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, 4 insertions, 4 deletions

diff --git a/src/dotty/tools/dotc/typer/Namer.scala b/src/dotty/tools/dotc/typer/Namer.scala
index c522a5998..4bf194f5e 100644
--- a/src/dotty/tools/dotc/typer/Namer.scala
+++ b/src/dotty/tools/dotc/typer/Namer.scala
@@ -436,9 +436,9 @@ class Namer { typer: Typer =>
 
     protected implicit val ctx: Context = localContext(cls).setMode(ictx.mode &~ Mode.InSuperCall)
 
-    val TypeDef(name, impl @ Template(constr, parents, self, body)) = original
+    val TypeDef(name, impl @ Template(constr, parents, self, _)) = original
 
-    val (params, rest) = body span {
+    val (params, rest) = impl.body span {
       case td: TypeDef => td.mods is Param
       case td: ValDef => td.mods is ParamAccessor
       case _ => false
@@ -496,9 +496,9 @@ class Namer { typer: Typer =>
       index(rest)(inClassContext(selfInfo))
       denot.info = ClassInfo(cls.owner.thisType, cls, parentRefs, decls, selfInfo)
       if (cls is Trait) {
-        if (body forall isNoInitMember) {
+        if (impl.body forall isNoInitMember) {
           cls.setFlag(NoInits)
-          if (body forall isPureInterfaceMember)
+          if (impl.body forall isPureInterfaceMember)
             cls.setFlag(PureInterface)
         }
       }