Merge pull request #5402 from som-snytt/issue/8040-unused

SI-8040 Improve unused warnings

48 files changed, 737 insertions, 129 deletions

diff --git a/src/compiler/scala/reflect/reify/codegen/GenAnnotationInfos.scala b/src/compiler/scala/reflect/reify/codegen/GenAnnotationInfos.scala
index ce26232e5f..089f07de06 100644
--- a/src/compiler/scala/reflect/reify/codegen/GenAnnotationInfos.scala
+++ b/src/compiler/scala/reflect/reify/codegen/GenAnnotationInfos.scala
@@ -10,7 +10,7 @@ trait GenAnnotationInfos {
   // however, when reifying free and tough types, we're forced to reify annotation infos as is
   // why is that bad? take a look inside
   def reifyAnnotationInfo(ann: AnnotationInfo): Tree = {
-    val reifiedArgs = ann.args map { arg =>
+    ann.args.foreach { arg =>
       val saved1 = reifyTreeSymbols
       val saved2 = reifyTreeTypes
 
diff --git a/src/compiler/scala/tools/nsc/ast/TreeGen.scala b/src/compiler/scala/tools/nsc/ast/TreeGen.scala
index dd827a8f52..b073cb828c 100644
--- a/src/compiler/scala/tools/nsc/ast/TreeGen.scala
+++ b/src/compiler/scala/tools/nsc/ast/TreeGen.scala
@@ -371,4 +371,6 @@ abstract class TreeGen extends scala.reflect.internal.TreeGen with TreeDSL {
         Typed(New(anonClass.tpe), TypeTree(fun.tpe)))
     }
   }
+
+  override def isPatVarWarnable = settings.warnUnusedPatVars
 }
diff --git a/src/compiler/scala/tools/nsc/ast/parser/Parsers.scala b/src/compiler/scala/tools/nsc/ast/parser/Parsers.scala
index 82664ba9c0..707fe15f91 100644
--- a/src/compiler/scala/tools/nsc/ast/parser/Parsers.scala
+++ b/src/compiler/scala/tools/nsc/ast/parser/Parsers.scala
@@ -1947,19 +1947,22 @@ self =>
        *                |   Pattern3
        *  }}}
        */
-      def pattern2(): Tree = {
-        val p = pattern3()
-
-        if (in.token != AT) p
-        else p match {
-          case Ident(nme.WILDCARD) =>
-            in.nextToken()
-            pattern3()
-          case Ident(name) =>
-            in.nextToken()
-            atPos(p.pos.start) { Bind(name, pattern3()) }
-          case _ => p
-        }
+      def pattern2(): Tree = (pattern3(), in.token) match {
+        case (Ident(nme.WILDCARD), AT) =>
+          in.nextToken()
+          pattern3()
+        case (p @ Ident(name), AT) =>
+          in.nextToken()
+          val body = pattern3()
+          atPos(p.pos.start, p.pos.start, body.pos.end) {
+            val t = Bind(name, body)
+            body match {
+              case Ident(nme.WILDCARD) => t updateAttachment AtBoundIdentifierAttachment
+              case _ if !settings.warnUnusedPatVars => t updateAttachment AtBoundIdentifierAttachment
+              case _ => t
+            }
+          }
+        case (p, _) => p
       }
 
       /** {{{
@@ -2854,9 +2857,8 @@ self =>
           val (constrMods, vparamss) =
             if (mods.isTrait) (Modifiers(Flags.TRAIT), List())
             else (accessModifierOpt(), paramClauses(name, classContextBounds, ofCaseClass = mods.isCase))
-          var mods1 = mods
-          val template = templateOpt(mods1, name, constrMods withAnnotations constrAnnots, vparamss, tstart)
-          val result = gen.mkClassDef(mods1, name, tparams, template)
+          val template = templateOpt(mods, name, constrMods withAnnotations constrAnnots, vparamss, tstart)
+          val result = gen.mkClassDef(mods, name, tparams, template)
           // Context bounds generate implicit parameters (part of the template) with types
           // from tparams: we need to ensure these don't overlap
           if (!classContextBounds.isEmpty)
diff --git a/src/compiler/scala/tools/nsc/backend/jvm/opt/Inliner.scala b/src/compiler/scala/tools/nsc/backend/jvm/opt/Inliner.scala
index 0ae8347dc5..1c29859f46 100644
--- a/src/compiler/scala/tools/nsc/backend/jvm/opt/Inliner.scala
+++ b/src/compiler/scala/tools/nsc/backend/jvm/opt/Inliner.scala
@@ -15,7 +15,6 @@ import scala.collection.JavaConverters._
 import AsmUtils._
 import BytecodeUtils._
 import collection.mutable
-import scala.tools.asm.tree.analysis.{Analyzer, SourceInterpreter}
 import BackendReporting._
 import scala.tools.nsc.backend.jvm.BTypes.InternalName
 
diff --git a/src/compiler/scala/tools/nsc/settings/Warnings.scala b/src/compiler/scala/tools/nsc/settings/Warnings.scala
index 87534656f9..329a6aadd7 100644
--- a/src/compiler/scala/tools/nsc/settings/Warnings.scala
+++ b/src/compiler/scala/tools/nsc/settings/Warnings.scala
@@ -15,15 +15,40 @@ trait Warnings {
   // Warning semantics.
   val fatalWarnings = BooleanSetting("-Xfatal-warnings", "Fail the compilation if there are any warnings.")
 
-  // Non-lint warnings
+  // Non-lint warnings.
 
   val warnDeadCode         = BooleanSetting("-Ywarn-dead-code", "Warn when dead code is identified.")
   val warnValueDiscard     = BooleanSetting("-Ywarn-value-discard", "Warn when non-Unit expression results are unused.")
   val warnNumericWiden     = BooleanSetting("-Ywarn-numeric-widen", "Warn when numerics are widened.")
-  // SI-7712, SI-7707 warnUnused not quite ready for prime-time
-  val warnUnused           = BooleanSetting("-Ywarn-unused", "Warn when local and private vals, vars, defs, and types are unused.")
-  // currently considered too noisy for general use
-  val warnUnusedImport     = BooleanSetting("-Ywarn-unused-import", "Warn when imports are unused.")
+
+  object UnusedWarnings extends MultiChoiceEnumeration {
+    val Imports   = Choice("imports",   "Warn if an import selector is not referenced.")
+    val PatVars   = Choice("patvars",   "Warn if a variable bound in a pattern is unused.")
+    val Privates  = Choice("privates",  "Warn if a private member is unused.")
+    val Locals    = Choice("locals",    "Warn if a local definition is unused.")
+    val Params    = Choice("params",    "Warn if a value parameter is unused.")
+    val Implicits = Choice("implicits", "Warn if an implicit parameter is unused.")
+  }
+
+  // The -Ywarn-unused warning group.
+  val warnUnused = MultiChoiceSetting(
+    name    = "-Ywarn-unused",
+    helpArg = "warning",
+    descr   = "Enable or disable specific `unused' warnings",
+    domain  = UnusedWarnings,
+    default = Some(List("_"))
+  )
+
+  def warnUnusedImport    = warnUnused contains UnusedWarnings.Imports
+  def warnUnusedPatVars   = warnUnused contains UnusedWarnings.PatVars
+  def warnUnusedPrivates  = warnUnused contains UnusedWarnings.Privates
+  def warnUnusedLocals    = warnUnused contains UnusedWarnings.Locals
+  def warnUnusedParams    = warnUnused contains UnusedWarnings.Params
+  def warnUnusedImplicits = warnUnused contains UnusedWarnings.Implicits
+
+  BooleanSetting("-Ywarn-unused-import", "Warn when imports are unused.") withPostSetHook { s =>
+    warnUnused.add(s"${if (s) "" else "-"}imports")
+  } //withDeprecationMessage s"Enable -Ywarn-unused:imports"
 
   val warnExtraImplicit    = BooleanSetting("-Ywarn-extra-implicit", "Warn when more than one implicit parameter section is defined.")
 
