| 1 | """
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| 2 | control_flow_pass.py - AST pass that builds a control flow graph.
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| 3 | """
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| 4 | import collections
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| 5 | from typing import overload, Union, Optional, Dict
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| 6 |
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| 7 | import mypy
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| 8 | from mypy.nodes import (Block, Expression, Statement, ExpressionStmt, StrExpr,
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| 9 | CallExpr, FuncDef, IfStmt, NameExpr, MemberExpr)
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| 10 |
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| 11 | from mypy.types import CallableType, Instance, Type, UnionType
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| 12 |
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| 13 | from mycpp.crash import catch_errors
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| 14 | from mycpp.util import join_name, split_py_name
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| 15 | from mycpp.visitor import SimpleVisitor, T
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| 16 | from mycpp import util
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| 17 | from mycpp import pass_state
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| 18 |
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| 19 |
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| 20 | class UnsupportedException(Exception):
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| 21 | pass
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| 22 |
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| 23 |
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| 24 | class Build(SimpleVisitor):
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| 25 |
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| 26 | def __init__(self, types: Dict[Expression, Type], virtual, local_vars,
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| 27 | dot_exprs):
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| 28 |
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| 29 | self.types = types
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| 30 | self.cfgs = collections.defaultdict(pass_state.ControlFlowGraph)
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| 31 | self.current_statement_id = None
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| 32 | self.current_class_name = None
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| 33 | self.current_func_node = None
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| 34 | self.loop_stack = []
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| 35 | self.virtual = virtual
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| 36 | self.local_vars = local_vars
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| 37 | self.dot_exprs = dot_exprs
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| 38 | self.callees = {} # statement object -> SymbolPath of the callee
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| 39 |
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| 40 | def current_cfg(self):
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| 41 | if not self.current_func_node:
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| 42 | return None
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| 43 |
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| 44 | return self.cfgs[split_py_name(self.current_func_node.fullname)]
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| 45 |
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| 46 | def resolve_callee(self, o: CallExpr) -> Optional[util.SymbolPath]:
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| 47 | """
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| 48 | Returns the fully qualified name of the callee in the given call
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| 49 | expression.
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| 50 |
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| 51 | Member functions are prefixed by the names of the classes that contain
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| 52 | them. For example, the name of the callee in the last statement of the
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| 53 | snippet below is `module.SomeObject.Foo`.
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| 54 |
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| 55 | x = module.SomeObject()
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| 56 | x.Foo()
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| 57 |
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| 58 | Free-functions defined in the local module are referred to by their
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| 59 | normal fully qualified names. The function `foo` in a module called
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| 60 | `moduleA` would is named `moduleA.foo`. Calls to free-functions defined
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| 61 | in imported modules are named the same way.
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| 62 | """
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| 63 |
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| 64 | if isinstance(o.callee, NameExpr):
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| 65 | return split_py_name(o.callee.fullname)
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| 66 |
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| 67 | elif isinstance(o.callee, MemberExpr):
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| 68 | if isinstance(o.callee.expr, NameExpr):
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| 69 | is_module = isinstance(self.dot_exprs.get(o.callee),
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| 70 | pass_state.ModuleMember)
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| 71 | if is_module:
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| 72 | return split_py_name(
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| 73 | o.callee.expr.fullname) + (o.callee.name, )
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| 74 |
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| 75 | elif o.callee.expr.name == 'self':
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| 76 | assert self.current_class_name
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| 77 | return self.current_class_name + (o.callee.name, )
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| 78 |
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| 79 | else:
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| 80 | local_type = None
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| 81 | for name, t in self.local_vars.get(self.current_func_node,
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| 82 | []):
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| 83 | if name == o.callee.expr.name:
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| 84 | local_type = t
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| 85 | break
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| 86 |
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| 87 | if local_type:
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| 88 | if isinstance(local_type, str):
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| 89 | return split_py_name(local_type) + (
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| 90 | o.callee.name, )
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| 91 |
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| 92 | elif isinstance(local_type, Instance):
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| 93 | return split_py_name(
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| 94 | local_type.type.fullname) + (o.callee.name, )
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| 95 |
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| 96 | elif isinstance(local_type, UnionType):
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| 97 | assert len(local_type.items) == 2
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| 98 | return split_py_name(
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| 99 | local_type.items[0].type.fullname) + (
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| 100 | o.callee.expr.name, )
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| 101 |
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| 102 | else:
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| 103 | assert not isinstance(local_type, CallableType)
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| 104 | # primitive type or string. don't care.
