test: assets precompile integration test

CHANGELOG.md

@@ -11,6 +11,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Add `#[ink::contract_ref]` attribute - [#2648](https://github.com/use-ink/ink/pull/2648)
 - Add `ink_revive_types` (and remove `pallet-revive` dependency from `ink_e2e`) - [#2657](https://github.com/use-ink/ink/pull/2657)
 - non-allocating Solidity ABI encoder - [#2655](https://github.com/use-ink/ink/pull/2655)
+- Add `ink_precompiles` crate with ERC-20 assets precompile interface - [#2686](https://github.com/use-ink/ink/pull/2686)
 
 ### Changed
 - Marks the `pallet-revive` host function `account_id` stable - [#2578](https://github.com/use-ink/ink/pull/2578)

Cargo.toml

@@ -11,6 +11,7 @@ members = [
     "crates/ink/ir",
     "crates/ink/macro",
     "crates/metadata",
+    "crates/precompiles",
     "crates/revive-types",
     "crates/prelude",
     "crates/primitives",
@@ -115,6 +116,7 @@ ink_env = { version = "=6.0.0-alpha.4", path = "crates/env", default-features =
 ink_ir = { version = "=6.0.0-alpha.4", path = "crates/ink/ir", default-features = false }
 ink_macro = { version = "=6.0.0-alpha.4", path = "crates/ink/macro", default-features = false }
 ink_metadata = { version = "=6.0.0-alpha.4", path = "crates/metadata", default-features = false }
+ink_precompiles = { version = "=6.0.0-alpha.4", path = "crates/precompiles", default-features = false }
 ink_prelude = { version = "=6.0.0-alpha.4", path = "crates/prelude", default-features = false }
 ink_primitives = { version = "=6.0.0-alpha.4", path = "crates/primitives", default-features = false }
 ink_revive_types = {  version = "=6.0.0-alpha.4", path = "crates/revive-types", default-features = false }

crates/e2e/src/contract_results.rs

@@ -259,6 +259,31 @@ impl<E: Environment, V, EventLog, Abi> CallResult<E, V, EventLog, Abi> {
     pub fn return_data(&self) -> &[u8] {
         &self.dry_run.exec_return_value().data
     }
+
+    /// Returns the error from nested contract calls (e.g., precompile errors)
+    /// if available in the trace, otherwise returns the raw error data.
+    pub fn extract_error(&self) -> Option<String> {
+        if !self.dry_run.did_revert() {
+            return None;
+        }
+
+        // Check trace for error information
+        if let Some(trace) = &self.trace {
+            // // Check nested calls first (more specific errors)
+            for call in &trace.calls {
+                if let Some(error) = &call.error {
+                    return Some(error.clone());
+                }
+            }
+
+            // Then check top-level error
+            if let Some(error) = &trace.error {
+                return Some(error.clone());
+            }
+        }
+        // Fallback to raw data
+        Some(format!("{:?}", self.return_data()))
+    }
 }
 
 // TODO(#xxx) Improve the `Debug` implementation.

crates/ink/macro/src/contract_ref.rs

@@ -68,7 +68,7 @@ pub fn analyze_or_err(
         #trait_def_impl
 
         // Type alias for contract ref.
-        type #contract_ref_name =
+        pub type #contract_ref_name =
             <<::ink::reflect::TraitDefinitionRegistry<#env> as #trait_name>
                     ::__ink_TraitInfo as ::ink::codegen::TraitCallForwarder>::Forwarder<#abi_ty>;
     ))

crates/precompiles/Cargo.toml

@@ -0,0 +1,21 @@
+[package]
+name = "ink_precompiles"
+version.workspace = true
+authors = ["Use Ink <[email protected]>"]
+edition.workspace = true
+license.workspace = true
+description = "[ink!] Precompile interfaces for pallet-revive smart contracts."
+repository.workspace = true
+homepage.workspace = true
+keywords.workspace = true
+categories.workspace = true
+
+[dependencies]
+ink = { workspace = true, default-features = false }
+
+[features]
+default = ["std"]
+std = [
+    "ink/std",
+]
+

