Add a test to ensure we invalidate brackets not only on edits (#45219)

Follow-up of https://github.com/zed-industries/zed/pull/45187

Release Notes:

- N/A

crates/editor/src/bracket_colorization.rs

@@ -348,6 +348,61 @@ where
         );
     }
 
+    #[gpui::test]
+    async fn test_bracket_colorization_after_language_swap(cx: &mut gpui::TestAppContext) {
+        init_test(cx, |language_settings| {
+            language_settings.defaults.colorize_brackets = Some(true);
+        });
+
+        let language_registry = Arc::new(language::LanguageRegistry::test(cx.executor()));
+        language_registry.add(markdown_lang());
+        language_registry.add(rust_lang());
+
+        let mut cx = EditorTestContext::new(cx).await;
+        cx.update_buffer(|buffer, cx| {
+            buffer.set_language_registry(language_registry.clone());
+            buffer.set_language(Some(markdown_lang()), cx);
+        });
+
+        cx.set_state(indoc! {r#"
+            fn main() {
+                let v: Vec<Stringˇ> = vec![];
+            }
+        "#});
+        cx.executor().advance_clock(Duration::from_millis(100));
+        cx.executor().run_until_parked();
+
+        assert_eq!(
+            r#"fn main«1()1» «1{
+    let v: Vec<String> = vec!«2[]2»;
+}1»
+
+1 hsla(207.80, 16.20%, 69.19%, 1.00)
+2 hsla(29.00, 54.00%, 65.88%, 1.00)
+"#,
+            &bracket_colors_markup(&mut cx),
+            "Markdown does not colorize <> brackets"
+        );
+
+        cx.update_buffer(|buffer, cx| {
+            buffer.set_language(Some(rust_lang()), cx);
+        });
+        cx.executor().advance_clock(Duration::from_millis(100));
+        cx.executor().run_until_parked();
+
+        assert_eq!(
+            r#"fn main«1()1» «1{
+    let v: Vec«2<String>2» = vec!«2[]2»;
+}1»
+
+1 hsla(207.80, 16.20%, 69.19%, 1.00)
+2 hsla(29.00, 54.00%, 65.88%, 1.00)
+"#,
+            &bracket_colors_markup(&mut cx),
+            "After switching to Rust, <> brackets are now colorized"
+        );
+    }
+
     #[gpui::test]
     async fn test_bracket_colorization_when_editing(cx: &mut gpui::TestAppContext) {
         init_test(cx, |language_settings| {