0(1) element: null
1(2) element: PyMatchStatement
2(3) element: PyAsPattern
3(4) refutable pattern: [42] | foo.bar
4(5,8) refutable pattern: [42]
5(6,8) refutable pattern: 42
6(7) matched pattern: 42
7(11) matched pattern: [42]
8(9) refutable pattern: foo.bar
9(10,15) READ ACCESS: foo
10(11) matched pattern: foo.bar
11(12) matched pattern: [42] | foo.bar
12(13) WRITE ACCESS: x
13(14) element: PyExpressionStatement
14(15) READ ACCESS: y
15(16) element: PyExpressionStatement
16(17) READ ACCESS: z
17() element: null