wake.analysis.cfg module

TransitionConditionKind class

Bases: StrEnum

Source code in wake/analysis/cfg.py

class TransitionConditionKind(StrEnum):
    IS_TRUE = "is true"
    """
    Associated expression evaluates to true.
    """
    IS_FALSE = "is false"
    """
    Associated expression evaluates to false.
    """
    ALWAYS = "always"
    """
    Transition is always taken.
    """
    NEVER = "never"
    """
    Transition is never taken.
    """
    TRY_SUCCEEDED = "try succeeded"
    """
    Try call succeeded.
    """
    TRY_REVERTED = "try reverted"
    """
    Try call reverted with a string reason.
    """
    TRY_PANICKED = "try panicked"
    """
    Try call panicked with an uint256 error code.
    """
    TRY_FAILED = "try failed"
    """
    Try call failed with a bytes memory reason.
    """
    SWITCH_MATCHED = "switch matched"
    """
    Yul switch case value matched the switch expression.
    """
    SWITCH_DEFAULT = "switch default"
    """
    None of the Yul switch case values matched the switch expression.
    """

IS_TRUE = 'is true' class-attribute instance-attribute

Associated expression evaluates to true.

IS_FALSE = 'is false' class-attribute instance-attribute

Associated expression evaluates to false.

ALWAYS = 'always' class-attribute instance-attribute

Transition is always taken.

NEVER = 'never' class-attribute instance-attribute

Transition is never taken.

TRY_SUCCEEDED = 'try succeeded' class-attribute instance-attribute

Try call succeeded.

TRY_REVERTED = 'try reverted' class-attribute instance-attribute

Try call reverted with a string reason.

TRY_PANICKED = 'try panicked' class-attribute instance-attribute

Try call panicked with an uint256 error code.

TRY_FAILED = 'try failed' class-attribute instance-attribute

Try call failed with a bytes memory reason.

SWITCH_MATCHED = 'switch matched' class-attribute instance-attribute

Yul switch case value matched the switch expression.

SWITCH_DEFAULT = 'switch default' class-attribute instance-attribute

None of the Yul switch case values matched the switch expression.

ControlFlowGraph class

Control flow graph for a function or a modifier. Uses NetworkX DiGraph as the underlying data structure.

Holds the following invariants:

• all nodes are of CfgNode type,
• start_node, success_end_node and revert_end_node are always present and empty (i.e. they contain no statements),
• all edges have a condition attribute holding a 2-item tuple:
  • the first item is a TransitionConditionKind enum value,
  • the second item is an optional ExpressionAbc instance.

Tip

The Tools for Solidity VS Code extension provides a visualizer for CFGs. The visualized CFGs are stripped of empty nodes, so they may slightly differ from the CFGs constructed by this class.

Source code in wake/analysis/cfg.py

class ControlFlowGraph:
    """
    Control flow graph for a function or a modifier. Uses NetworkX [DiGraph](https://networkx.org/documentation/stable/reference/classes/digraph.html) as the underlying data structure.

    Holds the following invariants:

    - all nodes are of [CfgNode][wake.analysis.cfg.CfgNode] type,
    - [start_node][wake.analysis.cfg.ControlFlowGraph.start_node], [success_end_node][wake.analysis.cfg.ControlFlowGraph.success_end_node] and [revert_end_node][wake.analysis.cfg.ControlFlowGraph.revert_end_node] are always present and empty (i.e. they contain no statements),
    - all edges have a `condition` attribute holding a 2-item tuple:
        - the first item is a [TransitionConditionKind][wake.analysis.cfg.TransitionConditionKind] enum value,
        - the second item is an optional [ExpressionAbc][wake.ir.expressions.abc.ExpressionAbc] instance.

    !!! tip
        The [Tools for Solidity](https://marketplace.visualstudio.com/items?itemName=AckeeBlockchain.tools-for-solidity) VS Code extension provides a visualizer for CFGs.
        The visualized CFGs are stripped of empty nodes, so they may slightly differ from the CFGs constructed by this class.
    """

