Reuse regex matcher in replaceAll calls

Regex compilation is expensive, so we should re-use the matcher over
multiple replaceAll calls in:

 - StdNames.str.sanitize
 - Text's lengthWithoutAnsi

Author: odersky

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

@@ -3,6 +3,7 @@ package core
 
 import scala.collection.mutable
 import scala.annotation.switch
+import scala.annotation.internal.sharable
 import Names._
 import Symbols._
 import Contexts._
@@ -40,7 +41,9 @@ object StdNames {
     inline val Tuple                      = "Tuple"
     inline val Product                    = "Product"
 
-    def sanitize(str: String): String = str.replaceAll("""[<>]""", """\$""").nn
+    @sharable
+    private val disallowed = java.util.regex.Pattern.compile("""[<>]""").nn
+    def sanitize(str: String): String = disallowed.matcher(str).nn.replaceAll("""\$""").nn
   }
 
   abstract class DefinedNames[N <: Name] {

compiler/src/dotty/tools/dotc/printing/Texts.scala

@@ -1,8 +1,12 @@
 package dotty.tools.dotc
 package printing
+import scala.annotation.internal.sharable
 
 object Texts {
 
+  @sharable
+  private val ansi = java.util.regex.Pattern.compile("\u001b\\[\\d+m").nn
+
   sealed abstract class Text {
 
     protected def indentMargin: Int = 2
@@ -70,7 +74,7 @@ object Texts {
       else appendIndented(that)(width)
 
     private def lengthWithoutAnsi(str: String): Int =
-      str.replaceAll("\u001b\\[\\d+m", "").nn.length
+      ansi.matcher(str).nn.replaceAll("").nn.length
 
     def layout(width: Int): Text = this match {
       case Str(s, _) =>