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POCreating a method definition tree from a method symbol and a body
 

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    <p>Is there a convenient way to turn a <a href="http://www.scala-lang.org/archives/downloads/distrib/files/nightly/docs/library/index.html#scala.reflect.api.Symbols$MethodSymbolApi" rel="nofollow noreferrer"><code>MethodSymbol</code></a> into the left-hand side of a method definition tree (i.e., a <a href="http://www.scala-lang.org/archives/downloads/distrib/files/nightly/docs/library/index.html#scala.reflect.api.Trees$DefDefApi" rel="nofollow noreferrer"><code>DefDef</code></a>) in Scala 2.10?</p> <p>For example, suppose I want to create a macro that will take an instance of a trait and wrap all of that trait's methods with some debugging functionality. I can write the following:</p> <pre><code>import scala.language.experimental.macros import scala.reflect.macros.Context object WrapperExample { def wrap[A](a: A): A = macro wrap_impl[A] def wrap_impl[A: c.WeakTypeTag](c: Context)(a: c.Expr[A]) = { import c.universe._ val wrapped = weakTypeOf[A] val f = Select(reify(Predef).tree, "println") val methods = wrapped.declarations.collect { case m: MethodSymbol if !m.isConstructor =&gt; DefDef( Modifiers(Flag.OVERRIDE), m.name, Nil, Nil, TypeTree(), Block( Apply(f, c.literal("Calling: " + m.name.decoded).tree :: Nil), Select(a.tree, m.name) ) ) }.toList //... } </code></pre> <p>I've elided the boring business of sticking these methods in a new anonymous class that implements the trait and then instantiating that class—you can find a complete working example <a href="https://gist.github.com/4234441" rel="nofollow noreferrer">here</a> if you're interested.</p> <p>Now I can write this, for example:</p> <pre><code>scala&gt; trait X { def foo = 1; def bar = 'a } defined trait X scala&gt; val x = new X {} x: X = $anon$1@15dd533 scala&gt; val w: X = WrapperExample.wrap[X](x) w: X = $1$$1@27c3a4a3 scala&gt; w.foo Calling: foo res0: Int = 1 scala&gt; w.bar Calling: bar res1: Symbol = 'a </code></pre> <p>So it works, but only in very simple cases—it won't if the trait has methods with parameter lists, with access modifiers, annotations, etc.</p> <p>What I really want is a function that will take a method symbol and a tree for the new body and return a <code>DefDef</code>. I've started writing one by hand, but it involves a lot of fiddly stuff like this:</p> <pre><code>List(if (method.isImplicit) Some(Flag.IMPLICIT) else None, ...) </code></pre> <p>Which is annoying, verbose, and error-prone. Am I missing some nicer way to do this in the new Reflection API?</p>
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