wf: refactor compute_trait_ref
This commit is contained in:
Bastian Kauschke
parent
39b62533c7
commit
ab4178bd7d
@ -134,6 +134,152 @@ enum Elaborate {
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None,
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}
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fn extend_cause_with_original_assoc_item_obligation<'tcx>(
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tcx: TyCtxt<'tcx>,
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trait_ref: &ty::TraitRef<'tcx>,
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item: Option<&hir::Item<'tcx>>,
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cause: &mut traits::ObligationCause<'tcx>,
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pred: &ty::Predicate<'_>,
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mut trait_assoc_items: impl Iterator<Item = ty::AssocItem>,
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) {
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let trait_item =
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tcx.hir().as_local_hir_id(trait_ref.def_id).and_then(|trait_id| tcx.hir().find(trait_id));
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let (trait_name, trait_generics) = match trait_item {
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Some(hir::Node::Item(hir::Item {
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ident,
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kind: hir::ItemKind::Trait(.., generics, _, _),
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..
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}))
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| Some(hir::Node::Item(hir::Item {
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ident,
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kind: hir::ItemKind::TraitAlias(generics, _),
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..
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})) => (Some(ident), Some(generics)),
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_ => (None, None),
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};
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let item_span = item.map(|i| tcx.sess.source_map().guess_head_span(i.span));
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match pred {
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ty::Predicate::Projection(proj) => {
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// The obligation comes not from the current `impl` nor the `trait` being
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// implemented, but rather from a "second order" obligation, like in
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// `src/test/ui/associated-types/point-at-type-on-obligation-failure.rs`:
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//
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// error[E0271]: type mismatch resolving `<Foo2 as Bar2>::Ok == ()`
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// --> $DIR/point-at-type-on-obligation-failure.rs:13:5
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// |
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// LL | type Ok;
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// | -- associated type defined here
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// ...
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// LL | impl Bar for Foo {
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// | ---------------- in this `impl` item
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// LL | type Ok = ();
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// | ^^^^^^^^^^^^^ expected `u32`, found `()`
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// |
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// = note: expected type `u32`
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// found type `()`
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//
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// FIXME: we would want to point a span to all places that contributed to this
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// obligation. In the case above, it should be closer to:
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//
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// error[E0271]: type mismatch resolving `<Foo2 as Bar2>::Ok == ()`
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// --> $DIR/point-at-type-on-obligation-failure.rs:13:5
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// |
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// LL | type Ok;
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// | -- associated type defined here
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// LL | type Sibling: Bar2<Ok=Self::Ok>;
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// | -------------------------------- obligation set here
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// ...
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// LL | impl Bar for Foo {
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// | ---------------- in this `impl` item
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// LL | type Ok = ();
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// | ^^^^^^^^^^^^^ expected `u32`, found `()`
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// ...
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// LL | impl Bar2 for Foo2 {
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// | ---------------- in this `impl` item
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// LL | type Ok = u32;
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// | -------------- obligation set here
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// |
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// = note: expected type `u32`
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// found type `()`
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if let Some(hir::ItemKind::Impl { items, .. }) = item.map(|i| &i.kind) {
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let trait_assoc_item = tcx.associated_item(proj.projection_def_id());
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if let Some(impl_item) =
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items.iter().find(|item| item.ident == trait_assoc_item.ident)
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{
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cause.span = impl_item.span;
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cause.code = traits::AssocTypeBound(Box::new(AssocTypeBoundData {
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impl_span: item_span,
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original: trait_assoc_item.ident.span,
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bounds: vec![],
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}));
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}
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}
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}
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ty::Predicate::Trait(proj, _) => {
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// An associated item obligation born out of the `trait` failed to be met.
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// Point at the `impl` that failed the obligation, the associated item that
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// needed to meet the obligation, and the definition of that associated item,
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// which should hold the obligation in most cases. An example can be seen in
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// `src/test/ui/associated-types/point-at-type-on-obligation-failure-2.rs`:
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//
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// error[E0277]: the trait bound `bool: Bar` is not satisfied
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// --> $DIR/point-at-type-on-obligation-failure-2.rs:8:5
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// |
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// LL | type Assoc: Bar;
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// | ----- associated type defined here
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// ...
