fix: fix const into str implementation, add test cases

strum_macros/src/macros/strings/as_ref_str.rs

@@ -116,8 +116,8 @@ pub fn as_static_str_inner(
             }
         },
         GenerateTraitVariant::From  => quote! {
-            impl #name #ty_generics {
-                pub const fn into_str(&self) -> &'static str #where_clause {
+            impl #impl_generics #name #ty_generics #where_clause {
+                pub const fn into_str(&self) -> &'static str {
                     match *self {
                         #(#arms3),*
                     }

strum_tests/tests/as_ref_str.rs

@@ -111,3 +111,77 @@ fn brightness_serialize_all() {
     assert_eq!("dim", <&'static str>::from(Brightness::Dim { glow: 0 }));
     assert_eq!("Bright", <&'static str>::from(Brightness::BrightWhite));
 }
+
+#[derive(IntoStaticStr)]
+#[strum(const_into_str)]
+enum Bar<'a, T>
+    where
+        T: AsRef<str>,
+{
+    A(T),
+    B,
+    C(&'a i32),
+    #[strum(serialize = "Dark")]
+    D,
+    #[strum(to_string = "Green")]
+    G,
+    #[strum(serialize = "b", to_string = "blue")]
+    Blue { hue: usize },
+    #[strum(serialize = "y", serialize = "yellow")]
+    Yellow,
+}
+
+#[derive(IntoStaticStr)]
+#[strum(const_into_str)]
+enum Baz<'a, T> {
+    A(T),
+    C(&'a i32),
+}
+
+#[derive(IntoStaticStr)]
+#[strum(serialize_all = "snake_case")]
+#[strum(const_into_str)]
+enum BrightnessConst {
+    DarkBlack,
+    Dim {
+        glow: usize,
+    },
+    #[strum(serialize = "Bright")]
+    BrightWhite,
+}
+
+#[test]
+fn test_const_into_static_str() {
+
+    const A: &'static str = Bar::A("foo").into_str();
+    assert_eq!("A", A);
+    const B: &'static str = Bar::B::<&str>.into_str();
+    assert_eq!("B", B);
+    const C: &'static str = Bar::C::<&str>(&12).into_str();
+    assert_eq!("C", C);
+
+    const D: &'static str = Bar::D::<&str>.into_str();
+    assert_eq!("Dark", D);
+
+    const G: &'static str = Bar::G::<&str>.into_str();
+    assert_eq!("Green", G);
+
+    const BLUE: &'static str = Bar::Blue::<&str>{ hue: 2 }.into_str();
+    assert_eq!("blue", BLUE);
+
+    const YELLOW: &'static str = Bar::Yellow::<&str>.into_str();
+    assert_eq!("yellow", YELLOW);
+
+    const BAZ_A: &'static str = Baz::A("foo").into_str();
+    assert_eq!("A", BAZ_A);
+
+    const BAZ_C: &'static str = Baz::C::<&str>(&6).into_str();
+    assert_eq!("C", BAZ_C);
+
+    const DARK_BLACK: &'static str = BrightnessConst::DarkBlack.into_str();
+    assert_eq!("dark_black", DARK_BLACK);
+    const DIM: &'static str = BrightnessConst::Dim {glow:1}.into_str();
+    assert_eq!("dim", DIM);
+    const BRIGHT_WHITE: &'static str = BrightnessConst::BrightWhite.into_str();
+    assert_eq!("Bright", BRIGHT_WHITE);
+}