    _graph: nx.DiGraph
    _declaration: weakref.ReferenceType[
        Union[FunctionDefinition, ModifierDefinition, YulFunctionDefinition]
    ]
    _statements_lookup: Dict[Union[StatementAbc, YulStatementAbc], CfgNode]
    _start_node: CfgNode
    _success_end_node: CfgNode
    _revert_end_node: CfgNode

    def __init__(
        self,
        declaration: Union[
            FunctionDefinition, ModifierDefinition, YulFunctionDefinition
        ],
    ):
        if declaration.body is None:
            raise ValueError("Function body is None.")
        self._declaration = weakref.ref(declaration)

        self._graph = nx.DiGraph()
        self._start_node = CfgNode()
        self._graph.add_node(self._start_node)
        next_node = CfgNode()
        self._graph.add_node(next_node)
        self._graph.add_edge(
            self._start_node,
            next_node,
            condition=(TransitionConditionKind.ALWAYS, None),
        )
        self._success_end_node = CfgNode()
        self._graph.add_node(self._success_end_node)
        self._revert_end_node = CfgNode()
        self._graph.add_node(self._revert_end_node)

        tmp = CfgNode.from_statement(
            self._graph,
            next_node,
            self._success_end_node,
            self._revert_end_node,
            None,
            None,
            declaration.body,
        )
        self._graph.add_edge(
            tmp,
            self._success_end_node,
            condition=(TransitionConditionKind.ALWAYS, None),
        )

        while _normalize(
            self._graph,
            self._start_node,
            self._success_end_node,
            self._revert_end_node,
        ):
            pass

        self._statements_lookup = {
            stmt: node for node in self._graph.nodes for stmt in node.statements
        }
        for node in self._graph.nodes:
            for stmt in node.statements:
                self._statements_lookup[stmt] = node
            if node.control_statement is not None:
                self._statements_lookup[node.control_statement] = node

    @property
    def graph(self) -> nx.DiGraph:
        """
        Returns:
            Read-only view of the underlying NetworkX DiGraph.
        """
        return self._graph.copy(as_view=True)

    @property
    def declaration(
        self,
    ) -> Union[FunctionDefinition, ModifierDefinition, YulFunctionDefinition]:
        """
        Returns:
            Function or modifier definition for which this CFG was constructed.
        """
        return self._declaration()

    @property
    def start_node(self) -> CfgNode:
        """
        Start node is guaranteed to be empty, i.e. it has no statements.

        Returns:
            Start node of this CFG, i.e. the node that is always executed first.
        """
        return self._start_node

    @property
    def success_end_node(self) -> CfgNode:
        """
        Success end node is guaranteed to be empty, i.e. it has no statements.

        Returns:
            Success end node of this CFG, i.e. the node that is always executed last if the function or modifier does not revert.
        """
        return self._success_end_node

    @property
    def revert_end_node(self) -> CfgNode:
        """
        Revert end node is guaranteed to be empty, i.e. it has no statements.

        Returns:
            Revert end node of this CFG, signaling that the function or modifier reverted under some condition.
        """
        return self._revert_end_node

    def get_cfg_node(self, statement: Union[StatementAbc, YulStatementAbc]) -> CfgNode:
        """
        Raises:
            KeyError: If the given statement is not contained in this CFG or if the statement is of the
                [Block][wake.ir.statements.block.Block], [UncheckedBlock][wake.ir.statements.unchecked_block.UncheckedBlock],
                [YulBlock][wake.ir.yul.block.YulBlock] or [InlineAssembly][wake.ir.statements.inline_assembly.InlineAssembly] type.


        [Block][wake.ir.statements.block.Block], [UncheckedBlock][wake.ir.statements.block.UncheckedBlock], [YulBlock][wake.ir.yul.block.YulBlock] and [InlineAssembly][wake.ir.statements.inline_assembly.InlineAssembly] statements
        serve as containers for other statements and so may be contained in multiple CFG nodes. For this reason, a single [CfgNode][wake.analysis.cfg.CfgNode] cannot be returned for these statements.

        Args:
            statement: Statement for which to get the CFG node.

        Returns:
            CFG node that contains the given statement.
        """
        return self._statements_lookup[statement]

    def is_reachable(
        self,
        start: Union[StatementAbc, YulStatementAbc],
        end: Union[StatementAbc, YulStatementAbc],
    ) -> bool:
        """
        Returns False for `start == end` unless there is a loop in the CFG containing `start`.

        Args:
            start: Statement that is expected to be executed before `end`.
            end: Statement that is expected to be executed after `start`.

        Returns:
            True if there is an execution path from `start` to `end` in this CFG, False otherwise.
        """
        start_node = self._statements_lookup[start]
        end_node = self._statements_lookup[end]
        if start_node == end_node:
            start_index = (
                start_node.statements.index(start)
                if start != start_node.control_statement
                else len(start_node.statements)
            )
            end_index = (
                end_node.statements.index(end)
                if end != end_node.control_statement
                else len(end_node.statements)
            )
            if start_index < end_index:
                return True

            for _, to in nx.edge_dfs(self._graph, start_node):
                if to == end_node:
                    return True

            return False
        else:
            return nx.has_path(self._graph, start_node, end_node)

graph: nx.DiGraph property

Returns:

Type	Description
DiGraph	Read-only view of the underlying NetworkX DiGraph.

declaration: Union[FunctionDefinition, ModifierDefinition, YulFunctionDefinition] property

Returns:

Type	Description
Union[FunctionDefinition, ModifierDefinition, YulFunctionDefinition]	Function or modifier definition for which this CFG was constructed.

start_node: CfgNode property

Start node is guaranteed to be empty, i.e. it has no statements.

