Added -Xdev setting... you know, for devs

A setting we developers can give all the time and expect to
hear useful things without being buried in debugging output.
As the comment says:

  This is for WARNINGS which should reach the ears of scala
  developers whenever they occur, but are not useful for normal
  users. They should be precise, explanatory, and infrequent. Please
  don't use this as a logging mechanism. !!! is prefixed to all
  messages issued via this route to make them visually distinct.

This is what I always intended for "debugwarn", the method
I have deprecated in favor of the more accurate:

  def devWarning(msg: => String): Unit

In this VERY SAME COMMIT, I performed the CLOSELY RELATED
task of quieting down an -Xlint warning which had become too
noisy thanks to implicit classes tickling it. I tightened that
warn condition to include both -Xlint and -Xdev.

16 files changed, 38 insertions, 23 deletions

diff --git a/src/compiler/scala/tools/nsc/Global.scala b/src/compiler/scala/tools/nsc/Global.scala
index 13bec828ca..9c87ff9ad8 100644
--- a/src/compiler/scala/tools/nsc/Global.scala
+++ b/src/compiler/scala/tools/nsc/Global.scala
@@ -253,11 +253,15 @@ class Global(var currentSettings: Settings, var reporter: Reporter)
     if (settings.debug.value)
       body
   }
-  // Warnings issued only under -Ydebug.  For messages which should reach
-  // developer ears, but are not adequately actionable by users.
-  @inline final override def debugwarn(msg: => String) {
-    if (settings.debug.value)
-      warning(msg)
+  /** This is for WARNINGS which should reach the ears of scala developers
+   *  whenever they occur, but are not useful for normal users. They should
+   *  be precise, explanatory, and infrequent. Please don't use this as a
+   *  logging mechanism. !!! is prefixed to all messages issued via this route
+   *  to make them visually distinct.
+   */
+  @inline final override def devWarning(msg: => String) {
+    if (settings.developer.value || settings.debug.value)
+      warning("!!! " + msg)
   }
 
   private def elapsedMessage(msg: String, start: Long) =
diff --git a/src/compiler/scala/tools/nsc/backend/icode/GenICode.scala b/src/compiler/scala/tools/nsc/backend/icode/GenICode.scala
index 720896d0b3..03ad618b86 100644
--- a/src/compiler/scala/tools/nsc/backend/icode/GenICode.scala
+++ b/src/compiler/scala/tools/nsc/backend/icode/GenICode.scala
@@ -1251,8 +1251,11 @@ abstract class GenICode extends SubComponent  {
       val sym = (
         if (!tree.symbol.isPackageClass) tree.symbol
         else tree.symbol.info.member(nme.PACKAGE) match {
-          case NoSymbol => assert(false, "Cannot use package as value: " + tree) ; NoSymbol
-          case s        => debugwarn("Bug: found package class where package object expected.  Converting.") ; s.moduleClass
+          case NoSymbol =>
+            abort("Cannot use package as value: " + tree)
+          case s        =>
+            devWarning(s"Found ${tree.symbol} where a package object is required. Converting to ${s.moduleClass}")
+            s.moduleClass
         }
       )
       debuglog("LOAD_MODULE from %s: %s".format(tree.shortClass, sym))
diff --git a/src/compiler/scala/tools/nsc/backend/icode/ICodes.scala b/src/compiler/scala/tools/nsc/backend/icode/ICodes.scala
index 7c6f2a0620..e2d387c65d 100644
--- a/src/compiler/scala/tools/nsc/backend/icode/ICodes.scala
+++ b/src/compiler/scala/tools/nsc/backend/icode/ICodes.scala
@@ -28,7 +28,7 @@ abstract class ICodes extends AnyRef
                                  with Repository
 {
   val global: Global
-  import global.{ log, definitions, settings, perRunCaches }
+  import global.{ log, definitions, settings, perRunCaches, devWarning }
 
