Parity Substrate

Solang works with Parity Substrate 3.0. Note that for recent Substrate versions, cross-contract calls as well as using address type as function argument or return values are not supported. We are currently working on fixing any regressions.

The Parity Substrate has the following differences to Ethereum Solidity:

  • The address type is 32 bytes, not 20 bytes. This is what Substrate calls an “account”

  • An address literal has to be specified using the address"5GBWmgdFAMqm8ZgAHGobqDqX6tjLxJhv53ygjNtaaAn3sjeZ" syntax

  • ABI encoding and decoding is done using the SCALE encoding

  • Constructors can be named. Constructors with no name will be called new in the generated metadata.

  • There is no ecrecover() builtin function, or any other function to recover or verify cryptographic signatures at runtime

  • Only functions called via rpc may return values; when calling a function in a transaction, the return values cannot be accessed

  • An assert(), require(), or revert() executes the wasm unreachable instruction. The reason code is lost

There is an solidity example which can be found in the examples directory. Write this to flipper.sol and run:

solang compile --target substrate flipper.sol

Now you should have a file called flipper.contract. The file contains both the ABI and contract wasm. It can be used directly in the Contracts UI, as if the contract was written in ink!.

Builtin Imports

Some builtin functionality is only available after importing. The following types can be imported via the special import file substrate.

import {Hash} from 'substrate';

Note that {Hash} can be omitted, renamed or imported via import object.

// Now Hash will be known as InkHash
import {Hash as InkHash} from 'substrate';

Note

The import file substrate is only available when compiling for the Substrate target.