Avoid ObjectRefs in the compiler and fix a historical quirk of pattern matcher

project/ScriptCommands.scala

@@ -122,7 +122,7 @@ object ScriptCommands {
   }
 
   val enableOptimizer = Seq(
-    scalacOptions in Compile in ThisBuild ++= Seq("-opt:l:inline", "-opt-inline-from:scala/**")
+    scalacOptions in Compile in ThisBuild ++= Seq("-opt:l:inline,omit-pattern-vars", "-opt-inline-from:scala/**")
   )
 
   val noDocs = Seq(

src/compiler/scala/tools/nsc/settings/ScalaSettings.scala

@@ -276,6 +276,7 @@ trait ScalaSettings extends AbsScalaSettings
     val compactLocals           = Choice("compact-locals",            "Eliminate empty slots in the sequence of local variables.")
     val copyPropagation         = Choice("copy-propagation",          "Eliminate redundant local variables and unused values (including closures). Enables unreachable-code.")
     val redundantCasts          = Choice("redundant-casts",           "Eliminate redundant casts using a type propagation analysis.")
+    val omitPatternVars         = Choice("omit-pattern-vars",         "Omit local variables in pattern translation and repeat selection from accessors.")
     val boxUnbox                = Choice("box-unbox",                 "Eliminate box-unbox pairs within the same method (also tuples, xRefs, value class instances). Enables unreachable-code.")
     val nullnessTracking        = Choice("nullness-tracking",         "Track nullness / non-nullness of local variables and apply optimizations.")
     val closureInvocations      = Choice("closure-invocations" ,      "Rewrite closure invocations to the implementation method.")
@@ -341,6 +342,7 @@ trait ScalaSettings extends AbsScalaSettings
   def optNullnessTracking        = optEnabled(optChoices.nullnessTracking)
   def optClosureInvocations      = optEnabled(optChoices.closureInvocations)
   def optInlinerEnabled          = optEnabled(optChoices.inline)
+  def optOmitPatternVars         = optEnabled(optChoices.omitPatternVars)
 
   // deprecated inliner levels
   def optLProject                = optEnabled(optChoices.lProject)

src/compiler/scala/tools/nsc/transform/patmat/MatchTreeMaking.scala

@@ -131,7 +131,7 @@ trait MatchTreeMaking extends MatchCodeGen with Debugging {
     }
 
     // unless we're optimizing, emit local variable bindings for all subpatterns of extractor/case class patterns
-    protected val debugInfoEmitVars = !settings.optimise.value
+    protected val debugInfoEmitVars = !(settings.optimise.value || settings.optOmitPatternVars)
 
     sealed trait PreserveSubPatBinders extends TreeMaker {
       val subPatBinders: List[Symbol]

versions.properties

@@ -1,5 +1,5 @@
 # Scala version used for bootstrapping (see README.md)
-starr.version=2.12.9
+starr.version=2.12.10-bin-584e5bc-SNAPSHOT
 
 # The scala.binary.version determines how modules are resolved. It is set as follows:
 #  - After 2.x.0 is released, the binary version is 2.x