Move associated_item* providers to their own module

Author: matthewjasper

compiler/rustc_ty_utils/src/assoc.rs

@@ -0,0 +1,230 @@
+use rustc_errors::struct_span_err;
+use rustc_hir as hir;
+use rustc_hir::def_id::{DefId, LocalDefId};
+use rustc_middle::ty::{self, TyCtxt, TypeFoldable};
+
+pub fn provide(providers: &mut ty::query::Providers) {
+    *providers = ty::query::Providers {
+        associated_item,
+        associated_item_def_ids,
+        associated_items,
+        trait_of_item,
+        ..*providers
+    };
+}
+
+fn associated_item_def_ids(tcx: TyCtxt<'_>, def_id: DefId) -> &[DefId] {
+    let item = tcx.hir().expect_item(def_id.expect_local());
+    match item.kind {
+        hir::ItemKind::Trait(.., ref trait_item_refs) => tcx.arena.alloc_from_iter(
+            trait_item_refs.iter().map(|trait_item_ref| trait_item_ref.id.def_id.to_def_id()),
+        ),
+        hir::ItemKind::Impl(ref impl_) => tcx.arena.alloc_from_iter(
+            impl_.items.iter().map(|impl_item_ref| impl_item_ref.id.def_id.to_def_id()),
+        ),
+        hir::ItemKind::TraitAlias(..) => &[],
+        _ => span_bug!(item.span, "associated_item_def_ids: not impl or trait"),
+    }
+}
+
+fn associated_items(tcx: TyCtxt<'_>, def_id: DefId) -> ty::AssocItems<'_> {
+    let items = tcx.associated_item_def_ids(def_id).iter().map(|did| tcx.associated_item(*did));
+    ty::AssocItems::new(items)
+}
+
+/// If the given `DefId` describes an item belonging to a trait,
+/// returns the `DefId` of the trait that the trait item belongs to;
+/// otherwise, returns `None`.
+fn trait_of_item(tcx: TyCtxt<'_>, def_id: DefId) -> Option<DefId> {
+    tcx.opt_associated_item(def_id).and_then(|associated_item| match associated_item.container {
+        ty::TraitContainer(def_id) => Some(def_id),
+        ty::ImplContainer(_) => None,
+    })
+}
+
+fn associated_item(tcx: TyCtxt<'_>, def_id: DefId) -> ty::AssocItem {
+    let id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
+    let parent_id = tcx.hir().get_parent_item(id);
+    let parent_def_id = tcx.hir().local_def_id(parent_id);
+    let parent_item = tcx.hir().expect_item(parent_def_id);
+    match parent_item.kind {
+        hir::ItemKind::Impl(ref impl_) => {
+            if let Some(impl_item_ref) =
+                impl_.items.iter().find(|i| i.id.def_id.to_def_id() == def_id)
+            {
+                let assoc_item =
+                    associated_item_from_impl_item_ref(tcx, parent_def_id, impl_item_ref);
+                debug_assert_eq!(assoc_item.def_id, def_id);
+                return assoc_item;
+            }
+        }
+
+        hir::ItemKind::Trait(.., ref trait_item_refs) => {
+            if let Some(trait_item_ref) =
+                trait_item_refs.iter().find(|i| i.id.def_id.to_def_id() == def_id)
+            {
+                let assoc_item =
+                    associated_item_from_trait_item_ref(tcx, parent_def_id, trait_item_ref);
+                debug_assert_eq!(assoc_item.def_id, def_id);
+                return assoc_item;
+            }
+        }
+
+        _ => {}
+    }
+
+    span_bug!(
+        parent_item.span,
+        "unexpected parent of trait or impl item or item not found: {:?}",
+        parent_item.kind
+    )
+}
+
+fn associated_item_from_trait_item_ref(
+    tcx: TyCtxt<'_>,
+    parent_def_id: LocalDefId,
+    trait_item_ref: &hir::TraitItemRef,
+) -> ty::AssocItem {
+    let def_id = trait_item_ref.id.def_id;
+    let (kind, has_self) = match trait_item_ref.kind {
+        hir::AssocItemKind::Const => (ty::AssocKind::Const, false),
+        hir::AssocItemKind::Fn { has_self } => (ty::AssocKind::Fn, has_self),
+        hir::AssocItemKind::Type => (ty::AssocKind::Type, false),
+    };
+
+    ty::AssocItem {
+        ident: trait_item_ref.ident,
+        kind,
+        vis: tcx.visibility(def_id),
+        defaultness: trait_item_ref.defaultness,
+        def_id: def_id.to_def_id(),
+        trait_item_def_id: Some(def_id.to_def_id()),
+        container: ty::TraitContainer(parent_def_id.to_def_id()),
+        fn_has_self_parameter: has_self,
+    }
+}
+
+fn associated_item_from_impl_item_ref(
+    tcx: TyCtxt<'_>,
+    parent_def_id: LocalDefId,
+    impl_item_ref: &hir::ImplItemRef,
+) -> ty::AssocItem {
+    let def_id = impl_item_ref.id.def_id;
