createEventDispatcher definitions are not merged

[dummdidumm]

It appears that only the last createEventDispatcher produces the type for the listener, they are not merged.

Example:

// Component Foo
const dispatchFoo = createEventDispatcher<{foo: string; bar: boolean}>();
const dispatchBar = createEventDispatcher<{bar: string; baz: string}>();

// Component Bar
// e is CustomEvent<any>
on:foo="{(e) => handleFoo(e.detail.bar)}"
// e is CustomEvent<{baz: string}>
on:bar="{(e) => handleBar(e.detail.bar)}"

The typescript compiler catches this as expected.

Changing the order produces different results.

if the createEventDispatcher order changes, then the typescript compiler does not catch the error.

// Component Foo
const dispatchBar = createEventDispatcher<{bar: string; baz: string}>();
const dispatchFoo = createEventDispatcher<{foo: string; bar: boolean}>();

// Component Bar
// e is CustomEvent<{bar: boolean}>
on:foo="{(e) => handleFoo(e.detail.bar)}"
// e is CustomEvent<any>
on:bar="{(e) => handleBar(e.detail.bar)}"

The typescript compiler does not catch the error since the type is now CustomEvent<any>.

Originally posted by @linuxuser586 in #424 (comment)