661 lines
26 KiB
Rust
661 lines
26 KiB
Rust
//! Check properties that are required by built-in traits and set
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//! up data structures required by type-checking/codegen.
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use std::assert_matches::assert_matches;
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use std::collections::BTreeMap;
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use rustc_data_structures::fx::FxHashSet;
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use rustc_errors::{ErrorGuaranteed, MultiSpan};
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use rustc_hir as hir;
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use rustc_hir::def_id::{DefId, LocalDefId};
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use rustc_hir::lang_items::LangItem;
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use rustc_hir::ItemKind;
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use rustc_infer::infer::outlives::env::OutlivesEnvironment;
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use rustc_infer::infer::{self, RegionResolutionError, TyCtxtInferExt};
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use rustc_infer::traits::Obligation;
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use rustc_middle::ty::adjustment::CoerceUnsizedInfo;
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use rustc_middle::ty::print::PrintTraitRefExt as _;
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use rustc_middle::ty::{self, suggest_constraining_type_params, Ty, TyCtxt, TypeVisitableExt};
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use rustc_span::{Span, DUMMY_SP};
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use rustc_trait_selection::error_reporting::InferCtxtErrorExt;
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use rustc_trait_selection::traits::misc::{
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type_allowed_to_implement_const_param_ty, type_allowed_to_implement_copy,
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ConstParamTyImplementationError, CopyImplementationError, InfringingFieldsReason,
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};
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use rustc_trait_selection::traits::{self, ObligationCause, ObligationCtxt};
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use tracing::debug;
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use crate::errors;
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pub(super) fn check_trait<'tcx>(
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tcx: TyCtxt<'tcx>,
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trait_def_id: DefId,
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impl_def_id: LocalDefId,
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impl_header: ty::ImplTraitHeader<'tcx>,
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) -> Result<(), ErrorGuaranteed> {
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let lang_items = tcx.lang_items();
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let checker = Checker { tcx, trait_def_id, impl_def_id, impl_header };
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let mut res = checker.check(lang_items.drop_trait(), visit_implementation_of_drop);
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res = res.and(checker.check(lang_items.copy_trait(), visit_implementation_of_copy));
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res = res.and(checker.check(lang_items.const_param_ty_trait(), |checker| {
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visit_implementation_of_const_param_ty(checker, LangItem::ConstParamTy)
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}));
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res = res.and(checker.check(lang_items.unsized_const_param_ty_trait(), |checker| {
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visit_implementation_of_const_param_ty(checker, LangItem::UnsizedConstParamTy)
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}));
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res = res.and(
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checker.check(lang_items.coerce_unsized_trait(), visit_implementation_of_coerce_unsized),
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);
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res.and(
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checker
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.check(lang_items.dispatch_from_dyn_trait(), visit_implementation_of_dispatch_from_dyn),
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)
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}
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struct Checker<'tcx> {
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tcx: TyCtxt<'tcx>,
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trait_def_id: DefId,
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impl_def_id: LocalDefId,
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impl_header: ty::ImplTraitHeader<'tcx>,
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}
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impl<'tcx> Checker<'tcx> {
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fn check(
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&self,
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trait_def_id: Option<DefId>,
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f: impl FnOnce(&Self) -> Result<(), ErrorGuaranteed>,
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) -> Result<(), ErrorGuaranteed> {
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if Some(self.trait_def_id) == trait_def_id { f(self) } else { Ok(()) }
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}
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}
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fn visit_implementation_of_drop(checker: &Checker<'_>) -> Result<(), ErrorGuaranteed> {
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let tcx = checker.tcx;
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let impl_did = checker.impl_def_id;
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// Destructors only work on local ADT types.
