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package com.oracle.js.parser.ir;

Symbol is a symbolic address for a value ("variable" if you wish). Identifiers in JavaScript source, as well as certain synthetic variables created by the compiler are represented by Symbol objects. Symbols can address either local variable slots in bytecode ("slotted symbol"), or properties in scope objects ("scoped symbol"). A symbol can also end up being defined but then not used during symbol assignment calculations; such symbol will be neither scoped, nor slotted; it represents a dead variable (it might be written to, but is never read). Finally, a symbol can be both slotted and in scope. This special case can only occur with bytecode method parameters. They all come in as slotted, but if they are used by a nested function (or eval) then they will be copied into the scope object, and used from there onwards. Two further special cases are parameters stored in NativeArguments objects and parameters stored in Object[] parameter to variable-arity functions. Those use the #getFieldIndex() property to refer to their location. /**
 * Symbol is a symbolic address for a value ("variable" if you wish). Identifiers in JavaScript
 * source, as well as certain synthetic variables created by the compiler are represented by Symbol
 * objects. Symbols can address either local variable slots in bytecode ("slotted symbol"), or
 * properties in scope objects ("scoped symbol"). A symbol can also end up being defined but then
 * not used during symbol assignment calculations; such symbol will be neither scoped, nor slotted;
 * it represents a dead variable (it might be written to, but is never read). Finally, a symbol can
 * be both slotted and in scope. This special case can only occur with bytecode method parameters.
 * They all come in as slotted, but if they are used by a nested function (or eval) then they will
 * be copied into the scope object, and used from there onwards. Two further special cases are
 * parameters stored in {@code NativeArguments} objects and parameters stored in {@code Object[]}
 * parameter to variable-arity functions. Those use the {@code #getFieldIndex()} property to refer
 * to their location.
 */
public final class Symbol implements Comparable<Symbol> {
    
Is this a let binding /** Is this a let binding */
    public static final int IS_LET = 1 << 0;
    
Is this a const binding /** Is this a const binding */
    public static final int IS_CONST = 1 << 1;
    
Is this a var binding /** Is this a var binding */
    public static final int IS_VAR = 1 << 2;
    
Mask for kind flags /** Mask for kind flags */
    public static final int KINDMASK = IS_LET | IS_CONST | IS_VAR;

    
Is this a global binding /** Is this a global binding */
    public static final int IS_GLOBAL = 1 << 3;
    
Is this a parameter /** Is this a parameter */
    public static final int IS_PARAM = 1 << 4;
    
Is this a this symbol /** Is this a this symbol */
    public static final int IS_THIS = 1 << 5;
    
Is this an internal symbol, never represented explicitly in source code /** Is this an internal symbol, never represented explicitly in source code */
    public static final int IS_INTERNAL = 1 << 6;
    
Is this a function self-reference symbol /** Is this a function self-reference symbol */
    public static final int IS_FUNCTION_SELF = 1 << 7;
    
Is this a hoistable var declaration? /** Is this a hoistable var declaration? */
    public static final int IS_HOISTABLE_DECLARATION = 1 << 8;
    
Is this a program level symbol? /** Is this a program level symbol? */
    public static final int IS_PROGRAM_LEVEL = 1 << 9;
    
Is this symbol seen a declaration? Used for block scoped LET and CONST symbols only. /** Is this symbol seen a declaration? Used for block scoped LET and CONST symbols only. */
    public static final int HAS_BEEN_DECLARED = 1 << 10;
    
Is this symbol a block function declaration hoisted into the body scope. /** Is this symbol a block function declaration hoisted into the body scope. */
    public static final int IS_HOISTED_BLOCK_FUNCTION = 1 << 11;
    
Is this symbol a var declaration binding that needs to be initialized with the value of the
parent's scope's binding with the same name? Used for parameter bindings that are replicated
in the body's VariableEnvironment.
/**
     * Is this symbol a var declaration binding that needs to be initialized with the value of the
     * parent's scope's binding with the same name? Used for parameter bindings that are replicated
     * in the body's VariableEnvironment.
     */
    public static final int IS_VAR_REDECLARED_HERE = 1 << 12;
    
Is this symbol declared in an unprotected switch case context? /** Is this symbol declared in an unprotected switch case context? */
    public static final int IS_DECLARED_IN_SWITCH_BLOCK = 1 << 13;
    
Is this symbol an indirect import binding of a module environment? /** Is this symbol an indirect import binding of a module environment? */
    public static final int IS_IMPORT_BINDING = 1 << 14;
    
Is this symbol a catch parameter binding? /** Is this symbol a catch parameter binding? */
    public static final int IS_CATCH_PARAMETER = 1 << 15;
    