@@ -60,6 +85,7 @@ trait Warnings {
     val UnsoundMatch           = LintWarning("unsound-match",             "Pattern match may not be typesafe.")
     val StarsAlign             = LintWarning("stars-align",               "Pattern sequence wildcard must align with sequence component.")
     val Constant               = LintWarning("constant",                  "Evaluation of a constant arithmetic expression results in an error.")
+    val Unused                 = LintWarning("unused",                    "Enable -Ywarn-unused:imports,privates,locals,implicits.")
 
     def allLintWarnings = values.toSeq.asInstanceOf[Seq[LintWarning]]
   }
@@ -82,6 +108,7 @@ trait Warnings {
   def warnUnsoundMatch           = lint contains UnsoundMatch
   def warnStarsAlign             = lint contains StarsAlign
   def warnConstant               = lint contains Constant
+  def lintUnused                 = lint contains Unused
 
   // Lint warnings that are currently -Y, but deprecated in that usage
   @deprecated("Use warnAdaptedArgs", since="2.11.2")
@@ -101,7 +128,11 @@ trait Warnings {
     helpArg = "warning",
     descr   = "Enable or disable specific warnings",
     domain  = LintWarnings,
-    default = Some(List("_")))
+    default = Some(List("_"))
+  ).withPostSetHook { s =>
+    val unused = List("imports", "privates", "locals", "implicits")
+    if (s contains Unused) unused.foreach(warnUnused.add)
+  }
 
   allLintWarnings foreach {
     case w if w.yAliased =>
diff --git a/src/compiler/scala/tools/nsc/transform/Delambdafy.scala b/src/compiler/scala/tools/nsc/transform/Delambdafy.scala
index 2e7ab8a887..034cf118d7 100644
--- a/src/compiler/scala/tools/nsc/transform/Delambdafy.scala
+++ b/src/compiler/scala/tools/nsc/transform/Delambdafy.scala
@@ -347,7 +347,7 @@ abstract class Delambdafy extends Transform with TypingTransformers with ast.Tre
     // recursively find methods that refer to 'this' directly or indirectly via references to other methods
     // for each method found add it to the referrers set
     private def refersToThis(symbol: Symbol): Boolean = {
-      var seen = mutable.Set[Symbol]()
+      val seen = mutable.Set[Symbol]()
       def loop(symbol: Symbol): Boolean = {
         if (seen(symbol)) false
         else {
diff --git a/src/compiler/scala/tools/nsc/typechecker/Analyzer.scala b/src/compiler/scala/tools/nsc/typechecker/Analyzer.scala
index 323fe1c171..b8ef439e03 100644
--- a/src/compiler/scala/tools/nsc/typechecker/Analyzer.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/Analyzer.scala
@@ -104,7 +104,7 @@ trait Analyzer extends AnyRef
           for (workItem <- unit.toCheck) workItem()
           if (settings.warnUnusedImport)
             warnUnusedImports(unit)
-          if (settings.warnUnused)
+          if (settings.warnUnused.isSetByUser)
             typer checkUnused unit
         }
         finally {
diff --git a/src/compiler/scala/tools/nsc/typechecker/Contexts.scala b/src/compiler/scala/tools/nsc/typechecker/Contexts.scala
index db3bb9badb..c80bdb180b 100644
--- a/src/compiler/scala/tools/nsc/typechecker/Contexts.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/Contexts.scala
@@ -64,10 +64,8 @@ trait Contexts { self: Analyzer =>
     for (imps <- allImportInfos.remove(unit)) {
       for (imp <- imps.distinct.reverse) {
         val used = allUsedSelectors(imp)
-
-        imp.tree.selectors filterNot (s => isMaskImport(s) || used(s)) foreach { sel =>
-          reporter.warning(imp posOf sel, "Unused import")
-        }
+        for (sel <- imp.tree.selectors if !isMaskImport(sel) && !used(sel))
+          reporter.warning(imp.posOf(sel), "Unused import")
       }
       allUsedSelectors --= imps
     }
@@ -825,7 +823,6 @@ trait Contexts { self: Analyzer =>
     private def collectImplicitImports(imp: ImportInfo): List[ImplicitInfo] = {
       val qual = imp.qual
 
-      val qualSym = qual.tpe.typeSymbol
       val pre = qual.tpe
       def collect(sels: List[ImportSelector]): List[ImplicitInfo] = sels match {
         case List() =>
@@ -1412,7 +1409,8 @@ trait Contexts { self: Analyzer =>
 
   class ImportInfo(val tree: Import, val depth: Int) {
     def pos = tree.pos
-    def posOf(sel: ImportSelector) = tree.pos withPoint sel.namePos
+    def posOf(sel: ImportSelector) =
+      if (sel.namePos >= 0) tree.pos withPoint sel.namePos else tree.pos
 
     /** The prefix expression */
     def qual: Tree = tree.symbol.info match {
diff --git a/src/compiler/scala/tools/nsc/typechecker/RefChecks.scala b/src/compiler/scala/tools/nsc/typechecker/RefChecks.scala
index 7b261810d4..86a1d3f2e4 100644
--- a/src/compiler/scala/tools/nsc/typechecker/RefChecks.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/RefChecks.scala
@@ -323,8 +323,6 @@ abstract class RefChecks extends Transform {
         import pair._
         val member   = low
         val other    = high
-        def memberTp = lowType
-        def otherTp  = highType
 
 //        debuglog(s"Checking validity of ${member.fullLocationString} overriding ${other.fullLocationString}")
 
diff --git a/src/compiler/scala/tools/nsc/typechecker/TypeDiagnostics.scala b/src/compiler/scala/tools/nsc/typechecker/TypeDiagnostics.scala
index 35e6e0099e..cd1dd18768 100644
--- a/src/compiler/scala/tools/nsc/typechecker/TypeDiagnostics.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/TypeDiagnostics.scala
@@ -33,7 +33,7 @@ import scala.annotation.tailrec
  *  @version 1.0
  */
 trait TypeDiagnostics {
-  self: Analyzer =>
+  self: Analyzer with StdAttachments =>
 
   import global._
   import definitions._
@@ -79,6 +79,8 @@ trait TypeDiagnostics {
     prefix + name.decode
   }
 
+  private def atBounded(t: Tree) = t.hasAttachment[AtBoundIdentifierAttachment.type]
+
   /** Does the positioned line assigned to t1 precede that of t2?
    */
   def posPrecedes(p1: Position, p2: Position) = p1.isDefined && p2.isDefined && p1.line < p2.line
@@ -353,7 +355,10 @@ trait TypeDiagnostics {
 
     // functions to manipulate the name
     def preQualify()   = modifyName(trueOwner.fullName + "." + _)
-    def postQualify()  = if (!(postQualifiedWith contains trueOwner)) { postQualifiedWith ::= trueOwner; modifyName(_ + "(in " + trueOwner + ")") }
+    def postQualify()  = if (!(postQualifiedWith contains trueOwner)) {
+      postQualifiedWith ::= trueOwner
+      modifyName(s => s"$s(in $trueOwner)")
+    }
     def typeQualify()  = if (sym.isTypeParameterOrSkolem) postQualify()
     def nameQualify()  = if (trueOwner.isPackageClass) preQualify() else postQualify()
 
@@ -464,13 +469,18 @@ trait TypeDiagnostics {
       context.warning(pos, "imported `%s' is permanently hidden by definition of %s".format(hidden, defn.fullLocationString))
 
     object checkUnused {
-      val ignoreNames: Set[TermName] = Set(TermName("readResolve"), TermName("readObject"), TermName("writeObject"), TermName("writeReplace"))
+      val ignoreNames: Set[TermName] = Set(
+        "readResolve", "readObject", "writeObject", "writeReplace"
+      ).map(TermName(_))
 
       class UnusedPrivates extends Traverser {
         val defnTrees = ListBuffer[MemberDef]()
         val targets   = mutable.Set[Symbol]()
         val setVars   = mutable.Set[Symbol]()
         val treeTypes = mutable.Set[Type]()
+        val atBounds  = mutable.Set[Symbol]()
+        val params    = mutable.Set[Symbol]()
+        val patvars   = mutable.Set[Symbol]()
 
         def defnSymbols = defnTrees.toList map (_.symbol)
         def localVars   = defnSymbols filter (t => t.isLocalToBlock && t.isVar)
@@ -490,20 +500,39 @@ trait TypeDiagnostics {
         )
 
