Fix "wrong number of args" reporting

"Wrong number of args" only works for type arguments but was called also for
term arguments. Ideally we should have a WrongNumberOfArgs message that works for
both, but this will take some refactoring.

Author: odersky

compiler/src/dotty/tools/dotc/reporting/diagnostic/messages.scala

@@ -224,6 +224,8 @@ object messages {
   extends Message(8) {
     val kind = "Member Not Found"
 
+    //println(i"site = $site, decls = ${site.decls}, source = ${site.widen.typeSymbol.sourceFile}") //DEBUG
+
     val msg = {
       import core.Flags._
       val maxDist = 3
@@ -606,7 +608,7 @@ object messages {
            |"""
   }
 
-  case class WrongNumberOfArgs(fntpe: Type, argKind: String, expectedArgs: List[TypeParamInfo], actual: List[untpd.Tree])(implicit ctx: Context)
+  case class WrongNumberOfTypeArgs(fntpe: Type, expectedArgs: List[TypeParamInfo], actual: List[untpd.Tree])(implicit ctx: Context)
   extends Message(22) {
     val kind = "Syntax"
 
@@ -628,7 +630,7 @@ object messages {
     }
 
     val msg =
-      hl"""|${NoColor(msgPrefix)} ${argKind} arguments for $prettyName$expectedArgString
+      hl"""|${NoColor(msgPrefix)} type arguments for $prettyName$expectedArgString
            |expected: $expectedArgString
            |actual:   $actualArgString""".stripMargin
 

compiler/src/dotty/tools/dotc/typer/ErrorReporting.scala

@@ -49,8 +49,8 @@ object ErrorReporting {
     errorMsg(ex.show, ctx)
   }
 
-  def wrongNumberOfArgs(fntpe: Type, kind: String, expectedArgs: List[TypeParamInfo], actual: List[untpd.Tree], pos: Position)(implicit ctx: Context) =
-    errorType(WrongNumberOfArgs(fntpe, kind, expectedArgs, actual)(ctx), pos)
+  def wrongNumberOfTypeArgs(fntpe: Type, expectedArgs: List[TypeParamInfo], actual: List[untpd.Tree], pos: Position)(implicit ctx: Context) =
+    errorType(WrongNumberOfTypeArgs(fntpe, expectedArgs, actual)(ctx), pos)
 
   class Errors(implicit ctx: Context) {
 

compiler/src/dotty/tools/dotc/typer/TypeAssigner.scala

@@ -314,7 +314,8 @@ trait TypeAssigner {
     val ownType = fn.tpe.widen match {
       case fntpe @ MethodType(_, ptypes) =>
         if (sameLength(ptypes, args) || ctx.phase.prev.relaxedTyping) fntpe.instantiate(args.tpes)
-        else wrongNumberOfArgs(fn.tpe, "", fntpe.typeParams, args, tree.pos)
+        else
+          errorType(i"wrong number of arguments for $fntpe: ${fn.tpe}, expected: ${ptypes.length}, found: ${args.length}", tree.pos)
       case t =>
         errorType(i"${err.exprStr(fn)} does not take parameters", tree.pos)
     }
@@ -369,7 +370,7 @@ trait TypeAssigner {
         else {
           val argTypes = args.tpes
           if (sameLength(argTypes, paramNames) || ctx.phase.prev.relaxedTyping) pt.instantiate(argTypes)
-          else wrongNumberOfArgs(fn.tpe, "type", pt.typeParams, args, tree.pos)
+          else wrongNumberOfTypeArgs(fn.tpe, pt.typeParams, args, tree.pos)
         }
       case _ =>
         errorType(i"${err.exprStr(fn)} does not take type parameters", tree.pos)
@@ -462,7 +463,7 @@ trait TypeAssigner {
     val ownType =
       if (hasNamedArg(args)) (tycon.tpe /: args)(refineNamed)
       else if (sameLength(tparams, args)) tycon.tpe.appliedTo(args.tpes)
-      else wrongNumberOfArgs(tycon.tpe, "type", tparams, args, tree.pos)
+      else wrongNumberOfTypeArgs(tycon.tpe, tparams, args, tree.pos)
     tree.withType(ownType)
   }
 

compiler/src/dotty/tools/dotc/typer/Typer.scala

@@ -1056,7 +1056,7 @@ class Typer extends Namer with TypeAssigner with Applications with Implicits wit
         if (hasNamedArg(args)) typedNamedArgs(args)
         else {
           if (args.length != tparams.length) {
-            wrongNumberOfArgs(tpt1.tpe, "type", tparams, args, tree.pos)
+            wrongNumberOfTypeArgs(tpt1.tpe, tparams, args, tree.pos)
             args = args.take(tparams.length)
           }
           def typedArg(arg: untpd.Tree, tparam: TypeParamInfo) = {