Python 3.6+ SETUP_ANNOTATION

[rocky]

Python 3.6+ SETUP_ANNOTATION is not handled. Here is code that will create such an opcode:

x: int

[dotjrich]

I've started noodling around with this one and wanted to talk about my strategy and see if it makes sense.

From what I can tell from my testing, it looks like we'll see SETUP_ANNOTATIONS as the first instruction if annotations are used anywhere:

        0       SETUP_ANNOTATIONS

When a variable has been annotated, we'll then see something along the lines of this:

        6       LOAD_NAME               1: int
        8       LOAD_NAME               2: __annotations__
        10      LOAD_CONST              1: 'x'

So, what I was planning on doing is set some kind of flag if we find SETUP_ANNOTATIONS. Then, if that flag is set, we'll take a peek at the top of the stack whenever we encounter LOAD_CONST and see if we find __annotations__. If we do, we'll process it as an annotation accordingly.

Does that sound like a viable strategy?

[zrax]

If you look a little more closely, it looks like what the code actually does is translate:

x: int

into

__annotations__['x'] = int

So the lazy solution would just be to ignore SETUP_ANNOTATIONS, and leave the code the compiler translated as-is... But the more advanced solution might be to look for subscript stores to __annotations__ and emit the appropriate annotation instead.

NOTE: This gets a little trickier with mixed annotation and assignment, since Python turns this into two statements:

x: int = 5

### Compiles to:
x = 5
__annotations__['x'] = int

[dotjrich]

Thank you for the pointers; this is very helpful! I'll see what I can come up with.