         override def traverse(t: Tree): Unit = {
+          val sym = t.symbol
           t match {
-            case t: MemberDef if qualifies(t.symbol)   => defnTrees += t
-            case t: RefTree if t.symbol ne null        => targets += t.symbol
+            case m: MemberDef if qualifies(t.symbol)   =>
+              defnTrees += m
+              t match {
+                case DefDef(mods@_, name@_, tparams@_, vparamss, tpt@_, rhs@_) if !sym.isAbstract && !sym.isDeprecated && !sym.isMacro =>
+                  if (sym.isPrimaryConstructor)
+                    for (cpa <- sym.owner.constrParamAccessors if cpa.isPrivateLocal) params += cpa
+                  else if (sym.isSynthetic && sym.isImplicit) return
+                  else if (!sym.isConstructor)
+                    for (vs <- vparamss) params ++= vs.map(_.symbol)
+                case _ =>
+              }
+            case CaseDef(pat, guard@_, rhs@_) if settings.warnUnusedPatVars
+                                                       => pat.foreach {
+                                                            // TODO don't warn in isDefinedAt of $anonfun
+                                                            case b @ Bind(n, _) if !atBounded(b) && n != nme.DEFAULT_CASE => patvars += b.symbol
+                                                            case _ =>
+                                                          }
+            case _: RefTree if sym ne null             => targets += sym
             case Assign(lhs, _) if lhs.symbol != null  => setVars += lhs.symbol
+            case Bind(_, _) if atBounded(t)            => atBounds += sym
             case _                                     =>
           }
           // Only record type references which don't originate within the
           // definition of the class being referenced.
           if (t.tpe ne null) {
-            for (tp <- t.tpe ; if !treeTypes(tp) && !currentOwner.ownerChain.contains(tp.typeSymbol)) {
+            for (tp <- t.tpe if !treeTypes(tp) && !currentOwner.ownerChain.contains(tp.typeSymbol)) {
               tp match {
                 case NoType | NoPrefix    =>
                 case NullaryMethodType(_) =>
                 case MethodType(_, _)     =>
+                case SingleType(_, _)     =>
                 case _                    =>
                   log(s"$tp referenced from $currentOwner")
                   treeTypes += tp
@@ -523,55 +552,127 @@ trait TypeDiagnostics {
           && (m.isPrivate || m.isLocalToBlock)
           && !(treeTypes.exists(tp => tp exists (t => t.typeSymbolDirect == m)))
         )
+        def isSyntheticWarnable(sym: Symbol) = (
+          sym.isDefaultGetter 
+        )
+        
         def isUnusedTerm(m: Symbol): Boolean = (
-             (m.isTerm)
-          && (m.isPrivate || m.isLocalToBlock)
+             m.isTerm
+          && (!m.isSynthetic || isSyntheticWarnable(m))
+          && ((m.isPrivate && !(m.isConstructor && m.owner.isAbstract)) || m.isLocalToBlock)
           && !targets(m)
           && !(m.name == nme.WILDCARD)              // e.g. val _ = foo
-          && !ignoreNames(m.name.toTermName)        // serialization methods
+          && (m.isValueParameter || !ignoreNames(m.name.toTermName)) // serialization methods
           && !isConstantType(m.info.resultType)     // subject to constant inlining
           && !treeTypes.exists(_ contains m)        // e.g. val a = new Foo ; new a.Bar
+          //&& !(m.isVal && m.info.resultType =:= typeOf[Unit])      // Unit val is uninteresting
+        )
+        def isUnusedParam(m: Symbol): Boolean = (
+             isUnusedTerm(m)
+          && !m.isDeprecated
+          && !m.owner.isDefaultGetter
+          && !(m.isParamAccessor && (
+            m.owner.isImplicit ||
+            targets.exists(s => s.isParameter
+              && s.name == m.name && s.owner.isConstructor && s.owner.owner == m.owner) // exclude ctor params
+          ))
         )
-        def unusedTypes = defnTrees.toList filter (t => isUnusedType(t.symbol))
-        def unusedTerms = defnTrees.toList filter (v => isUnusedTerm(v.symbol))
+        def sympos(s: Symbol): Int =
+          if (s.pos.isDefined) s.pos.point else if (s.isTerm) s.asTerm.referenced.pos.point else -1
+        def treepos(t: Tree): Int =
+          if (t.pos.isDefined) t.pos.point else sympos(t.symbol)
+
+        def unusedTypes = defnTrees.toList.filter(t => isUnusedType(t.symbol)).sortBy(treepos)
+        def unusedTerms = {
+          val all = defnTrees.toList.filter(v => isUnusedTerm(v.symbol))
+
+          // filter out setters if already warning for getter, indicated by position.
+          // also documentary names in patterns.
+          all.filterNot(v =>
+              v.symbol.isSetter && all.exists(g => g.symbol.isGetter && g.symbol.pos.point == v.symbol.pos.point)
+           || atBounds.exists(x => v.symbol.pos.point == x.pos.point)
+          ).sortBy(treepos)
+        }
         // local vars which are never set, except those already returned in unused
-        def unsetVars = localVars filter (v => !setVars(v) && !isUnusedTerm(v))
+        def unsetVars = localVars.filter(v => !setVars(v) && !isUnusedTerm(v)).sortBy(sympos)
+        def unusedParams = params.toList.filter(isUnusedParam).sortBy(sympos)
+        def inDefinedAt(p: Symbol) = p.owner.isMethod && p.owner.name == nme.isDefinedAt && p.owner.owner.isAnonymousFunction
+        def unusedPatVars = patvars.toList.filter(p => isUnusedTerm(p) && !inDefinedAt(p)).sortBy(sympos)
+      }
+
+      private def warningsEnabled: Boolean = {
+        val ss = settings
+        import ss._
+        warnUnusedPatVars || warnUnusedPrivates || warnUnusedLocals || warnUnusedParams || warnUnusedImplicits
       }
 
