scala> import reflect.macros.Context
import reflect.macros.Context

scala> abstract class MacroBase {
     |   def macroImpl[T: c.WeakTypeTag](c: Context)(body: c.Expr[T]): c.Expr[Any] = c.universe.reify(body.splice)
     | }
defined class MacroBase

scala> object Macro extends MacroBase {
     |   def macroDecl[T](body: T) = macro macroImpl[T]
     | }
defined module Macro

scala> Macro.macroDecl(0)
error: macro implementation not found: macroDecl (the most common reason for that is that you cannot use macro implementations in the same compilation run that defines them)

scala> import reflect.macros.Context
import reflect.macros.Context

scala> abstract class MacroBase {
     |   def macroImpl[T: c.WeakTypeTag](c: Context)(body: c.Expr[T]): c.Expr[Any] = c.universe.reify(body.splice)
     | }
defined class MacroBase

scala> object Macro extends MacroBase {
     |   def macroDecl[T](body: T) = macro macroImpl[T]
     |   override def macroImpl[T: c.WeakTypeTag](c: Context)(body: c.Expr[T]): c.Expr[Any] = super.macroImpl[T](c)(body)
     | }
defined module Macro

scala> Macro.macroDecl(0)
res2: Int = 0