Returns:

Type	Description
CfgNode	Start node of this CFG, i.e. the node that is always executed first.

success_end_node: CfgNode property

Success end node is guaranteed to be empty, i.e. it has no statements.

Returns:

Type	Description
CfgNode	Success end node of this CFG, i.e. the node that is always executed last if the function or modifier does not revert.

revert_end_node: CfgNode property

Revert end node is guaranteed to be empty, i.e. it has no statements.

Returns:

Type	Description
CfgNode	Revert end node of this CFG, signaling that the function or modifier reverted under some condition.

get_cfg_node(statement)

Raises:

Type	Description
KeyError	If the given statement is not contained in this CFG or if the statement is of the Block, UncheckedBlock, YulBlock or InlineAssembly type.

Block, UncheckedBlock, YulBlock and InlineAssembly statements serve as containers for other statements and so may be contained in multiple CFG nodes. For this reason, a single CfgNode cannot be returned for these statements.

Parameters:

Name	Type	Description	Default
statement	Union[StatementAbc, YulStatementAbc]	Statement for which to get the CFG node.	required

Returns:

Type	Description
CfgNode	CFG node that contains the given statement.

Source code in wake/analysis/cfg.py

def get_cfg_node(self, statement: Union[StatementAbc, YulStatementAbc]) -> CfgNode:
    """
    Raises:
        KeyError: If the given statement is not contained in this CFG or if the statement is of the
            [Block][wake.ir.statements.block.Block], [UncheckedBlock][wake.ir.statements.unchecked_block.UncheckedBlock],
            [YulBlock][wake.ir.yul.block.YulBlock] or [InlineAssembly][wake.ir.statements.inline_assembly.InlineAssembly] type.


    [Block][wake.ir.statements.block.Block], [UncheckedBlock][wake.ir.statements.block.UncheckedBlock], [YulBlock][wake.ir.yul.block.YulBlock] and [InlineAssembly][wake.ir.statements.inline_assembly.InlineAssembly] statements
    serve as containers for other statements and so may be contained in multiple CFG nodes. For this reason, a single [CfgNode][wake.analysis.cfg.CfgNode] cannot be returned for these statements.

    Args:
        statement: Statement for which to get the CFG node.

    Returns:
        CFG node that contains the given statement.
    """
    return self._statements_lookup[statement]

is_reachable(start, end)

Returns False for start == end unless there is a loop in the CFG containing start.

Parameters:

Name	Type	Description	Default
start	Union[StatementAbc, YulStatementAbc]	Statement that is expected to be executed before end.	required
end	Union[StatementAbc, YulStatementAbc]	Statement that is expected to be executed after start.	required

Returns:

Type	Description
bool	True if there is an execution path from start to end in this CFG, False otherwise.

Source code in wake/analysis/cfg.py

def is_reachable(
    self,
    start: Union[StatementAbc, YulStatementAbc],
    end: Union[StatementAbc, YulStatementAbc],
) -> bool:
    """
    Returns False for `start == end` unless there is a loop in the CFG containing `start`.

    Args:
        start: Statement that is expected to be executed before `end`.
        end: Statement that is expected to be executed after `start`.

    Returns:
        True if there is an execution path from `start` to `end` in this CFG, False otherwise.
    """
    start_node = self._statements_lookup[start]
    end_node = self._statements_lookup[end]
    if start_node == end_node:
        start_index = (
            start_node.statements.index(start)
            if start != start_node.control_statement
            else len(start_node.statements)
        )
        end_index = (
            end_node.statements.index(end)
            if end != end_node.control_statement
            else len(end_node.statements)
        )
        if start_index < end_index:
            return True

        for _, to in nx.edge_dfs(self._graph, start_node):
            if to == end_node:
                return True

        return False
    else:
        return nx.has_path(self._graph, start_node, end_node)

CfgNode class

Basic building block of a control flow graph. Holds a list of statements and an optional control statement that is always executed last (if set). Solidity and Yul statements may be mixed in the same CFG node.

