Merge #8539

8539:  fix: Do not propose inherent traits in flyimports and import assists r=flodiebold a=SomeoneToIgnore

Closes https://github.com/rust-analyzer/rust-analyzer/issues/8520

I've went with a separate method approach, since the [highlighted code](https://github.com/rust-analyzer/rust-analyzer/issues/8520#issuecomment-819856337) has not`Type` and uses `Ty` to get his data, but the code I had to change has no access to `Ty` and has `Type` only.

Co-authored-by: Kirill Bulatov <mail4score@gmail.com>

crates/hir/src/lib.rs

@@ -2066,6 +2066,18 @@ impl Type {
         self.ty.dyn_trait().map(Into::into)
     }
 
+    /// If a type can be represented as `dyn Trait`, returns all traits accessible via this type,
+    /// or an empty iterator otherwise.
+    pub fn applicable_inherent_traits<'a>(
+        &'a self,
+        db: &'a dyn HirDatabase,
+    ) -> impl Iterator<Item = Trait> + 'a {
+        self.autoderef(db)
+            .filter_map(|derefed_type| derefed_type.ty.dyn_trait())
+            .flat_map(move |dyn_trait_id| hir_ty::all_super_traits(db.upcast(), dyn_trait_id))
+            .map(Trait::from)
+    }
+
     pub fn as_impl_traits(&self, db: &dyn HirDatabase) -> Option<Vec<Trait>> {
         self.ty.impl_trait_bounds(db).map(|it| {
             it.into_iter()

crates/hir_ty/src/lib.rs

@@ -56,6 +56,7 @@ pub use mapping::{
     to_foreign_def_id, to_placeholder_idx,
 };
 pub use traits::TraitEnvironment;
+pub use utils::all_super_traits;
 pub use walk::TypeWalk;
 
 pub use chalk_ir::{

crates/hir_ty/src/utils.rs

@@ -78,7 +78,7 @@ fn direct_super_trait_refs(db: &dyn HirDatabase, trait_ref: &TraitRef) -> Vec<Tr
 
 /// Returns an iterator over the whole super trait hierarchy (including the
 /// trait itself).
-pub(super) fn all_super_traits(db: &dyn DefDatabase, trait_: TraitId) -> Vec<TraitId> {
+pub fn all_super_traits(db: &dyn DefDatabase, trait_: TraitId) -> Vec<TraitId> {
     // we need to take care a bit here to avoid infinite loops in case of cycles
     // (i.e. if we have `trait A: B; trait B: A;`)
     let mut result = vec![trait_];

crates/ide_completion/src/completions/flyimport.rs

@@ -1127,4 +1127,27 @@ impl Bar for Foo {
             expect![[r#""#]],
         );
     }
+
+    #[test]
+    fn no_inherent_candidates_proposed() {
+        check(
+            r#"
+mod baz {
+    pub trait DefDatabase {
+        fn method1(&self);
+    }
+    pub trait HirDatabase: DefDatabase {
+        fn method2(&self);
+    }
+}
+
+mod bar {
+    fn test(db: &dyn crate::baz::HirDatabase) {
+        db.metho$0
+    }
+}
+            "#,
+            expect![[r#""#]],
+        );
+    }
 }

crates/ide_db/src/helpers/import_assets.rs

@@ -436,6 +436,8 @@ fn trait_applicable_items(
     })
     .collect();
 
+    let related_dyn_traits =
+        trait_candidate.receiver_ty.applicable_inherent_traits(db).collect::<FxHashSet<_>>();
     let mut located_imports = FxHashSet::default();
 
     if trait_assoc_item {
@@ -451,12 +453,16 @@ fn trait_applicable_items(
                             return None;
                         }
                     }
+                    let located_trait = assoc.containing_trait(db)?;
+                    if related_dyn_traits.contains(&located_trait) {
+                        return None;
+                    }
 
-                    let item = ItemInNs::from(ModuleDef::from(assoc.containing_trait(db)?));
+                    let trait_item = ItemInNs::from(ModuleDef::from(located_trait));
                     let original_item = assoc_to_item(assoc);
                     located_imports.insert(LocatedImport::new(
-                        mod_path(item)?,
-                        item,
+                        mod_path(trait_item)?,
+                        trait_item,
                         original_item,
                         mod_path(original_item),
                     ));
@@ -473,11 +479,15 @@ fn trait_applicable_items(
             |_, function| {
                 let assoc = function.as_assoc_item(db)?;
                 if required_assoc_items.contains(&assoc) {
-                    let item = ItemInNs::from(ModuleDef::from(assoc.containing_trait(db)?));
+                    let located_trait = assoc.containing_trait(db)?;
+                    if related_dyn_traits.contains(&located_trait) {
+                        return None;
+                    }
+                    let trait_item = ItemInNs::from(ModuleDef::from(located_trait));
                     let original_item = assoc_to_item(assoc);
                     located_imports.insert(LocatedImport::new(
-                        mod_path(item)?,
-                        item,
+                        mod_path(trait_item)?,
+                        trait_item,
                         original_item,
                         mod_path(original_item),
                     ));