Discourage multi-argument infix syntax: lint applications (x op (a, b)), also lint operator-name definitions

build.sbt

@@ -374,6 +374,7 @@ lazy val commonSettings = instanceSettings ++ clearSourceAndResourceDirectories
   connectInput in run := true,
   //scalacOptions in Compile += "-Xlint:-deprecation,-inaccessible,-nonlocal-return,-valpattern,_",
   //scalacOptions in Compile ++= Seq("-Xmaxerrs", "5", "-Xmaxwarns", "5"),
+  scalacOptions in Compile += "-Wconf:cat=unchecked&msg=The outer reference in this type test cannot be checked at run time.:ws",
   scalacOptions in Compile in doc ++= Seq(
     "-doc-footer", "epfl",
     "-diagrams",

src/compiler/scala/reflect/macros/compiler/Errors.scala

@@ -100,7 +100,7 @@ trait Errors extends Traces {
 
     private def showMeth(pss: List[List[Symbol]], restpe: Type, abbreviate: Boolean, untype: Boolean) = {
       def preprocess(tpe: Type) = if (untype) untypeMetalevel(tpe) else tpe
-      var pssPart = (pss map (ps => ps map (p => p.defStringSeenAs(preprocess(p.info))) mkString ("(", ", ", ")"))).mkString
+      var pssPart = pss.map(_.map(p => p.defStringSeenAs(preprocess(p.info))).mkString("(", ", ", ")")).mkString
       if (abbreviate) pssPart = abbreviateCoreAliases(pssPart)
       var retPart = preprocess(restpe).toString
       if (abbreviate || macroDdef.tpt.tpe == null) retPart = abbreviateCoreAliases(retPart)

src/compiler/scala/reflect/reify/utils/SymbolTables.scala

@@ -58,6 +58,7 @@ trait SymbolTables {
         case None => EmptyTree
       }
 
+    @deprecated("use add instead", since="2.13.3")
     def +(sym: Symbol, name: TermName, reification: Tree): SymbolTable = add(sym, name, reification)
     def +(symDef: Tree): SymbolTable = add(symDef)
     def ++(symDefs: IterableOnce[Tree]): SymbolTable = symDefs.iterator.foldLeft(this)((symtab, symDef) => symtab.add(symDef))

src/compiler/scala/tools/nsc/Reporting.scala

@@ -229,7 +229,7 @@ trait Reporting extends internal.Reporting { self: ast.Positions with Compilatio
         )
       reportedFeature += featureTrait
 
-      val msg = s"$featureDesc $req be enabled\nby making the implicit value $fqname visible.$explain" replace ("#", construct)
+      val msg = s"$featureDesc $req be enabled\nby making the implicit value $fqname visible.$explain".replace("#", construct)
       // maybe pos.source.file.file.getParentFile.getName or Path(source.file.file).parent.name
       def parentFileName(source: internal.util.SourceFile) =
         Option(java.nio.file.Paths.get(source.path).getParent).map(_.getFileName.toString)
@@ -382,6 +382,7 @@ object Reporting {
     object LintBynameImplicit extends Lint; add(LintBynameImplicit)
     object LintRecurseWithDefault extends Lint; add(LintRecurseWithDefault)
     object LintUnitSpecialization extends Lint; add(LintUnitSpecialization)
+    object LintMultiargInfix extends Lint; add(LintMultiargInfix)
 
     sealed trait Feature extends WarningCategory { override def summaryCategory: WarningCategory = Feature }
     object Feature extends Feature { override def includes(o: WarningCategory): Boolean = o.isInstanceOf[Feature] }; add(Feature)

src/compiler/scala/tools/nsc/ast/TreeDSL.scala

@@ -13,6 +13,7 @@
 package scala.tools.nsc
 package ast
 
+import scala.annotation.unused
 import scala.language.implicitConversions
 
 /** A DSL for generating scala code.  The goal is that the
@@ -82,9 +83,13 @@ trait TreeDSL {
       def INT_-   (other: Tree)     = fn(target, getMember(IntClass, nme.MINUS), other)
 
