1 files changed, 48 insertions, 0 deletions
diff --git a/src/library/scala/reflect/api/Exprs.scala b/src/library/scala/reflect/api/Exprs.scala
new file mode 100644
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+++ b/src/library/scala/reflect/api/Exprs.scala
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+/* NSC -- new Scala compiler
+ * Copyright 2005-2011 LAMP/EPFL
+ * @author  Martin Odersky
+ */
+
+package scala.reflect
+package api
+
+trait Exprs { self: Universe =>
+
+  /** An expression tree tagged with its type */
+  case class Expr[+T: TypeTag](tree: Tree) {
+    def tpe: Type = implicitly[TypeTag[T]].tpe
+    def eval: T = mkToolBox().runExpr(tree).asInstanceOf[T]
+    lazy val value: T = eval
+    override def toString = "Expr["+tpe+"]("+tree+")"
+  }
+
+  // [Eugene] had to move this to the companion of Tree to make stuff compile. weirdo!
+//  object Expr {
+//    // would be great if in future this generated an Expr[Magic]
+//    // where Magic is a magic untyped type that propagates through the entire quasiquote
+//    // and turns off typechecking whenever it's involved
+//    // that'd allow us to splice trees into quasiquotes and still have these qqs to be partially typechecked
+//    // see some exploration of these ideas here: https://github.com/xeno-by/alphakeplerdemo
+//    implicit def tree2expr(tree: Tree): Expr[Nothing] = Expr[Nothing](tree)
+//    implicit def expr2tree(expr: Expr[_]): Tree = expr.tree
+//
+//    // [Eugene] good idea?
+//    implicit def trees2exprs(trees: List[Tree]): List[Expr[Nothing]] = trees map tree2expr
+//    implicit def exprs2trees(exprs: List[Expr[_]]): List[Tree] = exprs map expr2tree
+//  }
+
+  // [Eugene] even weirder - implicits didn't feel at home in Trees :(
+
+  // would be great if in future this generated an Expr[Magic]
+  // where Magic is a magic untyped type that propagates through the entire quasiquote
+  // and turns off typechecking whenever it's involved
+  // that'd allow us to splice trees into quasiquotes and still have these qqs to be partially typechecked
+  // see some exploration of these ideas here: https://github.com/xeno-by/alphakeplerdemo
+  implicit def tree2expr(tree: Tree): Expr[Nothing] = Expr[Nothing](tree)(TypeTag.Nothing)
+  implicit def expr2tree(expr: Expr[_]): Tree = expr.tree
+
+  // [Eugene] good idea?
+  implicit def trees2exprs(trees: List[Tree]): List[Expr[Nothing]] = trees map tree2expr
+  implicit def exprs2trees(exprs: List[Expr[_]]): List[Tree] = exprs map expr2tree
+}
+