Do not accidentally force diagnostic message in reportWarning

compiler/src/dotty/tools/dotc/reporting/ConsoleReporter.scala

@@ -24,19 +24,19 @@ class ConsoleReporter(
   def doReport(m: MessageContainer)(implicit ctx: Context): Unit = {
     val didPrint = m match {
       case m: Error =>
-        printMessage(messageAndPos(m.contained, m.pos, diagnosticLevel(m)))
+        printMessage(messageAndPos(m.contained(), m.pos, diagnosticLevel(m)))
         if (ctx.settings.prompt.value) displayPrompt()
         true
       case m: ConditionalWarning if !m.enablingOption.value =>
         false
       case m =>
-        printMessage(messageAndPos(m.contained, m.pos, diagnosticLevel(m)))
+        printMessage(messageAndPos(m.contained(), m.pos, diagnosticLevel(m)))
         true
     }
 
     if (didPrint && ctx.shouldExplain(m))
-      printMessage(explanation(m.contained))
-    else if (didPrint && m.contained.explanation.nonEmpty)
+      printMessage(explanation(m.contained()))
+    else if (didPrint && m.contained().explanation.nonEmpty)
       printMessage("\nlonger explanation available when compiling with `-explain`")
   }
 

compiler/src/dotty/tools/dotc/reporting/Reporter.scala

@@ -37,8 +37,8 @@ trait Reporting { this: Context =>
   def echo(msg: => String, pos: SourcePosition = NoSourcePosition): Unit =
     reporter.report(new Info(msg, pos))
 
-  def reportWarning(warning:Warning):Unit =
-    if(this.settings.XfatalWarnings.value) error(warning.contained, warning.pos)
+  def reportWarning(warning: Warning): Unit =
+    if (this.settings.XfatalWarnings.value) reporter.report(warning.toError)
     else reporter.report(warning)
 
   def deprecationWarning(msg: => Message, pos: SourcePosition = NoSourcePosition): Unit =

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

@@ -15,7 +15,7 @@ object MessageContainer {
   implicit class MessageContext(val c: Context) extends AnyVal {
     def shouldExplain(cont: MessageContainer): Boolean = {
       implicit val ctx = c
-      cont.contained.explanation match {
+      cont.contained().explanation match {
         case "" => false
         case _ => ctx.settings.explain.value
       }
@@ -39,7 +39,7 @@ class MessageContainer(
   /** The message to report */
   def message: String = {
     if (myMsg == null) {
-      myMsg = contained.msg.replaceAll("\u001B\\[[;\\d]*m", "")
+      myMsg = contained().msg.replaceAll("\u001B\\[[;\\d]*m", "")
       if (myMsg.contains(nonSensicalStartTag)) {
         myIsNonSensical = true
         // myMsg might be composed of several d"..." invocations -> nested
@@ -53,7 +53,8 @@ class MessageContainer(
     myMsg
   }
 
-  def contained: Message = {
+  /** This function forces the contained message and returns it */
+  def contained(): Message = {
     if (myContained == null)
       myContained = msgFn
 

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

@@ -31,7 +31,9 @@ object messages {
   class Warning(
     msgFn: => Message,
     pos: SourcePosition
-  ) extends MessageContainer(msgFn, pos, WARNING)
+  ) extends MessageContainer(msgFn, pos, WARNING) {
+    def toError: Error = new Error(msgFn, pos)
+  }
 
   class Info(
     msgFn: => Message,

compiler/test/dotty/tools/dotc/reporting/ErrorMessagesTest.scala

@@ -40,7 +40,7 @@ trait ErrorMessagesTest extends DottyTest {
 
     def doReport(m: MessageContainer)(implicit ctx: Context) = {
       capturedContext = ctx
-      buffer append m.contained
+      buffer append m.contained()
     }
 
     def toReport: Report =

compiler/test/dotty/tools/dotc/reporting/TestReporter.scala

@@ -49,7 +49,7 @@ extends Reporter with UniqueMessagePositions with HideNonSensicalMessages with M
 
   /** Prints the message with the given position indication. */
   def printMessageAndPos(m: MessageContainer, extra: String)(implicit ctx: Context): Unit = {
-    val msg = messageAndPos(m.contained, m.pos, diagnosticLevel(m))
+    val msg = messageAndPos(m.contained(), m.pos, diagnosticLevel(m))
     val extraInfo = inlineInfo(m.pos)
 
     if (m.level >= logLevel) {
@@ -63,7 +63,7 @@ extends Reporter with UniqueMessagePositions with HideNonSensicalMessages with M
 
   override def doReport(m: MessageContainer)(implicit ctx: Context): Unit = {
     // Here we add extra information that we should know about the error message
-    val extra = m.contained match {
+    val extra = m.contained() match {
       case pm: PatternMatchExhaustivity => s": ${pm.uncovered}"
       case _ => ""
     }
@@ -120,7 +120,7 @@ object TestReporter {
       /** Prints the message with the given position indication in a simplified manner */
       override def printMessageAndPos(m: MessageContainer, extra: String)(implicit ctx: Context): Unit = {
         def report() = {
-          val msg = s"${m.pos.line + 1}: " + m.contained.kind + extra
+          val msg = s"${m.pos.line + 1}: " + m.contained().kind + extra
           val extraInfo = inlineInfo(m.pos)
 
           writer.println(msg)