diff --git a/modules/lang-painless/src/main/java/org/elasticsearch/painless/Def.java b/modules/lang-painless/src/main/java/org/elasticsearch/painless/Def.java
index 867b481a2a4d7..496c2702a8ba8 100644
--- a/modules/lang-painless/src/main/java/org/elasticsearch/painless/Def.java
+++ b/modules/lang-painless/src/main/java/org/elasticsearch/painless/Def.java
@@ -622,23 +622,41 @@ static MethodHandle lookupIterator(Class<?> receiverClass) {
     // Conversion methods for def to primitive types.
 
     public static boolean defToboolean(final Object value) {
-        return (boolean)value;
+        if (value instanceof Boolean) {
+            return (boolean) value;
+        } else {
+            throw new ClassCastException(
+                    "cannot cast def [" + PainlessLookupUtility.typeToUnboxedType(value.getClass()).getCanonicalName() + "] to boolean");
+        }
     }
 
     public static byte defTobyteImplicit(final Object value) {
-        return (byte)value;
+        if (value instanceof Byte) {
+            return (byte)value;
+        } else {
+            throw new ClassCastException("cannot implicitly cast " +
+                    "def [" + PainlessLookupUtility.typeToUnboxedType(value.getClass()).getCanonicalName() + "] to byte");
+        }
     }
 
     public static short defToshortImplicit(final Object value) {
         if (value instanceof Byte) {
             return (byte)value;
-        } else {
+        } else if (value instanceof Short) {
             return (short)value;
+        } else {
+            throw new ClassCastException("cannot implicitly cast " +
+                    "def [" + PainlessLookupUtility.typeToUnboxedType(value.getClass()).getCanonicalName() + "] to short");
         }
     }
 
     public static char defTocharImplicit(final Object value) {
-        return (char)value;
+        if (value instanceof Character) {
+            return (char)value;
+        } else {
+            throw new ClassCastException("cannot implicitly cast " +
+                    "def [" + PainlessLookupUtility.typeToUnboxedType(value.getClass()).getCanonicalName() + "] to char");
+        }
     }
 
     public static int defTointImplicit(final Object value) {
@@ -648,8 +666,11 @@ public static int defTointImplicit(final Object value) {
             return (short)value;
         } else if (value instanceof Character) {
             return (char)value;
-        } else {
+        } else if (value instanceof Integer) {
             return (int)value;
+        } else {
+            throw new ClassCastException("cannot implicitly cast " +
+                    "def [" + PainlessLookupUtility.typeToUnboxedType(value.getClass()).getCanonicalName() + "] to int");
         }
     }
 
@@ -662,8 +683,12 @@ public static long defTolongImplicit(final Object value) {
             return (char)value;
         } else if (value instanceof Integer) {
             return (int)value;
-        } else {
+        } else if (value instanceof Long) {
             return (long)value;
+        } else {
+            throw new ClassCastException(
+                    "cannot implicitly cast " +
+                            "def [" + PainlessLookupUtility.typeToUnboxedType(value.getClass()).getCanonicalName() + "] to long");
         }
     }
 
@@ -678,8 +703,12 @@ public static float defTofloatImplicit(final Object value) {
             return (int)value;
         } else if (value instanceof Long) {
             return (long)value;
-        } else {
+        } else if (value instanceof Float) {
             return (float)value;
+        } else {
+            throw new ClassCastException(
+                    "cannot implicitly cast " +
+                            "def [" + PainlessLookupUtility.typeToUnboxedType(value.getClass()).getCanonicalName() + "] to float");
         }
     }
 
