Upgraded to mypy 1.5.1

We upgraded to mypy 1.5.1 (current latest version) and removed a couple
of unnecessary casts that mypy now does not need anymore.

Since mypy dropped support for Python 3.7, we exclude the check in the
pre-commit script for Python versions below 3.8.

icontract/_recompute.py

@@ -652,8 +652,7 @@ def visit_NamedExpr(self, node: ast.NamedExpr) -> Any:
 
             self.recomputed_values[node] = value
 
-            # This assignment is needed to make mypy happy.
-            target = cast(ast.Name, node.target)
+            target = node.target
 
             if not isinstance(target.ctx, ast.Store):
                 raise NotImplementedError(

icontract/_represent.py

@@ -106,8 +106,7 @@ def visit_NamedExpr(self, node: ast.NamedExpr) -> Any:
             if node in self._recomputed_values:
                 value = self._recomputed_values[node]
 
-                # This is necessary in order to make mypy happy.
-                target = cast(ast.Name, node.target)
+                target = node.target
 
                 if _representable(value=value):
                     self.reprs[target.id] = value

precommit.py

@@ -41,19 +41,23 @@ def main() -> int:
         subprocess.check_call(
             ["yapf", "--diff", "--style=style.yapf", "--recursive"] + yapf_targets, cwd=str(repo_root))
 
-    print("Mypy'ing...")
-    mypy_targets = ["icontract", "tests"]
-    if sys.version_info >= (3, 6):
-        mypy_targets.append('tests_3_6')
+    if sys.version_info < (3, 8):
+        print("Mypy since 1.5 dropped support for Python 3.7 and "
+              "you are running Python %s, so skipping.".format(sys.version_info))
+    else:
+        print("Mypy'ing...")
+        mypy_targets = ["icontract", "tests"]
+        if sys.version_info >= (3, 6):
+            mypy_targets.append('tests_3_6')
 
-    if sys.version_info >= (3, 7):
-        mypy_targets.append('tests_3_7')
+        if sys.version_info >= (3, 7):
+            mypy_targets.append('tests_3_7')
 
-    if sys.version_info >= (3, 8):
-        mypy_targets.append('tests_3_8')
-        mypy_targets.append('tests_with_others')
+        if sys.version_info >= (3, 8):
+            mypy_targets.append('tests_3_8')
+            mypy_targets.append('tests_with_others')
 
-    subprocess.check_call(["mypy", "--strict"] + mypy_targets, cwd=str(repo_root))
+        subprocess.check_call(["mypy", "--strict"] + mypy_targets, cwd=str(repo_root))
 
     print("Pylint'ing...")
     pylint_targets = ['icontract', 'tests']

setup.py

@@ -51,11 +51,12 @@
     install_requires=install_requires,
     extras_require={
         'dev': [
-            'mypy==0.991', 'pylint==2.13.9', 'yapf==0.20.2', 'tox>=3.0.0', 'pydocstyle>=6.1.1,<7', 'coverage>=4.5.1,<5',
+            'pylint==2.13.9', 'yapf==0.20.2', 'tox>=3.0.0', 'pydocstyle>=6.1.1,<7', 'coverage>=4.5.1,<5',
             'docutils>=0.14,<1', 'pygments>=2.2.0,<3', 'dpcontracts==0.6.0', 'tabulate>=0.8.7,<1',
             'py-cpuinfo>=5.0.0,<6', 'typeguard>=2,<3', 'astor==0.8.1', 'numpy>=1,<2'
-        ] + (['deal==4.23.3'] if sys.version_info >= (3, 8) else []) + (['asyncstdlib==3.9.1']
-                                                                        if sys.version_info >= (3, 8) else []),
+        ] + (['mypy==1.5.1'] if sys.version_info >= (3, 8) else []) +
+        (['deal==4.23.3'] if sys.version_info >= (3, 8) else []) + (['asyncstdlib==3.9.1']
+                                                                    if sys.version_info >= (3, 8) else []),
     },
     py_modules=['icontract'],
     package_data={"icontract": ["py.typed"]},