | | ty::FnDef(..) | |
166 | | ty::FnPtr(_) | |
167 | | ty::GeneratorWitness(..) => { | |
0531ce1d | 168 | // these types never have a destructor |
0531ce1d XL |
169 | } |
170 | ||
b7449926 | 171 | ty::Array(ety, _) | ty::Slice(ety) => { |
0531ce1d | 172 | // single-element containers, behave like their element |
f9f354fc | 173 | rustc_data_structures::stack::ensure_sufficient_stack(|| { |
5099ac24 | 174 | dtorck_constraint_for_ty(tcx, span, for_ty, depth + 1, *ety, constraints) |
f9f354fc | 175 | })?; |
0531ce1d XL |
176 | } |
177 | ||
f9f354fc | 178 | ty::Tuple(tys) => rustc_data_structures::stack::ensure_sufficient_stack(|| { |
dfeec247 | 179 | for ty in tys.iter() { |
5e7ed085 | 180 | dtorck_constraint_for_ty(tcx, span, for_ty, depth + 1, ty, constraints)?; |
dfeec247 | 181 | } |
f9f354fc XL |
182 | Ok::<_, NoSolution>(()) |
183 | })?, | |
0531ce1d | 184 | |
29967ef6 XL |
185 | ty::Closure(_, substs) => { |
186 | if !substs.as_closure().is_valid() { | |
187 | // By the time this code runs, all type variables ought to | |
188 | // be fully resolved. | |
189 | ||
190 | tcx.sess.delay_span_bug( | |
191 | span, | |
192 | &format!("upvar_tys for closure not found. Expected capture information for closure {}", ty,), | |
193 | ); | |
194 | return Err(NoSolution); | |
dfeec247 | 195 | } |
29967ef6 XL |
196 | |
197 | rustc_data_structures::stack::ensure_sufficient_stack(|| { | |
198 | for ty in substs.as_closure().upvar_tys() { | |
199 | dtorck_constraint_for_ty(tcx, span, for_ty, depth + 1, ty, constraints)?; | |
200 | } | |
201 | Ok::<_, NoSolution>(()) | |
202 | })? | |
203 | } | |
0531ce1d | 204 | |
ba9703b0 | 205 | ty::Generator(_, substs, _movability) => { |
83c7162d XL |
206 | // rust-lang/rust#49918: types can be constructed, stored |
207 | // in the interior, and sit idle when generator yields | |
208 | // (and is subsequently dropped). | |
209 | // | |
210 | // It would be nice to descend into interior of a | |
211 | // generator to determine what effects dropping it might | |
212 | // have (by looking at any drop effects associated with | |
213 | // its interior). | |
214 | // | |
215 | // However, the interior's representation uses things like | |
b7449926 | 216 | // GeneratorWitness that explicitly assume they are not |
83c7162d XL |
217 | // traversed in such a manner. So instead, we will |
218 | // simplify things for now by treating all generators as | |
219 | // if they were like trait objects, where its upvars must | |
220 | // all be alive for the generator's (potential) | |
221 | // destructor. | |
222 | // | |
223 | // In particular, skipping over `_interior` is safe | |
224 | // because any side-effects from dropping `_interior` can | |
225 | // only take place through references with lifetimes | |
74b04a01 XL |
226 | // derived from lifetimes attached to the upvars and resume |
227 | // argument, and we *do* incorporate those here. | |
83c7162d | 228 | |
29967ef6 XL |
229 | if !substs.as_generator().is_valid() { |
230 | // By the time this code runs, all type variables ought to | |
231 | // be fully resolved. | |
232 | tcx.sess.delay_span_bug( | |
233 | span, | |
234 | &format!("upvar_tys for generator not found. Expected capture information for generator {}", ty,), | |
235 | ); | |
236 | return Err(NoSolution); | |
237 | } | |
238 | ||
dfeec247 XL |
239 | constraints.outlives.extend( |
240 | substs | |
241 | .as_generator() | |
ba9703b0 | 242 | .upvar_tys() |
dfeec247 XL |
243 | .map(|t| -> ty::subst::GenericArg<'tcx> { t.into() }), |
244 | ); | |
ba9703b0 | 245 | constraints.outlives.push(substs.as_generator().resume_ty().into()); |
