Merge pull request #8406 from dotty-staging/fix-#7793

Fix #7793: Handle context parameters in resolveOverloaded

Author: anatoliykmetyuk

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

@@ -574,7 +574,7 @@ object desugar {
       val nu = vparamss.foldLeft(makeNew(classTypeRef)) { (nu, vparams) =>
         val app = Apply(nu, vparams.map(refOfDef))
         vparams match {
-          case vparam :: _ if vparam.mods.is(Given) => app.setGivenApply()
+          case vparam :: _ if vparam.mods.is(Given) => app.setUsingApply()
           case _ => app
         }
       }

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

@@ -439,8 +439,8 @@ object Trees {
     extends GenericApply[T] {
     type ThisTree[-T >: Untyped] = Apply[T]
 
-    def isGivenApply = hasAttachment(untpd.ApplyGiven)
-    def setGivenApply() = { putAttachment(untpd.ApplyGiven, ()); this }
+    def isUsingApply = hasAttachment(untpd.ApplyGiven)
+    def setUsingApply() = { putAttachment(untpd.ApplyGiven, ()); this }
   }
 
   /** fun[args] */

compiler/src/dotty/tools/dotc/core/Types.scala

@@ -3305,7 +3305,6 @@ object Types {
       companion.eq(ContextualMethodType) ||
       companion.eq(ErasedContextualMethodType)
 
-
     def computeSignature(implicit ctx: Context): Signature = {
       val params = if (isErasedMethod) Nil else paramInfos
       resultSignature.prependTermParams(params, isJavaMethod)

compiler/src/dotty/tools/dotc/parsing/Parsers.scala

@@ -2293,7 +2293,7 @@ object Parsers {
 
     def mkApply(fn: Tree, args: (List[Tree], Boolean)): Tree =
       val res = Apply(fn, args._1)
-      if args._2 then res.setGivenApply()
+      if args._2 then res.setUsingApply()
       res
 
     val argumentExpr: () => Tree = () => exprInParens() match {

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

@@ -390,7 +390,7 @@ class RefinedPrinter(_ctx: Context) extends PlainPrinter(_ctx) {
         else
           toTextLocal(fun)
           ~ "("
-          ~ Str("using ").provided(app.isGivenApply && !homogenizedView)
+          ~ Str("using ").provided(app.isUsingApply && !homogenizedView)
           ~ toTextGlobal(args, ", ")
           ~ ")"
       case tree: TypeApply =>

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

@@ -545,7 +545,7 @@ object Erasure {
       val Apply(fun, args) = tree
       if (fun.symbol == defn.cbnArg)
         typedUnadapted(args.head, pt)
-      else typedExpr(fun, FunProto(args, pt)(this, isGivenApply = false)) match {
+      else typedExpr(fun, FunProto(args, pt)(this, isUsingApply = false)) match {
         case fun1: Apply => // arguments passed in prototype were already passed
           fun1
         case fun1 =>

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

@@ -833,7 +833,7 @@ trait Applications extends Compatibility {
   def typedApply(tree: untpd.Apply, pt: Type)(implicit ctx: Context): Tree = {
 
     def realApply(implicit ctx: Context): Tree = {
-      val originalProto = new FunProto(tree.args, IgnoredProto(pt))(this, tree.isGivenApply)(argCtx(tree))
+      val originalProto = new FunProto(tree.args, IgnoredProto(pt))(this, tree.isUsingApply)(argCtx(tree))
       record("typedApply")
       val fun1 = typedFunPart(tree.fun, originalProto)
 
@@ -1299,6 +1299,16 @@ trait Applications extends Compatibility {
     }
   }
 
+  /** Drop any implicit parameter section */
+  def stripImplicit(tp: Type)(using Context): Type = tp match {
+    case mt: MethodType if mt.isImplicitMethod =>
+      stripImplicit(resultTypeApprox(mt))
+    case pt: PolyType =>
+      pt.derivedLambdaType(pt.paramNames, pt.paramInfos, stripImplicit(pt.resultType))
+    case _ =>
+      tp
+  }
+
   /** Compare owner inheritance level.
     *  @param    sym1 The first owner
     *  @param    sym2 The second owner
@@ -1466,16 +1476,6 @@ trait Applications extends Compatibility {
         else tp
     }
 
