Typecheck unreachable code

mypy/binder.py

@@ -22,6 +22,7 @@
     TypeOfAny,
     TypeType,
     TypeVarType,
+    UninhabitedType,
     UnionType,
     UnpackType,
     find_unpack_in_list,
@@ -65,6 +66,7 @@ def __init__(self, id: int, conditional_frame: bool = False) -> None:
         self.unreachable = False
         self.conditional_frame = conditional_frame
         self.suppress_unreachable_warnings = False
+        self.unreachable_warning_emitted = False
 
     def __repr__(self) -> str:
         return f"Frame({self.id}, {self.types}, {self.unreachable}, {self.conditional_frame})"
@@ -166,6 +168,10 @@ def put(self, expr: Expression, typ: Type, *, from_assignment: bool = True) -> N
 
         This is used for isinstance() etc. Assignments should go through assign_type().
         """
+        proper_typ = get_proper_type(typ)
+        if isinstance(proper_typ, UninhabitedType) and not proper_typ.ambiguous:
+            self.frames[-1].unreachable = True
+
         if not isinstance(expr, (IndexExpr, MemberExpr, NameExpr)):
             return
         if not literal(expr):
@@ -183,6 +189,9 @@ def unreachable(self) -> None:
     def suppress_unreachable_warnings(self) -> None:
         self.frames[-1].suppress_unreachable_warnings = True
 
+    def emitted_unreachable_warning(self) -> None:
+        self.frames[-1].unreachable_warning_emitted = True
+
     def get(self, expr: Expression) -> Type | None:
         key = literal_hash(expr)
         assert key is not None, "Internal error: binder tried to get non-literal"
@@ -199,6 +208,9 @@ def is_unreachable(self) -> bool:
     def is_unreachable_warning_suppressed(self) -> bool:
         return any(f.suppress_unreachable_warnings for f in self.frames)
 
+    def is_unreachable_warning_emitted(self) -> bool:
+        return any(f.unreachable_warning_emitted for f in self.frames)
+
     def cleanse(self, expr: Expression) -> None:
         """Remove all references to a Node from the binder."""
         key = literal_hash(expr)

mypy/checkexpr.py

@@ -1638,6 +1638,9 @@ def check_call(
                 object_type,
                 original_type=callee,
             )
+        elif isinstance(callee, UninhabitedType):
+            self.infer_arg_types_in_empty_context(args)
+            return (UninhabitedType(), UninhabitedType())
         else:
             return self.msg.not_callable(callee, context), AnyType(TypeOfAny.from_error)
 
@@ -1795,9 +1798,20 @@ def check_callable_call(
             callable_name,
         )
 
-        self.check_argument_types(
-            arg_types, arg_kinds, args, callee, formal_to_actual, context, object_type=object_type
-        )
+        if not (
+            isinstance(callable_node, RefExpr)
+            and callable_node.fullname in ("typing.assert_never", "typing_extensions.assert_never")
+            and self.chk.binder.is_unreachable()
+        ):
+            self.check_argument_types(
+                arg_types,
+                arg_kinds,
+                args,
+                callee,
+                formal_to_actual,
+                context,
+                object_type=object_type,
+            )
 
         if (
             callee.is_type_obj()
@@ -4273,34 +4287,41 @@ def check_boolean_op(self, e: OpExpr, context: Context) -> Type:
         elif e.op == "or":
             left_map, right_map = self.chk.find_isinstance_check(e.left)
 
+        left_impossible = left_map is None or any(
+            isinstance(get_proper_type(v), UninhabitedType) for v in left_map.values()
+        )
+        right_impossible = right_map is None or any(
+            isinstance(get_proper_type(v), UninhabitedType) for v in right_map.values()
+        )
+
         # If left_map is None then we know mypy considers the left expression
         # to be redundant.
         if (
             codes.REDUNDANT_EXPR in self.chk.options.enabled_error_codes
-            and left_map is None
+            and left_impossible
             # don't report an error if it's intentional
             and not e.right_always
         ):
             self.msg.redundant_left_operand(e.op, e.left)
 
         if (
             self.chk.should_report_unreachable_issues()
-            and right_map is None
+            and right_impossible
             # don't report an error if it's intentional
             and not e.right_unreachable
         ):
             self.msg.unreachable_right_operand(e.op, e.right)
 
         right_type = self.analyze_cond_branch(right_map, e.right, expanded_left_type)
 
-        if left_map is None and right_map is None:
+        if left_impossible and right_impossible:
             return UninhabitedType()
 
