narrow to literal value

Author: KotlinIsland

CHANGELOG.md

@@ -1,6 +1,10 @@
 # Basedmypy Changelog
 
 ## [Unreleased]
+### Added
+- `float` and `complex` literals
+- narrow types to literal values
+- infer literal in generics
 
 ## [2.9.0]
 ### Added

mypy/binder.py

@@ -5,7 +5,6 @@
 from typing import DefaultDict, Generator, Iterator, List, NamedTuple, Optional, Tuple, Union
 from typing_extensions import TypeAlias as _TypeAlias
 
-from mypy.erasetype import remove_instance_last_known_values
 from mypy.join import join_simple
 from mypy.literals import Key, literal, literal_hash, subkeys
 from mypy.nodes import Expression, IndexExpr, MemberExpr, NameExpr, RefExpr, TypeInfo, Var
@@ -331,7 +330,8 @@ def assign_type(
     ) -> None:
         # We should erase last known value in binder, because if we are using it,
         # it means that the target is not final, and therefore can't hold a literal.
-        type = remove_instance_last_known_values(type)
+        # HUUHHH?????
+        # type = remove_instance_last_known_values(type)
 
         if self.type_assignments is not None:
             # We are in a multiassign from union, defer the actual binding,

mypy/checker.py

@@ -3589,19 +3589,30 @@ def check_assignment(
                         ):
                             lvalue.node.type = remove_instance_last_known_values(lvalue_type)
 
+                elif lvalue.node and lvalue.node.is_inferred and rvalue_type:
+                    # for literal values
+                    # Don't use type binder for definitions of special forms, like named tuples.
+                    if not (isinstance(lvalue, NameExpr) and lvalue.is_special_form):
+                        self.binder.assign_type(lvalue, rvalue_type, lvalue_type, False)
+
             elif index_lvalue:
                 self.check_indexed_assignment(index_lvalue, rvalue, lvalue)
 
             if inferred:
                 type_context = self.get_variable_type_context(inferred)
                 rvalue_type = self.expr_checker.accept(rvalue, type_context=type_context)
+                original_rvalue_type = rvalue_type
                 if not (
                     inferred.is_final
                     or inferred.is_index_var
                     or (isinstance(lvalue, NameExpr) and lvalue.name == "__match_args__")
                 ):
                     rvalue_type = remove_instance_last_known_values(rvalue_type)
-                self.infer_variable_type(inferred, lvalue, rvalue_type, rvalue)
+                if self.infer_variable_type(inferred, lvalue, rvalue_type, rvalue) or self.binder.type_assignments:
+                    # we don't always want to assign the type here as it might be something like partial
+                    self.binder.assign_type(
+                        lvalue, original_rvalue_type, original_rvalue_type, False
+                    )
             self.check_assignment_to_slots(lvalue)
 
     # (type, operator) tuples for augmented assignments supported with partial types
@@ -4553,12 +4564,13 @@ def is_definition(self, s: Lvalue) -> bool:
 
     def infer_variable_type(
         self, name: Var, lvalue: Lvalue, init_type: Type, context: Context
-    ) -> None:
+    ) -> bool:
         """Infer the type of initialized variables from initializer type."""
+        valid = True
         if isinstance(init_type, DeletedType):
             self.msg.deleted_as_rvalue(init_type, context)
         elif (
-            not is_valid_inferred_type(init_type, is_lvalue_final=name.is_final)
+            not (valid := is_valid_inferred_type(init_type, is_lvalue_final=name.is_final))
             and not self.no_partial_types
         ):
             # We cannot use the type of the initialization expression for full type
@@ -4585,6 +4597,7 @@ def infer_variable_type(
             init_type = strip_type(init_type)
 
             self.set_inferred_type(name, lvalue, init_type)
+        return valid
 
     def infer_partial_type(self, name: Var, lvalue: Lvalue, init_type: Type) -> bool:
         init_type = get_proper_type(init_type)

mypy/checkexpr.py

@@ -210,7 +210,8 @@
 # Type of callback user for checking individual function arguments. See
 # check_args() below for details.
 ArgChecker: _TypeAlias = Callable[
-    [Type, Type, ArgKind, Type, int, int, CallableType, Optional[Type], Context, Context], None
+    [Type, Type, ArgKind, Type, int, int, CallableType, Optional[Type], Context, Context, bool],
+    None,
 ]
 
 # Maximum nesting level for math union in overloads, setting this to large values
@@ -2175,6 +2176,13 @@ def infer_function_type_arguments(
         Return a derived callable type that has the arguments applied.
         """
         if self.chk.in_checked_function():
+            if isinstance(callee_type.ret_type, TypeVarType):
+                # if the return type is constant, infer as literal
+                rvalue_type = [
+                    remove_instance_last_known_values(arg) if isinstance(arg, Instance) else arg
+                    for arg in args
+                ]
+
             # Disable type errors during type inference. There may be errors
             # due to partial available context information at this time, but
             # these errors can be safely ignored as the arguments will be
@@ -2581,6 +2589,8 @@ def check_argument_types(
         context: Context,
         check_arg: ArgChecker | None = None,
         object_type: Type | None = None,
+        *,
+        type_function=False,
     ) -> None:
         """Check argument types against a callable type.
 
