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Diffstat (limited to 'compiler/rustc_middle/src/traits/query.rs')
| -rw-r--r-- | compiler/rustc_middle/src/traits/query.rs | 330 |
1 files changed, 330 insertions, 0 deletions
diff --git a/compiler/rustc_middle/src/traits/query.rs b/compiler/rustc_middle/src/traits/query.rs new file mode 100644 index 00000000000..4b7663e9ade --- /dev/null +++ b/compiler/rustc_middle/src/traits/query.rs @@ -0,0 +1,330 @@ +//! Experimental types for the trait query interface. The methods +//! defined in this module are all based on **canonicalization**, +//! which makes a canonical query by replacing unbound inference +//! variables and regions, so that results can be reused more broadly. +//! The providers for the queries defined here can be found in +//! `librustc_traits`. + +use crate::ich::StableHashingContext; +use crate::infer::canonical::{Canonical, QueryResponse}; +use crate::ty::error::TypeError; +use crate::ty::subst::GenericArg; +use crate::ty::{self, Ty, TyCtxt}; + +use rustc_data_structures::stable_hasher::{HashStable, StableHasher}; +use rustc_data_structures::sync::Lrc; +use rustc_errors::struct_span_err; +use rustc_span::source_map::Span; +use std::iter::FromIterator; +use std::mem; + +pub mod type_op { + use crate::ty::fold::TypeFoldable; + use crate::ty::subst::UserSubsts; + use crate::ty::{Predicate, Ty}; + use rustc_hir::def_id::DefId; + use std::fmt; + + #[derive(Copy, Clone, Debug, Hash, PartialEq, Eq, HashStable, TypeFoldable, Lift)] + pub struct AscribeUserType<'tcx> { + pub mir_ty: Ty<'tcx>, + pub def_id: DefId, + pub user_substs: UserSubsts<'tcx>, + } + + impl<'tcx> AscribeUserType<'tcx> { + pub fn new(mir_ty: Ty<'tcx>, def_id: DefId, user_substs: UserSubsts<'tcx>) -> Self { + Self { mir_ty, def_id, user_substs } + } + } + + #[derive(Copy, Clone, Debug, Hash, PartialEq, Eq, HashStable, TypeFoldable, Lift)] + pub struct Eq<'tcx> { + pub a: Ty<'tcx>, + pub b: Ty<'tcx>, + } + + impl<'tcx> Eq<'tcx> { + pub fn new(a: Ty<'tcx>, b: Ty<'tcx>) -> Self { + Self { a, b } + } + } + + #[derive(Copy, Clone, Debug, Hash, PartialEq, Eq, HashStable, TypeFoldable, Lift)] + pub struct Subtype<'tcx> { + pub sub: Ty<'tcx>, + pub sup: Ty<'tcx>, + } + + impl<'tcx> Subtype<'tcx> { + pub fn new(sub: Ty<'tcx>, sup: Ty<'tcx>) -> Self { + Self { sub, sup } + } + } + + #[derive(Copy, Clone, Debug, Hash, PartialEq, Eq, HashStable, TypeFoldable, Lift)] + pub struct ProvePredicate<'tcx> { + pub predicate: Predicate<'tcx>, + } + + impl<'tcx> ProvePredicate<'tcx> { + pub fn new(predicate: Predicate<'tcx>) -> Self { + ProvePredicate { predicate } + } + } + + #[derive(Copy, Clone, Debug, Hash, PartialEq, Eq, HashStable, TypeFoldable, Lift)] + pub struct Normalize<T> { + pub value: T, + } + + impl<'tcx, T> Normalize<T> + where + T: fmt::Debug + TypeFoldable<'tcx>, + { + pub fn new(value: T) -> Self { + Self { value } + } + } +} + +pub type CanonicalProjectionGoal<'tcx> = + Canonical<'tcx, ty::ParamEnvAnd<'tcx, ty::ProjectionTy<'tcx>>>; + +pub type CanonicalTyGoal<'tcx> = Canonical<'tcx, ty::ParamEnvAnd<'tcx, Ty<'tcx>>>; + +pub type CanonicalPredicateGoal<'tcx> = Canonical<'tcx, ty::ParamEnvAnd<'tcx, ty::Predicate<'tcx>>>; + +pub type CanonicalTypeOpAscribeUserTypeGoal<'tcx> = + Canonical<'tcx, ty::ParamEnvAnd<'tcx, type_op::AscribeUserType<'tcx>>>; + +pub type CanonicalTypeOpEqGoal<'tcx> = Canonical<'tcx, ty::ParamEnvAnd<'tcx, type_op::Eq<'tcx>>>; + +pub type CanonicalTypeOpSubtypeGoal<'tcx> = + Canonical<'tcx, ty::ParamEnvAnd<'tcx, type_op::Subtype<'tcx>>>; + +pub type CanonicalTypeOpProvePredicateGoal<'tcx> = + Canonical<'tcx, ty::ParamEnvAnd<'tcx, type_op::ProvePredicate<'tcx>>>; + +pub