Const enum variants names (#75)

* Add implementing const `VARIANTS` by `EnumVariantsNames`, deprecate old `::variants` * Move `const VARIANTS` to `VariantNames` trait * Remove `VariantNames::variants` function
Peternator7 · Dec 12, 2019 · eea32db · eea32db
1 parent a94c8b0
commit eea32db
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Showing 3 changed files with 10 additions and 18 deletions.
diff --git a/strum/src/lib.rs b/strum/src/lib.rs
@@ -221,7 +221,8 @@ pub trait EnumCount {
 /// A trait for retrieving the names of each variant in Enum. This trait can
 /// be autoderived by `strum_macros`.
 pub trait VariantNames {
-    fn variants() -> &'static [&'static str];
+    /// Names of the variants of this enum
+    const VARIANTS: &'static [&'static str];
 }
 
 #[cfg(feature = "derive")]

diff --git a/strum_macros/src/macros/enum_variant_names.rs b/strum_macros/src/macros/enum_variant_names.rs
@@ -26,13 +26,7 @@ pub fn enum_variant_names_inner(ast: &syn::DeriveInput) -> TokenStream {
 
     quote! {
         impl #impl_generics ::strum::VariantNames for #name #ty_generics #where_clause {
-            /// Return a slice containing the names of the variants of this enum
-            #[allow(dead_code)]
-            fn variants() -> &'static [&'static str] {
-                &[
-                    #(#names),*
-                ]
-            }
+            const VARIANTS: &'static [&'static str] = &[ #(#names),* ];
         }
     }
 }
diff --git a/strum_tests/tests/enum_variant_names.rs b/strum_tests/tests/enum_variant_names.rs
@@ -15,7 +15,7 @@ fn simple() {
         Yellow,
     }
 
-    assert_eq!(&Color::variants(), &["Red", "Blue", "Yellow"]);
+    assert_eq!(Color::VARIANTS, &["Red", "Blue", "Yellow"]);
 }
 
 #[test]
@@ -29,7 +29,7 @@ fn variant_names_trait() {
     }
 
     fn generic_function<T: VariantNames>() {
-        assert_eq!(T::variants(), &["Red", "Blue", "Yellow"]);
+        assert_eq!(T::VARIANTS, &["Red", "Blue", "Yellow"]);
     }
 
     generic_function::<Color>();
@@ -47,10 +47,7 @@ fn plain_kebab() {
         RebeccaPurple,
     }
 
-    assert_eq!(
-        &Color::variants(),
-        &["red", "blue", "yellow", "rebecca-purple"]
-    );
+    assert_eq!(Color::VARIANTS, &["red", "blue", "yellow", "rebecca-purple"]);
 }
 
 #[test]
@@ -66,7 +63,7 @@ fn non_plain_camel() {
     }
 
     assert_eq!(
-        &Color::variants(),
+        Color::VARIANTS,
         &["deep-pink", "green-yellow", "cornflower-blue", "other"]
     );
 }
@@ -83,14 +80,14 @@ fn clap_and_structopt() {
     }
 
     assert_eq!(
-        &Color::variants(),
+        Color::VARIANTS,
         &["red", "blue", "yellow", "rebecca-purple"]
     );
 
     let _clap_example = clap::App::new("app").arg(
         clap::Arg::with_name("color")
             .long("color")
-            .possible_values(Color::variants())
+            .possible_values(Color::VARIANTS)
             .case_insensitive(true),
     );
 
@@ -101,7 +98,7 @@ fn clap_and_structopt() {
         #[structopt(
             long = "color",
             default_value = "Color::Blue",
-            raw(possible_values = "Color::variants()")
+            raw(possible_values = "Color::VARIANTS")
         )]
         color: Color,
     }