8324736: Invalid end positions for EMPTY_STATEMENT

Reviewed-by: vromero

src/jdk.compiler/share/classes/com/sun/tools/javac/parser/JavacParser.java

@@ -3965,8 +3965,9 @@ public JCTree.JCCompilationUnit parseCompilationUnit() {
             // comes after before deciding how best to handle them.
             ListBuffer<JCTree> semiList = new ListBuffer<>();
             while (firstTypeDecl && mods == null && token.kind == SEMI) {
-                semiList.append(toP(F.at(token.pos).Skip()));
+                int pos = token.pos;
                 nextToken();
+                semiList.append(toP(F.at(pos).Skip()));
                 if (token.kind == EOF)
                     break OUTER;
             }

test/langtools/tools/javac/parser/ReversedSourcePositions.java

@@ -0,0 +1,85 @@
+/*
+ * Copyright (c) 2024, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code 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 General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * @test
+ * @bug 8324736
+ * @summary Verify starting and ending source positions are not backwards
+ * @modules jdk.compiler/com.sun.tools.javac.tree
+ * @run main ReversedSourcePositions
+ */
+
+import com.sun.source.tree.CompilationUnitTree;
+import com.sun.source.tree.Tree;
+import com.sun.source.util.JavacTask;
+import com.sun.source.util.TreeScanner;
+import com.sun.tools.javac.tree.JCTree;
+
+import java.io.IOException;
+import java.net.URI;
+import java.util.List;
+
+import javax.tools.JavaCompiler;
+import javax.tools.JavaFileObject;
+import javax.tools.SimpleJavaFileObject;
+import javax.tools.ToolProvider;
+
+public class ReversedSourcePositions {
+
+    public static void main(String... args) throws Exception {
+
+        // Create test case source
+        var source = new SimpleJavaFileObject(URI.create("file://T.java"), JavaFileObject.Kind.SOURCE) {
+            @Override
+            public CharSequence getCharContent(boolean ignoreEncodingErrors) throws IOException {
+                return """
+                    package errorpronecrash;
+                    ;
+                    public class ReproFile {}
+                """;
+            }
+        };
+
+        // Parse source
+        JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();
+        JavaCompiler.CompilationTask task = compiler.getTask(null, null, null, List.of(), List.of(), List.of(source));
+        Iterable<? extends CompilationUnitTree> units = ((JavacTask)task).parse();
+
+        // Look for reversed source positions
+        JCTree.JCCompilationUnit unit = (JCTree.JCCompilationUnit)units.iterator().next();
+        unit.accept(new TreeScanner<Void, Void>() {
+            @Override
+            public Void scan(Tree node, Void aVoid) {
+                if (node instanceof JCTree tree) {
+                    int start = tree.getStartPosition();
+                    int end = tree.getEndPosition(unit.endPositions);
+                    if (start >= end) {
+                        throw new AssertionError(
+                          String.format("[%d, %d] %s %s\n", start, end, tree.getKind(), tree));
+                    }
+                }
+                return super.scan(node, aVoid);
+            }
+        }, null);
+    }
+}