Drop explicit BYNAME pickles

Instead, drop <by-name> applications when pickling and reconstitute them
based on formal parameter types when unpickling.

Author: odersky

compiler/src/dotty/tools/dotc/core/tasty/TreePickler.scala

@@ -418,8 +418,9 @@ class TreePickler(pickler: TastyPickler) {
             writeByte(THROW)
             pickleTree(args.head)
           else if fun.symbol eq defn.byNameMethod then
-            writeByte(BYNAME)
             pickleTree(args.head)
+              // <by-name>(...) applications are re-constituted when unpickling
+              // based on formal parameter types.
           else
             writeByte(APPLY)
             withLength {

compiler/src/dotty/tools/dotc/core/tasty/TreeUnpickler.scala

@@ -1123,8 +1123,6 @@ class TreeUnpickler(reader: TastyReader,
           New(readTpt())
         case THROW =>
           Throw(readTerm())
-        case BYNAME =>
-          ByName(readTerm())
         case SINGLETONtpt =>
           SingletonTypeTree(readTerm())
         case BYNAMEtpt =>
@@ -1145,7 +1143,12 @@ class TreeUnpickler(reader: TastyReader,
               tpd.Super(qual, mixId, mixTpe.typeSymbol)
             case APPLY =>
               val fn = readTerm()
-              tpd.Apply(fn, until(end)(readTerm()))
+              var args = until(end)(readTerm())
+              fn.tpe.widen match
+                case mt: MethodType =>
+                  args = args.zipWithConserve(mt.paramInfos)(_.alignByName(_))
+                case _ =>
+              tpd.Apply(fn, args)
             case TYPEAPPLY =>
               tpd.TypeApply(readTerm(), until(end)(readTpt()))
             case TYPED =>

tasty/src/dotty/tools/tasty/TastyFormat.scala

@@ -89,7 +89,6 @@ Standard-Section: "ASTs" TopLevelStat*
                   QUALTHIS              typeIdent_Tree                             -- id.this, different from THIS in that it contains a qualifier ident with position.
                   NEW                   clsType_Term                               -- new cls
                   THROW                 throwableExpr_Term                         -- throw throwableExpr
-                  BYNAME                expr_Term                                  -- by-name argument
                   NAMEDARG              paramName_NameRef arg_Term                 -- paramName = arg
                   APPLY          Length fn_Term arg_Term*                          -- fn(args)
                   TYPEAPPLY      Length fn_Term arg_Type*                          -- fn[args]
@@ -512,7 +511,6 @@ object TastyFormat {
   final val RECtype = 100
   final val SINGLETONtpt = 101
   final val BOUNDED = 102
-  final val BYNAME = 103
 
   // Cat. 4:    tag Nat AST
 
@@ -790,7 +788,6 @@ object TastyFormat {
     case TYPEBOUNDStpt => "TYPEBOUNDStpt"
     case ANDtype => "ANDtype"
     case ORtype => "ORtype"
-    case BYNAME => "BYNAME"
     case BYNAMEtype => "BYNAMEtype"
     case BYNAMEtpt => "BYNAMEtpt"
     case POLYtype => "POLYtype"