Fix building on rust < 1.34

strum_macros/src/lib.rs

@@ -381,7 +381,8 @@ pub fn enum_iter(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
     toks.into()
 }
 
-/// Add a function to enum that allows accessing variants by its discriminant
+/// Add a function to enum that allows accessing variants by its discriminant.
+/// On Rust 1.34 and above, std::convert::TryFrom<TDiscriminant> will be derived as well.
 ///
 /// This macro adds a standalone function to obtain an enum variant by its discriminant. The macro adds
 /// `from_repr(discriminant: usize) -> Option<YourEnum>` as a standalone function on the enum. For

strum_tests/Cargo.toml

@@ -11,6 +11,7 @@ clap = "=2.33.0"
 enum_variant_type = "=0.2.0"
 structopt = "0.2.18"
 bitflags = "=1.2"
+if_rust_version = "1.0"
 
 [dev-dependencies]
 rustversion = "1.0"

strum_tests/tests/from_repr.rs

@@ -1,6 +1,4 @@
-use core::convert::TryFrom;
+use if_rust_version::if_rust_version;
-use core::convert::TryInto;
-
 use strum::FromRepr;
 
 #[derive(Debug, FromRepr, PartialEq)]
@@ -18,13 +16,17 @@ enum Week {
 macro_rules! assert_eq_repr {
     ( $type:ident::from_repr($number:literal), Some($enum:expr) ) => {
         assert_eq!($type::from_repr($number), Some($enum));
-        assert_eq!(TryInto::<$type>::try_into($number), Ok($enum));
+        if_rust_version! { >= 1.34 {
-        assert_eq!(<$type as TryFrom<_>>::try_from($number), Ok($enum));
+            assert_eq!(core::convert::TryInto::<$type>::try_into($number), Ok($enum));
+            assert_eq!(<$type as core::convert::TryFrom<_>>::try_from($number), Ok($enum));
+        }}
     };
     ( $type:ident::from_repr($number:literal), None ) => {
         assert_eq!($type::from_repr($number), None);
-        assert_eq!(TryInto::<$type>::try_into($number), Err(::strum::ParseError::VariantNotFound));
+        if_rust_version! { >= 1.34 {
-        assert_eq!(<$type as TryFrom<_>>::try_from($number), Err(::strum::ParseError::VariantNotFound));
+            assert_eq!(core::convert::TryInto::<$type>::try_into($number), Err(::strum::ParseError::VariantNotFound));
+            assert_eq!(<$type as core::convert::TryFrom<_>>::try_from($number), Err(::strum::ParseError::VariantNotFound));
+        }}
     };
 }