Added support for typing.NoReturn

Fixes #131.

docs/userguide.rst

@@ -197,6 +197,7 @@ Type            Notes
 ``List``        Contents are typechecked
 ``Literal``
 ``NamedTuple``  Field values are typechecked
+``NoReturn``
 ``Protocol``    Value type checked with ``issubclass()`` against the protocol
 ``Set``         Contents are typechecked
 ``Sequence``    Contents are typechecked

docs/versionhistory.rst

@@ -3,6 +3,10 @@ Version history
 
 This library adheres to `Semantic Versioning 2.0 <https://semver.org/#semantic-versioning-200>`_.
 
+**UNRELEASED**
+
+- Added support for ``typing.NoReturn``
+
 **2.8.0** (2020-06-02)
 
 - Added support for the ``Mock`` and ``MagicMock`` types (PR by prescod)

tests/test_typeguard.py

@@ -10,6 +10,7 @@
     Container, Generic, BinaryIO, TextIO, Generator, Iterator, SupportsInt, AbstractSet, AnyStr)
 
 import pytest
+from typing_extensions import NoReturn
 
 from typeguard import (
     typechecked, check_argument_types, qualified_name, TypeChecker, TypeWarning, function_name,
@@ -1156,6 +1157,13 @@ def foo(arg: SupportsInt):
         else:
             foo(value)
 
+    def test_noreturn(self):
+        @typechecked
+        def foo() -> NoReturn:
+            pass
+
+        pytest.raises(TypeError, foo).match(r'foo\(\) was declared never to return but it did')
+
 
 class TestTypeChecker:
     @pytest.fixture

typeguard/__init__.py

@@ -43,6 +43,14 @@
     from typing import _ForwardRef as ForwardRef  # Python < 3.8
     evaluate_forwardref = ForwardRef._eval_type
 
+try:
+    from typing import NoReturn
+except ImportError:
+    try:
+        from typing_extensions import NoReturn
+    except ImportError:
+        NoReturn = None
+
 try:
     from inspect import isasyncgenfunction, isasyncgen
 except ImportError:
@@ -641,6 +649,9 @@ def check_return_type(retval, memo: Optional[_CallMemo] = None) -> bool:
         memo = _CallMemo(func, frame.f_locals)
 
     if 'return' in memo.type_hints:
+        if memo.type_hints['return'] is NoReturn:
+            raise TypeError('{}() was declared never to return but it did'.format(memo.func_name))
+
         try:
             check_type('the return value', retval, memo.type_hints['return'], memo)
         except TypeError as exc:  # suppress unnecessarily long tracebacks