Merge branch 'master' into narrowing/refine_partial_types_in_loops

# Conflicts:
#	test-data/unit/check-narrowing.test

mypy/binder.py

@@ -2,7 +2,7 @@
 
 from collections import defaultdict
 from contextlib import contextmanager
-from typing import DefaultDict, Iterator, List, Optional, Tuple, Union, cast
+from typing import DefaultDict, Iterator, List, NamedTuple, Optional, Tuple, Union
 from typing_extensions import TypeAlias as _TypeAlias
 
 from mypy.erasetype import remove_instance_last_known_values
@@ -30,6 +30,11 @@
 BindableExpression: _TypeAlias = Union[IndexExpr, MemberExpr, NameExpr]
 
 
+class CurrentType(NamedTuple):
+    type: Type
+    from_assignment: bool
+
+
 class Frame:
     """A Frame represents a specific point in the execution of a program.
     It carries information about the current types of expressions at
@@ -44,7 +49,7 @@ class Frame:
 
     def __init__(self, id: int, conditional_frame: bool = False) -> None:
         self.id = id
-        self.types: dict[Key, Type] = {}
+        self.types: dict[Key, CurrentType] = {}
         self.unreachable = False
         self.conditional_frame = conditional_frame
         self.suppress_unreachable_warnings = False
@@ -132,18 +137,18 @@ def push_frame(self, conditional_frame: bool = False) -> Frame:
         self.options_on_return.append([])
         return f
 
-    def _put(self, key: Key, type: Type, index: int = -1) -> None:
-        self.frames[index].types[key] = type
+    def _put(self, key: Key, type: Type, from_assignment: bool, index: int = -1) -> None:
+        self.frames[index].types[key] = CurrentType(type, from_assignment)
 
-    def _get(self, key: Key, index: int = -1) -> Type | None:
+    def _get(self, key: Key, index: int = -1) -> CurrentType | None:
         if index < 0:
             index += len(self.frames)
         for i in range(index, -1, -1):
             if key in self.frames[i].types:
                 return self.frames[i].types[key]
         return None
 
-    def put(self, expr: Expression, typ: Type) -> None:
+    def put(self, expr: Expression, typ: Type, *, from_assignment: bool = True) -> None:
         if not isinstance(expr, (IndexExpr, MemberExpr, NameExpr)):
             return
         if not literal(expr):
@@ -153,7 +158,7 @@ def put(self, expr: Expression, typ: Type) -> None:
         if key not in self.declarations:
             self.declarations[key] = get_declaration(expr)
             self._add_dependencies(key)
-        self._put(key, typ)
+        self._put(key, typ, from_assignment)
 
     def unreachable(self) -> None:
         self.frames[-1].unreachable = True
@@ -164,7 +169,10 @@ def suppress_unreachable_warnings(self) -> None:
     def get(self, expr: Expression) -> Type | None:
         key = literal_hash(expr)
         assert key is not None, "Internal error: binder tried to get non-literal"
-        return self._get(key)
+        found = self._get(key)
+        if found is None:
+            return None
+        return found.type
 
     def is_unreachable(self) -> bool:
         # TODO: Copy the value of unreachable into new frames to avoid
@@ -193,7 +201,7 @@ def update_from_options(self, frames: list[Frame]) -> bool:
         If a key is declared as AnyType, only update it if all the
         options are the same.
         """
-
+        all_reachable = all(not f.unreachable for f in frames)
         frames = [f for f in frames if not f.unreachable]
         changed = False
         keys = {key for f in frames for key in f.types}
@@ -207,17 +215,30 @@ def update_from_options(self, frames: list[Frame]) -> bool:
                 # know anything about key in at least one possible frame.
                 continue
 