@@ -696,64 +725,129 @@ public static double defTodoubleImplicit(final Object value) {
             return (long)value;
         } else if (value instanceof Float) {
             return (float)value;
-        } else {
+        } else if (value instanceof Double) {
             return (double)value;
+        } else {
+            throw new ClassCastException("cannot implicitly cast def [" + value.getClass().getCanonicalName() + "] to double");
         }
     }
 
     public static byte defTobyteExplicit(final Object value) {
         if (value instanceof Character) {
             return (byte)(char)value;
-        } else {
+        } else if (
+                value instanceof Byte    ||
+                value instanceof Short   ||
+                value instanceof Integer ||
+                value instanceof Long    ||
+                value instanceof Float   ||
+                value instanceof Double
+        ) {
             return ((Number)value).byteValue();
+        } else {
+            throw new ClassCastException("cannot explicitly cast def [" + value.getClass().getCanonicalName() + "] to byte");
         }
     }
 
     public static short defToshortExplicit(final Object value) {
         if (value instanceof Character) {
             return (short)(char)value;
-        } else {
+        } else if (
+                value instanceof Byte    ||
+                value instanceof Short   ||
+                value instanceof Integer ||
+                value instanceof Long    ||
+                value instanceof Float   ||
+                value instanceof Double
+        ) {
             return ((Number)value).shortValue();
+        } else {
+            throw new ClassCastException("cannot explicitly cast def [" + value.getClass().getCanonicalName() + "] to short");
         }
     }
 
     public static char defTocharExplicit(final Object value) {
         if (value instanceof Character) {
             return (char)value;
-        } else {
+        } else if (
+                value instanceof Byte    ||
+                value instanceof Short   ||
+                value instanceof Integer ||
+                value instanceof Long    ||
+                value instanceof Float   ||
+                value instanceof Double
+        ) {
             return (char)((Number)value).intValue();
+        } else {
+            throw new ClassCastException("cannot explicitly cast def [" + value.getClass().getCanonicalName() + "] to char");
         }
     }
 
     public static int defTointExplicit(final Object value) {
         if (value instanceof Character) {
             return (char)value;
-        } else {
+        } else if (
+                value instanceof Byte    ||
+                value instanceof Short   ||
+                value instanceof Integer ||
+                value instanceof Long    ||
+                value instanceof Float   ||
+                value instanceof Double
+        ) {
             return ((Number)value).intValue();
+        } else {
+            throw new ClassCastException("cannot explicitly cast def [" + value.getClass().getCanonicalName() + "] to int");
         }
     }
 
     public static long defTolongExplicit(final Object value) {
         if (value instanceof Character) {
             return (char)value;
-        } else {
+        } else if (
+                value instanceof Byte    ||
+                value instanceof Short   ||
+                value instanceof Integer ||
+                value instanceof Long    ||
+                value instanceof Float   ||
+                value instanceof Double
+        ) {
             return ((Number)value).longValue();
+        } else {
+            throw new ClassCastException("cannot explicitly cast def [" + value.getClass().getCanonicalName() + "] to long");
         }
     }
 
     public static float defTofloatExplicit(final Object value) {
         if (value instanceof Character) {
             return (char)value;
-        } else {
+        } else if (
+                value instanceof Byte    ||
+                value instanceof Short   ||
+                value instanceof Integer ||
+                value instanceof Long    ||
+                value instanceof Float   ||
+                value instanceof Double
+        ) {
             return ((Number)value).floatValue();
+        } else {
+            throw new ClassCastException("cannot explicitly cast def [" + value.getClass().getCanonicalName() + "] to float");
         }
     }
 
     public static double defTodoubleExplicit(final Object value) {
         if (value instanceof Character) {
             return (char)value;
-        } else {
+        } else if (
+                value instanceof Byte    ||
+                value instanceof Short   ||
+                value instanceof Integer ||
+                value instanceof Long    ||
+                value instanceof Float   ||
+                value instanceof Double
+        ) {
             return ((Number)value).doubleValue();
+        } else {
+            throw new ClassCastException("cannot explicitly cast def [" + value.getClass().getCanonicalName() + "] to double");
         }
     }
 
diff --git a/modules/lang-painless/src/test/java/org/elasticsearch/painless/BasicExpressionTests.java b/modules/lang-painless/src/test/java/org/elasticsearch/painless/BasicExpressionTests.java
index 6ff727d987cdd..b729c6769c50c 100644
--- a/modules/lang-painless/src/test/java/org/elasticsearch/painless/BasicExpressionTests.java
+++ b/modules/lang-painless/src/test/java/org/elasticsearch/painless/BasicExpressionTests.java
@@ -115,12 +115,12 @@ public void testIllegalDefCast() {
         Exception exception = expectScriptThrows(ClassCastException.class, () -> {
             exec("def x = 1.0; int y = x; return y;");
         });
-        assertTrue(exception.getMessage().contains("cannot be cast"));
+        assertTrue(exception.getMessage().contains("cannot implicitly cast"));
 
