Annotated assignment in a `match` block does not generate `SETUP_ANNOTATIONS`

[martindemello]

Bug report

Compiling the following code:

match 0:
    case 0:
        x: int = 1

generates

  1           0 LOAD_CONST               0 (0)

  2           2 LOAD_CONST               0 (0)
              4 COMPARE_OP               2 (==)
              6 POP_JUMP_IF_FALSE       12 (to 24)

  3           8 LOAD_CONST               1 (1)
             10 STORE_NAME               0 (x)
             12 LOAD_NAME                1 (int)
             14 LOAD_NAME                2 (__annotations__)
             16 LOAD_CONST               2 ('x')
             18 STORE_SUBSCR
             20 LOAD_CONST               3 (None)
             22 RETURN_VALUE

  2     >>   24 LOAD_CONST               3 (None)
             26 RETURN_VALUE

There is no SETUP_ANNOTATIONS opcode generated despite the __annotations__ access later on. (Found via google/pytype#1435 - for some reason this does not generate a runtime error, but it does cause issues for tools like pytype.)

Your environment

cpython 3.10

Linked PRs

• gh-105164: Detect annotations inside match blocks #105177
• [3.12] gh-105164: Detect annotations inside match blocks (GH-105177) #105313
• [3.11] gh-105164: Detect annotations inside match blocks (GH-105177). #105314

[yilei]

FWIW, it's a runtime error when the module is imported, not run as main:

$ cat lib.py
match 0:
    case 0:
        x: int = 1

$ cat main.py
import lib

$ python main.py
Traceback (most recent call last):
  File "main.py", line 1, in <module>
    import lib
  File "lib.py", line 3, in <module>
    x: int = 1
NameError: name '__annotations__' is not defined

[brandtbucher]

I think find_ann in compile.c needs to be taught about Match_kind.

Looks like @JelleZijlstra picked this up already. Feel free to ping me for review!