inline parameters for a function description #6002

Signed-off-by: Benjamin Coenen <5719034+bnjjj@users.noreply.github.com>

crates/ide/src/completion/complete_qualified_path.rs

@@ -730,4 +730,26 @@ fn f() {}
             expect![[""]],
         );
     }
+
+    #[test]
+    fn completes_function() {
+        check(
+            r#"
+fn foo(
+    a: i32,
+    b: i32
+) {
+
+}
+
+fn main() {
+    fo<|>
+}
+"#,
+            expect![[r#"
+                fn foo(…) fn foo(a: i32, b: i32)
+                fn main() fn main()
+            "#]],
+        );
+    }
 }

crates/ide/src/display.rs

@@ -41,7 +41,13 @@ pub(crate) fn function_declaration(node: &ast::Fn) -> String {
         format_to!(buf, "{}", type_params);
     }
     if let Some(param_list) = node.param_list() {
-        format_to!(buf, "{}", param_list);
+        let mut params = match param_list.self_param() {
+            Some(self_param) => vec![self_param.to_string()],
+            None => vec![],
+        };
+        params.extend(param_list.params().map(|param| param.to_string()));
+        // Useful to inline parameters
+        format_to!(buf, "({})", params.join(", "));
     }
     if let Some(ret_type) = node.ret_type() {
         if ret_type.ty().is_some() {