         exception = expectScriptThrows(ClassCastException.class, () -> {
             exec("def x = (short)1; byte y = x; return y;");
         });
-        assertTrue(exception.getMessage().contains("cannot be cast"));
+        assertTrue(exception.getMessage().contains("cannot implicitly cast"));
     }
 
     public void testCat() {
diff --git a/modules/lang-painless/src/test/java/org/elasticsearch/painless/DefCastTests.java b/modules/lang-painless/src/test/java/org/elasticsearch/painless/DefCastTests.java
new file mode 100644
index 0000000000000..2add69989b1b8
--- /dev/null
+++ b/modules/lang-painless/src/test/java/org/elasticsearch/painless/DefCastTests.java
@@ -0,0 +1,338 @@
+/*
+ * Licensed to Elasticsearch under one or more contributor
+ * license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright
+ * ownership. Elasticsearch licenses this file to you under
+ * the Apache License, Version 2.0 (the "License"); you may
+ * not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+package org.elasticsearch.painless;
+
+public class DefCastTests extends ScriptTestCase {
+
+    public void testdefTobooleanImplicit() {
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = 'string'; boolean b = d;"));
+        assertEquals(true, exec("def d = true; boolean b = d; b"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = (byte)0; boolean b = d;"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = (short)0; boolean b = d;"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = (char)0; boolean b = d;"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = (int)0; boolean b = d;"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = (long)0; boolean b = d;"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = (float)0; boolean b = d;"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = (double)0; boolean b = d;"));
+        assertEquals(false, exec("def d = Boolean.valueOf(false); boolean b = d; b"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = Byte.valueOf(0); boolean b = d;"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = Short.valueOf(0); boolean b = d;"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = Character.valueOf(0); boolean b = d;"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = Integer.valueOf(0); boolean b = d;"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = Long.valueOf(0); boolean b = d;"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = Float.valueOf(0); boolean b = d;"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = Double.valueOf(0); boolean b = d;"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = new ArrayList(); boolean b = d;"));
+    }
+
+    public void testdefTobyteImplicit() {
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = 'string'; byte b = d;"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = true; byte b = d;"));
+        assertEquals((byte)0, exec("def d = (byte)0; byte b = d; b"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = (short)0; byte b = d;"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = (char)0; byte b = d;"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = (int)0; byte b = d;"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = (long)0; byte b = d;"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = (float)0; byte b = d;"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = (double)0; byte b = d;"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = Boolean.valueOf(true); byte b = d;"));
+        assertEquals((byte)0, exec("def d = Byte.valueOf(0); byte b = d; b"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = Short.valueOf(0); byte b = d;"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = Character.valueOf(0); byte b = d;"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = Integer.valueOf(0); byte b = d;"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = Long.valueOf(0); byte b = d;"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = Float.valueOf(0); byte b = d;"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = Double.valueOf(0); byte b = d;"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = new ArrayList(); byte b = d;"));
+    }
+
+    public void testdefToshortImplicit() {
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = 'string'; short b = d;"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = true; short b = d;"));
+        assertEquals((short)0, exec("def d = (byte)0; short b = d; b"));
+        assertEquals((short)0, exec("def d = (short)0; short b = d; b"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = (char)0; short b = d;"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = (int)0; short b = d;"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = (long)0; short b = d;"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = (float)0; short b = d;"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = (double)0; short b = d;"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = Boolean.valueOf(true); short b = d;"));
