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Type-check generic const items

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León Orell Valerian Liehr 2023-07-02 18:48:43 +02:00
parent da17134be0
commit 8c390286e4
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4 changed files with 122 additions and 103 deletions
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110
compiler/rustc_hir_analysis/src/check/compare_impl_item.rs
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@ -76,7 +76,7 @@ fn check_method_is_structurally_compatible<'tcx>(
Ok(())
}
/// This function is best explained by example. Consider a trait with it's implementation:
/// This function is best explained by example. Consider a trait with its implementation:
///
/// ```rust
/// trait Trait<'t, T> {
@ -120,7 +120,7 @@ fn check_method_is_structurally_compatible<'tcx>(
/// types:
///
/// ```rust,ignore (pseudo-Rust)
/// <'b> fn(t: &'i0 U0, m: &'b) -> Foo
/// <'b> fn(t: &'i0 U0, m: &'b N0) -> Foo
/// ```
///
/// We now want to extract and substitute the type of the *trait*
@ -137,7 +137,7 @@ fn check_method_is_structurally_compatible<'tcx>(
/// Applying this to the trait method type yields:
///
/// ```rust,ignore (pseudo-Rust)
/// <'a> fn(t: &'i0 U0, m: &'a) -> Foo
/// <'a> fn(t: &'i0 U0, m: &'a N0) -> Foo
/// ```
///
/// This type is also the same but the name of the bound region (`'a`
@ -258,8 +258,6 @@ fn compare_method_predicate_entailment<'tcx>(
// type.
// Compute placeholder form of impl and trait method tys.
let tcx = infcx.tcx;
let mut wf_tys = FxIndexSet::default();
let unnormalized_impl_sig = infcx.instantiate_binder_with_fresh_vars(
@ -1668,19 +1666,19 @@ fn compare_synthetic_generics<'tcx>(
/// ```rust,ignore (pseudo-Rust)
/// trait Foo {
/// fn foo<const N: u8>();
/// type bar<const N: u8>;
/// type Bar<const N: u8>;
/// fn baz<const N: u32>();
/// type blah<T>;
/// type Blah<T>;
/// }
///
/// impl Foo for () {
/// fn foo<const N: u64>() {}
/// //~^ error
/// type bar<const N: u64> {}
/// type Bar<const N: u64> = ();
/// //~^ error
/// fn baz<T>() {}
/// //~^ error
/// type blah<const N: i64> = u32;
/// type Blah<const N: i64> = u32;
/// //~^ error
/// }
/// ```
@ -1769,36 +1767,82 @@ pub(super) fn compare_impl_const_raw(
let trait_const_item = tcx.associated_item(trait_const_item_def);
let impl_trait_ref =
tcx.impl_trait_ref(impl_const_item.container_id(tcx)).unwrap().instantiate_identity();
debug!("compare_const_impl(impl_trait_ref={:?})", impl_trait_ref);
let impl_c_span = tcx.def_span(impl_const_item_def.to_def_id());
debug!("compare_impl_const(impl_trait_ref={:?})", impl_trait_ref);
let infcx = tcx.infer_ctxt().build();
let param_env = tcx.param_env(impl_const_item_def.to_def_id());
let ocx = ObligationCtxt::new(&infcx);
compare_number_of_generics(tcx, impl_const_item, trait_const_item, false)?;
compare_generic_param_kinds(tcx, impl_const_item, trait_const_item, false)?;
compare_const_predicate_entailment(tcx, impl_const_item, trait_const_item, impl_trait_ref)
}
/// The equivalent of [compare_method_predicate_entailment], but for associated constants
/// instead of associated functions.
// FIXME(generic_const_items): If possible extract the common parts of `compare_{type,const}_predicate_entailment`.
fn compare_const_predicate_entailment<'tcx>(
tcx: TyCtxt<'tcx>,
impl_ct: ty::AssocItem,
trait_ct: ty::AssocItem,
impl_trait_ref: ty::TraitRef<'tcx>,
) -> Result<(), ErrorGuaranteed> {
let impl_ct_def_id = impl_ct.def_id.expect_local();
let impl_ct_span = tcx.def_span(impl_ct_def_id);
// The below is for the most part highly similar to the procedure
// for methods above. It is simpler in many respects, especially
// because we shouldn't really have to deal with lifetimes or
// predicates. In fact some of this should probably be put into
// shared functions because of DRY violations...
let trait_to_impl_args = impl_trait_ref.args;
let impl_args = GenericArgs::identity_for_item(tcx, impl_ct.def_id);
let trait_to_impl_args =
impl_args.rebase_onto(tcx, impl_ct.container_id(tcx), impl_trait_ref.args);
// Create a parameter environment that represents the implementation's
// method.
