[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, 15 insertions, 2 deletions

diff --git a/test/files/run/virtpatmat_partial.check b/test/files/run/virtpatmat_partial.check
index 1555eca82b..137d16da79 100644
--- a/test/files/run/virtpatmat_partial.check
+++ b/test/files/run/virtpatmat_partial.check
@@ -1,4 +1,17 @@
 Map(a -> Some(1), b -> None)
-79
-undefined
 Map(a -> 1)
+a
+undefined
+a
+undefined
+a
+undefined
+a
+undefined
+hai!
+hai!
+2
+hai!
+undefined
+1
+undefined