+        assertEquals((short)0, exec("def d = Byte.valueOf(0); short b = d; b"));
+        assertEquals((short)0, exec("def d = Short.valueOf(0); short b = d; b"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = Character.valueOf(0); short b = d;"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = Integer.valueOf(0); short b = d;"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = Long.valueOf(0); short b = d;"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = Float.valueOf(0); short b = d;"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = Double.valueOf(0); short b = d;"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = new ArrayList(); short b = d;"));
+    }
+
+    public void testdefTocharImplicit() {
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = 'string'; char b = d;"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = true; char b = d;"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = (byte)0; char b = d;"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = (short)0; char b = d;"));
+        assertEquals((char)0, exec("def d = (char)0; char b = d; b"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = (int)0; char b = d;"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = (long)0; char b = d;"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = (float)0; char b = d;"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = (double)0; char b = d;"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = Boolean.valueOf(true); char b = d;"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = Byte.valueOf(0); char b = d;"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = Short.valueOf(0); char b = d;"));
+        assertEquals((char)0, exec("def d = Character.valueOf(0); char b = d; b"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = Integer.valueOf(0); char b = d;"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = Long.valueOf(0); char b = d;"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = Float.valueOf(0); char b = d;"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = Double.valueOf(0); char b = d;"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = new ArrayList(); char b = d;"));
+    }
+
+    public void testdefTointImplicit() {
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = 'string'; int b = d;"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = true; int b = d;"));
+        assertEquals(0, exec("def d = (byte)0; int b = d; b"));
+        assertEquals(0, exec("def d = (short)0; int b = d; b"));
+        assertEquals(0, exec("def d = (char)0; int b = d; b"));
+        assertEquals(0, exec("def d = 0; int b = d; b"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = (long)0; int b = d;"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = (float)0; int b = d;"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = (double)0; int b = d;"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = Boolean.valueOf(true); int b = d;"));
+        assertEquals(0, exec("def d = Byte.valueOf(0); int b = d; b"));
+        assertEquals(0, exec("def d = Short.valueOf(0); int b = d; b"));
+        assertEquals(0, exec("def d = Character.valueOf(0); int b = d; b"));
+        assertEquals(0, exec("def d = Integer.valueOf(0); int b = d; b"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = Long.valueOf(0); int b = d;"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = Float.valueOf(0); int b = d;"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = Double.valueOf(0); int b = d;"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = new ArrayList(); int b = d;"));
+    }
+
+    public void testdefTolongImplicit() {
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = 'string'; long b = d;"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = true; long b = d;"));
+        assertEquals((long)0, exec("def d = (byte)0; long b = d; b"));
+        assertEquals((long)0, exec("def d = (short)0; long b = d; b"));
+        assertEquals((long)0, exec("def d = (char)0; long b = d; b"));
+        assertEquals((long)0, exec("def d = 0; long b = d; b"));
+        assertEquals((long)0, exec("def d = (long)0; long b = d; b"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = (float)0; long b = d;"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = (double)0; long b = d;"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = Boolean.valueOf(true); long b = d;"));
+        assertEquals((long)0, exec("def d = Byte.valueOf(0); long b = d; b"));
+        assertEquals((long)0, exec("def d = Short.valueOf(0); long b = d; b"));
+        assertEquals((long)0, exec("def d = Character.valueOf(0); long b = d; b"));
+        assertEquals((long)0, exec("def d = Integer.valueOf(0); long b = d; b"));