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| 105 | return None
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| 106 |
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| 107 | else:
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| 108 | # context or exception handler. probably safe to ignore.
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| 109 | return None
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| 110 |
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| 111 | else:
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| 112 | t = self.types.get(o.callee.expr)
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| 113 | if isinstance(t, Instance):
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| 114 | return split_py_name(t.type.fullname) + (o.callee.name, )
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| 115 |
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| 116 | elif isinstance(t, UnionType):
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| 117 | assert len(t.items) == 2
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| 118 | return split_py_name(
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| 119 | t.items[0].type.fullname) + (o.callee.name, )
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| 120 |
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| 121 | elif o.callee.expr and getattr(o.callee.expr, 'fullname',
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| 122 | None):
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| 123 | return split_py_name(
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| 124 | o.callee.expr.fullname) + (o.callee.name, )
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| 125 |
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| 126 | else:
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| 127 | # constructors of things that we don't care about.
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| 128 | return None
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| 129 |
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| 130 | # Don't currently get here
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| 131 | raise AssertionError()
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| 132 |
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| 133 | #
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| 134 | # COPIED from IRBuilder
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| 135 | #
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| 136 |
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| 137 | @overload
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| 138 | def accept(self, node: Expression) -> T:
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| 139 | ...
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| 140 |
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| 141 | @overload
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| 142 | def accept(self, node: Statement) -> None:
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| 143 | ...
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| 144 |
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| 145 | def accept(self, node: Union[Statement, Expression]) -> Optional[T]:
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| 146 | with catch_errors(self.module_path, node.line):
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| 147 | if isinstance(node, Expression):
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| 148 | try:
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| 149 | res = node.accept(self)
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| 150 | #res = self.coerce(res, self.node_type(node), node.line)
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| 151 |
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| 152 | # If we hit an error during compilation, we want to
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| 153 | # keep trying, so we can produce more error
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| 154 | # messages. Generate a temp of the right type to keep
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| 155 | # from causing more downstream trouble.
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| 156 | except UnsupportedException:
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| 157 | res = self.alloc_temp(self.node_type(node))
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| 158 | return res
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| 159 | else:
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| 160 | try:
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| 161 | cfg = self.current_cfg()
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| 162 | # Most statements have empty visitors because they don't
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| 163 | # require any special logic. Create statements for them
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| 164 | # here. Don't create statements from blocks to avoid
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| 165 | # stuttering.
