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-rw-r--r--compiler/rustc_typeck/src/coherence/builtin.rs603
1 files changed, 0 insertions, 603 deletions
diff --git a/compiler/rustc_typeck/src/coherence/builtin.rs b/compiler/rustc_typeck/src/coherence/builtin.rs
deleted file mode 100644
index 50946cc1d..000000000
--- a/compiler/rustc_typeck/src/coherence/builtin.rs
+++ /dev/null
@@ -1,603 +0,0 @@
-//! Check properties that are required by built-in traits and set
-//! up data structures required by type-checking/codegen.
-
-use crate::errors::{CopyImplOnNonAdt, CopyImplOnTypeWithDtor, DropImplOnWrongItem};
-use rustc_errors::{struct_span_err, MultiSpan};
-use rustc_hir as hir;
-use rustc_hir::def_id::{DefId, LocalDefId};
-use rustc_hir::lang_items::LangItem;
-use rustc_hir::ItemKind;
-use rustc_infer::infer;
-use rustc_infer::infer::outlives::env::OutlivesEnvironment;
-use rustc_infer::infer::TyCtxtInferExt;
-use rustc_middle::ty::adjustment::CoerceUnsizedInfo;
-use rustc_middle::ty::{self, suggest_constraining_type_params, Ty, TyCtxt, TypeVisitable};
-use rustc_trait_selection::traits::error_reporting::InferCtxtExt;
-use rustc_trait_selection::traits::misc::{can_type_implement_copy, CopyImplementationError};
-use rustc_trait_selection::traits::predicate_for_trait_def;
-use rustc_trait_selection::traits::{self, ObligationCause, TraitEngine, TraitEngineExt};
-use std::collections::BTreeMap;
-
-pub fn check_trait(tcx: TyCtxt<'_>, trait_def_id: DefId) {
- let lang_items = tcx.lang_items();
- Checker { tcx, trait_def_id }
- .check(lang_items.drop_trait(), visit_implementation_of_drop)
- .check(lang_items.copy_trait(), visit_implementation_of_copy)
- .check(lang_items.coerce_unsized_trait(), visit_implementation_of_coerce_unsized)
- .check(lang_items.dispatch_from_dyn_trait(), visit_implementation_of_dispatch_from_dyn);
-}
-
-struct Checker<'tcx> {
- tcx: TyCtxt<'tcx>,
- trait_def_id: DefId,
-}
-
-impl<'tcx> Checker<'tcx> {
- fn check<F>(&self, trait_def_id: Option<DefId>, mut f: F) -> &Self
- where
- F: FnMut(TyCtxt<'tcx>, LocalDefId),
- {
- if Some(self.trait_def_id) == trait_def_id {
- for &impl_def_id in self.tcx.hir().trait_impls(self.trait_def_id) {
- f(self.tcx, impl_def_id);
- }
- }
- self
- }
-}
-
-fn visit_implementation_of_drop(tcx: TyCtxt<'_>, impl_did: LocalDefId) {
- // Destructors only work on nominal types.
