Allow TypedDataUtils to be called unbound

Previously the functions exposed as `TypedDataUtils` could only be
called from the `TypedDataUtils` object. If they were called unbound,
they would throw errors because of the use of `this`.

They have all been updated to no longer rely upon `this`, so they now
work the same way regardless how they are bound when called.

They are still exported as the `TypedDataUtils` object, so this should
not change the API. This was done to simplify the code, specifically to
make it easier for functions outside of `TypedDataUtils` to reuse code
inside of `TypedDataUtils`.

Some types required adjustments, as type mistakes were brought to light
that TypeScript for some reason wasn't aware of when these were
declared as properties of the `TypedDataUtils` object. These were fixed
by adding two type assertions, making the `types` parameter to
`hashStruct` and `hashType` more strict, and by making the `typedData`
parameter to `eip712Hash` more strict. The type assertions (warranted
or not) preserve the types used previously. We can replace them later
with validation.

src/index.test.ts

@@ -1250,3 +1250,126 @@ it('signedTypeMessage V4 with recursive types', function () {
     '0xf2ec61e636ff7bb3ac8bc2a4cc2c8b8f635dd1b2ec8094c963128b358e79c85c5ca6dd637ed7e80f0436fe8fce39c0e5f2082c9517fe677cc2917dcd6c84ba881c',
   );
 });
+
+it('unbound sign typed data utility functions', function () {
+  const typedData = {
+    types: {
+      EIP712Domain: [
+        { name: 'name', type: 'string' },
+        { name: 'version', type: 'string' },
+        { name: 'chainId', type: 'uint256' },
+        { name: 'verifyingContract', type: 'address' },
+      ],
+      Person: [
+        { name: 'name', type: 'string' },
+        { name: 'mother', type: 'Person' },
+        { name: 'father', type: 'Person' },
+      ],
+    },
+    domain: {
+      name: 'Family Tree',
+      version: '1',
+      chainId: 1,
+      verifyingContract: '0xCcCCccccCCCCcCCCCCCcCcCccCcCCCcCcccccccC',
+    },
+    primaryType: 'Person' as const,
+    message: {
+      name: 'Jon',
+      mother: {
+        name: 'Lyanna',
+        father: {
+          name: 'Rickard',
+        },
+      },
+      father: {
+        name: 'Rhaegar',
+        father: {
+          name: 'Aeris II',
+        },
+      },
+    },
+  };
+
+  const { encodeData, encodeType, hashStruct, hashType, eip712Hash } =
+    sigUtil.TypedDataUtils;
+
+  expect(encodeType('Person', typedData.types)).toBe(
+    'Person(string name,Person mother,Person father)',
+  );
+
+  expect(ethUtil.bufferToHex(hashType('Person', typedData.types))).toBe(
+    '0x7c5c8e90cb92c8da53b893b24962513be98afcf1b57b00327ae4cc14e3a64116',
+  );
+
+  expect(
+    ethUtil.bufferToHex(
+      encodeData('Person', typedData.message.mother, typedData.types, 'V4'),
+    ),
+  ).toBe(
+    `0x${[
+      '7c5c8e90cb92c8da53b893b24962513be98afcf1b57b00327ae4cc14e3a64116',
+      'afe4142a2b3e7b0503b44951e6030e0e2c5000ef83c61857e2e6003e7aef8570',
+      '0000000000000000000000000000000000000000000000000000000000000000',
+      '88f14be0dd46a8ec608ccbff6d3923a8b4e95cdfc9648f0db6d92a99a264cb36',
+    ].join('')}`,
+  );
+  expect(
+    ethUtil.bufferToHex(
+      hashStruct('Person', typedData.message.mother, typedData.types, 'V4'),
+    ),
+  ).toBe('0x9ebcfbf94f349de50bcb1e3aa4f1eb38824457c99914fefda27dcf9f99f6178b');
+
+  expect(
+    ethUtil.bufferToHex(
+      encodeData('Person', typedData.message.father, typedData.types, 'V4'),
+    ),
+  ).toBe(
+    `0x${[
+      '7c5c8e90cb92c8da53b893b24962513be98afcf1b57b00327ae4cc14e3a64116',
+      'b2a7c7faba769181e578a391a6a6811a3e84080c6a3770a0bf8a856dfa79d333',
+      '0000000000000000000000000000000000000000000000000000000000000000',
+      '02cc7460f2c9ff107904cff671ec6fee57ba3dd7decf999fe9fe056f3fd4d56e',
+    ].join('')}`,
+  );
+  expect(
+    ethUtil.bufferToHex(
+      hashStruct('Person', typedData.message.father, typedData.types, 'V4'),
+    ),
+  ).toBe('0xb852e5abfeff916a30cb940c4e24c43cfb5aeb0fa8318bdb10dd2ed15c8c70d8');
+
+  expect(
+    ethUtil.bufferToHex(
+      encodeData(
+        typedData.primaryType,
+        typedData.message,
+        typedData.types,
+        'V4',
+      ),
+    ),
+  ).toBe(
+    `0x${[
+      '7c5c8e90cb92c8da53b893b24962513be98afcf1b57b00327ae4cc14e3a64116',
+      'e8d55aa98b6b411f04dbcf9b23f29247bb0e335a6bc5368220032fdcb9e5927f',
+      '9ebcfbf94f349de50bcb1e3aa4f1eb38824457c99914fefda27dcf9f99f6178b',
+      'b852e5abfeff916a30cb940c4e24c43cfb5aeb0fa8318bdb10dd2ed15c8c70d8',
+    ].join('')}`,
+  );
+  expect(
+    ethUtil.bufferToHex(
+      hashStruct(
+        typedData.primaryType,
+        typedData.message,
+        typedData.types,
+        'V4',
+      ),
+    ),
+  ).toBe('0xfdc7b6d35bbd81f7fa78708604f57569a10edff2ca329c8011373f0667821a45');
+  expect(
+    ethUtil.bufferToHex(
+      hashStruct('EIP712Domain', typedData.domain, typedData.types, 'V4'),
+    ),
+  ).toBe('0xfacb2c1888f63a780c84c216bd9a81b516fc501a19bae1fc81d82df590bbdc60');
+  expect(ethUtil.bufferToHex(eip712Hash(typedData, 'V4'))).toBe(
+    '0x807773b9faa9879d4971b43856c4d60c2da15c6f8c062bd9d33afefb756de19c',
+  );
+});