Is this symbol a block function declaration? /** Is this symbol a block function declaration? */
    public static final int IS_BLOCK_FUNCTION_DECLARATION = 1 << 16;
    
Is this symbol a private name? /** Is this symbol a private name? */
    public static final int IS_PRIVATE_NAME = 1 << 17;
    
Is this symbol a private name associated with a static member? /** Is this symbol a private name associated with a static member? */
    public static final int IS_PRIVATE_NAME_STATIC = 1 << 18;
    
Is this symbol a private name associated with a method? /** Is this symbol a private name associated with a method? */
    public static final int IS_PRIVATE_NAME_METHOD = 1 << 19;
    
Is this symbol a private name associated with an accessor? /** Is this symbol a private name associated with an accessor? */
    public static final int IS_PRIVATE_NAME_ACCESSOR = 1 << 20;

    
Null or name identifying symbol. /** Null or name identifying symbol. */
    private final String name;

    
Symbol flags. /** Symbol flags. */
    private int flags;

    
Number of times this symbol is used in code /** Number of times this symbol is used in code */
    private int useCount;

    
Constructor
Params:
name – name of symbol
flags – symbol flags/**
     * Constructor
     *
     * @param name name of symbol
     * @param flags symbol flags
     */
    public Symbol(final String name, final int flags) {
        this.name = name;
        this.flags = flags;
        assert (flags & KINDMASK) != 0;
    }

    @Override
    public String toString() {
        final StringBuilder sb = new StringBuilder();

        sb.append(name);

        sb.append(' ');
        if (isLet()) {
            sb.append('L');
        } else if (isConst()) {
            sb.append('C');
        } else if (isVar()) {
            if (isGlobal()) {
                sb.append('G');
            } else if (isParam()) {
                sb.append('P');
            } else {
                sb.append('V');
            }
        }

        return sb.toString();
    }

    @Override
    public int compareTo(final Symbol other) {
        return name.compareTo(other.name);
    }

    
Check if this symbol is a hoistable var declaration.
See Also:
VarNode.isHoistableDeclaration()
Returns:
true if a hoistable var declaration/**
     * Check if this symbol is a hoistable var declaration.
     *
     * @return true if a hoistable var declaration
     * @see VarNode#isHoistableDeclaration()
     */
    public boolean isHoistableDeclaration() {
        return (flags & IS_HOISTABLE_DECLARATION) != 0;
    }

    
Check if this symbol is a variable
Returns:
true if variable/**
     * Check if this symbol is a variable
     *
     * @return true if variable
     */
    public boolean isVar() {
        return (flags & IS_VAR) != 0;
    }

    
Check if this symbol is a global (undeclared) variable
Returns:
true if global/**
     * Check if this symbol is a global (undeclared) variable
     *
     * @return true if global
     */
    public boolean isGlobal() {
        return (flags & IS_GLOBAL) != 0;
    }

    
Check if this symbol is a function parameter
Returns:
true if parameter/**
     * Check if this symbol is a function parameter
     *
     * @return true if parameter
     */
    public boolean isParam() {
        return (flags & IS_PARAM) != 0;
    }

    
Check if this is a program (script) level definition
Returns:
true if program level/**
     * Check if this is a program (script) level definition
     *
     * @return true if program level
     */
    public boolean isProgramLevel() {
        return (flags & IS_PROGRAM_LEVEL) != 0;
    }

    
Check if this symbol is a constant
Returns:
true if a constant/**
     * Check if this symbol is a constant
     *
     * @return true if a constant
     */
    public boolean isConst() {
        return (flags & IS_CONST) != 0;
    }

    
Check if this is an internal symbol, without an explicit JavaScript source code equivalent
Returns:
true if internal/**
     * Check if this is an internal symbol, without an explicit JavaScript source code equivalent
     *
     * @return true if internal
     */
    public boolean isInternal() {
        return (flags & IS_INTERNAL) != 0;
    }

    
Check if this symbol represents this 
Returns:
true if this/**
     * Check if this symbol represents {@code this}
     *
     * @return true if this
     */
    public boolean isThis() {
        return (flags & IS_THIS) != 0;
    }

    
Check if this symbol is a let
Returns:
true if let/**
     * Check if this symbol is a let
     *
     * @return true if let
     */
    public boolean isLet() {
        return (flags & IS_LET) != 0;
    }

    
Flag this symbol as a function's self-referencing symbol.
Returns:
true if this symbol as a function's self-referencing symbol./**
     * Flag this symbol as a function's self-referencing symbol.
     *
     * @return true if this symbol as a function's self-referencing symbol.
     */
    public boolean isFunctionSelf() {
        return (flags & IS_FUNCTION_SELF) != 0;
    }