-    /** Drop any implicit parameter section */
-    def stripImplicit(tp: Type): Type = tp match {
-      case mt: MethodType if mt.isImplicitMethod =>
-        stripImplicit(resultTypeApprox(mt))
-      case pt: PolyType =>
-        pt.derivedLambdaType(pt.paramNames, pt.paramInfos, stripImplicit(pt.resultType))
-      case _ =>
-        tp
-    }
-
     def compareWithTypes(tp1: Type, tp2: Type) = {
       val ownerScore = compareOwner(alt1.symbol.maybeOwner, alt2.symbol.maybeOwner)
       def winsType1 = isAsSpecific(alt1, tp1, alt2, tp2)
@@ -1707,6 +1707,22 @@ trait Applications extends Compatibility {
       case _ => arg
     end normArg
 
+    /** Resolve overloading by mapping to a different problem where each alternative's
+     *  type is mapped with `f`, alternatives with non-existing types are dropped, and the
+     *  expected type is `pt`. Map the results back to the original alternatives.
+     */
+    def resolveMapped(alts: List[TermRef], f: TermRef => Type, pt: Type): List[TermRef] =
+      val reverseMapping = alts.flatMap { alt =>
+        val t = f(alt)
+        if t.exists then
+          Some((TermRef(NoPrefix, alt.symbol.asTerm.copy(info = t)), alt))
+        else
+          None
+      }
+      val mapped = reverseMapping.map(_._1)
+      overload.println(i"resolve mapped: $mapped")
+      resolveOverloaded(mapped, pt, targs).map(reverseMapping.toMap)
+
     val candidates = pt match {
       case pt @ FunProto(args, resultType) =>
         val numArgs = args.length
@@ -1747,6 +1763,15 @@ trait Applications extends Compatibility {
             alts2
         }
 
+        if pt.isUsingApply then
+          val alts0 = alts.filterConserve { alt =>
+            val mt = alt.widen.stripPoly
+            mt.isImplicitMethod || mt.isContextualMethod
+          }
+          if alts0 ne alts then return resolveOverloaded(alts0, pt, targs)
+        else if alts.exists(_.widen.stripPoly.isContextualMethod) then
+          return resolveMapped(alts, alt => stripImplicit(alt.widen), pt)
+
         val alts1 = narrowBySize(alts)
         //ctx.log(i"narrowed by size: ${alts1.map(_.symbol.showDcl)}%, %")
         if isDetermined(alts1) then alts1
@@ -1783,32 +1808,20 @@ trait Applications extends Compatibility {
         else compat
     }
 
-    /** For each candidate `C`, a proxy termref paired with `C`.
-     *  The proxy termref has as symbol a copy of the original candidate symbol,
-     *  with an info that strips the first value parameter list away.
-     *  @param  argTypes  The types of the arguments of the FunProto `pt`.
+    /** The type of alternative `alt` after instantiating its first parameter
+     *  clause with `argTypes`.
      */
-    def advanceCandidates(argTypes: List[Type]): List[(TermRef, TermRef)] = {
-      def strippedType(tp: Type): Type = tp match {
+    def skipParamClause(argTypes: List[Type])(alt: TermRef): Type =
+      def skip(tp: Type): Type = tp match {
         case tp: PolyType =>
-          val rt = strippedType(tp.resultType)
+          val rt = skip(tp.resultType)
           if (rt.exists) tp.derivedLambdaType(resType = rt) else rt
         case tp: MethodType =>
           tp.instantiate(argTypes)
         case _ =>
           NoType
       }
-      def cloneCandidate(cand: TermRef): List[(TermRef, TermRef)] = {
-        val strippedInfo = strippedType(cand.widen)
-        if (strippedInfo.exists) {
-          val sym = cand.symbol.asTerm.copy(info = strippedInfo)
-          (TermRef(NoPrefix, sym), cand) :: Nil
-        }
-        else Nil
-      }
-      overload.println(i"look at more params: ${candidates.head.symbol}: ${candidates.map(_.widen)}%, % with $pt, [$targs%, %]")
-      candidates.flatMap(cloneCandidate)
-    }
+      skip(alt.widen)
 
