Cleanup `LinkedHashSet` fixes and replace them with `Set` (i.e., back

to initial implementation).

Assuming that the DPLL procedure does not run into max recursion
depth, that workaround is not needed anymore, since the non-
determinism has been fixed.

2 files changed, 14 insertions, 22 deletions

diff --git a/src/compiler/scala/tools/nsc/transform/patmat/Logic.scala b/src/compiler/scala/tools/nsc/transform/patmat/Logic.scala
index 3331805c1b..e6ddf8b758 100644
--- a/src/compiler/scala/tools/nsc/transform/patmat/Logic.scala
+++ b/src/compiler/scala/tools/nsc/transform/patmat/Logic.scala
@@ -87,7 +87,7 @@ trait Logic extends Debugging  {
       def mayBeNull: Boolean
 
       // compute the domain and return it (call registerNull first!)
-      def domainSyms: Option[mutable.LinkedHashSet[Sym]]
+      def domainSyms: Option[Set[Sym]]
 
       // the symbol for this variable being equal to its statically known type
       // (only available if registerEquality has been called for that type before)
@@ -205,7 +205,7 @@ trait Logic extends Debugging  {
     def removeVarEq(props: List[Prop], modelNull: Boolean = false): (Formula, List[Formula]) = {
       val start = if (Statistics.canEnable) Statistics.startTimer(patmatAnaVarEq) else null
 
-      val vars = mutable.LinkedHashSet[Var]()
+      val vars = new mutable.HashSet[Var]
 
       object gatherEqualities extends PropTraverser {
         override def apply(p: Prop) = p match {
@@ -292,7 +292,7 @@ trait Logic extends Debugging  {
     def eqFreePropToSolvable(p: Prop): Formula
     def cnfString(f: Formula): String
 
-    type Model = collection.immutable.SortedMap[Sym, Boolean]
+    type Model = Map[Sym, Boolean]
     val EmptyModel: Model
     val NoModel: Model
 
@@ -342,9 +342,9 @@ trait ScalaLogic extends Interface with Logic with TreeAndTypeAnalysis {
       // we enumerate the subtypes of the full type, as that allows us to filter out more types statically,
       // once we go to run-time checks (on Const's), convert them to checkable types
       // TODO: there seems to be bug for singleton domains (variable does not show up in model)
-      lazy val domain: Option[mutable.LinkedHashSet[Const]] = {
-        val subConsts: Option[mutable.LinkedHashSet[Const]] = enumerateSubtypes(staticTp).map { tps =>
-          mutable.LinkedHashSet(tps: _*).map{ tp =>
+      lazy val domain: Option[Set[Const]] = {
+        val subConsts = enumerateSubtypes(staticTp).map{ tps =>
+          tps.toSet[Type].map{ tp =>
             val domainC = TypeConst(tp)
             registerEquality(domainC)
             domainC
@@ -487,7 +487,7 @@ trait ScalaLogic extends Interface with Logic with TreeAndTypeAnalysis {
       }
 
       // accessing after calling registerNull will result in inconsistencies
-      lazy val domainSyms: Option[collection.mutable.LinkedHashSet[Sym]] = domain map { _ map symForEqualsTo }
+      lazy val domainSyms: Option[Set[Sym]] = domain map { _ map symForEqualsTo }
 
       lazy val symForStaticTp: Option[Sym]  = symForEqualsTo.get(TypeConst(staticTpCheckable))
 
diff --git a/src/compiler/scala/tools/nsc/transform/patmat/Solving.scala b/src/compiler/scala/tools/nsc/transform/patmat/Solving.scala
index 0d867be4b6..4330781013 100644
--- a/src/compiler/scala/tools/nsc/transform/patmat/Solving.scala
+++ b/src/compiler/scala/tools/nsc/transform/patmat/Solving.scala
@@ -26,16 +26,9 @@ trait Solving extends Logic {
     type Formula = FormulaBuilder
     def formula(c: Clause*): Formula = ArrayBuffer(c: _*)
 
-    type Clause  = collection.Set[Lit]
+    type Clause  = Set[Lit]
     // a clause is a disjunction of distinct literals
-    def clause(l: Lit*): Clause = (
-      if (l.lengthCompare(1) <= 0) {
-        l.toSet // SI-8531 Avoid LinkedHashSet's bulk for 0 and 1 element clauses
-      } else {
-        // neg/t7020.scala changes output 1% of the time, the non-determinism is quelled with this linked set
-        mutable.LinkedHashSet(l: _*)
-      }
-    )
+    def clause(l: Lit*): Clause = l.toSet
 
     type Lit
     def Lit(sym: Sym, pos: Boolean = true): Lit
@@ -140,7 +133,7 @@ trait Solving extends Logic {
     def cnfString(f: Formula) = alignAcrossRows(f map (_.toList) toList, "\\/", " /\\\n")
 
     // adapted from http://lara.epfl.ch/w/sav10:simple_sat_solver (original by Hossein Hojjat)
-    val EmptyModel = collection.immutable.SortedMap.empty[Sym, Boolean]
+    val EmptyModel = Map.empty[Sym, Boolean]
     val NoModel: Model = null
 
     // returns all solutions, if any (TODO: better infinite recursion backstop -- detect fixpoint??)
@@ -256,15 +249,14 @@ trait Solving extends Logic {
             withLit(findModelFor(dropUnit(f, unitLit)), unitLit)
           case _ =>
             // partition symbols according to whether they appear in positive and/or negative literals
-            // SI-7020 Linked- for deterministic counter examples.
-            val pos = new mutable.LinkedHashSet[Sym]()
-            val neg = new mutable.LinkedHashSet[Sym]()
+            val pos = new mutable.HashSet[Sym]()
+            val neg = new mutable.HashSet[Sym]()
             mforeach(f)(lit => if (lit.pos) pos += lit.sym else neg += lit.sym)
 
             // appearing in both positive and negative
-            val impures: mutable.LinkedHashSet[Sym] = pos intersect neg
+            val impures = pos intersect neg
             // appearing only in either positive/negative positions
-            val pures: mutable.LinkedHashSet[Sym] = (pos ++ neg) -- impures
+            val pures = (pos ++ neg) -- impures
 
             if (pures nonEmpty) {
               val pureSym = pures.head