type add some typing changes required by Mypyc (#1658)

* Add Final annotations

* Add TLineNo annotations

* Use single assignment for class var

coverage/config.py

@@ -13,7 +13,7 @@
 import re
 
 from typing import (
-    Any, Callable, Union,
+    Any, Callable, Final, Union,
 )
 from collections.abc import Iterable
 
@@ -360,7 +360,8 @@ def copy(self) -> CoverageConfig:
         """Return a copy of the configuration."""
         return copy.deepcopy(self)
 
-    CONCURRENCY_CHOICES = {"thread", "gevent", "greenlet", "eventlet", "multiprocessing"}
+    CONCURRENCY_CHOICES: Final[set[str]] = {
+        "thread", "gevent", "greenlet", "eventlet", "multiprocessing"}
 
     CONFIG_FILE_OPTIONS = [
         # These are *args for _set_attr_from_config_option:

coverage/debug.py

@@ -21,7 +21,7 @@
 
 from typing import (
     overload,
-    Any, Callable, IO,
+    Any, Callable, Final, IO,
 )
 from collections.abc import Iterable, Iterator, Mapping
 
@@ -467,8 +467,8 @@ def get_one(
     # a process-wide singleton. So stash it in sys.modules instead of
     # on a class attribute. Yes, this is aggressively gross.
 
-    SYS_MOD_NAME = "$coverage.debug.DebugOutputFile.the_one"
-    SINGLETON_ATTR = "the_one_and_is_interim"
+    SYS_MOD_NAME: Final[str] = "$coverage.debug.DebugOutputFile.the_one"
+    SINGLETON_ATTR: Final[str] = "the_one_and_is_interim"
 
     @classmethod
     def _set_singleton_data(cls, the_one: DebugOutputFile, interim: bool) -> None:

coverage/env.py

@@ -9,7 +9,7 @@
 import platform
 import sys
 
-from typing import Any
+from typing import Any, Final
 from collections.abc import Iterable
 
 # debug_info() at the bottom wants to show all the globals, but not imports.
@@ -53,10 +53,7 @@ class PYBEHAVIOR:
 
     # Is "if not __debug__" optimized away? The exact details have changed
     # across versions.
-    if pep626:
-        optimize_if_not_debug = 1
-    else:
-        optimize_if_not_debug = 2
+    optimize_if_not_debug = 1 if pep626 else 2
 
     # 3.7 changed how functions with only docstrings are numbered.
     docstring_only_function = (not PYPY) and (PYVERSION <= (3, 10))
@@ -148,7 +145,7 @@ class PYBEHAVIOR:
     soft_keywords = (PYVERSION >= (3, 10))
 
     # PEP669 Low Impact Monitoring: https://peps.python.org/pep-0669/
-    pep669 = bool(getattr(sys, "monitoring", None))
+    pep669: Final[bool] = bool(getattr(sys, "monitoring", None))
 
     # Where does frame.f_lasti point when yielding from a generator?
     # It used to point at the YIELD, in 3.13 it points at the RESUME,

coverage/parser.py

@@ -466,7 +466,7 @@ def _line_numbers(self) -> Iterable[TLineNo]:
             byte_increments = self.code.co_lnotab[0::2]
             line_increments = self.code.co_lnotab[1::2]
 
-            last_line_num = None
+            last_line_num: TLineNo | None = None
             line_num = self.code.co_firstlineno
             byte_num = 0
             for byte_incr, line_incr in zip(byte_increments, line_increments):

coverage/results.py

@@ -343,7 +343,7 @@ def _line_ranges(
     lines = sorted(lines)
 
     pairs = []
-    start = None
+    start: TLineNo | None = None
     lidx = 0
     for stmt in statements:
         if lidx >= len(lines):