   /** The ICode representation of classes */
   val classes = perRunCaches.newMap[global.Symbol, IClass]()
@@ -82,7 +82,7 @@ abstract class ICodes extends AnyRef
         // Something is leaving open/empty blocks around (see SI-4840) so
         // let's not kill the deal unless it's nonempty.
         if (b.isEmpty) {
-          log("!!! Found open but empty block while inlining " + m + ": removing from block list.")
+          devWarning(s"Found open but empty block while inlining $m: removing from block list.")
           m.code removeBlock b
         }
         else dumpMethodAndAbort(m, b)
diff --git a/src/compiler/scala/tools/nsc/backend/icode/analysis/ReachingDefinitions.scala b/src/compiler/scala/tools/nsc/backend/icode/analysis/ReachingDefinitions.scala
index 45c85ff25a..48755d4424 100644
--- a/src/compiler/scala/tools/nsc/backend/icode/analysis/ReachingDefinitions.scala
+++ b/src/compiler/scala/tools/nsc/backend/icode/analysis/ReachingDefinitions.scala
@@ -52,7 +52,7 @@ abstract class ReachingDefinitions {
           // it makes it harder to spot the real problems.
           val result = (a.stack, b.stack).zipped map (_ ++ _)
           if (settings.debug.value && (a.stack.length != b.stack.length))
-            debugwarn("Mismatched stacks in ReachingDefinitions#lub2: " + a.stack + ", " + b.stack + ", returning " + result)
+            devWarning(s"Mismatched stacks in ReachingDefinitions#lub2: ${a.stack}, ${b.stack}, returning $result")
           result
         }
       )
diff --git a/src/compiler/scala/tools/nsc/settings/ScalaSettings.scala b/src/compiler/scala/tools/nsc/settings/ScalaSettings.scala
index 8dce48ee9a..af0e3c97b0 100644
--- a/src/compiler/scala/tools/nsc/settings/ScalaSettings.scala
+++ b/src/compiler/scala/tools/nsc/settings/ScalaSettings.scala
@@ -74,6 +74,7 @@ trait ScalaSettings extends AbsScalaSettings
   val assemextdirs  = StringSetting     ("-Xassem-extdirs", "dirs", "(Requires -target:msil) List of directories containing assemblies.  default:lib", Defaults.scalaLibDir.path).dependsOn(target, "msil")
   val sourcedir     = StringSetting     ("-Xsourcedir", "directory", "(Requires -target:msil) Mirror source folder structure in output directory.", ".").dependsOn(target, "msil")
   val checkInit     = BooleanSetting    ("-Xcheckinit", "Wrap field accessors to throw an exception on uninitialized access.")
+  val developer     = BooleanSetting    ("-Xdev", "Indicates user is a developer - issue warnings about anything which seems amiss")
   val noassertions  = BooleanSetting    ("-Xdisable-assertions", "Generate no assertions or assumptions.")
   val elidebelow    = IntSetting        ("-Xelide-below", "Calls to @elidable methods are omitted if method priority is lower than argument",
                                                 elidable.MINIMUM, None, elidable.byName get _)
diff --git a/src/compiler/scala/tools/nsc/transform/Mixin.scala b/src/compiler/scala/tools/nsc/transform/Mixin.scala
index 8122dc38cf..2025891ab2 100644
--- a/src/compiler/scala/tools/nsc/transform/Mixin.scala
+++ b/src/compiler/scala/tools/nsc/transform/Mixin.scala
@@ -289,7 +289,7 @@ abstract class Mixin extends InfoTransform with ast.TreeDSL {
       for (mixinMember <- mixinClass.info.decls) {
         if (isConcreteAccessor(mixinMember)) {
           if (isOverriddenAccessor(mixinMember, clazz.info.baseClasses))
-            debugwarn("!!! is overridden val: "+mixinMember.fullLocationString)
+            devWarning(s"Overridden concrete accessor: ${mixinMember.fullLocationString}")
           else {
             // mixin field accessors
             val mixedInAccessor = cloneAndAddMixinMember(mixinClass, mixinMember)
diff --git a/src/compiler/scala/tools/nsc/transform/SpecializeTypes.scala b/src/compiler/scala/tools/nsc/transform/SpecializeTypes.scala
index 78fb725041..3af9524f3e 100644
--- a/src/compiler/scala/tools/nsc/transform/SpecializeTypes.scala
+++ b/src/compiler/scala/tools/nsc/transform/SpecializeTypes.scala
@@ -1482,7 +1482,7 @@ abstract class SpecializeTypes extends InfoTransform with TypingTransformers {
               }
               // See SI-5583.  Don't know why it happens now if it didn't before.
               if (specMember.info.typeParams.isEmpty && residualTargs.nonEmpty) {
-                log("!!! Type args to be applied, but symbol says no parameters: " + ((specMember.defString, residualTargs)))
+                devWarning("Type args to be applied, but symbol says no parameters: " + ((specMember.defString, residualTargs)))
                 localTyper.typed(sel)
               }
               else {
diff --git a/src/compiler/scala/tools/nsc/transform/UnCurry.scala b/src/compiler/scala/tools/nsc/transform/UnCurry.scala
index 84803d0b6b..becc7f65ff 100644
--- a/src/compiler/scala/tools/nsc/transform/UnCurry.scala
+++ b/src/compiler/scala/tools/nsc/transform/UnCurry.scala
@@ -297,7 +297,8 @@ abstract class UnCurry extends InfoTransform
      *  If there's a default case, the original match is used for applyOrElse, and isDefinedAt returns `true`
      */
     def synthPartialFunction(fun: Function) = {
-      if (!settings.XoldPatmat.value) debugwarn("Under the new pattern matching scheme, PartialFunction should have been synthesized during typers.")
+      if (!settings.XoldPatmat.value)
+        devWarning("Under the new pattern matching scheme, PartialFunction should have been synthesized during typers.")
 