Source code in wake/analysis/cfg.py

class CfgNode:
    """
    Basic building block of a control flow graph. Holds a list of statements and an optional control statement that is always
    executed last (if set). Solidity and Yul statements may be mixed in the same CFG node.
    """

    _id_counter: int = 0
    _id: int
    _statements: List[Union[StatementAbc, YulStatementAbc]]
    # control statement is always the last statement
    _control_statement: Optional[
        Union[
            DoWhileStatement,
            ForStatement,
            IfStatement,
            TryStatement,
            WhileStatement,
            YulForLoop,
            YulIf,
            YulSwitch,
        ]
    ]

    def __init__(self):
        self._id = self.__class__._id_counter
        self.__class__._id_counter += 1
        self._statements = []
        self._control_statement = None

    def __str__(self):
        return (
            "\n".join(statement.source for statement in self.statements)
            if len(self.statements) > 0
            else ""
        )

    @property
    def id(self) -> int:
        """
        The concrete value should not be relied upon, it is only guaranteed to be unique within a single CFG.

        Returns:
            Unique ID of this CFG node.
        """
        return self._id

    @property
    def statements(self) -> Tuple[Union[StatementAbc, YulStatementAbc], ...]:
        """
        Returns:
            Statements contained in this CFG node.
        """
        return tuple(self._statements)

    @property
    def control_statement(
        self,
    ) -> Optional[
        Union[
            DoWhileStatement,
            ForStatement,
            IfStatement,
            TryStatement,
            WhileStatement,
            YulForLoop,
            YulIf,
            YulSwitch,
        ]
    ]:
        """
        Control statements are handled specially in CFG construction, because they contain sub-statements that are not
        part of the current CFG node. At the same time, control statements are always nearest parent statements for
        some expressions and so must be indexed.

        !!! example
            For example, [IfStatement][wake.ir.statements.if_statement.IfStatement] is the nearest parent statement
            of the [IfStatement.condition][wake.ir.statements.if_statement.IfStatement.condition] expression.

        A control statement is always the last statement in a CFG node.

        Returns:
            Control statement of this CFG node, if any.
        """
        return self._control_statement

    @classmethod
    def from_statement(
        cls,
        graph: nx.DiGraph,
        prev: CfgNode,
        success_end: CfgNode,
        revert_end: CfgNode,
        loop_body_post: Optional[CfgNode],
        loop_body_next: Optional[CfgNode],
        statement: Union[StatementAbc, YulStatementAbc],
    ) -> CfgNode:
        if isinstance(statement, (Block, UncheckedBlock, YulBlock)):
            for body_statement in statement.statements:
                prev = cls.from_statement(
                    graph,
                    prev,
                    success_end,
                    revert_end,
                    loop_body_post,
                    loop_body_next,
                    body_statement,
                )
            return prev
        elif isinstance(statement, InlineAssembly):
            return cls.from_statement(
                graph,
                prev,
                success_end,
                revert_end,
                loop_body_post,
                loop_body_next,
                statement.yul_block,
            )
        elif (
            isinstance(statement, YulExpressionStatement)
            and isinstance(statement.expression, YulFunctionCall)
            and statement.expression.function_name.name == "revert"
        ):
            prev._statements.append(statement)
            next = CfgNode()
            graph.add_node(next)
            graph.add_edge(
                prev, revert_end, condition=(TransitionConditionKind.ALWAYS, None)
            )
            graph.add_edge(prev, next, condition=(TransitionConditionKind.NEVER, None))
            return next
        elif (
            isinstance(statement, YulExpressionStatement)
            and isinstance(statement.expression, YulFunctionCall)
            and statement.expression.function_name.name == "return"
        ):
            prev._statements.append(statement)
            next = CfgNode()
            graph.add_node(next)
            graph.add_edge(
                prev, success_end, condition=(TransitionConditionKind.ALWAYS, None)
            )
            graph.add_edge(prev, next, condition=(TransitionConditionKind.NEVER, None))
            return next
        elif isinstance(statement, (Break, YulBreak)):
            prev._statements.append(statement)
            next = CfgNode()
            assert loop_body_next is not None
            graph.add_node(next)
            graph.add_edge(
                prev, loop_body_next, condition=(TransitionConditionKind.ALWAYS, None)
            )
            graph.add_edge(prev, next, condition=(TransitionConditionKind.NEVER, None))
            return next
        elif isinstance(statement, (Continue, YulContinue)):
            prev._statements.append(statement)
            next = CfgNode()
            assert loop_body_post is not None
            graph.add_node(next)
            graph.add_edge(
                prev, loop_body_post, condition=(TransitionConditionKind.ALWAYS, None)
            )
            graph.add_edge(prev, next, condition=(TransitionConditionKind.NEVER, None))
            return next
        elif isinstance(statement, DoWhileStatement):
            return cls.from_do_while_statement(
                graph, prev, success_end, revert_end, statement
            )
        elif isinstance(statement, ForStatement):
            return cls.from_for_statement(
                graph, prev, success_end, revert_end, statement
            )
        elif isinstance(statement, IfStatement):
            return cls.from_if_statement(
                graph,
                prev,
                success_end,
                revert_end,
                loop_body_post,
                loop_body_next,
                statement,
            )
        elif isinstance(statement, (Return, YulLeave)):
            prev._statements.append(statement)
            next = CfgNode()
            graph.add_node(next)
            graph.add_edge(
                prev, success_end, condition=(TransitionConditionKind.ALWAYS, None)
            )
            graph.add_edge(prev, next, condition=(TransitionConditionKind.NEVER, None))
            return next
        elif isinstance(statement, RevertStatement):
            prev._statements.append(statement)
            next = CfgNode()
            graph.add_node(next)
            graph.add_edge(
                prev, revert_end, condition=(TransitionConditionKind.ALWAYS, None)
            )
            graph.add_edge(prev, next, condition=(TransitionConditionKind.NEVER, None))
            return next
        elif isinstance(statement, ExpressionStatement):

