Change InferCtxtBuilder from enter to build
This commit is contained in:
Cameron Steffen
parent
91269fa5b8
commit
283abbf0e7
53 changed files with 1966 additions and 2182 deletions
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@ -108,43 +108,42 @@ fn visit_implementation_of_copy(tcx: TyCtxt<'_>, impl_did: LocalDefId) {
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// why this field does not implement Copy. This is useful because sometimes
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// it is not immediately clear why Copy is not implemented for a field, since
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// all we point at is the field itself.
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tcx.infer_ctxt().ignoring_regions().enter(|infcx| {
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for error in traits::fully_solve_bound(
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&infcx,
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traits::ObligationCause::dummy_with_span(field_ty_span),
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param_env,
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ty,
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tcx.lang_items().copy_trait().unwrap(),
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) {
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let error_predicate = error.obligation.predicate;
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// Only note if it's not the root obligation, otherwise it's trivial and
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// should be self-explanatory (i.e. a field literally doesn't implement Copy).
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let infcx = tcx.infer_ctxt().ignoring_regions().build();
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for error in traits::fully_solve_bound(
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&infcx,
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traits::ObligationCause::dummy_with_span(field_ty_span),
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param_env,
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ty,
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tcx.lang_items().copy_trait().unwrap(),
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) {
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let error_predicate = error.obligation.predicate;
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// Only note if it's not the root obligation, otherwise it's trivial and
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// should be self-explanatory (i.e. a field literally doesn't implement Copy).
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// FIXME: This error could be more descriptive, especially if the error_predicate
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// contains a foreign type or if it's a deeply nested type...
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if error_predicate != error.root_obligation.predicate {
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errors
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.entry((ty.to_string(), error_predicate.to_string()))
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.or_default()
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.push(error.obligation.cause.span);
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}
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if let ty::PredicateKind::Trait(ty::TraitPredicate {
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trait_ref,
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polarity: ty::ImplPolarity::Positive,
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..
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}) = error_predicate.kind().skip_binder()
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{
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let ty = trait_ref.self_ty();
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if let ty::Param(_) = ty.kind() {
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bounds.push((
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format!("{ty}"),
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trait_ref.print_only_trait_path().to_string(),
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Some(trait_ref.def_id),
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));
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}
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// FIXME: This error could be more descriptive, especially if the error_predicate
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// contains a foreign type or if it's a deeply nested type...
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if error_predicate != error.root_obligation.predicate {
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errors
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.entry((ty.to_string(), error_predicate.to_string()))
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.or_default()
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.push(error.obligation.cause.span);
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}
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if let ty::PredicateKind::Trait(ty::TraitPredicate {
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trait_ref,
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polarity: ty::ImplPolarity::Positive,
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..
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}) = error_predicate.kind().skip_binder()
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{
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let ty = trait_ref.self_ty();
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if let ty::Param(_) = ty.kind() {
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bounds.push((
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format!("{ty}"),
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trait_ref.print_only_trait_path().to_string(),
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Some(trait_ref.def_id),
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));
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}
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}
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});
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}
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}
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for ((ty, error_predicate), spans) in errors {
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let span: MultiSpan = spans.into();
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@ -205,91 +204,89 @@ fn visit_implementation_of_dispatch_from_dyn<'tcx>(tcx: TyCtxt<'tcx>, impl_did:
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let create_err = |msg: &str| struct_span_err!(tcx.sess, span, E0378, "{}", msg);
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tcx.infer_ctxt().enter(|infcx| {
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let cause = ObligationCause::misc(span, impl_hir_id);
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let infcx = tcx.infer_ctxt().build();
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let cause = ObligationCause::misc(span, impl_hir_id);
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use rustc_type_ir::sty::TyKind::*;
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match (source.kind(), target.kind()) {
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(&Ref(r_a, _, mutbl_a), Ref(r_b, _, mutbl_b))
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if infcx.at(&cause, param_env).eq(r_a, *r_b).is_ok() && mutbl_a == *mutbl_b => {}
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(&RawPtr(tm_a), &RawPtr(tm_b)) if tm_a.mutbl == tm_b.mutbl => (),
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(&Adt(def_a, substs_a), &Adt(def_b, substs_b))
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if def_a.is_struct() && def_b.is_struct() =>
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{
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if def_a != def_b {
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let source_path = tcx.def_path_str(def_a.did());
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let target_path = tcx.def_path_str(def_b.did());
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use rustc_type_ir::sty::TyKind::*;
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match (source.kind(), target.kind()) {
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(&Ref(r_a, _, mutbl_a), Ref(r_b, _, mutbl_b))
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if infcx.at(&cause, param_env).eq(r_a, *r_b).is_ok() && mutbl_a == *mutbl_b => {}
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(&RawPtr(tm_a), &RawPtr(tm_b)) if tm_a.mutbl == tm_b.mutbl => (),
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(&Adt(def_a, substs_a), &Adt(def_b, substs_b))
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if def_a.is_struct() && def_b.is_struct() =>
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{
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if def_a != def_b {
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let source_path = tcx.def_path_str(def_a.did());
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let target_path = tcx.def_path_str(def_b.did());
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create_err(&format!(
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"the trait `DispatchFromDyn` may only be implemented \
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for a coercion between structures with the same \
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definition; expected `{}`, found `{}`",
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source_path, target_path,
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))
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.emit();
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create_err(&format!(
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"the trait `DispatchFromDyn` may only be implemented \
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for a coercion between structures with the same \
