Fix #4466: Update contexts of FunProto when something else is tried

compiler/src/dotty/tools/dotc/ast/tpd.scala

@@ -981,7 +981,7 @@ object tpd extends Trees.Instance[Type] with TypedTreeInfo {
 
   def applyOverloaded(receiver: Tree, method: TermName, args: List[Tree], targs: List[Type], expectedType: Type, isAnnotConstructor: Boolean = false)(implicit ctx: Context): Tree = {
     val typer = ctx.typer
-    val proto = new FunProtoTyped(args, expectedType, typer)
+    val proto = new FunProtoTyped(args, expectedType)(typer)
     val denot = receiver.tpe.member(method)
     assert(denot.exists, i"no member $receiver . $method, members = ${receiver.tpe.decls}")
     val selected =

compiler/src/dotty/tools/dotc/printing/RefinedPrinter.scala

@@ -208,7 +208,7 @@ class RefinedPrinter(_ctx: Context) extends PlainPrinter(_ctx) {
            ": " ~ toText(tp.memberProto) ~ " }"
       case tp: ViewProto =>
         return toText(tp.argType) ~ " ?=>? " ~ toText(tp.resultType)
-      case tp @ FunProto(args, resultType, _) =>
+      case tp @ FunProto(args, resultType) =>
         val argsText = args match {
           case dummyTreeOfType(tp) :: Nil if !(tp isRef defn.NullClass) => "null: " ~ toText(tp)
           case _ => toTextGlobal(args, ", ")

compiler/src/dotty/tools/dotc/transform/Erasure.scala

@@ -500,7 +500,7 @@ object Erasure {
       val Apply(fun, args) = tree
       if (fun.symbol == defn.cbnArg)
         typedUnadapted(args.head, pt)
-      else typedExpr(fun, FunProto(args, pt, this)) match {
+      else typedExpr(fun, FunProto(args, pt)(this)) match {
         case fun1: Apply => // arguments passed in prototype were already passed
           fun1
         case fun1 =>

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

@@ -690,7 +690,7 @@ trait Applications extends Compatibility { self: Typer with Dynamic =>
   def typedApply(tree: untpd.Apply, pt: Type)(implicit ctx: Context): Tree = {
 
     def realApply(implicit ctx: Context): Tree = track("realApply") {
-      val originalProto = new FunProto(tree.args, IgnoredProto(pt), this)(argCtx(tree))
+      val originalProto = new FunProto(tree.args, IgnoredProto(pt))(this)(argCtx(tree))
       val fun1 = typedExpr(tree.fun, originalProto)
 
       // Warning: The following lines are dirty and fragile. We record that auto-tupling was demanded as
@@ -1365,7 +1365,7 @@ trait Applications extends Compatibility { self: Typer with Dynamic =>
       alts filter (isApplicable(_, argTypes, resultType))
 
     val candidates = pt match {
-      case pt @ FunProto(args, resultType, _) =>
+      case pt @ FunProto(args, resultType) =>
         val numArgs = args.length
         val normArgs = args.mapConserve {
           case Block(Nil, expr) => expr

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

@@ -897,7 +897,7 @@ trait Implicits { self: Typer =>
 
     lazy val funProto = fullProto match {
       case proto: ViewProto =>
-        FunProto(untpd.TypedSplice(dummyTreeOfType(proto.argType)) :: Nil, proto.resultType, self)
+        FunProto(untpd.TypedSplice(dummyTreeOfType(proto.argType)) :: Nil, proto.resultType)(self)
       case proto => proto
     }
 