-        if right_map is None:
+        if right_impossible:
             # The boolean expression is statically known to be the left value
             assert left_map is not None
             return left_type
-        if left_map is None:
+        if left_impossible:
             # The boolean expression is statically known to be the right value
             assert right_map is not None
             return right_type
@@ -5798,9 +5819,13 @@ def check_for_comp(self, e: GeneratorExpr | DictionaryComprehension) -> None:
                     self.chk.push_type_map(true_map)
 
                 if codes.REDUNDANT_EXPR in self.chk.options.enabled_error_codes:
-                    if true_map is None:
+                    if true_map is None or any(
+                        isinstance(get_proper_type(t), UninhabitedType) for t in true_map.values()
+                    ):
                         self.msg.redundant_condition_in_comprehension(False, condition)
-                    elif false_map is None:
+                    elif false_map is None or any(
+                        isinstance(get_proper_type(t), UninhabitedType) for t in false_map.values()
+                    ):
                         self.msg.redundant_condition_in_comprehension(True, condition)
 
     def visit_conditional_expr(self, e: ConditionalExpr, allow_none_return: bool = False) -> Type:
@@ -5811,9 +5836,13 @@ def visit_conditional_expr(self, e: ConditionalExpr, allow_none_return: bool = F
         # but only for the current expression
         if_map, else_map = self.chk.find_isinstance_check(e.cond)
         if codes.REDUNDANT_EXPR in self.chk.options.enabled_error_codes:
-            if if_map is None:
+            if if_map is None or any(
+                isinstance(get_proper_type(t), UninhabitedType) for t in if_map.values()
+            ):
                 self.msg.redundant_condition_in_if(False, e.cond)
-            elif else_map is None:
+            elif else_map is None or any(
+                isinstance(get_proper_type(t), UninhabitedType) for t in else_map.values()
+            ):
                 self.msg.redundant_condition_in_if(True, e.cond)
 
         if_type = self.analyze_cond_branch(
@@ -5890,17 +5919,28 @@ def analyze_cond_branch(
         node: Expression,
         context: Type | None,
         allow_none_return: bool = False,
-        suppress_unreachable_errors: bool = True,
+        suppress_unreachable_errors: bool | None = None,
     ) -> Type:
+        # TODO: default based on flag (default to `True` if flag is not passed)
+        unreachable_errors_suppressed = (
+            suppress_unreachable_errors
+            if suppress_unreachable_errors is not None
+            else self.chk.binder.is_unreachable_warning_suppressed()
+        )
         with self.chk.binder.frame_context(can_skip=True, fall_through=0):
-            if map is None:
+            self.chk.push_type_map(map)
+
+            if map is None or any(
+                isinstance(get_proper_type(t), UninhabitedType) for t in map.values()
+            ):
                 # We still need to type check node, in case we want to
                 # process it for isinstance checks later. Since the branch was
                 # determined to be unreachable, any errors should be suppressed.
-                with self.msg.filter_errors(filter_errors=suppress_unreachable_errors):
+
+                with self.msg.filter_errors(filter_errors=unreachable_errors_suppressed):
                     self.accept(node, type_context=context, allow_none_return=allow_none_return)
                 return UninhabitedType()
-            self.chk.push_type_map(map)
+
             return self.accept(node, type_context=context, allow_none_return=allow_none_return)
 
     #

mypy/checkmember.py

@@ -70,6 +70,7 @@
     TypeVarLikeType,
     TypeVarTupleType,
     TypeVarType,
+    UninhabitedType,
     UnionType,
     get_proper_type,
 )
@@ -253,6 +254,8 @@ def _analyze_member_access(
     elif isinstance(typ, DeletedType):
         mx.msg.deleted_as_rvalue(typ, mx.context)
         return AnyType(TypeOfAny.from_error)
+    elif isinstance(typ, UninhabitedType):
+        return UninhabitedType()
     return report_missing_attribute(mx.original_type, typ, name, mx)
 
 

mypy/checkpattern.py

@@ -140,12 +140,11 @@ def visit_as_pattern(self, o: AsPattern) -> PatternType:
         else:
             typ, rest_type, type_map = current_type, UninhabitedType(), {}
 
-        if not is_uninhabited(typ) and o.name is not None:
+        if o.name is not None:
             typ, _ = self.chk.conditional_types_with_intersection(
                 current_type, [get_type_range(typ)], o, default=current_type
             )
-            if not is_uninhabited(typ):
-                type_map[o.name] = typ
+            type_map[o.name] = typ
 
         return PatternType(typ, rest_type, type_map)
 