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definition; expected `{}`, found `{}`",
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source_path, target_path,
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))
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.emit();
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return;
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}
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return;
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}
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if def_a.repr().c() || def_a.repr().packed() {
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create_err(
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"structs implementing `DispatchFromDyn` may not have \
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`#[repr(packed)]` or `#[repr(C)]`",
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)
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.emit();
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}
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if def_a.repr().c() || def_a.repr().packed() {
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create_err(
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"structs implementing `DispatchFromDyn` may not have \
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`#[repr(packed)]` or `#[repr(C)]`",
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)
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.emit();
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}
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let fields = &def_a.non_enum_variant().fields;
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let fields = &def_a.non_enum_variant().fields;
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let coerced_fields = fields
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.iter()
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.filter(|field| {
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let ty_a = field.ty(tcx, substs_a);
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let ty_b = field.ty(tcx, substs_b);
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let coerced_fields = fields
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.iter()
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.filter(|field| {
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let ty_a = field.ty(tcx, substs_a);
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let ty_b = field.ty(tcx, substs_b);
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if let Ok(layout) = tcx.layout_of(param_env.and(ty_a)) {
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if layout.is_zst() && layout.align.abi.bytes() == 1 {
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// ignore ZST fields with alignment of 1 byte
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return false;
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}
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if let Ok(layout) = tcx.layout_of(param_env.and(ty_a)) {
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if layout.is_zst() && layout.align.abi.bytes() == 1 {
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// ignore ZST fields with alignment of 1 byte
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return false;
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}
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}
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if let Ok(ok) = infcx.at(&cause, param_env).eq(ty_a, ty_b) {
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if ok.obligations.is_empty() {
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create_err(
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"the trait `DispatchFromDyn` may only be implemented \
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for structs containing the field being coerced, \
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ZST fields with 1 byte alignment, and nothing else",
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)
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.note(&format!(
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"extra field `{}` of type `{}` is not allowed",
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field.name, ty_a,
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))
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.emit();
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if let Ok(ok) = infcx.at(&cause, param_env).eq(ty_a, ty_b) {
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if ok.obligations.is_empty() {
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create_err(
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"the trait `DispatchFromDyn` may only be implemented \
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for structs containing the field being coerced, \
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ZST fields with 1 byte alignment, and nothing else",
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)
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.note(&format!(
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"extra field `{}` of type `{}` is not allowed",
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field.name, ty_a,
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))
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.emit();
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return false;
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}
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return false;
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}
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}
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return true;
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})
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.collect::<Vec<_>>();
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return true;
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})
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.collect::<Vec<_>>();
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if coerced_fields.is_empty() {
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create_err(
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"the trait `DispatchFromDyn` may only be implemented \
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for a coercion between structures with a single field \
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being coerced, none found",
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)
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.emit();
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} else if coerced_fields.len() > 1 {
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create_err(
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"implementing the `DispatchFromDyn` trait requires multiple coercions",
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)
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if coerced_fields.is_empty() {
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create_err(
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"the trait `DispatchFromDyn` may only be implemented \
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for a coercion between structures with a single field \
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being coerced, none found",
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)
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.emit();
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} else if coerced_fields.len() > 1 {
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create_err("implementing the `DispatchFromDyn` trait requires multiple coercions")
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.note(
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"the trait `DispatchFromDyn` may only be implemented \
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for a coercion between structures with a single field \
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being coerced",
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for a coercion between structures with a single field \
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being coerced",
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)
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.note(&format!(
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"currently, {} fields need coercions: {}",
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@ -308,39 +305,38 @@ fn visit_implementation_of_dispatch_from_dyn<'tcx>(tcx: TyCtxt<'tcx>, impl_did:
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.join(", ")
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))
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.emit();
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} else {
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let errors = traits::fully_solve_obligations(
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&infcx,
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coerced_fields.into_iter().map(|field| {
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predicate_for_trait_def(
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tcx,
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param_env,
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cause.clone(),
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dispatch_from_dyn_trait,
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0,
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field.ty(tcx, substs_a),
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&[field.ty(tcx, substs_b).into()],
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)
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}),
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);
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if !errors.is_empty() {
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infcx.err_ctxt().report_fulfillment_errors(&errors, None, false);
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}
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// Finally, resolve all regions.
