fixes incorrect handling of Annotated in lazy copier

src/reflect/scala/reflect/internal/Trees.scala

@@ -811,7 +811,7 @@ trait Trees extends api.Trees { self: SymbolTable =>
     }
     def Annotated(tree: Tree, annot: Tree, arg: Tree) = tree match {
       case t @ Annotated(annot0, arg0)
-      if (annot0==annot) => t
+      if (annot0==annot && arg0==arg) => t
       case _ => treeCopy.Annotated(tree, annot, arg)
     }
     def SingletonTypeTree(tree: Tree, ref: Tree) = tree match {

test/files/pos/annotated-treecopy.flags

@@ -0,0 +1 @@
+-language:experimental.macros

test/files/pos/annotated-treecopy/Impls_Macros_1.scala

@@ -0,0 +1,53 @@
+import scala.language.experimental.macros
+import scala.reflect.macros.Context
+import collection.mutable.ListBuffer
+import collection.mutable.Stack
+
+object Macros {
+  trait TypedFunction {
+    def tree: scala.reflect.runtime.universe.Tree
+    val typeIn: String
+    val typeOut: String
+  }
+
+  def tree[T,U](f:Function1[T,U]): Function1[T,U] = macro tree_impl[T,U]
+
+  def tree_impl[T:c.WeakTypeTag,U:c.WeakTypeTag](c: Context)
+      (f:c.Expr[Function1[T,U]]): c.Expr[Function1[T,U]] = {
+    import c.universe._
+    val ttag = c.weakTypeTag[U]
+    f match {
+      case Expr(Function(List(ValDef(_,n,tp,_)),b)) =>
+        // normalize argument name
+        var b1 = new Transformer {
+          override def transform(tree: Tree): Tree = tree match {
+            case Ident(x) if (x==n) => Ident(newTermName("_arg"))
+            case tt @ TypeTree() if tt.original != null => TypeTree(tt.tpe) setOriginal transform(tt.original)
+            // without the fix to LazyTreeCopier.Annotated, we would need to uncomment the line below to make the macro work
+            // that's because the pattern match in the input expression gets expanded into Typed(<x>, TypeTree(<Int @unchecked>))
+            // with the original of the TypeTree being Annotated(<@unchecked>, Ident(<x>))
+            // then the macro tries to replace all Ident(<x>) trees with Ident(<_arg>), recurs into the original of the TypeTree, changes it,
+            // but leaves the <@unchecked> part untouched. this signals the misguided LazyTreeCopier that the Annotated tree hasn't been modified,
+            // so the original tree should be copied over and returned => crash when later <x: @unchecked> re-emerges from TypeTree.original
+            // case Annotated(annot, arg) => treeCopy.Annotated(tree, transform(annot).duplicate, transform(arg))
+            case _ => super.transform(tree)
+          }
+        }.transform(b)
+
+        val reifiedTree = c.reifyTree(treeBuild.mkRuntimeUniverseRef, EmptyTree, b1)
+        val reifiedExpr = c.Expr[scala.reflect.runtime.universe.Expr[T => U]](reifiedTree)
+        val template =
+          c.universe.reify(new (T => U) with TypedFunction {
+            override def toString = c.literal(tp+" => "+ttag.tpe+" { "+b1.toString+" } ").splice // DEBUG
+            def tree = reifiedExpr.splice.tree
+            val typeIn = c.literal(tp.toString).splice
+            val typeOut = c.literal(ttag.tpe.toString).splice
+            def apply(_arg: T): U = c.Expr[U](b1)(ttag.asInstanceOf[c.WeakTypeTag[U]]).splice
+          })
+        val untyped = c.resetLocalAttrs(template.tree)
+
+        c.Expr[T => U](untyped)
+      case _ => sys.error("Bad function type")
+    }
+  }
+}

test/files/pos/annotated-treecopy/Test_2.scala

@@ -0,0 +1,5 @@
+object Test extends App {
+  import Macros._
+  // tree { (x:((Int,Int,Int),(Int,Int,Int))) => { val y=x; val ((r1,m1,c1),(r2,m2,c2))=y; (r1, m1 + m2 + r1 * c1 * c2, c2) } }
+  tree { (x:((Int,Int,Int),(Int,Int,Int))) => { val ((r1,m1,c1),(r2,m2,c2))=x; (r1, m1 + m2 + r1 * c1 * c2, c2) } }
+}