Meta-issue: Use Full Unification for Generic Inference?

Search Terms

unification generic inference

Suggestion

Today, TypeScript cannot retain or synthesize free type parameters during generic inference. This means code like this doesn't typecheck, when it should:

function identity<T>(arg: T) { return arg; }
function memoize<F extends (...args: unknown[]) => unknown>(fn: F): F { return fn; }
// memid: unknown => unknown
// desired: memid<T>(T) => T
const memid = memoize(identity);

Use Cases

Many functional programming patterns would greatly benefit from this.

The purpose of this issue is to gather use cases and examine the cost/benefit of using a different inference algorithm.

Examples

Haven't extensively researched these to validate that they require unification, but it's a start:

#9366
#3423
#25092
#26951 (design meeting notes with good examples)
#25826
#10247

Start by studying the generic inference example in the issue and reviewing the referenced issues #9366, #3423, #25092, #26951, #25826, and #10247. Gather validated use cases and assess the cost and benefit of changing the inference algorithm; done means producing a considered design direction rather than a contained code change.