- if let ty::Adt(..) | ty::Error(_) = tcx.type_of(impl_did).kind() {
- return;
- }
-
- let sp = match tcx.hir().expect_item(impl_did).kind {
- ItemKind::Impl(ref impl_) => impl_.self_ty.span,
- _ => bug!("expected Drop impl item"),
- };
-
- tcx.sess.emit_err(DropImplOnWrongItem { span: sp });
-}
-
-fn visit_implementation_of_copy(tcx: TyCtxt<'_>, impl_did: LocalDefId) {
- debug!("visit_implementation_of_copy: impl_did={:?}", impl_did);
-
- let impl_hir_id = tcx.hir().local_def_id_to_hir_id(impl_did);
-
- let self_type = tcx.type_of(impl_did);
- debug!("visit_implementation_of_copy: self_type={:?} (bound)", self_type);
-
- let span = tcx.hir().span(impl_hir_id);
- let param_env = tcx.param_env(impl_did);
- assert!(!self_type.has_escaping_bound_vars());
-
- debug!("visit_implementation_of_copy: self_type={:?} (free)", self_type);
-
- let cause = traits::ObligationCause::misc(span, impl_hir_id);
- match can_type_implement_copy(tcx, param_env, self_type, cause) {
- Ok(()) => {}
- Err(CopyImplementationError::InfrigingFields(fields)) => {
- let item = tcx.hir().expect_item(impl_did);
- let span = if let ItemKind::Impl(hir::Impl { of_trait: Some(ref tr), .. }) = item.kind {
- tr.path.span
- } else {
- span
- };
-
- let mut err = struct_span_err!(
- tcx.sess,
- span,
- E0204,
- "the trait `Copy` may not be implemented for this type"
- );
-
- // 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![];
-
- for (field, ty) in fields {
- let field_span = tcx.def_span(field.did);
- let field_ty_span = match tcx.hir().get_if_local(field.did) {
- Some(hir::Node::Field(field_def)) => field_def.ty.span,
- _ => field_span,
- };
- err.span_label(field_span, "this field does not implement `Copy`");
- // Spin up a new FulfillmentContext, so we can get the _precise_ reason
- // why this field does not implement Copy. This is useful because sometimes
- // it is not immediately clear why Copy is not implemented for a field, since
- // all we point at is the field itself.
- tcx.infer_ctxt().ignoring_regions().enter(|infcx| {
- let mut fulfill_cx = <dyn TraitEngine<'_>>::new(tcx);
- fulfill_cx.register_bound(
- &infcx,
- param_env,
- ty,
- tcx.lang_items().copy_trait().unwrap(),
- traits::ObligationCause::dummy_with_span(field_ty_span),
- );
- for error in fulfill_cx.select_all_or_error(&infcx) {
- 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::Trait(ty::TraitPredicate {
- trait_ref,
- polarity: ty::ImplPolarity::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_only_trait_path().to_string(),
- Some(trait_ref.def_id),
- ));
- }
- }
- }
- });
- }
- for ((ty, error_predicate), spans) in errors {
- let span: MultiSpan = spans.into();
- err.span_note(
- span,
- &format!("the `Copy` impl for `{}` requires that `{}`", ty, error_predicate),
- );
- }
- 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)
- }),
- );
- err.emit();
- }
- Err(CopyImplementationError::NotAnAdt) => {
- let item = tcx.hir().expect_item(impl_did);
- let span =
- if let ItemKind::Impl(ref impl_) = item.kind { impl_.self_ty.span } else { span };
-
- tcx.sess.emit_err(CopyImplOnNonAdt { span });
- }
- Err(CopyImplementationError::HasDestructor) => {
- tcx.sess.emit_err(CopyImplOnTypeWithDtor { span });
- }
- }
-}
-
-fn visit_implementation_of_coerce_unsized<'tcx>(tcx: TyCtxt<'tcx>, impl_did: LocalDefId) {
- debug!("visit_implementation_of_coerce_unsized: impl_did={:?}", impl_did);
-
- // Just compute this for the side-effects, in particular reporting
- // errors; other parts of the code may demand it for the info of
- // course.