+        assertEquals((long)0, exec("def d = Long.valueOf(0); long b = d; b"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = Float.valueOf(0); long b = d;"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = Double.valueOf(0); long b = d;"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = new ArrayList(); long b = d;"));
+    }
+
+    public void testdefTodoubleImplicit() {
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = 'string'; double b = d;"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = true; double b = d;"));
+        assertEquals((double)0, exec("def d = (byte)0; double b = d; b"));
+        assertEquals((double)0, exec("def d = (short)0; double b = d; b"));
+        assertEquals((double)0, exec("def d = (char)0; double b = d; b"));
+        assertEquals((double)0, exec("def d = 0; double b = d; b"));
+        assertEquals((double)0, exec("def d = (long)0; double b = d; b"));
+        assertEquals((double)0, exec("def d = (float)0; double b = d; b"));
+        assertEquals((double)0, exec("def d = (double)0; double b = d; b"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = Boolean.valueOf(true); double b = d;"));
+        assertEquals((double)0, exec("def d = Byte.valueOf(0); double b = d; b"));
+        assertEquals((double)0, exec("def d = Short.valueOf(0); double b = d; b"));
+        assertEquals((double)0, exec("def d = Character.valueOf(0); double b = d; b"));
+        assertEquals((double)0, exec("def d = Integer.valueOf(0); double b = d; b"));
+        assertEquals((double)0, exec("def d = Long.valueOf(0); double b = d; b"));
+        assertEquals((double)0, exec("def d = Float.valueOf(0); double b = d; b"));
+        assertEquals((double)0, exec("def d = Double.valueOf(0); double b = d; b"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = new ArrayList(); double b = d;"));
+    }
+
+    public void testdefTobooleanExplicit() {
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = 'string'; boolean b = (boolean)d;"));
+        assertEquals(true, exec("def d = true; boolean b = (boolean)d; b"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = (byte)0; boolean b = (boolean)d;"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = (short)0; boolean b = (boolean)d;"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = (char)0; boolean b = (boolean)d;"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = (int)0; boolean b = (boolean)d;"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = (long)0; boolean b = (boolean)d;"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = (float)0; boolean b = (boolean)d;"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = (double)0; boolean b = (boolean)d;"));
+        assertEquals(false, exec("def d = Boolean.valueOf(false); boolean b = (boolean)d; b"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = Byte.valueOf(0); boolean b = (boolean)d;"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = Short.valueOf(0); boolean b = (boolean)d;"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = Character.valueOf(0); boolean b = (boolean)d;"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = Integer.valueOf(0); boolean b = (boolean)d;"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = Long.valueOf(0); boolean b = (boolean)d;"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = Float.valueOf(0); boolean b = (boolean)d;"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = Double.valueOf(0); boolean b = (boolean)d;"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = new ArrayList(); boolean b = (boolean)d;"));
+    }
+
+    public void testdefTobyteExplicit() {
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = 'string'; byte b = (byte)d;"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = true; byte b = (byte)d;"));
+        assertEquals((byte)0, exec("def d = (byte)0; byte b = (byte)d; b"));
+        assertEquals((byte)0, exec("def d = (short)0; byte b = (byte)d; b"));
+        assertEquals((byte)0, exec("def d = (char)0; byte b = (byte)d; b"));
+        assertEquals((byte)0, exec("def d = 0; byte b = (byte)d; b"));
+        assertEquals((byte)0, exec("def d = (long)0; byte b = (byte)d; b"));
+        assertEquals((byte)0, exec("def d = (float)0; byte b = (byte)d; b"));
+        assertEquals((byte)0, exec("def d = (double)0; byte b = (byte)d; b"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = Boolean.valueOf(true); byte b = d;"));
+        assertEquals((byte)0, exec("def d = Byte.valueOf(0); byte b = (byte)d; b"));
+        assertEquals((byte)0, exec("def d = Short.valueOf(0); byte b = (byte)d; b"));
+        assertEquals((byte)0, exec("def d = Character.valueOf(0); byte b = (byte)d; b"));
+        assertEquals((byte)0, exec("def d = Integer.valueOf(0); byte b = (byte)d; b"));
+        assertEquals((byte)0, exec("def d = Long.valueOf(0); byte b = (byte)d; b"));
