[3.15] Detect slice type subscription support

Author: netromdk

README.rst

@@ -155,9 +155,9 @@ generalized unpacking, ellipsis literal (``...``) out of slices, dictionary unio
 keyword, pattern matching with ``match``, union types written as ``X | Y``, type alias statements
 (``type X = SomeType``), type alias statements with lambdas/comprehensions in class scopes, generic
 classes (``class C[T]: ...``), template string literals (``t'{var}'``), lazy imports (``lazy
-import``, ``lazy from ... import``), and special module attributes like ``__lazy_modules__``. It
-tries to detect and ignore user-defined functions, classes, arguments, and variables with names that
-clash with library-defined symbols.
+import``, ``lazy from ... import``), special module attributes like ``__lazy_modules__``, and slice
+type subscription (``slice[1:2:3]``). It tries to detect and ignore user-defined functions, classes,
+arguments, and variables with names that clash with library-defined symbols.
 
 Caveats
 =======

tests/lang.py

@@ -1206,6 +1206,15 @@ def test_lazy_modules(self):
 
     visitor = self.visit("__all__ = []")
     self.assertFalse(visitor.lazy_modules())
+
+  def test_slice_subscription(self):
+    visitor = self.visit("x = slice[1:2:3]")
+    self.assertTrue(visitor.slice_subscription())
+    self.assertOnlyIn((3, 15), visitor.minimum_versions())
+
+    visitor = self.visit("x = slice(1, 2, 3)")
+    self.assertFalse(visitor.slice_subscription())
+
   @VerminTest.skipUnlessVersion(3, 5)
   def test_bytes_format(self):
     visitor = self.visit("b'%x' % 10")

vermin/source_state.py

@@ -138,6 +138,9 @@ def __init__(self, config, path=None, source=None):
 
     # `__lazy_modules__` module attribute.
     self.lazy_modules = False
+
+    # `slice` type subscript support, e.g. `slice[1:2:3]`.
+    self.slice_subscription = False
     # Imported members of modules, like "exc_clear" of "sys".
     self.import_mem_mod = {}
 

vermin/source_visitor.py

@@ -285,6 +285,9 @@ def lazy_imports(self):
   def lazy_modules(self):
     return self.__s.lazy_modules
 
+  def slice_subscription(self):
+    return self.__s.slice_subscription
+
   def __get_source_line(self, line, col=0):
     if self.__s.source is None:
       return None  # pragma: no cover
@@ -550,6 +553,10 @@ def minimum_versions(self):
       mins = self.__add_versions_entity(mins, (None, (3, 15)),
                                         "`__lazy_modules__`")
 
+    if self.slice_subscription():
+      mins = self.__add_versions_entity(mins, (None, (3, 15)),
+                                        "slice subscription")
+
     for directive in self.strftime_directives():
       if directive in STRFTIME_REQS:
         vers = STRFTIME_REQS[directive]
@@ -2291,6 +2298,13 @@ def match(name):
           if is_ellipsis_node(n):
             self.__s.ellipsis_nodes_in_slices.add(n)
 
+    # `slice[...]` subscript support (3.15+).
+    if isinstance(node.value, ast.Name) and node.value.id == "slice" \
+       and "slice" not in self.__s.user_defs:
+      self.__s.slice_subscription = True
+      self.__vvprint("slice subscription", line=node.lineno,
+                     versions=[None, (3, 15)])
+
     self.generic_visit(node)
 
   def visit_Match(self, node):