- let span = tcx.def_span(impl_did);
- tcx.at(span).coerce_unsized_info(impl_did);
-}
-
-fn visit_implementation_of_dispatch_from_dyn<'tcx>(tcx: TyCtxt<'tcx>, impl_did: LocalDefId) {
- debug!("visit_implementation_of_dispatch_from_dyn: impl_did={:?}", impl_did);
-
- let impl_hir_id = tcx.hir().local_def_id_to_hir_id(impl_did);
- let span = tcx.hir().span(impl_hir_id);
-
- let dispatch_from_dyn_trait = tcx.require_lang_item(LangItem::DispatchFromDyn, Some(span));
-
- let source = tcx.type_of(impl_did);
- assert!(!source.has_escaping_bound_vars());
- let target = {
- let trait_ref = tcx.impl_trait_ref(impl_did).unwrap();
- assert_eq!(trait_ref.def_id, dispatch_from_dyn_trait);
-
- trait_ref.substs.type_at(1)
- };
-
- debug!("visit_implementation_of_dispatch_from_dyn: {:?} -> {:?}", source, target);
-
- let param_env = tcx.param_env(impl_did);
-
- let create_err = |msg: &str| struct_span_err!(tcx.sess, span, E0378, "{}", msg);
-
- tcx.infer_ctxt().enter(|infcx| {
- let cause = ObligationCause::misc(span, impl_hir_id);
-
- use rustc_type_ir::sty::TyKind::*;
- match (source.kind(), target.kind()) {
- (&Ref(r_a, _, mutbl_a), Ref(r_b, _, mutbl_b))
- if infcx.at(&cause, param_env).eq(r_a, *r_b).is_ok() && mutbl_a == *mutbl_b => {}
- (&RawPtr(tm_a), &RawPtr(tm_b)) if tm_a.mutbl == tm_b.mutbl => (),
- (&Adt(def_a, substs_a), &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());
-
- create_err(&format!(
- "the trait `DispatchFromDyn` may only be implemented \
- for a coercion between structures with the same \
- definition; expected `{}`, found `{}`",
- source_path, target_path,
- ))
- .emit();
-
- return;
- }
-
- if def_a.repr().c() || def_a.repr().packed() {
- create_err(
- "structs implementing `DispatchFromDyn` may not have \
- `#[repr(packed)]` or `#[repr(C)]`",
- )
- .emit();
- }
-
- let fields = &def_a.non_enum_variant().fields;
-
- let coerced_fields = fields
- .iter()
- .filter(|field| {
- let ty_a = field.ty(tcx, substs_a);
- let ty_b = field.ty(tcx, substs_b);
-
- if let Ok(layout) = tcx.layout_of(param_env.and(ty_a)) {
- if layout.is_zst() && layout.align.abi.bytes() == 1 {
- // ignore ZST fields with alignment of 1 byte
- return false;
- }
- }
-
- if let Ok(ok) = infcx.at(&cause, param_env).eq(ty_a, ty_b) {
- if ok.obligations.is_empty() {
- create_err(
- "the trait `DispatchFromDyn` may only be implemented \
- for structs containing the field being coerced, \
- ZST fields with 1 byte alignment, and nothing else",
- )
- .note(&format!(
- "extra field `{}` of type `{}` is not allowed",
- field.name, ty_a,
- ))
- .emit();
-
- return false;
- }
- }
-
- return true;
- })
- .collect::<Vec<_>>();
-
- if coerced_fields.is_empty() {
- create_err(
- "the trait `DispatchFromDyn` may only be implemented \
- for a coercion between structures with a single field \
- being coerced, none found",
- )
- .emit();
- } else if coerced_fields.len() > 1 {
- create_err(
- "implementing the `DispatchFromDyn` trait requires multiple coercions",
- )
- .note(
- "the trait `DispatchFromDyn` may only be implemented \
- for a coercion between structures with a single field \
- being coerced",
- )
- .note(&format!(
- "currently, {} fields need coercions: {}",
- coerced_fields.len(),
- coerced_fields
- .iter()
- .map(|field| {
- format!(
- "`{}` (`{}` to `{}`)",
- field.name,
- field.ty(tcx, substs_a),
- field.ty(tcx, substs_b),
- )
- })
- .collect::<Vec<_>>()
- .join(", ")
- ))
- .emit();
- } else {
- let mut fulfill_cx = <dyn TraitEngine<'_>>::new(infcx.tcx);
-
- for field in coerced_fields {
- let predicate = predicate_for_trait_def(
- tcx,
- param_env,
- cause.clone(),
- dispatch_from_dyn_trait,
- 0,
- field.ty(tcx, substs_a),
- &[field.ty(tcx, substs_b).into()],
- );
-
- fulfill_cx.register_predicate_obligation(&infcx, predicate);
- }
-
- // Check that all transitive obligations are satisfied.