       // generic operations on ByteClass, IntClass, LongClass
+      @unused("avoid warning for multiple parameters")
       def GEN_|   (other: Tree, kind: ClassSymbol)  = fn(target, getMember(kind, nme.OR), other)
+      @unused("avoid warning for multiple parameters")
       def GEN_&   (other: Tree, kind: ClassSymbol)  = fn(target, getMember(kind, nme.AND), other)
+      @unused("avoid warning for multiple parameters")
       def GEN_==  (other: Tree, kind: ClassSymbol)  = fn(target, getMember(kind, nme.EQ), other)
+      @unused("avoid warning for multiple parameters")
       def GEN_!=  (other: Tree, kind: ClassSymbol)  = fn(target, getMember(kind, nme.NE), other)
 
       /** Apply, Select, Match **/

src/compiler/scala/tools/nsc/ast/TreeGen.scala

@@ -364,7 +364,7 @@ abstract class TreeGen extends scala.reflect.internal.TreeGen with TreeDSL {
   }
 
   def expandFunction(localTyper: analyzer.Typer)(fun: Function, inConstructorFlag: Long): Tree = {
-    val anonClass = fun.symbol.owner newAnonymousFunctionClass(fun.pos, inConstructorFlag)
+    val anonClass = fun.symbol.owner.newAnonymousFunctionClass(fun.pos, inConstructorFlag)
     val parents = if (isFunctionType(fun.tpe)) {
       anonClass addAnnotation SerialVersionUIDAnnotation
       addSerializable(abstractFunctionType(fun.vparams.map(_.symbol.tpe), fun.body.tpe.deconst))

src/compiler/scala/tools/nsc/ast/parser/Parsers.scala

@@ -16,12 +16,11 @@
 package scala.tools.nsc
 package ast.parser
 
-import scala.collection.mutable
-import mutable.ListBuffer
-import scala.reflect.internal.{Precedence, ModifierFlags => Flags}
+import scala.annotation.tailrec
+import scala.collection.mutable, mutable.ListBuffer
+import scala.reflect.internal.{ModifierFlags => Flags, Precedence}
 import scala.reflect.internal.util.{FreshNameCreator, ListOfNil, Position, SourceFile}
 import Tokens._
-import scala.annotation.tailrec
 import scala.tools.nsc.Reporting.WarningCategory
 
 /** Historical note: JavaParsers started life as a direct copy of Parsers
@@ -868,11 +867,18 @@ self =>
           }
         }
       }
-      def mkNamed(args: List[Tree]) = if (isExpr) args map treeInfo.assignmentToMaybeNamedArg else args
+      def mkNamed(args: List[Tree]) = if (isExpr) args.map(treeInfo.assignmentToMaybeNamedArg) else args
+      var isMultiarg = false
       val arguments = right match {
-        case Parens(Nil)  => literalUnit :: Nil
-        case Parens(args) => mkNamed(args)
-        case _            => right :: Nil
+        case Parens(Nil)               => literalUnit :: Nil
+        case Parens(args @ (_ :: Nil)) => mkNamed(args)
+        case Parens(args)              => isMultiarg = true ; mkNamed(args)
+        case _                         => right :: Nil
+      }
+      def mkApply(fun: Tree, args: List[Tree]) = {
+        val apply = Apply(fun, args)
+        if (isMultiarg) apply.updateAttachment(MultiargInfixAttachment)
+        apply
       }
       if (isExpr) {
         if (rightAssoc) {
@@ -881,15 +887,12 @@ self =>
           val liftedArg = atPos(left.pos) {
             ValDef(Modifiers(FINAL | SYNTHETIC | ARTIFACT), x, TypeTree(), stripParens(left))
           }
-          Block(
-            liftedArg :: Nil,
-            Apply(mkSelection(right), List(Ident(x) setPos left.pos.focus)))
-        } else {
-          Apply(mkSelection(left), arguments)
-        }
-      } else {
-        Apply(Ident(op.encode), stripParens(left) :: arguments)
-      }
+          val apply = mkApply(mkSelection(right), List(Ident(x) setPos left.pos.focus))
+          Block(liftedArg :: Nil, apply)
+        } else
+          mkApply(mkSelection(left), arguments)
+      } else
+        mkApply(Ident(op.encode), stripParens(left) :: arguments)
     }
 
