Implement ReplConsoleReporter in terms of the ReplDriver out PrintStream

Based on the implementation of ConsoleReporter.

Sidesteps issues on Windows where the default console encoding may be
something other than UTF8 (such as Cp437), which PrintStream is aware
of, but apparently there is no API to query.

Author: griggt

compiler/src/dotty/tools/repl/ReplDriver.scala

@@ -1,6 +1,6 @@
 package dotty.tools.repl
 
-import java.io.{BufferedWriter, File => JFile, OutputStreamWriter, PrintStream, PrintWriter}
+import java.io.{File => JFile, PrintStream}
 import java.nio.charset.StandardCharsets
 
 import dotty.tools.dotc.ast.Trees._
@@ -20,7 +20,7 @@ import dotty.tools.dotc.core.Symbols.{Symbol, defn}
 import dotty.tools.dotc.interfaces
 import dotty.tools.dotc.interactive.Completion
 import dotty.tools.dotc.printing.SyntaxHighlighting
-import dotty.tools.dotc.reporting.{ConsoleReporter, MessageRendering, StoreReporter}
+import dotty.tools.dotc.reporting.{AbstractReporter, MessageRendering, StoreReporter}
 import dotty.tools.dotc.reporting.{Message, Diagnostic}
 import dotty.tools.dotc.util.Spans.Span
 import dotty.tools.dotc.util.{SourceFile, SourcePosition}
@@ -426,10 +426,18 @@ class ReplDriver(settings: Array[String],
   }
 
   /** Like ConsoleReporter, but without file paths or real -Xprompt'ing */
-  private object ReplConsoleReporter extends ConsoleReporter(
-    reader = null, // this short-circuits the -Xprompt display from waiting for an input
-    writer = new PrintWriter(new BufferedWriter(new OutputStreamWriter(out, StandardCharsets.UTF_8)), /* autoFlush = */ true), // write to out, not Console.err
-  ) {
+  private object ReplConsoleReporter extends AbstractReporter {
+    def printMessage(msg: String): Unit = out.println(msg)
+
+    def doReport(dia: Diagnostic)(using Context): Unit = {
+      printMessage(messageAndPos(dia))
+
+      if Diagnostic.shouldExplain(dia) then
+        printMessage(explanation(dia.msg))
+      else if dia.msg.canExplain then
+        printMessage("\nlonger explanation available when compiling with `-explain`")
+    }
+
     override def posFileStr(pos: SourcePosition) = "" // omit file paths
   }