-            type = resulting_values[0]
-            assert type is not None
+            if all_reachable and all(
+                x is not None and not x.from_assignment for x in resulting_values
+            ):
+                # Do not synthesize a new type if we encountered a conditional block
+                # (if, while or match-case) without assignments.
+                # See check-isinstance.test::testNoneCheckDoesNotMakeTypeVarOptional
+                # This is a safe assumption: the fact that we checked something with `is`
+                # or `isinstance` does not change the type of the value.
+                continue
+
+            current_type = resulting_values[0]
+            assert current_type is not None
+            type = current_type.type
             declaration_type = get_proper_type(self.declarations.get(key))
             if isinstance(declaration_type, AnyType):
                 # At this point resulting values can't contain None, see continue above
-                if not all(is_same_type(type, cast(Type, t)) for t in resulting_values[1:]):
+                if not all(
+                    t is not None and is_same_type(type, t.type) for t in resulting_values[1:]
+                ):
                     type = AnyType(TypeOfAny.from_another_any, source_any=declaration_type)
             else:
                 for other in resulting_values[1:]:
                     assert other is not None
-                    type = join_simple(self.declarations[key], type, other)
+                    type = join_simple(self.declarations[key], type, other.type)
                     # Try simplifying resulting type for unions involving variadic tuples.
                     # Technically, everything is still valid without this step, but if we do
                     # not do this, this may create long unions after exiting an if check like:
@@ -236,8 +257,8 @@ def update_from_options(self, frames: list[Frame]) -> bool:
                         )
                         if simplified == self.declarations[key]:
                             type = simplified
-            if current_value is None or not is_same_type(type, current_value):
-                self._put(key, type)
+            if current_value is None or not is_same_type(type, current_value[0]):
+                self._put(key, type, from_assignment=True)
                 changed = True
 
         self.frames[-1].unreachable = not frames
@@ -374,7 +395,9 @@ def most_recent_enclosing_type(self, expr: BindableExpression, type: Type) -> Ty
         key = literal_hash(expr)
         assert key is not None
         enclosers = [get_declaration(expr)] + [
-            f.types[key] for f in self.frames if key in f.types and is_subtype(type, f.types[key])
+            f.types[key].type
+            for f in self.frames
+            if key in f.types and is_subtype(type, f.types[key][0])
         ]
         return enclosers[-1]
 

mypy/checker.py

@@ -4728,11 +4728,11 @@ def visit_if_stmt(self, s: IfStmt) -> None:
 
                 # XXX Issue a warning if condition is always False?
                 with self.binder.frame_context(can_skip=True, fall_through=2):
-                    self.push_type_map(if_map)
+                    self.push_type_map(if_map, from_assignment=False)
                     self.accept(b)
 
                 # XXX Issue a warning if condition is always True?
-                self.push_type_map(else_map)
+                self.push_type_map(else_map, from_assignment=False)
 
             with self.binder.frame_context(can_skip=False, fall_through=2):
                 if s.else_body:
@@ -5313,18 +5313,21 @@ def visit_match_stmt(self, s: MatchStmt) -> None:
                     if b.is_unreachable or isinstance(
                         get_proper_type(pattern_type.type), UninhabitedType
                     ):
-                        self.push_type_map(None)
+                        self.push_type_map(None, from_assignment=False)
                         else_map: TypeMap = {}
                     else:
                         pattern_map, else_map = conditional_types_to_typemaps(
                             named_subject, pattern_type.type, pattern_type.rest_type
                         )
                         self.remove_capture_conflicts(pattern_type.captures, inferred_types)
-                        self.push_type_map(pattern_map)
+                        self.push_type_map(pattern_map, from_assignment=False)
                         if pattern_map:
                             for expr, typ in pattern_map.items():
-                                self.push_type_map(self._get_recursive_sub_patterns_map(expr, typ))
-                        self.push_type_map(pattern_type.captures)
+                                self.push_type_map(
+                                    self._get_recursive_sub_patterns_map(expr, typ),
+                                    from_assignment=False,
+                                )
+                        self.push_type_map(pattern_type.captures, from_assignment=False)
                     if g is not None:
                         with self.binder.frame_context(can_skip=False, fall_through=3):
                             gt = get_proper_type(self.expr_checker.accept(g))
@@ -5350,11 +5353,11 @@ def visit_match_stmt(self, s: MatchStmt) -> None:
                                                 continue
                                             type_map[named_subject] = type_map[expr]
 
-                            self.push_type_map(guard_map)
+                            self.push_type_map(guard_map, from_assignment=False)
                             self.accept(b)
                     else:
                         self.accept(b)
-                self.push_type_map(else_map)
+                self.push_type_map(else_map, from_assignment=False)
 
