[vpm] typer synths Function{} for empty-sel match

typedMatchAnonFun is called from typedFunction when the function's body is a match

this is work-in-progres: the compiler currently won't bootstrap under -Yvirtpatmat
see also the pending test

make sure to use the right context in typeFunction when the body is a Match
when typer is set up for type checking a Function, the current owner is the symbol for the function,
but we'll type check a Block(List(ClassDef(cd)), New(cd)) when the function is a match,
and the function symbol is nowhere to be found, so go to outer context

in patmatvirt:
- simplified default case gen (no need for a Casegen instance)
- using CASE | SYNTHETIC to detect generated matches (for switches) and avoid typing them endlessly
  more uniform, and necessary for new-style anon Function class instance gen for matches

1 files changed, 3 insertions, 2 deletions

diff --git a/src/compiler/scala/reflect/internal/Trees.scala b/src/compiler/scala/reflect/internal/Trees.scala
index 9b1712b790..1a40e0105c 100644
--- a/src/compiler/scala/reflect/internal/Trees.scala
+++ b/src/compiler/scala/reflect/internal/Trees.scala
@@ -350,8 +350,9 @@ trait Trees extends api.Trees { self: SymbolTable =>
     "subst[%s, %s](%s)".format(fromStr, toStr, (from, to).zipped map (_ + " -> " + _) mkString ", ")
   }
 
-  // NOTE: if symbols in `from` occur multiple times in the `tree` passed to `transform`,
-  // the resulting Tree will be a graph, not a tree... this breaks all sorts of stuff,
+  // NOTE: calls shallowDuplicate on trees in `to` to avoid problems when symbols in `from`
+  // occur multiple times in the `tree` passed to `transform`,
+  // otherwise, the resulting Tree would be a graph, not a tree... this breaks all sorts of stuff,
   // notably concerning the mutable aspects of Trees (such as setting their .tpe)
   class TreeSubstituter(from: List[Symbol], to: List[Tree]) extends Transformer {
     override def transform(tree: Tree): Tree = tree match {