O.Merge with nested objects should compute.

[gautelo]

🐞 Bug Report

Describe the bug

When you merge two nested objects the MergeDeepObject type is left in the output type for nested object properties.

Reproduce the bug

declare type Source = {
	nested: {
		a: number,
	}
}

declare type Override = {
	nested: {
		b: number,
	}
}

declare type Merged = O.Merge<Source, Override, 'deep'>;
// expected =>
// type Merged = {
// 	nested: {
// 		 a: number;
// 		 b: number;
// 	};
// }

// actual =>
// type Merged = {
// 	nested: MergeDeepObject<{
// 		 a: number;
// 	}, {
// 		 b: number;
// 	}, BuiltIn, undefined, never>;
// }

Expected behavior

See expected output in ts above.

Possible Solution

Doing an A.Compute<> on the type defind by MergeDeepObject seem to fix it.

Additional context

I'm unsure about the ramifications of doing Computes inside low level library types in this way. There might be a performance reason that says you should only call Compute in app code and not inside the library or something like that.

Frankly I'm trying to write a similar type to the ts-toolbelt 'deep' mode capable types and would like to know what is and is not a good idea. ;) So even if you decline this bug report, I'd appreciate an explanation of why this is bad, if it is indeed a bad suggestion.

PS: ts-toolbelt is very cool, so thanks for making it! :) Been learning a lot by looking at the implementation.