Merge pull request #1881 from dotty-staging/add-structural-select

Implement structural type member access

2 files changed, 81 insertions, 0 deletions

diff --git a/library/src/scala/Selectable.scala b/library/src/scala/Selectable.scala
new file mode 100644
index 000000000..c5c714ca9
--- /dev/null
+++ b/library/src/scala/Selectable.scala
@@ -0,0 +1,8 @@
+package scala
+import scala.reflect.ClassTag
+
+trait Selectable extends Any {
+  def selectDynamic(name: String): Any
+  def selectDynamicMethod(name: String, paramClasses: ClassTag[_]*): Any =
+    new UnsupportedOperationException("selectDynamicMethod")
+}
diff --git a/library/src/scala/reflect/Selectable.scala b/library/src/scala/reflect/Selectable.scala
new file mode 100644
index 000000000..0dbdbc293
--- /dev/null
+++ b/library/src/scala/reflect/Selectable.scala
@@ -0,0 +1,73 @@
+package scala.reflect
+
+class Selectable(val receiver: Any) extends AnyVal with scala.Selectable {
+  def selectDynamic(name: String): Any = {
+    val rcls = receiver.getClass
+    try {
+      val fld = rcls.getField(name)
+      fld.get(receiver)
+    }
+    catch {
+      case ex: NoSuchFieldError =>
+        selectDynamicMethod(name).asInstanceOf[() => Any]()
+    }
+  }
+
+  override def selectDynamicMethod(name: String, paramTypes: ClassTag[_]*): Any = {
+    val rcls = receiver.getClass
+    val paramClasses = paramTypes.map(_.runtimeClass)
+    val mth = rcls.getMethod(name, paramClasses: _*)
+    paramTypes.length match {
+      case 0 => () =>
+        mth.invoke(receiver)
+      case 1 => (x0: Any) =>
+        mth.invoke(receiver, x0.asInstanceOf[Object])
+      case 2 => (x0: Any, x1: Any) =>
+        mth.invoke(receiver,
+            x0.asInstanceOf[Object],
+            x1.asInstanceOf[Object])
+      case 3 => (x0: Any, x1: Any, x2: Any) =>
+        mth.invoke(receiver,
+            x0.asInstanceOf[Object],
+            x1.asInstanceOf[Object],
+            x2.asInstanceOf[Object])
+      case 4 => (x0: Any, x1: Any, x2: Any, x3: Any) =>
+        mth.invoke(receiver,
+            x0.asInstanceOf[Object],
+            x1.asInstanceOf[Object],
+            x2.asInstanceOf[Object],
+            x3.asInstanceOf[Object])
+      case 5 => (x0: Any, x1: Any, x2: Any, x3: Any, x4: Any) =>
+        mth.invoke(receiver,
+            x0.asInstanceOf[Object],
+            x1.asInstanceOf[Object],
+            x2.asInstanceOf[Object],
+            x3.asInstanceOf[Object],
+            x4.asInstanceOf[Object])
+      case 6 => (x0: Any, x1: Any, x2: Any, x3: Any, x4: Any, x5: Any) =>
+        mth.invoke(receiver,
+            x0.asInstanceOf[Object],
+            x1.asInstanceOf[Object],
+            x2.asInstanceOf[Object],
+            x3.asInstanceOf[Object],
+            x4.asInstanceOf[Object],
+            x5.asInstanceOf[Object])
+      case 7 => (x0: Any, x1: Any, x2: Any, x3: Any, x4: Any, x5: Any, x6: Any) =>
+        mth.invoke(receiver,
+            x0.asInstanceOf[Object],
+            x1.asInstanceOf[Object],
+            x2.asInstanceOf[Object],
+            x3.asInstanceOf[Object],
+            x4.asInstanceOf[Object],
+            x5.asInstanceOf[Object],
+            x6.asInstanceOf[Object])
+      }
+  }
+}
+
+object Selectable {
+  implicit def reflectiveSelectable(receiver: Any): scala.Selectable = receiver match {
+    case receiver: scala.Selectable => receiver
+    case _                          => new Selectable(receiver)
+  }
+}