     /* --------- OPERAND/OPERATOR STACK --------------------------------------- */
@@ -2184,7 +2187,7 @@ self =>
     private def addMod(mods: Modifiers, mod: Long, pos: Position): Modifiers = {
       if (mods hasFlag mod) syntaxError(in.offset, "repeated modifier", skipIt = false)
       in.nextToken()
-      (mods | mod) withPosition (mod, pos)
+      (mods | mod).withPosition(mod, pos)
     }
 
     private def tokenRange(token: TokenData) =
@@ -2352,13 +2355,12 @@ self =>
           warning(in.offset, s"$ttl parameter sections are effectively implicit", WarningCategory.WFlagExtraImplicit)
       }
       val result = vds.toList
-      if (owner == nme.CONSTRUCTOR && (result.isEmpty || (result.head take 1 exists (_.mods.isImplicit)))) {
+      if (owner == nme.CONSTRUCTOR && (result.isEmpty || result.head.take(1).exists(_.mods.isImplicit)))
         in.token match {
           case LBRACKET   => syntaxError(in.offset, "no type parameters allowed here", skipIt = false)
           case EOF        => incompleteInputError("auxiliary constructor needs non-implicit parameter list")
           case _          => syntaxError(start, "auxiliary constructor needs non-implicit parameter list", skipIt = false)
         }
-      }
       addEvidenceParams(owner, result, contextBounds)
     }
 
@@ -2394,7 +2396,7 @@ self =>
         if (mods.isLazy) syntaxError("lazy modifier not allowed here. Use call-by-name parameters instead", skipIt = false)
         in.token match {
           case v @ (VAL | VAR) =>
-            mods = mods withPosition (in.token.toLong, tokenRange(in))
+            mods = mods.withPosition(in.token.toLong, tokenRange(in))
             if (v == VAR) mods |= Flags.MUTABLE
             in.nextToken()
           case _ =>
@@ -2629,13 +2631,13 @@ self =>
         syntaxError("lazy not allowed here. Only vals can be lazy", skipIt = false)
       in.token match {
         case VAL =>
-          patDefOrDcl(pos, mods withPosition(VAL, tokenRange(in)))
+          patDefOrDcl(pos, mods.withPosition(VAL, tokenRange(in)))
         case VAR =>
-          patDefOrDcl(pos, (mods | Flags.MUTABLE) withPosition (VAR, tokenRange(in)))
+          patDefOrDcl(pos, (mods | Flags.MUTABLE).withPosition(VAR, tokenRange(in)))
         case DEF =>
-          List(funDefOrDcl(pos, mods withPosition(DEF, tokenRange(in))))
+          List(funDefOrDcl(pos, mods.withPosition(DEF, tokenRange(in))))
         case TYPE =>
-          List(typeDefOrDcl(pos, mods withPosition(TYPE, tokenRange(in))))
+          List(typeDefOrDcl(pos, mods.withPosition(TYPE, tokenRange(in))))
         case _ =>
           List(tmplDef(pos, mods))
       }
@@ -2888,15 +2890,15 @@ self =>
       if (mods.isLazy) syntaxError("classes cannot be lazy", skipIt = false)
       in.token match {
         case TRAIT =>
-          classDef(pos, (mods | Flags.TRAIT | Flags.ABSTRACT) withPosition (Flags.TRAIT, tokenRange(in)))
+          classDef(pos, (mods | Flags.TRAIT | Flags.ABSTRACT).withPosition(Flags.TRAIT, tokenRange(in)))
         case CLASS =>
           classDef(pos, mods)
         case CASECLASS =>
-          classDef(pos, (mods | Flags.CASE) withPosition (Flags.CASE, tokenRange(in.prev /*scanner skips on 'case' to 'class', thus take prev*/)))
+          classDef(pos, (mods | Flags.CASE).withPosition(Flags.CASE, tokenRange(in.prev /*scanner skips on 'case' to 'class', thus take prev*/)))
         case OBJECT =>
           objectDef(pos, mods)
         case CASEOBJECT =>
-          objectDef(pos, (mods | Flags.CASE) withPosition (Flags.CASE, tokenRange(in.prev /*scanner skips on 'case' to 'object', thus take prev*/)))
+          objectDef(pos, (mods | Flags.CASE).withPosition(Flags.CASE, tokenRange(in.prev /*scanner skips on 'case' to 'object', thus take prev*/)))
         case _ =>
           syntaxErrorOrIncompleteAnd("expected start of definition", skipIt = true)(
             // assume a class definition so as to have somewhere to stash the annotations

