Add diagnostics for enum names and variants

crates/ide/src/diagnostics.rs

@@ -851,6 +851,32 @@ pub struct TestStruct { one: i32 }
 pub fn some_fn(val: TestStruct) -> TestStruct {
     TestStruct { one: val.one + 1 }
 }
+"#,
+        );
+
+        check_fixes(
+            r#"
+pub fn some_fn(NonSnakeCase<|>: u8) -> u8 {
+    NonSnakeCase
+}
+"#,
+            r#"
+pub fn some_fn(non_snake_case: u8) -> u8 {
+    non_snake_case
+}
+"#,
+        );
+
+        check_fixes(
+            r#"
+pub fn SomeFn<|>(val: u8) -> u8 {
+    if val != 0 { SomeFn(val - 1) } else { val }
+}
+"#,
+            r#"
+pub fn some_fn(val: u8) -> u8 {
+    if val != 0 { some_fn(val - 1) } else { val }
+}
 "#,
         );
     }