docs(erc20): improve docs for ERC20Burnable (#27)

contracts/src/erc20/extensions/burnable.rs

@@ -1,8 +1,16 @@
 //! Optional Burnable extension of the ERC-20 standard.
+
 #[macro_export]
 /// This macro provides implementation of ERC-20 Burnable extension.
-/// It adds `burn` and `burn_from` function.
-macro_rules! derive_erc20_burnable {
+///
+/// It adds `burn` and `burn_from` function
+/// to a custom token that contains `ERC20 erc20` attribute.
+///
+/// Requires import of:
+/// * alloy_primitives::{Address, U256}
+/// * contracts::erc20::{Error, ERC20}
+/// * stylus_sdk::msg
+macro_rules! impl_erc20_burnable {
     () => {
         /// Destroys a `value` amount of tokens from the caller.
         /// lowering the total supply.
@@ -74,7 +82,7 @@ mod tests {
     #[external]
     #[inherit(ERC20)]
     impl TestERC20Burnable {
-        derive_erc20_burnable!();
+        impl_erc20_burnable!();
     }
 
     impl Default for TestERC20Burnable {

examples/erc20/src/lib.rs

@@ -3,15 +3,18 @@ extern crate alloc;
 
 use alloc::string::String;
 
+// Import required by ERC20Burnable extension.
 use alloy_primitives::{Address, U256};
-use contracts::{
-    derive_erc20_burnable,
-    erc20::{extensions::Metadata, Error, ERC20},
-};
-use stylus_sdk::{
-    msg,
-    prelude::{entrypoint, external, sol_storage},
-};
+// Import Metadata extension.
+use contracts::erc20::extensions::Metadata;
+// Import ERC20 token and its Errors.
+use contracts::erc20::{Error, ERC20};
+// Import implementation of ERC20Burnable extension.
+use contracts::impl_erc20_burnable;
+// Import required by ERC20Burnable extension.
+use stylus_sdk::msg;
+// Stylus imports to build a smart contract.
+use stylus_sdk::prelude::{entrypoint, external, sol_storage};
 
 const DECIMALS: u8 = 10;
 
@@ -28,7 +31,9 @@ sol_storage! {
 #[external]
 #[inherit(ERC20, Metadata)]
 impl Token {
-    derive_erc20_burnable!();
+    // This macro implements ERC20Burnable functions -- `burn` and `burn_from`.
+    // Uses `erc20` Token's attribute.
+    impl_erc20_burnable!();
 
     pub fn constructor(&mut self, name: String, symbol: String) {
         self.metadata.constructor(name, symbol);