       val targs             = fun.tpe.typeArgs
       val (formals, restpe) = (targs.init, targs.last)
@@ -704,7 +705,7 @@ abstract class UnCurry extends InfoTransform
         val finalizer = tree.finalizer
         if (!settings.XoldPatmat.value) {
           if (catches exists (cd => !treeInfo.isCatchCase(cd)))
-            debugwarn("VPM BUG! illegal try/catch " + catches)
+            devWarning("VPM BUG - illegal try/catch " + catches)
           tree
         } else if (catches forall treeInfo.isCatchCase) {
           tree
diff --git a/src/compiler/scala/tools/nsc/typechecker/Checkable.scala b/src/compiler/scala/tools/nsc/typechecker/Checkable.scala
index 166a9785fa..9efa3f36b0 100644
--- a/src/compiler/scala/tools/nsc/typechecker/Checkable.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/Checkable.scala
@@ -130,7 +130,7 @@ trait Checkable {
       else if (P3) RuntimeCheckable
       else if (uncheckableType == NoType) {
         // Avoid warning (except ourselves) if we can't pinpoint the uncheckable type
-        debugwarn("Checkability checker says 'Uncheckable', but uncheckable type cannot be found:\n" + summaryString)
+        debuglog("Checkability checker says 'Uncheckable', but uncheckable type cannot be found:\n" + summaryString)
         CheckabilityError
       }
       else Uncheckable
diff --git a/src/compiler/scala/tools/nsc/typechecker/Contexts.scala b/src/compiler/scala/tools/nsc/typechecker/Contexts.scala
index 78380ad054..0a9baca58b 100644
--- a/src/compiler/scala/tools/nsc/typechecker/Contexts.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/Contexts.scala
@@ -398,8 +398,10 @@ trait Contexts { self: Analyzer =>
       unit.error(pos, if (checking) "\n**** ERROR DURING INTERNAL CHECKING ****\n" + msg else msg)
 
     @inline private def issueCommon(err: AbsTypeError)(pf: PartialFunction[AbsTypeError, Unit]) {
-      debugwarn("issue error: " + err.errMsg)
-      if (settings.Yissuedebug.value) (new Exception).printStackTrace()
+      if (settings.Yissuedebug.value) {
+        log("issue error: " + err.errMsg)
+        (new Exception).printStackTrace()
+      }
       if (pf isDefinedAt err) pf(err)
       else if (bufferErrors) { buffer += err }
       else throw new TypeError(err.errPos, err.errMsg)
diff --git a/src/compiler/scala/tools/nsc/typechecker/Implicits.scala b/src/compiler/scala/tools/nsc/typechecker/Implicits.scala
index 576a21fe31..710b7e9051 100644
--- a/src/compiler/scala/tools/nsc/typechecker/Implicits.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/Implicits.scala
@@ -82,7 +82,7 @@ trait Implicits {
     val result = new ImplicitSearch(tree, pt, isView, implicitSearchContext, pos).bestImplicit
     if (saveAmbiguousDivergent && implicitSearchContext.hasErrors) {
       context.updateBuffer(implicitSearchContext.errBuffer.filter(err => err.kind == ErrorKinds.Ambiguous || err.kind == ErrorKinds.Divergent))
-      debugwarn("update buffer: " + implicitSearchContext.errBuffer)
+      debuglog("update buffer: " + implicitSearchContext.errBuffer)
     }
     printInference("[infer implicit] inferred " + result)
     context.undetparams = context.undetparams filterNot result.subst.from.contains
diff --git a/src/compiler/scala/tools/nsc/typechecker/Infer.scala b/src/compiler/scala/tools/nsc/typechecker/Infer.scala
index 6e42481d60..ac367dfde6 100644
--- a/src/compiler/scala/tools/nsc/typechecker/Infer.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/Infer.scala
@@ -1319,7 +1319,8 @@ trait Infer extends Checkable {
           new TreeTypeSubstituter(undetparams, targs).traverse(tree)
           notifyUndetparamsInferred(undetparams, targs)
         case _ =>
-          debugwarn("failed inferConstructorInstance for "+ tree  +" : "+ tree.tpe +" under "+ undetparams +" pt = "+ pt +(if(isFullyDefined(pt)) " (fully defined)" else " (not fully defined)"))
+          def full = if (isFullyDefined(pt)) "(fully defined)" else "(not fully defined)"
+          devWarning(s"failed inferConstructorInstance for $tree: ${tree.tpe} undet=$undetparams, pt=$pt $full")
           // if (settings.explaintypes.value) explainTypes(resTp.instantiateTypeParams(undetparams, tvars), pt)
           ConstrInstantiationError(tree, resTp, pt)
       }
diff --git a/src/compiler/scala/tools/nsc/typechecker/Namers.scala b/src/compiler/scala/tools/nsc/typechecker/Namers.scala
index 04fb69671e..ee1b1f9b37 100644
--- a/src/compiler/scala/tools/nsc/typechecker/Namers.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/Namers.scala
@@ -336,7 +336,7 @@ trait Namers extends MethodSynthesis {
 