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let outlives_env = OutlivesEnvironment::new(param_env);
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infcx.check_region_obligations_and_report_errors(impl_did, &outlives_env);
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} else {
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let errors = traits::fully_solve_obligations(
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&infcx,
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coerced_fields.into_iter().map(|field| {
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predicate_for_trait_def(
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tcx,
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param_env,
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cause.clone(),
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dispatch_from_dyn_trait,
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0,
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field.ty(tcx, substs_a),
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&[field.ty(tcx, substs_b).into()],
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)
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}),
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);
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if !errors.is_empty() {
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infcx.err_ctxt().report_fulfillment_errors(&errors, None, false);
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}
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}
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_ => {
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create_err(
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"the trait `DispatchFromDyn` may only be implemented \
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for a coercion between structures",
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)
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.emit();
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// Finally, resolve all regions.
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let outlives_env = OutlivesEnvironment::new(param_env);
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infcx.check_region_obligations_and_report_errors(impl_did, &outlives_env);
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}
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}
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})
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_ => {
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create_err(
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"the trait `DispatchFromDyn` may only be implemented \
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for a coercion between structures",
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)
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.emit();
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}
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}
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}
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pub fn coerce_unsized_info<'tcx>(tcx: TyCtxt<'tcx>, impl_did: DefId) -> CoerceUnsizedInfo {
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@ -369,221 +365,208 @@ pub fn coerce_unsized_info<'tcx>(tcx: TyCtxt<'tcx>, impl_did: DefId) -> CoerceUn
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debug!("visit_implementation_of_coerce_unsized: {:?} -> {:?} (free)", source, target);
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tcx.infer_ctxt().enter(|infcx| {
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let impl_hir_id = tcx.hir().local_def_id_to_hir_id(impl_did);
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let cause = ObligationCause::misc(span, impl_hir_id);
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let check_mutbl = |mt_a: ty::TypeAndMut<'tcx>,
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mt_b: ty::TypeAndMut<'tcx>,
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mk_ptr: &dyn Fn(Ty<'tcx>) -> Ty<'tcx>| {
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if (mt_a.mutbl, mt_b.mutbl) == (hir::Mutability::Not, hir::Mutability::Mut) {
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infcx
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.err_ctxt()
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.report_mismatched_types(
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&cause,
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mk_ptr(mt_b.ty),
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target,
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ty::error::TypeError::Mutability,
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)
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.emit();
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}
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(mt_a.ty, mt_b.ty, unsize_trait, None)
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};
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let (source, target, trait_def_id, kind) = match (source.kind(), target.kind()) {
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(&ty::Ref(r_a, ty_a, mutbl_a), &ty::Ref(r_b, ty_b, mutbl_b)) => {
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infcx.sub_regions(infer::RelateObjectBound(span), r_b, r_a);
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let mt_a = ty::TypeAndMut { ty: ty_a, mutbl: mutbl_a };
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let mt_b = ty::TypeAndMut { ty: ty_b, mutbl: mutbl_b };
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check_mutbl(mt_a, mt_b, &|ty| tcx.mk_imm_ref(r_b, ty))
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let infcx = tcx.infer_ctxt().build();
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let impl_hir_id = tcx.hir().local_def_id_to_hir_id(impl_did);
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let cause = ObligationCause::misc(span, impl_hir_id);
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let check_mutbl = |mt_a: ty::TypeAndMut<'tcx>,
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mt_b: ty::TypeAndMut<'tcx>,
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mk_ptr: &dyn Fn(Ty<'tcx>) -> Ty<'tcx>| {
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if (mt_a.mutbl, mt_b.mutbl) == (hir::Mutability::Not, hir::Mutability::Mut) {
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infcx
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.err_ctxt()
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.report_mismatched_types(