type CanonicalTypeOpNormalizeGoal<'tcx, T> = + Canonical<'tcx, ty::ParamEnvAnd<'tcx, type_op::Normalize<T>>>; + +#[derive(Clone, Debug, HashStable)] +pub struct NoSolution; + +pub type Fallible<T> = Result<T, NoSolution>; + +impl<'tcx> From<TypeError<'tcx>> for NoSolution { + fn from(_: TypeError<'tcx>) -> NoSolution { + NoSolution + } +} + +#[derive(Clone, Debug, Default, HashStable, TypeFoldable, Lift)] +pub struct DropckOutlivesResult<'tcx> { + pub kinds: Vec<GenericArg<'tcx>>, + pub overflows: Vec<Ty<'tcx>>, +} + +impl<'tcx> DropckOutlivesResult<'tcx> { + pub fn report_overflows(&self, tcx: TyCtxt<'tcx>, span: Span, ty: Ty<'tcx>) { + if let Some(overflow_ty) = self.overflows.get(0) { + let mut err = struct_span_err!( + tcx.sess, + span, + E0320, + "overflow while adding drop-check rules for {}", + ty, + ); + err.note(&format!("overflowed on {}", overflow_ty)); + err.emit(); + } + } + + pub fn into_kinds_reporting_overflows( + self, + tcx: TyCtxt<'tcx>, + span: Span, + ty: Ty<'tcx>, + ) -> Vec<GenericArg<'tcx>> { + self.report_overflows(tcx, span, ty); + let DropckOutlivesResult { kinds, overflows: _ } = self; + kinds + } +} + +/// A set of constraints that need to be satisfied in order for +/// a type to be valid for destruction. +#[derive(Clone, Debug, HashStable)] +pub struct DtorckConstraint<'tcx> { + /// Types that are required to be alive in order for this + /// type to be valid for destruction. + pub outlives: Vec<ty::subst::GenericArg<'tcx>>, + + /// Types that could not be resolved: projections and params. + pub dtorck_types: Vec<Ty<'tcx>>, + + /// If, during the computation of the dtorck constraint, we + /// overflow, that gets recorded here. The caller is expected to + /// report an error. + pub overflows: Vec<Ty<'tcx>>, +} + +impl<'tcx> DtorckConstraint<'tcx> { + pub fn empty() -> DtorckConstraint<'tcx> { + DtorckConstraint { outlives: vec![], dtorck_types: vec![], overflows: vec![] } + } +} + +impl<'tcx> FromIterator<DtorckConstraint<'tcx>> for DtorckConstraint<'tcx> { + fn from_iter<I: IntoIterator<Item = DtorckConstraint<'tcx>>>(iter: I) -> Self { + let mut result = Self::empty(); + + for DtorckConstraint { outlives, dtorck_types, overflows } in iter { + result.outlives.extend(outlives); + result.dtorck_types.extend(dtorck_types); + result.overflows.extend(overflows); + } + + result + } +} + +/// This returns true if the type `ty` is "trivial" for +/// dropck-outlives -- that is, if it doesn't require any types to +/// outlive. This is similar but not *quite* the same as the +/// `needs_drop` test in the compiler already -- that is, for every +/// type T for which this function return true, needs-drop would +/// return `false`. But the reverse does not hold: in particular, +/// `needs_drop` returns false for `PhantomData`, but it is not +/// trivial for dropck-outlives. +/// +/// Note also that `needs_drop` requires a "global" type (i.e., one +/// with erased regions), but this function does not. +pub fn trivial_dropck_outlives<'tcx>(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> bool { + match ty.kind { + // None of these types have a destructor and hence they do not + // require anything in particular to outlive the dtor's + // execution. + ty::Infer(ty::FreshIntTy(_)) + | ty::Infer(ty::FreshFloatTy(_)) + | ty::Bool + | ty::Int(_) + | ty::Uint(_) + | ty::Float(_) + | ty::Never + | ty::FnDef(..) + | ty::FnPtr(_) + | ty::Char + | ty::GeneratorWitness(..) + | ty::RawPtr(_) + | ty::Ref(..) + | ty::Str + | ty::Foreign(..) + | ty::Error(_) => true, + + // [T; N] and [T] have same properties as