Custom error decoder (#3783)

automerge

programs/token_api/src/token_state.rs

@@ -1,15 +1,23 @@
 use log::*;
+use num_derive::FromPrimitive;
 use serde_derive::{Deserialize, Serialize};
 use solana_sdk::account::KeyedAccount;
+use solana_sdk::instruction_processor_utils::DecodeError;
 use solana_sdk::pubkey::Pubkey;
 
-#[derive(Serialize, Debug, PartialEq)]
+#[derive(Serialize, Debug, PartialEq, FromPrimitive)]
 pub enum TokenError {
     InvalidArgument,
     InsufficentFunds,
     NotOwner,
 }
 
+impl<T> DecodeError<T> for TokenError {
+    fn type_of(&self) -> &'static str {
+        "TokenError"
+    }
+}
+
 impl std::fmt::Display for TokenError {
     fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
         write!(f, "error")