Add some basic compile-time checks to enforce usage of `T{...}` within traits

1 files changed, 28 insertions, 0 deletions

diff --git a/core/src/main/scala/forge/util/LocalDef.scala b/core/src/main/scala/forge/util/LocalDef.scala
new file mode 100644
index 00000000..2a58bbd2
--- /dev/null
+++ b/core/src/main/scala/forge/util/LocalDef.scala
@@ -0,0 +1,28 @@
+package forge.util
+
+import scala.reflect.macros.blackbox
+import language.experimental.macros
+class LocalDef
+object LocalDef {
+  implicit def default: LocalDef = macro enclosing
+  def enclosing(c: blackbox.Context): c.Expr[LocalDef] = {
+
+    import c.universe._
+    val current = c.internal.enclosingOwner
+
+    if (
+      !current.isMethod ||
+      // We can't do this right now because it causes recursive method errors
+      // current.asMethod.paramLists.nonEmpty ||
+      !(current.owner.isClass || current.owner.isModuleClass)
+    ) {
+      c.abort(
+        c.enclosingPosition,
+        "T{} can only be used directly within a zero-arg method defined in a class body"
+      )
+    }else{
+
+      c.Expr[LocalDef](q"""new forge.util.LocalDef()""")
+    }
+  }
+}