Micro-optimization: Avoid nonEmpty in hot paths

Author: smarter

compiler/src/dotty/tools/dotc/ast/Trees.scala

@@ -771,7 +771,7 @@ object Trees {
   def flatten[T >: Untyped](trees: List[Tree[T]]): List[Tree[T]] = {
     var buf: ListBuffer[Tree[T]] = null
     var xs = trees
-    while (xs.nonEmpty) {
+    while (!xs.isEmpty) {
       xs.head match {
         case Thicket(elems) =>
           if (buf == null) {

compiler/src/dotty/tools/dotc/core/Hashable.scala

@@ -64,7 +64,7 @@ trait Hashable {
     var h = seed
     var xs = tps
     var len = arity
-    while (xs.nonEmpty) {
+    while (!xs.isEmpty) {
       val elemHash = typeHash(bs, xs.head)
       if (elemHash == NotCached) return NotCached
       h = hashing.mix(h, elemHash)

compiler/src/dotty/tools/dotc/core/Signature.scala

@@ -45,7 +45,7 @@ case class Signature(paramsSig: List[TypeName], resSig: TypeName) {
   final def consistentParams(that: Signature): Boolean = {
     @tailrec def loop(names1: List[TypeName], names2: List[TypeName]): Boolean =
       if (names1.isEmpty) names2.isEmpty
-      else names2.nonEmpty && consistent(names1.head, names2.head) && loop(names1.tail, names2.tail)
+      else !names2.isEmpty && consistent(names1.head, names2.head) && loop(names1.tail, names2.tail)
     loop(this.paramsSig, that.paramsSig)
   }
 

compiler/src/dotty/tools/dotc/parsing/Scanners.scala

@@ -249,13 +249,13 @@ object Scanners {
     /** Are we directly in a string interpolation expression?
      */
     private def inStringInterpolation =
-      sepRegions.nonEmpty && sepRegions.head == STRINGLIT
+      !sepRegions.isEmpty && sepRegions.head == STRINGLIT
 
     /** Are we directly in a multiline string interpolation expression?
      *  @pre inStringInterpolation
      */
     private def inMultiLineInterpolation =
-      inStringInterpolation && sepRegions.tail.nonEmpty && sepRegions.tail.head == STRINGPART
+      inStringInterpolation && !sepRegions.tail.isEmpty && sepRegions.tail.head == STRINGPART
 
     /** read next token and return last offset
      */