The XCM builder pattern lets you build xcms like so:
```rust
let xcm = Xcm::builder()
.withdraw_asset((Parent, 100u128).into())
.buy_execution((Parent, 1u128).into())
.deposit_asset(All.into(), AccountId32 { id: [0u8; 32], network: None }.into())
.build();
```
All the `.into()` become quite annoying to have to write.
I accepted `impl Into<T>` instead of `T` in the generated methods from
the macro.
Now the previous example can be simplified as follows:
```rust
let xcm = Xcm::builder()
.withdraw_asset((Parent, 100u128))
.buy_execution((Parent, 1u128))
.deposit_asset(All, [0u8; 32])
.build();
```
---------
Co-authored-by: Bastian Köcher <git@kchr.de>
Co-authored-by: command-bot <>
Co-authored-by: Adrian Catangiu <adrian@parity.io>
Adding on top of the new builder pattern for creating XCM programs, I'm
adding some more APIs:
```rust
let paying_fees: Xcm<()> = Xcm::builder() // Only allow paying for fees
.withdraw_asset() // First instruction has to load the holding register
.buy_execution() // Second instruction has to be `buy_execution`
.build();
let paying_fees_invalid: Xcm<()> = Xcm::builder()
.withdraw_asset()
.build(); // Invalid, need to pay for fees
let not_paying_fees: Xcm<()> = Xcm::builder_unpaid()
.unpaid_execution() // Needed
.withdraw_asset()
.deposit_asset()
.build();
let all_goes: Xcm<()> = Xcm::builder_unsafe() // You can do anything
.withdraw_asset()
.deposit_asset()
.build();
```
The invalid bits are because the methods don't even exist on the types
that you'd want to call them on.
---------
Co-authored-by: command-bot <>
Added a proc macro to be able to write XCMs using the builder pattern.
This means we go from having to do this:
```rust
let message: Xcm<()> = Xcm(vec![
WithdrawAsset(assets),
BuyExecution { fees: asset, weight_limit: Unlimited },
DepositAsset { assets, beneficiary },
]);
```
to this:
```rust
let message: Xcm<()> = Xcm::builder()
.withdraw_asset(assets)
.buy_execution(asset, Unlimited),
.deposit_asset(assets, beneficiary)
.build();
```
---------
Co-authored-by: Keith Yeung <kungfukeith11@gmail.com>
Co-authored-by: command-bot <>
Francisco Aguirre