Made the squeezer worthy of its name: a block w...

Made the squeezer worthy of its name: a block with an empty list of
stats and another block as the result expression is rewritten to the
inner block (recursively). This makes the output from the pattern
matcher nicer, eliminating loads of empty nested blocks. Review by
extempore.

1 files changed, 9 insertions, 2 deletions

diff --git a/src/compiler/scala/tools/nsc/matching/MatrixAdditions.scala b/src/compiler/scala/tools/nsc/matching/MatrixAdditions.scala
index 23944c91d9..74de20de4a 100644
--- a/src/compiler/scala/tools/nsc/matching/MatrixAdditions.scala
+++ b/src/compiler/scala/tools/nsc/matching/MatrixAdditions.scala
@@ -30,9 +30,16 @@ trait MatrixAdditions extends ast.TreeDSL
     def squeezedBlockPVs(pvs: List[PatternVar], exp: Tree): Tree =
       squeezedBlock(pvs map (_.valDef), exp)
 
+    def mkBlock(stats: List[Tree], expr: Tree): Tree =
+      if (stats.isEmpty) expr match {
+        case Block(stats1, expr1) => mkBlock(stats1, expr1)
+        case _ => Block(stats, expr)
+      } else
+        Block(stats, expr)
+
     def squeezedBlock(vds: List[Tree], exp: Tree): Tree =
-      if (settings_squeeze) Block(Nil, squeezedBlock1(vds, exp))
-      else                  Block(vds, exp)
+      if (settings_squeeze) mkBlock(Nil, squeezedBlock1(vds, exp))
+      else                  mkBlock(vds, exp)
 
     private def squeezedBlock1(vds: List[Tree], exp: Tree): Tree = {
       class RefTraverser(sym: Symbol) extends Traverser {