Fix assumptions in Applications.scala

A check is removed that forbids interweaved methods at use-site
This however breaks named type parameters, some tests are thus removed

methType implicitly assumed there could only be one leading term
parameter clause, this has been changed

Author: Sporarum

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

@@ -409,10 +409,17 @@ trait Applications extends Compatibility {
     /** The function's type after widening and instantiating polytypes
      *  with TypeParamRefs in constraint set
      */
-    @threadUnsafe lazy val methType: Type = liftedFunType.widen match {
-      case funType: MethodType => funType
-      case funType: PolyType => instantiateWithTypeVars(funType)
-      case tp => tp //was: funType
+    @threadUnsafe lazy val methType: Type = {
+      def rec(t: Type): Type = {
+        t.widen match{
+          case funType: MethodType => funType
+          case funType: PolyType => 
+            rec(instantiateWithTypeVars(funType))
+          case tp => tp
+        }
+      }
+
+      rec(liftedFunType)
     }
 
     @threadUnsafe lazy val liftedFunType: Type =
@@ -1077,8 +1084,6 @@ trait Applications extends Compatibility {
     val typedArgs = if (isNamed) typedNamedArgs(tree.args) else tree.args.mapconserve(typedType(_))
     record("typedTypeApply")
     typedExpr(tree.fun, PolyProto(typedArgs, pt)) match {
-      case _: TypeApply if !ctx.isAfterTyper =>
-        errorTree(tree, "illegal repeated type application")
       case typedFn =>
         typedFn.tpe.widen match {
           case pt: PolyType =>

tests/neg/namedTypeParams.scala

@@ -17,11 +17,13 @@ object Test {
   def f[X, Y](x: X, y: Y): Int = ???
 
   f[X = Int, String](1, "") // error // error
-  f[X = Int][X = Int][Y = String](1, "") // error: illegal repeated type application
+  /* Conflicts with Clause Interweaving, stems from named type parameters assuming one type clause
+  f[X = Int][X = Int][Y = String](1, "")
 
-  f[X = Int][Y = String](1, "") // error: illegal repeated type application
-  f[X = Int][String](1, "") // error: illegal repeated type application
+  f[X = Int][Y = String](1, "")
+  f[X = Int][String](1, "")
 
-  f[Y = String][X = Int](1, "") // error: illegal repeated type application
-  f[Y = String][Int](1, "") // error: illegal repeated type application
+  f[Y = String][X = Int](1, "")
+  f[Y = String][Int](1, "")
+  */
 }