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&cause,
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mk_ptr(mt_b.ty),
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target,
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ty::error::TypeError::Mutability,
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)
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.emit();
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}
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(mt_a.ty, mt_b.ty, unsize_trait, None)
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};
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let (source, target, trait_def_id, kind) = match (source.kind(), target.kind()) {
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(&ty::Ref(r_a, ty_a, mutbl_a), &ty::Ref(r_b, ty_b, mutbl_b)) => {
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infcx.sub_regions(infer::RelateObjectBound(span), r_b, r_a);
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let mt_a = ty::TypeAndMut { ty: ty_a, mutbl: mutbl_a };
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let mt_b = ty::TypeAndMut { ty: ty_b, mutbl: mutbl_b };
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check_mutbl(mt_a, mt_b, &|ty| tcx.mk_imm_ref(r_b, ty))
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}
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(&ty::Ref(_, ty_a, mutbl_a), &ty::RawPtr(mt_b)) => {
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let mt_a = ty::TypeAndMut { ty: ty_a, mutbl: mutbl_a };
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check_mutbl(mt_a, mt_b, &|ty| tcx.mk_imm_ptr(ty))
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}
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(&ty::RawPtr(mt_a), &ty::RawPtr(mt_b)) => check_mutbl(mt_a, mt_b, &|ty| tcx.mk_imm_ptr(ty)),
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(&ty::Adt(def_a, substs_a), &ty::Adt(def_b, substs_b))
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if def_a.is_struct() && def_b.is_struct() =>
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{
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if def_a != def_b {
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let source_path = tcx.def_path_str(def_a.did());
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let target_path = tcx.def_path_str(def_b.did());
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struct_span_err!(
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tcx.sess,
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span,
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E0377,
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"the trait `CoerceUnsized` may only be implemented \
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for a coercion between structures with the same \
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definition; expected `{}`, found `{}`",
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source_path,
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target_path
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)
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.emit();
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return err_info;
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}
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(&ty::Ref(_, ty_a, mutbl_a), &ty::RawPtr(mt_b)) => {
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let mt_a = ty::TypeAndMut { ty: ty_a, mutbl: mutbl_a };
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check_mutbl(mt_a, mt_b, &|ty| tcx.mk_imm_ptr(ty))
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}
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// Here we are considering a case of converting
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// `S<P0...Pn>` to S<Q0...Qn>`. As an example, let's imagine a struct `Foo<T, U>`,
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// which acts like a pointer to `U`, but carries along some extra data of type `T`:
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//
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// struct Foo<T, U> {
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// extra: T,
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// ptr: *mut U,
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// }
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//
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// We might have an impl that allows (e.g.) `Foo<T, [i32; 3]>` to be unsized
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// to `Foo<T, [i32]>`. That impl would look like:
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//
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// impl<T, U: Unsize<V>, V> CoerceUnsized<Foo<T, V>> for Foo<T, U> {}
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//
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// Here `U = [i32; 3]` and `V = [i32]`. At runtime,
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// when this coercion occurs, we would be changing the
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// field `ptr` from a thin pointer of type `*mut [i32;
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// 3]` to a fat pointer of type `*mut [i32]` (with
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// extra data `3`). **The purpose of this check is to
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// make sure that we know how to do this conversion.**
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//
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// To check if this impl is legal, we would walk down
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||||
// the fields of `Foo` and consider their types with
|
||||
// both substitutes. We are looking to find that
|
||||
// exactly one (non-phantom) field has changed its
|
||||
// type, which we will expect to be the pointer that
|
||||
// is becoming fat (we could probably generalize this
|
||||
// to multiple thin pointers of the same type becoming
|
||||
// fat, but we don't). In this case:
|
||||
//
|
||||
// - `extra` has type `T` before and type `T` after
|
||||
// - `ptr` has type `*mut U` before and type `*mut V` after
|
||||
//
|
||||
// Since just one field changed, we would then check
|
||||
// that `*mut U: CoerceUnsized<*mut V>` is implemented
|
||||
// (in other words, that we know how to do this
|
||||
// conversion). This will work out because `U:
|
||||
// Unsize<V>`, and we have a builtin rule that `*mut
|
||||
// U` can be coerced to `*mut V` if `U: Unsize<V>`.
