Last strict optional fixes (#4070)

This makes mypy completely --strict-optional clean.

Fixes #1955.

mypy/checker.py

@@ -1814,9 +1814,9 @@ def check_multi_assignment_from_iterable(self, lvalues: List[Lvalue], rvalue_typ
     def check_lvalue(self, lvalue: Lvalue) -> Tuple[Optional[Type],
                                                     Optional[IndexExpr],
                                                     Optional[Var]]:
-        lvalue_type = None  # type: Optional[Type]
-        index_lvalue = None  # type: Optional[IndexExpr]
-        inferred = None  # type: Optional[Var]
+        lvalue_type = None
+        index_lvalue = None
+        inferred = None
 
         if self.is_definition(lvalue):
             if isinstance(lvalue, NameExpr):
@@ -2781,12 +2781,10 @@ def iterable_item_type(self, instance: Instance) -> Type:
     def function_type(self, func: FuncBase) -> FunctionLike:
         return function_type(func, self.named_type('builtins.function'))
 
-    # TODO: These next two functions should refer to TypeMap below
-    def find_isinstance_check(self, n: Expression) -> Tuple[Optional[Dict[Expression, Type]],
-                                                            Optional[Dict[Expression, Type]]]:
+    def find_isinstance_check(self, n: Expression) -> 'Tuple[TypeMap, TypeMap]':
         return find_isinstance_check(n, self.type_map)
 
-    def push_type_map(self, type_map: Optional[Dict[Expression, Type]]) -> None:
+    def push_type_map(self, type_map: 'TypeMap') -> None:
         if type_map is None:
             self.binder.unreachable()
         else:

mypy/checkexpr.py

@@ -721,8 +721,7 @@ def infer_arg_types_in_context2(
 
         Returns the inferred types of *actual arguments*.
         """
-        dummy = None  # type: Any
-        res = [dummy] * len(args)  # type: List[Type]
+        res = [None] * len(args)  # type: List[Optional[Type]]
 
         for i, actuals in enumerate(formal_to_actual):
             for ai in actuals:
@@ -733,7 +732,8 @@ def infer_arg_types_in_context2(
         for i, t in enumerate(res):
             if not t:
                 res[i] = self.accept(args[i])
-        return res
+        assert all(tp is not None for tp in res)
+        return cast(List[Type], res)
 
     def infer_function_type_arguments_using_context(
             self, callable: CallableType, error_context: Context) -> CallableType:
@@ -2648,7 +2648,7 @@ def is_async_def(t: Type) -> bool:
 def map_actuals_to_formals(caller_kinds: List[int],
                            caller_names: Optional[Sequence[Optional[str]]],
                            callee_kinds: List[int],
-                           callee_names: List[Optional[str]],
+                           callee_names: Sequence[Optional[str]],
                            caller_arg_type: Callable[[int],
                                                      Type]) -> List[List[int]]:
     """Calculate mapping between actual (caller) args and formals.

mypy/nodes.py

@@ -4,7 +4,7 @@
 from abc import abstractmethod
 from collections import OrderedDict
 from typing import (
-    Any, TypeVar, List, Tuple, cast, Set, Dict, Union, Optional, Callable,
+    Any, TypeVar, List, Tuple, cast, Set, Dict, Union, Optional, Callable, Sequence,
 )
 
 import mypy.strconv
@@ -1786,11 +1786,11 @@ class NewTypeExpr(Expression):
     """NewType expression NewType(...)."""
     name = None  # type: str
     # The base type (the second argument to NewType)
-    old_type = None  # type: mypy.types.Type
+    old_type = None  # type: Optional[mypy.types.Type]
     # The synthesized class representing the new type (inherits old_type)
     info = None  # type: Optional[TypeInfo]
 
-    def __init__(self, name: str, old_type: 'mypy.types.Type', line: int) -> None:
+    def __init__(self, name: str, old_type: 'Optional[mypy.types.Type]', line: int) -> None:
         self.name = name
         self.old_type = old_type
 
@@ -2552,7 +2552,7 @@ def check_arg_kinds(arg_kinds: List[int], nodes: List[T], fail: Callable[[str, T
             is_kw_arg = True
 
