1 files changed, 272 insertions, 0 deletions
diff --git a/compiler/rustc_middle/src/ty/trait_def.rs b/compiler/rustc_middle/src/ty/trait_def.rs
new file mode 100644
index 000000000..541dace5c
--- /dev/null
+++ b/compiler/rustc_middle/src/ty/trait_def.rs
@@ -0,0 +1,272 @@
+use crate::traits::specialization_graph;
+use crate::ty::fast_reject::{self, SimplifiedType, TreatParams};
+use crate::ty::visit::TypeVisitable;
+use crate::ty::{Ident, Ty, TyCtxt};
+use hir::def_id::LOCAL_CRATE;
+use rustc_hir as hir;
+use rustc_hir::def_id::DefId;
+use std::iter;
+
+use rustc_data_structures::fx::FxIndexMap;
+use rustc_errors::ErrorGuaranteed;
+use rustc_macros::HashStable;
+
+/// A trait's definition with type information.
+#[derive(HashStable, Encodable, Decodable)]
+pub struct TraitDef {
+    pub def_id: DefId,
+
+    pub unsafety: hir::Unsafety,
+
+    /// If `true`, then this trait had the `#[rustc_paren_sugar]`
+    /// attribute, indicating that it should be used with `Foo()`
+    /// sugar. This is a temporary thing -- eventually any trait will
+    /// be usable with the sugar (or without it).
+    pub paren_sugar: bool,
+
+    pub has_auto_impl: bool,
+
+    /// If `true`, then this trait has the `#[marker]` attribute, indicating
+    /// that all its associated items have defaults that cannot be overridden,
+    /// and thus `impl`s of it are allowed to overlap.
+    pub is_marker: bool,
+
+    /// If `true`, then this trait has the `#[rustc_skip_array_during_method_dispatch]`
+    /// attribute, indicating that editions before 2021 should not consider this trait
+    /// during method dispatch if the receiver is an array.
+    pub skip_array_during_method_dispatch: bool,
+
+    /// Used to determine whether the standard library is allowed to specialize
+    /// on this trait.
+    pub specialization_kind: TraitSpecializationKind,
+
+    /// List of functions from `#[rustc_must_implement_one_of]` attribute one of which
+    /// must be implemented.
+    pub must_implement_one_of: Option<Box<[Ident]>>,
+}
+
+/// Whether this trait is treated specially by the standard library
+/// specialization lint.
+#[derive(HashStable, PartialEq, Clone, Copy, Encodable, Decodable)]
+pub enum TraitSpecializationKind {
+    /// The default. Specializing on this trait is not allowed.
+    None,
+    /// Specializing on this trait is allowed because it doesn't have any
+    /// methods. For example `Sized` or `FusedIterator`.
+    /// Applies to traits with the `rustc_unsafe_specialization_marker`
+    /// attribute.
+    Marker,
+    /// Specializing on this trait is allowed because all of the impls of this
+    /// trait are "always applicable". Always applicable means that if
+    /// `X<'x>: T<'y>` for any lifetimes, then `for<'a, 'b> X<'a>: T<'b>`.
+    /// Applies to traits with the `rustc_specialization_trait` attribute.
+    AlwaysApplicable,
+}
+
+#[derive(Default, Debug, HashStable)]
+pub struct TraitImpls {
+    blanket_impls: Vec<DefId>,
+    /// Impls indexed by their simplified self type, for fast lookup.
+    non_blanket_impls: FxIndexMap<SimplifiedType, Vec<DefId>>,
+}
+
+impl TraitImpls {
+    pub fn blanket_impls(&self) -> &[DefId] {
+        self.blanket_impls.as_slice()
+    }
+
+    pub fn non_blanket_impls(&self) -> &FxIndexMap<SimplifiedType, Vec<DefId>> {
+        &self.non_blanket_impls
+    }
+}
+
+impl<'tcx> TraitDef {
+    pub fn new(
+        def_id: DefId,
+        unsafety: hir::Unsafety,
+        paren_sugar: bool,
+        has_auto_impl: bool,
+        is_marker: bool,
+        skip_array_during_method_dispatch: bool,
+        specialization_kind: TraitSpecializationKind,
+        must_implement_one_of: Option<Box<[Ident]>>,
+    ) -> TraitDef {
+        TraitDef {
+            def_id,
+            unsafety,
+            paren_sugar,
+            has_auto_impl,
+            is_marker,
+            skip_array_during_method_dispatch,
+            specialization_kind,
+            must_implement_one_of,
+        }
+    }
+
+    pub fn ancestors(
+        &self,
+        tcx: TyCtxt<'tcx>,
+        of_impl: DefId,
+    ) -> Result<specialization_graph::Ancestors<'tcx>, ErrorGuaranteed> {
+        specialization_graph::ancestors(tcx, self.def_id, of_impl)
+    }
+}
+
+impl<'tcx> TyCtxt<'tcx> {
+    pub fn for_each_impl<F: FnMut(DefId)>(self, def_id: DefId, mut f: F) {
+        let impls = self.trait_impls_of(def_id);
+
+        for &impl_def_id in impls.blanket_impls.iter() {
+            f(impl_def_id);
+        }
+
+        for v in impls.non_blanket_impls.values() {
+            for &impl_def_id in v {
+                f(impl_def_id);
+            }
+        }
+    }
+
+    /// Iterate over every impl that could possibly match the
+    /// self type `self_ty`.