|
||||
let fields = &def_a.non_enum_variant().fields;
|
||||
let diff_fields = fields
|
||||
.iter()
|
||||
.enumerate()
|
||||
.filter_map(|(i, f)| {
|
||||
let (a, b) = (f.ty(tcx, substs_a), f.ty(tcx, substs_b));
|
||||
|
||||
(&ty::RawPtr(mt_a), &ty::RawPtr(mt_b)) => {
|
||||
check_mutbl(mt_a, mt_b, &|ty| tcx.mk_imm_ptr(ty))
|
||||
}
|
||||
if tcx.type_of(f.did).is_phantom_data() {
|
||||
// Ignore PhantomData fields
|
||||
return None;
|
||||
}
|
||||
|
||||
(&ty::Adt(def_a, substs_a), &ty::Adt(def_b, substs_b))
|
||||
if def_a.is_struct() && def_b.is_struct() =>
|
||||
{
|
||||
if def_a != def_b {
|
||||
let source_path = tcx.def_path_str(def_a.did());
|
||||
let target_path = tcx.def_path_str(def_b.did());
|
||||
struct_span_err!(
|
||||
tcx.sess,
|
||||
span,
|
||||
E0377,
|
||||
"the trait `CoerceUnsized` may only be implemented \
|
||||
for a coercion between structures with the same \
|
||||
definition; expected `{}`, found `{}`",
|
||||
source_path,
|
||||
target_path
|
||||
)
|
||||
.emit();
|
||||
return err_info;
|
||||
}
|
||||
|
||||
// Here we are considering a case of converting
|
||||
// `S<P0...Pn>` to S<Q0...Qn>`. As an example, let's imagine a struct `Foo<T, U>`,
|
||||
// which acts like a pointer to `U`, but carries along some extra data of type `T`:
|
||||
//
|
||||
// struct Foo<T, U> {
|
||||
// extra: T,
|
||||
// ptr: *mut U,
|
||||
// }
|
||||
//
|
||||
// We might have an impl that allows (e.g.) `Foo<T, [i32; 3]>` to be unsized
|
||||
// to `Foo<T, [i32]>`. That impl would look like:
|
||||
//
|
||||
// impl<T, U: Unsize<V>, V> CoerceUnsized<Foo<T, V>> for Foo<T, U> {}
|
||||
//
|
||||
// Here `U = [i32; 3]` and `V = [i32]`. At runtime,
|
||||
// when this coercion occurs, we would be changing the
|
||||
// field `ptr` from a thin pointer of type `*mut [i32;
|
||||
// 3]` to a fat pointer of type `*mut [i32]` (with
|
||||
// extra data `3`). **The purpose of this check is to
|
||||
// make sure that we know how to do this conversion.**
|
||||
//
|
||||
// To check if this impl is legal, we would walk down
|
||||
// the fields of `Foo` and consider their types with
|
||||
// both substitutes. We are looking to find that
|
||||
// exactly one (non-phantom) field has changed its
|
||||
// type, which we will expect to be the pointer that
|
||||
// is becoming fat (we could probably generalize this
|
||||
// to multiple thin pointers of the same type becoming
|
||||
// fat, but we don't). In this case:
|
||||
//
|
||||
// - `extra` has type `T` before and type `T` after
|
||||
// - `ptr` has type `*mut U` before and type `*mut V` after
|
||||
//
|
||||
// Since just one field changed, we would then check
|
||||
// that `*mut U: CoerceUnsized<*mut V>` is implemented
|
||||
// (in other words, that we know how to do this
|
||||
// conversion). This will work out because `U:
|
||||
// Unsize<V>`, and we have a builtin rule that `*mut
|
||||
// U` can be coerced to `*mut V` if `U: Unsize<V>`.
