8271928: ErroneousTree with start position -1

Reviewed-by: jlaskey, vromero

src/jdk.compiler/share/classes/com/sun/tools/javac/tree/TreeInfo.java

@@ -548,8 +548,13 @@ public class TreeInfo {
             }
             case ERRONEOUS: {
                 JCErroneous node = (JCErroneous)tree;
-                if (node.errs != null && node.errs.nonEmpty())
+                if (node.errs != null && node.errs.nonEmpty()) {
-                    return getStartPos(node.errs.head);
+                    int pos = getStartPos(node.errs.head);
+                    if (pos != Position.NOPOS) {
+                        return pos;
+                    }
+                }
+                break;
             }
         }
         return tree.pos;

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

@@ -23,7 +23,7 @@
 
 /*
  * @test
- * @bug 7073631 7159445 7156633 8028235 8065753 8205418 8205913 8228451 8237041 8253584 8246774 8256411 8256149 8259050 8266436 8267221
+ * @bug 7073631 7159445 7156633 8028235 8065753 8205418 8205913 8228451 8237041 8253584 8246774 8256411 8256149 8259050 8266436 8267221 8271928
  * @summary tests error and diagnostics positions
  * @author  Jan Lahoda
  * @modules jdk.compiler/com.sun.tools.javac.api
@@ -1795,6 +1795,31 @@ public class JavacParserTest extends TestCase {
         assertEquals("correct parameter type span", code.substring(typeStart, typeEnd), "int[]...");
     }
 
+    @Test //JDK-8271928
+    void testX() throws IOException {
+        String code = """
+                      package test;
+                          public static void test() {
+                              return test;
+                          }
+                      """;
+
+        JavacTaskImpl ct = (JavacTaskImpl) tool.getTask(null, fm, null,
+                null, null, Arrays.asList(new MyFileObject(code)));
+        CompilationUnitTree cut = ct.parse().iterator().next();
+        SourcePositions sp = Trees.instance(ct).getSourcePositions();
+        new TreePathScanner<Void, Void>() {
+            @Override
+            public Void visitErroneous(ErroneousTree tree, Void p) {
+                int pos = (int) sp.getStartPosition(cut, tree);
+                if (pos == (-1)) {
+                    fail("Invalid source position for an ErroneousTree");
+                }
+                return scan(tree.getErrorTrees(), p);
+            }
+        }.scan(cut, null);
+    }
+
     void run(String[] args) throws Exception {
         int passed = 0, failed = 0;
         final Pattern p = (args != null && args.length > 0)