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match checker.impl_header.trait_ref.instantiate_identity().self_ty().kind() {
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ty::Adt(def, _) if def.did().is_local() => return Ok(()),
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ty::Error(_) => return Ok(()),
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_ => {}
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}
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let impl_ = tcx.hir().expect_item(impl_did).expect_impl();
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Err(tcx.dcx().emit_err(errors::DropImplOnWrongItem { span: impl_.self_ty.span }))
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}
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fn visit_implementation_of_copy(checker: &Checker<'_>) -> Result<(), ErrorGuaranteed> {
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let tcx = checker.tcx;
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let impl_header = checker.impl_header;
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let impl_did = checker.impl_def_id;
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debug!("visit_implementation_of_copy: impl_did={:?}", impl_did);
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let self_type = impl_header.trait_ref.instantiate_identity().self_ty();
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debug!("visit_implementation_of_copy: self_type={:?} (bound)", self_type);
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let param_env = tcx.param_env(impl_did);
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assert!(!self_type.has_escaping_bound_vars());
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debug!("visit_implementation_of_copy: self_type={:?} (free)", self_type);
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if let ty::ImplPolarity::Negative = impl_header.polarity {
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return Ok(());
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}
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let cause = traits::ObligationCause::misc(DUMMY_SP, impl_did);
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match type_allowed_to_implement_copy(tcx, param_env, self_type, cause) {
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Ok(()) => Ok(()),
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Err(CopyImplementationError::InfringingFields(fields)) => {
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let span = tcx.hir().expect_item(impl_did).expect_impl().self_ty.span;
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Err(infringing_fields_error(
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tcx,
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fields.into_iter().map(|(field, ty, reason)| (tcx.def_span(field.did), ty, reason)),
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LangItem::Copy,
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impl_did,
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span,
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))
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}
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Err(CopyImplementationError::NotAnAdt) => {
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let span = tcx.hir().expect_item(impl_did).expect_impl().self_ty.span;
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Err(tcx.dcx().emit_err(errors::CopyImplOnNonAdt { span }))
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}
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Err(CopyImplementationError::HasDestructor) => {
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let span = tcx.hir().expect_item(impl_did).expect_impl().self_ty.span;
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Err(tcx.dcx().emit_err(errors::CopyImplOnTypeWithDtor { span }))
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}
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}
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}
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fn visit_implementation_of_const_param_ty(
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checker: &Checker<'_>,
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kind: LangItem,
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) -> Result<(), ErrorGuaranteed> {
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assert_matches!(kind, LangItem::ConstParamTy | LangItem::UnsizedConstParamTy);
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let tcx = checker.tcx;
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let header = checker.impl_header;
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let impl_did = checker.impl_def_id;
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let self_type = header.trait_ref.instantiate_identity().self_ty();
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assert!(!self_type.has_escaping_bound_vars());
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let param_env = tcx.param_env(impl_did);
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if let ty::ImplPolarity::Negative | ty::ImplPolarity::Reservation = header.polarity {
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return Ok(());
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}
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let cause = traits::ObligationCause::misc(DUMMY_SP, impl_did);
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match type_allowed_to_implement_const_param_ty(tcx, param_env, self_type, kind, cause) {
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Ok(()) => Ok(()),
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Err(ConstParamTyImplementationError::InfrigingFields(fields)) => {
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let span = tcx.hir().expect_item(impl_did).expect_impl().self_ty.span;
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Err(infringing_fields_error(
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tcx,
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fields.into_iter().map(|(field, ty, reason)| (tcx.def_span(field.did), ty, reason)),
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LangItem::ConstParamTy,
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impl_did,
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span,
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))
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}
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Err(ConstParamTyImplementationError::NotAnAdtOrBuiltinAllowed) => {
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let span = tcx.hir().expect_item(impl_did).expect_impl().self_ty.span;
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Err(tcx.dcx().emit_err(errors::ConstParamTyImplOnNonAdt { span }))
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}
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Err(ConstParamTyImplementationError::InvalidInnerTyOfBuiltinTy(infringing_tys)) => {
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let span = tcx.hir().expect_item(impl_did).expect_impl().self_ty.span;
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Err(infringing_fields_error(
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tcx,
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infringing_tys.into_iter().map(|(ty, reason)| (span, ty, reason)),
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LangItem::ConstParamTy,
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impl_did,
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span,
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))
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}
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Err(ConstParamTyImplementationError::UnsizedConstParamsFeatureRequired) => {
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let span = tcx.hir().expect_item(impl_did).expect_impl().self_ty.span;
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Err(tcx.dcx().emit_err(errors::ConstParamTyImplOnUnsized { span }))
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}
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}
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}
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fn visit_implementation_of_coerce_unsized(checker: &Checker<'_>) -> Result<(), ErrorGuaranteed> {
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let tcx = checker.tcx;
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let impl_did = checker.impl_def_id;
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debug!("visit_implementation_of_coerce_unsized: impl_did={:?}", impl_did);
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// Just compute this for the side-effects, in particular reporting
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// errors; other parts of the code may demand it for the info of
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// course.
