[Python] tsg-parser fails to extract generic base class relations

Bắt đầu bằng cách tái hiện đầu ra v2.26.2 tsg-python cho class Bar(list[int]): pass, sau đó theo dõi cách parser xử lý nút Subscript khi xây dựng các base của lớp. Hoàn tất khi base generic tạo ra một cạnh bases và CodeQL nhận diện quan hệ Bar -> list[int], trong khi trường hợp không generic hiện có vẫn nguyên vẹn.

Working with typed base classes in Python (see #22291) I realised that the toolchain seems to drop generic base classes (e.g. list[int] in class Bar(list[int]):) at some point. That is, in the example code

class Foo(list): pass

class Bar(list[int]): pass

CodeQL knows the Foo -> list relation but not the Bar -> list[int] relation.

As far as I could trace it, the relation is already lost in the tsg-python parser. Using the v2.26.2 toolchain, the source code class Bar(list): pass produces the following tsg-python output (assignment nodes removed for brevity):

node 4
  _kind: "Name"
  _location: [0, 10, 0, 14]
  ctx: "load"
  variable: "list"
node 5
  _kind: "ClassExpr"
  _location: [0, 0, 0, 21]
  _location_end: [0, 16]
  inner_scope: [graph node 6]
  name: "Bar"
edge 5 -> 4
  bases: 0
node 6
  _kind: "Class"
  _location: [0, 0, 0, 21]
  _location_end: [0, 16]
  name: "Bar"
edge 6 -> 1
  body: 0

Now if the code is extended for a generic subscription as class Bar(list[int]): pass produces the following tsg-python output (assignment nodes removed for brevity):

node 4
  _kind: "Name"
  _location: [0, 10, 0, 14]
  ctx: "load"
  variable: "list"
node 5
  _kind: "Name"
  _location: [0, 15, 0, 18]
  ctx: "load"
  variable: "int"
node 6
  _kind: "Subscript"
  _location: [0, 10, 0, 19]
  ctx: "load"
  index: [graph node 5]
  value: [graph node 4]
node 7
  _kind: "ClassExpr"
  _location: [0, 0, 0, 26]
  _location_end: [0, 21]
  inner_scope: [graph node 8]
  name: "Bar"
node 8
  _kind: "Class"
  _location: [0, 0, 0, 26]
  _location_end: [0, 21]
  name: "Bar"
edge 8 -> 1
  body: 0

Notice that the type subscription is parsed (nodes 4, 5, 6) but the edge n -> m node for the bases: 0 relation is absent.