def join_types(s: Type, t: Type) -> Type:
"""Return the least upper bound of s and t.
For example, the join of 'int' and 'object' is 'object'.
"""
if (s.can_be_true, s.can_be_false) != (t.can_be_true, t.can_be_false):
# if types are restricted in different ways, use the more general versions
s = true_or_false(s)
t = true_or_false(t)
if isinstance(s, AnyType):
return s
if isinstance(s, ErasedType):
return t
if isinstance(s, UnionType) and not isinstance(t, UnionType):
s, t = t, s
if isinstance(s, NoneTyp) and not isinstance(t, NoneTyp):
s, t = t, s
if isinstance(s, UninhabitedType) and not isinstance(t, UninhabitedType):
s, t = t, s
# Use a visitor to handle non-trivial cases.
return t.accept(TypeJoinVisitor(s))
def join_simple(declaration: Optional[Type], s: Type, t: Type) -> Type:
"""Return a simple least upper bound given the declared type."""
if (s.can_be_true, s.can_be_false) != (t.can_be_true, t.can_be_false):
# if types are restricted in different ways, use the more general versions
s = true_or_false(s)
t = true_or_false(t)
if isinstance(s, AnyType):
return s
if isinstance(s, ErasedType):
return t
if is_proper_subtype(s, t):
return t
if is_proper_subtype(t, s):
return s
if isinstance(declaration, UnionType):
return UnionType.make_simplified_union([s, t])
if isinstance(s, NoneTyp) and not isinstance(t, NoneTyp):
s, t = t, s
if isinstance(s, UninhabitedType) and not isinstance(t, UninhabitedType):
s, t = t, s
value = t.accept(TypeJoinVisitor(s))
if value is None:
# XXX this code path probably should be avoided.
# It seems to happen when a line (x = y) is a type error, and
# it's not clear that assuming that x is arbitrary afterward
# is a good idea.
return declaration
if declaration is None or is_subtype(value, declaration):
return value
return declaration
def join_simple(declaration: Optional[Type], s: Type, t: Type) -> Type:
"""Return a simple least upper bound given the declared type."""
if (s.can_be_true, s.can_be_false) != (t.can_be_true, t.can_be_false):
# if types are restricted in different ways, use the more general versions
s = true_or_false(s)
t = true_or_false(t)
if isinstance(s, AnyType):
return s
if isinstance(s, ErasedType):
return t
if is_proper_subtype(s, t):
return t
if is_proper_subtype(t, s):
return s
if isinstance(declaration, UnionType):
return UnionType.make_simplified_union([s, t])
if isinstance(s, NoneTyp) and not isinstance(t, NoneTyp):
s, t = t, s
if isinstance(s, UninhabitedType) and not isinstance(t, UninhabitedType):
s, t = t, s
value = t.accept(TypeJoinVisitor(s))
if value is None:
# XXX this code path probably should be avoided.
# It seems to happen when a line (x = y) is a type error, and
# it's not clear that assuming that x is arbitrary afterward
# is a good idea.
return declaration
if declaration is None or is_subtype(value, declaration):
return value
return declaration
def join_simple(declaration: Optional[Type], s: Type, t: Type) -> ProperType:
"""Return a simple least upper bound given the declared type."""
declaration = get_proper_type(declaration)
s = get_proper_type(s)
t = get_proper_type(t)
if (s.can_be_true, s.can_be_false) != (t.can_be_true, t.can_be_false):
# if types are restricted in different ways, use the more general versions
s = true_or_false(s)
t = true_or_false(t)
if isinstance(s, AnyType):
return s
if isinstance(s, ErasedType):
return t
if is_proper_subtype(s, t):
return t
if is_proper_subtype(t, s):
return s
if isinstance(declaration, UnionType):
return UnionType.make_simplified_union([s, t])
if isinstance(s, NoneType) and not isinstance(t, NoneType):
s, t = t, s
if isinstance(s, UninhabitedType) and not isinstance(t, UninhabitedType):
s, t = t, s
value = t.accept(TypeJoinVisitor(s))
if declaration is None or is_subtype(value, declaration):
return value
return declaration
