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