Add an ABC for the visitors passed to pyc.visit().

To make a subsequent change clearer.

PiperOrigin-RevId: 652453548

pytype/blocks/process_blocks.py

@@ -25,7 +25,7 @@ def _is_function_def(fn_code):
   return True
 
 
-class CollectAnnotationTargetsVisitor:
+class CollectAnnotationTargetsVisitor(pyc.CodeVisitor):
   """Collect opcodes that might have annotations attached."""
 
   def __init__(self):
@@ -68,7 +68,7 @@ def visit_code(self, code):
     return code
 
 
-class FunctionDefVisitor:
+class FunctionDefVisitor(pyc.CodeVisitor):
   """Add metadata to function definition opcodes."""
 
   def __init__(self, param_annotations):

pytype/constant_folding.py

@@ -265,7 +265,7 @@ def resolve(self, op):
     return f
 
 
-class _FoldConstants:
+class _FoldConstants(pyc.CodeVisitor):
   """Fold constant literals in pyc code."""
 
   def visit_code(self, code):

pytype/pyc/pyc.py

@@ -1,5 +1,6 @@
 """Functions for generating, reading and parsing pyc."""
 
+import abc
 import copy
 
 from pycnite import pyc
@@ -11,6 +12,14 @@
 CompileError = compiler.CompileError
 
 
+# The abstract base class for a code visitor passed to pyc.visit.
+class CodeVisitor(abc.ABC):
+
+  @abc.abstractmethod
+  def visit_code(self, code):
+    ...
+
+
 def parse_pyc_string(data):
   """Parse pyc data from a string.
 
@@ -23,7 +32,7 @@ def parse_pyc_string(data):
   return pyc.loads(data)
 
 
-class AdjustFilename:
+class AdjustFilename(CodeVisitor):
   """Visitor for changing co_filename in a code object."""
 
   def __init__(self, filename):
@@ -71,7 +80,7 @@ def compile_src(src, filename, python_version, python_exe, mode="exec"):
 _VISIT_CACHE = {}
 
 
-def visit(c, visitor):
+def visit(c, visitor: CodeVisitor):
   """Recursively process constants in a pyc using a visitor."""
   if hasattr(c, "co_consts"):
     # This is a CodeType object (because it has co_consts). Visit co_consts,

pytype/vm_utils.py

@@ -21,6 +21,7 @@
 from pytype.errors import error_types
 from pytype.overlays import metaclass
 from pytype.pyc import opcodes
+from pytype.pyc import pyc
 from pytype.pytd import mro
 from pytype.pytd import pytd
 from pytype.pytd import slots
@@ -72,7 +73,7 @@ def __repr__(self):
     return f"Block({self.type}: {self.op_index} level={self.level})"
 
 
-class FindIgnoredTypeComments:
+class FindIgnoredTypeComments(pyc.CodeVisitor):
   """A visitor that finds type comments that will be ignored."""
 
   def __init__(self, type_comments):
@@ -82,7 +83,6 @@ def __init__(self, type_comments):
     self._ignored_type_lines = set(type_comments)
 
   def visit_code(self, code):
-    """Interface for pyc.visit."""
     for op in code.code_iter:
       # Make sure we have attached the type comment to an opcode.
       if isinstance(op, blocks.STORE_OPCODES):