fixes the bug reported in Issue #241.

It makes $r available in the code given to CtBehavior#insertBefore().

Readme.html

@@ -283,7 +283,7 @@ <h2>Changes</h2>
 
 <p>-version 3.25
 <ul>
-    <li>GitHub Issue #72 (PR #231), #242 (PR #243).
+    <li>GitHub Issue #72 (PR #231), #241, #242 (PR #243).
 </ul>
 
 <p>-version 3.24.1 on December 9, 2018

src/main/javassist/CtBehavior.java

@@ -782,7 +782,7 @@ private void insertBefore(String src, boolean rebuild)
                                         Modifier.isStatic(getModifiers()));
             jv.recordParamNames(ca, nvars);
             jv.recordLocalVariables(ca, 0);
-            jv.recordType(getReturnType0());
+            jv.recordReturnType(getReturnType0(), false);
             jv.compileStmnt(src);
             Bytecode b = jv.getBytecode();
             int stack = b.getMaxStack();

src/test/javassist/JvstTest5.java

@@ -484,4 +484,18 @@ public void testSwitchCaseWithStringConstant2() throws Exception {
         Object obj = make(cc.getName());
         assertEquals(1, invoke(obj, "run"));   
     }
+
+    // Issue #241
+    public void testInsertBeforeAndDollarR() throws Exception {
+        CtClass cc = sloader.get(test5.InsertBeforeDollarR.class.getName());
+        CtMethod m = cc.getDeclaredMethod("foo");
+        m.insertBefore("{ if ($1 == 1) return ($r)$2; }");
+        try {
+            m.insertBefore("{ $_ = \"bar\"; }");
+            assertTrue(false);
+        } catch (CannotCompileException e) {}
+        cc.writeFile();
+        Object obj = make(cc.getName());
+        assertEquals(1, invoke(obj, "run"));
+    }
 }

src/test/test5/InsertBeforeDollarR.java

@@ -0,0 +1,14 @@
+package test5;
+
+public class InsertBeforeDollarR {
+    public int run() {
+        if (foo(1, "baz").equals("baz"))
+            return 1;
+        else
+            return 0;
+    }
+
+    public String foo(int i, Object obj) {
+        return String.valueOf(i);
+    }
+}