src/compiler/scala/tools/nsc/settings/Warnings.scala

@@ -192,6 +192,7 @@ trait Warnings {
     val ByNameImplicit         = LintWarning("byname-implicit",           "Block adapted by implicit with by-name parameter.")
     val RecurseWithDefault     = LintWarning("recurse-with-default",      "Recursive call used default argument.")
     val UnitSpecialization     = LintWarning("unit-special",              "Warn for specialization of Unit in parameter position.")
+    val MultiargInfix          = LintWarning("multiarg-infix",            "Infix operator was defined or used with multiarg operand.")
 
     def allLintWarnings = values.toSeq.asInstanceOf[Seq[LintWarning]]
   }
@@ -223,6 +224,7 @@ trait Warnings {
   def warnByNameImplicit         = lint contains ByNameImplicit
   def warnRecurseWithDefault     = lint contains RecurseWithDefault
   def unitSpecialization         = lint contains UnitSpecialization
+  def multiargInfix              = lint contains MultiargInfix
 
   // The Xlint warning group.
   val lint = MultiChoiceSetting(

src/compiler/scala/tools/nsc/symtab/SymbolTrackers.scala

@@ -147,7 +147,7 @@ trait SymbolTrackers {
         else {
           indicatorString + indent + symString(root) + (
             if (children.isEmpty) ""
-            else children map (c => c.indentString(indent + "    ")) mkString ("\n", "\n", "")
+            else children.map(_.indentString(indent + "    ")).mkString("\n", "\n", "")
           )
         }
       }

src/compiler/scala/tools/nsc/transform/Constructors.scala

@@ -272,16 +272,10 @@ abstract class Constructors extends Statics with Transform with TypingTransforme
 
           closureClass setInfoAndEnter new ClassInfoType(closureParents, newScope, closureClass)
 
-          val outerField: TermSymbol = (
-            closureClass
-              newValue(nme.OUTER, impl.pos, PrivateLocal | PARAMACCESSOR)
-              setInfoAndEnter clazz.tpe
-          )
-          val applyMethod: MethodSymbol = (
-            closureClass
-              newMethod(nme.apply, impl.pos, FINAL)
-              setInfoAndEnter MethodType(Nil, ObjectTpe)
-          )
+          val outerField: TermSymbol =
+            closureClass.newValue(nme.OUTER, impl.pos, PrivateLocal | PARAMACCESSOR) setInfoAndEnter clazz.tpe
+          val applyMethod: MethodSymbol =
+            closureClass.newMethod(nme.apply, impl.pos, FINAL) setInfoAndEnter MethodType(Nil, ObjectTpe)
           val outerFieldDef     = ValDef(outerField)
           val closureClassTyper = localTyper.atOwner(closureClass)
           val applyMethodTyper  = closureClassTyper.atOwner(applyMethod)

src/compiler/scala/tools/nsc/transform/ExtensionMethods.scala

@@ -138,14 +138,14 @@ abstract class ExtensionMethods extends Transform with TypingTransformers {
       val resultType    = MethodType(List(thisParam), dropNullaryMethod(methodResult))
       val selfParamType = singleType(currentOwner.companionModule.thisType, thisParam)
 