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let span = tcx.def_span(impl_did);
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tcx.at(span).ensure().coerce_unsized_info(impl_did)
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}
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fn visit_implementation_of_dispatch_from_dyn(checker: &Checker<'_>) -> Result<(), ErrorGuaranteed> {
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let tcx = checker.tcx;
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let impl_did = checker.impl_def_id;
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let trait_ref = checker.impl_header.trait_ref.instantiate_identity();
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debug!("visit_implementation_of_dispatch_from_dyn: impl_did={:?}", impl_did);
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let span = tcx.def_span(impl_did);
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let dispatch_from_dyn_trait = tcx.require_lang_item(LangItem::DispatchFromDyn, Some(span));
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let source = trait_ref.self_ty();
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assert!(!source.has_escaping_bound_vars());
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let target = {
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assert_eq!(trait_ref.def_id, dispatch_from_dyn_trait);
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trait_ref.args.type_at(1)
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};
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debug!("visit_implementation_of_dispatch_from_dyn: {:?} -> {:?}", source, target);
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let param_env = tcx.param_env(impl_did);
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let infcx = tcx.infer_ctxt().build();
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let cause = ObligationCause::misc(span, impl_did);
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// Later parts of the compiler rely on all DispatchFromDyn types to be ABI-compatible with raw
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// pointers. This is enforced here: we only allow impls for references, raw pointers, and things
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// that are effectively repr(transparent) newtypes around types that already hav a
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// DispatchedFromDyn impl. We cannot literally use repr(transparent) on those types since some
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// of them support an allocator, but we ensure that for the cases where the type implements this
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// trait, they *do* satisfy the repr(transparent) rules, and then we assume that everything else
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// in the compiler (in particular, all the call ABI logic) will treat them as repr(transparent)
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// even if they do not carry that attribute.
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use rustc_type_ir::TyKind::*;
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match (source.kind(), target.kind()) {
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(&Ref(r_a, _, mutbl_a), Ref(r_b, _, mutbl_b)) if r_a == *r_b && mutbl_a == *mutbl_b => {
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Ok(())
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}
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(&RawPtr(_, a_mutbl), &RawPtr(_, b_mutbl)) if a_mutbl == b_mutbl => Ok(()),
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(&Adt(def_a, args_a), &Adt(def_b, args_b)) if def_a.is_struct() && def_b.is_struct() => {
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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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return Err(tcx.dcx().emit_err(errors::DispatchFromDynCoercion {
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span,
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trait_name: "DispatchFromDyn",
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note: true,
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source_path,
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target_path,
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}));
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}
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let mut res = Ok(());
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if def_a.repr().c() || def_a.repr().packed() {
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res = Err(tcx.dcx().emit_err(errors::DispatchFromDynRepr { span }));
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}
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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, args_a);
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let ty_b = field.ty(tcx, args_b);
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if let Ok(layout) = tcx.layout_of(param_env.and(ty_a)) {
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if layout.is_1zst() {
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// ignore 1-ZST fields
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return false;
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}
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}
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if ty_a == ty_b {
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res = Err(tcx.dcx().emit_err(errors::DispatchFromDynZST {
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span,
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name: field.name,
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ty: ty_a,
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}));
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return false;
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}
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true
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})
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.collect::<Vec<_>>();
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if coerced_fields.is_empty() {
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res = Err(tcx.dcx().emit_err(errors::DispatchFromDynSingle {
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span,
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trait_name: "DispatchFromDyn",
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note: true,
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}));
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} else if coerced_fields.len() > 1 {
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res = Err(tcx.dcx().emit_err(errors::DispatchFromDynMulti {
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span,
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coercions_note: true,
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number: coerced_fields.len(),
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coercions: coerced_fields
