com.google.javascript.jscomp

Class LinkedFlowScope

java.lang.Object

com.google.javascript.jscomp.LinkedFlowScope

All Implemented Interfaces:

LatticeElement, FlowScope, StaticTypedScope<JSType>, StaticScope

class LinkedFlowScope
extends java.lang.Object
implements FlowScope

A flow scope that tries to store as little symbol information as possible, instead delegating to its parents. Optimized for low memory use.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
private static class	LinkedFlowScope.FlatFlowScopeCache A map that tries to cache as much symbol table information as possible in a map.
(package private) static class	LinkedFlowScope.FlowScopeJoinOp Join the two FlowScopes.
private static class	LinkedFlowScope.LinkedFlowSlot A static slot that can be used in a linked list.

Field Summary

Fields

Modifier and Type	Field and Description
private LinkedFlowScope.FlatFlowScopeCache	cache
private int	depth
private LinkedFlowScope.FlatFlowScopeCache	flattened
private boolean	frozen
private LinkedFlowScope.LinkedFlowSlot	lastSlot
(package private) static int	MAX_DEPTH
private LinkedFlowScope	parent

Constructor Summary

Constructors

Modifier	Constructor and Description
(package private)	LinkedFlowScope(LinkedFlowScope.FlatFlowScopeCache cache)
private	LinkedFlowScope(LinkedFlowScope.FlatFlowScopeCache cache, LinkedFlowScope directParent)
(package private)	LinkedFlowScope(LinkedFlowScope directParent)

Method Summary

Modifier and Type	Method and Description
private java.util.Map<java.lang.String,StaticTypedSlot<JSType>>	allFlowSlots() Gets all the symbols that have been defined before this point in the current flow.
void	completeScope(StaticTypedScope<JSType> staticScope) Look through the given scope, and try to find slots where it doesn't have enough type information.
FlowScope	createChildFlowScope() Creates a child of this flow scope, to represent an instruction directly following this one.
static LinkedFlowScope	createEntryLattice(TypedScope scope) Creates an entry lattice for the flow.
private static boolean	diffSlots(StaticTypedSlot<JSType> slotA, StaticTypedSlot<JSType> slotB) Determines whether two slots are meaningfully different for the purposes of data flow analysis.
boolean	equals(java.lang.Object other)
StaticTypedSlot<JSType>	findUniqueRefinedSlot(FlowScope blindScope) Iterate through all the linked flow scopes before this one.
private boolean	flowsFromBottom() Whether this flows from a bottom scope.
private TypedScope	getFunctionScope() Gets the function scope for this flow scope.
StaticTypedSlot<JSType>	getOwnSlot(java.lang.String name) Like getSlot but does not recurse into parent scopes.
StaticTypedScope<JSType>	getParentScope() Returns the scope enclosing this one or null if none.
Node	getRootNode() Returns the root node associated with this scope.
StaticTypedSlot<JSType>	getSlot(java.lang.String name) Get the slot for the given symbol.
JSType	getTypeOfThis() Returns the expected type of this in the current scope.
int	hashCode()
void	inferQualifiedSlot(Node node, java.lang.String symbol, JSType bottomType, JSType inferredType, boolean declared) Infer the type of a qualified name.
void	inferSlotType(java.lang.String symbol, JSType type) Defines the type of a symbol at this point in the flow.
LinkedFlowScope	optimize() Remove flow scopes that add nothing to the flow.

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, toString, wait, wait, wait

Field Detail

cache

private final LinkedFlowScope.FlatFlowScopeCache cache

parent

private final LinkedFlowScope parent

depth

private int depth

MAX_DEPTH

static final int MAX_DEPTH

See Also:

Constant Field Values

flattened

private LinkedFlowScope.FlatFlowScopeCache flattened

frozen

private boolean frozen

lastSlot

private LinkedFlowScope.LinkedFlowSlot lastSlot

Constructor Detail

LinkedFlowScope

private LinkedFlowScope(LinkedFlowScope.FlatFlowScopeCache cache,
                        LinkedFlowScope directParent)

LinkedFlowScope

LinkedFlowScope(LinkedFlowScope.FlatFlowScopeCache cache)

LinkedFlowScope

LinkedFlowScope(LinkedFlowScope directParent)

Method Detail

getFunctionScope

private TypedScope getFunctionScope()

Gets the function scope for this flow scope.

flowsFromBottom

private boolean flowsFromBottom()

Whether this flows from a bottom scope.

createEntryLattice

public static LinkedFlowScope createEntryLattice(TypedScope scope)

Creates an entry lattice for the flow.

inferSlotType

public void inferSlotType(java.lang.String symbol,
                          JSType type)

Description copied from interface: FlowScope

Defines the type of a symbol at this point in the flow.