+    let (kind, has_self) = match impl_item_ref.kind {
+        hir::AssocItemKind::Const => (ty::AssocKind::Const, false),
+        hir::AssocItemKind::Fn { has_self } => (ty::AssocKind::Fn, has_self),
+        hir::AssocItemKind::Type => (ty::AssocKind::Type, false),
+    };
+
+    let trait_item_def_id = impl_item_base_id(tcx, parent_def_id, impl_item_ref);
+
+    ty::AssocItem {
+        ident: impl_item_ref.ident,
+        kind,
+        vis: tcx.visibility(def_id),
+        defaultness: impl_item_ref.defaultness,
+        def_id: def_id.to_def_id(),
+        trait_item_def_id,
+        container: ty::ImplContainer(parent_def_id.to_def_id()),
+        fn_has_self_parameter: has_self,
+    }
+}
+
+fn impl_item_base_id<'tcx>(
+    tcx: TyCtxt<'tcx>,
+    parent_def_id: LocalDefId,
+    impl_item: &hir::ImplItemRef,
+) -> Option<DefId> {
+    let impl_trait_ref = tcx.impl_trait_ref(parent_def_id)?;
+
+    // If the trait reference itself is erroneous (so the compilation is going
+    // to fail), skip checking the items here -- the `impl_item` table in `tcx`
+    // isn't populated for such impls.
+    if impl_trait_ref.references_error() {
+        return None;
+    }
+
+    // Locate trait items
+    let associated_items = tcx.associated_items(impl_trait_ref.def_id);
+
+    // Match item against trait
+    let mut items = associated_items.filter_by_name(tcx, impl_item.ident, impl_trait_ref.def_id);
+
+    let mut trait_item = items.next()?;
+
+    let is_compatible = |ty: &&ty::AssocItem| match (ty.kind, &impl_item.kind) {
+        (ty::AssocKind::Const, hir::AssocItemKind::Const) => true,
+        (ty::AssocKind::Fn, hir::AssocItemKind::Fn { .. }) => true,
+        (ty::AssocKind::Type, hir::AssocItemKind::Type) => true,
+        _ => false,
+    };
+
+    // If we don't have a compatible item, we'll use the first one whose name matches
+    // to report an error.
+    let mut compatible_kind = is_compatible(&trait_item);
+
+    if !compatible_kind {
+        if let Some(ty_trait_item) = items.find(is_compatible) {
+            compatible_kind = true;
+            trait_item = ty_trait_item;
+        }
+    }
+
+    if compatible_kind {
+        Some(trait_item.def_id)
+    } else {
+        report_mismatch_error(tcx, trait_item.def_id, impl_trait_ref, impl_item);
+        None
+    }
+}
+
+#[inline(never)]
+#[cold]
+fn report_mismatch_error<'tcx>(
+    tcx: TyCtxt<'tcx>,
+    trait_item_def_id: DefId,
+    impl_trait_ref: ty::TraitRef<'tcx>,
+    impl_item: &hir::ImplItemRef,
+) {
+    let mut err = match impl_item.kind {
+        hir::AssocItemKind::Const => {
+            // Find associated const definition.
+            struct_span_err!(
+                tcx.sess,
+                impl_item.span,
+                E0323,
+                "item `{}` is an associated const, which doesn't match its trait `{}`",
+                impl_item.ident,
+                impl_trait_ref.print_only_trait_path()
+            )
+        }
+
+        hir::AssocItemKind::Fn { .. } => {
+            struct_span_err!(
+                tcx.sess,
+                impl_item.span,
+                E0324,
+                "item `{}` is an associated method, which doesn't match its trait `{}`",
+                impl_item.ident,
+                impl_trait_ref.print_only_trait_path()
+            )
+        }
+
+        hir::AssocItemKind::Type => {
+            struct_span_err!(
+                tcx.sess,
+                impl_item.span,
+                E0325,
+                "item `{}` is an associated type, which doesn't match its trait `{}`",
+                impl_item.ident,
+                impl_trait_ref.print_only_trait_path()
+            )
+        }
+    };
+
+    err.span_label(impl_item.span, "does not match trait");
+    if let Some(trait_span) = tcx.hir().span_if_local(trait_item_def_id) {
+        err.span_label(trait_span, "item in trait");
+    }
+    err.emit();
+}

compiler/rustc_ty_utils/src/lib.rs

@@ -16,13 +16,15 @@ extern crate tracing;
 
 use rustc_middle::ty::query::Providers;
 
+mod assoc;
 mod common_traits;
 pub mod instance;
 mod needs_drop;
 pub mod representability;
 mod ty;
 
 pub fn provide(providers: &mut Providers) {
+    assoc::provide(providers);
     common_traits::provide(providers);
     needs_drop::provide(providers);
     ty::provide(providers);