def solve_constraints( vars, constraints, basic):
"""Solve type constraints.
Return lower bound for each type variable or None if the variable could
not be solved.
"""
# Collect a list of constraints for each type variable.
cmap = {}
for con in constraints:
a = cmap.get(con.type_var, [])
a.append(con)
cmap[con.type_var] = a
res = []
# Solve each type variable separately.
for tvar in vars:
bottom = None
top = None
# Process each contraint separely, and calculate the lower and upper
# bounds based on constraints. Note that we assume that the contraint
# targets do not have contraint references.
for c in cmap.get(tvar, []):
if c.op == SUPERTYPE_OF:
if bottom is None:
bottom = c.target
else:
bottom = join_types(bottom, c.target, basic)
else:
if top is None:
top = c.target
else:
top = meet_types(top, c.target, basic)
if top is None:
if isinstance(bottom, Void):
top = Void()
else:
top = basic.object
if bottom is None:
if isinstance(top, Void):
bottom = Void()
else:
bottom = NoneTyp()
if isinstance(top, Any) or isinstance(bottom, Any):
top = Any()
bottom = Any()
# Pick the most specific type if it satisfies the constraints.
if (not top or not bottom or is_subtype(bottom, top)) and (
not isinstance(top, ErrorType) and
not isinstance(bottom, ErrorType)):
res.append(bottom)
else:
res.append(None)
return res
def assert_simple_meet(self, s, t, meet):
result = meet_types(s, t, self.fx.basic)
actual = str(result)
expected = str(meet)
assert_equal(actual, expected,
'meet({}, {}) == {{}} ({{}} expected)'.format(s, t))
if not isinstance(s, ErrorType) and not isinstance(result, ErrorType):
assert_true(is_subtype(result, s),
'{} not subtype of {}'.format(result, s))
if not isinstance(t, ErrorType) and not isinstance(result, ErrorType):
assert_true(is_subtype(result, t),
'{} not subtype of {}'.format(result, t))
Typ top = None
# Process each contraint separely, and calculate the lower and upper
# bounds based on constraints. Note that we assume that the contraint
# targets do not have contraint references.
for c in cmap.get(tvar, []):
if c.op == SUPERTYPE_OF:
if bottom is None:
bottom = c.target
else:
bottom = join_types(bottom, c.target, basic)
else:
if top is None:
top = c.target
else:
top = meet_types(top, c.target, basic)
if top is None:
if isinstance(bottom, Void):
top = Void()
else:
top = basic.object
if bottom is None:
if isinstance(top, Void):
bottom = Void()
else:
bottom = NoneTyp()
if isinstance(top, Any) or isinstance(bottom, Any):
top = Any()