@@ -2712,6 +2722,7 @@ def check_argument_types(
                     object_type,
                     args[actual],
                     context,
+                    type_function,
                 )
 
     def check_arg(
@@ -2726,12 +2737,16 @@ def check_arg(
         object_type: Type | None,
         context: Context,
         outer_context: Context,
+        type_function=False,
     ) -> None:
         """Check the type of a single argument in a call."""
         caller_type = get_proper_type(caller_type)
         original_caller_type = get_proper_type(original_caller_type)
         callee_type = get_proper_type(callee_type)
-
+        if type_function:
+            # TODO: make this work at all
+            if not isinstance(caller_type, Instance) or not caller_type.last_known_value:
+                caller_type = self.named_type("builtins.object")
         if isinstance(caller_type, DeletedType):
             self.msg.deleted_as_rvalue(caller_type, context)
         # Only non-abstract non-protocol class can be given where Type[...] is expected...
@@ -3348,6 +3363,7 @@ def check_arg(
             object_type: Type | None,
             context: Context,
             outer_context: Context,
+            type_function: bool,
         ) -> None:
             if not arg_approximate_similarity(caller_type, callee_type):
                 # No match -- exit early since none of the remaining work can change
@@ -3580,10 +3596,14 @@ def visit_bytes_expr(self, e: BytesExpr) -> Type:
 
     def visit_float_expr(self, e: FloatExpr) -> Type:
         """Type check a float literal (trivial)."""
+        if mypy.options._based:
+            return self.infer_literal_expr_type(e.value, "builtins.float")
         return self.named_type("builtins.float")
 
     def visit_complex_expr(self, e: ComplexExpr) -> Type:
         """Type check a complex literal."""
+        if mypy.options._based:
+            return self.infer_literal_expr_type(e.value, "builtins.complex")
         return self.named_type("builtins.complex")
 
     def visit_ellipsis(self, e: EllipsisExpr) -> Type:

mypy/expandtype.py

@@ -1,5 +1,6 @@
 from __future__ import annotations
 
+from contextlib import contextmanager
 from typing import Final, Iterable, Mapping, Sequence, TypeVar, cast, overload
 
 from mypy.nodes import ARG_STAR, FakeInfo, Var
@@ -185,6 +186,16 @@ def __init__(self, variables: Mapping[TypeVarId, Type]) -> None:
         super().__init__()
         self.variables = variables
         self.recursive_tvar_guard: dict[TypeVarId, Type | None] = {}
+        self._erase_literals = False
+
+    @contextmanager
+    def erase_literals(self):
+        _erase_literals = self._erase_literals
+        self._erase_literals = True
+        try:
+            yield
+        finally:
+            self._erase_literals = _erase_literals
 
     def visit_unbound_type(self, t: UnboundType) -> Type:
         return t
@@ -211,7 +222,8 @@ def visit_erased_type(self, t: ErasedType) -> Type:
         return t
 
     def visit_instance(self, t: Instance) -> Type:
-        args = self.expand_types_with_unpack(list(t.args))
+        with self.erase_literals():
+            args = self.expand_types_with_unpack(list(t.args))
 
         if isinstance(t.type, FakeInfo):
             # The type checker expands function definitions and bodies
@@ -238,7 +250,7 @@ def visit_type_var(self, t: TypeVarType) -> Type:
         if t.id.is_self():
             t = t.copy_modified(upper_bound=t.upper_bound.accept(self))
         repl = self.variables.get(t.id, t)
-        if isinstance(repl, ProperType) and isinstance(repl, Instance):
+        if self._erase_literals and isinstance(repl, ProperType) and isinstance(repl, Instance):
             # TODO: do we really need to do this?
             # If I try to remove this special-casing ~40 tests fail on reveal_type().
             return repl.copy_modified(last_known_value=None)
@@ -410,17 +422,18 @@ def visit_callable_type(self, t: CallableType) -> CallableType:
 
         var_arg = t.var_arg()
         needs_normalization = False
-        if var_arg is not None and isinstance(var_arg.typ, UnpackType):
-            needs_normalization = True
-            arg_types = self.interpolate_args_for_unpack(t, var_arg.typ)
-        else:
-            arg_types = self.expand_types(t.arg_types)
-        expanded = t.copy_modified(
-            arg_types=arg_types,
-            ret_type=t.ret_type.accept(self),
-            type_guard=t.type_guard and cast(TypeGuardType, t.type_guard.accept(self)),
-            type_is=(t.type_is.accept(self) if t.type_is is not None else None),
-        )
+        with self.erase_literals():
+            if var_arg is not None and isinstance(var_arg.typ, UnpackType):
+                needs_normalization = True
+                arg_types = self.interpolate_args_for_unpack(t, var_arg.typ)
+            else:
+                arg_types = self.expand_types(t.arg_types)
+            expanded = t.copy_modified(
+                arg_types=arg_types,
+                ret_type=t.ret_type.accept(self),
+                type_guard=t.type_guard and cast(TypeGuardType, t.type_guard.accept(self)),
+                type_is=(t.type_is.accept(self) if t.type_is is not None else None),
+            )
         if needs_normalization:
             return expanded.with_normalized_var_args()
         return expanded
@@ -467,7 +480,9 @@ def visit_typeddict_type(self, t: TypedDictType) -> Type:
             return cached
         fallback = t.fallback.accept(self)
         assert isinstance(fallback, ProperType) and isinstance(fallback, Instance)
-        result = t.copy_modified(item_types=self.expand_types(t.items.values()), fallback=fallback)
+        with self.erase_literals():
+            # TODO: we don't want to erase literals for `ReadOnly` keys
+            result = t.copy_modified(item_types=self.expand_types(t.items.values()), fallback=fallback)
         self.set_cached(t, result)
         return result
 

