Simplify generated enum code -- write it in terms of public APIs (#503)

Author: alex

asn1_derive/src/lib.rs

@@ -566,31 +566,31 @@ fn generate_enum_read_block(
             OpType::Explicit(arg) => {
                 let tag = arg.value;
                 read_blocks.push(quote::quote! {
-                    if tlv.tag() == asn1::explicit_tag(#tag) {
+                    if asn1::Explicit::<#ty, #tag>::can_parse(tlv.tag()) {
                         return Ok(#name::#ident(asn1::parse(
                             tlv.full_data(),
                             |p| Ok(p.read_element::<asn1::Explicit<_, #tag>>()#add_error_location?.into_inner())
                         )?))
                     }
                 });
                 can_parse_blocks.push(quote::quote! {
-                    if tag == asn1::explicit_tag(#tag) {
+                    if asn1::Explicit::<#ty, #tag>::can_parse(tag) {
                         return true;
                     }
                 });
             }
             OpType::Implicit(arg) => {
                 let tag = arg.value;
                 read_blocks.push(quote::quote! {
-                    if tlv.tag() == asn1::implicit_tag(#tag, <#ty as asn1::SimpleAsn1Readable>::TAG) {
+                    if asn1::Implicit::<#ty, #tag>::can_parse(tlv.tag()) {
                         return Ok(#name::#ident(asn1::parse(
                             tlv.full_data(),
                             |p| Ok(p.read_element::<asn1::Implicit<_, #tag>>()#add_error_location?.into_inner())
                         )?))
                     }
                 });
                 can_parse_blocks.push(quote::quote! {
-                    if tag == asn1::implicit_tag(#tag, <#ty as asn1::SimpleAsn1Readable>::TAG) {
+                    if asn1::Implicit::<#ty, #tag>::can_parse(tag) {
                         return true;
                     }
                 });

src/lib.rs

@@ -231,3 +231,14 @@ pub fn write_defined_by<T: Asn1Writable, U: Asn1DefinedByWritable<T>>(
 pub fn writable_defined_by_item<T: Asn1Writable, U: Asn1DefinedByWritable<T>>(v: &U) -> &T {
     v.item()
 }
+
+#[cfg(test)]
+mod tests {
+    #[test]
+    fn test_implicit_tag() {
+        let t = crate::implicit_tag(3, crate::Tag::primitive(2));
+        assert_eq!(t.as_u8(), Some(0x83));
+        let t = crate::implicit_tag(3, crate::Tag::constructed(2));
+        assert_eq!(t.as_u8(), Some(0xa3));
+    }
+}