            def process_expression(expression: ExpressionAbc, node: CfgNode) -> bool:
                if isinstance(expression, Conditional):
                    true_node = CfgNode()
                    graph.add_node(true_node)
                    false_node = CfgNode()
                    graph.add_node(false_node)

                    graph.add_edge(
                        node,
                        true_node,
                        condition=(
                            TransitionConditionKind.IS_TRUE,
                            expression.condition,
                        ),
                    )
                    graph.add_edge(
                        node,
                        false_node,
                        condition=(
                            TransitionConditionKind.IS_FALSE,
                            expression.condition,
                        ),
                    )

                    true_is_control = process_expression(
                        expression.true_expression, true_node
                    )
                    false_is_control = process_expression(
                        expression.false_expression, false_node
                    )

                    if not true_is_control:
                        graph.remove_node(true_node)
                        if false_is_control:
                            graph.add_edge(
                                node,
                                next,
                                condition=(
                                    TransitionConditionKind.IS_TRUE,
                                    expression.condition,
                                ),
                            )

                    if not false_is_control:
                        graph.remove_node(false_node)
                        if true_is_control:
                            graph.add_edge(
                                node,
                                next,
                                condition=(
                                    TransitionConditionKind.IS_FALSE,
                                    expression.condition,
                                ),
                            )

                    return true_is_control or false_is_control
                elif isinstance(expression, FunctionCall):
                    func_called = expression.function_called
                    if func_called == GlobalSymbol.REVERT:
                        graph.add_edge(
                            node,
                            revert_end,
                            condition=(TransitionConditionKind.ALWAYS, None),
                        )
                        graph.add_edge(
                            node, next, condition=(TransitionConditionKind.NEVER, None)
                        )
                        return True
                    elif func_called in {
                        GlobalSymbol.REQUIRE,
                        GlobalSymbol.ASSERT,
                    }:
                        graph.add_edge(
                            node,
                            next,
                            condition=(
                                TransitionConditionKind.IS_TRUE,
                                expression.arguments[0],
                            ),
                        )
                        graph.add_edge(
                            node,
                            revert_end,
                            condition=(
                                TransitionConditionKind.IS_FALSE,
                                expression.arguments[0],
                            ),
                        )
                        return True
                    else:
                        return False
                else:
                    return False

            prev._statements.append(statement)
            next = CfgNode()
            graph.add_node(next)

            if process_expression(
                statement.expression,  # pyright: ignore reportArgumentType
                prev,
            ):
                return next
            else:
                graph.remove_node(next)
                return prev
        elif isinstance(statement, TryStatement):
            return cls.from_try_statement(
                graph,
                prev,
                success_end,
                revert_end,
                loop_body_post,
                loop_body_next,
                statement,
            )
        elif isinstance(statement, WhileStatement):
            return cls.from_while_statement(
                graph, prev, success_end, revert_end, statement
            )
        elif isinstance(statement, YulCase):
            raise NotImplementedError()  # should be handled by YulSwitch
        elif isinstance(statement, YulForLoop):
            return cls.from_yul_for_loop(
                graph, prev, success_end, revert_end, statement
            )
        elif isinstance(statement, YulIf):
            return cls.from_yul_if(
                graph,
                prev,
                success_end,
                revert_end,
                loop_body_post,
                loop_body_next,
                statement,
            )
        elif isinstance(statement, YulSwitch):
            return cls.from_yul_switch(graph, prev, success_end, revert_end, statement)
        else:
            prev._statements.append(statement)
            return prev

