Merge pull request #9576 from dotty-staging/fix-#9562

Fix #9562: Fix handling of identifiers in extension methods

Author: bishabosha

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

@@ -899,7 +899,7 @@ object desugar {
           name = mdef.name.toExtensionName,
           tparams = ext.tparams ++ mdef.tparams,
           vparamss = mdef.vparamss match
-            case vparams1 :: vparamss1 if !isLeftAssoc(mdef.name) =>
+            case vparams1 :: vparamss1 if mdef.name.isRightAssocOperatorName =>
               vparams1 :: ext.vparamss ::: vparamss1
             case _ =>
               ext.vparamss ++ mdef.vparamss
@@ -1204,10 +1204,10 @@ object desugar {
         case _ =>
           Apply(sel, arg :: Nil)
 
-    if (isLeftAssoc(op.name))
-      makeOp(left, right, Span(left.span.start, op.span.end, op.span.start))
-    else
+    if op.name.isRightAssocOperatorName then
       makeOp(right, left, Span(op.span.start, right.span.end))
+    else
+      makeOp(left, right, Span(left.span.start, op.span.end, op.span.start))
   }
 
   /** Translate tuple expressions of arity <= 22

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

@@ -6,6 +6,7 @@ import util.Spans._
 import util.{SourceFile, NoSource, SourcePosition, SrcPos}
 import core.Contexts._
 import core.Decorators._
+import core.NameOps._
 import core.Flags.{JavaDefined, ExtensionMethod}
 import core.StdNames.nme
 import ast.Trees.mods
@@ -208,7 +209,7 @@ abstract class Positioned(implicit @constructorOnly src: SourceFile) extends Src
         check(tree.vparamss)
       case tree: DefDef if tree.mods.is(ExtensionMethod) =>
         tree.vparamss match {
-          case vparams1 :: vparams2 :: rest if !isLeftAssoc(tree.name) =>
+          case vparams1 :: vparams2 :: rest if tree.name.isRightAssocOperatorName =>
             check(tree.tparams)
             check(vparams2)
             check(vparams1)

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

@@ -185,9 +185,6 @@ trait TreeInfo[T >: Untyped <: Type] { self: Trees.Instance[T] =>
     case _ => false
   }
 
-  /** Is name a left-associative operator? */
-  def isLeftAssoc(operator: Name): Boolean = !operator.isEmpty && (operator.toSimpleName.last != ':')
-
   /** Is this argument node of the form <expr> : _*, or is it a reference to
    *  such an argument ? The latter case can happen when an argument is lifted.
    */

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

@@ -19,48 +19,48 @@ object ContextOps:
     def enter(sym: Symbol): Symbol = inContext(ctx) {
       ctx.owner match
         case cls: ClassSymbol => cls.classDenot.enter(sym)
-        case _ => scope.openForMutations.enter(sym)
+        case _ => ctx.scope.openForMutations.enter(sym)
       sym
     }
 
     /** The denotation with the given `name` and all `required` flags in current context
      */
     def denotNamed(name: Name, required: FlagSet = EmptyFlags): Denotation = inContext(ctx) {
-      if (owner.isClass)
-        if (outer.owner == owner) { // inner class scope; check whether we are referring to self
-          if (scope.size == 1) {
-            val elem = scope.lastEntry
+      if (ctx.owner.isClass)
+        if (ctx.outer.owner == ctx.owner) { // inner class scope; check whether we are referring to self
+          if (ctx.scope.size == 1) {
+            val elem = ctx.scope.lastEntry
             if (elem.name == name) return elem.sym.denot // return self
           }
-          val pre = owner.thisType
+          val pre = ctx.owner.thisType
           pre.findMember(name, pre, required, EmptyFlags)
         }
         else // we are in the outermost context belonging to a class; self is invisible here. See inClassContext.
-          owner.findMember(name, owner.thisType, required, EmptyFlags)
+          ctx.owner.findMember(name, ctx.owner.thisType, required, EmptyFlags)
       else
-        scope.denotsNamed(name).filterWithFlags(required, EmptyFlags).toDenot(NoPrefix)
+        ctx.scope.denotsNamed(name).filterWithFlags(required, EmptyFlags).toDenot(NoPrefix)
     }
 
     /** A fresh local context with given tree and owner.
     *  Owner might not exist (can happen for self valdefs), in which case
     *  no owner is set in result context
     */
     def localContext(tree: untpd.Tree, owner: Symbol): FreshContext = inContext(ctx) {
-      val freshCtx = fresh.setTree(tree)
-      if (owner.exists) freshCtx.setOwner(owner) else freshCtx
+      val freshCtx = ctx.fresh.setTree(tree)
+      if owner.exists then freshCtx.setOwner(owner) else freshCtx
     }
 