    
Is this a block scoped symbol
Returns:
true if block scoped/**
     * Is this a block scoped symbol
     *
     * @return true if block scoped
     */
    public boolean isBlockScoped() {
        return isLet() || isConst();
    }

    
Has this symbol been declared
Returns:
true if declared/**
     * Has this symbol been declared
     *
     * @return true if declared
     */
    public boolean hasBeenDeclared() {
        return (flags & HAS_BEEN_DECLARED) != 0;
    }

    
Mark this symbol as declared
/**
     * Mark this symbol as declared
     */
    public void setHasBeenDeclared() {
        assert !isDeclaredInSwitchBlock();
        if (!hasBeenDeclared()) {
            flags |= HAS_BEEN_DECLARED;
        }
    }

    
Mark this symbol as declared/undeclared
/**
     * Mark this symbol as declared/undeclared
     */
    public void setHasBeenDeclared(boolean declared) {
        if (declared) {
            flags |= HAS_BEEN_DECLARED;
        } else {
            flags &= ~HAS_BEEN_DECLARED;
        }
    }

    
Get the symbol flags
Returns:
flags/**
     * Get the symbol flags
     *
     * @return flags
     */
    public int getFlags() {
        return flags;
    }

    
Get the name of this symbol
Returns:
symbol name/**
     * Get the name of this symbol
     *
     * @return symbol name
     */
    public String getName() {
        return name;
    }

    
Get the symbol's use count
Returns:
the number of times the symbol is used in code./**
     * Get the symbol's use count
     *
     * @return the number of times the symbol is used in code.
     */
    public int getUseCount() {
        return useCount;
    }

    
Has this symbol been declared
Returns:
true if declared/**
     * Has this symbol been declared
     *
     * @return true if declared
     */
    public boolean isDeclaredInSwitchBlock() {
        return (flags & IS_DECLARED_IN_SWITCH_BLOCK) != 0;
    }

    
See Also:
IS_IMPORT_BINDING
Returns:
true if this symbol is an indirect import binding/**
     * @return true if this symbol is an indirect import binding
     * @see #IS_IMPORT_BINDING
     */
    public boolean isImportBinding() {
        return (flags & IS_IMPORT_BINDING) != 0;
    }

    
See Also:
IS_CATCH_PARAMETER
Returns:
true if this symbol is a catch parameter binding/**
     * @return true if this symbol is a catch parameter binding
     * @see #IS_CATCH_PARAMETER
     */
    public boolean isCatchParameter() {
        return (flags & IS_CATCH_PARAMETER) != 0;
    }

    public boolean isVarRedeclaredHere() {
        return (flags & IS_VAR_REDECLARED_HERE) != 0;
    }

    
Is this symbol a hoisted block function declaration.
/**
     * Is this symbol a hoisted block function declaration.
     */
    public boolean isHoistedBlockFunctionDeclaration() {
        return (flags & IS_HOISTED_BLOCK_FUNCTION) != 0;
    }

    
Mark this symbol as a hoisted block function declaration.
/**
     * Mark this symbol as a hoisted block function declaration.
     */
    public void setHoistedBlockFunctionDeclaration() {
        assert isBlockScoped();
        flags |= IS_HOISTED_BLOCK_FUNCTION;
    }

    
Is this symbol a block function declaration.
/**
     * Is this symbol a block function declaration.
     */
    public boolean isBlockFunctionDeclaration() {
        return (flags & IS_BLOCK_FUNCTION_DECLARATION) != 0;
    }

    
Is this symbol a private name.
/**
     * Is this symbol a private name.
     */
    public boolean isPrivateName() {
        return (flags & IS_PRIVATE_NAME) != 0;
    }

    
Is this symbol a private name associated with a static member.
/**
     * Is this symbol a private name associated with a static member.
     */
    public boolean isPrivateNameStatic() {
        return (flags & IS_PRIVATE_NAME_STATIC) != 0;
    }

    
Is this symbol a private name associated with a field.
/**
     * Is this symbol a private name associated with a field.
     */
    public boolean isPrivateField() {
        return isPrivateName() && !isPrivateMethod() && !isPrivateAccessor();
    }

    
Is this symbol a private name associated with a method.
/**
     * Is this symbol a private name associated with a method.
     */
    public boolean isPrivateMethod() {
        return (flags & IS_PRIVATE_NAME_METHOD) != 0;
    }

    
Is this symbol a private name associated with an accessor.
/**
     * Is this symbol a private name associated with an accessor.
     */
    public boolean isPrivateAccessor() {
        return (flags & IS_PRIVATE_NAME_ACCESSOR) != 0;
    }
}