Remove built-in Unsize impls

They exist in Chalk now.

4 files changed, 6 insertions, 235 deletions

diff --git a/crates/ra_hir_ty/src/traits.rs b/crates/ra_hir_ty/src/traits.rs
index 786f758e9..f7edb4c8b 100644
--- a/crates/ra_hir_ty/src/traits.rs
+++ b/crates/ra_hir_ty/src/traits.rs
@@ -295,13 +295,8 @@ pub enum Impl {
     /// A normal impl from an impl block.
     ImplDef(ImplId),
     /// Closure types implement the Fn traits synthetically.
+    // FIXME: implement closure support from Chalk, remove this
     ClosureFnTraitImpl(ClosureFnTraitImplData),
-    /// [T; n]: Unsize<[T]>
-    UnsizeArray,
-    /// T: Unsize<dyn Trait> where T: Trait
-    UnsizeToTraitObject(TraitId),
-    /// dyn Trait: Unsize<dyn SuperTrait> if Trait: SuperTrait
-    UnsizeToSuperTraitObject(UnsizeToSuperTraitObjectData),
 }
 /// This exists just for Chalk, because our ImplIds are only unique per module.
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
diff --git a/crates/ra_hir_ty/src/traits/builtin.rs b/crates/ra_hir_ty/src/traits/builtin.rs
index 6d5f2d46a..86e22e459 100644
--- a/crates/ra_hir_ty/src/traits/builtin.rs
+++ b/crates/ra_hir_ty/src/traits/builtin.rs
@@ -1,15 +1,12 @@
 //! This module provides the built-in trait implementations, e.g. to make
 //! closures implement `Fn`.
-use hir_def::{expr::Expr, lang_item::LangItemTarget, TraitId, TypeAliasId};
+use hir_def::{expr::Expr, TraitId, TypeAliasId};
 use hir_expand::name::name;
 use ra_db::CrateId;
 
-use super::{AssocTyValue, Impl, UnsizeToSuperTraitObjectData};
+use super::{AssocTyValue, Impl};
 use crate::{
-    db::HirDatabase,
-    utils::{all_super_traits, generics},
-    ApplicationTy, Binders, BoundVar, DebruijnIndex, GenericPredicate, Substs, TraitRef, Ty,
-    TypeCtor, TypeWalk,
+    db::HirDatabase, ApplicationTy, BoundVar, DebruijnIndex, Substs, TraitRef, Ty, TypeCtor,
 };
 
 pub(super) struct BuiltinImplData {
@@ -31,7 +28,7 @@ pub(super) fn get_builtin_impls(
     krate: CrateId,
     ty: &Ty,
     // The first argument for the trait, if present
-    arg: &Option<Ty>,
+    _arg: &Option<Ty>,
     trait_: TraitId,
     mut callback: impl FnMut(Impl),
 ) {
@@ -50,60 +47,12 @@ pub(super) fn get_builtin_impls(
             }
         }
     }
-
-    let unsize_trait = get_unsize_trait(db, krate);
-    if let Some(actual_trait) = unsize_trait {
-        if trait_ == actual_trait {
-            get_builtin_unsize_impls(db, krate, ty, arg, callback);
-        }
-    }
-}
-
-fn get_builtin_unsize_impls(
-    db: &dyn HirDatabase,
-    krate: CrateId,
-    ty: &Ty,
-    // The first argument for the trait, if present
-    arg: &Option<Ty>,
-    mut callback: impl FnMut(Impl),
-) {
-    if !check_unsize_impl_prerequisites(db, krate) {
-        return;
-    }
-
-    if let Ty::Apply(ApplicationTy { ctor: TypeCtor::Array, .. }) = ty {
-        callback(Impl::UnsizeArray);
-        return; // array is unsized, the rest of the impls shouldn't apply
-    }
-
-    if let Some(target_trait) = arg.as_ref().and_then(|t| t.dyn_trait_ref()) {
-        // FIXME what about more complicated dyn tys with marker traits?
-        if let Some(trait_ref) = ty.dyn_trait_ref() {
-            if trait_ref.trait_ != target_trait.trait_ {
-                let super_traits = all_super_traits(db.upcast(), trait_ref.trait_);
-                if super_traits.contains(&target_trait.trait_) {
-                    callback(Impl::UnsizeToSuperTraitObject(UnsizeToSuperTraitObjectData {
-                        trait_: trait_ref.trait_,
-                        super_trait: target_trait.trait_,
-                    }));
-                }
-            }
-        } else {
-            // FIXME only for sized types
-            callback(Impl::UnsizeToTraitObject(target_trait.trait_));
-        }
-    }
 }
 
 pub(super) fn impl_datum(db: &dyn HirDatabase, krate: CrateId, impl_: Impl) -> BuiltinImplData {
     match impl_ {
         Impl::ImplDef(_) => unreachable!(),
         Impl::ClosureFnTraitImpl(data) => closure_fn_trait_impl_datum(db, krate, data),
-        Impl::UnsizeArray => array_unsize_impl_datum(db, krate),
-        Impl::UnsizeToTraitObject(trait_) => trait_object_unsize_impl_datum(db, krate, trait_),
-        Impl::UnsizeToSuperTraitObject(data) => {
-            super_trait_object_unsize_impl_datum(db, krate, data)
-        }
     }
 }
 
