[review] update override_value

Author: tommilligan

src/config/config_type.rs

@@ -161,28 +161,13 @@ macro_rules! create_config {
 
             fn fill_from_parsed_config(mut self, parsed: PartialConfig, dir: &Path) -> Config {
             $(
-                if let Some(val) = parsed.$i {
-                    let nightly = crate::is_nightly_channel!();
+                if let Some(option_value) = parsed.$i {
                     let option_stable = self.$i.3;
-                    let variant_stable = val.stable_variant();
-
-                    match (nightly, option_stable, variant_stable) {
-                        // Stable with an unstable option
-                        (false, false, _) => {
-                            eprintln!("Warning: can't set `{} = {:?}`, unstable features are only \
-                                       available in nightly channel.", stringify!($i), val);
-                        },
-                        // Stable with a stable option, but an unstable variant
-                        (false, true, false) => {
-                        eprintln!("Warning: can't set `{} = {:?}`, unstable variants are only \
-                                   available in nightly channel.", stringify!($i), val);
-                        },
-                        // Nightly: everything allowed
-                        // Stable with stable option and variant: allowed
-                        (true, _, _) | (false, true, true) => {
-                            self.$i.1 = true;
-                            self.$i.2 = val;
-                        },
+                    if $crate::config::config_type::is_stable_option_and_value(
+                        stringify!($i), option_stable, &option_value
+                    ) {
+                        self.$i.1 = true;
+                        self.$i.2 = option_value;
                     }
                 }
             )+
@@ -249,12 +234,18 @@ macro_rules! create_config {
                 match key {
                     $(
                         stringify!($i) => {
-                            self.$i.1 = true;
-                            self.$i.2 = val.parse::<$ty>()
+                            let option_value = val.parse::<$ty>()
                                 .expect(&format!("Failed to parse override for {} (\"{}\") as a {}",
                                                  stringify!($i),
                                                  val,
                                                  stringify!($ty)));
+                            let option_stable = self.$i.3;
+                            if $crate::config::config_type::is_stable_option_and_value(
+                                stringify!($i), option_stable, &option_value
+                            ) {
+                                self.$i.1 = true;
+                                self.$i.2 = option_value;
+                            }
                         }
                     )+
                     _ => panic!("Unknown config key in override: {}", key)
@@ -452,3 +443,38 @@ macro_rules! create_config {
         }
     )
 }
+
+pub(crate) fn is_stable_option_and_value<T>(
+    option_name: &str,
+    option_stable: bool,
+    option_value: &T,
+) -> bool
+where
+    T: PartialEq + std::fmt::Debug + ConfigType,
+{
+    let nightly = crate::is_nightly_channel!();
+    let variant_stable = option_value.stable_variant();
+    match (nightly, option_stable, variant_stable) {
+        // Stable with an unstable option
+        (false, false, _) => {
+            eprintln!(
+                "Warning: can't set `{} = {:?}`, unstable features are only \
+                       available in nightly channel.",
+                option_name, option_value
+            );
+            false
+        }
+        // Stable with a stable option, but an unstable variant
+        (false, true, false) => {
+            eprintln!(
+                "Warning: can't set `{} = {:?}`, unstable variants are only \
+                       available in nightly channel.",
+                option_name, option_value
+            );
+            false
+        }
+        // Nightly: everything allowed
+        // Stable with stable option and variant: allowed
+        (true, _, _) | (false, true, true) => true,
+    }
+}