     /** Context where `sym` is defined, assuming we are in a nested context. */
     def defContext(sym: Symbol): Context = inContext(ctx) {
-      outersIterator
+      ctx.outersIterator
         .dropWhile(_.owner != sym)
         .dropWhile(_.owner == sym)
         .next()
     }
 
     /** A new context for the interior of a class */
     def inClassContext(selfInfo: TypeOrSymbol): Context = inContext(ctx) {
-      val localCtx: Context = fresh.setNewScope
+      val localCtx: Context = ctx.fresh.setNewScope
       selfInfo match {
         case sym: Symbol if sym.exists && sym.name != nme.WILDCARD => localCtx.scope.openForMutations.enter(sym)
         case _ =>
@@ -69,7 +69,7 @@ object ContextOps:
     }
 
     def packageContext(tree: untpd.PackageDef, pkg: Symbol): Context = inContext(ctx) {
-      if (pkg.is(Package)) fresh.setOwner(pkg.moduleClass).setTree(tree)
+      if (pkg.is(Package)) ctx.fresh.setOwner(pkg.moduleClass).setTree(tree)
       else ctx
     }
 end ContextOps

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

@@ -72,6 +72,7 @@ object NameOps {
     def isAnonymousClassName: Boolean = name.startsWith(str.ANON_CLASS)
     def isAnonymousFunctionName: Boolean = name.startsWith(str.ANON_FUN)
     def isUnapplyName: Boolean = name == nme.unapply || name == nme.unapplySeq
+    def isRightAssocOperatorName: Boolean = name.lastPart.last == ':'
 
     def isOperatorName: Boolean = name match
       case name: SimpleName => name.exists(isOperatorPart)

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

@@ -325,6 +325,18 @@ object SymDenotations {
       else recurWithParamss(info, rawParamss)
     end paramSymss
 
+    /** The extension parameter of this extension method
+     *  @pre this symbol is an extension method
+     */
+    final def extensionParam(using Context): Symbol =
+      def leadParam(paramss: List[List[Symbol]]): Symbol = paramss match
+        case (param :: _) :: paramss1 if param.isType => leadParam(paramss1)
+        case _ :: (snd :: Nil) :: _ if name.isRightAssocOperatorName => snd
+        case (fst :: Nil) :: _ => fst
+        case _ => NoSymbol
+      assert(isAllOf(ExtensionMethod))
+      leadParam(rawParamss)
+
     /** The denotation is completed: info is not a lazy type and attributes have defined values */
     final def isCompleted: Boolean = !myInfo.isInstanceOf[LazyType]
 

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

@@ -927,7 +927,7 @@ object Parsers {
     var opStack: List[OpInfo] = Nil
 
     def checkAssoc(offset: Token, op1: Name, op2: Name, op2LeftAssoc: Boolean): Unit =
-      if (isLeftAssoc(op1) != op2LeftAssoc)
+      if (op1.isRightAssocOperatorName == op2LeftAssoc)
         syntaxError(MixedLeftAndRightAssociativeOps(op1, op2, op2LeftAssoc), offset)
 
     def reduceStack(base: List[OpInfo], top: Tree, prec: Int, leftAssoc: Boolean, op2: Name, isType: Boolean): Tree = {
@@ -967,7 +967,7 @@ object Parsers {
       def recur(top: Tree): Tree =
         if (isIdent && isOperator) {
           val op = if (isType) typeIdent() else termIdent()
-          val top1 = reduceStack(base, top, precedence(op.name), isLeftAssoc(op.name), op.name, isType)
+          val top1 = reduceStack(base, top, precedence(op.name), !op.name.isRightAssocOperatorName, op.name, isType)
           opStack = OpInfo(top1, op, in.offset) :: opStack
           colonAtEOLOpt()
           newLineOptWhenFollowing(canStartOperand)
@@ -3316,7 +3316,7 @@ object Parsers {
             typeParamClause(ParamOwner.Def)
           else leadingTparams
         val vparamss = paramClauses() match
-          case rparams :: rparamss if leadingVparamss.nonEmpty && !isLeftAssoc(ident.name) =>
+          case rparams :: rparamss if leadingVparamss.nonEmpty && ident.name.isRightAssocOperatorName =>
             rparams :: leadingVparamss ::: rparamss
           case rparamss =>
             leadingVparamss ::: rparamss

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

@@ -795,7 +795,7 @@ class RefinedPrinter(_ctx: Context) extends PlainPrinter(_ctx) {
         val (prefix, vparamss) =
           if isExtension then
             val (leadingParams, otherParamss) = (tree.vparamss: @unchecked) match
-              case vparams1 :: vparams2 :: rest if !isLeftAssoc(tree.name) =>
+              case vparams1 :: vparams2 :: rest if tree.name.isRightAssocOperatorName =>
                 (vparams2, vparams1 :: rest)
               case vparams1 :: rest =>
                 (vparams1, rest)

