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# Nodes for structural pattern matching.
#
# In a separate file because they're unlikely to be useful for much else.
from .Nodes import Node, StatNode
from .Errors import error
class MatchNode(StatNode):
"""
subject ExprNode The expression to be matched
cases [MatchCaseNode] list of cases
"""
child_attrs = ["subject", "cases"]
def validate_irrefutable(self):
found_irrefutable_case = None
for c in self.cases:
if found_irrefutable_case:
error(
found_irrefutable_case.pos,
(
"%s makes remaining patterns unreachable"
% found_irrefutable_case.pattern.irrefutable_message()
),
)
break
if c.is_irrefutable():
found_irrefutable_case = c
c.validate_irrefutable()
def analyse_expressions(self, env):
error(self.pos, "Structural pattern match is not yet implemented")
return self
class MatchCaseNode(Node):
"""
pattern PatternNode
body StatListNode
guard ExprNode or None
"""
child_attrs = ["pattern", "body", "guard"]
def is_irrefutable(self):
return self.pattern.is_irrefutable() and not self.guard
def validate_targets(self):
self.pattern.get_targets()
def validate_irrefutable(self):
self.pattern.validate_irrefutable()
class PatternNode(Node):
"""
DW decided that PatternNode shouldn't be an expression because
it does several things (evalutating a boolean expression,
assignment of targets), and they need to be done at different
times.
as_targets [NameNode] any target assign by "as"
"""
child_attrs = ["as_targets"]
def __init__(self, pos, **kwds):
super(PatternNode, self).__init__(pos, **kwds)
if "as_targets" not in kwds:
self.as_targets = []
def is_irrefutable(self):
return False
def get_targets(self):
targets = self.get_main_pattern_targets()
for t in self.as_targets:
self.add_target_to_targets(targets, t.name)
return targets
def update_targets_with_targets(self, targets, other_targets):
intersection = targets.intersection(other_targets)
for i in intersection:
error(self.pos, "multiple assignments to name '%s' in pattern" % i)
targets.update(other_targets)
def add_target_to_targets(self, targets, target):
if target in targets:
error(self.pos, "multiple assignments to name '%s in pattern" % target)
targets.add(target)
def get_main_pattern_targets(self):
# exclude "as" target
raise NotImplementedError
def validate_irrefutable(self):
for attr in self.child_attrs:
child = getattr(self, attr)
if isinstance(child, PatternNode):
child.validate_irrefutable()
class MatchValuePatternNode(PatternNode):
"""
value ExprNode # todo be more specific
is_is_check bool Picks "is" or equality check
"""
child_attrs = PatternNode.child_attrs + ["value"]
is_is_check = False
def get_main_pattern_targets(self):
return set()
class MatchAndAssignPatternNode(PatternNode):
"""
target NameNode or None the target to assign to (None = wildcard)
is_star bool
"""
target = None
is_star = False
child_atts = PatternNode.child_attrs + ["target"]
def is_irrefutable(self):
return not self.is_star
def irrefutable_message(self):
if self.target:
return "name capture '%s'" % self.target.name
else:
return "wildcard"
def get_main_pattern_targets(self):
if self.target:
return {self.target.name}
else:
return set()
class OrPatternNode(PatternNode):
"""
alternatives list of PatternNodes
"""
child_attrs = PatternNode.child_attrs + ["alternatives"]
def get_first_irrefutable(self):
for a in self.alternatives:
if a.is_irrefutable():
return a
return None
def is_irrefutable(self):
return self.get_first_irrefutable() is not None
def irrefutable_message(self):
return self.get_first_irrefutable().irrefutable_message()
def get_main_pattern_targets(self):
child_targets = None
for ch in self.alternatives:
ch_targets = ch.get_targets()
if child_targets is not None and child_targets != ch_targets:
error(self.pos, "alternative patterns bind different names")
child_targets = ch_targets
return child_targets
def validate_irrefutable(self):
super(OrPatternNode, self).validate_irrefutable()
found_irrefutable_case = None
for a in self.alternatives:
if found_irrefutable_case:
error(
found_irrefutable_case.pos,
(
"%s makes remaining patterns unreachable"
% found_irrefutable_case.irrefutable_message()
),
)
break
if a.is_irrefutable():
found_irrefutable_case = a
a.validate_irrefutable()
class MatchSequencePatternNode(PatternNode):
"""
patterns list of PatternNodes
"""
child_attrs = PatternNode.child_attrs + ["patterns"]
def get_main_pattern_targets(self):
targets = set()
for p in self.patterns:
self.update_targets_with_targets(targets, p.get_targets())
return targets
class MatchMappingPatternNode(PatternNode):
"""
keys list of NameNodes
value_patterns list of PatternNodes of equal length to keys
double_star_capture_target NameNode or None
"""
keys = []
value_patterns = []
double_star_capture_target = None
child_attrs = PatternNode.child_attrs + [
"keys",
"value_patterns",
"double_star_capture_target",
]
def get_main_pattern_targets(self):
targets = set()
for p in self.value_patterns:
self.update_targets_with_targets(targets, p.get_targets())
if self.double_star_capture_target:
self.add_target_to_targets(targets, self.double_star_capture_target.name)
return targets
class ClassPatternNode(PatternNode):
"""
class_ NameNode or AttributeNode
positional_patterns list of PatternNodes
keyword_pattern_names list of NameNodes
keyword_pattern_patterns list of PatternNodes
(same length as keyword_pattern_names)
"""
class_ = None
positional_patterns = []
keyword_pattern_names = []
keyword_pattern_patterns = []
child_attrs = PatternNode.child_attrs + [
"class_",
"positional_patterns",
"keyword_pattern_names",
"keyword_pattern_patterns",
]
def get_main_pattern_targets(self):
targets = set()
for p in self.positional_patterns + self.keyword_pattern_patterns:
self.update_targets_with_targets(targets, p.get_targets())
return targets
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