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// LL | impl Foo for () {
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// | --------------- in this `impl` item
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// LL | type Assoc = bool;
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// | ^^^^^^^^^^^^^^^^^^ the trait `Bar` is not implemented for `bool`
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//
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// If the obligation comes from the where clause in the `trait`, we point at it:
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//
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// error[E0277]: the trait bound `bool: Bar` is not satisfied
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// --> $DIR/point-at-type-on-obligation-failure-2.rs:8:5
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// |
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// | trait Foo where <Self as Foo>>::Assoc: Bar {
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// | -------------------------- restricted in this bound
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// LL | type Assoc;
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// | ----- associated type defined here
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// ...
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// LL | impl Foo for () {
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// | --------------- in this `impl` item
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// LL | type Assoc = bool;
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// | ^^^^^^^^^^^^^^^^^^ the trait `Bar` is not implemented for `bool`
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if let (
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ty::Projection(ty::ProjectionTy { item_def_id, .. }),
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Some(hir::ItemKind::Impl { items, .. }),
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) = (&proj.skip_binder().self_ty().kind, item.map(|i| &i.kind))
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{
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if let Some((impl_item, trait_assoc_item)) = trait_assoc_items
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.find(|i| i.def_id == *item_def_id)
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.and_then(|trait_assoc_item| {
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items
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.iter()
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.find(|i| i.ident == trait_assoc_item.ident)
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.map(|impl_item| (impl_item, trait_assoc_item))
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})
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{
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let bounds = trait_generics
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.map(|generics| {
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get_generic_bound_spans(&generics, trait_name, trait_assoc_item.ident)
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})
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.unwrap_or_else(Vec::new);
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cause.span = impl_item.span;
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cause.code = traits::AssocTypeBound(Box::new(AssocTypeBoundData {
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impl_span: item_span,
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original: trait_assoc_item.ident.span,
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bounds,
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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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}
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impl<'a, 'tcx> WfPredicates<'a, 'tcx> {
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fn cause(&mut self, code: traits::ObligationCauseCode<'tcx>) -> traits::ObligationCause<'tcx> {
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traits::ObligationCause::new(self.span, self.body_id, code)
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@ -163,170 +309,20 @@ fn compute_trait_ref(&mut self, trait_ref: &ty::TraitRef<'tcx>, elaborate: Elabo
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let cause = self.cause(traits::MiscObligation);
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let param_env = self.param_env;
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let item = &self.item;
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let extend_cause_with_original_assoc_item_obligation =
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|cause: &mut traits::ObligationCause<'_>,
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pred: &ty::Predicate<'_>,
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trait_assoc_items: &[ty::AssocItem]| {
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let trait_item = tcx
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.hir()
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.as_local_hir_id(trait_ref.def_id)
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.and_then(|trait_id| tcx.hir().find(trait_id));
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let (trait_name, trait_generics) = match trait_item {
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Some(hir::Node::Item(hir::Item {
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ident,
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kind: hir::ItemKind::Trait(.., generics, _, _),
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..
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}))
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| Some(hir::Node::Item(hir::Item {
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ident,
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kind: hir::ItemKind::TraitAlias(generics, _),
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..
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})) => (Some(ident), Some(generics)),
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_ => (None, None),
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};
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let item_span = item.map(|i| tcx.sess.source_map().guess_head_span(i.span));
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match pred {
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ty::Predicate::Projection(proj) => {
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// The obligation comes not from the current `impl` nor the `trait` being
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// implemented, but rather from a "second order" obligation, like in
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// `src/test/ui/associated-types/point-at-type-on-obligation-failure.rs`:
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//
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// error[E0271]: type mismatch resolving `<Foo2 as Bar2>::Ok == ()`
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// --> $DIR/point-at-type-on-obligation-failure.rs:13:5
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// |
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// LL | type Ok;
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// | -- associated type defined here
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// ...
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// LL | impl Bar for Foo {
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// | ---------------- in this `impl` item
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// LL | type Ok = ();
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// | ^^^^^^^^^^^^^ expected `u32`, found `()`
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// |
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// = note: expected type `u32`
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// found type `()`
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//
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// FIXME: we would want to point a span to all places that contributed to this
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// obligation. In the case above, it should be closer to:
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//
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// error[E0271]: type mismatch resolving `<Foo2 as Bar2>::Ok == ()`
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// --> $DIR/point-at-type-on-obligation-failure.rs:13:5
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// |
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// LL | type Ok;
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// | -- associated type defined here
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// LL | type Sibling: Bar2<Ok=Self::Ok>;
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// | -------------------------------- obligation set here
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// ...
