Building Groovy from source gives 5 warning messages from javac about deprecated methods - enabling the <deprecation> parameter to the <javac> task (see below) reveals that all of these messages are the result of meta class implementations extending or implementing a deprecated method without declaring that the method is deprecated. The fix is very simple - just add the missing @deprecated declaration to DelegatingMetaClass (invokeConstructorAt), ProxyMetaClass (invokeMethod), and MockProxyMetaClass (invokeMethod). The confusing warning message for GPathResult.java will disappear as a result of fixing DelegatingMetaClass, which is extended by an anonymous inner class, resulting in the warning message that the compiler bizarrely associates with the declaration of the setAttribute method! [javac] [...]/groovy-core/src/main/groovy/lang/DelegatingMetaClass.java:185: warning: [deprecation] invokeConstructorAt(java.lang.Class,java.lang.Object[]) in groovy.lang.MetaClass has been deprecated [javac] public Object invokeConstructorAt(Class at, Object[] arguments) { [javac] ^ [javac] [...]//groovy-core/src/main/groovy/lang/DelegatingMetaClass.java:186: warning: [deprecation] invokeConstructorAt(java.lang.Class,java.lang.Object[]) in groovy.lang.MetaClass has been deprecated [javac] return this.delegate.invokeConstructorAt(at, arguments); [javac] ^ [javac] [...]//groovy-core/src/main/groovy/lang/ProxyMetaClass.java:117: warning: [deprecation] invokeMethod(java.lang.Object,java.lang.String,java.lang.Object[]) in groovy.lang.MetaClassImpl has been deprecated [javac] public Object invokeMethod(final Object object, final String methodName, final Object[] arguments) { [javac] ^ [javac] [...]//groovy-core/src/main/groovy/mock/interceptor/MockProxyMetaClass.java:32: warning: [deprecation] invokeMethod(java.lang.Object,java.lang.String,java.lang.Object[]) in groovy.lang.MetaClassImpl has been deprecated [javac] public Object invokeMethod(final Object object, final String methodName, final Object[] arguments) { [javac] ^ [javac] [...]//groovy-core/src/main/groovy/util/slurpersupport/GPathResult.java:93: warning: [deprecation] invokeConstructorAt(java.lang.Class,java.lang.Object[]) in groovy.lang.MetaClass has been deprecated [javac] public void setAttribute(final Object object, final String attribute, final Object newValue) { [javac] ^ [javac] 5 warnings [echo] Groovyc of main code.