Add helper methods for unstable options

One method is used to determine if any unstable options were used on
nightly.

The other method provides us with easy access to the underlying Vec
where all the unstable options were set.

Author: ytmimi

src/config/config_type.rs

@@ -147,6 +147,22 @@ macro_rules! create_config {
                 ConfigWasSet(self)
             }
 
+            /// Returns None if using nightly or if no unstable options were set.
+            /// Otherwise, return all unstable options set by the user.
+            #[allow(unreachable_pub)]
+            pub fn unstable_options_set_on_stable_channel(&self) -> Option<&Vec<String>> {
+                if crate::is_nightly_channel!() {
+                    None
+                } else {
+                    self.configured_unstable_options.as_ref()
+                }
+            }
+
+            /// Returns true if any unstable options were set while on the stable channel
+            #[allow(unreachable_pub)]
+            pub fn using_unstable_options_on_stable_channel(&self) -> bool {
+                self.configured_unstable_options.is_some()
+            }
             fn fill_from_parsed_config(mut self, parsed: PartialConfig, dir: &Path) -> Config {
                 let mut unstable_options = vec![];
             $(

src/config/mod.rs

@@ -549,6 +549,35 @@ mod test {
         assert!(config.license_template.is_none());
     }
 
+    #[test]
+    fn test_on_stable_get_all_unstable_options_set_in_toml() {
+        if crate::is_nightly_channel!() {
+            // This test requires non-nightly
+            return;
+        }
+        let toml = r#"
+            reorder_impl_items = true
+        "#;
+        let config = Config::from_toml(toml, Path::new("")).unwrap();
+        assert_eq!(
+            config.unstable_options_set_on_stable_channel().unwrap(),
+            &vec!["reorder_impl_items = true"]
+        )
+    }
+
+    #[test]
+    fn test_on_stable_are_any_unstable_options_set_in_toml() {
+        if crate::is_nightly_channel!() {
+            // This test requires non-nightly
+            return;
+        }
+        let toml = r#"
+            reorder_impl_items = true
+        "#;
+        let config = Config::from_toml(toml, Path::new("")).unwrap();
+        assert!(config.using_unstable_options_on_stable_channel())
+    }
+
     #[test]
     fn test_dump_default_config() {
         let default_config = format!(