-      def apply(unit: CompilationUnit) = {
+      def apply(unit: CompilationUnit): Unit = if (warningsEnabled) {
         val p = new UnusedPrivates
-        p traverse unit.body
-        val unused = p.unusedTerms
-        unused foreach { defn: DefTree =>
-          val sym             = defn.symbol
-          val pos = (
-            if (defn.pos.isDefined) defn.pos
-            else if (sym.pos.isDefined) sym.pos
-            else sym match {
-              case sym: TermSymbol => sym.referenced.pos
-              case _               => NoPosition
+        p.traverse(unit.body)
+        if (settings.warnUnusedLocals || settings.warnUnusedPrivates) {
+          for (defn: DefTree <- p.unusedTerms) {
+            val sym = defn.symbol
+            val pos = (
+              if (defn.pos.isDefined) defn.pos
+              else if (sym.pos.isDefined) sym.pos
+              else sym match {
+                case sym: TermSymbol => sym.referenced.pos
+                case _               => NoPosition
+              }
+            )
+            val why = if (sym.isPrivate) "private" else "local"
+            val what = (
+              if (sym.isDefaultGetter) "default argument"
+              else if (sym.isConstructor) "constructor"
+              else if (
+                  sym.isVar
+               || sym.isGetter && (sym.accessed.isVar || (sym.owner.isTrait && !sym.hasFlag(STABLE)))
+              ) s"var ${sym.name.getterName.decoded}"
+              else if (
+                  sym.isVal
+               || sym.isGetter && (sym.accessed.isVal || (sym.owner.isTrait && sym.hasFlag(STABLE)))
+               || sym.isLazy
+              ) s"val ${sym.name.decoded}"
+              else if (sym.isSetter) s"setter of ${sym.name.getterName.decoded}"
+              else if (sym.isMethod) s"method ${sym.name.decoded}"
+              else if (sym.isModule) s"object ${sym.name.decoded}"
+              else "term"
+            )
+            reporter.warning(pos, s"$why $what in ${sym.owner} is never used")
+          }
+          for (v <- p.unsetVars) {
+            reporter.warning(v.pos, s"local var ${v.name} in ${v.owner} is never set: consider using immutable val")
+          }
+          for (t <- p.unusedTypes) {
+            val sym = t.symbol
+            val wrn = if (sym.isPrivate) settings.warnUnusedPrivates else settings.warnUnusedLocals
+            if (wrn) {
+              val why = if (sym.isPrivate) "private" else "local"
+              reporter.warning(t.pos, s"$why ${sym.fullLocationString} is never used")
             }
-          )
-          val why = if (sym.isPrivate) "private" else "local"
-          val what = (
-            if (sym.isDefaultGetter) "default argument"
-            else if (sym.isConstructor) "constructor"
-            else if (sym.isVar || sym.isGetter && (sym.accessed.isVar || (sym.owner.isTrait && !sym.hasFlag(STABLE)))) "var"
-            else if (sym.isVal || sym.isGetter && (sym.accessed.isVal || (sym.owner.isTrait && sym.hasFlag(STABLE))) || sym.isLazy) "val"
-            else if (sym.isSetter) "setter"
-            else if (sym.isMethod) "method"
-            else if (sym.isModule) "object"
-            else "term"
-          )
-          reporter.warning(pos, s"$why $what in ${sym.owner} is never used")
+          }
         }
-        p.unsetVars foreach { v =>
-          reporter.warning(v.pos, s"local var ${v.name} in ${v.owner} is never set - it could be a val")
+        if (settings.warnUnusedPatVars) {
+          for (v <- p.unusedPatVars)
+            reporter.warning(v.pos, s"pattern var ${v.name} in ${v.owner} is never used; `${v.name}@_' suppresses this warning")
         }
-        p.unusedTypes foreach { t =>
-          val sym = t.symbol
-          val why = if (sym.isPrivate) "private" else "local"
-          reporter.warning(t.pos, s"$why ${sym.fullLocationString} is never used")
+        if (settings.warnUnusedParams || settings.warnUnusedImplicits) {
+          def classOf(s: Symbol): Symbol = if (s.isClass || s == NoSymbol) s else classOf(s.owner)
+          def isImplementation(m: Symbol): Boolean = {
+            val opc = new overridingPairs.Cursor(classOf(m))
+            opc.iterator.exists(pair => pair.low == m)
+          }
+          def isConvention(p: Symbol): Boolean = {
+            (p.name.decoded == "args" && p.owner.isMethod && p.owner.name.decoded == "main") ||
+            (p.tpe =:= typeOf[scala.Predef.DummyImplicit])
+          }
+          def warnable(s: Symbol) = (
+               (settings.warnUnusedParams || s.isImplicit)
+            && !isImplementation(s.owner)
+            && !isConvention(s)
+          )
+          for (s <- p.unusedParams if warnable(s))
+            reporter.warning(s.pos, s"parameter $s in ${s.owner} is never used")
         }
       }
     }
diff --git a/src/compiler/scala/tools/nsc/typechecker/Typers.scala b/src/compiler/scala/tools/nsc/typechecker/Typers.scala
index 05f7deb352..cd4a883a33 100644
--- a/src/compiler/scala/tools/nsc/typechecker/Typers.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/Typers.scala
@@ -4267,7 +4267,8 @@ trait Typers extends Adaptations with Tags with TypersTracking with PatternTyper
         val name = tree.name
         val body = tree.body
         name match {
-          case name: TypeName  => assert(body == EmptyTree, context.unit + " typedBind: " + name.debugString + " " + body + " " + body.getClass)
+          case name: TypeName  =>
+            assert(body == EmptyTree, s"${context.unit} typedBind: ${name.debugString} ${body} ${body.getClass}")
             val sym =
               if (tree.symbol != NoSymbol) tree.symbol
               else {
diff --git a/src/compiler/scala/tools/reflect/FormatInterpolator.scala b/src/compiler/scala/tools/reflect/FormatInterpolator.scala
index 9825acd39f..857b733f59 100644
--- a/src/compiler/scala/tools/reflect/FormatInterpolator.scala
+++ b/src/compiler/scala/tools/reflect/FormatInterpolator.scala
@@ -19,7 +19,6 @@ abstract class FormatInterpolator {
   @inline private def truly(body: => Unit): Boolean = { body ; true }
   @inline private def falsely(body: => Unit): Boolean = { body ; false }
 
-  private def fail(msg: String) = c.abort(c.enclosingPosition, msg)
   private def bail(msg: String) = global.abort(msg)
 
   def interpolate: Tree = c.macroApplication match {
@@ -93,8 +92,8 @@ abstract class FormatInterpolator {
               case '\n' => "\\n"
               case '\f' => "\\f"
               case '\r' => "\\r"
-              case '\"' => "${'\"'}" /* avoid lint warn */ +
-                " or a triple-quoted literal \"\"\"with embedded \" or \\u0022\"\"\""  // $" in future
+              case '\"' => "$" /* avoid lint warn */ +
+                "{'\"'} or a triple-quoted literal \"\"\"with embedded \" or \\u0022\"\"\""
               case '\'' => "'"
               case '\\' => """\\"""
               case x    => "\\u%04x" format x
diff --git a/src/reflect/scala/reflect/internal/StdAttachments.scala b/src/reflect/scala/reflect/internal/StdAttachments.scala
index fc49de1cf6..f72c1eb1b3 100644
--- a/src/reflect/scala/reflect/internal/StdAttachments.scala
+++ b/src/reflect/scala/reflect/internal/StdAttachments.scala
@@ -57,6 +57,12 @@ trait StdAttachments {
    */
   case object BackquotedIdentifierAttachment extends PlainAttachment
 
+  /** Indicates that the host `Ident` has been created from a pattern2 binding, `case x @ p`.
+   *  In the absence of named parameters in patterns, allows nuanced warnings for unused variables.
+   *  Hence, `case X(x = _) =>` would not warn; for now, `case X(x @ _) =>` is documentary if x is unused.
+   */
+  case object AtBoundIdentifierAttachment extends PlainAttachment
+
   /** Identifies trees are either result or intermediate value of for loop desugaring.
    */
   case object ForAttachment extends PlainAttachment
diff --git a/src/reflect/scala/reflect/internal/TreeGen.scala b/src/reflect/scala/reflect/internal/TreeGen.scala
index 4fecaf70df..ade9ee84ac 100644
--- a/src/reflect/scala/reflect/internal/TreeGen.scala
+++ b/src/reflect/scala/reflect/internal/TreeGen.scala
@@ -797,7 +797,7 @@ abstract class TreeGen {
 
   /** Create tree for for-comprehension generator <val pat0 <- rhs0> */
   def mkGenerator(pos: Position, pat: Tree, valeq: Boolean, rhs: Tree)(implicit fresh: FreshNameCreator): Tree = {
-    val pat1 = patvarTransformer.transform(pat)
+    val pat1 = patvarTransformerForFor.transform(pat)
     if (valeq) ValEq(pat1, rhs).setPos(pos)
     else ValFrom(pat1, mkCheckIfRefutable(pat1, rhs)).setPos(pos)
   }
@@ -894,11 +894,15 @@ abstract class TreeGen {
    *    x                  becomes      x @ _
    *    x: T               becomes      x @ (_: T)
    */
-  object patvarTransformer extends Transformer {
+  class PatvarTransformer(forFor: Boolean) extends Transformer {
     override def transform(tree: Tree): Tree = tree match {
-      case Ident(name) if (treeInfo.isVarPattern(tree) && name != nme.WILDCARD) =>
-        atPos(tree.pos)(Bind(name, atPos(tree.pos.focus) (Ident(nme.WILDCARD))))
-      case Typed(id @ Ident(name), tpt) if (treeInfo.isVarPattern(id) && name != nme.WILDCARD) =>
+      case Ident(name) if treeInfo.isVarPattern(tree) && name != nme.WILDCARD =>
+        atPos(tree.pos) {
+          val b = Bind(name, atPos(tree.pos.focus) (Ident(nme.WILDCARD)))
+          if (!forFor && isPatVarWarnable) b
+          else b updateAttachment AtBoundIdentifierAttachment
+        }
+      case Typed(id @ Ident(name), tpt) if treeInfo.isVarPattern(id) && name != nme.WILDCARD =>
         atPos(tree.pos.withPoint(id.pos.point)) {
           Bind(name, atPos(tree.pos.withStart(tree.pos.point)) {
             Typed(Ident(nme.WILDCARD), tpt)
@@ -919,6 +923,15 @@ abstract class TreeGen {
     }
   }
 
