WIP: Add create_function assist

Author: TimoFreiberg

crates/ra_assists/src/doc_tests/generated.rs

@@ -58,6 +58,33 @@ fn main() {
     )
 }
 
+#[test]
+fn doctest_add_function() {
+    check(
+        "add_function",
+        r#####"
+struct Baz;
+fn baz() -> Baz { Baz }
+fn foo() {
+     bar<|>("", baz());
+}
+
+"#####,
+        r#####"
+struct Baz;
+fn baz() -> Baz { Baz }
+fn foo() {
+     bar("", baz());
+}
+
+fn bar(arg: &str, baz: Baz) {
+    <|>todo!()
+}
+
+"#####,
+    )
+}
+
 #[test]
 fn doctest_add_hash() {
     check(