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

@@ -409,7 +409,7 @@ class SyntheticMembers(thisPhase: DenotTransformer) {
 
   /** Is this an anonymous class deriving from an enum definition? */
   extension (cls: ClassSymbol) private def isEnumValueImplementation(using Context): Boolean =
-    isAnonymousClass && classParents.head.typeSymbol.is(Enum) // asserted in Typer
+    cls.isAnonymousClass && cls.classParents.head.typeSymbol.is(Enum) // asserted in Typer
 
   /** If this is the class backing a serializable singleton enum value with base class `MyEnum`,
    *  and not deriving from `java.lang.Enum` add the method:

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

@@ -199,9 +199,10 @@ object Applications {
    *  I.e., if the expected type is a PolyProto, then `app` will be a `TypeApply(_, args)` where
    *  `args` are the type arguments of the expected type.
    */
-  class IntegratedTypeArgs(val app: Tree)(implicit @constructorOnly src: SourceFile) extends tpd.Tree {
+  class IntegratedTypeArgs(val app: Tree)(implicit @constructorOnly src: SourceFile) extends ProxyTree {
     override def span = app.span
 
+    def forwardTo = app
     def canEqual(that: Any): Boolean = app.canEqual(that)
     def productArity: Int = app.productArity
     def productElement(n: Int): Any = app.productElement(n)

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

@@ -1110,7 +1110,7 @@ trait Checking {
   def checkEnumParent(cls: Symbol, firstParent: Symbol)(using Context): Unit =
 
     extension (sym: Symbol) def typeRefApplied(using Context): Type =
-      typeRef.appliedTo(typeParams.map(_.info.loBound))
+      sym.typeRef.appliedTo(sym.typeParams.map(_.info.loBound))
 
     def ensureParentDerivesFrom(enumCase: Symbol)(using Context) =
       val enumCls = enumCase.owner.linkedClass

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

@@ -1620,7 +1620,7 @@ class RefChecks extends MiniPhase { thisPhase =>
     private def checkByNameRightAssociativeDef(tree: DefDef) {
       tree match {
         case DefDef(_, name, _, params :: _, _, _) =>
-          if (settings.lint && !treeInfo.isLeftAssoc(name.decodedName) && params.exists(p => isByName(p.symbol)))
+          if (settings.lint && name.decodedName.isRightAssocOperatorName && params.exists(p => isByName(p.symbol)))
             unit.warning(tree.pos,
               "by-name parameters will be evaluated eagerly when called as a right-associative infix operator. For more details, see SI-1980.")
         case _ =>

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

@@ -447,25 +447,6 @@ class Typer extends Namer
     if (name == nme.ROOTPKG)
       return tree.withType(defn.RootPackage.termRef)
 
-    /** Convert a reference `f` to an extension method select `p.f`, where
-     *  `p` is the closest enclosing extension parameter, or else `this`.
-     */
-    def extensionMethodSelect: untpd.Tree =
-      val xmethod = ctx.owner.enclosingExtensionMethod
-      val qualifier =
-        if xmethod.exists then // TODO: see whether we can use paramss for that
-          val leadParamName = xmethod.info.paramNamess.head.head
-          def isLeadParam(sym: Symbol) =
-            sym.is(Param) && sym.owner.owner == xmethod.owner && sym.name == leadParamName
-          def leadParam(ctx: Context): Symbol =
-            ctx.scope.lookupAll(leadParamName).find(isLeadParam) match
-              case Some(param) => param
-              case None => leadParam(ctx.outersIterator.dropWhile(_.scope eq ctx.scope).next)
-          untpd.ref(leadParam(ctx).termRef)
-        else
-          untpd.This(untpd.EmptyTypeIdent)
-      untpd.cpy.Select(tree)(qualifier, name)
-
     val rawType = {
       val saved1 = unimported
       val saved2 = foundUnderScala2
@@ -516,7 +497,20 @@ class Typer extends Namer
     else if name.toTermName == nme.ERROR then
       setType(UnspecifiedErrorType)
     else if name.isTermName then
-      tryEither(typed(extensionMethodSelect, pt))((_, _) => fail)
+      // Convert a reference `f` to an extension method select `p.f`, where
+      // `p` is the closest enclosing extension parameter, or else convert to `this.f`.
+      val xmethod = ctx.owner.enclosingExtensionMethod
+      val qualifier =
+        if xmethod.exists then untpd.ref(xmethod.extensionParam.termRef)
+        else untpd.This(untpd.EmptyTypeIdent)
+      val selection = untpd.cpy.Select(tree)(qualifier, name)
+      val result = tryEither(typed(selection, pt))((_, _) => fail)
+      def canAccessUnqualified(sym: Symbol) =
+        sym.is(ExtensionMethod) && (sym.extensionParam.span == xmethod.extensionParam.span)
+      if !xmethod.exists || result.tpe.isError || canAccessUnqualified(result.symbol) then
+        result
+      else
+        fail
     else
       fail
   end typedIdent
@@ -2348,20 +2342,18 @@ class Typer extends Namer
         typedUnApply(cpy.Apply(tree)(op, l :: r :: Nil), pt)
       else {
         val app = typedApply(desugar.binop(l, op, r), pt)
-        if (untpd.isLeftAssoc(op.name)) app
-        else {
+        if op.name.isRightAssocOperatorName then
           val defs = new mutable.ListBuffer[Tree]
-          def lift(app: Tree): Tree = (app: @unchecked) match {
+          def lift(app: Tree): Tree = (app: @unchecked) match
             case Apply(fn, args) =>
               if (app.tpe.isError) app
               else tpd.cpy.Apply(app)(fn, LiftImpure.liftArgs(defs, fn.tpe, args))
             case Assign(lhs, rhs) =>
               tpd.cpy.Assign(app)(lhs, lift(rhs))
             case Block(stats, expr) =>
               tpd.cpy.Block(app)(stats, lift(expr))
-          }
           wrapDefs(defs, lift(app))
-        }
+        else app
       }
     checkValidInfix(tree, result.symbol)
     result

