Add tests for nostd environment

Cargo.toml

@@ -2,7 +2,7 @@
 members = [
     "strum",
     "strum_macros",
-    "strum_tests"
+    "strum_tests",
+    "strum_nostd_tests"
 ]
  
-exclude = [ "strum_tests_rename" ]

strum_nostd_tests/Cargo.toml

@@ -0,0 +1,13 @@
+[package]
+name = "strum_nostd_tests"
+version = "0.23.1"
+edition = "2018"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+strum = { path = "../strum", features = ["derive"] }
+strum_macros = { path = "../strum_macros", features = [] }
+
+[dev-dependencies]
+rustversion = "1.0"

strum_nostd_tests/src/lib.rs

@@ -0,0 +1,37 @@
+#![no_std]
+
+#[cfg(test)]
+mod tests {
+    use core::str::FromStr;
+    use strum::EnumString;
+
+    #[derive(Debug, Eq, PartialEq, EnumString)]
+    enum Color {
+        Red,
+        Blue {
+            hue: usize,
+        },
+        #[strum(serialize = "y", serialize = "yellow")]
+        Yellow,
+        #[strum(to_string = "purp")]
+        Purple,
+        #[strum(serialize = "blk", serialize = "Black", ascii_case_insensitive)]
+        Black,
+    }
+
+    #[test]
+    fn from_str_no_std() {
+        assert_eq!(Color::Yellow, Color::from_str("yellow").unwrap());
+    }
+
+    #[test]
+    #[rustversion::since(1.34)]
+    fn try_from_str_no_std() {
+        use core::convert::TryFrom;
+        assert_eq!(Color::Yellow, Color::try_from("yellow").unwrap());
+    }
+
+    #[test]
+    #[rustversion::before(1.34)]
+    fn try_from_str_no_std() {}
+}

strum_tests/tests/from_str.rs

@@ -131,7 +131,7 @@ fn lifetime_test() {
 #[derive(Debug, Eq, PartialEq, EnumString)]
 enum Generic<T: Default> {
     Gen(T),
-    None,
+    Error,
 }
 
 #[test]