             # This is needed due to a quirk in frame_context. Without it types will stay narrowed
             # after the match.
@@ -7375,12 +7378,12 @@ def iterable_item_type(
     def function_type(self, func: FuncBase) -> FunctionLike:
         return function_type(func, self.named_type("builtins.function"))
 
-    def push_type_map(self, type_map: TypeMap) -> None:
+    def push_type_map(self, type_map: TypeMap, *, from_assignment: bool = True) -> None:
         if type_map is None:
             self.binder.unreachable()
         else:
             for expr, type in type_map.items():
-                self.binder.put(expr, type)
+                self.binder.put(expr, type, from_assignment=from_assignment)
 
     def infer_issubclass_maps(self, node: CallExpr, expr: Expression) -> tuple[TypeMap, TypeMap]:
         """Infer type restrictions for an expression in issubclass call."""
@@ -7753,9 +7756,7 @@ def conditional_types(
         ) and is_proper_subtype(current_type, proposed_type, ignore_promotions=True):
             # Expression is always of one of the types in proposed_type_ranges
             return default, UninhabitedType()
-        elif not is_overlapping_types(
-            current_type, proposed_type, prohibit_none_typevar_overlap=True, ignore_promotions=True
-        ):
+        elif not is_overlapping_types(current_type, proposed_type, ignore_promotions=True):
             # Expression is never of any type in proposed_type_ranges
             return UninhabitedType(), default
         else:

mypy/semanal.py

@@ -484,6 +484,12 @@ def __init__(
         # Used to pass information about current overload index to visit_func_def().
         self.current_overload_item: int | None = None
 
+        # Used to track whether currently inside an except* block. This helps
+        # to invoke errors when continue/break/return is used inside except* block.
+        self.inside_except_star_block: bool = False
+        # Used to track edge case when return is still inside except* if it enters a loop
+        self.return_stmt_inside_except_star_block: bool = False
+
     # mypyc doesn't properly handle implementing an abstractproperty
     # with a regular attribute so we make them properties
     @property
@@ -511,6 +517,25 @@ def allow_unbound_tvars_set(self) -> Iterator[None]:
         finally:
             self.allow_unbound_tvars = old
 
+    @contextmanager
+    def inside_except_star_block_set(
+        self, value: bool, entering_loop: bool = False
+    ) -> Iterator[None]:
+        old = self.inside_except_star_block
+        self.inside_except_star_block = value
+
+        # Return statement would still be in except* scope if entering loops
+        if not entering_loop:
+            old_return_stmt_flag = self.return_stmt_inside_except_star_block
+            self.return_stmt_inside_except_star_block = value
+
+        try:
+            yield
+        finally:
+            self.inside_except_star_block = old
+            if not entering_loop:
+                self.return_stmt_inside_except_star_block = old_return_stmt_flag
+
     #
     # Preparing module (performed before semantic analysis)
     #
@@ -877,7 +902,8 @@ def visit_func_def(self, defn: FuncDef) -> None:
             return
 
         with self.scope.function_scope(defn):
-            self.analyze_func_def(defn)
+            with self.inside_except_star_block_set(value=False):
+                self.analyze_func_def(defn)
 
     def function_fullname(self, fullname: str) -> str:
         if self.current_overload_item is None:
@@ -1684,6 +1710,7 @@ def visit_decorator(self, dec: Decorator) -> None:
                     "abc.abstractproperty",
                     "functools.cached_property",
                     "enum.property",
+                    "types.DynamicClassAttribute",
                 ),
             ):
                 removed.append(i)
@@ -5263,6 +5290,8 @@ def visit_return_stmt(self, s: ReturnStmt) -> None:
         self.statement = s
         if not self.is_func_scope():
             self.fail('"return" outside function', s)
+        if self.return_stmt_inside_except_star_block:
+            self.fail('"return" not allowed in except* block', s, serious=True)
         if s.expr:
             s.expr.accept(self)
 
@@ -5296,7 +5325,8 @@ def visit_while_stmt(self, s: WhileStmt) -> None:
         self.statement = s
         s.expr.accept(self)
         self.loop_depth[-1] += 1
-        s.body.accept(self)
+        with self.inside_except_star_block_set(value=False, entering_loop=True):
+            s.body.accept(self)
         self.loop_depth[-1] -= 1
         self.visit_block_maybe(s.else_body)
 