crates/precompiles/src/erc20.rs

@@ -0,0 +1,192 @@
+// Copyright (C) Use Ink (UK) Ltd.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//! ERC-20 precompile interface for pallet-assets.
+//!
+//! This module provides the standard ERC-20 token interface for interacting with
+//! assets managed by `pallet-assets` through the precompile mechanism.
+//!
+//! # References
+//!
+//! - [Polkadot SDK Assets Precompile](https://github.com/paritytech/polkadot-sdk/blob/master/substrate/frame/assets/src/precompiles.rs)
+//! - [ERC-20 Token Standard](https://eips.ethereum.org/EIPS/eip-20)
+
+use ink::{
+    Address,
+    U256,
+};
+
+/// ERC-20 Assets precompile index.
+pub const PRECOMPILE_INDEX: u16 = 0x0120;
+
+/// Type alias for asset IDs.
+pub type AssetId = u32;
+
+/// Defines the ERC-20 interface of the Asset Hub precompile.
+#[ink::contract_ref(abi = "sol")]
+pub trait Erc20 {
+    /// Returns the total supply of tokens.
+    ///
+    /// # Solidity Signature
+    ///
+    /// ```solidity
+    /// function totalSupply() external view returns (uint256);
+    /// ```
+    #[ink(message)]
+    #[allow(non_snake_case)]
+    fn totalSupply(&self) -> U256;
+
+    /// Returns the balance of an account.
+    ///
+    /// # Arguments
+    /// * `account` - The address to query the balance of
+    ///
+    /// # Solidity Signature
+    ///
+    /// ```solidity
+    /// function balanceOf(address account) external view returns (uint256);
+    /// ```
+    #[ink(message)]
+    #[allow(non_snake_case)]
+    fn balanceOf(&self, account: Address) -> U256;
+
+    /// Transfers tokens to another account.
+    ///
+    /// # Arguments
+    /// * `to` - The recipient address
+    /// * `value` - The amount of tokens to transfer
+    ///
+    /// # Returns
+    ///
+    /// Returns `true` if the transfer was successful.
+    ///
+    /// # Solidity Signature
+    ///
+    /// ```solidity
+    /// function transfer(address to, uint256 value) external returns (bool);
+    /// ```
+    #[ink(message)]
+    fn transfer(&mut self, to: Address, value: U256) -> bool;
+
+    /// Returns the allowance for a spender on behalf of an owner.
+    ///
+    /// This shows how many tokens `spender` is allowed to spend on behalf of `owner`.
+    ///
+    /// # Arguments
+    /// * `owner` - The token owner's address
+    /// * `spender` - The spender's address
+    ///
+    /// # Solidity Signature
+    ///
+    /// ```solidity
+    /// function allowance(address owner, address spender) external view returns (uint256);
+    /// ```
+    #[ink(message)]
+    fn allowance(&self, owner: Address, spender: Address) -> U256;
+
+    /// Approves a spender to spend tokens on behalf of the caller.
+    ///
+    /// # Arguments
+    /// * `spender` - The address authorized to spend tokens
+    /// * `value` - The maximum amount the spender can spend
+    ///
+    /// # Returns
+    ///
+    /// Returns `true` if the approval was successful.
+    ///
+    /// # Solidity Signature
+    ///
+    /// ```solidity
+    /// function approve(address spender, uint256 value) external returns (bool);
+    /// ```
+    #[ink(message)]
+    fn approve(&mut self, spender: Address, value: U256) -> bool;
+
+    /// Transfers tokens from one account to another using allowance.
+    ///
+    /// The caller must have sufficient allowance from the `from` account.
+    ///
+    /// # Arguments
+    /// * `from` - The address to transfer tokens from
+    /// * `to` - The recipient address
+    /// * `value` - The amount of tokens to transfer
+    ///
+    /// # Returns
+    ///
+    /// Returns `true` if the transfer was successful.
+    ///
+    /// # Solidity Signature
+    ///
+    /// ```solidity
+    /// function transferFrom(address from, address to, uint256 value) external returns (bool);
+    /// ```
+    #[ink(message)]
+    #[allow(non_snake_case)]
+    fn transferFrom(&mut self, from: Address, to: Address, value: U256) -> bool;
+}
+
+/// Creates a new ERC-20 precompile reference for the given asset ID.
+///
+/// # Arguments
+/// * `asset_id` - The ID of the asset to interact with
+///
+/// # Returns
+///
+/// Returns an `Erc20Ref` that can be used to call precompile methods.
+///
+/// # Example
+///
+/// ```rust,ignore
+/// use ink_precompiles::erc20::erc20;
+///
+/// let asset_id = 1;
+/// let erc20_ref = erc20(asset_id);
+/// let balance = erc20_ref.balanceOf(account);
+/// ```
+pub fn erc20(asset_id: AssetId) -> Erc20Ref {
+    let address = crate::prefixed_address(PRECOMPILE_INDEX, asset_id);
+    address.into()
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn erc20_precompile_address_format() {
+        // ERC20 Assets precompile for asset ID 1 should be at the correct address
+        let expected = [
+            0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+            0x00, 0x00, 0x00, 0x01, 0x20, 0x00, 0x00,
+        ];
+
+        let address = crate::prefixed_address(PRECOMPILE_INDEX, 1);
+        let address_bytes: [u8; 20] = address.into();
+
+        assert_eq!(address_bytes, expected);
+    }
+
+    #[test]
+    fn erc20_precompile_address_for_multiple_assets() {
+        // Test asset ID 42
+        let address_42 = crate::prefixed_address(PRECOMPILE_INDEX, 42);
+        let bytes_42: [u8; 20] = address_42.into();
+
+        // First 4 bytes should be asset ID (42 = 0x0000002a)
+        assert_eq!(&bytes_42[0..4], &[0x00, 0x00, 0x00, 0x2a]);
+
+        // Bytes 16-19 should be precompile index (0x0120)
+        assert_eq!(&bytes_42[16..20], &[0x01, 0x20, 0x00, 0x00]);
+    }
+}