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## `eip712HashType`

### Signature

```solidity
function eip712HashType(string calldata typeNameOrDefinition) external pure returns (bytes32 typeHash);
function eip712HashType(string calldata bindingsPath, string calldata typeName) external pure returns (bytes32 typeHash);
```

### Description

Generates the hash of the canonical [EIP-712](https://eips.ethereum.org/EIPS/eip-712) type representation, i.e. `keccak256(encodeType(...))`.

The input can be either:

1. A type definition string, such as `Foo(Bar bar)Bar(uint256 baz)`. The cheatcode canonicalizes the input, so extra whitespace or a wrong order of nested definitions is corrected automatically.
2. A type name, such as `Transaction`. This requires bindings previously generated with `forge bind-json`; they are read from the path configured under `[bind_json]` in `foundry.toml` (default `utils/JsonBindings.sol`), or from an explicit `bindingsPath` with the second overload.

Use it to keep on-chain `TYPEHASH` constants honest instead of hand-writing the encoded type string.

### Parameters

| Parameter              | Type     | Description                                                |
|------------------------|----------|------------------------------------------------------------|
| `typeNameOrDefinition` | `string` | A type name (requires bindings) or a full type definition  |
| `bindingsPath`         | `string` | Path to the `forge bind-json` output file                  |
| `typeName`             | `string` | The name of the type in the bindings                       |

### Returns

| Type      | Description                                  |
|-----------|----------------------------------------------|
| `bytes32` | `keccak256` of the canonical type definition |

### Examples

```solidity [test/Eip712HashType.t.sol]
bytes32 constant PERMIT_TYPEHASH = keccak256(
    "Permit(address owner,address spender,uint256 value,uint256 nonce,uint256 deadline)"
);

function testEip712HashType() public view {
    bytes32 typeHash = vm.eip712HashType(
        "Permit(address owner, address spender, uint256 value, uint256 nonce, uint256 deadline)"
    );
    assertEq(typeHash, PERMIT_TYPEHASH);
}
```

### Related Cheatcodes

* [`eip712HashStruct`](/reference/cheatcodes/eip712-hash-struct) - Hash a struct value per EIP-712
* [`eip712HashTypedData`](/reference/cheatcodes/eip712-hash-typed-data) - Compute a full EIP-712 digest from JSON