1 files changed, 149 insertions, 0 deletions

diff --git a/crates/ide_db/src/traits.rs b/crates/ide_db/src/traits.rs
index dcd61a595..f57b6dd91 100644
--- a/crates/ide_db/src/traits.rs
+++ b/crates/ide_db/src/traits.rs
@@ -76,3 +76,152 @@ pub fn get_missing_assoc_items(
             .collect()
     })
 }
+
+#[cfg(test)]
+mod tests {
+    use crate::RootDatabase;
+    use base_db::{fixture::ChangeFixture, FilePosition};
+    use expect_test::{expect, Expect};
+    use hir::Semantics;
+    use syntax::ast::{self, AstNode};
+    use test_utils::RangeOrOffset;
+
+    /// Creates analysis from a multi-file fixture, returns positions marked with <|>.
+    pub(crate) fn position(ra_fixture: &str) -> (RootDatabase, FilePosition) {
+        let change_fixture = ChangeFixture::parse(ra_fixture);
+        let mut database = RootDatabase::default();
+        database.apply_change(change_fixture.change);
+        let (file_id, range_or_offset) =
+            change_fixture.file_position.expect("expected a marker (<|>)");
+        let offset = match range_or_offset {
+            RangeOrOffset::Range(_) => panic!(),
+            RangeOrOffset::Offset(it) => it,
+        };
+        (database, FilePosition { file_id, offset })
+    }
+
+    fn check_trait(ra_fixture: &str, expect: Expect) {
+        let (db, position) = position(ra_fixture);
+        let sema = Semantics::new(&db);
+        let file = sema.parse(position.file_id);
+        let impl_block: ast::Impl =
+            sema.find_node_at_offset_with_descend(file.syntax(), position.offset).unwrap();
+        let trait_ = crate::traits::resolve_target_trait(&sema, &impl_block);
+        let actual = match trait_ {
+            Some(trait_) => trait_.name(&db).to_string(),
+            None => String::new(),
+        };
+        expect.assert_eq(&actual);
+    }
+
+    fn check_missing_assoc(ra_fixture: &str, expect: Expect) {
+        let (db, position) = position(ra_fixture);
+        let sema = Semantics::new(&db);
+        let file = sema.parse(position.file_id);
+        let impl_block: ast::Impl =
+            sema.find_node_at_offset_with_descend(file.syntax(), position.offset).unwrap();
+        let items = crate::traits::get_missing_assoc_items(&sema, &impl_block);
+        let actual = items
+            .into_iter()
+            .map(|item| item.name(&db).unwrap().to_string())
+            .collect::<Vec<_>>()
+            .join("\n");
+        expect.assert_eq(&actual);
+    }
+
+    #[test]
+    fn resolve_trait() {
+        check_trait(
+            r#"
+pub trait Foo {
+    fn bar();
+}
+impl Foo for u8 {
+    <|>
+}
+            "#,
+            expect![["Foo"]],
+        );
+        check_trait(
+            r#"
+pub trait Foo {
+    fn bar();
+}
+impl Foo for u8 {
+    fn bar() {
+        fn baz() {
+            <|>
+        }
+        baz();
+    }
+}
+            "#,
+            expect![["Foo"]],
+        );
+        check_trait(
+            r#"
+pub trait Foo {
+    fn bar();
+}
+pub struct Bar;
+impl Bar {
+    <|>
+}
+            "#,
+            expect![[""]],
+        );
+    }
+
+    #[test]
+    fn missing_assoc_items() {
+        check_missing_assoc(
+            r#"
+pub trait Foo {
+    const FOO: u8;
+    fn bar();
+}
+impl Foo for u8 {
+    <|>
+}"#,
+            expect![[r#"
+                FOO
+                bar"#]],
+        );
+
+        check_missing_assoc(
+            r#"
+pub trait Foo {
+    const FOO: u8;
+    fn bar();
+}
+impl Foo for u8 {
+    const FOO: u8 = 10;
+    <|>
+}"#,
+            expect![[r#"
+                bar"#]],
+        );
+
+        check_missing_assoc(
+            r#"
+pub trait Foo {
+    const FOO: u8;
+    fn bar();
+}
+impl Foo for u8 {
+    const FOO: u8 = 10;
+    fn bar() {<|>}
+}"#,
+            expect![[r#""#]],
+        );
+
+        check_missing_assoc(
+            r#"
+pub struct Foo;
+impl Foo {
+    fn bar() {<|>}
+}"#,
+            expect![[r#""#]],
+        );
+    }
+}