fix(func): await Promises returned from async generators

[Refzlund]

Summary

Fixes #17 - Returning a Promise from an async generator in func wraps the Promise instead of awaiting it.

Problem

When using func with an async generator (async function*) and returning a Promise at the end (e.g., from another function call), the returned value became Result<Promise<T>> instead of Result<T>. The Promise was not awaited before being wrapped in the Result.

const inner = func(async () => {
  return { id: 1 }
})

const outer = func(async function*() {
  return inner() // Returns Promise<Result<{ id: 1 }>>
})

const result = await outer()
// Before fix: Result.Ok with value Promise<Result<{ id: 1 }>> ❌
// After fix: Result.Ok with value { id: 1 } ✅

Root Cause

In the handleIteration function within Result.func, when an async generator completed (iteration.done === true), the code checked if the value was a Result instance. When iteration.value was a Promise, it passed the instanceof Result check as false, so it got wrapped in Result.ok(Promise) instead of being awaited first.

Solution

Modified the async generator iteration path to check if the final value is a Result.Ok containing a Promise. When detected:

1. Await the Promise
2. If the awaited value is itself a Result, return it directly
3. Otherwise, wrap the awaited value in Result.ok()
4. Handle any errors during Promise resolution with toThrownError

Changes

• src/result.ts: Added Promise detection and awaiting logic in the async generator completion handler
• tests/issues/#17-async-generator-promise-wrap.test.ts: Minimal reproduction test for issue fix: func(async) infinite recursion in function execution #8
• tests/promises.test.ts: Comprehensive test suite covering Promise handling in async generators

Test Results

• ✅ All 312 tests pass
• ✅ TypeScript type checking passes
• ✅ Linting passes

Workaround (no longer needed)

Previously, users had to use yield* await instead of directly returning the Promise:

// Old workaround (still works, but no longer required)
const processData = func(async function*() {
  const data = yield* await fetchData()
  return data
})

// Now this works correctly too
const processData = func(async function*() {
  return fetchData() // Promise is now properly awaited
})

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Latest commit: f76713a

The changes in this PR will be included in the next version bump.

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