|
||||
let fields = &def_a.non_enum_variant().fields;
|
||||
let diff_fields = fields
|
||||
.iter()
|
||||
.enumerate()
|
||||
.filter_map(|(i, f)| {
|
||||
let (a, b) = (f.ty(tcx, substs_a), f.ty(tcx, substs_b));
|
||||
|
||||
if tcx.type_of(f.did).is_phantom_data() {
|
||||
// Ignore PhantomData fields
|
||||
// Ignore fields that aren't changed; it may
|
||||
// be that we could get away with subtyping or
|
||||
// something more accepting, but we use
|
||||
// equality because we want to be able to
|
||||
// perform this check without computing
|
||||
// variance where possible. (This is because
|
||||
// we may have to evaluate constraint
|
||||
// expressions in the course of execution.)
|
||||
// See e.g., #41936.
|
||||
if let Ok(ok) = infcx.at(&cause, param_env).eq(a, b) {
|
||||
if ok.obligations.is_empty() {
|
||||
return None;
|
||||
}
|
||||
}
|
||||
|
||||
// Ignore fields that aren't changed; it may
|
||||
// be that we could get away with subtyping or
|
||||
// something more accepting, but we use
|
||||
// equality because we want to be able to
|
||||
// perform this check without computing
|
||||
// variance where possible. (This is because
|
||||
// we may have to evaluate constraint
|
||||
// expressions in the course of execution.)
|
||||
// See e.g., #41936.
|
||||
if let Ok(ok) = infcx.at(&cause, param_env).eq(a, b) {
|
||||
if ok.obligations.is_empty() {
|
||||
return None;
|
||||
}
|
||||
}
|
||||
// Collect up all fields that were significantly changed
|
||||
// i.e., those that contain T in coerce_unsized T -> U
|
||||
Some((i, a, b))
|
||||
})
|
||||
.collect::<Vec<_>>();
|
||||
|
||||
// Collect up all fields that were significantly changed
|
||||
// i.e., those that contain T in coerce_unsized T -> U
|
||||
Some((i, a, b))
|
||||
})
|
||||
.collect::<Vec<_>>();
|
||||
|
||||
if diff_fields.is_empty() {
|
||||
struct_span_err!(
|
||||
tcx.sess,
|
||||
span,
|
||||
E0374,
|
||||
"the trait `CoerceUnsized` may only be implemented \
|
||||
for a coercion between structures with one field \
|
||||
being coerced, none found"
|
||||
)
|
||||
.emit();
|
||||
return err_info;
|
||||
} else if diff_fields.len() > 1 {
|
||||
let item = tcx.hir().expect_item(impl_did);
|
||||
let span = if let ItemKind::Impl(hir::Impl { of_trait: Some(ref t), .. }) =
|
||||
item.kind
|
||||
{
|
||||
if diff_fields.is_empty() {
|
||||
struct_span_err!(
|
||||
tcx.sess,
|
||||
span,
|
||||
E0374,
|
||||
"the trait `CoerceUnsized` may only be implemented \
|
||||
for a coercion between structures with one field \
|
||||
being coerced, none found"
|
||||
)
|
||||
.emit();
|
||||
return err_info;
|
||||
} else if diff_fields.len() > 1 {
|
||||
let item = tcx.hir().expect_item(impl_did);
|
||||
let span =
|
||||
if let ItemKind::Impl(hir::Impl { of_trait: Some(ref t), .. }) = item.kind {
|
||||
t.path.span
|
||||
} else {
|
||||
tcx.def_span(impl_did)
|
||||
};
|
||||
|
||||
struct_span_err!(
|
||||
tcx.sess,
|
||||
span,
|
||||
E0375,
|
||||
"implementing the trait \
|
||||
`CoerceUnsized` requires multiple \
|
||||
coercions"
|
||||
)
|
||||
.note(
|
||||
"`CoerceUnsized` may only be implemented for \
|
||||
a coercion between structures with one field being coerced",
|
||||
)
|
||||
.note(&format!(
|
||||
