|
1 | | -use rustc_hir as hir; |
| 1 | +use rustc_hir::{self as hir, LangItem}; |
2 | 2 | use rustc_infer::infer::{BoundRegionConversionTime, DefineOpaqueTypes}; |
3 | 3 | use rustc_infer::traits::{ |
4 | 4 | ImplDerivedHostCause, ImplSource, Obligation, ObligationCauseCode, PredicateObligation, |
@@ -48,6 +48,12 @@ pub fn evaluate_host_effect_obligation<'tcx>( |
48 | 48 | Err(EvaluationFailure::NoSolution) => {} |
49 | 49 | } |
50 | 50 |
|
| 51 | + match evaluate_host_effect_from_builtin_impls(selcx, obligation) { |
| 52 | + Ok(result) => return Ok(result), |
| 53 | + Err(EvaluationFailure::Ambiguous) => return Err(EvaluationFailure::Ambiguous), |
| 54 | + Err(EvaluationFailure::NoSolution) => {} |
| 55 | + } |
| 56 | + |
51 | 57 | match evaluate_host_effect_from_selection_candiate(selcx, obligation) { |
52 | 58 | Ok(result) => return Ok(result), |
53 | 59 | Err(EvaluationFailure::Ambiguous) => return Err(EvaluationFailure::Ambiguous), |
@@ -228,6 +234,104 @@ fn evaluate_host_effect_from_item_bounds<'tcx>( |
228 | 234 | } |
229 | 235 | } |
230 | 236 |
|
| 237 | +fn evaluate_host_effect_from_builtin_impls<'tcx>( |
| 238 | + selcx: &mut SelectionContext<'_, 'tcx>, |
| 239 | + obligation: &HostEffectObligation<'tcx>, |
| 240 | +) -> Result<ThinVec<PredicateObligation<'tcx>>, EvaluationFailure> { |
| 241 | + match selcx.tcx().as_lang_item(obligation.predicate.def_id()) { |
| 242 | + Some(LangItem::Destruct) => evaluate_host_effect_for_destruct_goal(selcx, obligation), |
| 243 | + _ => Err(EvaluationFailure::NoSolution), |
| 244 | + } |
| 245 | +} |
| 246 | + |
| 247 | +// NOTE: Keep this in sync with `const_conditions_for_destruct` in the new solver. |
| 248 | +fn evaluate_host_effect_for_destruct_goal<'tcx>( |
| 249 | + selcx: &mut SelectionContext<'_, 'tcx>, |
| 250 | + obligation: &HostEffectObligation<'tcx>, |
| 251 | +) -> Result<ThinVec<PredicateObligation<'tcx>>, EvaluationFailure> { |
| 252 | + let tcx = selcx.tcx(); |
| 253 | + let destruct_def_id = tcx.require_lang_item(LangItem::Destruct, None); |
| 254 | + let self_ty = obligation.predicate.self_ty(); |
| 255 | + |
| 256 | + let const_conditions = match *self_ty.kind() { |
| 257 | + // An ADT is `~const Destruct` only if all of the fields are, |
| 258 | + // *and* if there is a `Drop` impl, that `Drop` impl is also `~const`. |
| 259 | + ty::Adt(adt_def, args) => { |
| 260 | + let mut const_conditions: ThinVec<_> = adt_def |
| 261 | + .all_fields() |
| 262 | + .map(|field| ty::TraitRef::new(tcx, destruct_def_id, [field.ty(tcx, args)])) |
| 263 | + .collect(); |
| 264 | + match adt_def.destructor(tcx).map(|dtor| dtor.constness) { |
| 265 | + // `Drop` impl exists, but it's not const. Type cannot be `~const Destruct`. |
| 266 | + Some(hir::Constness::NotConst) => return Err(EvaluationFailure::NoSolution), |
| 267 | + // `Drop` impl exists, and it's const. Require `Ty: ~const Drop` to hold. |
| 268 | + Some(hir::Constness::Const) => { |
| 269 | + let drop_def_id = tcx.require_lang_item(LangItem::Drop, None); |
| 270 | + let drop_trait_ref = ty::TraitRef::new(tcx, drop_def_id, [self_ty]); |
| 271 | + const_conditions.push(drop_trait_ref); |
| 272 | + } |
| 273 | + // No `Drop` impl, no need to require anything else. |
| 274 | + None => {} |
| 275 | + } |
| 276 | + const_conditions |
| 277 | + } |
| 278 | + |
| 279 | + ty::Array(ty, _) | ty::Pat(ty, _) | ty::Slice(ty) => { |
| 280 | + thin_vec![ty::TraitRef::new(tcx, destruct_def_id, [ty])] |
| 281 | + } |
| 282 | + |
| 283 | + ty::Tuple(tys) => { |
| 284 | + tys.iter().map(|field_ty| ty::TraitRef::new(tcx, destruct_def_id, [field_ty])).collect() |
| 285 | + } |
| 286 | + |
| 287 | + // Trivially implement `~const Destruct` |
| 288 | + ty::Bool |
| 289 | + | ty::Char |
| 290 | + | ty::Int(..) |
| 291 | + | ty::Uint(..) |
| 292 | + | ty::Float(..) |
| 293 | + | ty::Str |
| 294 | + | ty::RawPtr(..) |
| 295 | + | ty::Ref(..) |
| 296 | + | ty::FnDef(..) |
| 297 | + | ty::FnPtr(..) |
| 298 | + | ty::Never |
| 299 | + | ty::Infer(ty::InferTy::FloatVar(_) | ty::InferTy::IntVar(_)) |
| 300 | + | ty::Error(_) => thin_vec![], |
| 301 | + |
| 302 | + // Coroutines and closures could implement `~const Drop`, |
| 303 | + // but they don't really need to right now. |
| 304 | + ty::Closure(_, _) |
| 305 | + | ty::CoroutineClosure(_, _) |
| 306 | + | ty::Coroutine(_, _) |
| 307 | + | ty::CoroutineWitness(_, _) => return Err(EvaluationFailure::NoSolution), |
| 308 | + |
| 309 | + // FIXME(unsafe_binders): Unsafe binders could implement `~const Drop` |
| 310 | + // if their inner type implements it. |
| 311 | + ty::UnsafeBinder(_) => return Err(EvaluationFailure::NoSolution), |
| 312 | + |
| 313 | + ty::Dynamic(..) | ty::Param(_) | ty::Alias(..) | ty::Placeholder(_) | ty::Foreign(_) => { |
| 314 | + return Err(EvaluationFailure::NoSolution); |
| 315 | + } |
| 316 | + |
| 317 | + ty::Bound(..) |
| 318 | + | ty::Infer(ty::TyVar(_) | ty::FreshTy(_) | ty::FreshIntTy(_) | ty::FreshFloatTy(_)) => { |
| 319 | + panic!("unexpected type `{self_ty:?}`") |
| 320 | + } |
| 321 | + }; |
| 322 | + |
| 323 | + Ok(const_conditions |
| 324 | + .into_iter() |
| 325 | + .map(|trait_ref| { |
| 326 | + obligation.with( |
| 327 | + tcx, |
| 328 | + ty::Binder::dummy(trait_ref) |
| 329 | + .to_host_effect_clause(tcx, obligation.predicate.constness), |
| 330 | + ) |
| 331 | + }) |
| 332 | + .collect()) |
| 333 | +} |
| 334 | + |
231 | 335 | fn evaluate_host_effect_from_selection_candiate<'tcx>( |
232 | 336 | selcx: &mut SelectionContext<'_, 'tcx>, |
233 | 337 | obligation: &HostEffectObligation<'tcx>, |
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