diff -r 97aaf02ed830 -r 5497ee9d40f4 test/langtools/tools/javac/api/ast/CodeBuilder.java
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/test/langtools/tools/javac/api/ast/CodeBuilder.java	Thu Mar 28 11:31:30 2019 +0100
@@ -0,0 +1,159 @@
+/*
+ * Copyright (c) 2019, 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.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * 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.
+ */
+
+import com.sun.source.tree.BinaryTree;
+import com.sun.source.tree.ClassTree;
+import com.sun.source.tree.CompilationUnitTree;
+import com.sun.source.tree.IdentifierTree;
+import com.sun.source.tree.LiteralTree;
+import com.sun.source.tree.PrimitiveTypeTree;
+import com.sun.source.tree.Tree;
+import com.sun.source.tree.VariableTree;
+import com.sun.source.util.TreeScanner;
+
+import java.util.HashSet;
+import java.util.Locale;
+import java.util.Set;
+
+
+public class CodeBuilder {
+
+    public static String buildCodeToGenerate(Tree t, String builder) {
+        StringBuilder result = new StringBuilder();
+        new TreeScanner<Void, Void>() {
+            private final Set<String> usedNames = new HashSet<>();
+            private String currentBuilder = builder;
+            @Override
+            public Void visitClass(ClassTree node, Void p) {
+                result.append(currentBuilder() + "._class(\"" + node.getSimpleName() + "\", ");
+                doScan("C", () -> super.visitClass(node, p));
+                result.append(")");
+                return null;
+            }
+            @Override
+            public Void visitCompilationUnit(CompilationUnitTree node, Void p) {
+                result.append(currentBuilder() + ".createCompilationUnitTree(");
+                doScan("U", () -> super.visitCompilationUnit(node, p));
+                result.append(")");
+                return null;
+            }
+            @Override
+            public Void visitVariable(VariableTree node, Void p) {
+                result.append(currentBuilder() + ".field(\"" + node.getName() + "\", "); //XXX: field/vs local variable!
+                doScan("T", node.getType());
+                result.append(", ");
+                doScan("F", () -> {
+                    //TODO: modifiers....
+                    if (node.getInitializer() != null) {
+                        result.append(currentBuilder() + ".init(");
+                        doScan("E", node.getInitializer());
+                        result.append(")");
+                    }
+                });
+                result.append(")");
+                return null;
+            }
+
+            @Override
+            public Void visitPrimitiveType(PrimitiveTypeTree node, Void p) {
+                result.append(currentBuilder() + "._" + node.getPrimitiveTypeKind().name().toLowerCase(Locale.ROOT) + "()");
+                return null;
+            }
+
+            @Override
+            public Void visitLiteral(LiteralTree node, Void p) {
+                result.append(currentBuilder() + ".literal(" + node.getValue() + ")");
+                return null;
+            }
+
+            @Override
+            public Void visitBinary(BinaryTree node, Void p) {
+                switch (node.getKind()) {
+                    case PLUS:
+                        result.append(currentBuilder() + ".plus(");
+                        doScan("E", node.getLeftOperand());
+                        result.append(", ");
+                        doScan("E", node.getRightOperand());
+                        result.append(")");
+                        break;
+                    default: throw new IllegalStateException("Not handled: " + node.getKind());
+                }
+                return null;
+            }
+
+            @Override
+            public Void visitIdentifier(IdentifierTree node, Void p) {
+                result.append(currentBuilder() + ".ident(\"" + node.getName() + "\")");
+                return null;
+            }
+
+            private String currentBuilder() {
+                if (currentBuilder != null) {
+                    String res = currentBuilder;
+                    currentBuilder = null;
+                    return res;
+                }
+                return "";
+            }
+            private void doScan(String preferredBuilderName, Tree... subTreesToScan) {
+                doScan(preferredBuilderName, () -> {
+                    for (Tree tree : subTreesToScan) {
+                        scan(tree, null);
+                    }
+                });
+            }
+
+            private void doScan(String preferredBuilderName, Runnable scan) {
+                String prevBuilder = currentBuilder;
+                String builder = inferBuilderName(preferredBuilderName);
+                try {
+                    result.append(builder + " -> ");
+                    int len = result.length();
+                    currentBuilder = builder;
+                    scan.run();
+                    if (result.length() == len) {
+                        result.append("{}");
+                    }
+                } finally {
+                    currentBuilder = prevBuilder;
+                    usedNames.remove(builder);
+                }
+            }
+            private String inferBuilderName(String preferredBuilderName) {
+                Integer idx = null;
+                while (true) {
+                    String thisBuilder = preferredBuilderName + (idx != null ? idx : "");
+                    if (usedNames.add(thisBuilder)) {
+                        return thisBuilder;
+                    }
+                    idx = idx != null ? idx + 1 : 1;
+                }
+            }
+        }.scan(t, null);
+
+        return result.toString();
+    }
+
+}