support for -Xfatal-warnings

compiler/src/dotty/tools/dotc/config/ScalaSettings.scala

@@ -57,6 +57,7 @@ class ScalaSettings extends Settings.SettingGroup {
   val mainClass = StringSetting("-Xmain-class", "path", "Class for manifest's Main-Class entry (only useful with -d <jar>)", "")
   val XnoValueClasses = BooleanSetting("-Xno-value-classes", "Do not use value classes. Helps debugging.")
   val XreplLineWidth = IntSetting("-Xrepl-line-width", "Maximial number of columns per line for REPL output", 390)
+  val XfatalWarnings = BooleanSetting("-Xfatal-warnings", "Fail the compilation if there are any warnings.")
 
   /** -Y "Private" settings */
   val overrideVars = BooleanSetting("-Yoverride-vars", "Allow vars to be overridden.")

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

@@ -37,17 +37,21 @@ 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)
+    else reporter.report(warning)
+
   def deprecationWarning(msg: => Message, pos: SourcePosition = NoSourcePosition): Unit =
-    reporter.report(new DeprecationWarning(msg, pos))
+    reportWarning(new DeprecationWarning(msg, pos))
 
   def migrationWarning(msg: => Message, pos: SourcePosition = NoSourcePosition): Unit =
-    reporter.report(new MigrationWarning(msg, pos))
+    reportWarning(new MigrationWarning(msg, pos))
 
   def uncheckedWarning(msg: => Message, pos: SourcePosition = NoSourcePosition): Unit =
-    reporter.report(new UncheckedWarning(msg, pos))
+    reportWarning(new UncheckedWarning(msg, pos))
 
   def featureWarning(msg: => Message, pos: SourcePosition = NoSourcePosition): Unit =
-    reporter.report(new FeatureWarning(msg, pos))
+    reportWarning(new FeatureWarning(msg, pos))
 
   def featureWarning(feature: String, featureDescription: String, isScala2Feature: Boolean,
       featureUseSite: Symbol, required: Boolean, pos: SourcePosition): Unit = {
@@ -69,17 +73,15 @@ trait Reporting { this: Context =>
 
     val msg = s"$featureDescription $req be enabled\nby making the implicit value $fqname visible.$explain"
     if (required) error(msg, pos)
-    else reporter.report(new FeatureWarning(msg, pos))
+    else reportWarning(new FeatureWarning(msg, pos))
   }
 
   def warning(msg: => Message, pos: SourcePosition = NoSourcePosition): Unit =
-    reporter.report(new Warning(msg, pos))
+    reportWarning(new Warning(msg, pos))
 
   def strictWarning(msg: => Message, pos: SourcePosition = NoSourcePosition): Unit =
     if (this.settings.strict.value) error(msg, pos)
-    else reporter.report {
-      new ExtendMessage(() => msg)(_ + "\n(This would be an error under strict mode)").warning(pos)
-    }
+    else reportWarning(new ExtendMessage(() => msg)(_ + "\n(This would be an error under strict mode)").warning(pos))
 
   def error(msg: => Message, pos: SourcePosition = NoSourcePosition): Unit =
     reporter.report(new Error(msg, pos))

compiler/test/dotty/tools/dotc/CompilationTests.scala

@@ -145,6 +145,7 @@ class CompilationTests extends ParallelTesting {
     compileFile("../tests/neg/customArgs/noimports.scala", defaultOptions.and("-Yno-imports")) +
     compileFile("../tests/neg/customArgs/noimports2.scala", defaultOptions.and("-Yno-imports")) +
     compileFile("../tests/neg/customArgs/overloadsOnAbstractTypes.scala", allowDoubleBindings) +
+    compileFile("../tests/neg/customArgs/xfatalWarnings.scala", defaultOptions.and("-Xfatal-warnings")) +
     compileFile("../tests/neg/tailcall/t1672b.scala", defaultOptions) +
     compileFile("../tests/neg/tailcall/t3275.scala", defaultOptions) +
     compileFile("../tests/neg/tailcall/t6574.scala", defaultOptions) +

tests/neg/customArgs/xfatalWarnings.scala

@@ -0,0 +1,7 @@
+object xfatalWarnings {
+  val opt:Option[String] = Some("test")
+
+  opt match { // error when running with -Xfatal-warnings
+    case None =>
+  }
+}