Resolve issues mentioned in review

Author: Wiezzel

examples/psp22-extension/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "psp22_extension"
-version = "3.0.1"
+version = "4.0.0-alpha.1"
 authors = ["Parity Technologies <admin@parity.io>"]
 edition = "2021"
 publish = false

examples/psp22-extension/lib.rs

@@ -10,7 +10,7 @@ type DefaultBalance = <ink_env::DefaultEnvironment as Environment>::Balance;
 
 #[ink::chain_extension]
 pub trait Psp22Extension {
-    type ErrorCode = Psp22ErrorCode;
+    type ErrorCode = Psp22Error;
 
     // PSP22 Metadata interfaces
 
@@ -77,33 +77,21 @@ pub trait Psp22Extension {
     ) -> Result<()>;
 }
 
-#[derive(scale::Encode, scale::Decode)]
-#[cfg_attr(feature = "std", derive(scale_info::TypeInfo))]
-pub enum Psp22ErrorCode {
-    TotalSupplyFailed,
-}
-
 #[derive(scale::Encode, scale::Decode)]
 #[cfg_attr(feature = "std", derive(scale_info::TypeInfo))]
 pub enum Psp22Error {
-    ErrorCode(Psp22ErrorCode),
+    TotalSupplyFailed,
 }
 
 pub type Result<T> = core::result::Result<T, Psp22Error>;
 
-impl From<Psp22ErrorCode> for Psp22Error {
-    fn from(error_code: Psp22ErrorCode) -> Self {
-        Self::ErrorCode(error_code)
-    }
-}
-
 impl From<scale::Error> for Psp22Error {
     fn from(_: scale::Error) -> Self {
         panic!("encountered unexpected invalid SCALE encoding")
     }
 }
 
-impl ink_env::chain_extension::FromStatusCode for Psp22ErrorCode {
+impl ink_env::chain_extension::FromStatusCode for Psp22Error {
     fn from_status_code(status_code: u32) -> core::result::Result<(), Self> {
         match status_code {
             0 => Ok(()),
@@ -138,10 +126,13 @@ mod psp22_ext {
         Vec,
     };
 
+    /// A chain extension which implements the PSP-22 fungible token standard.
+    /// For more details see <https://github.com/w3f/PSPs/blob/master/PSPs/psp-22.md>
     #[ink(storage)]
     pub struct Psp22Extension {}
 
     impl Psp22Extension {
+        /// Creates a new instance of this contract.
         #[ink(constructor)]
         pub fn new() -> Self {
             Psp22Extension {}

examples/psp22-extension/runtime/psp22-extension-example.rs

@@ -210,7 +210,7 @@ where
         target: "runtime",
         "[ChainExtension]|call|transfer"
     );
-    
+
     Ok(())
 }
 
@@ -350,7 +350,7 @@ where
         target: "runtime",
         "[ChainExtension]|call|decrease_allowance"
     );
-    
+
     Ok(())
 }