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

@@ -210,28 +210,38 @@ object ProtoTypes {
 
   trait ApplyingProto extends ProtoType
 
+  class FunProtoState {
+
+    /** The list of typed arguments, if all arguments are typed */
+    var typedArgs: List[Tree] = Nil
+
+    /** A map in which typed arguments can be stored to be later integrated in `typedArgs`. */
+    var typedArg: SimpleIdentityMap[untpd.Tree, Tree] = SimpleIdentityMap.Empty
+
+    /** A map recording the typer states and constraints in which arguments stored in myTypedArg were typed */
+    var evalState: SimpleIdentityMap[untpd.Tree, (TyperState, Constraint)] = SimpleIdentityMap.Empty
+
+    /** The tupled version of this prototype, if it has been computed */
+    var tupled: Type = NoType
+
+    /** If true, the application of this prototype was canceled. */
+    var toDrop: Boolean = false
+  }
+
   /** A prototype for expressions that appear in function position
    *
    *  [](args): resultType
    */
-  case class FunProto(args: List[untpd.Tree], resType: Type, typer: Typer)(implicit ctx: Context)
+  case class FunProto(args: List[untpd.Tree], resType: Type)(typer: Typer, state: FunProtoState = new FunProtoState)(implicit ctx: Context)
   extends UncachedGroundType with ApplyingProto {
-    private var myTypedArgs: List[Tree] = Nil
-
     override def resultType(implicit ctx: Context) = resType
 
-    /** A map in which typed arguments can be stored to be later integrated in `typedArgs`. */
-    private var myTypedArg: SimpleIdentityMap[untpd.Tree, Tree] = SimpleIdentityMap.Empty
-
-    /** A map recording the typer states and constraints in which arguments stored in myTypedArg were typed */
-    private var evalState: SimpleIdentityMap[untpd.Tree, (TyperState, Constraint)] = SimpleIdentityMap.Empty
-
     def isMatchedBy(tp: Type)(implicit ctx: Context) =
       typer.isApplicable(tp, Nil, unforcedTypedArgs, resultType)
 
     def derivedFunProto(args: List[untpd.Tree] = this.args, resultType: Type, typer: Typer = this.typer) =
       if ((args eq this.args) && (resultType eq this.resultType) && (typer eq this.typer)) this
-      else new FunProto(args, resultType, typer)
+      else new FunProto(args, resultType)(typer)
 
     override def notApplied = WildcardType
 
@@ -244,19 +254,19 @@ object ProtoTypes {
      *  @return True if all arguments have types (in particular, no types were forgotten).
      */
     def allArgTypesAreCurrent()(implicit ctx: Context): Boolean = {
-      evalState foreachBinding { (arg, tstateConstr) =>
+      state.evalState foreachBinding { (arg, tstateConstr) =>
         if ((tstateConstr._1.uncommittedAncestor.constraint `ne` ctx.typerState.constraint) ||
             tstateConstr._2.isRetracted) {
-          typr.println(i"need to invalidate $arg / ${myTypedArg(arg)}, ${tstateConstr._2}, current = ${ctx.typerState.constraint}")
-          myTypedArg = myTypedArg.remove(arg)
-          evalState = evalState.remove(arg)
+          typr.println(i"need to invalidate $arg / ${state.typedArg(arg)}, ${tstateConstr._2}, current = ${ctx.typerState.constraint}")
+          state.typedArg = state.typedArg.remove(arg)
+          state.evalState = state.evalState.remove(arg)
         }
       }
-      myTypedArg.size == args.length
+      state.typedArg.size == args.length
     }
 
     private def cacheTypedArg(arg: untpd.Tree, typerFn: untpd.Tree => Tree, force: Boolean)(implicit ctx: Context): Tree = {
-      var targ = myTypedArg(arg)
+      var targ = state.typedArg(arg)
       if (targ == null) {
         if (!force && untpd.functionWithUnknownParamType(arg).isDefined)
           // If force = false, assume ? rather than reporting an error.
@@ -270,8 +280,8 @@ object ProtoTypes {
             // typerstate if there are no errors. If we also omitted the next two lines
             // when warning were emitted, `pos/t1756.scala` would fail when run with -feature.
             // It would produce an orphan type parameter for CI when pickling.
-            myTypedArg = myTypedArg.updated(arg, targ)
-            evalState = evalState.updated(arg, (ctx.typerState, ctx.typerState.constraint))
+            state.typedArg = state.typedArg.updated(arg, targ)
+            state.evalState = state.evalState.updated(arg, (ctx.typerState, ctx.typerState.constraint))
           }
         }
       }
@@ -285,9 +295,9 @@ object ProtoTypes {
      *                  "missing parameter type" error
      */
     private def typedArgs(force: Boolean): List[Tree] = {
-      if (myTypedArgs.size != args.length)
-        myTypedArgs = args.mapconserve(cacheTypedArg(_, typer.typed(_), force))
-      myTypedArgs
+      if (state.typedArgs.size != args.length)
+        state.typedArgs = args.mapconserve(cacheTypedArg(_, typer.typed(_), force))
+      state.typedArgs
     }
 
     def typedArgs: List[Tree] = typedArgs(force = true)
@@ -306,24 +316,19 @@ object ProtoTypes {
      *  @pre `arg` has been typed before
      */
     def typeOfArg(arg: untpd.Tree)(implicit ctx: Context): Type =
-      myTypedArg(arg).tpe
-
-    private var myTupled: Type = NoType
+      state.typedArg(arg).tpe
 
