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This project contains a parser for the Checker Framework's stub files: https://checkerframework.org/manual/#stub . It is a fork of the JavaParser project.
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/*
 * Copyright (C) 2007-2010 Júlio Vilmar Gesser.
 * Copyright (C) 2011, 2013-2024 The JavaParser Team.
 *
 * This file is part of JavaParser.
 *
 * JavaParser can be used either under the terms of
 * a) the GNU Lesser General Public License as published by
 *     the Free Software Foundation, either version 3 of the License, or
 *     (at your option) any later version.
 * b) the terms of the Apache License
 *
 * You should have received a copy of both licenses in LICENCE.LGPL and
 * LICENCE.APACHE. Please refer to those files for details.
 *
 * JavaParser is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Lesser General Public License for more details.
 */
package com.github.javaparser.ast.expr;

import static com.github.javaparser.utils.Utils.assertNotNull;

import com.github.javaparser.TokenRange;
import com.github.javaparser.ast.AllFieldsConstructor;
import com.github.javaparser.ast.Generated;
import com.github.javaparser.ast.Node;
import com.github.javaparser.ast.nodeTypes.NodeWithType;
import com.github.javaparser.ast.observer.ObservableProperty;
import com.github.javaparser.ast.type.Type;
import com.github.javaparser.ast.visitor.CloneVisitor;
import com.github.javaparser.metamodel.JavaParserMetaModel;
import com.github.javaparser.metamodel.PatternExprMetaModel;
import java.util.Optional;
import java.util.function.Consumer;

/**
 * Pattern Matching in Java
 *
 * Java 1.0 to 13
 * Not available.
 * 

 * Java 14
 * Java 14 introduced TypePatterns with simple pattern matching in {@code instanceof} expressions.
 * @see com.github.javaparser.ast.expr.TypePatternExpr
 * Java 21
 * In Java 21, support for pattern matching was extended to switch expressions and {@code Record Patterns}
 * were introduced. Since {@code Record Patterns} and {@code TypePatterns} can be used interchangeably, the
 * {@code PatternExpr} class is used as a common parent for both in the JavaParser AST.
 *
 * JDK21 Grammar
 * 

 * Pattern:
 *     TypePattern
 *     RecordPattern
 * TypePattern:
 *     LocalVariableDeclaration
 * RecordPattern:
 *     ReferenceType ( [PatternList] )
 * PatternList:
 *     Pattern {, Pattern }
 *
 * @author Johannes Coetzee
 *
 * @see JEP305: https://bugs.openjdk.java.net/browse/JDK-8181287
 * @see https://docs.oracle.com/javase/specs/jls/se11/html/jls-15.html#jls-15.20
 */
public abstract class PatternExpr extends Expression implements NodeWithType {

    private Type type;

    @AllFieldsConstructor
    public PatternExpr(final Type type) {}

    @Override
    @Generated("com.github.javaparser.generator.core.node.TypeCastingGenerator")
    public boolean isPatternExpr() {
        return true;
    }

    @Override
    @Generated("com.github.javaparser.generator.core.node.TypeCastingGenerator")
    public PatternExpr asPatternExpr() {
        return this;
    }

    @Override
    @Generated("com.github.javaparser.generator.core.node.TypeCastingGenerator")
    public Optional toPatternExpr() {
        return Optional.of(this);
    }

    @Override
    @Generated("com.github.javaparser.generator.core.node.TypeCastingGenerator")
    public void ifPatternExpr(Consumer action) {
        action.accept(this);
    }

    @Override
    @Generated("com.github.javaparser.generator.core.node.CloneGenerator")
    public PatternExpr clone() {
        return (PatternExpr) accept(new CloneVisitor(), null);
    }

    @Override
    @Generated("com.github.javaparser.generator.core.node.GetMetaModelGenerator")
    public PatternExprMetaModel getMetaModel() {
        return JavaParserMetaModel.patternExprMetaModel;
    }

    /**
     * This constructor is used by the parser and is considered private.
     */
    @Generated("com.github.javaparser.generator.core.node.MainConstructorGenerator")
    public PatternExpr(TokenRange tokenRange) {
        super(tokenRange);
        customInitialization();
    }

    @Generated("com.github.javaparser.generator.core.node.PropertyGenerator")
    public PatternExpr setType(final Type type) {
        assertNotNull(type);
        if (type == this.type) {
            return this;
        }
        notifyPropertyChange(ObservableProperty.TYPE, this.type, type);
        if (this.type != null) this.type.setParentNode(null);
        this.type = type;
        setAsParentNodeOf(type);
        return this;
    }

    /**
     * The types of record patters and top-level type patterns must be reference types, but nested type patterns
     * can also have primitive types.
     */
    @Generated("com.github.javaparser.generator.core.node.PropertyGenerator")
    public Type getType() {
        return type;
    }

    @Override
    @Generated("com.github.javaparser.generator.core.node.ReplaceMethodGenerator")
    public boolean replace(Node node, Node replacementNode) {
        if (node == null) {
            return false;
        }
        if (node == type) {
            setType((Type) replacementNode);
            return true;
        }
        return super.replace(node, replacementNode);
    }

    /**
     * This constructor is used by the parser and is considered private.
     */
    @Generated("com.github.javaparser.generator.core.node.MainConstructorGenerator")
    public PatternExpr(TokenRange tokenRange, Type type) {
        super(tokenRange);
        setType(type);
        customInitialization();
    }
}