-      def fixres(tp: Type)    = tp substThisAndSym (clazz, selfParamType, clazz.typeParams, tparamsFromClass)
-      def fixtparam(tp: Type) = tp substSym (clazz.typeParams, tparamsFromClass)
+      def fixres(tp: Type)    = tp.substThisAndSym(clazz, selfParamType, clazz.typeParams, tparamsFromClass)
+      def fixtparam(tp: Type) = tp.substSym(clazz.typeParams, tparamsFromClass)
 
       // We can't substitute symbols on the entire polytype because we
       // need to modify the bounds of the cloned type parameters, but we
       // don't want to substitute for the cloned type parameters themselves.
       val tparams = tparamsFromMethod ::: tparamsFromClass
-      tparams foreach (_ modifyInfo fixtparam)
+      tparams.foreach(_ modifyInfo fixtparam)
       GenPolyType(tparams, fixres(resultType))
 
       // For reference, calling fix on the GenPolyType plays out like this:

src/compiler/scala/tools/nsc/transform/SpecializeTypes.scala

@@ -804,7 +804,7 @@ abstract class SpecializeTypes extends InfoTransform with TypingTransformers {
           def overrideIn(clazz: Symbol, sym: Symbol) = {
             val newFlags = (sym.flags | OVERRIDE | SPECIALIZED) & ~(DEFERRED | CASEACCESSOR | PARAMACCESSOR)
             val sym1     = sym.cloneSymbol(clazz, newFlags)
-            sym1 modifyInfo (_ asSeenFrom (clazz.tpe, sym1.owner))
+            sym1.modifyInfo(_.asSeenFrom(clazz.tpe, sym1.owner))
           }
           val specVal = specializedOverload(sClass, m, env)
 

src/compiler/scala/tools/nsc/transform/TailCalls.scala

@@ -174,7 +174,7 @@ abstract class TailCalls extends Transform {
         val thisParam = method.newSyntheticValueParam(currentClass.typeOfThis)
         label setInfo MethodType(thisParam :: method.tpe.params, method.tpe_*.finalResultType)
         if (isEligible)
-          label substInfo (method.tpe.typeParams, tparams)
+          label.substInfo(method.tpe.typeParams, tparams)
 
         label
       }

src/compiler/scala/tools/nsc/transform/patmat/Logic.scala

@@ -517,7 +517,7 @@ trait ScalaLogic extends Interface with Logic with TreeAndTypeAnalysis {
 
       def resetUniques() = {_nextId = 0; uniques.clear()}
       private val uniques = new mutable.HashMap[Tree, Var]
-      def apply(x: Tree): Var = uniques getOrElseUpdate(x, new Var(x, x.tpe))
+      def apply(x: Tree): Var = uniques.getOrElseUpdate(x, new Var(x, x.tpe))
       def unapply(v: Var) = Some(v.path)
     }
     class Var(val path: Tree, staticTp: Type) extends AbsVar {
@@ -575,11 +575,11 @@ trait ScalaLogic extends Interface with Logic with TreeAndTypeAnalysis {
 
       // populate equalitySyms
       // don't care about the result, but want only one fresh symbol per distinct constant c
-      def registerEquality(c: Const): Unit = {ensureCanModify(); symForEqualsTo getOrElseUpdate(c, Sym(this, c))}
+      def registerEquality(c: Const): Unit = { ensureCanModify() ; symForEqualsTo.getOrElseUpdate(c, Sym(this, c)) }
 
       // return the symbol that represents this variable being equal to the constant `c`, if it exists, otherwise False (for robustness)
       // (registerEquality(c) must have been called prior, either when constructing the domain or from outside)
-      def propForEqualsTo(c: Const): Prop = {observed(); symForEqualsTo.getOrElse(c, False)}
+      def propForEqualsTo(c: Const): Prop = { observed() ; symForEqualsTo.getOrElse(c, False) }
 
