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|
use rustc::traits::{
GoalKind,
Clause,
ProgramClause,
ProgramClauseCategory,
};
use rustc::ty;
use rustc::ty::subst::{InternalSubsts, Subst};
use rustc::hir::def_id::DefId;
use crate::lowering::Lower;
use crate::generic_types;
crate fn assemble_builtin_unsize_impls<'tcx>(
tcx: ty::TyCtxt<'_, '_, 'tcx>,
unsize_def_id: DefId,
source: ty::Ty<'tcx>,
target: ty::Ty<'tcx>,
clauses: &mut Vec<Clause<'tcx>>
) {
match (&source.sty, &target.sty) {
(ty::Dynamic(data_a, ..), ty::Dynamic(data_b, ..)) => {
if data_a.principal_def_id() != data_b.principal_def_id()
|| data_b.auto_traits().any(|b| data_a.auto_traits().all(|a| a != b))
{
return;
}
// FIXME: rules for trait upcast
}
(_, &ty::Dynamic(..)) => {
// FIXME: basically, we should have something like:
// ```
// forall<T> {
// Implemented(T: Unsize< for<...> dyn Trait<...> >) :-
// for<...> Implemented(T: Trait<...>).
// }
// ```
// The question is: how to correctly handle the higher-ranked
// `for<...>` binder in order to have a generic rule?
// (Having generic rules is useful for caching, as we may be able
// to turn this function and others into tcx queries later on).
}
(ty::Array(_, length), ty::Slice(_)) => {
let ty_param = generic_types::bound(tcx, 0);
let array_ty = tcx.mk_ty(ty::Array(ty_param, length));
let slice_ty = tcx.mk_ty(ty::Slice(ty_param));
// `forall<T> { Implemented([T; N]: Unsize<[T]>). }`
let clause = ProgramClause {
goal: ty::TraitPredicate {
trait_ref: ty::TraitRef {
def_id: unsize_def_id,
substs: tcx.mk_substs_trait(array_ty, &[slice_ty.into()])
},
}.lower(),
hypotheses: ty::List::empty(),
category: ProgramClauseCategory::Other,
};
clauses.push(Clause::ForAll(ty::Binder::bind(clause)));
}
(ty::Infer(ty::TyVar(_)), _) | (_, ty::Infer(ty::TyVar(_))) => {
// FIXME: ambiguous
}
(ty::Adt(def_id_a, ..), ty::Adt(def_id_b, ..)) => {
if def_id_a != def_id_b {
return;
}
// FIXME: rules for struct unsizing
}
(&ty::Tuple(tys_a), &ty::Tuple(tys_b)) => {
if tys_a.len() != tys_b.len() {
return;
}
// FIXME: rules for tuple unsizing
}
_ => (),
}
}
crate fn assemble_builtin_sized_impls<'tcx>(
tcx: ty::TyCtxt<'_, '_, 'tcx>,
sized_def_id: DefId,
ty: ty::Ty<'tcx>,
clauses: &mut Vec<Clause<'tcx>>
) {
let mut push_builtin_impl = |ty: ty::Ty<'tcx>, nested: &[ty::Ty<'tcx>]| {
let clause = ProgramClause {
goal: ty::TraitPredicate {
trait_ref: ty::TraitRef {
def_id: sized_def_id,
substs: tcx.mk_substs_trait(ty, &[]),
},
}.lower(),
hypotheses: tcx.mk_goals(
nested.iter()
.cloned()
.map(|nested_ty| ty::TraitRef {
def_id: sized_def_id,
substs: tcx.mk_substs_trait(nested_ty, &[]),
})
.map(|trait_ref| ty::TraitPredicate { trait_ref })
.map(|pred| GoalKind::DomainGoal(pred.lower()))
.map(|goal_kind| tcx.mk_goal(goal_kind))
),
category: ProgramClauseCategory::Other,
};
// Bind innermost bound vars that may exist in `ty` and `nested`.
clauses.push(Clause::ForAll(ty::Binder::bind(clause)));
};
match &ty.sty {
// Non parametric primitive types.
ty::Bool |
ty::Char |
ty::Int(..) |
ty::Uint(..) |
ty::Float(..) |
ty::Error |
ty::Never => push_builtin_impl(ty, &[]),
// These ones are always `Sized`.
&ty::Array(_, length) => {
push_builtin_impl(tcx.mk_ty(ty::Array(generic_types::bound(tcx, 0), length)), &[]);
}
ty::RawPtr(ptr) => {
push_builtin_impl(generic_types::raw_ptr(tcx, ptr.mutbl), &[]);
}
&ty::Ref(_, _, mutbl) => {
push_builtin_impl(generic_types::ref_ty(tcx, mutbl), &[]);
}
ty::FnPtr(fn_ptr) => {
let fn_ptr = fn_ptr.skip_binder();
let fn_ptr = generic_types::fn_ptr(
tcx,
fn_ptr.inputs_and_output.len(),
fn_ptr.c_variadic,
fn_ptr.unsafety,
fn_ptr.abi
);
push_builtin_impl(fn_ptr, &[]);
}
&ty::FnDef(def_id, ..) => {
push_builtin_impl(generic_types::fn_def(tcx, def_id), &[]);
}
&ty::Closure(def_id, ..) => {
push_builtin_impl(generic_types::closure(tcx, def_id), &[]);
}
&ty::Generator(def_id, ..) => {
push_builtin_impl(generic_types::generator(tcx, def_id), &[]);
}
// `Sized` if the last type is `Sized` (because else we will get a WF error anyway).
&ty::Tuple(type_list) => {
let type_list = generic_types::type_list(tcx, type_list.len());
push_builtin_impl(tcx.mk_ty(ty::Tuple(type_list)), &**type_list);
}
// Struct def
ty::Adt(adt_def, _) => {
let substs = InternalSubsts::bound_vars_for_item(tcx, adt_def.did);
let adt = tcx.mk_ty(ty::Adt(adt_def, substs));
let sized_constraint = adt_def.sized_constraint(tcx)
.iter()
.map(|ty| ty.subst(tcx, substs))
.collect::<Vec<_>>();
push_builtin_impl(adt, &sized_constraint);
}
// Artificially trigger an ambiguity.
ty::Infer(..) => {
// Everybody can find at least two types to unify against:
// general ty vars, int vars and float vars.
push_builtin_impl(tcx.types.i32, &[]);
push_builtin_impl(tcx.types.u32, &[]);
push_builtin_impl(tcx.types.f32, &[]);
push_builtin_impl(tcx.types.f64, &[]);
}
ty::Projection(_projection_ty) => {
// FIXME: add builtin impls from the associated type values found in
// trait impls of `projection_ty.trait_ref(tcx)`.
}
// The `Sized` bound can only come from the environment.
ty::Param(..) |
ty::Placeholder(..) |
ty::UnnormalizedProjection(..) => (),
// Definitely not `Sized`.
ty::Foreign(..) |
ty::Str |
ty::Slice(..) |
ty::Dynamic(..) |
ty::Opaque(..) => (),
ty::Bound(..) |
ty::GeneratorWitness(..) => bug!("unexpected type {:?}", ty),
}
}
|