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.iter()
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.map(|field| {
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format!(
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"`{}` (`{}` to `{}`)",
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field.name,
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field.ty(tcx, args_a),
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field.ty(tcx, args_b),
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)
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})
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.collect::<Vec<_>>()
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.join(", "),
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}));
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} else {
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let ocx = ObligationCtxt::new_with_diagnostics(&infcx);
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for field in coerced_fields {
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ocx.register_obligation(Obligation::new(
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tcx,
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cause.clone(),
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param_env,
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ty::TraitRef::new(
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tcx,
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dispatch_from_dyn_trait,
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[field.ty(tcx, args_a), field.ty(tcx, args_b)],
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),
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));
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}
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let errors = ocx.select_all_or_error();
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if !errors.is_empty() {
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res = Err(infcx.err_ctxt().report_fulfillment_errors(errors));
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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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res = res.and(ocx.resolve_regions_and_report_errors(impl_did, &outlives_env));
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}
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res
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}
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_ => Err(tcx
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.dcx()
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.emit_err(errors::CoerceUnsizedMay { span, trait_name: "DispatchFromDyn" })),
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}
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}
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pub(crate) fn coerce_unsized_info<'tcx>(
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tcx: TyCtxt<'tcx>,
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impl_did: LocalDefId,
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) -> Result<CoerceUnsizedInfo, ErrorGuaranteed> {
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debug!("compute_coerce_unsized_info(impl_did={:?})", impl_did);
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let span = tcx.def_span(impl_did);
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let coerce_unsized_trait = tcx.require_lang_item(LangItem::CoerceUnsized, Some(span));
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let unsize_trait = tcx.require_lang_item(LangItem::Unsize, Some(span));
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let source = tcx.type_of(impl_did).instantiate_identity();
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let trait_ref = tcx.impl_trait_ref(impl_did).unwrap().instantiate_identity();
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assert_eq!(trait_ref.def_id, coerce_unsized_trait);
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let target = trait_ref.args.type_at(1);
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debug!("visit_implementation_of_coerce_unsized: {:?} -> {:?} (bound)", source, target);
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let param_env = tcx.param_env(impl_did);
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assert!(!source.has_escaping_bound_vars());
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debug!("visit_implementation_of_coerce_unsized: {:?} -> {:?} (free)", source, target);
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let infcx = tcx.infer_ctxt().build();
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let cause = ObligationCause::misc(span, impl_did);
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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 {
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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| Ty::new_imm_ref(tcx, r_b, ty))
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}
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(&ty::Ref(_, ty_a, mutbl_a), &ty::RawPtr(ty_b, mutbl_b)) => check_mutbl(
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ty::TypeAndMut { ty: ty_a, mutbl: mutbl_a },
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ty::TypeAndMut { ty: ty_b, mutbl: mutbl_b },
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&|ty| Ty::new_imm_ptr(tcx, ty),
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),
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(&ty::RawPtr(ty_a, mutbl_a), &ty::RawPtr(ty_b, mutbl_b)) => check_mutbl(
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ty::TypeAndMut { ty: ty_a, mutbl: mutbl_a },
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ty::TypeAndMut { ty: ty_b, mutbl: mutbl_b },
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&|ty| Ty::new_imm_ptr(tcx, ty),
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),
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(&ty::Adt(def_a, args_a), &ty::Adt(def_b, args_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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return Err(tcx.dcx().emit_err(errors::DispatchFromDynSame {
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span,
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trait_name: "CoerceUnsized",
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note: true,
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source_path,
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target_path,
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}));
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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
|
|
// 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 generic parameters. 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_enumerated()
|
|
.filter_map(|(i, f)| {
|
|
let (a, b) = (f.ty(tcx, args_a), f.ty(tcx, args_b));
|
|
|
|
if tcx.type_of(f.did).instantiate_identity().is_phantom_data() {
|
|
// Ignore PhantomData fields
|
|
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 or constraining opaque types' hidden types.