    @classmethod
    def from_if_statement(
        cls,
        graph: nx.DiGraph,
        prev: CfgNode,
        success_end: CfgNode,
        revert_end: CfgNode,
        loop_body_post: Optional[CfgNode],
        loop_body_next: Optional[CfgNode],
        if_statement: IfStatement,
    ) -> CfgNode:
        assert prev._control_statement is None
        prev._control_statement = if_statement
        true_node = CfgNode()
        graph.add_node(true_node)
        true_node_end = cls.from_statement(
            graph,
            true_node,
            success_end,
            revert_end,
            loop_body_post,
            loop_body_next,
            if_statement.true_body,
        )

        false_node = CfgNode()
        graph.add_node(false_node)

        if if_statement.false_body is None:
            false_node_end = false_node
        else:
            false_node_end = cls.from_statement(
                graph,
                false_node,
                success_end,
                revert_end,
                loop_body_post,
                loop_body_next,
                if_statement.false_body,
            )

        next = CfgNode()
        graph.add_node(next)
        graph.add_edge(
            prev,
            true_node,
            condition=(TransitionConditionKind.IS_TRUE, if_statement.condition),
        )
        graph.add_edge(
            prev,
            false_node,
            condition=(TransitionConditionKind.IS_FALSE, if_statement.condition),
        )
        graph.add_edge(
            true_node_end, next, condition=(TransitionConditionKind.ALWAYS, None)
        )
        graph.add_edge(
            false_node_end, next, condition=(TransitionConditionKind.ALWAYS, None)
        )
        return next

    @classmethod
    def from_yul_if(
        cls,
        graph: nx.DiGraph,
        prev: CfgNode,
        success_end: CfgNode,
        revert_end: CfgNode,
        loop_body_post: Optional[CfgNode],
        loop_body_next: Optional[CfgNode],
        if_statement: YulIf,
    ):
        assert prev._control_statement is None
        prev._control_statement = if_statement
        true_node = CfgNode()
        graph.add_node(true_node)
        true_node_end = cls.from_statement(
            graph,
            true_node,
            success_end,
            revert_end,
            loop_body_post,
            loop_body_next,
            if_statement.body,
        )
        next = CfgNode()
        graph.add_node(next)
        graph.add_edge(
            prev,
            true_node,
            condition=(TransitionConditionKind.IS_TRUE, if_statement.condition),
        )
        graph.add_edge(
            prev,
            next,
            condition=(TransitionConditionKind.IS_FALSE, if_statement.condition),
        )
        graph.add_edge(
            true_node_end, next, condition=(TransitionConditionKind.ALWAYS, None)
        )
        return next

    @classmethod
    def from_do_while_statement(
        cls,
        graph: nx.DiGraph,
        prev: CfgNode,
        success_end: CfgNode,
        revert_end: CfgNode,
        do_while_statement: DoWhileStatement,
    ) -> CfgNode:
        body = CfgNode()
        graph.add_node(body)
        next = CfgNode()
        graph.add_node(next)
        body_end = cls.from_statement(
            graph, body, success_end, revert_end, body, next, do_while_statement.body
        )
        assert body_end._control_statement is None
        body_end._control_statement = do_while_statement

        graph.add_edge(prev, body, condition=(TransitionConditionKind.ALWAYS, None))
        graph.add_edge(
            body_end,
            next,
            condition=(TransitionConditionKind.IS_FALSE, do_while_statement.condition),
        )
        graph.add_edge(
            body_end,
            body,
            condition=(TransitionConditionKind.IS_TRUE, do_while_statement.condition),
        )
        return next

    @classmethod
    def from_for_statement(
        cls,
        graph: nx.DiGraph,
        prev: CfgNode,
        success_end: CfgNode,
        revert_end: CfgNode,
        for_statement: ForStatement,
    ) -> CfgNode:
        if for_statement.initialization_expression is not None:
            prev = cls.from_statement(
                graph,
                prev,
                success_end,
                revert_end,
                None,
                None,
                for_statement.initialization_expression,
            )
        assert prev._control_statement is None
        prev._control_statement = for_statement