+  /** Can be overridden to depend on settings.warnUnusedPatvars. */
+  def isPatVarWarnable: Boolean = true
+
+  /** Not in for comprehensions, whether to warn unused pat vars depends on flag. */
+  object patvarTransformer       extends PatvarTransformer(forFor = false)
+
+  /** Tag pat vars in for comprehensions. */
+  object patvarTransformerForFor extends PatvarTransformer(forFor = true)
+
   // annotate the expression with @unchecked
   def mkUnchecked(expr: Tree): Tree = atPos(expr.pos) {
     // This can't be "Annotated(New(UncheckedClass), expr)" because annotations
diff --git a/src/reflect/scala/reflect/runtime/JavaUniverseForce.scala b/src/reflect/scala/reflect/runtime/JavaUniverseForce.scala
index 9138ed3f02..b455a08036 100644
--- a/src/reflect/scala/reflect/runtime/JavaUniverseForce.scala
+++ b/src/reflect/scala/reflect/runtime/JavaUniverseForce.scala
@@ -40,6 +40,7 @@ trait JavaUniverseForce { self: runtime.JavaUniverse  =>
     this.SAMFunction
     this.DelambdafyTarget
     this.BackquotedIdentifierAttachment
+    this.AtBoundIdentifierAttachment
     this.ForAttachment
     this.SyntheticUnitAttachment
     this.SubpatternsAttachment
diff --git a/src/repl/scala/tools/nsc/interpreter/ILoop.scala b/src/repl/scala/tools/nsc/interpreter/ILoop.scala
index 8be4d159f1..a729ea4f5f 100644
--- a/src/repl/scala/tools/nsc/interpreter/ILoop.scala
+++ b/src/repl/scala/tools/nsc/interpreter/ILoop.scala
@@ -958,17 +958,19 @@ class ILoop(in0: Option[BufferedReader], protected val out: JPrintWriter)
     def withSuppressedSettings[A](body: => A): A = {
       val ss = this.settings
       import ss._
-      val noisy = List(Xprint, Ytyperdebug)
+      val noisy = List(Xprint, Ytyperdebug, browse)
       val noisesome = noisy.exists(!_.isDefault)
-      val current = (Xprint.value, Ytyperdebug.value)
+      val current = (Xprint.value, Ytyperdebug.value, browse.value)
       if (isReplDebug || !noisesome) body
       else {
         this.settings.Xprint.value = List.empty
+        this.settings.browse.value = List.empty
         this.settings.Ytyperdebug.value = false
         try body
         finally {
           Xprint.value       = current._1
           Ytyperdebug.value  = current._2
+          browse.value      = current._3
           intp.global.printTypings = current._2
         }
       }
diff --git a/src/repl/scala/tools/nsc/interpreter/IMain.scala b/src/repl/scala/tools/nsc/interpreter/IMain.scala
index a351d2da95..b977ab0939 100644
--- a/src/repl/scala/tools/nsc/interpreter/IMain.scala
+++ b/src/repl/scala/tools/nsc/interpreter/IMain.scala
@@ -751,11 +751,9 @@ class IMain(initialSettings: Settings, protected val out: JPrintWriter) extends
     lazy val evalClass = load(evalPath)
 
     def evalEither = callEither(resultName) match {
-      case Left(ex) => ex match {
-          case ex: NullPointerException => Right(null)
-          case ex => Left(unwrap(ex))
-      }
-      case Right(result) => Right(result)
+      case Right(result)                 => Right(result)
+      case Left(_: NullPointerException) => Right(null)
+      case Left(e)                       => Left(unwrap(e))
     }
 
