SI-6726 Further optimization of pattern analysis

Manually fuse `.filterNot(..).map` in dropUnit.

Before:

    real    1m23.574s
    user    1m51.795s
    sys 0m2.634s

After:

    real    1m4.883s
    user    1m30.754s
    sys 0m1.776s

2 files changed, 9 insertions, 4 deletions

diff --git a/src/compiler/scala/tools/nsc/typechecker/PatternMatching.scala b/src/compiler/scala/tools/nsc/typechecker/PatternMatching.scala
index a9714acc55..d00e0e6bf6 100644
--- a/src/compiler/scala/tools/nsc/typechecker/PatternMatching.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/PatternMatching.scala
@@ -2070,6 +2070,7 @@ trait PatternMatching extends Transform with TypingTransformers with ast.TreeDSL
     import scala.collection.mutable.ArrayBuffer
     type FormulaBuilder = ArrayBuffer[Clause]
     def formulaBuilder  = ArrayBuffer[Clause]()
+    def formulaBuilderSized(init: Int)  = new ArrayBuffer[Clause](init)
     def addFormula(buff: FormulaBuilder, f: Formula): Unit = buff ++= f
     def toFormula(buff: FormulaBuilder): Formula = buff
 
@@ -2223,13 +2224,18 @@ trait PatternMatching extends Transform with TypingTransformers with ast.TreeDSL
     }
 
     private def withLit(res: Model, l: Lit): Model = if (res eq NoModel) NoModel else res + (l.sym -> l.pos)
-    private def dropUnit(f: Formula, unitLit: Lit) = {
+    private def dropUnit(f: Formula, unitLit: Lit): Formula = {
       val negated = -unitLit
       // drop entire clauses that are trivially true
       // (i.e., disjunctions that contain the literal we're making true in the returned model),
       // and simplify clauses by dropping the negation of the literal we're making true
       // (since False \/ X == X)
-      f.filterNot(_.contains(unitLit)).map(_ - negated)
+      val dropped = formulaBuilderSized(f.size)
+      for {
+        clause <- f
+        if !(clause contains unitLit)
+      } dropped += (clause - negated)
+      dropped
     }
 
     def findModelFor(f: Formula): Model = {
diff --git a/src/reflect/scala/reflect/api/Symbols.scala b/src/reflect/scala/reflect/api/Symbols.scala
index 36f8626389..b53c700701 100644
--- a/src/reflect/scala/reflect/api/Symbols.scala
+++ b/src/reflect/scala/reflect/api/Symbols.scala
@@ -351,8 +351,7 @@ trait Symbols { self: Universe =>
     def asFreeType: FreeTypeSymbol = throw new ScalaReflectionException(s"$this is not a free type")
 
     /** @group Constructors */
-    def
-    newTermSymbol(name: TermName, pos: Position = NoPosition, flags: FlagSet = NoFlags): TermSymbol
+    def newTermSymbol(name: TermName, pos: Position = NoPosition, flags: FlagSet = NoFlags): TermSymbol
     /** @group Constructors */
     def newModuleAndClassSymbol(name: Name, pos: Position = NoPosition, flags: FlagSet = NoFlags): (ModuleSymbol, ClassSymbol)
     /** @group Constructors */