0531ce1d XL |
246 | } |
247 | ||
b7449926 | 248 | ty::Adt(def, substs) => { |
5e7ed085 FG |
249 | let DropckConstraint { dtorck_types, outlives, overflows } = |
250 | tcx.at(span).adt_dtorck_constraint(def.did())?; | |
e74abb32 XL |
251 | // FIXME: we can try to recursively `dtorck_constraint_on_ty` |
252 | // there, but that needs some way to handle cycles. | |
04454e1e FG |
253 | constraints |
254 | .dtorck_types | |
255 | .extend(dtorck_types.iter().map(|t| EarlyBinder(*t).subst(tcx, substs))); | |
256 | constraints | |
257 | .outlives | |
258 | .extend(outlives.iter().map(|t| EarlyBinder(*t).subst(tcx, substs))); | |
259 | constraints | |
260 | .overflows | |
261 | .extend(overflows.iter().map(|t| EarlyBinder(*t).subst(tcx, substs))); | |
0531ce1d XL |
262 | } |
263 | ||
264 | // Objects must be alive in order for their destructor | |
265 | // to be called. | |
e74abb32 XL |
266 | ty::Dynamic(..) => { |
267 | constraints.outlives.push(ty.into()); | |
dfeec247 | 268 | } |
0531ce1d XL |
269 | |
270 | // Types that can't be resolved. Pass them forward. | |
e74abb32 XL |
271 | ty::Projection(..) | ty::Opaque(..) | ty::Param(..) => { |
272 | constraints.dtorck_types.push(ty); | |
dfeec247 | 273 | } |
0531ce1d | 274 | |
f035d41b | 275 | ty::Placeholder(..) | ty::Bound(..) | ty::Infer(..) | ty::Error(_) => { |
0531ce1d XL |
276 | // By the time this code runs, all type variables ought to |
277 | // be fully resolved. | |
dfeec247 | 278 | return Err(NoSolution); |
0531ce1d | 279 | } |
e74abb32 | 280 | } |
0531ce1d | 281 | |
e74abb32 | 282 | Ok(()) |
0531ce1d XL |
283 | } |
284 | ||
285 | /// Calculates the dtorck constraint for a type. | |
923072b8 | 286 | pub(crate) fn adt_dtorck_constraint( |
416331ca | 287 | tcx: TyCtxt<'_>, |
0531ce1d | 288 | def_id: DefId, |
5e7ed085 | 289 | ) -> Result<&DropckConstraint<'_>, NoSolution> { |
0531ce1d XL |
290 | let def = tcx.adt_def(def_id); |
291 | let span = tcx.def_span(def_id); | |
292 | debug!("dtorck_constraint: {:?}", def); | |
293 | ||
294 | if def.is_phantom_data() { | |
94b46f34 XL |
295 | // The first generic parameter here is guaranteed to be a type because it's |
296 | // `PhantomData`. | |
532ac7d7 | 297 | let substs = InternalSubsts::identity_for_item(tcx, def_id); |
94b46f34 | 298 | assert_eq!(substs.len(), 1); |
5e7ed085 | 299 | let result = DropckConstraint { |
0531ce1d | 300 | outlives: vec![], |
94b46f34 | 301 | dtorck_types: vec![substs.type_at(0)], |
0531ce1d XL |
302 | overflows: vec![], |
303 | }; | |
304 | debug!("dtorck_constraint: {:?} => {:?}", def, result); | |
5099ac24 | 305 | return Ok(tcx.arena.alloc(result)); |
0531ce1d XL |
306 | } |
307 | ||
5e7ed085 | 308 | let mut result = DropckConstraint::empty(); |
e74abb32 XL |
309 | for field in def.all_fields() { |
310 | let fty = tcx.type_of(field.did); | |
311 | dtorck_constraint_for_ty(tcx, span, fty, 0, fty, &mut result)?; | |
312 | } | |
0531ce1d XL |
313 | result.outlives.extend(tcx.destructor_constraints(def)); |
314 | dedup_dtorck_constraint(&mut result); | |
315 | ||
316 | debug!("dtorck_constraint: {:?} => {:?}", def, result); | |
317 | ||
5099ac24 | 318 | Ok(tcx.arena.alloc(result)) |
0531ce1d XL |
319 | } |
320 | ||
5e7ed085 | 321 | fn dedup_dtorck_constraint(c: &mut DropckConstraint<'_>) { |
0bf4aa26 XL |
322 | let mut outlives = FxHashSet::default(); |
323 | let mut dtorck_types = FxHashSet::default(); | |
0531ce1d XL |
324 | |
325 | c.outlives.retain(|&val| outlives.replace(val).is_none()); | |
dfeec247 | 326 | c.dtorck_types.retain(|&val| dtorck_types.replace(val).is_none()); |
0531ce1d | 327 | } |