 
-def check_arg_names(names: List[Optional[str]], nodes: List[T], fail: Callable[[str, T], None],
+def check_arg_names(names: Sequence[Optional[str]], nodes: List[T], fail: Callable[[str, T], None],
                     description: str = 'function definition') -> None:
     seen_names = set()  # type: Set[Optional[str]]
     for name, node in zip(names, nodes):

mypy/semanal_pass3.py

@@ -152,7 +152,7 @@ def visit_decorator(self, dec: Decorator) -> None:
         for expr in dec.decorators:
             preserve_type = False
             if isinstance(expr, RefExpr) and isinstance(expr.node, FuncDef):
-                if is_identity_signature(expr.node.type):
+                if expr.node.type and is_identity_signature(expr.node.type):
                     preserve_type = True
             if not preserve_type:
                 decorator_preserves_type = False
@@ -246,31 +246,38 @@ def perform_transform(self, node: Union[Node, SymbolTableNode],
                           transform: Callable[[Type], Type]) -> None:
         """Apply transform to all types associated with node."""
         if isinstance(node, ForStmt):
-            node.index_type = transform(node.index_type)
+            if node.index_type:
+                node.index_type = transform(node.index_type)
             self.transform_types_in_lvalue(node.index, transform)
         if isinstance(node, WithStmt):
-            node.target_type = transform(node.target_type)
+            if node.target_type:
+                node.target_type = transform(node.target_type)
             for n in node.target:
                 if isinstance(n, NameExpr) and isinstance(n.node, Var) and n.node.type:
                     n.node.type = transform(n.node.type)
         if isinstance(node, (FuncDef, CastExpr, AssignmentStmt, TypeAliasExpr, Var)):
+            assert node.type, "Scheduled patch for non-existent type"
             node.type = transform(node.type)
         if isinstance(node, NewTypeExpr):
+            assert node.old_type, "Scheduled patch for non-existent type"
             node.old_type = transform(node.old_type)
         if isinstance(node, TypeVarExpr):
             if node.upper_bound:
                 node.upper_bound = transform(node.upper_bound)
             if node.values:
                 node.values = [transform(v) for v in node.values]
         if isinstance(node, TypedDictExpr):
+            assert node.info.typeddict_type, "Scheduled patch for non-existent type"
             node.info.typeddict_type = cast(TypedDictType,
                                             transform(node.info.typeddict_type))
         if isinstance(node, NamedTupleExpr):
+            assert node.info.tuple_type, "Scheduled patch for non-existent type"
             node.info.tuple_type = cast(TupleType,
                                         transform(node.info.tuple_type))
         if isinstance(node, TypeApplication):
             node.types = [transform(t) for t in node.types]
         if isinstance(node, SymbolTableNode):
+            assert node.type_override, "Scheduled patch for non-existent type"
             node.type_override = transform(node.type_override)
         if isinstance(node, TypeInfo):
             for tvar in node.defn.type_vars:
@@ -296,7 +303,8 @@ def transform_types_in_lvalue(self, lvalue: Lvalue,
         if isinstance(lvalue, RefExpr):
             if isinstance(lvalue.node, Var):
                 var = lvalue.node
-                var.type = transform(var.type)
+                if var.type:
+                    var.type = transform(var.type)
         elif isinstance(lvalue, TupleExpr):
             for item in lvalue.items:
                 self.transform_types_in_lvalue(item, transform)
@@ -355,7 +363,7 @@ def fail(self, msg: str, ctx: Context, *, blocker: bool = False) -> None:
     def fail_blocker(self, msg: str, ctx: Context) -> None:
         self.fail(msg, ctx, blocker=True)
 
-    def builtin_type(self, name: str, args: List[Type] = None) -> Instance:
+    def builtin_type(self, name: str, args: Optional[List[Type]] = None) -> Instance:
         names = self.modules['builtins']
         sym = names.names[name]
         node = sym.node

mypy/typeanal.py

@@ -53,7 +53,7 @@
 
 
 def analyze_type_alias(node: Expression,
-                       lookup_func: Callable[[str, Context], SymbolTableNode],
+                       lookup_func: Callable[[str, Context], Optional[SymbolTableNode]],
                        lookup_fqn_func: Callable[[str], SymbolTableNode],
                        tvar_scope: TypeVarScope,
                        fail_func: Callable[[str, Context], None],
@@ -144,7 +144,7 @@ class TypeAnalyser(SyntheticTypeVisitor[Type], AnalyzerPluginInterface):
     global_scope = True  # type: bool
 