Specified by:

inferSlotType in interface FlowScope

inferQualifiedSlot

public void inferQualifiedSlot(Node node,
                               java.lang.String symbol,
                               JSType bottomType,
                               JSType inferredType,
                               boolean declared)

Description copied from interface: FlowScope

Infer the type of a qualified name. When traversing the control flow of a function, simple names are declared at the bottom of the flow lattice. But there are far too many qualified names to be able to do this and be performant. So the bottoms of qualified names are declared lazily. Therefore, when inferring a qualified slot, we need both the "bottom" type of the slot when we enter the scope, and the current type being inferred.

Specified by:

inferQualifiedSlot in interface FlowScope

getTypeOfThis

public JSType getTypeOfThis()

Description copied from interface: StaticTypedScope

Returns the expected type of this in the current scope.

Specified by:

getTypeOfThis in interface StaticTypedScope<JSType>

getRootNode

public Node getRootNode()

Description copied from interface: StaticScope

Returns the root node associated with this scope. May be null.

Specified by:

getRootNode in interface StaticScope

getParentScope

public StaticTypedScope<JSType> getParentScope()

Description copied from interface: StaticTypedScope

Returns the scope enclosing this one or null if none.

Specified by:

getParentScope in interface StaticTypedScope<JSType>

Specified by:

getParentScope in interface StaticScope

getSlot

public StaticTypedSlot<JSType> getSlot(java.lang.String name)

Get the slot for the given symbol.

Specified by:

getSlot in interface StaticTypedScope<JSType>

Specified by:

getSlot in interface StaticScope

Parameters:

name - The name of the variable slot to look up.

Returns:

The defined slot for the variable, or null if no definition exists.

getOwnSlot

public StaticTypedSlot<JSType> getOwnSlot(java.lang.String name)

Description copied from interface: StaticTypedScope

Like getSlot but does not recurse into parent scopes.

Specified by:

getOwnSlot in interface StaticTypedScope<JSType>

Specified by:

getOwnSlot in interface StaticScope

createChildFlowScope

public FlowScope createChildFlowScope()

Description copied from interface: FlowScope

Creates a child of this flow scope, to represent an instruction directly following this one.

Specified by:

createChildFlowScope in interface FlowScope

findUniqueRefinedSlot

public StaticTypedSlot<JSType> findUniqueRefinedSlot(FlowScope blindScope)

Iterate through all the linked flow scopes before this one. If there's one and only one slot defined between this scope and the blind scope, return it.

Specified by:

findUniqueRefinedSlot in interface FlowScope

Parameters:

blindScope - The scope before the refinement, i.e. some parent of the this scope or itself.

Returns:

The unique refined variable if found or null.

completeScope

public void completeScope(StaticTypedScope<JSType> staticScope)

Look through the given scope, and try to find slots where it doesn't have enough type information. Then fill in that type information with stuff that we've inferred in the local flow.

Specified by:

completeScope in interface FlowScope

optimize

public LinkedFlowScope optimize()

Remove flow scopes that add nothing to the flow.

Specified by:

optimize in interface FlowScope

equals

public boolean equals(java.lang.Object other)

Overrides:

equals in class java.lang.Object

diffSlots

private static boolean diffSlots(StaticTypedSlot<JSType> slotA,
                                 StaticTypedSlot<JSType> slotB)

Determines whether two slots are meaningfully different for the purposes of data flow analysis.

allFlowSlots

private java.util.Map<java.lang.String,StaticTypedSlot<JSType>> allFlowSlots()

Gets all the symbols that have been defined before this point in the current flow. Does not return slots that have not changed during the flow. For example, consider the code: var x = 3; function f() { var y = 5; y = 6; // FLOW POINT var z = y; return z; } A FlowScope at FLOW POINT will return a slot for y, but not a slot for x or z.

hashCode

public int hashCode()

Overrides:

hashCode in class java.lang.Object