        body = CfgNode()
        graph.add_node(body)
        next = CfgNode()
        graph.add_node(next)
        loop_post = CfgNode()
        graph.add_node(loop_post)
        if for_statement.loop_expression is not None:
            loop_post_end = cls.from_statement(
                graph,
                loop_post,
                success_end,
                revert_end,
                loop_post,
                next,
                for_statement.loop_expression,
            )
        else:
            loop_post_end = loop_post
        body_end = cls.from_statement(
            graph, body, success_end, revert_end, loop_post, next, for_statement.body
        )

        graph.add_edge(
            body_end, loop_post, condition=(TransitionConditionKind.ALWAYS, None)
        )
        graph.add_edge(
            prev,
            body,
            condition=(TransitionConditionKind.IS_TRUE, for_statement.condition),
        )
        graph.add_edge(
            prev,
            next,
            condition=(TransitionConditionKind.IS_FALSE, for_statement.condition),
        )
        graph.add_edge(
            loop_post_end,
            body,
            condition=(TransitionConditionKind.IS_TRUE, for_statement.condition),
        )
        graph.add_edge(
            loop_post_end,
            next,
            condition=(TransitionConditionKind.IS_FALSE, for_statement.condition),
        )
        return next

    @classmethod
    def from_yul_for_loop(
        cls,
        graph: nx.DiGraph,
        prev: CfgNode,
        success_end: CfgNode,
        revert_end: CfgNode,
        for_loop: YulForLoop,
    ) -> CfgNode:
        assert prev._control_statement is None
        prev = cls.from_statement(
            graph, prev, success_end, revert_end, None, None, for_loop.pre
        )
        assert prev._control_statement is None
        prev._control_statement = for_loop

        body = CfgNode()
        graph.add_node(body)
        next = CfgNode()
        graph.add_node(next)
        loop_post = CfgNode()
        graph.add_node(loop_post)
        body_end = cls.from_statement(
            graph, body, success_end, revert_end, loop_post, next, for_loop.body
        )
        loop_post_end = cls.from_statement(
            graph, loop_post, success_end, revert_end, loop_post, next, for_loop.post
        )

        graph.add_edge(
            body_end, loop_post, condition=(TransitionConditionKind.ALWAYS, None)
        )
        graph.add_edge(
            prev, body, condition=(TransitionConditionKind.IS_TRUE, for_loop.condition)
        )
        graph.add_edge(
            prev,
            next,
            condition=(TransitionConditionKind.IS_FALSE, for_loop.condition),
        )
        graph.add_edge(
            loop_post_end,
            body,
            condition=(TransitionConditionKind.IS_TRUE, for_loop.condition),
        )
        graph.add_edge(
            loop_post_end,
            next,
            condition=(TransitionConditionKind.IS_FALSE, for_loop.condition),
        )
        return next

    @classmethod
    def from_try_statement(
        cls,
        graph: nx.DiGraph,
        prev: CfgNode,
        success_end: CfgNode,
        revert_end: CfgNode,
        loop_body_post: Optional[CfgNode],
        loop_body_next: Optional[CfgNode],
        try_statement: TryStatement,
    ) -> CfgNode:
        assert prev._control_statement is None
        prev._control_statement = try_statement

        success_node = CfgNode()
        graph.add_node(success_node)
        success_node_end = cls.from_statement(
            graph,
            success_node,
            success_end,
            revert_end,
            loop_body_post,
            loop_body_next,
            try_statement.clauses[0].block,
        )

        revert_node = None
        revert_node_end = None
        panic_node = None
        panic_node_end = None
        fail_node = None
        fail_node_end = None
        for clause in try_statement.clauses[1:]:
            if clause.error_name == "Error":
                revert_node = CfgNode()
                graph.add_node(revert_node)
                revert_node_end = cls.from_statement(
                    graph,
                    revert_node,
                    success_end,
                    revert_end,
                    loop_body_post,
                    loop_body_next,
                    clause.block,
                )
            elif clause.error_name == "Panic":
                panic_node = CfgNode()
                graph.add_node(panic_node)
                panic_node_end = cls.from_statement(
                    graph,
                    panic_node,
                    success_end,
                    revert_end,
                    loop_body_post,
                    loop_body_next,
                    clause.block,
                )
            elif clause.error_name == "":
                fail_node = CfgNode()
                graph.add_node(fail_node)
                fail_node_end = cls.from_statement(
                    graph,
                    fail_node,
                    success_end,
                    revert_end,
                    loop_body_post,
                    loop_body_next,
                    clause.block,
                )
            else:
                raise NotImplementedError(f"Unknown error name: {clause.error_name}")

        next = CfgNode()
        graph.add_node(next)

