[mypyc] Add 'range' primitive type

[97littleleaf11]

Description

Closes mypyc/mypyc#770

Test Plan

def range_object() -> None:
    r = range(4, 12, 2)
    sum = 0
    for i in r:
        sum += I

This should generate a range object and a iterator when looping on it.

def range_in_loop() -> None:
    sum = 0
    for i in range(4, 12, 2):
        sum += I

This should maintain original specialized IR result.

[JukkaL]

Thanks for the PR! Looks good, just a few comments about tests.

[JukkaL]

There probably is an existing test case for range in a for loop, so this can be removed.

[97littleleaf11]

I cannot find the irbuild case and I'll keep this.

[JukkaL]

Can you change this to use a test_ function without a custom driver, as that's the "modern" way to write tests.

Test also that coercion to range works, for example something like this:

def f(r: range) -> None:
    pass

r: Any = range(...)
f(r)  # OK

r = 'x'
f(r)  # Should be a TypeError

ff: Any = f
ff(r)  # Again should be a TypeError; this uses the wrapper function since the callee has type Any

[97littleleaf11]

I got this error after adding function def f(r: range) -> None:

run-loops.test:460: error: Function "builtins.range" is not valid as a type
run-loops.test:460: note: Perhaps you need "Callable[...]" or a callback protocol?

[JukkaL]

You'll need to change the definition of range into a class in mypyc/test-data/fixtures/ir.py.

[97littleleaf11]

Two cases seem to work correctly.

[JukkaL]

LGTM