"currently, {} fields need coercions: {}",
|
||||
diff_fields.len(),
|
||||
diff_fields
|
||||
.iter()
|
||||
.map(|&(i, a, b)| {
|
||||
format!("`{}` (`{}` to `{}`)", fields[i].name, a, b)
|
||||
})
|
||||
.collect::<Vec<_>>()
|
||||
.join(", ")
|
||||
))
|
||||
.span_label(span, "requires multiple coercions")
|
||||
.emit();
|
||||
return err_info;
|
||||
}
|
||||
|
||||
let (i, a, b) = diff_fields[0];
|
||||
let kind = ty::adjustment::CustomCoerceUnsized::Struct(i);
|
||||
(a, b, coerce_unsized_trait, Some(kind))
|
||||
}
|
||||
|
||||
_ => {
|
||||
struct_span_err!(
|
||||
tcx.sess,
|
||||
span,
|
||||
E0376,
|
||||
"the trait `CoerceUnsized` may only be implemented \
|
||||
for a coercion between structures"
|
||||
E0375,
|
||||
"implementing the trait \
|
||||
`CoerceUnsized` requires multiple \
|
||||
coercions"
|
||||
)
|
||||
.note(
|
||||
"`CoerceUnsized` may only be implemented for \
|
||||
a coercion between structures with one field being coerced",
|
||||
)
|
||||
.note(&format!(
|
||||
"currently, {} fields need coercions: {}",
|
||||
diff_fields.len(),
|
||||
diff_fields
|
||||
.iter()
|
||||
.map(|&(i, a, b)| { format!("`{}` (`{}` to `{}`)", fields[i].name, a, b) })
|
||||
.collect::<Vec<_>>()
|
||||
.join(", ")
|
||||
))
|
||||
.span_label(span, "requires multiple coercions")
|
||||
.emit();
|
||||
return err_info;
|
||||
}
|
||||
};
|
||||
|
||||
// Register an obligation for `A: Trait<B>`.
|
||||
let cause = traits::ObligationCause::misc(span, impl_hir_id);
|
||||
let predicate = predicate_for_trait_def(
|
||||
tcx,
|
||||
param_env,
|
||||
cause,
|
||||
trait_def_id,
|
||||
0,
|
||||
source,
|
||||
&[target.into()],
|
||||
);
|
||||
let errors = traits::fully_solve_obligation(&infcx, predicate);
|
||||
if !errors.is_empty() {
|
||||
infcx.err_ctxt().report_fulfillment_errors(&errors, None, false);
|
||||
let (i, a, b) = diff_fields[0];
|
||||
let kind = ty::adjustment::CustomCoerceUnsized::Struct(i);
|
||||
(a, b, coerce_unsized_trait, Some(kind))
|
||||
}
|
||||
|
||||
// Finally, resolve all regions.
|
||||
let outlives_env = OutlivesEnvironment::new(param_env);
|
||||
infcx.check_region_obligations_and_report_errors(impl_did, &outlives_env);
|
||||
_ => {
|
||||
struct_span_err!(
|
||||
tcx.sess,
|
||||
span,
|
||||
E0376,
|
||||
"the trait `CoerceUnsized` may only be implemented \
|
||||
for a coercion between structures"
|
||||
)
|
||||
.emit();
|
||||
return err_info;
|
||||
}
|
||||
};
|
||||
|
||||
CoerceUnsizedInfo { custom_kind: kind }
|
||||
})
|
||||
// Register an obligation for `A: Trait<B>`.
|
||||
let cause = traits::ObligationCause::misc(span, impl_hir_id);
|
||||
let predicate =
|
||||
predicate_for_trait_def(tcx, param_env, cause, trait_def_id, 0, source, &[target.into()]);
|
||||
let errors = traits::fully_solve_obligation(&infcx, predicate);
|
||||
if !errors.is_empty() {
|
||||
infcx.err_ctxt().report_fulfillment_errors(&errors, None, false);
|
||||
}
|
||||
|
||||
// Finally, resolve all regions.
|
||||
let outlives_env = OutlivesEnvironment::new(param_env);
|
||||
infcx.check_region_obligations_and_report_errors(impl_did, &outlives_env);
|
||||
|
||||
CoerceUnsizedInfo { custom_kind: kind }
|
||||
}
|
||||
|
|
|
|||
Loading…
Add table
Add a link
Reference in a new issue