@@ -5320,20 +5350,24 @@ def visit_for_stmt(self, s: ForStmt) -> None:
                 s.index_type = analyzed
 
         self.loop_depth[-1] += 1
-        self.visit_block(s.body)
+        with self.inside_except_star_block_set(value=False, entering_loop=True):
+            self.visit_block(s.body)
         self.loop_depth[-1] -= 1
-
         self.visit_block_maybe(s.else_body)
 
     def visit_break_stmt(self, s: BreakStmt) -> None:
         self.statement = s
         if self.loop_depth[-1] == 0:
             self.fail('"break" outside loop', s, serious=True, blocker=True)
+        if self.inside_except_star_block:
+            self.fail('"break" not allowed in except* block', s, serious=True)
 
     def visit_continue_stmt(self, s: ContinueStmt) -> None:
         self.statement = s
         if self.loop_depth[-1] == 0:
             self.fail('"continue" outside loop', s, serious=True, blocker=True)
+        if self.inside_except_star_block:
+            self.fail('"continue" not allowed in except* block', s, serious=True)
 
     def visit_if_stmt(self, s: IfStmt) -> None:
         self.statement = s
@@ -5354,7 +5388,8 @@ def analyze_try_stmt(self, s: TryStmt, visitor: NodeVisitor[None]) -> None:
                 type.accept(visitor)
             if var:
                 self.analyze_lvalue(var)
-            handler.accept(visitor)
+            with self.inside_except_star_block_set(self.inside_except_star_block or s.is_star):
+                handler.accept(visitor)
         if s.else_body:
             s.else_body.accept(visitor)
         if s.finally_body:

mypy/typeanal.py

@@ -180,7 +180,7 @@ def analyze_type_alias(
     )
     analyzer.in_dynamic_func = in_dynamic_func
     analyzer.global_scope = global_scope
-    res = type.accept(analyzer)
+    res = analyzer.anal_type(type, nested=False)
     return res, analyzer.aliases_used
 
 

test-data/unit/check-enum.test

@@ -815,7 +815,7 @@ elif x is Foo.C:
     reveal_type(x)  # N: Revealed type is "Literal[__main__.Foo.C]"
 else:
     reveal_type(x)  # No output here: this branch is unreachable
-reveal_type(x) # N: Revealed type is "__main__.Foo"
+reveal_type(x) # N: Revealed type is "Union[Literal[__main__.Foo.A], Literal[__main__.Foo.B], Literal[__main__.Foo.C]]"
 
 if Foo.A is x:
     reveal_type(x)  # N: Revealed type is "Literal[__main__.Foo.A]"
@@ -825,7 +825,7 @@ elif Foo.C is x:
     reveal_type(x)  # N: Revealed type is "Literal[__main__.Foo.C]"
 else:
     reveal_type(x)  # No output here: this branch is unreachable
-reveal_type(x) # N: Revealed type is "__main__.Foo"
+reveal_type(x) # N: Revealed type is "Union[Literal[__main__.Foo.A], Literal[__main__.Foo.B], Literal[__main__.Foo.C]]"
 
 y: Foo
 if y is Foo.A:

test-data/unit/check-isinstance.test

@@ -2207,23 +2207,24 @@ def foo2(x: Optional[str]) -> None:
         reveal_type(x)      # N: Revealed type is "builtins.str"
 [builtins fixtures/isinstance.pyi]
 
-[case testNoneCheckDoesNotNarrowWhenUsingTypeVars]
-
-# Note: this test (and the following one) are testing checker.conditional_type_map:
-# if you set the 'prohibit_none_typevar_overlap' keyword argument to False when calling
-# 'is_overlapping_types', the binder will incorrectly infer that 'out' has a type of
-# Union[T, None] after the if statement.
-
+[case testNoneCheckDoesNotMakeTypeVarOptional]
 from typing import TypeVar
 
 T = TypeVar('T')
 
-def foo(x: T) -> T:
+def foo_if(x: T) -> T:
     out = None
     out = x
     if out is None:
         pass
     return out
+
+def foo_while(x: T) -> T:
+    out = None
+    out = x
+    while out is None:
+        pass
+    return out
 [builtins fixtures/isinstance.pyi]
 
 [case testNoneCheckDoesNotNarrowWhenUsingTypeVarsNoStrictOptional]