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// LL | impl Bar for Foo {
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// | ---------------- in this `impl` item
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// LL | type Ok = ();
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// | ^^^^^^^^^^^^^ expected `u32`, found `()`
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// ...
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// LL | impl Bar2 for Foo2 {
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// | ---------------- in this `impl` item
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// LL | type Ok = u32;
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// | -------------- obligation set here
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// |
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// = note: expected type `u32`
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// found type `()`
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if let Some(hir::ItemKind::Impl { items, .. }) = item.map(|i| &i.kind) {
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let trait_assoc_item = tcx.associated_item(proj.projection_def_id());
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if let Some(impl_item) =
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items.iter().find(|item| item.ident == trait_assoc_item.ident)
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{
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cause.span = impl_item.span;
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cause.code = traits::AssocTypeBound(Box::new(AssocTypeBoundData {
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impl_span: item_span,
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original: trait_assoc_item.ident.span,
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bounds: vec![],
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}));
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}
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}
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}
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ty::Predicate::Trait(proj, _) => {
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// An associated item obligation born out of the `trait` failed to be met.
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// Point at the `impl` that failed the obligation, the associated item that
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// needed to meet the obligation, and the definition of that associated item,
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// which should hold the obligation in most cases. An example can be seen in
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// `src/test/ui/associated-types/point-at-type-on-obligation-failure-2.rs`:
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//
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// error[E0277]: the trait bound `bool: Bar` is not satisfied
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// --> $DIR/point-at-type-on-obligation-failure-2.rs:8:5
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// |
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// LL | type Assoc: Bar;
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// | ----- associated type defined here
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// ...
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// LL | impl Foo for () {
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// | --------------- in this `impl` item
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// LL | type Assoc = bool;
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// | ^^^^^^^^^^^^^^^^^^ the trait `Bar` is not implemented for `bool`
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//
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// If the obligation comes from the where clause in the `trait`, we point at it:
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//
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// error[E0277]: the trait bound `bool: Bar` is not satisfied
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// --> $DIR/point-at-type-on-obligation-failure-2.rs:8:5
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// |
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// | trait Foo where <Self as Foo>>::Assoc: Bar {
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// | -------------------------- restricted in this bound
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// LL | type Assoc;
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// | ----- associated type defined here
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// ...
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// LL | impl Foo for () {
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// | --------------- in this `impl` item
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// LL | type Assoc = bool;
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// | ^^^^^^^^^^^^^^^^^^ the trait `Bar` is not implemented for `bool`
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if let (
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ty::Projection(ty::ProjectionTy { item_def_id, .. }),
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Some(hir::ItemKind::Impl { items, .. }),
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) = (&proj.skip_binder().self_ty().kind, item.map(|i| &i.kind))
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{
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if let Some((impl_item, trait_assoc_item)) = trait_assoc_items
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.iter()
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.find(|i| i.def_id == *item_def_id)
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.and_then(|trait_assoc_item| {
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items
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.iter()
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.find(|i| i.ident == trait_assoc_item.ident)
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.map(|impl_item| (impl_item, trait_assoc_item))
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})
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{
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let bounds = trait_generics
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.map(|generics| {
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get_generic_bound_spans(
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&generics,
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trait_name,
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trait_assoc_item.ident,
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)
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})
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.unwrap_or_else(Vec::new);
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cause.span = impl_item.span;
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cause.code = traits::AssocTypeBound(Box::new(AssocTypeBoundData {
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impl_span: item_span,
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original: trait_assoc_item.ident.span,
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bounds,
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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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};
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let item = self.item;
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if let Elaborate::All = elaborate {
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// FIXME: Make `extend_cause_with_original_assoc_item_obligation` take an iterator
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// instead of a slice.
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let trait_assoc_items: Vec<_> =
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tcx.associated_items(trait_ref.def_id).in_definition_order().copied().collect();
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let predicates = obligations.iter().map(|obligation| obligation.predicate).collect();
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let implied_obligations = traits::elaborate_predicates(tcx, predicates);
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let implied_obligations = implied_obligations.map(|pred| {
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let mut cause = cause.clone();
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extend_cause_with_original_assoc_item_obligation(
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tcx,
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trait_ref,
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item,
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&mut cause,
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&pred,
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&*trait_assoc_items,
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tcx.associated_items(trait_ref.def_id).in_definition_order().copied(),
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);
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traits::Obligation::new(cause, param_env, pred)
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});
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