     def resultIsMethod(tp: Type): Boolean = tp.widen.stripPoly match
       case tp: MethodType => tp.resultType.isInstanceOf[MethodType]
@@ -1821,9 +1834,7 @@ trait Applications extends Compatibility {
       deepPt match
         case pt @ FunProto(_, resType: FunProto) =>
           // try to narrow further with snd argument list
-          val advanced = advanceCandidates(pt.typedArgs().tpes)
-          resolveOverloaded(advanced.map(_._1), resType, Nil) // resolve with candidates where first params are stripped
-            .map(advanced.toMap) // map surviving result(s) back to original candidates
+          resolveMapped(candidates, skipParamClause(pt.typedArgs().tpes), resType)
         case _ =>
           // prefer alternatives that need no eta expansion
           val noCurried = alts.filter(!resultIsMethod(_))

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

@@ -233,7 +233,7 @@ object EtaExpansion extends LiftImpure {
     if (mt.paramInfos.nonEmpty && mt.paramInfos.last.isRepeatedParam)
       ids = ids.init :+ repeated(ids.last)
     val app = Apply(lifted, ids)
-    if (mt.isContextualMethod) app.setGivenApply()
+    if (mt.isContextualMethod) app.setUsingApply()
     val body = if (isLastApplication) app else PostfixOp(app, Ident(nme.WILDCARD))
     val fn =
       if (mt.isContextualMethod) new untpd.FunctionWithMods(params, body, Modifiers(Given))

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

@@ -228,7 +228,7 @@ object ProtoTypes {
 
   trait ApplyingProto extends ProtoType   // common trait of ViewProto and FunProto
   trait FunOrPolyProto extends ProtoType { // common trait of PolyProto and FunProto
-    def isGivenApply: Boolean = false
+    def isUsingApply: Boolean = false
   }
 
   class FunProtoState {
@@ -251,7 +251,7 @@ object ProtoTypes {
    *  [](args): resultType
    */
   case class FunProto(args: List[untpd.Tree], resType: Type)(typer: Typer,
-    override val isGivenApply: Boolean, state: FunProtoState = new FunProtoState)(implicit val ctx: Context)
+    override val isUsingApply: Boolean, state: FunProtoState = new FunProtoState)(implicit val ctx: Context)
   extends UncachedGroundType with ApplyingProto with FunOrPolyProto {
     override def resultType(implicit ctx: Context): Type = resType
 
@@ -265,7 +265,7 @@ object ProtoTypes {
 
     def derivedFunProto(args: List[untpd.Tree] = this.args, resultType: Type, typer: Typer = this.typer): FunProto =
       if ((args eq this.args) && (resultType eq this.resultType) && (typer eq this.typer)) this
-      else new FunProto(args, resultType)(typer, isGivenApply)
+      else new FunProto(args, resultType)(typer, isUsingApply)
 
     /** @return True if all arguments have types.
      */
@@ -355,7 +355,7 @@ object ProtoTypes {
       case pt: FunProto =>
         pt
       case _ =>
-        state.tupled = new FunProto(untpd.Tuple(args) :: Nil, resultType)(typer, isGivenApply)
+        state.tupled = new FunProto(untpd.Tuple(args) :: Nil, resultType)(typer, isUsingApply)
         tupled
     }
 
