Fail with an explicit error on PyPy (#20384)

Fixes mypyc/librt#21

Fail with an explicit user-friendly error on PyPy.

Author: ilevkivskyi

mypy-requirements.txt

@@ -4,4 +4,4 @@ typing_extensions>=4.6.0
 mypy_extensions>=1.0.0
 pathspec>=0.9.0
 tomli>=1.1.0; python_version<'3.11'
-librt>=0.6.2
+librt>=0.6.2; platform_python_implementation != 'PyPy'

pyproject.toml

@@ -9,7 +9,7 @@ requires = [
     "mypy_extensions>=1.0.0",
     "pathspec>=0.9.0",
     "tomli>=1.1.0; python_version<'3.11'",
-    "librt>=0.6.2",
+    "librt>=0.6.2; platform_python_implementation != 'PyPy'",
     # the following is from build-requirements.txt
     "types-psutil",
     "types-setuptools",
@@ -54,7 +54,7 @@ dependencies = [
   "mypy_extensions>=1.0.0",
   "pathspec>=0.9.0",
   "tomli>=1.1.0; python_version<'3.11'",
-  "librt>=0.6.2",
+  "librt>=0.6.2; platform_python_implementation != 'PyPy'",
 ]
 dynamic = ["version"]
 

setup.py

@@ -5,13 +5,22 @@
 import glob
 import os
 import os.path
+import platform
 import sys
 from typing import TYPE_CHECKING, Any
 
 if sys.version_info < (3, 9, 0):  # noqa: UP036, RUF100
     sys.stderr.write("ERROR: You need Python 3.9 or later to use mypy.\n")
     exit(1)
 
+if platform.python_implementation() == "PyPy":
+    sys.stderr.write(
+        "ERROR: Running mypy on PyPy is not supported yet.\n"
+        "To type-check a PyPy library please use an equivalent CPython version,\n"
+        "see https://github.com/mypyc/librt/issues/16 for possible workarounds.\n"
+    )
+    exit(1)
+
 # we'll import stuff from the source tree, let's ensure is on the sys path
 sys.path.insert(0, os.path.dirname(os.path.realpath(__file__)))
 

test-requirements.txt

@@ -22,7 +22,7 @@ identify==2.6.15
     # via pre-commit
 iniconfig==2.1.0
     # via pytest
-librt==0.6.2
+librt==0.7.3 ; platform_python_implementation != 'PyPy'
     # via -r mypy-requirements.txt
 lxml==6.0.2 ; python_version < "3.15"
     # via -r test-requirements.in