     /** The same proto-type but with all arguments combined in a single tuple */
-    def tupled: FunProto = myTupled match {
+    def tupled: FunProto = state.tupled match {
       case pt: FunProto =>
         pt
       case _ =>
-        myTupled = new FunProto(untpd.Tuple(args) :: Nil, resultType, typer)
+        state.tupled = new FunProto(untpd.Tuple(args) :: Nil, resultType)(typer)
         tupled
     }
 
     /** Somebody called the `tupled` method of this prototype */
-    def isTupled: Boolean = myTupled.isInstanceOf[FunProto]
-
-    /** If true, the application of this prototype was canceled. */
-    private var toDrop: Boolean = false
+    def isTupled: Boolean = state.tupled.isInstanceOf[FunProto]
 
     /** Cancel the application of this prototype. This can happen for a nullary
      *  application `f()` if `f` refers to a symbol that exists both in parameterless
@@ -333,10 +338,10 @@ object ProtoTypes {
      */
     def markAsDropped() = {
       assert(args.isEmpty)
-      toDrop = true
+      state.toDrop = true
     }
 
-    def isDropped: Boolean = toDrop
+    def isDropped: Boolean = state.toDrop
 
     override def toString = s"FunProto(${args mkString ","} => $resultType)"
 
@@ -350,23 +355,15 @@ object ProtoTypes {
 
     override def withContext(newCtx: Context) =
       if (newCtx `eq` ctx) this
-      else {
-        val result = new FunProto(args, resType, typer)(newCtx)
-        result.myTypedArgs = myTypedArgs
-        result.myTypedArg = myTypedArg
-        result.evalState = evalState
-        result.myTupled = myTupled
-        result.toDrop = toDrop
-        result
-      }
+      else new FunProto(args, resType)(typer, state)(newCtx)
   }
 
 
   /** A prototype for expressions that appear in function position
    *
    *  [](args): resultType, where args are known to be typed
    */
-  class FunProtoTyped(args: List[tpd.Tree], resultType: Type, typer: Typer)(implicit ctx: Context) extends FunProto(args, resultType, typer)(ctx) {
+  class FunProtoTyped(args: List[tpd.Tree], resultType: Type)(typer: Typer)(implicit ctx: Context) extends FunProto(args, resultType)(typer)(ctx) {
     override def typedArgs = args
     override def withContext(ctx: Context) = this
   }
@@ -405,7 +402,7 @@ object ProtoTypes {
   }
 
   class UnapplyFunProto(argType: Type, typer: Typer)(implicit ctx: Context) extends FunProto(
-    untpd.TypedSplice(dummyTreeOfType(argType))(ctx) :: Nil, WildcardType, typer)
+    untpd.TypedSplice(dummyTreeOfType(argType))(ctx) :: Nil, WildcardType)(typer)
 
   /** A prototype for expressions [] that are type-parameterized:
    *

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

@@ -870,7 +870,7 @@ class Typer extends Namer
               expr1.tpe
             case _ =>
               val protoArgs = args map (_ withType WildcardType)
-              val callProto = FunProto(protoArgs, WildcardType, this)
+              val callProto = FunProto(protoArgs, WildcardType)(this)
               val expr1 = typedExpr(expr, callProto)
               fnBody = cpy.Apply(fnBody)(untpd.TypedSplice(expr1), args)
               expr1.tpe
@@ -2054,7 +2054,7 @@ class Typer extends Namer
       tryInsertImplicitOnQualifier(tree, pt.withContext(ctx), locked).getOrElse(fallBack)
 
     pt match {
-      case pt @ FunProto(Nil, _, _)
+      case pt @ FunProto(Nil, _)
       if tree.symbol.allOverriddenSymbols.exists(_.info.isNullaryMethod) &&
          tree.getAttachment(DroppedEmptyArgs).isEmpty =>
         tree.putAttachment(DroppedEmptyArgs, ())