7159445: (javac) emits inaccurate diagnostics for enhanced for-loops

Reviewed-by: jjg
Contributed-by: jan.lahoda@oracle.com

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

@@ -2206,10 +2206,15 @@ public class JavacParser implements Parser {
         } else {
             JCExpression t = term(EXPR | TYPE);
             if ((lastmode & TYPE) != 0 &&
-                (token.kind == IDENTIFIER || token.kind == ASSERT || token.kind == ENUM))
+                (token.kind == IDENTIFIER || token.kind == ASSERT ||
+                 token.kind == ENUM)) {
                 return variableDeclarators(modifiersOpt(), t, stats).toList();
-            else
+            } else if ((lastmode & TYPE) != 0 && token.kind == COLON) {
+                error(pos, "bad.initializer", "for-loop");
+                return List.of((JCStatement)F.at(pos).VarDef(null, null, t, null));
+            } else {
                 return moreStatementExpressions(pos, t, stats).toList();
+            }
         }
     }
 

src/share/classes/com/sun/tools/javac/resources/compiler.properties

@@ -137,6 +137,10 @@ compiler.err.array.req.but.found=\
 compiler.err.attribute.value.must.be.constant=\
     attribute value must be constant
 
+# 0: statement type
+compiler.err.bad.initializer=\
+    bad initializer for {0}
+
 compiler.err.break.outside.switch.loop=\
     break outside switch or loop
 

test/tools/javac/diags/examples/ForeachBadInitialization.java

+/*
+ * Copyright (c) 2012, 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.
+ */
+
+// key: compiler.err.bad.initializer
+import java.util.List;
+class ForeachBadInitialization {
+    void m() {
+        List<String> s = null;
+        for (a : s) {}
+    }
+}

test/tools/javac/parser/JavacParserTest.java

@@ -23,7 +23,7 @@
 
 /*
  * @test
- * @bug 7073631
+ * @bug 7073631 7159445
  * @summary tests error and diagnostics positions
  * @author  Jan Lahoda
  */
@@ -875,6 +875,7 @@ public class JavacParserTest extends TestCase {
         testMissingClassError();
         testSwitchError();
         testMethodError();
+        testErrorRecoveryForEnhancedForLoop142381();
     }
 
     public static void main(String... args) throws IOException {
@@ -892,8 +893,10 @@ abstract class TestCase {
         }
     }
 
-    void assertFalse(String message, boolean empty) {
-        throw new UnsupportedOperationException("Not yet implemented");
+    void assertFalse(String message, boolean bvalue) {
+        if (bvalue == true) {
+            fail(message);
+        }
     }
 
     void assertEquals(String message, int i, long l) {