Fix #3932: prevent RefinedPrinter colors leaks

Author: OlivierBlanvillain

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

@@ -536,9 +536,9 @@ class PlainPrinter(_ctx: Context) extends Printer {
   protected def literalText(text: Text): Text = coloredText(text, SyntaxHighlighting.LiteralColor)
   protected def stringText(text: Text): Text = coloredText(text, SyntaxHighlighting.StringColor)
 
-  private def coloredStr(text: String, color: String): String =
+  protected def coloredStr(text: String, color: String): String =
     if (ctx.useColors) color + text + SyntaxHighlighting.NoColor else text
-  private def coloredText(text: Text, color: String): Text =
+  protected def coloredText(text: Text, color: String): Text =
     if (ctx.useColors) color ~ text ~ SyntaxHighlighting.NoColor else text
 }
 

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

@@ -37,4 +37,9 @@ class ReplPrinter(_ctx: Context) extends DecompilerPrinter(_ctx) {
       else ":" ~~ toText(sym.info)
     }
   }
+
+  // We don't want the colors coming from RefinedPrinter as the REPL uses its
+  // own syntax coloring mechanism.
+  override def coloredStr(text: String, color: String): String = text
+  override def coloredText(text: Text, color: String): Text = text
 }

compiler/test-resources/repl/3932

@@ -0,0 +1,2 @@
+scala> def fun[T](x: T): implicit List[T] => Int = ???
+def fun[T](x: T): implicit List[T] => Int