Add derive macros for enums (#287)

* add derive macros for enums

* set up derive macro

* fix build

* more options

* fix build

* fix redox build

* more improvements

* lead with double colon

crates/steel-core/src/steel_vm/engine.rs

@@ -2317,3 +2317,65 @@ mod engine_sandbox_tests {
             .is_err());
     }
 }
+
+#[cfg(test)]
+mod derive_macro_tests {
+    use super::*;
+
+    #[derive(steel_derive::_Steel, PartialEq, Debug)]
+    #[steel(equality, getters, constructors)]
+    enum TestEnumVariants {
+        Foo,
+        Bar,
+        Baz(usize, usize),
+        Bazinga {
+            foo: usize,
+            bananas: usize,
+        },
+        #[steel(ignore)]
+        Ignored(SteelString),
+    }
+
+    fn test() {
+        let mut module = BuiltInModule::new("foo");
+        TestEnumVariants::register_enum_variants(&mut module);
+    }
+
+    enum Foo {
+        Bananas(usize, usize, usize, usize),
+        Bananas2(usize, usize, usize, usize),
+    }
+
+    #[test]
+    fn test_primitives_are_registered() {
+        let mut engine = Engine::new();
+        let mut module = BuiltInModule::new("foo");
+
+        TestEnumVariants::register_enum_variants(&mut module);
+        engine.register_module(module);
+
+        engine
+            .run(
+                r#"
+(require-builtin foo)
+(assert! (TestEnumVariants-Foo? (TestEnumVariants-Foo)))
+(assert! (TestEnumVariants-Bar? (TestEnumVariants-Bar)))
+(assert! (TestEnumVariants-Baz? (TestEnumVariants-Baz 10 20)))
+(assert! (TestEnumVariants-Bazinga? (TestEnumVariants-Bazinga 100 200)))
+
+(assert! (equal? (TestEnumVariants-Bazinga-foo (TestEnumVariants-Bazinga 100 200)) 100))
+(assert! (equal? (TestEnumVariants-Bazinga-bananas (TestEnumVariants-Bazinga 100 200)) 200))
+(assert! (equal? (TestEnumVariants-Baz-0 (TestEnumVariants-Baz 100 200)) 100))
+(assert! (equal? (TestEnumVariants-Baz-1 (TestEnumVariants-Baz 100 200)) 200))
+
+(assert! (not (equal? 100 (TestEnumVariants-Foo))))
+
+            "#,
+            )
+            .unwrap();
+
+        assert!(engine
+            .run(r#"(TestEnumVariants-Ignored "Hello world")"#)
+            .is_err())
+    }
+}