refactor(experimental): support more scalar values in getDiscriminate…

…dUnionCodec (#2395)

This PR changes the custom values supported by `getDiscriminatedUnionCodec` from:

```ts
type DiscriminatorValue = number | string | symbol;
```

to:

```ts
type DiscriminatorValue = bigint | boolean | number | string | null | undefined;
```

Note that:
- We are dropping the `symbol` type since TypeScript doesn't make any distinctions between different symbols (i.e. `Symbol('A') | Symbol('B')` is typed as `symbol | symbol`).
- These values are now consistent with the new `getLiteralUnionCodec`.

packages/codecs-data-structures/README.md

@@ -339,7 +339,7 @@ messageCodec.encode({ message: 'Write', fields: ['Hi'] });
 messageCodec.encode({ message: 'Move', x: 5, y: 6 });
 ```
 
-Note that, the discriminator value of a variant may also be a `number`, `symbol` or a JavaScript `enum`. For instance, the following is also valid:
+Note that, the discriminator value of a variant may be any scalar value — such as `number`, `bigint`, `boolean`, a JavaScript `enum`, etc. For instance, the following is also valid:
 
 ```ts
 enum Message {

packages/codecs-data-structures/src/__tests__/discriminated-union-test.ts

@@ -159,6 +159,15 @@ describe('getDiscriminatedUnionCodec', () => {
         expect(codec.read(b('002a'), 0)).toStrictEqual([{ __kind: 1, one: 42 }, 2]);
     });
 
+    it('encodes discriminated unions with boolean discriminator values', () => {
+        const codec = discriminatedUnion([
+            [true, struct([['truth', u8()]])],
+            [false, struct([['lie', u32()]])],
+        ]);
+        expect(codec.encode({ __kind: true, truth: 42 })).toStrictEqual(b('002a'));
+        expect(codec.read(b('002a'), 0)).toStrictEqual([{ __kind: true, truth: 42 }, 2]);
+    });
+
     it('encodes discriminated unions with enum discriminator values', () => {
         enum Event {
             Click,

packages/codecs-data-structures/src/discriminated-union.ts

@@ -90,7 +90,7 @@ export type DiscriminatedUnionCodecConfig<
     size?: TDiscriminatorSize;
 };
 
-type DiscriminatorValue = number | string | symbol;
+type DiscriminatorValue = bigint | boolean | number | string | null | undefined;
 type Variants<T> = readonly (readonly [DiscriminatorValue, T])[];
 type ArrayIndices<T extends readonly unknown[]> = Exclude<Partial<T>['length'], T['length']> & number;
 

packages/errors/src/context.ts

@@ -283,8 +283,8 @@ export type SolanaErrorContext = DefaultUnspecifiedErrorContextToUndefined<
             expected: number;
         };
         [SOLANA_ERROR__CODECS__INVALID_DISCRIMINATED_UNION_VARIANT]: {
-            value: number | string | symbol;
-            variants: (number | string | symbol)[];
+            value: bigint | boolean | number | string | null | undefined;
+            variants: readonly (bigint | boolean | number | string | null | undefined)[];
         };
         [SOLANA_ERROR__CODECS__INVALID_ENUM_VARIANT]: {
             maxRange: number;