support multi-step bidirectional type inference #1211
Description
Summary
def f1() -> list[object]:
return [1, 2, 3] # lovely, bidirectional type inference uses the return type to infer `list[object]`
def f2() -> list[object]:
result = [1, 2, 3]
return result # error: bi-directional type inference does not look ahead, so the inferred type is `list[int]`note that there are two issues preventing the actual error from surfacing:
- return position is not taken into account for constraint solving
[1, 2, 3]is inferred aslist[Unknown | int], which is assignable tolist[object]