+    pub fn for_each_relevant_impl<F: FnMut(DefId)>(
+        self,
+        def_id: DefId,
+        self_ty: Ty<'tcx>,
+        mut f: F,
+    ) {
+        let _: Option<()> = self.find_map_relevant_impl(def_id, self_ty, |did| {
+            f(did);
+            None
+        });
+    }
+
+    pub fn non_blanket_impls_for_ty(
+        self,
+        def_id: DefId,
+        self_ty: Ty<'tcx>,
+    ) -> impl Iterator<Item = DefId> + 'tcx {
+        let impls = self.trait_impls_of(def_id);
+        if let Some(simp) = fast_reject::simplify_type(self, self_ty, TreatParams::AsInfer) {
+            if let Some(impls) = impls.non_blanket_impls.get(&simp) {
+                return impls.iter().copied();
+            }
+        }
+
+        [].iter().copied()
+    }
+
+    /// Applies function to every impl that could possibly match the self type `self_ty` and returns
+    /// the first non-none value.
+    pub fn find_map_relevant_impl<T, F: FnMut(DefId) -> Option<T>>(
+        self,
+        def_id: DefId,
+        self_ty: Ty<'tcx>,
+        mut f: F,
+    ) -> Option<T> {
+        // FIXME: This depends on the set of all impls for the trait. That is
+        // unfortunate wrt. incremental compilation.
+        //
+        // If we want to be faster, we could have separate queries for
+        // blanket and non-blanket impls, and compare them separately.
+        let impls = self.trait_impls_of(def_id);
+
+        for &impl_def_id in impls.blanket_impls.iter() {
+            if let result @ Some(_) = f(impl_def_id) {
+                return result;
+            }
+        }
+
+        // Note that we're using `TreatParams::AsPlaceholder` to query `non_blanket_impls` while using
+        // `TreatParams::AsInfer` while actually adding them.
+        //
+        // This way, when searching for some impl for `T: Trait`, we do not look at any impls
+        // whose outer level is not a parameter or projection. Especially for things like
+        // `T: Clone` this is incredibly useful as we would otherwise look at all the impls
+        // of `Clone` for `Option<T>`, `Vec<T>`, `ConcreteType` and so on.
+        if let Some(simp) = fast_reject::simplify_type(self, self_ty, TreatParams::AsPlaceholder) {
+            if let Some(impls) = impls.non_blanket_impls.get(&simp) {
+                for &impl_def_id in impls {
+                    if let result @ Some(_) = f(impl_def_id) {
+                        return result;
+                    }
+                }
+            }
+        } else {
+            for &impl_def_id in impls.non_blanket_impls.values().flatten() {
+                if let result @ Some(_) = f(impl_def_id) {
+                    return result;
+                }
+            }
+        }
+
+        None
+    }
+
+    /// Returns an iterator containing all impls
+    pub fn all_impls(self, def_id: DefId) -> impl Iterator<Item = DefId> + 'tcx {
+        let TraitImpls { blanket_impls, non_blanket_impls } = self.trait_impls_of(def_id);
+
+        blanket_impls.iter().chain(non_blanket_impls.iter().flat_map(|(_, v)| v)).cloned()
+    }
+}
+
+// Query provider for `trait_impls_of`.
+pub(super) fn trait_impls_of_provider(tcx: TyCtxt<'_>, trait_id: DefId) -> TraitImpls {
+    let mut impls = TraitImpls::default();
+
+    // Traits defined in the current crate can't have impls in upstream
+    // crates, so we don't bother querying the cstore.
+    if !trait_id.is_local() {
+        for &cnum in tcx.crates(()).iter() {
+            for &(impl_def_id, simplified_self_ty) in
+                tcx.implementations_of_trait((cnum, trait_id)).iter()
+            {
+                if let Some(simplified_self_ty) = simplified_self_ty {
+                    impls
+                        .non_blanket_impls
+                        .entry(simplified_self_ty)
+                        .or_default()
+                        .push(impl_def_id);
+                } else {
+                    impls.blanket_impls.push(impl_def_id);
+                }
+            }
+        }
+    }
+
+    for &impl_def_id in tcx.hir().trait_impls(trait_id) {
+        let impl_def_id = impl_def_id.to_def_id();
+
+        let impl_self_ty = tcx.type_of(impl_def_id);
+        if impl_self_ty.references_error() {
+            continue;
+        }
+
+        if let Some(simplified_self_ty) =
+            fast_reject::simplify_type(tcx, impl_self_ty, TreatParams::AsInfer)
+        {
+            impls.non_blanket_impls.entry(simplified_self_ty).or_default().push(impl_def_id);
+        } else {
+            impls.blanket_impls.push(impl_def_id);
+        }
+    }
+
+    impls
+}
+
+// Query provider for `incoherent_impls`.
+#[instrument(level = "debug", skip(tcx))]
+pub(super) fn incoherent_impls_provider(tcx: TyCtxt<'_>, simp: SimplifiedType) -> &[DefId] {
+    let mut impls = Vec::new();
+
+    for cnum in iter::once(LOCAL_CRATE).chain(tcx.crates(()).iter().copied()) {
+        for &impl_def_id in tcx.crate_incoherent_impls((cnum, simp)) {
+            impls.push(impl_def_id)
+        }
+    }
+
+    debug!(?impls);
+
+    tcx.arena.alloc_slice(&impls)
+}