Generic Higher order Function Confusion

[hmc-cs-mdrissi]

Why does set behave differently from lambda ls: set(ls) in the example below?

x = [[1, 2, 3]]
y = map(set, x)
reveal_type(y) # map[set[unknown]]

x = [[1, 2, 3]]
y = map(lambda ls: set(ls), x)
reveal_type(y) # map[set[int]]

This shows same behavior for both mypy and pyright and I'm confused why the two code blocks are handled differently.

[erictraut]

For reference, I answered this question in a related issue in the pyright issue tracker. microsoft/pyright#3208