       // [implementation NOTE: don't access until all potential equalities have been registered using registerEquality]p
       /** the information needed to construct the boolean proposition that encodes the equality proposition (V = C)
@@ -709,8 +709,8 @@ trait ScalaLogic extends Interface with Logic with TreeAndTypeAnalysis {
       // don't call until all equalities have been registered and registerNull has been called (if needed)
       def describe = {
         def domain_s = domain match {
-          case Some(d) => d mkString (" ::= ", " | ", "// "+ symForEqualsTo.keys)
-          case _       => symForEqualsTo.keys mkString (" ::= ", " | ", " | ...")
+          case Some(d) => d.mkString(" ::= ", " | ", "// "+ symForEqualsTo.keys)
+          case _       => symForEqualsTo.keys.mkString(" ::= ", " | ", " | ...")
         }
         s"$this: ${staticTp}${domain_s} // = $path"
       }

src/compiler/scala/tools/nsc/transform/patmat/MatchAnalysis.scala

@@ -234,14 +234,14 @@ trait MatchApproximation extends TreeAndTypeAnalysis with ScalaLogic with MatchT
       private[this] val uniqueTypeProps     = new mutable.HashMap[(Tree, Type), Eq]
 
       def uniqueEqualityProp(testedPath: Tree, rhs: Tree): Prop =
-        uniqueEqualityProps getOrElseUpdate((testedPath, rhs), Eq(Var(testedPath), ValueConst(rhs)))
+        uniqueEqualityProps.getOrElseUpdate((testedPath, rhs), Eq(Var(testedPath), ValueConst(rhs)))
 
       // overridden in TreeMakersToPropsIgnoreNullChecks
       def uniqueNonNullProp (testedPath: Tree): Prop =
-        uniqueNonNullProps getOrElseUpdate(testedPath, Not(Eq(Var(testedPath), NullConst)))
+        uniqueNonNullProps.getOrElseUpdate(testedPath, Not(Eq(Var(testedPath), NullConst)))
 
       def uniqueTypeProp(testedPath: Tree, pt: Type): Prop =
-        uniqueTypeProps getOrElseUpdate((testedPath, pt), Eq(Var(testedPath), TypeConst(checkableType(pt))))
+        uniqueTypeProps.getOrElseUpdate((testedPath, pt), Eq(Var(testedPath), TypeConst(checkableType(pt))))
 
       // a variable in this set should never be replaced by a tree that "does not consist of a selection on a variable in this set" (intuitively)
       private val pointsToBound = mutable.HashSet(root)
@@ -646,7 +646,7 @@ trait MatchAnalysis extends MatchApproximation {
 
     def varAssignmentString(varAssignment: Map[Var, (Seq[Const], Seq[Const])]) =
       varAssignment.toSeq.sortBy(_._1.toString).map { case (v, (trues, falses)) =>
-         val assignment = "== "+ (trues mkString("(", ", ", ")")) +"  != ("+ (falses mkString(", ")) +")"
+         val assignment = "== "+ trues.mkString("(", ", ", ")") +"  != ("+ falses.mkString(", ") +")"
          v +"(="+ v.path +": "+ v.staticTpCheckable +") "+ assignment
        }.mkString("\n")
 

src/compiler/scala/tools/nsc/transform/patmat/PatternMatching.scala

@@ -294,7 +294,7 @@ trait Interface extends ast.TreeDSL {
         }
         new Substitution(newFrom.prependToList(other.from), newTo.prependToList(other.to.mapConserve(apply)))
       }
-      override def toString = (from.map(_.name) zip to) mkString("Substitution(", ", ", ")")
+      override def toString = from.map(_.name).zip(to).mkString("Substitution(", ", ", ")")
     }
 
     object EmptySubstitution extends Substitution(Nil, Nil) {

src/compiler/scala/tools/nsc/typechecker/NamesDefaults.scala

@@ -188,7 +188,7 @@ trait NamesDefaults { self: Analyzer =>
         blockTyper.context.scope enter sym
         val vd = atPos(sym.pos)(ValDef(sym, qual) setType NoType)
         // it stays in Vegas: scala/bug#5720, scala/bug#5727
-        qual changeOwner (blockTyper.context.owner, sym)
+        qual.changeOwner(blockTyper.context.owner, sym)
 
         val newQual = atPos(qual.pos.focus)(blockTyper.typedQualifier(Ident(sym.name)))
         val baseFunTransformed = atPos(baseFun.pos.makeTransparent) {