@@ -390,14 +390,14 @@ object ProtoTypes {
 
     override def withContext(newCtx: Context): ProtoType =
       if (newCtx `eq` ctx) this
-      else new FunProto(args, resType)(typer, isGivenApply, state)(newCtx)
+      else new FunProto(args, resType)(typer, isUsingApply, 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, isGivenApply: Boolean)(implicit ctx: Context) extends FunProto(args, resultType)(typer, isGivenApply)(ctx) {
+  class FunProtoTyped(args: List[tpd.Tree], resultType: Type)(typer: Typer, isUsingApply: Boolean)(implicit ctx: Context) extends FunProto(args, resultType)(typer, isUsingApply)(ctx) {
     override def typedArgs(norm: (untpd.Tree, Int) => untpd.Tree)(implicit ctx: Context): List[tpd.Tree] = args
     override def withContext(ctx: Context): FunProtoTyped = this
   }
@@ -444,7 +444,7 @@ object ProtoTypes {
   }
 
   class UnapplyFunProto(argType: Type, typer: Typer)(implicit ctx: Context) extends FunProto(
-    untpd.TypedSplice(dummyTreeOfType(argType)(ctx.source))(ctx) :: Nil, WildcardType)(typer, isGivenApply = false)
+    untpd.TypedSplice(dummyTreeOfType(argType)(ctx.source))(ctx) :: Nil, WildcardType)(typer, isUsingApply = false)
 
   /** A prototype for expressions [] that are type-parameterized:
    *

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

@@ -1015,7 +1015,7 @@ class Typer extends Namer
             case _ =>
               given nestedCtx as Context = ctx.fresh.setNewTyperState()
               val protoArgs = args map (_ withType WildcardType)
-              val callProto = FunProto(protoArgs, WildcardType)(this, app.isGivenApply)
+              val callProto = FunProto(protoArgs, WildcardType)(this, app.isUsingApply)
               val expr1 = typedExpr(expr, callProto)
               if nestedCtx.reporter.hasErrors then NoType
               else
@@ -2640,7 +2640,7 @@ class Typer extends Namer
             errorTree(tree, NoMatchingOverload(altDenots, pt)(err))
           def hasEmptyParams(denot: SingleDenotation) = denot.info.paramInfoss == ListOfNil
           pt match {
-            case pt: FunOrPolyProto if !pt.isGivenApply =>
+            case pt: FunOrPolyProto if !pt.isUsingApply =>
               // insert apply or convert qualifier, but only for a regular application
               tryInsertApplyOrImplicit(tree, pt, locked)(noMatches)
             case _ =>
@@ -2791,7 +2791,7 @@ class Typer extends Namer
             }
             tryEither {
               val app = cpy.Apply(tree)(untpd.TypedSplice(tree), namedArgs)
-              if (wtp.isContextualMethod) app.setGivenApply()
+              if (wtp.isContextualMethod) app.setUsingApply()
               typr.println(i"try with default implicit args $app")
               typed(app, pt, locked)
             } { (_, _) =>
@@ -2808,7 +2808,7 @@ class Typer extends Namer
         }
       }
       pt.revealIgnored match {
-        case pt: FunProto if pt.isGivenApply =>
+        case pt: FunProto if pt.isUsingApply =>
           // We can end up here if extension methods are called with explicit given arguments.
           // See for instance #7119.
           tree
@@ -3230,8 +3230,8 @@ class Typer extends Namer
    *  Overridden in `ReTyper`, where all applications are treated the same
    */
   protected def matchingApply(methType: MethodOrPoly, pt: FunProto)(implicit ctx: Context): Boolean =
-    methType.isContextualMethod == pt.isGivenApply ||
-    methType.isImplicitMethod && pt.isGivenApply // for a transition allow `with` arguments for regular implicit parameters
+    methType.isContextualMethod == pt.isUsingApply ||
+    methType.isImplicitMethod && pt.isUsingApply // for a transition allow `with` arguments for regular implicit parameters
 
   /** Check that `tree == x: pt` is typeable. Used when checking a pattern
    *  against a selector of type `pt`. This implementation accounts for