     def compile(source: String): Boolean = compileAndSaveRun(label, source)
@@ -789,7 +787,7 @@ class IMain(initialSettings: Settings, protected val out: JPrintWriter) extends
           }
           ((pos, msg)) :: loop(filtered)
       }
-      val warnings = loop(run.reporting.allConditionalWarnings.map{case (pos, (msg, since)) => (pos, msg)})
+      val warnings = loop(run.reporting.allConditionalWarnings.map{ case (pos, (msg, since@_)) => (pos, msg) })
       if (warnings.nonEmpty)
         mostRecentWarnings = warnings
     }
diff --git a/test/files/neg/abstract-inaccessible.check b/test/files/neg/abstract-inaccessible.check
index d56f5691be..739620a4ce 100644
--- a/test/files/neg/abstract-inaccessible.check
+++ b/test/files/neg/abstract-inaccessible.check
@@ -8,7 +8,7 @@ Classes which cannot access Bippy may be unable to override overrideMe.
         ^
 abstract-inaccessible.scala:7: warning: method overrideMeAlso in trait YourTrait references private[foo] trait Bippy.
 Classes which cannot access Bippy may be unable to override overrideMeAlso.
-    def overrideMeAlso(x: Map[Int, Set[Bippy]]) = 5
+    def overrideMeAlso(x: Map[Int, Set[Bippy]]) = x.keys.head
         ^
 error: No warnings can be incurred under -Xfatal-warnings.
 three warnings found
diff --git a/test/files/neg/abstract-inaccessible.flags b/test/files/neg/abstract-inaccessible.flags
index 6c1dd108ae..ea7773e255 100644
--- a/test/files/neg/abstract-inaccessible.flags
+++ b/test/files/neg/abstract-inaccessible.flags
@@ -1 +1 @@
--Xfatal-warnings -Xlint
\ No newline at end of file
+-Xfatal-warnings -Xlint:inaccessible
diff --git a/test/files/neg/abstract-inaccessible.scala b/test/files/neg/abstract-inaccessible.scala
index 3c80f30522..02b458016f 100644
--- a/test/files/neg/abstract-inaccessible.scala
+++ b/test/files/neg/abstract-inaccessible.scala
@@ -4,6 +4,6 @@ package foo {
   trait YourTrait {
     def implementMe(f: Int => (String, Bippy)): Unit
     def overrideMe[T <: Bippy](x: T): T = x
-    def overrideMeAlso(x: Map[Int, Set[Bippy]]) = 5
+    def overrideMeAlso(x: Map[Int, Set[Bippy]]) = x.keys.head
   }
 }
diff --git a/test/files/neg/forgot-interpolator.flags b/test/files/neg/forgot-interpolator.flags
index 7949c2afa2..b0d7bc25cb 100644
--- a/test/files/neg/forgot-interpolator.flags
+++ b/test/files/neg/forgot-interpolator.flags
@@ -1 +1 @@
--Xlint -Xfatal-warnings
+-Xlint:missing-interpolator -Xfatal-warnings
diff --git a/test/files/neg/overloaded-implicit.flags b/test/files/neg/overloaded-implicit.flags
index 9c1e74e4ef..e04a4228ba 100644
--- a/test/files/neg/overloaded-implicit.flags
+++ b/test/files/neg/overloaded-implicit.flags
@@ -1 +1 @@
--Xlint -Xfatal-warnings -Xdev
+-Xlint:poly-implicit-overload -Xfatal-warnings -Xdev
diff --git a/test/files/neg/t1980.flags b/test/files/neg/t1980.flags
index 7949c2afa2..cdc464a47d 100644
--- a/test/files/neg/t1980.flags
+++ b/test/files/neg/t1980.flags
@@ -1 +1 @@
--Xlint -Xfatal-warnings
+-Xlint:by-name-right-associative -Xfatal-warnings
diff --git a/test/files/neg/t4877.flags b/test/files/neg/t4877.flags
deleted file mode 100644
index 7ccd56103a..0000000000
--- a/test/files/neg/t4877.flags
+++ /dev/null
@@ -1 +0,0 @@
--Xlint
\ No newline at end of file
diff --git a/test/files/neg/t6567.flags b/test/files/neg/t6567.flags
index e93641e931..076333a011 100644
--- a/test/files/neg/t6567.flags
+++ b/test/files/neg/t6567.flags
@@ -1 +1 @@
--Xlint -Xfatal-warnings
\ No newline at end of file
+-Xlint:option-implicit -Xfatal-warnings
diff --git a/test/files/neg/t6675.flags b/test/files/neg/t6675.flags
index 2843ea9efc..c6bfaf1f64 100644
--- a/test/files/neg/t6675.flags
+++ b/test/files/neg/t6675.flags
@@ -1 +1 @@
--deprecation -Xlint -Xfatal-warnings
\ No newline at end of file
+-deprecation -Xfatal-warnings
diff --git a/test/files/neg/t7860.check b/test/files/neg/t7860.check
new file mode 100644
index 0000000000..9b9d86c89d
--- /dev/null
+++ b/test/files/neg/t7860.check
@@ -0,0 +1,9 @@
+t7860.scala:5: warning: private class for your eyes only in object Test is never used
+  private implicit class `for your eyes only`(i: Int) {       // warn
+                         ^
+t7860.scala:31: warning: private class C in object Test3 is never used
+  private implicit class C(val i: Int) extends AnyVal {       // warn
+                         ^
+error: No warnings can be incurred under -Xfatal-warnings.
+two warnings found
+one error found
diff --git a/test/files/neg/t7860.flags b/test/files/neg/t7860.flags
new file mode 100644
index 0000000000..6ff0dea0b2
--- /dev/null
+++ b/test/files/neg/t7860.flags
@@ -0,0 +1 @@
+-Xfatal-warnings -Ywarn-unused:privates
diff --git a/test/files/neg/t7860.scala b/test/files/neg/t7860.scala
new file mode 100644
index 0000000000..6cc0d3e7f5
--- /dev/null
+++ b/test/files/neg/t7860.scala
@@ -0,0 +1,42 @@
+
+class Test
+
+object Test {
+  private implicit class `for your eyes only`(i: Int) {       // warn
+    def f = i
+  }
+}
+
+class Test2 {
+  import Test2._
+  println(5.toStr)
+}
+ 
+object Test2 {
+  // was: warning: private object in object Test2 is never used
+  // i.e. synthetic object C
+  private implicit class C(val i: Int) extends AnyVal {       // no warn
+    def toStr = i.toString
+  }
+}
+
+class Test3 {
+  import Test3._
+  //println(5.toStr)
+}
+ 
+object Test3 {
+  // was: warning: private object in object Test2 is never used
+  // i.e. synthetic object C
+  private implicit class C(val i: Int) extends AnyVal {       // warn
+    def toStr = i.toString
+  }
+}
+
+object Test4 {
+  class A { class B }
+
+  private val a: A = new A
+
+  def b = (new a.B).##
+}
diff --git a/test/files/neg/warn-unused-implicits.check b/test/files/neg/warn-unused-implicits.check
new file mode 100644
index 0000000000..4cc5836800
--- /dev/null
+++ b/test/files/neg/warn-unused-implicits.check
@@ -0,0 +1,9 @@
+warn-unused-implicits.scala:11: warning: parameter value s in method f is never used
+       )(implicit s: String): Int = {  // warn
+                  ^
+warn-unused-implicits.scala:31: warning: parameter value s in method i is never used
+  def i(implicit s: String, t: Int) = t           // yes, warn
+                 ^
+error: No warnings can be incurred under -Xfatal-warnings.
+two warnings found
+one error found
diff --git a/test/files/neg/warn-unused-implicits.flags b/test/files/neg/warn-unused-implicits.flags
new file mode 100644
index 0000000000..18169f3218
--- /dev/null
+++ b/test/files/neg/warn-unused-implicits.flags
@@ -0,0 +1 @@
+-Ywarn-unused:implicits -Xfatal-warnings
diff --git a/test/files/neg/warn-unused-implicits.scala b/test/files/neg/warn-unused-implicits.scala
new file mode 100644
index 0000000000..54f924eac0
--- /dev/null
+++ b/test/files/neg/warn-unused-implicits.scala
@@ -0,0 +1,32 @@
+
+trait InterFace {
+  /** Call something. */
+  def call(a: Int, b: String, c: Double)(implicit s: String): Int
+}
+
+trait BadAPI extends InterFace {
+  def f(a: Int,
+        b: String,
+        c: Double
+       )(implicit s: String): Int = {  // warn
+    println(b + c)
+    a
+  }
+  @deprecated ("no warn in deprecated API", since="yesterday")
+  def g(a: Int,
+        b: String,
+        c: Double
+       )(implicit s: String): Int = {  // no warn
+    println(b + c)
+    a
+  }
+  override def call(a: Int,
+                    b: String,
+                    c: Double
+                   )(implicit s: String): Int = {  // no warn, required by superclass
+    println(b + c)
+    a
+  }
+
+  def i(implicit s: String, t: Int) = t           // yes, warn
+}
diff --git a/test/files/neg/warn-unused-imports.check b/test/files/neg/warn-unused-imports.check
index 0a53d7a9cd..29d73a6264 100644
--- a/test/files/neg/warn-unused-imports.check
+++ b/test/files/neg/warn-unused-imports.check
@@ -51,5 +51,8 @@ warn-unused-imports_2.scala:149: warning: Unused import
 warn-unused-imports_2.scala:150: warning: Unused import
     import p1.A                         // warn
               ^
-16 warnings found
+warn-unused-imports_2.scala:158: warning: Unused import
+  def x = Macro.f  // warn, not crash
+                ^
+17 warnings found
 one error found
diff --git a/test/files/neg/warn-unused-imports.flags b/test/files/neg/warn-unused-imports.flags
index 24db705df1..c4e11e7fe7 100644
--- a/test/files/neg/warn-unused-imports.flags
+++ b/test/files/neg/warn-unused-imports.flags
@@ -1 +1 @@
--Xfatal-warnings -Ywarn-unused-import
+-Xfatal-warnings -Ywarn-unused:imports
diff --git a/test/files/neg/warn-unused-imports/sample_1.scala b/test/files/neg/warn-unused-imports/sample_1.scala
index d2f86239db..eea4d0eb4c 100644
--- a/test/files/neg/warn-unused-imports/sample_1.scala
+++ b/test/files/neg/warn-unused-imports/sample_1.scala
@@ -15,3 +15,18 @@ object Sample {
   def f(x: X) = ???
   def g(y: Y) = ???
 }
+
+import scala.language.experimental.macros
+import scala.reflect.macros.blackbox.Context
+ 
+object Macro {
+  def f: Int = macro fImpl
+  def fImpl(c: Context): c.Tree = {
+    import c.universe._
+ 
+    q"""
+     import scala.util.Random
+     42 // TODO randomize
+    """
+  }
+}
diff --git a/test/files/neg/warn-unused-imports/warn-unused-imports_2.scala b/test/files/neg/warn-unused-imports/warn-unused-imports_2.scala
index ded1186209..58fe0131d9 100644
--- a/test/files/neg/warn-unused-imports/warn-unused-imports_2.scala
+++ b/test/files/neg/warn-unused-imports/warn-unused-imports_2.scala
@@ -96,7 +96,7 @@ trait Warn {
 trait Nested {
   {
     import p1._   // warn
-    trait Warn {  // warn about unused local trait for good measure
+    trait Warn {  // don't warn about unused local trait with -Ywarn-unused:imports
       import p2._
       println(new A)
       println("abc".bippy)
@@ -153,3 +153,7 @@ trait Outsiders {
     //Future("abc".bippy)
   }
 }
+
+class MacroClient {
+  def x = Macro.f  // warn, not crash
+}
diff --git a/test/files/neg/warn-unused-params.check b/test/files/neg/warn-unused-params.check
new file mode 100644
index 0000000000..373417ce08
--- /dev/null
+++ b/test/files/neg/warn-unused-params.check
@@ -0,0 +1,18 @@
+warn-unused-params.scala:9: warning: parameter value b in method f is never used
+        b: String,               // warn
+        ^
+warn-unused-params.scala:32: warning: parameter value s in method i is never used
+  def i(implicit s: String) = 42           // yes, warn
+                 ^
+warn-unused-params.scala:49: warning: parameter value u in class Unusing is never used
+class Unusing(u: Int) {       // warn
+              ^
+warn-unused-params.scala:59: warning: parameter value s in class CaseyAtTheBat is never used
+case class CaseyAtTheBat(k: Int)(s: String)        // warn
+                                 ^
+warn-unused-params.scala:62: warning: parameter value readResolve in method f is never used
+  def f(readResolve: Int) = 42           // warn
+        ^
+error: No warnings can be incurred under -Xfatal-warnings.
+5 warnings found
+one error found
diff --git a/test/files/neg/warn-unused-params.flags b/test/files/neg/warn-unused-params.flags
new file mode 100644
index 0000000000..795fb74272
--- /dev/null
+++ b/test/files/neg/warn-unused-params.flags
@@ -0,0 +1 @@
+-Ywarn-unused:params -Xfatal-warnings
diff --git a/test/files/neg/warn-unused-params.scala b/test/files/neg/warn-unused-params.scala
new file mode 100644
index 0000000000..b166e8fae6
--- /dev/null
+++ b/test/files/neg/warn-unused-params.scala
@@ -0,0 +1,69 @@
+
+trait InterFace {
+  /** Call something. */
+  def call(a: Int, b: String, c: Double): Int
+}
+
+trait BadAPI extends InterFace {
+  def f(a: Int,
+        b: String,               // warn
+        c: Double): Int = {
+    println(c)
+    a
+  }
+  @deprecated ("no warn in deprecated API", since="yesterday")
+  def g(a: Int,
+        b: String,               // no warn
+        c: Double): Int = {
+    println(c)
+    a
+  }
+  override def call(a: Int,