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| 166 | if cfg and not isinstance(node, Block):
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| 167 | self.current_statement_id = cfg.AddStatement()
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| 168 |
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| 169 | node.accept(self)
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| 170 | except UnsupportedException:
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| 171 | pass
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| 172 | return None
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| 173 |
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| 174 | # Not in superclasses:
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| 175 |
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| 176 | def visit_mypy_file(self, o: 'mypy.nodes.MypyFile') -> T:
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| 177 | if util.ShouldSkipPyFile(o):
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| 178 | return
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| 179 |
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| 180 | self.module_path = o.path
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| 181 |
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| 182 | for node in o.defs:
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| 183 | # skip module docstring
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| 184 | if isinstance(node, ExpressionStmt) and isinstance(
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| 185 | node.expr, StrExpr):
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| 186 | continue
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| 187 | self.accept(node)
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| 188 |
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| 189 | # Statements
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| 190 |
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| 191 | def visit_for_stmt(self, o: 'mypy.nodes.ForStmt') -> T:
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| 192 | cfg = self.current_cfg()
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| 193 | with pass_state.CfgLoopContext(
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| 194 | cfg, entry=self.current_statement_id) as loop:
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| 195 | self.accept(o.expr)
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| 196 | self.loop_stack.append(loop)
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| 197 | self.accept(o.body)
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| 198 | self.loop_stack.pop()
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| 199 |
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| 200 | def _handle_switch(self, expr, o, cfg):
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| 201 | assert len(o.body.body) == 1, o.body.body
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| 202 | if_node = o.body.body[0]
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| 203 | assert isinstance(if_node, IfStmt), if_node
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| 204 | cases = []
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| 205 | default_block = util._collect_cases(self.module_path, if_node, cases)
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| 206 | with pass_state.CfgBranchContext(
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| 207 | cfg, self.current_statement_id) as branch_ctx:
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| 208 | for expr, body in cases:
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| 209 | self.accept(expr)
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| 210 | assert expr is not None, expr
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| 211 | with branch_ctx.AddBranch():
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| 212 | self.accept(body)
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| 213 |
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| 214 | if default_block:
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| 215 | with branch_ctx.AddBranch():
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| 216 | self.accept(default_block)
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| 217 |
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| 218 | def visit_with_stmt(self, o: 'mypy.nodes.WithStmt') -> T:
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| 219 | cfg = self.current_cfg()
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| 220 | assert len(o.expr) == 1, o.expr
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| 221 | expr = o.expr[0]
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| 222 | assert isinstance(expr, CallExpr), expr
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| 223 | self.accept(expr)
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| 224 |
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| 225 | callee_name = expr.callee.name
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| 226 | if callee_name == 'switch':
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| 227 | self._handle_switch(expr, o, cfg)
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| 228 | elif callee_name == 'str_switch':
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| 229 | self._handle_switch(expr, o, cfg)
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| 230 | elif callee_name == 'tagswitch':
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| 231 | self._handle_switch(expr, o, cfg)
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| 232 | else:
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| 233 | with pass_state.CfgBlockContext(cfg, self.current_statement_id):
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| 234 | self.accept(o.body)
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| 235 |
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| 236 | def visit_func_def(self, o: 'mypy.nodes.FuncDef') -> T:
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| 237 | if o.name == '__repr__': # Don't translate
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| 238 | return
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| 239 |
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| 240 | # For virtual methods, pretend that the method on the base class calls
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| 241 | # the same method on every subclass. This way call sites using the
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| 242 | # abstract base class will over-approximate the set of call paths they
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| 243 | # can take when checking if they can reach MaybeCollect().
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| 244 | if self.current_class_name and self.virtual.IsVirtual(
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| 245 | self.current_class_name, o.name):
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| 246 | key = (self.current_class_name, o.name)
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| 247 | base = self.virtual.virtuals[key]
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| 248 | if base:
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| 249 | sub = join_name(self.current_class_name + (o.name, ),
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| 250 | delim='.')
