Merge branch 'master' into experiments/typecheck-unreachable

Author: A5rocks

.github/workflows/test.yml

@@ -167,7 +167,7 @@ jobs:
         echo debug build; python -c 'import sysconfig; print(bool(sysconfig.get_config_var("Py_DEBUG")))'
         echo os.cpu_count; python -c 'import os; print(os.cpu_count())'
         echo os.sched_getaffinity; python -c 'import os; print(len(getattr(os, "sched_getaffinity", lambda *args: [])(0)))'
-        pip install setuptools==75.1.0 tox==4.21.2
+        pip install tox==4.21.2
 
     - name: Compiled with mypyc
       if: ${{ matrix.test_mypyc }}
@@ -230,7 +230,7 @@ jobs:
           default: 3.11.1
           command: python -c "import platform; print(f'{platform.architecture()=} {platform.machine()=}');"
       - name: Install tox
-        run: pip install setuptools==75.1.0 tox==4.21.2
+        run: pip install tox==4.21.2
       - name: Setup tox environment
         run: tox run -e py --notest
       - name: Test

docs/source/config_file.rst

@@ -432,7 +432,7 @@ Platform configuration
 
     Specifies the Python version used to parse and check the target
     program.  The string should be in the format ``MAJOR.MINOR`` --
-    for example ``2.7``.  The default is the version of the Python
+    for example ``3.9``.  The default is the version of the Python
     interpreter used to run mypy.
 
     This option may only be set in the global section (``[mypy]``).
@@ -1196,7 +1196,7 @@ of your repo (or append it to the end of an existing ``pyproject.toml`` file) an
     # mypy global options:
 
     [tool.mypy]
-    python_version = "2.7"
+    python_version = "3.9"
     warn_return_any = true
     warn_unused_configs = true
     exclude = [

mypy/argmap.py

@@ -249,10 +249,8 @@ def expand_actual_type(
                     formal_name = (set(actual_type.items.keys()) - self.kwargs_used).pop()
                 self.kwargs_used.add(formal_name)
                 return actual_type.items[formal_name]
-            elif (
-                isinstance(actual_type, Instance)
-                and len(actual_type.args) > 1
-                and is_subtype(actual_type, self.context.mapping_type)
+            elif isinstance(actual_type, Instance) and is_subtype(
+                actual_type, self.context.mapping_type
             ):
                 # Only `Mapping` type can be unpacked with `**`.
                 # Other types will produce an error somewhere else.

mypy/binder.py

@@ -7,8 +7,9 @@
 from typing_extensions import TypeAlias as _TypeAlias
 
 from mypy.erasetype import remove_instance_last_known_values
-from mypy.literals import Key, literal, literal_hash, subkeys
+from mypy.literals import Key, extract_var_from_literal_hash, literal, literal_hash, subkeys
 from mypy.nodes import Expression, IndexExpr, MemberExpr, NameExpr, RefExpr, TypeInfo, Var
+from mypy.options import Options
 from mypy.subtypes import is_same_type, is_subtype
 from mypy.typeops import make_simplified_union
 from mypy.types import (
@@ -40,6 +41,7 @@ class CurrentType(NamedTuple):
 
 class Frame:
     """A Frame represents a specific point in the execution of a program.
+
     It carries information about the current types of expressions at
     that point, arising either from assignments to those expressions
     or the result of isinstance checks and other type narrowing
@@ -99,7 +101,7 @@ class A:
     # This maps an expression to a list of bound types for every item in the union type.
     type_assignments: Assigns | None = None
 
-    def __init__(self) -> None:
+    def __init__(self, options: Options) -> None:
         # Each frame gets an increasing, distinct id.
         self.next_id = 1
 
@@ -133,6 +135,11 @@ def __init__(self) -> None:
         self.break_frames: list[int] = []
         self.continue_frames: list[int] = []
 
+        # If True, initial assignment to a simple variable (e.g. "x", but not "x.y")
+        # is added to the binder. This allows more precise narrowing and more
+        # flexible inference of variable types (--allow-redefinition-new).
+        self.bind_all = options.allow_redefinition_new
+
     def _get_id(self) -> int:
         self.next_id += 1
         return self.next_id
@@ -238,12 +245,20 @@ def update_from_options(self, frames: list[Frame]) -> bool:
         for key in keys:
             current_value = self._get(key)
             resulting_values = [f.types.get(key, current_value) for f in frames]
-            if any(x is None for x in resulting_values):
+            # Keys can be narrowed using two different semantics. The new semantics
+            # is enabled for plain variables when bind_all is true, and it allows
+            # variable types to be widened using subsequent assignments. This is
+            # tricky to support for instance attributes (primarily due to deferrals),
+            # so we don't use it for them.
+            old_semantics = not self.bind_all or extract_var_from_literal_hash(key) is None
+            if old_semantics and any(x is None for x in resulting_values):
                 # We didn't know anything about key before
                 # (current_value must be None), and we still don't
                 # know anything about key in at least one possible frame.
                 continue
 
+            resulting_values = [x for x in resulting_values if x is not None]
+
             if all_reachable and all(
                 x is not None and not x.from_assignment for x in resulting_values
             ):
@@ -290,7 +305,11 @@ def update_from_options(self, frames: list[Frame]) -> bool:
                     # still equivalent to such type).
                     if isinstance(type, UnionType):
                         type = collapse_variadic_union(type)
-                    if isinstance(type, ProperType) and isinstance(type, UnionType):
+                    if (
+                        old_semantics
+                        and isinstance(type, ProperType)
+                        and isinstance(type, UnionType)
+                    ):
                         # Simplify away any extra Any's that were added to the declared
                         # type when popping a frame.
                         simplified = UnionType.make_union(

mypy/build.py

@@ -2240,8 +2240,10 @@ def semantic_analysis_pass1(self) -> None:
         # TODO: Do this while constructing the AST?
         self.tree.names = SymbolTable()
         if not self.tree.is_stub:
-            # Always perform some low-key variable renaming
-            self.tree.accept(LimitedVariableRenameVisitor())
+            if not self.options.allow_redefinition_new:
+                # Perform some low-key variable renaming when assignments can't
+                # widen inferred types
+                self.tree.accept(LimitedVariableRenameVisitor())
             if options.allow_redefinition:
                 # Perform more renaming across the AST to allow variable redefinitions
                 self.tree.accept(VariableRenameVisitor())