mypy/fastparse.py

@@ -2129,7 +2129,8 @@ def numeric_type(self, value: object, n: AST) -> Type:
             # Other kinds of numbers (floats, complex) are not valid parameters for
             # RawExpressionType so we just pass in 'None' for now. We'll report the
             # appropriate error at a later stage.
-            numeric_value = None
+            # based: they are valid
+            numeric_value = value
             type_name = f"builtins.{type(value).__name__}"
         return RawExpressionType(
             numeric_value, type_name, line=self.line, column=getattr(n, "col_offset", -1)

mypy/join.py

@@ -232,7 +232,7 @@ def join_simple(declaration: Type | None, s: Type, t: Type) -> ProperType:
     if declaration is None or is_subtype(value, declaration):
         return value
 
-    return declaration
+    return value
 
 
 def trivial_join(s: Type, t: Type) -> Type:

mypy/meet.py

@@ -197,9 +197,12 @@ def narrow_declared_type(declared: Type, narrowed: Type) -> Type:
             # Special case: 'int' can't be narrowed down to a native int type such as
             # i64, since they have different runtime representations.
             return original_declared
+        if isinstance(narrowed, Instance) and narrowed.last_known_value:
+            return narrowed
         return meet_types(original_declared, original_narrowed)
     elif isinstance(declared, (TupleType, TypeType, LiteralType)):
-        return meet_types(original_declared, original_narrowed)
+        # this way around to preserve the last know of the items in the tuple
+        return meet_types(original_narrowed, original_declared, intersect=True)
     elif isinstance(declared, TypedDictType) and isinstance(narrowed, Instance):
         # Special case useful for selecting TypedDicts from unions using isinstance(x, dict).
         if narrowed.type.fullname == "builtins.dict" and all(

mypy/test/testtypes.py

@@ -694,8 +694,14 @@ def test_simplified_intersection(self):
             [fx.b, IntersectionType([fx.c, IntersectionType([fx.d])])],
             IntersectionType([fx.b, fx.c, fx.d]),
         )
+        self.assert_simplified_intersection([fx.bool_type, fx.lit_true], fx.lit_true)
+
+        # special case: it's not currently symmetric when there are last known values
+        narrowed = fx.bool_type.copy_modified(last_known_value=fx.lit_true)
+        assert_equal(make_simplified_intersection([narrowed, fx.bool_type]), narrowed)
 
     def assert_simplified_intersection(self, original: list[Type], intersection: Type) -> None:
+        __tracebackhide__ = True
         assert_equal(make_simplified_intersection(original), intersection)
         assert_equal(make_simplified_intersection(list(reversed(original))), intersection)
 

mypy/typeanal.py

@@ -527,7 +527,6 @@ def visit_unbound_type_nonoptional(self, t: UnboundType, defining_literal: bool)
                 return res
             elif isinstance(node, TypeInfo):
                 return self.analyze_type_with_type_info(node, t.args, t, t.empty_tuple_index)
-
             elif node.fullname in TYPE_ALIAS_NAMES:
                 return AnyType(TypeOfAny.special_form)
             # Concatenate is an operator, no need for a proper type
@@ -1432,7 +1431,11 @@ def visit_raw_expression_type(self, t: RawExpressionType) -> Type:
 
         if self.report_invalid_types:
             msg = None
-            if t.base_type_name in ("builtins.int", "builtins.bool"):
+            if (
+                t.base_type_name in ("builtins.int", "builtins.bool")
+                or mypy.options._based
+                and t.base_type_name in ("builtins.float", "builtins.complex")
+            ):
                 if not self.options.bare_literals:
                     # The only time it makes sense to use an int or bool is inside of
                     # a literal type.
@@ -1453,7 +1456,12 @@ def visit_raw_expression_type(self, t: RawExpressionType) -> Type:
                 self.fail(msg, t, code=codes.VALID_TYPE)
                 if t.note is not None:
                     self.note(t.note, t, code=codes.VALID_TYPE)
-        if t.base_type_name in ("builtins.int", "builtins.bool"):
+        if t.base_type_name in (
+            "builtins.int",
+            "builtins.bool",
+            "builtins.float",
+            "builtins.complex",
+        ):
             v = t.literal_value
             assert v is not None
             result = LiteralType(