Fix #3614: Do not allow the SyntaxFormatter to recolor code

Author: nicolasstucki

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

@@ -77,10 +77,6 @@ object Formatting {
   class SyntaxFormatter(sc: StringContext) extends StringFormatter(sc) {
     override protected def showArg(arg: Any)(implicit ctx: Context): String =
       arg match {
-        case arg: Showable if ctx.settings.color.value != "never" =>
-          val highlighted =
-            SyntaxHighlighting(wrapNonSensical(arg, super.showArg(arg)))
-          new String(highlighted.toArray)
         case hl: Highlight =>
           hl.show
         case hb: HighlightBuffer =>

compiler/src/dotty/tools/dotc/reporting/diagnostic/messages.scala

@@ -729,7 +729,7 @@ object messages {
     val msg =
       hl"""|${NoColor(msgPrefix)} type arguments for $prettyName$expectedArgString
            |expected: $expectedArgString
-           |actual:   $actualArgString""".stripMargin
+           |actual:   ${NoColor(actualArgString)}""".stripMargin
 
     val explanation = {
       val tooManyTypeParams =
@@ -1418,11 +1418,11 @@ object messages {
     val msg = hl"$tpe does not take type parameters"
 
     private val ps =
-      if (params.size == 1) hl"a type parameter ${params.head}"
-      else hl"type parameters ${params.map(_.show).mkString(", ")}"
+      if (params.size == 1) s"a type parameter ${params.head}"
+      else s"type parameters ${params.map(_.show).mkString(", ")}"
 
     val explanation =
-      i"""You specified $ps for ${hl"$tpe"}, which is not
+      i"""You specified ${NoColor(ps)} for ${hl"$tpe"}, which is not
          |declared to take any.
          |"""
   }