Migrate to thiserror (#7177)

* Migrate to thiserror

* Discourage the use of other modules' Result alias

`io::Result` set a bad precedent. Don't import other `Result`
aliases.

programs/ownable/Cargo.toml

@@ -15,6 +15,7 @@ serde_derive = "1.0.103"
 solana-sdk = { path = "../../sdk", version = "0.22.0" }
 num-derive = "0.3"
 num-traits = "0.2"
+thiserror = "1.0"
 
 [dev-dependencies]
 solana-runtime = { path = "../../runtime", version = "0.22.0" }

programs/ownable/src/ownable_instruction.rs

@@ -5,9 +5,11 @@ use solana_sdk::{
     pubkey::Pubkey,
     system_instruction,
 };
+use thiserror::Error;
 
-#[derive(Debug, Clone, PartialEq, FromPrimitive, ToPrimitive)]
+#[derive(Error, Debug, Clone, PartialEq, FromPrimitive, ToPrimitive)]
 pub enum OwnableError {
+    #[error("incorrect error")]
     IncorrectOwner,
 }
 
@@ -17,19 +19,6 @@ impl<T> DecodeError<T> for OwnableError {
     }
 }
 
-impl std::fmt::Display for OwnableError {
-    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
-        write!(
-            f,
-            "{}",
-            match self {
-                OwnableError::IncorrectOwner => "incorrect owner",
-            }
-        )
-    }
-}
-impl std::error::Error for OwnableError {}
-
 fn initialize_account(account_pubkey: &Pubkey, owner_pubkey: &Pubkey) -> Instruction {
     let keys = vec![AccountMeta::new(*account_pubkey, false)];
     Instruction::new(crate::id(), &owner_pubkey, keys)