Summary

This PR adds support for unpacking tuple expression in an assignment statement where the target expression can be a tuple or a list (the allowed sequence targets).

The implementation introduces a new infer_assignment_target which can then be used for other targets like the ones in for loops as well. This delegates it to the infer_definition. The final implementation uses a recursive function that visits the target expression in source order and compares the variable node that corresponds to the definition. At the same time, it keeps track of where it is on the assignment value type.

The logic also accounts for the number of elements on both sides such that it matches even if there's a gap in between. For example, if there's a starred expression like (a, *b, c) = (1, 2, 3), then the type of a will be Literal[1] and the type of b will be Literal[2].

There are a couple of follow-ups that can be done:

• Use this logic for other target positions like for loop
• Add diagnostics for mis-match length between LHS and RHS

Test Plan

Add various test cases using the new markdown test framework.
Validate that existing test cases pass.