// Compute placeholder form of impl and trait const tys.
let impl_ty = tcx.type_of(impl_const_item_def.to_def_id()).instantiate_identity();
let trait_ty = tcx.type_of(trait_const_item_def).instantiate(tcx, trait_to_impl_args);
let mut cause = ObligationCause::new(
impl_c_span,
impl_const_item_def,
ObligationCauseCode::CompareImplItemObligation {
impl_item_def_id: impl_const_item_def,
trait_item_def_id: trait_const_item_def,
kind: impl_const_item.kind,
},
let impl_ty = tcx.type_of(impl_ct_def_id).instantiate_identity();
let trait_ty = tcx.type_of(trait_ct.def_id).instantiate(tcx, trait_to_impl_args);
let code = ObligationCauseCode::CompareImplItemObligation {
impl_item_def_id: impl_ct_def_id,
trait_item_def_id: trait_ct.def_id,
kind: impl_ct.kind,
};
let mut cause = ObligationCause::new(impl_ct_span, impl_ct_def_id, code.clone());
let impl_ct_predicates = tcx.predicates_of(impl_ct.def_id);
let trait_ct_predicates = tcx.predicates_of(trait_ct.def_id);
check_region_bounds_on_impl_item(tcx, impl_ct, trait_ct, false)?;
// The predicates declared by the impl definition, the trait and the
// associated const in the trait are assumed.
let impl_predicates = tcx.predicates_of(impl_ct_predicates.parent.unwrap());
let mut hybrid_preds = impl_predicates.instantiate_identity(tcx);
hybrid_preds.predicates.extend(
trait_ct_predicates
.instantiate_own(tcx, trait_to_impl_args)
.map(|(predicate, _)| predicate),
);
let param_env = ty::ParamEnv::new(tcx.mk_clauses(&hybrid_preds.predicates), Reveal::UserFacing);
let param_env = traits::normalize_param_env_or_error(
tcx,
param_env,
ObligationCause::misc(impl_ct_span, impl_ct_def_id),
);
let infcx = tcx.infer_ctxt().build();
let ocx = ObligationCtxt::new(&infcx);
let impl_ct_own_bounds = impl_ct_predicates.instantiate_own(tcx, impl_args);
for (predicate, span) in impl_ct_own_bounds {
let cause = ObligationCause::misc(span, impl_ct_def_id);
let predicate = ocx.normalize(&cause, param_env, predicate);
let cause = ObligationCause::new(span, impl_ct_def_id, code.clone());
ocx.register_obligation(traits::Obligation::new(tcx, cause, param_env, predicate));
}
// There is no "body" here, so just pass dummy id.
let impl_ty = ocx.normalize(&cause, param_env, impl_ty);
@ -1817,7 +1861,7 @@ pub(super) fn compare_impl_const_raw(
);
// Locate the Span containing just the type of the offending impl
let (ty, _) = tcx.hir().expect_impl_item(impl_const_item_def).expect_const();
let (ty, _) = tcx.hir().expect_impl_item(impl_ct_def_id).expect_const();
cause.span = ty.span;
let mut diag = struct_span_err!(
@ -1825,12 +1869,12 @@ pub(super) fn compare_impl_const_raw(
cause.span,
E0326,
"implemented const `{}` has an incompatible type for trait",
trait_const_item.name
trait_ct.name
);
let trait_c_span = trait_const_item_def.as_local().map(|trait_c_def_id| {
let trait_c_span = trait_ct.def_id.as_local().map(|trait_ct_def_id| {
// Add a label to the Span containing just the type of the const
let (ty, _) = tcx.hir().expect_trait_item(trait_c_def_id).expect_const();
let (ty, _) = tcx.hir().expect_trait_item(trait_ct_def_id).expect_const();
ty.span
});
@ -1857,7 +1901,7 @@ pub(super) fn compare_impl_const_raw(
}
let outlives_env = OutlivesEnvironment::new(param_env);
ocx.resolve_regions_and_report_errors(impl_const_item_def, &outlives_env)
ocx.resolve_regions_and_report_errors(impl_ct_def_id, &outlives_env)
}
pub(super) fn compare_impl_ty<'tcx>(
@ -1899,7 +1943,7 @@ fn compare_type_predicate_entailment<'tcx>(
return Ok(());
}
// This `HirId` should be used for the `body_id` field on each
// This `DefId` should be used for the `body_id` field on each
// `ObligationCause` (and the `FnCtxt`). This is what
// `regionck_item` expects.
let impl_ty_def_id = impl_ty.def_id.expect_local();
@ -1918,7 +1962,7 @@ fn compare_type_predicate_entailment<'tcx>(
debug!("compare_type_predicate_entailment: bounds={:?}", hybrid_preds);
let impl_ty_span = tcx.def_span(impl_ty_def_id);
let normalize_cause = traits::ObligationCause::misc(impl_ty_span, impl_ty_def_id);
let normalize_cause = ObligationCause::misc(impl_ty_span, impl_ty_def_id);
let param_env = ty::ParamEnv::new(tcx.mk_clauses(&hybrid_preds.predicates), Reveal::UserFacing);
let param_env = traits::normalize_param_env_or_error(tcx, param_env, normalize_cause);
let infcx = tcx.infer_ctxt().build();
@ -1963,7 +2007,7 @@ fn compare_type_predicate_entailment<'tcx>(
///
/// trait X { type Y: Copy } impl X for T { type Y = S; }
///
/// We are able to normalize `<T as X>::U` to `S`, and so when we check the
/// We are able to normalize `<T as X>::Y` to `S`, and so when we check the
/// impl is well-formed we have to prove `S: Copy`.
///
/// For default associated types the normalization is not possible (the value