Merge #8020

8020: Power up goto_implementation r=matklad a=Veykril

by allowing it to be invoked on references of names, now showing all (trait)
implementations of the given type in all crates instead of just the defining
crate as well as including support for builtin types

![image](https://user-images.githubusercontent.com/3757771/111144403-52bb0700-8587-11eb-9205-7a2a5b8b75a3.png)
Example screenshot of `impl`s of Box in `log`, `alloc`, `std` and the current crate. Before you had to invoke it on the definition where it would only show the `impls` in `alloc`.

Co-authored-by: Lukas Wirth <lukastw97@gmail.com>

crates/hir/src/lib.rs

@@ -51,7 +51,8 @@ use hir_expand::{diagnostics::DiagnosticSink, name::name, MacroDefKind};
 use hir_ty::{
     autoderef,
     display::{write_bounds_like_dyn_trait_with_prefix, HirDisplayError, HirFormatter},
-    method_resolution, to_assoc_type_id,
+    method_resolution::{self, TyFingerprint},
+    to_assoc_type_id,
     traits::{FnTrait, Solution, SolutionVariables},
     AliasTy, BoundVar, CallableDefId, CallableSig, Canonical, DebruijnIndex, GenericPredicate,
     InEnvironment, Interner, Obligation, ProjectionPredicate, ProjectionTy, Scalar, Substs, Ty,
@@ -695,8 +696,8 @@ impl Adt {
         }
     }
 
-    pub fn krate(self, db: &dyn HirDatabase) -> Option<Crate> {
-        Some(self.module(db).krate())
+    pub fn krate(self, db: &dyn HirDatabase) -> Crate {
+        self.module(db).krate()
     }
 
     pub fn name(self, db: &dyn HirDatabase) -> Name {
@@ -1018,8 +1019,8 @@ impl TypeAlias {
         Module { id: self.id.lookup(db.upcast()).module(db.upcast()) }
     }
 
-    pub fn krate(self, db: &dyn HirDatabase) -> Option<Crate> {
-        Some(self.module(db).krate())
+    pub fn krate(self, db: &dyn HirDatabase) -> Crate {
+        self.module(db).krate()
     }
 
     pub fn type_ref(self, db: &dyn HirDatabase) -> Option<TypeRef> {
@@ -1482,9 +1483,44 @@ impl Impl {
 
         inherent.all_impls().chain(trait_.all_impls()).map(Self::from).collect()
     }
-    pub fn for_trait(db: &dyn HirDatabase, krate: Crate, trait_: Trait) -> Vec<Impl> {
-        let impls = db.trait_impls_in_crate(krate.id);
-        impls.for_trait(trait_.id).map(Self::from).collect()
+
+    pub fn all_for_type(db: &dyn HirDatabase, Type { krate, ty }: Type) -> Vec<Impl> {
+        let def_crates = match ty.value.def_crates(db, krate) {
+            Some(def_crates) => def_crates,
+            None => return Vec::new(),
+        };
+
+        let filter = |impl_def: &Impl| {
+            let target_ty = impl_def.target_ty(db);
+            let rref = target_ty.remove_ref();
+            ty.value.equals_ctor(rref.as_ref().map_or(&target_ty.ty.value, |it| &it.ty.value))
+        };
+
+        let mut all = Vec::new();
+        def_crates.into_iter().for_each(|id| {
+            all.extend(db.inherent_impls_in_crate(id).all_impls().map(Self::from).filter(filter))
+        });
+        let fp = TyFingerprint::for_impl(&ty.value);
+        for id in db.crate_graph().iter() {
+            match fp {
+                Some(fp) => all.extend(
+                    db.trait_impls_in_crate(id).for_self_ty(fp).map(Self::from).filter(filter),
+                ),
+                None => all
+                    .extend(db.trait_impls_in_crate(id).all_impls().map(Self::from).filter(filter)),
+            }
+        }
+        all
+    }
+
+    pub fn all_for_trait(db: &dyn HirDatabase, trait_: Trait) -> Vec<Impl> {
+        let krate = trait_.module(db).krate();
+        let mut all = Vec::new();
+        for Crate { id } in krate.reverse_dependencies(db).into_iter().chain(Some(krate)) {
+            let impls = db.trait_impls_in_crate(id);
+            all.extend(impls.for_trait(trait_.id).map(Self::from))
+        }
+        all
     }
 
     // FIXME: the return type is wrong. This should be a hir version of
@@ -1932,12 +1968,6 @@ impl Type {
         self.ty.value.associated_type_parent_trait(db).map(Into::into)
     }
 
-    // FIXME: provide required accessors such that it becomes implementable from outside.
-    pub fn is_equal_for_find_impls(&self, other: &Type) -> bool {
-        let rref = other.remove_ref();
-        self.ty.value.equals_ctor(rref.as_ref().map_or(&other.ty.value, |it| &it.ty.value))
-    }
-
     fn derived(&self, ty: Ty) -> Type {
         Type {
             krate: self.krate,