docs/docs/reference/contextual/extension-methods.md

@@ -76,7 +76,7 @@ extension [T: Numeric](x: T)
 ```
 
 If an extension method has type parameters, they come immediately after `extension` and are followed by the extended parameter.
-When calling a generic extension method, any explicitly given type arguments follow the method name. 
+When calling a generic extension method, any explicitly given type arguments follow the method name.
 So the `second` method could be instantiated as follows:
 
 ```scala
@@ -92,8 +92,8 @@ extension [T](x: T)(using n: Numeric[T])
   def + (y: T): T = n.plus(x, y)
 ```
 
-**Note**: Type parameters have to be given after the `extension` keyword; they cannot be given after the `def`. 
-This restriction might be lifted in the future once we support multiple type parameter clauses in a method. 
+**Note**: Type parameters have to be given after the `extension` keyword; they cannot be given after the `def`.
+This restriction might be lifted in the future once we support multiple type parameter clauses in a method.
 By contrast, using clauses can be defined for the `extension` as well as per `def`.
 
 ### Collective Extensions
@@ -215,7 +215,7 @@ List(1, 2) < List(3)
 
 The precise rules for resolving a selection to an extension method are as follows.
 
-Assume a selection `e.m[Ts]` where `m` is not a member of `e`, where the type arguments `[Ts]` are optional, and where `T` is the expected type. 
+Assume a selection `e.m[Ts]` where `m` is not a member of `e`, where the type arguments `[Ts]` are optional, and where `T` is the expected type.
 The following two rewritings are tried in order:
 
  1. The selection is rewritten to `extension_m[Ts](e)`.
@@ -233,9 +233,11 @@ An extension method can also be used as an identifier by itself. If an identifie
 resolve, the identifier is rewritten to:
 
 - `x.m`    if the identifier appears in an extension with parameter `x`
+           and the method `m` resolves to an extension method in
+           a (possibly collective) extension that also contains the call,
 - `this.m` otherwise
 
-and the rewritten term is again tried as an application of an extension method. Example:
+and the rewritten term is again tried as an application of an extension method. In
 
 ```scala
 extension (s: String)
@@ -264,7 +266,7 @@ def extension_position(s: String)(ch: Char, n: Int): Int =
      extension (x: Double) def ** (exponent: Int): Double =
        require(exponent >= 0)
        if exponent == 0 then 1 else x * (x ** (exponent - 1))
-  
+
    import DoubleOps.{**, extension_**}
    assert(2.0 ** 3 == extension_**(2.0)(3))
    ```

tests/neg/i9562.scala

@@ -0,0 +1,12 @@
+class Foo:
+  def foo = 23
+
+object Unrelated:
+  extension (f: Foo)
+    def g = f.foo // OK
+
+  extension (f: Foo)
+    def h1: Int = foo     // error
+    def h2: Int = h1 + 1  // OK
+    def h3: Int = g       // error
+    def ++: (x: Int): Int = h1 + x  // OK

tests/pos/i9562.scala

@@ -0,0 +1,11 @@
+class Foo:
+  def foo = 23
+
+object Unrelated:
+  extension (f: Foo)
+    def g = f.foo // OK
+
+  extension (f: Foo)
+    def h1: Int = 0
+    def h2: Int = h1 + 1  // OK
+    def ++: (x: Int): Int = h2 + x  // OK