Add libcst-dfa dependency, remove old code that was moved there

pyproject.toml

@@ -10,6 +10,7 @@ readme = "README.md"
 requires-python = ">=3.14"
 dependencies = [
     "libcst>=1.8.6",
+    "libcst-dfa>=0.0.1",
     "libcst-mypy>=0.1.0",
     "mypy>=1.19.1",
 ]

src/styx_compiler/core.py

@@ -12,12 +12,12 @@
 import libcst.matchers as m
 import mypy.api
 from libcst import CSTNode, FlattenSentinel, FunctionDef, Module, RemovalSentinel
+from libcst_dfa.live_variables import LiveVariablesProvider
 from libcst_mypy import MypyTypeInferenceProvider
 from libcst_mypy.utils import MypyType
 
 from styx_compiler.comprehension_expander import ComprehensionExpander
 from styx_compiler.config import N_PARTITIONS
-from styx_compiler.live_variables import LiveVariablesProvider
 from styx_compiler.processor import FunctionProcessor
 from styx_compiler.transformers import (
     EntityTypeReplacer,

src/styx_compiler/liveness.py

@@ -8,6 +8,7 @@
 
 import libcst as cst
 from libcst import matchers as m
+from libcst_dfa.data_flow import ImmutableSet
 
 
 class LivenessHelper:
@@ -22,16 +23,16 @@ def simple_name(v) -> str:
             return str(v.name).split(".")[-1]
         return str(v).split(".")[-1] if "." in str(v) else str(v)
 
-    def _live_set(self, node: cst.CSTNode | None, kind: str) -> frozenset | None:
+    def _live_set(self, node: cst.CSTNode | None, kind: str) -> ImmutableSet | None:
         if not self.live_vars or node is None:
             return None
         data = self.live_vars.get(node)
         if data is None:
             return None
         val = data[0] if kind == "in" else data[1]
-        return val if isinstance(val, frozenset) else None
+        return val if isinstance(val, ImmutableSet) else None
 
-    def live_out(self, stmt: cst.CSTNode) -> frozenset | None:
+    def live_out(self, stmt: cst.CSTNode) -> ImmutableSet | None:
         """Live-out set for a statement, or None if no liveness data."""
         if isinstance(stmt, cst.SimpleStatementLine) and stmt.body:
             element = stmt.body[0]