|
|
// (This is because we may have to evaluate constraint
|
|
// expressions in the course of execution.)
|
|
// See e.g., #41936.
|
|
if a == b {
|
|
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<_>>();
|
|
|
|
if diff_fields.is_empty() {
|
|
return Err(tcx.dcx().emit_err(errors::CoerceUnsizedOneField {
|
|
span,
|
|
trait_name: "CoerceUnsized",
|
|
note: true,
|
|
}));
|
|
} 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(t), .. }) = &item.kind {
|
|
t.path.span
|
|
} else {
|
|
tcx.def_span(impl_did)
|
|
};
|
|
|
|
return Err(tcx.dcx().emit_err(errors::CoerceUnsizedMulti {
|
|
span,
|
|
coercions_note: true,
|
|
number: diff_fields.len(),
|
|
coercions: diff_fields
|
|
.iter()
|
|
.map(|&(i, a, b)| format!("`{}` (`{}` to `{}`)", fields[i].name, a, b))
|
|
.collect::<Vec<_>>()
|
|
.join(", "),
|
|
}));
|
|
}
|
|
|
|
let (i, a, b) = diff_fields[0];
|
|
let kind = ty::adjustment::CustomCoerceUnsized::Struct(i);
|
|
(a, b, coerce_unsized_trait, Some(kind))
|
|
}
|
|
|
|
_ => {
|
|
return Err(tcx
|
|
.dcx()
|
|
.emit_err(errors::DispatchFromDynStruct { span, trait_name: "CoerceUnsized" }));
|
|
}
|
|
};
|
|
|
|
// Register an obligation for `A: Trait<B>`.
|
|
let ocx = ObligationCtxt::new_with_diagnostics(&infcx);
|
|
let cause = traits::ObligationCause::misc(span, impl_did);
|
|
let obligation = Obligation::new(
|
|
tcx,
|
|
cause,
|
|
param_env,
|
|
ty::TraitRef::new(tcx, trait_def_id, [source, target]),
|
|
);
|
|
ocx.register_obligation(obligation);
|
|
let errors = ocx.select_all_or_error();
|
|
if !errors.is_empty() {
|
|
infcx.err_ctxt().report_fulfillment_errors(errors);
|
|
}
|
|
|
|
// Finally, resolve all regions.
|
|
let outlives_env = OutlivesEnvironment::new(param_env);
|
|
let _ = ocx.resolve_regions_and_report_errors(impl_did, &outlives_env);
|
|
|
|
Ok(CoerceUnsizedInfo { custom_kind: kind })
|
|
}
|
|
|
|
fn infringing_fields_error<'tcx>(
|
|
tcx: TyCtxt<'tcx>,
|
|
infringing_tys: impl Iterator<Item = (Span, Ty<'tcx>, InfringingFieldsReason<'tcx>)>,
|
|
lang_item: LangItem,
|
|
impl_did: LocalDefId,
|
|
impl_span: Span,
|
|
) -> ErrorGuaranteed {
|
|
let trait_did = tcx.require_lang_item(lang_item, Some(impl_span));
|
|
|
|
let trait_name = tcx.def_path_str(trait_did);
|
|
|
|
// We'll try to suggest constraining type parameters to fulfill the requirements of
|
|
// their `Copy` implementation.