T. + ty::Array(ty, _) | ty::Slice(ty) => trivial_dropck_outlives(tcx, ty), + + // (T1..Tn) and closures have same properties as T1..Tn -- + // check if *any* of those are trivial. + ty::Tuple(ref tys) => tys.iter().all(|t| trivial_dropck_outlives(tcx, t.expect_ty())), + ty::Closure(_, ref substs) => { + substs.as_closure().upvar_tys().all(|t| trivial_dropck_outlives(tcx, t)) + } + + ty::Adt(def, _) => { + if Some(def.did) == tcx.lang_items().manually_drop() { + // `ManuallyDrop` never has a dtor. + true + } else { + // Other types might. Moreover, PhantomData doesn't + // have a dtor, but it is considered to own its + // content, so it is non-trivial. Unions can have `impl Drop`, + // and hence are non-trivial as well. + false + } + } + + // The following *might* require a destructor: needs deeper inspection. + ty::Dynamic(..) + | ty::Projection(..) + | ty::Param(_) + | ty::Opaque(..) + | ty::Placeholder(..) + | ty::Infer(_) + | ty::Bound(..) + | ty::Generator(..) => false, + } +} + +#[derive(Debug, HashStable)] +pub struct CandidateStep<'tcx> { + pub self_ty: Canonical<'tcx, QueryResponse<'tcx, Ty<'tcx>>>, + pub autoderefs: usize, + /// `true` if the type results from a dereference of a raw pointer. + /// when assembling candidates, we include these steps, but not when + /// picking methods. This so that if we have `foo: *const Foo` and `Foo` has methods + /// `fn by_raw_ptr(self: *const Self)` and `fn by_ref(&self)`, then + /// `foo.by_raw_ptr()` will work and `foo.by_ref()` won't. + pub from_unsafe_deref: bool, + pub unsize: bool, +} + +#[derive(Clone, Debug, HashStable)] +pub struct MethodAutoderefStepsResult<'tcx> { + /// The valid autoderef steps that could be find. + pub steps: Lrc<Vec<CandidateStep<'tcx>>>, + /// If Some(T), a type autoderef reported an error on. + pub opt_bad_ty: Option<Lrc<MethodAutoderefBadTy<'tcx>>>, + /// If `true`, `steps` has been truncated due to reaching the + /// recursion limit. + pub reached_recursion_limit: bool, +} + +#[derive(Debug, HashStable)] +pub struct MethodAutoderefBadTy<'tcx> { + pub reached_raw_pointer: bool, + pub ty: Canonical<'tcx, QueryResponse<'tcx, Ty<'tcx>>>, +} + +/// Result from the `normalize_projection_ty` query. +#[derive(Clone, Debug, HashStable, TypeFoldable, Lift)] +pub struct NormalizationResult<'tcx> { + /// Result of normalization. + pub normalized_ty: Ty<'tcx>, +} + +/// Outlives bounds are relationships between generic parameters, +/// whether they both be regions (`'a: 'b`) or whether types are +/// involved (`T: 'a`). These relationships can be extracted from the +/// full set of predicates we understand or also from types (in which +/// case they are called implied bounds). They are fed to the +/// `OutlivesEnv` which in turn is supplied to the region checker and +/// other parts of the inference system. +#[derive(Clone, Debug, TypeFoldable, Lift)] +pub enum OutlivesBound<'tcx> { + RegionSubRegion(ty::Region<'tcx>, ty::Region<'tcx>), + RegionSubParam(ty::Region<'tcx>, ty::ParamTy), + RegionSubProjection(ty::Region<'tcx>, ty::ProjectionTy<'tcx>), +} + +impl<'a, 'tcx> HashStable<StableHashingContext<'a>> for OutlivesBound<'tcx> { + fn hash_stable(&self, hcx: &mut StableHashingContext<'a>, hasher: &mut StableHasher) { + mem::discriminant(self).hash_stable(hcx, hasher); + match *self { + OutlivesBound::RegionSubRegion(ref a, ref b) => { + a.hash_stable(hcx, hasher); + b.hash_stable(hcx, hasher); + } + OutlivesBound::RegionSubParam(ref a, ref b) => { + a.hash_stable(hcx, hasher); + b.hash_stable(hcx, hasher); + } + OutlivesBound::RegionSubProjection(ref a, ref b) => { + a.hash_stable(hcx, hasher); + b.hash_stable(hcx, hasher); + } + } + } +} |