Package com.google.javascript.jscomp
Class ControlFlowAnalysis
- java.lang.Object
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- com.google.javascript.jscomp.ControlFlowAnalysis
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- All Implemented Interfaces:
CompilerPass
,NodeTraversal.Callback
public final class ControlFlowAnalysis extends java.lang.Object implements NodeTraversal.Callback, CompilerPass
This is a compiler pass that computes a control flow graph. Note that this is only a CompilerPass because the Compiler invokes it via Compiler#process. It is never included in a PassConfig.
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Method Summary
All Methods Static Methods Instance Methods Concrete Methods Modifier and Type Method Description static ControlFlowGraph<Node>
getCfg(AbstractCompiler compiler, Node cfgRoot)
static boolean
isBreakTarget(Node target, java.lang.String label)
Checks if target is actually the break target of labeled continue.static boolean
mayThrowException(Node n)
Determines if the subtree might throw an exception.void
process(Node externs, Node root)
Process the JS with root node root.boolean
shouldTraverse(NodeTraversal nodeTraversal, Node n, Node parent)
Visits a node in preorder (before its children) and decides whether its children should be traversed.void
visit(NodeTraversal t, Node n, Node parent)
Visits a node in postorder (after its children).
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Method Detail
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getCfg
public static ControlFlowGraph<Node> getCfg(AbstractCompiler compiler, Node cfgRoot)
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process
public void process(Node externs, Node root)
Description copied from interface:CompilerPass
Process the JS with root node root. Can modify the contents of each Node tree- Specified by:
process
in interfaceCompilerPass
- Parameters:
externs
- Top of external JS treeroot
- Top of JS tree
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shouldTraverse
public boolean shouldTraverse(NodeTraversal nodeTraversal, Node n, Node parent)
Description copied from interface:NodeTraversal.Callback
Visits a node in preorder (before its children) and decides whether its children should be traversed. If the children should be traversed, they will be visited byNodeTraversal.Callback.shouldTraverse(NodeTraversal, Node, Node)
in preorder and byNodeTraversal.Callback.visit(NodeTraversal, Node, Node)
in postorder.Siblings are always visited left-to-right.
Implementations can have side-effects (e.g. modify the parse tree). Removing the current node is legal, but removing or reordering nodes above the current node may cause nodes to be visited twice or not at all.
- Specified by:
shouldTraverse
in interfaceNodeTraversal.Callback
- Parameters:
nodeTraversal
- The current traversal.n
- The current node.parent
- The parent of the current node.- Returns:
- whether the children of this node should be visited
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visit
public void visit(NodeTraversal t, Node n, Node parent)
Description copied from interface:NodeTraversal.Callback
Visits a node in postorder (after its children). A node is visited in postorder iffNodeTraversal.Callback.shouldTraverse(NodeTraversal, Node, Node)
returned true for its parent. In particular, the root node is never visited in postorder.Siblings are always visited left-to-right.
Implementations can have side-effects (e.g. modify the parse tree). Removing the current node is legal, but removing or reordering nodes above the current node may cause nodes to be visited twice or not at all.
- Specified by:
visit
in interfaceNodeTraversal.Callback
- Parameters:
t
- The current traversal.n
- The current node.parent
- The parent of the current node.
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isBreakTarget
public static boolean isBreakTarget(Node target, java.lang.String label)
Checks if target is actually the break target of labeled continue. The label can be null if it is an unlabeled break.
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mayThrowException
public static boolean mayThrowException(Node n)
Determines if the subtree might throw an exception.
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