|
|
let mut errors: BTreeMap<_, Vec<_>> = Default::default();
|
|
let mut bounds = vec![];
|
|
|
|
let mut seen_tys = FxHashSet::default();
|
|
|
|
let mut label_spans = Vec::new();
|
|
|
|
for (span, ty, reason) in infringing_tys {
|
|
// Only report an error once per type.
|
|
if !seen_tys.insert(ty) {
|
|
continue;
|
|
}
|
|
|
|
label_spans.push(span);
|
|
|
|
match reason {
|
|
InfringingFieldsReason::Fulfill(fulfillment_errors) => {
|
|
for error in fulfillment_errors {
|
|
let error_predicate = error.obligation.predicate;
|
|
// Only note if it's not the root obligation, otherwise it's trivial and
|
|
// should be self-explanatory (i.e. a field literally doesn't implement Copy).
|
|
|
|
// FIXME: This error could be more descriptive, especially if the error_predicate
|
|
// contains a foreign type or if it's a deeply nested type...
|
|
if error_predicate != error.root_obligation.predicate {
|
|
errors
|
|
.entry((ty.to_string(), error_predicate.to_string()))
|
|
.or_default()
|
|
.push(error.obligation.cause.span);
|
|
}
|
|
if let ty::PredicateKind::Clause(ty::ClauseKind::Trait(ty::TraitPredicate {
|
|
trait_ref,
|
|
polarity: ty::PredicatePolarity::Positive,
|
|
..
|
|
})) = error_predicate.kind().skip_binder()
|
|
{
|
|
let ty = trait_ref.self_ty();
|
|
if let ty::Param(_) = ty.kind() {
|
|
bounds.push((
|
|
format!("{ty}"),
|
|
trait_ref.print_trait_sugared().to_string(),
|
|
Some(trait_ref.def_id),
|
|
));
|
|
}
|
|
}
|
|
}
|
|
}
|
|
InfringingFieldsReason::Regions(region_errors) => {
|
|
for error in region_errors {
|
|
let ty = ty.to_string();
|
|
match error {
|
|
RegionResolutionError::ConcreteFailure(origin, a, b) => {
|
|
let predicate = format!("{b}: {a}");
|
|
errors
|
|
.entry((ty.clone(), predicate.clone()))
|
|
.or_default()
|
|
.push(origin.span());
|
|
if let ty::RegionKind::ReEarlyParam(ebr) = *b
|
|
&& ebr.has_name()
|
|
{
|
|
bounds.push((b.to_string(), a.to_string(), None));
|
|
}
|
|
}
|
|
RegionResolutionError::GenericBoundFailure(origin, a, b) => {
|
|
let predicate = format!("{a}: {b}");
|
|
errors
|
|
.entry((ty.clone(), predicate.clone()))
|
|
.or_default()
|
|
.push(origin.span());
|
|
if let infer::region_constraints::GenericKind::Param(_) = a {
|
|
bounds.push((a.to_string(), b.to_string(), None));
|
|
}
|
|
}
|
|
_ => continue,
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
let mut notes = Vec::new();
|
|
for ((ty, error_predicate), spans) in errors {
|
|
let span: MultiSpan = spans.into();
|
|
notes.push(errors::ImplForTyRequires {
|
|
span,
|
|
error_predicate,
|
|
trait_name: trait_name.clone(),
|
|
ty,
|
|
});
|
|
}
|
|
|
|
let mut err = tcx.dcx().create_err(errors::TraitCannotImplForTy {
|
|
span: impl_span,
|
|
trait_name,
|
|
label_spans,
|
|
notes,
|
|
});
|
|
|
|
suggest_constraining_type_params(
|
|
tcx,
|
|
tcx.hir().get_generics(impl_did).expect("impls always have generics"),
|
|
&mut err,
|
|
bounds
|
|
.iter()
|
|
.map(|(param, constraint, def_id)| (param.as_str(), constraint.as_str(), *def_id)),
|
|
None,
|
|
);
|
|
|
|
err.emit()
|
|
}
|