+                    b: String,               // no warn, required by superclass
+                    c: Double): Int = {
+    println(c)
+    a
+  }
+
+  def meth(x: Int) = x
+
+  override def equals(other: Any): Boolean = true  // no warn
+
+  def i(implicit s: String) = 42           // yes, warn
+
+  /*
+  def future(x: Int): Int = {
+    val y = 42
+    val x = y               // maybe option to warn only if shadowed
+    x
+  }
+  */
+}
+
+// mustn't alter warnings in super
+trait PoorClient extends BadAPI {
+  override def meth(x: Int) = ???       // no warn
+  override def f(a: Int, b: String, c: Double): Int = a + b.toInt + c.toInt
+}
+
+class Unusing(u: Int) {       // warn
+  def f = ???
+}
+
+class Valuing(val u: Int)        // no warn
+
+class Revaluing(u: Int) { def f = u } // no warn
+
+case class CaseyKasem(k: Int)        // no warn
+
+case class CaseyAtTheBat(k: Int)(s: String)        // warn
+
+trait Ignorance {
+  def f(readResolve: Int) = 42           // warn
+}
+
+class Reusing(u: Int) extends Unusing(u)   // no warn
+
+class Main {
+  def main(args: Array[String]): Unit = println("hello, args")  // no warn
+}
diff --git a/test/files/neg/warn-unused-patvars.check b/test/files/neg/warn-unused-patvars.check
new file mode 100644
index 0000000000..2665126a36
--- /dev/null
+++ b/test/files/neg/warn-unused-patvars.check
@@ -0,0 +1,12 @@
+warn-unused-patvars.scala:9: warning: private val x in trait Boundings is never used
+  private val x = 42                      // warn, sanity check
+              ^
+warn-unused-patvars.scala:28: warning: local val x in method v is never used
+    val D(x) = d                          // warn, fixme
+         ^
+warn-unused-patvars.scala:32: warning: local val x in method w is never used
+    val D(x @ _) = d                      // warn, fixme (valdef pos is different)
+         ^
+error: No warnings can be incurred under -Xfatal-warnings.
+three warnings found
+one error found
diff --git a/test/files/neg/warn-unused-patvars.flags b/test/files/neg/warn-unused-patvars.flags
new file mode 100644
index 0000000000..d5bd86a658
--- /dev/null
+++ b/test/files/neg/warn-unused-patvars.flags
@@ -0,0 +1 @@
+-Ywarn-unused:-patvars,_ -Xfatal-warnings
diff --git a/test/files/neg/warn-unused-patvars.scala b/test/files/neg/warn-unused-patvars.scala
new file mode 100644
index 0000000000..3d35dfedd6
--- /dev/null
+++ b/test/files/neg/warn-unused-patvars.scala
@@ -0,0 +1,53 @@
+
+// verify no warning when -Ywarn-unused:-patvars
+
+case class C(a: Int, b: String, c: Option[String])
+case class D(a: Int)
+
+trait Boundings {
+
+  private val x = 42                      // warn, sanity check
+
+  def c = C(42, "hello", Some("world"))
+  def d = D(42)
+
+  def f() = {
+    val C(x, y, Some(z)) = c              // no warn
+    17
+  }
+  def g() = {
+    val C(x @ _, y @ _, Some(z @ _)) = c  // no warn
+    17
+  }
+  def h() = {
+    val C(x @ _, y @ _, z @ Some(_)) = c  // no warn for z?
+    17
+  }
+
+  def v() = {
+    val D(x) = d                          // warn, fixme
+    17
+  }
+  def w() = {
+    val D(x @ _) = d                      // warn, fixme (valdef pos is different)
+    17
+  }
+
+}
+
+trait Forever {
+  def f = {
+    val t = Option((17, 42))
+    for {
+      ns <- t
+      (i, j) = ns                        // no warn
+    } yield (i + j)
+  }
+  def g = {
+    val t = Option((17, 42))
+    for {
+      ns <- t
+      (i, j) = ns                        // no warn
+    } yield 42
+  }
+}
diff --git a/test/files/neg/warn-unused-privates.check b/test/files/neg/warn-unused-privates.check
index 2e93f338bb..2a88d3e6c3 100644
--- a/test/files/neg/warn-unused-privates.check
+++ b/test/files/neg/warn-unused-privates.check
@@ -1,66 +1,120 @@
 warn-unused-privates.scala:2: warning: private constructor in class Bippy is never used
   private def this(c: Int) = this(c, c)           // warn
               ^
-warn-unused-privates.scala:4: warning: private method in class Bippy is never used
+warn-unused-privates.scala:4: warning: private method boop in class Bippy is never used
   private def boop(x: Int)            = x+a+b     // warn
               ^
-warn-unused-privates.scala:6: warning: private val in class Bippy is never used
+warn-unused-privates.scala:6: warning: private val MILLIS2 in class Bippy is never used
   final private val MILLIS2: Int      = 1000      // warn
                     ^
-warn-unused-privates.scala:13: warning: private val in object Bippy is never used
+warn-unused-privates.scala:13: warning: private val HEY_INSTANCE in object Bippy is never used
   private val HEY_INSTANCE: Int = 1000    // warn
               ^
-warn-unused-privates.scala:14: warning: private val in object Bippy is never used
+warn-unused-privates.scala:14: warning: private val BOOL in object Bippy is never used
   private lazy val BOOL: Boolean = true   // warn
                    ^
-warn-unused-privates.scala:36: warning: private val in class Boppy is never used
+warn-unused-privates.scala:36: warning: private val hummer in class Boppy is never used
   private val hummer = "def" // warn
               ^
-warn-unused-privates.scala:43: warning: private var in trait Accessors is never used
+warn-unused-privates.scala:43: warning: private var v1 in trait Accessors is never used
   private var v1: Int = 0 // warn
               ^
-warn-unused-privates.scala:44: warning: private var in trait Accessors is never used
+warn-unused-privates.scala:44: warning: private var v2 in trait Accessors is never used
   private var v2: Int = 0 // warn, never set
               ^
-warn-unused-privates.scala:45: warning: private var in trait Accessors is never used
+warn-unused-privates.scala:45: warning: private var v3 in trait Accessors is never used
   private var v3: Int = 0 // warn, never got
               ^
-warn-unused-privates.scala:57: warning: private default argument in trait DefaultArgs is never used
+warn-unused-privates.scala:56: warning: private var s1 in class StableAccessors is never used
+  private var s1: Int = 0 // warn
+              ^
+warn-unused-privates.scala:57: warning: private setter of s2 in class StableAccessors is never used
+  private var s2: Int = 0 // warn, never set
+              ^
+warn-unused-privates.scala:58: warning: private var s3 in class StableAccessors is never used
+  private var s3: Int = 0 // warn, never got
+              ^
+warn-unused-privates.scala:70: warning: private default argument in trait DefaultArgs is never used
   private def bippy(x1: Int, x2: Int = 10, x3: Int = 15): Int = x1 + x2 + x3
                              ^
-warn-unused-privates.scala:57: warning: private default argument in trait DefaultArgs is never used
+warn-unused-privates.scala:70: warning: private default argument in trait DefaultArgs is never used
   private def bippy(x1: Int, x2: Int = 10, x3: Int = 15): Int = x1 + x2 + x3
                                            ^
-warn-unused-privates.scala:68: warning: local var in method f0 is never used
+warn-unused-privates.scala:86: warning: local var x in method f0 is never used
     var x = 1 // warn
         ^
-warn-unused-privates.scala:75: warning: local val in method f1 is never used
+warn-unused-privates.scala:93: warning: local val b in method f1 is never used
     val b = new Outer // warn
         ^
-warn-unused-privates.scala:85: warning: private object in object Types is never used
+warn-unused-privates.scala:103: warning: private object Dongo in object Types is never used
   private object Dongo { def f = this } // warn
                  ^
-warn-unused-privates.scala:95: warning: local object in method l1 is never used
+warn-unused-privates.scala:113: warning: local object HiObject in method l1 is never used
     object HiObject { def f = this } // warn
            ^
-warn-unused-privates.scala:79: warning: local var x in method f2 is never set - it could be a val
+warn-unused-privates.scala:136: warning: private method x_= in class OtherNames is never used
+  private def x_=(i: Int): Unit = ???
+              ^
+warn-unused-privates.scala:137: warning: private method x in class OtherNames is never used
+  private def x: Int = 42
+              ^
+warn-unused-privates.scala:138: warning: private method y_= in class OtherNames is never used
+  private def y_=(i: Int): Unit = ???
+              ^
+warn-unused-privates.scala:153: warning: local val x in method f is never used
+    val C(x, y, Some(z)) = c              // warn
+          ^
+warn-unused-privates.scala:153: warning: local val y in method f is never used
+    val C(x, y, Some(z)) = c              // warn
+             ^
+warn-unused-privates.scala:153: warning: local val z in method f is never used
+    val C(x, y, Some(z)) = c              // warn
+                     ^
+warn-unused-privates.scala:161: warning: local val z in method h is never used
+    val C(x @ _, y @ _, z @ Some(_)) = c  // warn for z?
+                        ^
+warn-unused-privates.scala:166: warning: local val x in method v is never used
+    val D(x) = d                          // warn
+         ^
+warn-unused-privates.scala:170: warning: local val x in method w is never used
+    val D(x @ _) = d                      // warn, fixme (valdef pos is different)
+         ^
+warn-unused-privates.scala:97: warning: local var x in method f2 is never set: consider using immutable val
     var x = 100 // warn about it being a var
         ^
-warn-unused-privates.scala:86: warning: private class Bar1 in object Types is never used
+warn-unused-privates.scala:104: warning: private class Bar1 in object Types is never used
   private class Bar1 // warn
                 ^
-warn-unused-privates.scala:88: warning: private type Alias1 in object Types is never used
+warn-unused-privates.scala:106: warning: private type Alias1 in object Types is never used
   private type Alias1 = String // warn
                ^
-warn-unused-privates.scala:96: warning: local class Hi is never used
+warn-unused-privates.scala:114: warning: local class Hi is never used
     class Hi { // warn
           ^
-warn-unused-privates.scala:100: warning: local class DingDongDoobie is never used
+warn-unused-privates.scala:118: warning: local class DingDongDoobie is never used
     class DingDongDoobie // warn
           ^
-warn-unused-privates.scala:103: warning: local type OtherThing is never used
+warn-unused-privates.scala:121: warning: local type OtherThing is never used
     type OtherThing = String // warn
          ^
+warn-unused-privates.scala:216: warning: private class for your eyes only in object not even using companion privates is never used
+  private implicit class `for your eyes only`(i: Int) {  // warn
+                         ^
+warn-unused-privates.scala:201: warning: pattern var z in method f is never used; `z@_' suppresses this warning
+    case z => "warn"
+         ^
+warn-unused-privates.scala:208: warning: pattern var z in method f is never used; `z@_' suppresses this warning
+    case Some(z) => "warn"
+              ^
+warn-unused-privates.scala:20: warning: parameter value msg0 in class B3 is never used
+class B3(msg0: String) extends A("msg")
+         ^
+warn-unused-privates.scala:136: warning: parameter value i in method x_= is never used
+  private def x_=(i: Int): Unit = ???
+                  ^
+warn-unused-privates.scala:138: warning: parameter value i in method y_= is never used
+  private def y_=(i: Int): Unit = ???
+                  ^
 error: No warnings can be incurred under -Xfatal-warnings.
-21 warnings found
+39 warnings found
 one error found
diff --git a/test/files/neg/warn-unused-privates.scala b/test/files/neg/warn-unused-privates.scala
index 2eda280d40..f7640927fb 100644
--- a/test/files/neg/warn-unused-privates.scala
+++ b/test/files/neg/warn-unused-privates.scala
@@ -52,6 +52,19 @@ trait Accessors {
   }
 }
 