@@ -470,14 +469,14 @@ def visit_mapping_pattern(self, o: MappingPattern) -> PatternType:
         captures: dict[Expression, Type] = {}
         for key, value in zip(o.keys, o.values):
             inner_type = self.get_mapping_item_type(o, current_type, key)
-            if inner_type is None:
+            if is_uninhabited(inner_type):
                 can_match = False
-                inner_type = self.chk.named_type("builtins.object")
+
             pattern_type = self.accept(value, inner_type)
             if is_uninhabited(pattern_type.type):
                 can_match = False
-            else:
-                self.update_type_map(captures, pattern_type.captures)
+
+            self.update_type_map(captures, pattern_type.captures)
 
         if o.rest is not None:
             mapping = self.chk.named_type("typing.Mapping")
@@ -502,13 +501,13 @@ def visit_mapping_pattern(self, o: MappingPattern) -> PatternType:
 
     def get_mapping_item_type(
         self, pattern: MappingPattern, mapping_type: Type, key: Expression
-    ) -> Type | None:
+    ) -> Type:
         mapping_type = get_proper_type(mapping_type)
         if isinstance(mapping_type, TypedDictType):
             with self.msg.filter_errors() as local_errors:
-                result: Type | None = self.chk.expr_checker.visit_typeddict_index_expr(
-                    mapping_type, key
-                )[0]
+                result: Type = self.chk.expr_checker.visit_typeddict_index_expr(mapping_type, key)[
+                    0
+                ]
                 has_local_errors = local_errors.has_new_errors()
             # If we can't determine the type statically fall back to treating it as a normal
             # mapping
@@ -517,7 +516,7 @@ def get_mapping_item_type(
                     result = self.get_simple_mapping_item_type(pattern, mapping_type, key)
 
                     if local_errors.has_new_errors():
-                        result = None
+                        result = UninhabitedType()
         else:
             with self.msg.filter_errors():
                 result = self.get_simple_mapping_item_type(pattern, mapping_type, key)

mypyc/ir/pprint.py

@@ -222,15 +222,16 @@ def visit_call_c(self, op: CallC) -> str:
     def visit_primitive_op(self, op: PrimitiveOp) -> str:
         args = []
         arg_index = 0
-        type_arg_index = 0
+        # type_arg_index = 0
         for arg_type in zip(op.desc.arg_types):
             if arg_type:
                 args.append(self.format("%r", op.args[arg_index]))
                 arg_index += 1
             else:
-                assert op.type_args
-                args.append(self.format("%r", op.type_args[type_arg_index]))
-                type_arg_index += 1
+                assert False
+                # assert op.type_args
+                # args.append(self.format("%r", op.type_args[type_arg_index]))
+                # type_arg_index += 1
 
         args_str = ", ".join(args)
         if op.is_void:

mypyc/test-data/irbuild-match.test

@@ -1765,10 +1765,8 @@ def f(x):
     r10 :: object
     r11 :: object[1]
     r12 :: object_ptr
-    r13, r14 :: object
-    r15 :: i32
-    r16 :: bit
-    r17, r18 :: bool
+    r13 :: object
+    r14 :: bool
 L0:
     r0 = __main__.Foo :: type
     r1 = PyObject_IsInstance(x, r0)
@@ -1792,13 +1790,9 @@ L2:
     goto L8
 L3:
 L4:
-    r14 = box(bool, 0)
-    r15 = PyObject_IsTrue(r14)
-    r16 = r15 >= 0 :: signed
-    r17 = truncate r15: i32 to builtins.bool
-    if r17 goto L6 else goto L5 :: bool
+    if 0 goto L6 else goto L5 :: bool
 L5:
-    r18 = raise AssertionError('Unreachable')
+    r14 = raise AssertionError('Unreachable')
     unreachable
 L6:
     goto L8

mypyc/test-data/run-singledispatch.test

@@ -347,11 +347,6 @@ def verify_typeinfo(stub: TypeInfo, a: MaybeMissing[Type[Any]], b: List[str]) ->
     yield Error('in TypeInfo')
     yield Error('hello')
 
-@verify.register(TypeVarExpr)
-def verify_typevarexpr(stub: TypeVarExpr, a: MaybeMissing[Any], b: List[str]) -> Iterator[Error]:
-    if False:
-        yield None
-
 def verify_list(stub, a, b) -> List[str]:
     """Helper function that converts iterator of errors to list of messages"""
     return list(err.msg for err in verify(stub, a, b))
@@ -361,7 +356,6 @@ def test_verify() -> None:
     assert verify_list(MypyFile(), MISSING, ['a', 'b']) == ["shouldn't be missing"]
     assert verify_list(MypyFile(), 5, ['a', 'b']) == ['in TypeInfo', 'hello']
     assert verify_list(TypeInfo(), str, ['a', 'b']) == ['in TypeInfo', 'hello']
-    assert verify_list(TypeVarExpr(), 'a', ['x', 'y']) == []
 
 
 [case testArgsInRegisteredImplNamedDifferentlyFromMainFunction]