- let errors = fulfill_cx.select_all_or_error(&infcx);
- if !errors.is_empty() {
- infcx.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);
- }
- }
- _ => {
- create_err(
- "the trait `DispatchFromDyn` may only be implemented \
- for a coercion between structures",
- )
- .emit();
- }
- }
- })
-}
-
-pub fn coerce_unsized_info<'tcx>(tcx: TyCtxt<'tcx>, impl_did: DefId) -> CoerceUnsizedInfo {
- debug!("compute_coerce_unsized_info(impl_did={:?})", impl_did);
-
- // this provider should only get invoked for local def-ids
- let impl_did = impl_did.expect_local();
- let span = tcx.def_span(impl_did);
-
- let coerce_unsized_trait = tcx.require_lang_item(LangItem::CoerceUnsized, Some(span));
-
- let unsize_trait = tcx.lang_items().require(LangItem::Unsize).unwrap_or_else(|err| {
- tcx.sess.fatal(&format!("`CoerceUnsized` implementation {}", err));
- });
-
- let source = tcx.type_of(impl_did);
- let trait_ref = tcx.impl_trait_ref(impl_did).unwrap();
- assert_eq!(trait_ref.def_id, coerce_unsized_trait);
- let target = trait_ref.substs.type_at(1);
- debug!("visit_implementation_of_coerce_unsized: {:?} -> {:?} (bound)", source, target);
-
- let param_env = tcx.param_env(impl_did);
- assert!(!source.has_escaping_bound_vars());
-
- let err_info = CoerceUnsizedInfo { custom_kind: None };
-
- debug!("visit_implementation_of_coerce_unsized: {:?} -> {:?} (free)", source, target);
-
- tcx.infer_ctxt().enter(|infcx| {
- let impl_hir_id = tcx.hir().local_def_id_to_hir_id(impl_did);
- let cause = ObligationCause::misc(span, impl_hir_id);
- let check_mutbl = |mt_a: ty::TypeAndMut<'tcx>,
- mt_b: ty::TypeAndMut<'tcx>,
- mk_ptr: &dyn Fn(Ty<'tcx>) -> Ty<'tcx>| {
- if (mt_a.mutbl, mt_b.mutbl) == (hir::Mutability::Not, hir::Mutability::Mut) {
- infcx
- .report_mismatched_types(
- &cause,
- mk_ptr(mt_b.ty),
- target,
- ty::error::TypeError::Mutability,
- )
- .emit();
- }
- (mt_a.ty, mt_b.ty, unsize_trait, None)
- };
- let (source, target, trait_def_id, kind) = match (source.kind(), target.kind()) {
- (&ty::Ref(r_a, ty_a, mutbl_a), &ty::Ref(r_b, ty_b, mutbl_b)) => {
- infcx.sub_regions(infer::RelateObjectBound(span), r_b, r_a);
- let mt_a = ty::TypeAndMut { ty: ty_a, mutbl: mutbl_a };
- let mt_b = ty::TypeAndMut { ty: ty_b, mutbl: mutbl_b };
- check_mutbl(mt_a, mt_b, &|ty| tcx.mk_imm_ref(r_b, ty))
- }
-
- (&ty::Ref(_, ty_a, mutbl_a), &ty::RawPtr(mt_b)) => {
- let mt_a = ty::TypeAndMut { ty: ty_a, mutbl: mutbl_a };
- check_mutbl(mt_a, mt_b, &|ty| tcx.mk_imm_ptr(ty))
- }
-
- (&ty::RawPtr(mt_a), &ty::RawPtr(mt_b)) => {
- check_mutbl(mt_a, mt_b, &|ty| tcx.mk_imm_ptr(ty))
- }
-
- (&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
- 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<_>>();
-
- 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"
- )
- .emit();
- return err_info;
- }
- };
-
- let mut fulfill_cx = <dyn TraitEngine<'_>>::new(infcx.tcx);
-
- // 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()],
- );
- fulfill_cx.register_predicate_obligation(&infcx, predicate);
-
- // Check that all transitive obligations are satisfied.
- let errors = fulfill_cx.select_all_or_error(&infcx);
- if !errors.is_empty() {
- infcx.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 }
- })
-}
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