+        assertEquals((byte)0, exec("def d = Float.valueOf(0); byte b = (byte)d; b"));
+        assertEquals((byte)0, exec("def d = Double.valueOf(0); byte b = (byte)d; b"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = new ArrayList(); byte b = (byte)d;"));
+    }
+
+    public void testdefToshortExplicit() {
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = 'string'; short b = (short)d;"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = true; short b = (short)d;"));
+        assertEquals((short)0, exec("def d = (byte)0; short b = (short)d; b"));
+        assertEquals((short)0, exec("def d = (short)0; short b = (short)d; b"));
+        assertEquals((short)0, exec("def d = (char)0; short b = (short)d; b"));
+        assertEquals((short)0, exec("def d = 0; short b = (short)d; b"));
+        assertEquals((short)0, exec("def d = (long)0; short b = (short)d; b"));
+        assertEquals((short)0, exec("def d = (float)0; short b = (short)d; b"));
+        assertEquals((short)0, exec("def d = (double)0; short b = (short)d; b"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = Boolean.valueOf(true); short b = d;"));
+        assertEquals((short)0, exec("def d = Byte.valueOf(0); short b = (short)d; b"));
+        assertEquals((short)0, exec("def d = Short.valueOf(0); short b = (short)d; b"));
+        assertEquals((short)0, exec("def d = Character.valueOf(0); short b = (short)d; b"));
+        assertEquals((short)0, exec("def d = Integer.valueOf(0); short b = (short)d; b"));
+        assertEquals((short)0, exec("def d = Long.valueOf(0); short b = (short)d; b"));
+        assertEquals((short)0, exec("def d = Float.valueOf(0); short b = (short)d; b"));
+        assertEquals((short)0, exec("def d = Double.valueOf(0); short b = (short)d; b"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = new ArrayList(); short b = (short)d;"));
+    }
+
+    public void testdefTocharExplicit() {
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = 'string'; char b = (char)d;"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = true; char b = (char)d;"));
+        assertEquals((char)0, exec("def d = (byte)0; char b = (char)d; b"));
+        assertEquals((char)0, exec("def d = (short)0; char b = (char)d; b"));
+        assertEquals((char)0, exec("def d = (char)0; char b = (char)d; b"));
+        assertEquals((char)0, exec("def d = 0; char b = (char)d; b"));
+        assertEquals((char)0, exec("def d = (long)0; char b = (char)d; b"));
+        assertEquals((char)0, exec("def d = (float)0; char b = (char)d; b"));
+        assertEquals((char)0, exec("def d = (double)0; char b = (char)d; b"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = Boolean.valueOf(true); char b = d;"));
+        assertEquals((char)0, exec("def d = Byte.valueOf(0); char b = (char)d; b"));
+        assertEquals((char)0, exec("def d = Short.valueOf(0); char b = (char)d; b"));
+        assertEquals((char)0, exec("def d = Character.valueOf(0); char b = (char)d; b"));
+        assertEquals((char)0, exec("def d = Integer.valueOf(0); char b = (char)d; b"));
+        assertEquals((char)0, exec("def d = Long.valueOf(0); char b = (char)d; b"));
+        assertEquals((char)0, exec("def d = Float.valueOf(0); char b = (char)d; b"));
+        assertEquals((char)0, exec("def d = Double.valueOf(0); char b = (char)d; b"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = new ArrayList(); char b = (char)d;"));
+    }
+
+    public void testdefTointExplicit() {
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = 'string'; int b = d;"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = true; int b = (int)d;"));
+        assertEquals(0, exec("def d = (byte)0; int b = (int)d; b"));
+        assertEquals(0, exec("def d = (short)0; int b = (int)d; b"));
+        assertEquals(0, exec("def d = (char)0; int b = (int)d; b"));
+        assertEquals(0, exec("def d = 0; int b = (int)d; b"));
+        assertEquals(0, exec("def d = (long)0; int b = (int)d; b"));
+        assertEquals(0, exec("def d = (float)0; int b = (int)d; b"));
+        assertEquals(0, exec("def d = (double)0; int b = (int)d; b"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = Boolean.valueOf(true); int b = d;"));
+        assertEquals(0, exec("def d = Byte.valueOf(0); int b = (int)d; b"));
+        assertEquals(0, exec("def d = Short.valueOf(0); int b = (int)d; b"));
+        assertEquals(0, exec("def d = Character.valueOf(0); int b = (int)d; b"));
+        assertEquals(0, exec("def d = Integer.valueOf(0); int b = (int)d; b"));
+        assertEquals(0, exec("def d = Long.valueOf(0); int b = (int)d; b"));
+        assertEquals(0, exec("def d = Float.valueOf(0); int b = (int)d; b"));
+        assertEquals(0, exec("def d = Double.valueOf(0); int b = (int)d; b"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = new ArrayList(); int b = (int)d;"));
