Add some very preliminary 3.10 opcode support.

Generated by following the mostly automated steps at the beginning of
https://github.com/google/pytype/blob/master/docs/developers/python_version_upgrades.md.
With this, we actually get useful test results rather than a bunch of
key errors for missing Python 3.10 magic numbers.

For #1022.

pytype/pyc/generate_opcode_diffs.py

@@ -17,7 +17,8 @@
 * "OPCODE MAPPING DIFF" is the content of a dictionary of opcode changes. Just
   copy the python_{major}_{minor}_mapping definition in pyc/opcodes.py for the
   previous version, change the version numbers, and replace the diff - it'll be
-  obvious where it goes.
+  obvious where it goes. Then add the new mapping to the mapping dict in the
+  top-level dis function in the same module.
 * "OPCODE STUB IMPLEMENTATIONS" are new methods that should be added to vm.py.
 """
 

pytype/pyc/magic.py

@@ -116,6 +116,18 @@
     3423: (3, 9),  # a2
     3424: (3, 9),  # a2
     3425: (3, 9),  # a2
+
+    # Python 3.10
+    3430: (3, 10),  # a1
+    3431: (3, 10),  # a1
+    3432: (3, 10),  # a2
+    3433: (3, 10),  # a2
+    3434: (3, 10),  # a6
+    3435: (3, 10),  # a7
+    3436: (3, 10),  # b1
+    3437: (3, 10),  # b1
+    3438: (3, 10),  # b1
+    3439: (3, 10),  # b1
 }
 
 

pytype/pyc/opcodes.py

@@ -151,6 +151,14 @@ def has_arg(cls):
     return True
 
 
+class LOAD_FOLDED_CONST(OpcodeWithArg):  # A fake opcode used internally
+  FLAGS = HAS_ARGUMENT
+  __slots__ = ()
+
+  def __str__(self):
+    return self.basic_str() + " " + str(self.arg.value)
+
+
 class POP_TOP(Opcode):
   __slots__ = ()
 
@@ -797,12 +805,39 @@ class DICT_UPDATE(OpcodeWithArg):
   __slots__ = ()
 
 
-class LOAD_FOLDED_CONST(OpcodeWithArg):  # A fake opcode used internally
+class GET_LEN(Opcode):
+  __slots__ = ()
+
+
+class MATCH_MAPPING(Opcode):
+  __slots__ = ()
+
+
+class MATCH_SEQUENCE(Opcode):
+  __slots__ = ()
+
+
+class MATCH_KEYS(Opcode):
+  __slots__ = ()
+
+
+class COPY_DICT_WITHOUT_KEYS(Opcode):
+  __slots__ = ()
+
+
+class ROT_N(OpcodeWithArg):
   FLAGS = HAS_ARGUMENT
   __slots__ = ()
 
-  def __str__(self):
-    return self.basic_str() + " " + str(self.arg.value)
+
+class GEN_START(OpcodeWithArg):
+  FLAGS = HAS_ARGUMENT
+  __slots__ = ()
+
+
+class MATCH_CLASS(OpcodeWithArg):
+  FLAGS = HAS_ARGUMENT
+  __slots__ = ()
 
 
 def _overlay_mapping(mapping, new_entries):
@@ -974,6 +1009,17 @@ def _overlay_mapping(mapping, new_entries):
     165: DICT_UPDATE,
 })
 
+python_3_10_mapping = _overlay_mapping(python_3_9_mapping, {
+    30: GET_LEN,
+    31: MATCH_MAPPING,
+    32: MATCH_SEQUENCE,
+    33: MATCH_KEYS,
+    34: COPY_DICT_WITHOUT_KEYS,
+    99: ROT_N,
+    129: GEN_START,
+    152: MATCH_CLASS,
+})
+
 
 class _LineNumberTableParser:
   """State machine for decoding a Python line number array."""
@@ -1113,6 +1159,7 @@ def dis(data, python_version, *args, **kwargs):
       (3, 7): python_3_7_mapping,
       (3, 8): python_3_8_mapping,
       (3, 9): python_3_9_mapping,
+      (3, 10): python_3_10_mapping,
   }[(major, minor)]
   return _dis(data, mapping, *args, **kwargs)
 

pytype/vm.py

@@ -3766,3 +3766,37 @@ def byte_LOAD_ASSERTION_ERROR(self, state, op):
     del op  # unused
     assertion_error = self.ctx.convert.name_to_value("builtins.AssertionError")
     return state.push(assertion_error.to_variable(state.node))
+
+  # Stub implementations for opcodes new in Python 3.10.
+
+  def byte_GET_LEN(self, state, op):
+    del op
+    return state
+
+  def byte_MATCH_MAPPING(self, state, op):
+    del op
+    return state
+
+  def byte_MATCH_SEQUENCE(self, state, op):
+    del op
+    return state
+
+  def byte_MATCH_KEYS(self, state, op):
+    del op
+    return state
+
+  def byte_COPY_DICT_WITHOUT_KEYS(self, state, op):
+    del op
+    return state
+
+  def byte_ROT_N(self, state, op):
+    del op
+    return state
+
+  def byte_GEN_START(self, state, op):
+    del op
+    return state
+
+  def byte_MATCH_CLASS(self, state, op):
+    del op
+    return state