     def __init__(self,
-                 lookup_func: Callable[[str, Context], SymbolTableNode],
+                 lookup_func: Callable[[str, Context], Optional[SymbolTableNode]],
                  lookup_fqn_func: Callable[[str], SymbolTableNode],
                  tvar_scope: Optional[TypeVarScope],
                  fail_func: Callable[[str, Context], None],
@@ -555,7 +555,9 @@ def bind_function_type_variables(self,
             return []  # We are in third pass, nothing new here
         if fun_type.variables:
             for var in fun_type.variables:
-                var_expr = self.lookup(var.name, var).node
+                var_node = self.lookup(var.name, var)
+                assert var_node, "Binding for function type variable not found within function"
+                var_expr = var_node.node
                 assert isinstance(var_expr, TypeVarExpr)
                 self.tvar_scope.bind(var.name, var_expr)
             return fun_type.variables
@@ -575,8 +577,12 @@ def bind_function_type_variables(self,
         return defs
 
     def is_defined_type_var(self, tvar: str, context: Context) -> bool:
-        return (self.tvar_scope is not None and
-                self.tvar_scope.get_binding(self.lookup(tvar, context)) is not None)
+        if self.tvar_scope is None:
+            return False
+        tvar_node = self.lookup(tvar, context)
+        if not tvar_node:
+            return False
+        return self.tvar_scope.get_binding(tvar_node) is not None
 
     def anal_array(self, a: List[Type], nested: bool = True) -> List[Type]:
         res = []  # type: List[Type]
@@ -638,7 +644,7 @@ class TypeAnalyserPass3(TypeVisitor[None]):
     """
 
     def __init__(self,
-                 lookup_func: Callable[[str, Context], SymbolTableNode],
+                 lookup_func: Callable[[str, Context], Optional[SymbolTableNode]],
                  lookup_fqn_func: Callable[[str], SymbolTableNode],
                  fail_func: Callable[[str, Context], None],
                  note_func: Callable[[str, Context], None],
@@ -878,7 +884,7 @@ def flatten_tvars(ll: Iterable[List[T]]) -> List[T]:
 class TypeVariableQuery(TypeQuery[TypeVarList]):
 
     def __init__(self,
-                 lookup: Callable[[str, Context], SymbolTableNode],
+                 lookup: Callable[[str, Context], Optional[SymbolTableNode]],
                  scope: 'TypeVarScope',
                  *,
                  include_callables: bool = True,

mypy/types.py

@@ -5,7 +5,7 @@
 from collections import OrderedDict
 from typing import (
     Any, TypeVar, Dict, List, Tuple, cast, Generic, Set, Optional, Union, Iterable, NamedTuple,
-    Callable
+    Callable, Sequence
 )
 
 import mypy.nodes
@@ -646,7 +646,7 @@ class CallableType(FunctionLike):
     def __init__(self,
                  arg_types: List[Type],
                  arg_kinds: List[int],
-                 arg_names: List[Optional[str]],
+                 arg_names: Sequence[Optional[str]],
                  ret_type: Type,
                  fallback: Instance,
                  name: Optional[str] = None,
@@ -667,7 +667,7 @@ def __init__(self,
         assert not any(tp is None for tp in arg_types), "No annotation must be Any, not None"
         self.arg_types = arg_types
         self.arg_kinds = arg_kinds
-        self.arg_names = arg_names
+        self.arg_names = list(arg_names)
         self.min_args = arg_kinds.count(ARG_POS)
         self.is_var_arg = ARG_STAR in arg_kinds
         self.is_kw_arg = ARG_STAR2 in arg_kinds

mypy_self_check.ini

@@ -9,16 +9,6 @@ warn_redundant_casts = True
 warn_unused_ignores = True
 warn_unused_configs = True
 
-# historical exception
-[mypy-mypy.semanal]
-strict_optional = False
-
-[mypy-mypy.semanal_pass1]
-strict_optional = False
-
-[mypy-mypy.semanal_pass3]
-strict_optional = False
-
 # needs py2 compatibility
 [mypy-mypy.test.testextensions]
 disallow_untyped_defs = False

test-data/unit/check-classes.test

@@ -2904,10 +2904,13 @@ class B(object, A): # E: Cannot determine consistent method resolution order (MR
     __iter__ = readlines
 
 [case testDynamicMetaclass]
-
 class C(metaclass=int()):  # E: Dynamic metaclass not supported for 'C'
     pass
 
+[case testDynamicMetaclassCrash]
+class C(metaclass=int().x):  # E: Dynamic metaclass not supported for 'C'
+    pass
+
 [case testVariableSubclass]
 class A:
     a = 1  # type: int