+class StableAccessors {
+  private var s1: Int = 0 // warn
+  private var s2: Int = 0 // warn, never set
+  private var s3: Int = 0 // warn, never got
+  private var s4: Int = 0 // no warn
+
+  def bippy(): Int = {
+    s3 = 5
+    s4 = 6
+    s2 + s4
+  }
+}
+
 trait DefaultArgs {
   // warn about default getters for x2 and x3
   private def bippy(x1: Int, x2: Int = 10, x3: Int = 15): Int = x1 + x2 + x3
@@ -59,6 +72,11 @@ trait DefaultArgs {
   def boppy() = bippy(5, 100, 200)
 }
 
+/* SI-7707 Both usages warn default arg because using PrivateRyan.apply, not new.
+case class PrivateRyan private (ryan: Int = 42) { def f = PrivateRyan() }
+object PrivateRyan { def f = PrivateRyan() }
+*/
+
 class Outer {
   class Inner
 }
@@ -104,3 +122,105 @@ object Types {
     (new Bippy): Something
   }
 }
+
+trait Underwarn {
+  def f(): Seq[Int]
+
+  def g() = {
+    val Seq(_, _) = f()  // no warn
+    true
+  }
+}
+
+class OtherNames {
+  private def x_=(i: Int): Unit = ???
+  private def x: Int = 42
+  private def y_=(i: Int): Unit = ???
+  private def y: Int = 42
+
+  def f = y
+}
+
+case class C(a: Int, b: String, c: Option[String])
+case class D(a: Int)
+
+trait Boundings {
+
+  def c = C(42, "hello", Some("world"))
+  def d = D(42)
+
+  def f() = {
+    val C(x, y, Some(z)) = c              // warn
+    17
+  }
+  def g() = {
+    val C(x @ _, y @ _, Some(z @ _)) = c  // no warn
+    17
+  }
+  def h() = {
+    val C(x @ _, y @ _, z @ Some(_)) = c  // warn for z?
+    17
+  }
+
+  def v() = {
+    val D(x) = d                          // warn
+    17
+  }
+  def w() = {
+    val D(x @ _) = d                      // warn, fixme (valdef pos is different)
+    17
+  }
+
+}
+
+trait Forever {
+  def f = {
+    val t = Option((17, 42))
+    for {
+      ns <- t
+      (i, j) = ns                        // no warn
+    } yield (i + j)
+  }
+  def g = {
+    val t = Option((17, 42))
+    for {
+      ns <- t
+      (i, j) = ns                        // warn, fixme
+    } yield 42                           // val emitted only if needed, hence nothing unused
+  }
+}
+
+trait Ignorance {
+  private val readResolve = 42      // ignore
+}
+
+trait CaseyKasem {
+  def f = 42 match {
+    case x if x < 25 => "no warn"
+    case y if toString.nonEmpty => "no warn" + y
+    case z => "warn"
+  }
+}
+trait CaseyAtTheBat {
+  def f = Option(42) match {
+    case Some(x) if x < 25 => "no warn"
+    case Some(y @ _) if toString.nonEmpty => "no warn"
+    case Some(z) => "warn"
+    case None => "no warn"
+  }
+}
+
+class `not even using companion privates`
+
+object `not even using companion privates` {
+  private implicit class `for your eyes only`(i: Int) {  // warn
+    def f = i
+  }
+}
+
+class `no warn in patmat anonfun isDefinedAt` {
+  def f(pf: PartialFunction[String, Int]) = pf("42")
+  def g = f {
+    case s => s.length        // no warn (used to warn case s => true in isDefinedAt)
+  }
+}
diff --git a/test/files/pos/t6091.scala b/test/files/pos/t6091.scala
index 72e663ec3b..0318640e7b 100644
--- a/test/files/pos/t6091.scala
+++ b/test/files/pos/t6091.scala
@@ -1,6 +1,6 @@
-object Foo { def eq(x:Int) = x }
+object Foo { def eq(x: Int) = x }
 
-class X { def ==(other: String) = true }
+class X { def ==(other: String) = other.nonEmpty }
 
 object Test {
   def main(args: Array[String]): Unit = {
diff --git a/test/files/pos/t8013.flags b/test/files/pos/t8013.flags
index 3955bb6710..219723cec9 100644
--- a/test/files/pos/t8013.flags
+++ b/test/files/pos/t8013.flags
@@ -1 +1 @@
--Xfatal-warnings -Xlint:-infer-any,_
+-Xfatal-warnings -Xlint:missing-interpolator
diff --git a/test/files/pos/t8040.flags b/test/files/pos/t8040.flags
new file mode 100644
index 0000000000..3126c059f0
--- /dev/null
+++ b/test/files/pos/t8040.flags
@@ -0,0 +1 @@
+-Xfatal-warnings -Ywarn-unused:params
diff --git a/test/files/pos/t8040.scala b/test/files/pos/t8040.scala
new file mode 100644
index 0000000000..3e01014ab4
--- /dev/null
+++ b/test/files/pos/t8040.scala
@@ -0,0 +1,13 @@
+
+object Test {
+  implicit class C(val sc: StringContext) {                 // no warn unused sc
+    def c(args: Any*): String = "c?" + args.mkString(",")   // would warn unused args
+  }
+
+  def f(implicit x: DummyImplicit) = 42                     // no warn DummyImplicit
+
+
+  def f(x: Int)(y: Int = 1) = x + y                         // no warn default getter
+
+  def g(@deprecated("","") x: Int) = 42                     // no warn deprecated
+}