+    }
+
+    public void testdefTolongExplicit() {
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = 'string'; long b = d;"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = true; long b = (long)d;"));
+        assertEquals((long)0, exec("def d = (byte)0; long b = (long)d; b"));
+        assertEquals((long)0, exec("def d = (short)0; long b = (long)d; b"));
+        assertEquals((long)0, exec("def d = (char)0; long b = (long)d; b"));
+        assertEquals((long)0, exec("def d = 0; long b = (long)d; b"));
+        assertEquals((long)0, exec("def d = (long)0; long b = (long)d; b"));
+        assertEquals((long)0, exec("def d = (float)0; long b = (long)d; b"));
+        assertEquals((long)0, exec("def d = (double)0; long b = (long)d; b"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = Boolean.valueOf(true); long b = d;"));
+        assertEquals((long)0, exec("def d = Byte.valueOf(0); long b = (long)d; b"));
+        assertEquals((long)0, exec("def d = Short.valueOf(0); long b = (long)d; b"));
+        assertEquals((long)0, exec("def d = Character.valueOf(0); long b = (long)d; b"));
+        assertEquals((long)0, exec("def d = Integer.valueOf(0); long b = (long)d; b"));
+        assertEquals((long)0, exec("def d = Long.valueOf(0); long b = (long)d; b"));
+        assertEquals((long)0, exec("def d = Float.valueOf(0); long b = (long)d; b"));
+        assertEquals((long)0, exec("def d = Double.valueOf(0); long b = (long)d; b"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = new ArrayList(); long b = (long)d;"));
+    }
+
+    public void testdefTofloatExplicit() {
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = 'string'; float b = d;"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = true; float b = (float)d;"));
+        assertEquals((float)0, exec("def d = (byte)0; float b = (float)d; b"));
+        assertEquals((float)0, exec("def d = (short)0; float b = (float)d; b"));
+        assertEquals((float)0, exec("def d = (char)0; float b = (float)d; b"));
+        assertEquals((float)0, exec("def d = 0; float b = (float)d; b"));
+        assertEquals((float)0, exec("def d = (long)0; float b = (float)d; b"));
+        assertEquals((float)0, exec("def d = (float)0; float b = (float)d; b"));
+        assertEquals((float)0, exec("def d = (double)0; float b = (float)d; b"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = Boolean.valueOf(true); float b = d;"));
+        assertEquals((float)0, exec("def d = Byte.valueOf(0); float b = (float)d; b"));
+        assertEquals((float)0, exec("def d = Short.valueOf(0); float b = (float)d; b"));
+        assertEquals((float)0, exec("def d = Character.valueOf(0); float b = (float)d; b"));
+        assertEquals((float)0, exec("def d = Integer.valueOf(0); float b = (float)d; b"));
+        assertEquals((float)0, exec("def d = Long.valueOf(0); float b = (float)d; b"));
+        assertEquals((float)0, exec("def d = Float.valueOf(0); float b = (float)d; b"));
+        assertEquals((float)0, exec("def d = Double.valueOf(0); float b = (float)d; b"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = new ArrayList(); float b = (float)d;"));
+    }
+
+    public void testdefTodoubleExplicit() {
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = 'string'; double b = d;"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = true; double b = (double)d;"));
+        assertEquals((double)0, exec("def d = (byte)0; double b = (double)d; b"));
+        assertEquals((double)0, exec("def d = (short)0; double b = (double)d; b"));
+        assertEquals((double)0, exec("def d = (char)0; double b = (double)d; b"));
+        assertEquals((double)0, exec("def d = 0; double b = (double)d; b"));
+        assertEquals((double)0, exec("def d = (long)0; double b = (double)d; b"));
+        assertEquals((double)0, exec("def d = (float)0; double b = (double)d; b"));
+        assertEquals((double)0, exec("def d = (double)0; double b = (double)d; b"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = Boolean.valueOf(true); double b = d;"));
+        assertEquals((double)0, exec("def d = Byte.valueOf(0); double b = (double)d; b"));
+        assertEquals((double)0, exec("def d = Short.valueOf(0); double b = (double)d; b"));
+        assertEquals((double)0, exec("def d = Character.valueOf(0); double b = (double)d; b"));
+        assertEquals((double)0, exec("def d = Integer.valueOf(0); double b = (double)d; b"));
+        assertEquals((double)0, exec("def d = Long.valueOf(0); double b = (double)d; b"));
+        assertEquals((double)0, exec("def d = Float.valueOf(0); double b = (double)d; b"));
+        assertEquals((double)0, exec("def d = Double.valueOf(0); double b = (double)d; b"));
+        expectScriptThrows(ClassCastException.class, () -> exec("def d = new ArrayList(); double b = (double)d;"));
+    }
+}