jdk-24/test/langtools/tools/javac/patterns/DisambiguateParenthesizedPattern.java

/**
 * @test
 * @modules jdk.compiler/com.sun.tools.javac.file
 *          jdk.compiler/com.sun.tools.javac.main
 *          jdk.compiler/com.sun.tools.javac.parser
 *          jdk.compiler/com.sun.tools.javac.tree
 *          jdk.compiler/com.sun.tools.javac.util
 * @compile --enable-preview -source ${jdk.version} DisambiguateParenthesizedPattern.java
 * @run main/othervm --enable-preview DisambiguateParenthesizedPattern
 */

import com.sun.source.tree.CaseLabelTree;
import com.sun.source.tree.ClassTree;
import com.sun.source.tree.CompilationUnitTree;
import com.sun.source.tree.ExpressionTree;
import com.sun.source.tree.MethodTree;
import com.sun.source.tree.PatternTree;
import com.sun.source.tree.SwitchTree;
import com.sun.tools.javac.file.JavacFileManager;
import com.sun.tools.javac.parser.JavacParser;
import com.sun.tools.javac.parser.ParserFactory;
import com.sun.tools.javac.util.Context;
import com.sun.tools.javac.main.Option;
import com.sun.tools.javac.util.Options;
import java.nio.charset.Charset;

public class DisambiguateParenthesizedPattern {

    public static void main(String... args) throws Throwable {
        DisambiguateParenthesizedPattern test = new DisambiguateParenthesizedPattern();
        test.disambiguationTest("String s",
                                 ExpressionType.PATTERN);
        test.disambiguationTest("String s && s.isEmpty()",
                                 ExpressionType.PATTERN);
        test.disambiguationTest("(String s)",
                                 ExpressionType.PATTERN);
        test.disambiguationTest("((String s))",
                                 ExpressionType.PATTERN);
        test.disambiguationTest("(String) s",
                                 ExpressionType.EXPRESSION);
        test.disambiguationTest("((String) s)",
                                 ExpressionType.EXPRESSION);
        test.disambiguationTest("((0x1))",
                                 ExpressionType.EXPRESSION);
        test.disambiguationTest("(a > b)",
                                 ExpressionType.EXPRESSION);
        test.disambiguationTest("(a >> b)",
                                 ExpressionType.EXPRESSION);
        test.disambiguationTest("(a >>> b)",
                                 ExpressionType.EXPRESSION);
        test.disambiguationTest("(a < b | a > b)",
                                 ExpressionType.EXPRESSION);
        test.disambiguationTest("(a << b | a >> b)",
                                 ExpressionType.EXPRESSION);
        test.disambiguationTest("(a << b || a < b | a >>> b)",
                                 ExpressionType.EXPRESSION);
        test.disambiguationTest("(a < c.d > b)",
                                 ExpressionType.PATTERN);
    }

    private final ParserFactory factory;

    public DisambiguateParenthesizedPattern() {
        Context context = new Context();
        JavacFileManager jfm = new JavacFileManager(context, true, Charset.defaultCharset());
        Options.instance(context).put(Option.PREVIEW, "");
        factory = ParserFactory.instance(context);
    }

    void disambiguationTest(String snippet, ExpressionType expectedType) {
        String code = """
                      public class Test {
                          private void test() {
                              switch (null) {
                                  case SNIPPET -> {}
                              }
                          }
                      }
                      """.replace("SNIPPET", snippet);
        JavacParser parser = factory.newParser(code, false, false, false);
        CompilationUnitTree result = parser.parseCompilationUnit();
        ClassTree clazz = (ClassTree) result.getTypeDecls().get(0);
        MethodTree method = (MethodTree) clazz.getMembers().get(0);
        SwitchTree st = (SwitchTree) method.getBody().getStatements().get(0);
        CaseLabelTree label = st.getCases().get(0).getLabels().get(0);
        ExpressionType actualType = switch (label) {
            case ExpressionTree et -> ExpressionType.EXPRESSION;
            case PatternTree pt -> ExpressionType.PATTERN;
            default -> throw new AssertionError("Unexpected result: " + result);
        };
        if (expectedType != actualType) {
            throw new AssertionError("Expected: " + expectedType + ", actual: " + actualType +
                                      ", for: " + code + ", parsed: " + result);
        }
    }

    enum ExpressionType {
        PATTERN,
        EXPRESSION;
    }

}