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| 251 | base_key = base[0] + (base[1], )
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| 252 | cfg = self.cfgs[base_key]
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| 253 | cfg.AddFact(0, pass_state.FunctionCall(sub))
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| 254 |
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| 255 | self.current_func_node = o
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| 256 | self.accept(o.body)
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| 257 | self.current_func_node = None
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| 258 | self.current_statement_id = None
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| 259 |
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| 260 | def visit_class_def(self, o: 'mypy.nodes.ClassDef') -> T:
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| 261 | self.current_class_name = split_py_name(o.fullname)
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| 262 | for stmt in o.defs.body:
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| 263 | # Ignore things that look like docstrings
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| 264 | if (isinstance(stmt, ExpressionStmt) and
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| 265 | isinstance(stmt.expr, StrExpr)):
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| 266 | continue
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| 267 |
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| 268 | if isinstance(stmt, FuncDef) and stmt.name == '__repr__':
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| 269 | continue
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| 270 |
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| 271 | self.accept(stmt)
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| 272 |
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| 273 | self.current_class_name = None
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| 274 |
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| 275 | def visit_while_stmt(self, o: 'mypy.nodes.WhileStmt') -> T:
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| 276 | cfg = self.current_cfg()
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| 277 | with pass_state.CfgLoopContext(
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| 278 | cfg, entry=self.current_statement_id) as loop:
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| 279 | self.accept(o.expr)
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| 280 | self.loop_stack.append(loop)
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| 281 | self.accept(o.body)
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| 282 | self.loop_stack.pop()
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| 283 |
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| 284 | def visit_return_stmt(self, o: 'mypy.nodes.ReturnStmt') -> T:
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| 285 | cfg = self.current_cfg()
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| 286 | if cfg:
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| 287 | cfg.AddDeadend(self.current_statement_id)
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| 288 |
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| 289 | if o.expr:
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| 290 | self.accept(o.expr)
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| 291 |
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| 292 | def visit_if_stmt(self, o: 'mypy.nodes.IfStmt') -> T:
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| 293 | cfg = self.current_cfg()
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| 294 | for expr in o.expr:
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| 295 | self.accept(expr)
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| 296 |
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| 297 | with pass_state.CfgBranchContext(
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| 298 | cfg, self.current_statement_id) as branch_ctx:
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| 299 | with branch_ctx.AddBranch():
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| 300 | for node in o.body:
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| 301 | self.accept(node)
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| 302 |
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| 303 | if o.else_body:
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| 304 | with branch_ctx.AddBranch():
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| 305 | self.accept(o.else_body)
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| 306 |
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| 307 | def visit_break_stmt(self, o: 'mypy.nodes.BreakStmt') -> T:
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| 308 | if len(self.loop_stack):
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| 309 | self.loop_stack[-1].AddBreak(self.current_statement_id)
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| 310 |
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| 311 | def visit_continue_stmt(self, o: 'mypy.nodes.ContinueStmt') -> T:
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| 312 | if len(self.loop_stack):
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| 313 | self.loop_stack[-1].AddContinue(self.current_statement_id)
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| 314 |
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| 315 | def visit_raise_stmt(self, o: 'mypy.nodes.RaiseStmt') -> T:
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| 316 | cfg = self.current_cfg()
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| 317 | if cfg:
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| 318 | cfg.AddDeadend(self.current_statement_id)
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| 319 |
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| 320 | if o.expr:
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| 321 | self.accept(o.expr)
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| 322 |
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| 323 | def visit_try_stmt(self, o: 'mypy.nodes.TryStmt') -> T:
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| 324 | cfg = self.current_cfg()
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| 325 | with pass_state.CfgBranchContext(cfg,
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| 326 | self.current_statement_id) as try_ctx:
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| 327 | with try_ctx.AddBranch() as try_block:
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| 328 | self.accept(o.body)
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| 329 |
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| 330 | for t, v, handler in zip(o.types, o.vars, o.handlers):
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| 331 | with try_ctx.AddBranch(try_block.exit):
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| 332 | self.accept(handler)
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| 333 |
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| 334 | # Expressions
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| 335 |
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| 336 | def visit_call_expr(self, o: 'mypy.nodes.CallExpr') -> T:
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| 337 | cfg = self.current_cfg()
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| 338 | if self.current_func_node:
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| 339 | full_callee = self.resolve_callee(o)
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| 340 | if full_callee:
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| 341 | self.callees[o] = full_callee
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| 342 | cfg.AddFact(
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| 343 | self.current_statement_id,
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| 344 | pass_state.FunctionCall(join_name(full_callee, delim='.')))
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| 345 |
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| 346 | self.accept(o.callee)
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| 347 | for arg in o.args:
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| 348 | self.accept(arg)
|