Grails AST Transformation "unable to find class" error

I'm trying to implement AST Transformation in a grails project.

I get the following error when i run grails clean and grails compile. I dont know where i am going wrong, it is working fine in a sample groovy project.

Compilation error: startup failed:
/home/manoj/grailsgradle/ast/grails-app/controllers/ast/AstController.groovy: 12: unable to resolve class WithLogging ,  unable to find class for annotation
 @ line 12, column 5.
       @WithLogging

I have created two files namely WithLogging and WithLoggingASTTransformation in /src/ast/ of the grails project directory.

WithLogging:

package ast

import org.codehaus.groovy.transform.GroovyASTTransformationClass

import java.lang.annotation.ElementType
import java.lang.annotation.Retention
import java.lang.annotation.RetentionPolicy
import java.lang.annotation.Target

@Retention(RetentionPolicy.SOURCE)
@Target([ElementType.METHOD])
@GroovyASTTransformationClass(["WithLoggingASTTransformation"])
public @interface WithLogging {}

WithLoggingASTTransformation :

package ast
import org.codehaus.groovy.ast.ASTNode
import org.codehaus.groovy.control.CompilePhase
import org.codehaus.groovy.control.SourceUnit
import org.codehaus.groovy.transform.ASTTransformation
import org.codehaus.groovy.transform.GroovyASTTransformation

@GroovyASTTransformation(phase = CompilePhase.CANONICALIZATION)
class WithLoggingASTTransformation implements ASTTransformation {

    @Override
    void visit(ASTNode[] nodes, SourceUnit sourceUnit) {

        println("******* inside ast *******")


    }
}

I have create a script in /scripts called _Events.groovy

eventCompileStart = {
    compileAST("/home/manoj/grailsgradle/ast", "/home/manoj/grailsgradle/ast/target/")
}

def compileAST(def srcBaseDir, def destDir) {
    ant.sequential {

        println "Precompiling AST Transformations ..."
        println "src ${srcBaseDir} ${destDir}"
        path id: "grails.compile.classpath", compileClasspath
        def classpathId = "grails.compile.classpath"
        mkdir dir: destDir

        groovyc(destdir: destDir,
                srcDir: "$srcBaseDir/src/ast",
                classpathref: classpathId,
                verbose: grailsSettings.verboseCompile,
                stacktrace: "yes",
                encoding: "UTF-8")



        echo "done precompiling AST Transformations"
    }
}

In /controllers/ast, i have created a controller AstController

package ast

class AstController {

    def index() {

        loggedMethod()

    }

    @WithLogging
    def loggedMethod() {
        println "i am doing some important stuff!"
    }
}