@@ -227,145 +176,3 @@ fn closure_fn_trait_output_assoc_ty_value(
         value: output_ty,
     }
 }
-
-// Array unsizing
-
-fn check_unsize_impl_prerequisites(db: &dyn HirDatabase, krate: CrateId) -> bool {
-    // the Unsize trait needs to exist and have two type parameters (Self and T)
-    let unsize_trait = match get_unsize_trait(db, krate) {
-        Some(t) => t,
-        None => return false,
-    };
-    let generic_params = generics(db.upcast(), unsize_trait.into());
-    generic_params.len() == 2
-}
-
-fn array_unsize_impl_datum(db: &dyn HirDatabase, krate: CrateId) -> BuiltinImplData {
-    // impl<T> Unsize<[T]> for [T; _]
-    // (this can be a single impl because we don't distinguish array sizes currently)
-
-    let trait_ = get_unsize_trait(db, krate) // get unsize trait
-        // the existence of the Unsize trait has been checked before
-        .expect("Unsize trait missing");
-
-    let var = Ty::Bound(BoundVar::new(DebruijnIndex::INNERMOST, 0));
-    let substs = Substs::builder(2)
-        .push(Ty::apply_one(TypeCtor::Array, var.clone()))
-        .push(Ty::apply_one(TypeCtor::Slice, var))
-        .build();
-
-    let trait_ref = TraitRef { trait_, substs };
-
-    BuiltinImplData {
-        num_vars: 1,
-        trait_ref,
-        where_clauses: Vec::new(),
-        assoc_ty_values: Vec::new(),
-    }
-}
-
-// Trait object unsizing
-
-fn trait_object_unsize_impl_datum(
-    db: &dyn HirDatabase,
-    krate: CrateId,
-    trait_: TraitId,
-) -> BuiltinImplData {
-    // impl<T, T1, ...> Unsize<dyn Trait<T1, ...>> for T where T: Trait<T1, ...>
-
-    let unsize_trait = get_unsize_trait(db, krate) // get unsize trait
-        // the existence of the Unsize trait has been checked before
-        .expect("Unsize trait missing");
-
-    let self_ty = Ty::Bound(BoundVar::new(DebruijnIndex::INNERMOST, 0));
-
-    let target_substs = Substs::build_for_def(db, trait_)
-        .push(Ty::Bound(BoundVar::new(DebruijnIndex::INNERMOST, 0)))
-        .fill_with_bound_vars(DebruijnIndex::ONE, 1)
-        .build();
-    let num_vars = target_substs.len();
-    let target_trait_ref = TraitRef { trait_, substs: target_substs };
-    let target_bounds = vec![GenericPredicate::Implemented(target_trait_ref)];
-
-    let self_substs =
-        Substs::build_for_def(db, trait_).fill_with_bound_vars(DebruijnIndex::INNERMOST, 0).build();
-    let self_trait_ref = TraitRef { trait_, substs: self_substs };
-    let where_clauses = vec![GenericPredicate::Implemented(self_trait_ref)];
-
-    let impl_substs = Substs::builder(2).push(self_ty).push(Ty::Dyn(target_bounds.into())).build();
-
-    let trait_ref = TraitRef { trait_: unsize_trait, substs: impl_substs };
-
-    BuiltinImplData { num_vars, trait_ref, where_clauses, assoc_ty_values: Vec::new() }
-}
-
-fn super_trait_object_unsize_impl_datum(
-    db: &dyn HirDatabase,
-    krate: CrateId,
-    data: UnsizeToSuperTraitObjectData,
-) -> BuiltinImplData {
-    // impl<T1, ...> Unsize<dyn SuperTrait> for dyn Trait<T1, ...>
-
-    let unsize_trait = get_unsize_trait(db, krate) // get unsize trait
-        // the existence of the Unsize trait has been checked before
-        .expect("Unsize trait missing");
-
-    let self_substs = Substs::build_for_def(db, data.trait_)
-        .fill_with_bound_vars(DebruijnIndex::INNERMOST, 0)
-        .build();
-    let self_trait_ref = TraitRef { trait_: data.trait_, substs: self_substs.clone() };
-
-    let num_vars = self_substs.len() - 1;
-
-    // we need to go from our trait to the super trait, substituting type parameters
-    let path = crate::utils::find_super_trait_path(db.upcast(), data.trait_, data.super_trait);
-
-    let mut current_trait_ref = self_trait_ref.clone();
-    for t in path.into_iter().skip(1) {
-        let bounds = db.generic_predicates(current_trait_ref.trait_.into());
-        let super_trait_ref = bounds
-            .iter()
-            .find_map(|b| match &b.value {
-                GenericPredicate::Implemented(tr)
-                    if tr.trait_ == t
-                        && tr.substs[0]
-                            == Ty::Bound(BoundVar::new(DebruijnIndex::INNERMOST, 0)) =>
-                {
-                    Some(Binders { value: tr, num_binders: b.num_binders })
-                }
-                _ => None,
-            })
-            .expect("trait bound for known super trait not found");
-        current_trait_ref = super_trait_ref.cloned().subst(&current_trait_ref.substs);
-    }
-
-    // We need to renumber the variables a bit now: from ^0.0, ^0.1, ^0.2, ...
-    // to ^0.0, ^1.0, ^1.1. The reason for this is that the first variable comes
-    // from the dyn Trait binder, while the other variables come from the impl.
-    let new_substs = Substs::builder(num_vars + 1)
-        .push(Ty::Bound(BoundVar::new(DebruijnIndex::INNERMOST, 0)))
-        .fill_with_bound_vars(DebruijnIndex::ONE, 0)
-        .build();
-
-    let self_bounds =
-        vec![GenericPredicate::Implemented(self_trait_ref.subst_bound_vars(&new_substs))];
-    let super_bounds =
-        vec![GenericPredicate::Implemented(current_trait_ref.subst_bound_vars(&new_substs))];
-
-    let substs = Substs::builder(2)
-        .push(Ty::Dyn(self_bounds.into()))
-        .push(Ty::Dyn(super_bounds.into()))
-        .build();
-
-    let trait_ref = TraitRef { trait_: unsize_trait, substs };
-
-    BuiltinImplData { num_vars, trait_ref, where_clauses: Vec::new(), assoc_ty_values: Vec::new() }
-}
-
-fn get_unsize_trait(db: &dyn HirDatabase, krate: CrateId) -> Option<TraitId> {
-    let target = db.lang_item(krate, "unsize".into())?;
-    match target {
-        LangItemTarget::TraitId(t) => Some(t),
-        _ => None,
-    }
-}
diff --git a/crates/ra_hir_ty/src/traits/chalk/mapping.rs b/crates/ra_hir_ty/src/traits/chalk/mapping.rs
index 848cb6e7d..7bdb6264e 100644
--- a/crates/ra_hir_ty/src/traits/chalk/mapping.rs
+++ b/crates/ra_hir_ty/src/traits/chalk/mapping.rs
@@ -271,6 +271,7 @@ impl ToChalk for TypeCtor {
             }
             TypeCtor::Never => TypeName::Never,
 
