Make some tree fields lazy

Lazy fields are
 - the rhs field of a ValDef or DefDef
 - the body field of a Template

These can be instantiated with Lazy instances.
The scheme is such that lazy fields are completely
transparent for users of the Trees API.

The only downside is that the parameter used to initialize
a potentially lazy field has a weak type (now it's Any, with
Dotty it would be a union type of the form `T | Lazy[T]`.
Therefore, the parameter cannot be recovered through pattern
matching.

1 files changed, 2 insertions, 2 deletions

diff --git a/src/dotty/tools/dotc/transform/MacroTransform.scala b/src/dotty/tools/dotc/transform/MacroTransform.scala
index 3a8bcc920..0f57c3ff5 100644
--- a/src/dotty/tools/dotc/transform/MacroTransform.scala
+++ b/src/dotty/tools/dotc/transform/MacroTransform.scala
@@ -58,12 +58,12 @@ abstract class MacroTransform extends Phase {
           tree
         case _: PackageDef | _: MemberDef =>
           super.transform(tree)(localCtx(tree))
-        case Template(constr, parents, self, body) =>
+        case impl @ Template(constr, parents, self, _) =>
           cpy.Template(tree)(
             transformSub(constr),
             transform(parents)(ctx.superCallContext),
             transformSelf(self),
-            transformStats(body, tree.symbol))
+            transformStats(impl.body, tree.symbol))
         case _ =>
           super.transform(tree)
       }