     private def enterClassSymbol(tree: ClassDef, clazz: ClassSymbol): Symbol = {
       if (clazz.sourceFile != null && clazz.sourceFile != contextFile)
-        debugwarn("!!! Source mismatch in " + clazz + ": " + clazz.sourceFile + " vs. " + contextFile)
+        devWarning(s"Source file mismatch in $clazz: ${clazz.sourceFile} vs. $contextFile")
 
       clazz.associatedFile = contextFile
       if (clazz.sourceFile != null) {
diff --git a/src/compiler/scala/tools/nsc/typechecker/PatternMatching.scala b/src/compiler/scala/tools/nsc/typechecker/PatternMatching.scala
index 7cb420d2dc..6c916649f0 100644
--- a/src/compiler/scala/tools/nsc/typechecker/PatternMatching.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/PatternMatching.scala
@@ -271,7 +271,9 @@ trait PatternMatching extends Transform with TypingTransformers with ast.TreeDSL
       // we don't transform after uncurry
       // (that would require more sophistication when generating trees,
       //  and the only place that emits Matches after typers is for exception handling anyway)
-      if(phase.id >= currentRun.uncurryPhase.id) debugwarn("running translateMatch at "+ phase +" on "+ selector +" match "+ cases)
+      if (phase.id >= currentRun.uncurryPhase.id)
+        devWarning(s"running translateMatch past uncurry (at $phase) on $selector match $cases")
+
       patmatDebug("translating "+ cases.mkString("{", "\n", "}"))
 
       val start = if (Statistics.canEnable) Statistics.startTimer(patmatNanos) else null
diff --git a/src/compiler/scala/tools/nsc/typechecker/RefChecks.scala b/src/compiler/scala/tools/nsc/typechecker/RefChecks.scala
index 9eb06dbdbf..7a7c7c7d25 100644
--- a/src/compiler/scala/tools/nsc/typechecker/RefChecks.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/RefChecks.scala
@@ -139,7 +139,8 @@ abstract class RefChecks extends InfoTransform with scala.reflect.internal.trans
         }
       }
 
-      if (settings.lint.value) {
+      // This has become noisy with implicit classes.
+      if (settings.lint.value && settings.developer.value) {
         clazz.info.decls filter (x => x.isImplicit && x.typeParams.nonEmpty) foreach { sym =>
           val alts = clazz.info.decl(sym.name).alternatives
           if (alts.size > 1)
diff --git a/src/compiler/scala/tools/nsc/typechecker/Typers.scala b/src/compiler/scala/tools/nsc/typechecker/Typers.scala
index d9084af7bc..fb5c5e6f84 100644
--- a/src/compiler/scala/tools/nsc/typechecker/Typers.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/Typers.scala
@@ -1545,7 +1545,7 @@ trait Typers extends Modes with Adaptations with Tags {
 
             val preSuperVals = treeInfo.preSuperFields(templ.body)
             if (preSuperVals.isEmpty && preSuperStats.nonEmpty)
-              debugwarn("Wanted to zip empty presuper val list with " + preSuperStats)
+              devWarning("Wanted to zip empty presuper val list with " + preSuperStats)
             else
               map2(preSuperStats, preSuperVals)((ldef, gdef) => gdef.tpt.tpe = ldef.symbol.tpe)