Make fatal warnings not fail compilation early & aggregate warns

Author: szymon-rd

compiler/src/dotty/tools/dotc/Run.scala

@@ -346,6 +346,7 @@ class Run(comp: Compiler, ictx: Context) extends ImplicitRunInfo with Constraint
     runCtx.withProgressCallback: cb =>
       _progress = Progress(cb, this, fusedPhases.map(_.traversals).sum)
     runPhases(allPhases = fusedPhases)(using runCtx)
+    ctx.reporter.finalizeReporting()
     if (!ctx.reporter.hasErrors)
       Rewrites.writeBack()
     suppressions.runFinished(hasErrors = ctx.reporter.hasErrors)

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

@@ -172,19 +172,14 @@ abstract class Reporter extends interfaces.ReporterResult {
   end issueUnconfigured
 
   def issueIfNotSuppressed(dia: Diagnostic)(using Context): Unit =
-    def toErrorIfFatal(dia: Diagnostic) = dia match
-      case w: Warning if ctx.settings.silentWarnings.value => dia
-      case w: ConditionalWarning if w.isSummarizedConditional => dia
-      case w: Warning if ctx.settings.XfatalWarnings.value => w.toError
-      case _ => dia
 
     def go() =
       import Action.*
       dia match
         case w: Warning => WConf.parsed.action(dia) match
           case Error   => issueUnconfigured(w.toError)
-          case Warning => issueUnconfigured(toErrorIfFatal(w))
-          case Verbose => issueUnconfigured(toErrorIfFatal(w.setVerbose()))
+          case Warning => issueUnconfigured(w)
+          case Verbose => issueUnconfigured(w.setVerbose())
           case Info    => issueUnconfigured(w.toInfo)
           case Silent  =>
         case _ => issueUnconfigured(dia)
@@ -214,6 +209,10 @@ abstract class Reporter extends interfaces.ReporterResult {
   def incomplete(dia: Diagnostic)(using Context): Unit =
     incompleteHandler(dia, ctx)
 
+  def finalizeReporting()(using Context) = 
+    if (hasWarnings && ctx.settings.XfatalWarnings.value)
+      report(new Error("No warnings can be incurred under -Werror.", NoSourcePosition))
+
   /** Summary of warnings and errors */
   def summary: String = {
     val b = new mutable.ListBuffer[String]