check the type like Python?

[ThreadSanitizer]

For example:

>>> x = 123
>>> type(x) is int
True
>>> type(x) is str
False
>>>

How to do this in Starlark?

[stepancheg]

In starlark spec starlark, the way to do it is:

type(x) == type(1)

in starlark-rust we have isinstance:

isinstance(x, int)

which I thing might be helpful addition to starlark spec, some basic form, i.e. mandate isinstance should work for builtin constructors like int or list.

[brandjon]

Any kind of symbolic type check raises questions about what exactly is a type, and what the type hierarchy is. Off the top of my head:

• Would isinstance() work on bazel providers and their instances?
• If you had a type()-style function that returned a type object, could that result be used to construct an instance of the type?