8024415: Bug in javac Pretty: Wrong precedence in JCConditional trees

Fixed precedence and associativity issues with pretty printing of JCConditional expressions.

Co-authored-by: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: jfranck

langtools/src/share/classes/com/sun/tools/javac/tree/Pretty.java

@@ -782,9 +782,9 @@ public class Pretty extends JCTree.Visitor {
     public void visitConditional(JCConditional tree) {
         try {
             open(prec, TreeInfo.condPrec);
-            printExpr(tree.cond, TreeInfo.condPrec);
+            printExpr(tree.cond, TreeInfo.condPrec + 1);
             print(" ? ");
-            printExpr(tree.truepart, TreeInfo.condPrec);
+            printExpr(tree.truepart);
             print(" : ");
             printExpr(tree.falsepart, TreeInfo.condPrec);
             close(prec, TreeInfo.condPrec);

langtools/test/tools/javac/tree/T8024415.java

@@ -0,0 +1,113 @@
+/*
+ * Copyright (c) 2013, 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 8024415
+ * @summary Pretty printing of JCConditional does not follow the precedence and
+ *          associativity rules of JCConditional
+ * @run testng T8024415
+ */
+
+
+import static org.testng.Assert.assertEquals;
+
+import java.io.IOException;
+import java.io.StringWriter;
+
+import org.testng.annotations.Test;
+
+import com.sun.tools.javac.file.JavacFileManager;
+import com.sun.tools.javac.tree.JCTree;
+import com.sun.tools.javac.tree.JCTree.JCExpression;
+import com.sun.tools.javac.tree.Pretty;
+import com.sun.tools.javac.tree.TreeMaker;
+import com.sun.tools.javac.util.Context;
+import com.sun.tools.javac.util.Names;
+
+
+/*
+ * Test verifies that the precedence rules of conditional expressions
+ * (JCConditional) are correct.
+ */
+@Test
+public class T8024415 {
+
+    TreeMaker maker;
+    JCExpression x;
+
+
+    public T8024415() {
+        Context ctx = new Context();
+        JavacFileManager.preRegister(ctx);
+        maker = TreeMaker.instance(ctx);
+        Names names = Names.instance(ctx);
+        x = maker.Ident(names.fromString("x"));
+    }
+
+
+    // JLS 15.25: The conditional operator is syntactically right-associative
+    // (it groups right-to-left). Thus, a?b:c?d:e?f:g means the same as
+    // a?b:(c?d:(e?f:g)).
+    public void testAssociativity() throws IOException {
+
+        JCTree left   = maker.Conditional(maker.Conditional(x, x, x), x, x);
+        JCTree right  = maker.Conditional(x, x, maker.Conditional(x, x, x));
+
+        String prettyLeft   = prettyPrint(left);
+        String prettyRight  = prettyPrint(right);
+
+        assertEquals(prettyLeft.replaceAll("\\s", ""),  "(x?x:x)?x:x");
+        assertEquals(prettyRight.replaceAll("\\s", ""), "x?x:x?x:x");
+
+    }
+
+
+    // The true-part of of a conditional expression is surrounded by ? and :
+    // and can thus always be parsed unambiguously without surrounding
+    // parentheses.
+    public void testPrecedence() throws IOException {
+
+        JCTree left   = maker.Conditional(maker.Assign(x, x), x, x);
+        JCTree middle = maker.Conditional(x, maker.Assign(x, x), x);
+        JCTree right  = maker.Conditional(x, x, maker.Assign(x, x));
+
+        String prettyLeft   = prettyPrint(left);
+        String prettyMiddle = prettyPrint(middle);
+        String prettyRight  = prettyPrint(right);
+
+        assertEquals(prettyLeft.replaceAll("\\s", ""),   "(x=x)?x:x");
+        assertEquals(prettyMiddle.replaceAll("\\s", ""), "x?x=x:x");
+        assertEquals(prettyRight.replaceAll("\\s", ""),  "x?x:(x=x)");
+
+    }
+
+
+    // Helper method
+    private static String prettyPrint(JCTree tree) throws IOException {
+        StringWriter sw = new StringWriter();
+        new Pretty(sw, true).printExpr(tree);
+        return sw.toString();
+    }
+
+}