        graph.add_edge(
            prev,
            success_node,
            condition=(
                TransitionConditionKind.TRY_SUCCEEDED,
                try_statement.external_call,
            ),
        )
        graph.add_edge(
            success_node_end, next, condition=(TransitionConditionKind.ALWAYS, None)
        )
        if revert_node is not None:
            graph.add_edge(
                prev,
                revert_node,
                condition=(
                    TransitionConditionKind.TRY_REVERTED,
                    try_statement.external_call,
                ),
            )
            graph.add_edge(
                revert_node_end, next, condition=(TransitionConditionKind.ALWAYS, None)
            )
        if panic_node is not None:
            graph.add_edge(
                prev,
                panic_node,
                condition=(
                    TransitionConditionKind.TRY_PANICKED,
                    try_statement.external_call,
                ),
            )
            graph.add_edge(
                panic_node_end, next, condition=(TransitionConditionKind.ALWAYS, None)
            )
        if fail_node is not None:
            graph.add_edge(
                prev,
                fail_node,
                condition=(
                    TransitionConditionKind.TRY_FAILED,
                    try_statement.external_call,
                ),
            )
            graph.add_edge(
                fail_node_end, next, condition=(TransitionConditionKind.ALWAYS, None)
            )
        else:
            graph.add_edge(
                prev,
                revert_end,
                condition=(
                    TransitionConditionKind.TRY_FAILED,
                    try_statement.external_call,
                ),
            )
        return next

    @classmethod
    def from_yul_switch(
        cls,
        graph: nx.DiGraph,
        prev: CfgNode,
        success_end: CfgNode,
        revert_end: CfgNode,
        switch: YulSwitch,
    ) -> CfgNode:
        assert prev._control_statement is None
        prev._control_statement = switch

        next = CfgNode()
        graph.add_node(next)

        for case_ in switch.cases:
            case_node = CfgNode()
            graph.add_node(case_node)
            graph.add_edge(
                prev,
                case_node,
                condition=(TransitionConditionKind.SWITCH_MATCHED, case_.value)
                if case_.value != "default"
                else (TransitionConditionKind.SWITCH_DEFAULT, None),
            )
            case_node_end = cls.from_statement(
                graph,
                case_node,
                success_end,
                revert_end,
                case_node,
                next,
                case_.body,
            )
            graph.add_edge(
                case_node_end, next, condition=(TransitionConditionKind.ALWAYS, None)
            )

        if not any(case.value == "default" for case in switch.cases):
            graph.add_edge(
                prev,
                next,
                condition=(TransitionConditionKind.SWITCH_DEFAULT, None),
            )

        return next

    @classmethod
    def from_while_statement(
        cls,
        graph: nx.DiGraph,
        prev: CfgNode,
        success_end: CfgNode,
        revert_end: CfgNode,
        while_statement: WhileStatement,
    ) -> CfgNode:
        assert prev._control_statement is None
        prev._control_statement = while_statement

        body = CfgNode()
        graph.add_node(body)
        next = CfgNode()
        graph.add_node(next)
        body_end = cls.from_statement(
            graph, body, success_end, revert_end, body, next, while_statement.body
        )

        graph.add_edge(
            prev,
            body,
            condition=(TransitionConditionKind.IS_TRUE, while_statement.condition),
        )
        graph.add_edge(
            prev,
            next,
            condition=(TransitionConditionKind.IS_FALSE, while_statement.condition),
        )
        graph.add_edge(
            body_end,
            body,
            condition=(TransitionConditionKind.IS_TRUE, while_statement.condition),
        )
        graph.add_edge(
            body_end,
            next,
            condition=(TransitionConditionKind.IS_FALSE, while_statement.condition),
        )
        return next

id: int property

The concrete value should not be relied upon, it is only guaranteed to be unique within a single CFG.

Returns:

Type	Description
int	Unique ID of this CFG node.

statements: Tuple[Union[StatementAbc, YulStatementAbc], ...] property

Returns:

Type	Description
Tuple[Union[StatementAbc, YulStatementAbc], ...]	Statements contained in this CFG node.

control_statement: Optional[Union[DoWhileStatement, ForStatement, IfStatement, TryStatement, WhileStatement, YulForLoop, YulIf, YulSwitch]] property

Control statements are handled specially in CFG construction, because they contain sub-statements that are not part of the current CFG node. At the same time, control statements are always nearest parent statements for some expressions and so must be indexed.

Example

For example, IfStatement is the nearest parent statement of the IfStatement.condition expression.

A control statement is always the last statement in a CFG node.

Returns:

Type	Description
Optional[Union[DoWhileStatement, ForStatement, IfStatement, TryStatement, WhileStatement, YulForLoop, YulIf, YulSwitch]]	Control statement of this CFG node, if any.