+            // FIXME convert these
             TypeCtor::Adt(_)
             | TypeCtor::Array
             | TypeCtor::FnPtr { .. }
diff --git a/crates/ra_hir_ty/src/utils.rs b/crates/ra_hir_ty/src/utils.rs
index c45820ff0..e3e244268 100644
--- a/crates/ra_hir_ty/src/utils.rs
+++ b/crates/ra_hir_ty/src/utils.rs
@@ -110,38 +110,6 @@ pub(super) fn all_super_trait_refs(db: &dyn HirDatabase, trait_ref: TraitRef) ->
     result
 }
 
-/// Finds a path from a trait to one of its super traits. Returns an empty
-/// vector if there is no path.
-pub(super) fn find_super_trait_path(
-    db: &dyn DefDatabase,
-    trait_: TraitId,
-    super_trait: TraitId,
-) -> Vec<TraitId> {
-    let mut result = Vec::with_capacity(2);
-    result.push(trait_);
-    return if go(db, super_trait, &mut result) { result } else { Vec::new() };
-
-    fn go(db: &dyn DefDatabase, super_trait: TraitId, path: &mut Vec<TraitId>) -> bool {
-        let trait_ = *path.last().unwrap();
-        if trait_ == super_trait {
-            return true;
-        }
-
-        for tt in direct_super_traits(db, trait_) {
-            if path.contains(&tt) {
-                continue;
-            }
-            path.push(tt);
-            if go(db, super_trait, path) {
-                return true;
-            } else {
-                path.pop();
-            }
-        }
-        false
-    }
-}
-
 pub(super) fn associated_type_by_name_including_super_traits(
     db: &dyn HirDatabase,
     trait_ref: TraitRef,