Allow Named Arguments in TypeArgs

Lets one also pass named arguments to methods.

3 files changed, 50 insertions, 11 deletions

diff --git a/src/dotty/tools/dotc/typer/Applications.scala b/src/dotty/tools/dotc/typer/Applications.scala
index c7acd3c1f..098385d4b 100644
--- a/src/dotty/tools/dotc/typer/Applications.scala
+++ b/src/dotty/tools/dotc/typer/Applications.scala
@@ -603,12 +603,19 @@ trait Applications extends Compatibility { self: Typer =>
   protected def handleUnexpectedFunType(tree: untpd.Apply, fun: Tree)(implicit ctx: Context): Tree =
     throw new Error(s"unexpected type.\n fun = $fun,\n methPart(fun) = ${methPart(fun)},\n methPart(fun).tpe = ${methPart(fun).tpe},\n tpe = ${fun.tpe}")
 
+  def typedNamedArgs(args: List[untpd.Tree])(implicit ctx: Context) =
+    for (arg @ NamedArg(id, argtpt) <- args) yield {
+      val argtpt1 = typedType(argtpt)
+      cpy.NamedArg(arg)(id, argtpt1).withType(argtpt1.tpe)
+    }
+
   def typedTypeApply(tree: untpd.TypeApply, pt: Type)(implicit ctx: Context): Tree = track("typedTypeApply") {
-    var typedArgs = tree.args mapconserve (typedType(_))
+    val isNamed = hasNamedArg(tree.args)
+    var typedArgs = if (isNamed) typedNamedArgs(tree.args) else tree.args.mapconserve(typedType(_))
     val typedFn = typedExpr(tree.fun, PolyProto(typedArgs.tpes, pt))
     typedFn.tpe.widen match {
       case pt: PolyType =>
-        if (typedArgs.length <= pt.paramBounds.length)
+        if (typedArgs.length <= pt.paramBounds.length && !isNamed)
           typedArgs = typedArgs.zipWithConserve(pt.paramBounds)(adaptTypeArg)
       case _ =>
     }
diff --git a/src/dotty/tools/dotc/typer/TypeAssigner.scala b/src/dotty/tools/dotc/typer/TypeAssigner.scala
index 9ee67684d..1c66414a1 100644
--- a/src/dotty/tools/dotc/typer/TypeAssigner.scala
+++ b/src/dotty/tools/dotc/typer/TypeAssigner.scala
@@ -8,7 +8,8 @@ import Scopes._, Contexts._, Constants._, Types._, Symbols._, Names._, Flags._,
 import ErrorReporting._, Annotations._, Denotations._, SymDenotations._, StdNames._, TypeErasure._
 import util.Positions._
 import config.Printers._
-import NameOps._
+import ast.Trees._
+import collection.mutable
 
 trait TypeAssigner {
   import tpd._
@@ -310,9 +311,44 @@ trait TypeAssigner {
   def assignType(tree: untpd.TypeApply, fn: Tree, args: List[Tree])(implicit ctx: Context) = {
     val ownType = fn.tpe.widen match {
       case pt: PolyType =>
-        val argTypes = args.tpes
-        if (sameLength(argTypes, pt.paramNames)|| ctx.phase.prev.relaxedTyping) pt.instantiate(argTypes)
-        else errorType(d"wrong number of type parameters for ${fn.tpe}; expected: ${pt.paramNames.length}", tree.pos)
+        val paramNames = pt.paramNames
+        if (hasNamedArg(args)) {
+          val argMap = new mutable.HashMap[Name, Type]
+          for (NamedArg(name, arg) <- args)
+            if (argMap.contains(name))
+              ctx.error("duplicate name", arg.pos)
+            else if (!paramNames.contains(name))
+              ctx.error(s"undefined parameter name, required: ${paramNames.mkString(" or ")}", arg.pos)
+            else
+              argMap(name) = arg.tpe
+          val gapBuf = new mutable.ListBuffer[Int]
+          def nextPoly = {
+            val idx = gapBuf.length
+            gapBuf += idx
+            PolyParam(pt, idx)
+          }
+          val normArgs = paramNames.map(pname => argMap.getOrElse(pname, nextPoly))
+          val transform = new TypeMap {
+            def apply(t: Type) = t match {
+              case PolyParam(`pt`, idx) => normArgs(idx)
+              case _ => mapOver(t)
+            }
+          }
+          val resultType1 = transform(pt.resultType)
+          if (gapBuf.isEmpty) resultType1
+          else {
+            val gaps = gapBuf.toList
+            pt.derivedPolyType(
+              gaps.map(paramNames.filterNot(argMap.contains)),
+              gaps.map(idx => transform(pt.paramBounds(idx)).bounds),
+              resultType1)
+          }
+        }
+        else {
+          val argTypes = args.tpes
+          if (sameLength(argTypes, paramNames)|| ctx.phase.prev.relaxedTyping) pt.instantiate(argTypes)
+          else errorType(d"wrong number of type parameters for ${fn.tpe}; expected: ${pt.paramNames.length}", tree.pos)
+        }
       case _ =>
         errorType(i"${err.exprStr(fn)} does not take type parameters", tree.pos)
     }
diff --git a/src/dotty/tools/dotc/typer/Typer.scala b/src/dotty/tools/dotc/typer/Typer.scala
index 0ff2241fb..fc2bf2381 100644
--- a/src/dotty/tools/dotc/typer/Typer.scala
+++ b/src/dotty/tools/dotc/typer/Typer.scala
@@ -893,11 +893,7 @@ class Typer extends Namer with TypeAssigner with Applications with Implicits wit
     else {
       var args = tree.args
       val args1 =
-        if (hasNamedArg(args))
-          for (arg @ NamedArg(id, argtpt) <- args) yield {
-            val argtpt1 = typedType(argtpt)
-            cpy.NamedArg(arg)(id, argtpt1).withType(argtpt1.tpe)
-          }
+        if (hasNamedArg(args)) typedNamedArgs(args)
         else {
           if (args.length != tparams.length) {
             ctx.error(d"wrong number of type arguments for ${tpt1.tpe}, should be ${tparams.length}", tree.pos)