9 files changed, 102 insertions, 24 deletions

diff --git a/crates/hir/src/lib.rs b/crates/hir/src/lib.rs
index eba46a056..0acfa582a 100644
--- a/crates/hir/src/lib.rs
+++ b/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()
diff --git a/crates/hir_def/src/nameres/path_resolution.rs b/crates/hir_def/src/nameres/path_resolution.rs
index ccc9f22eb..c984148c3 100644
--- a/crates/hir_def/src/nameres/path_resolution.rs
+++ b/crates/hir_def/src/nameres/path_resolution.rs
@@ -387,7 +387,13 @@ impl DefMap {
             .get_legacy_macro(name)
             .map_or_else(PerNs::none, |m| PerNs::macros(m, Visibility::Public));
         let from_scope = self[module].scope.get(name);
-        let from_builtin = BUILTIN_SCOPE.get(name).copied().unwrap_or_else(PerNs::none);
+        let from_builtin = match self.block {
+            Some(_) => {
+                // Only resolve to builtins in the root `DefMap`.
+                PerNs::none()
+            }
+            None => BUILTIN_SCOPE.get(name).copied().unwrap_or_else(PerNs::none),
+        };
         let from_scope_or_builtin = match shadow {
             BuiltinShadowMode::Module => from_scope.or(from_builtin),
             BuiltinShadowMode::Other => {
diff --git a/crates/hir_ty/src/lib.rs b/crates/hir_ty/src/lib.rs
index 113234fa4..0505fa4ae 100644
--- a/crates/hir_ty/src/lib.rs
+++ b/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::{
diff --git a/crates/hir_ty/src/tests/simple.rs b/crates/hir_ty/src/tests/simple.rs
index 84c5c05fd..5948d0bc2 100644
--- a/crates/hir_ty/src/tests/simple.rs
+++ b/crates/hir_ty/src/tests/simple.rs
@@ -1765,6 +1765,24 @@ fn main() {
 }
 
 #[test]
+fn shadowing_primitive_with_inner_items() {
+    check_types(
+        r#"
+struct i32;
+struct Foo;
+
+impl i32 { fn foo(&self) -> Foo { Foo } }
+
+fn main() {
+    fn inner() {}
+    let x: i32 = i32;
+    x.foo();
+        //^ Foo
+}"#,
+    );
+}
+
+#[test]
 fn not_shadowing_primitive_by_module() {
     check_types(
         r#"
diff --git a/crates/hir_ty/src/utils.rs b/crates/hir_ty/src/utils.rs
index 5f6cb052a..2f04ee57a 100644
--- a/crates/hir_ty/src/utils.rs
+++ b/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_];
diff --git a/crates/ide_assists/src/handlers/fill_match_arms.rs b/crates/ide_assists/src/handlers/fill_match_arms.rs
index 878b3a3fa..80bd1b7e8 100644
--- a/crates/ide_assists/src/handlers/fill_match_arms.rs
+++ b/crates/ide_assists/src/handlers/fill_match_arms.rs
@@ -71,12 +71,6 @@ pub(crate) fn fill_match_arms(acc: &mut Assists, ctx: &AssistContext) -> Option<
             return None;
         }
 
-        // We do not currently support filling match arms for a tuple
-        // containing a single enum.
-        if enum_defs.len() < 2 {
-            return None;
-        }
-
         // When calculating the match arms for a tuple of enums, we want
         // to create a match arm for each possible combination of enum
         // values. The `multi_cartesian_product` method transforms
@@ -514,10 +508,7 @@ fn main() {
 
     #[test]
     fn fill_match_arms_single_element_tuple_of_enum() {
-        // For now we don't hande the case of a single element tuple, but
-        // we could handle this in the future if `make::tuple_pat` allowed
-        // creating a tuple with a single pattern.
-        check_assist_not_applicable(
+        check_assist(
             fill_match_arms,
             r#"
             enum A { One, Two }
@@ -528,6 +519,17 @@ fn main() {
                 }
             }
             "#,
+            r#"
+            enum A { One, Two }
+
+            fn main() {
+                let a = A::One;
+                match (a, ) {
+                    $0(A::One,) => {}
+                    (A::Two,) => {}
+                }
+            }
+            "#,
         );
     }
 
diff --git a/crates/ide_completion/src/completions/flyimport.rs b/crates/ide_completion/src/completions/flyimport.rs
index 5e61ecb4d..8e211ae1e 100644
--- a/crates/ide_completion/src/completions/flyimport.rs
+++ b/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#""#]],
+        );
+    }
 }
diff --git a/crates/ide_db/src/helpers/import_assets.rs b/crates/ide_db/src/helpers/import_assets.rs
index 8ce648367..91d6a4665 100644
--- a/crates/ide_db/src/helpers/import_assets.rs
+++ b/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),
                     ));
diff --git a/crates/syntax/src/ast/make.rs b/crates/syntax/src/ast/make.rs
index c6a7b99b7..94d4f2cf0 100644
--- a/crates/syntax/src/ast/make.rs
+++ b/crates/syntax/src/ast/make.rs
@@ -29,9 +29,13 @@ pub fn ty(text: &str) -> ast::Type {
 pub fn ty_unit() -> ast::Type {
     ty("()")
 }
-// FIXME: handle types of length == 1
 pub fn ty_tuple(types: impl IntoIterator<Item = ast::Type>) -> ast::Type {
-    let contents = types.into_iter().join(", ");
+    let mut count: usize = 0;
+    let mut contents = types.into_iter().inspect(|_| count += 1).join(", ");
+    if count == 1 {
+        contents.push(',');
+    }
+
     ty(&format!("({})", contents))
 }
 // FIXME: handle path to type
@@ -292,11 +296,13 @@ pub fn wildcard_pat() -> ast::WildcardPat {
 
 /// Creates a tuple of patterns from an iterator of patterns.
 ///
-/// Invariant: `pats` must be length > 1
-///
-/// FIXME handle `pats` length == 1
+/// Invariant: `pats` must be length > 0
 pub fn tuple_pat(pats: impl IntoIterator<Item = ast::Pat>) -> ast::TuplePat {
-    let pats_str = pats.into_iter().map(|p| p.to_string()).join(", ");
+    let mut count: usize = 0;
+    let mut pats_str = pats.into_iter().inspect(|_| count += 1).join(", ");
+    if count == 1 {
+        pats_str.push(',');
+    }
     return from_text(&format!("({})", pats_str));
 
     fn from_text(text: &str) -> ast::TuplePat {