Merge pull request scala#7963 from hrhino/t11465

Eta lifts function before args.
ShapelessCat · Jun 18, 2019 · c1be65a · c1be65a
2 parents 14e469f + 64a2e55
commit c1be65a
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Showing 5 changed files with 17 additions and 5 deletions.
diff --git a/spec/06-expressions.md b/spec/06-expressions.md
@@ -431,8 +431,8 @@ The method values in the left column are each equivalent to the [eta-expanded ex
 |`math.sin _`                   | `x => math.sin(x)`                                                          |
 |`math.pow _`                   | `(x1, x2) => math.pow(x1, x2)`                                              |
 |`val vs = 1 to 9; vs.fold _`   | `(z) => (op) => vs.fold(z)(op)`                                             |
-|`(1 to 9).fold(z)_`            | `{ val eta1 = z; val eta2 = 1 to 9; op => eta2.fold(eta1)(op) }`            |
-|`Some(1).fold(??? : Int)_`     | `{ val eta1 = () => ???; val eta2 = Some(1); op => eta2.fold(eta1())(op) }` |
+|`(1 to 9).fold(z)_`            | `{ val eta1 = 1 to 9; val eta2 = z; op => eta1.fold(eta2)(op) }`            |
+|`Some(1).fold(??? : Int)_`     | `{ val eta1 = Some(1); val eta2 = () => ???; op => eta1.fold(eta2())(op) }` |
 
 Note that a space is necessary between a method name and the trailing underscore
 because otherwise the underscore would be considered part of the name.

diff --git a/src/compiler/scala/tools/nsc/typechecker/EtaExpansion.scala b/src/compiler/scala/tools/nsc/typechecker/EtaExpansion.scala
@@ -46,7 +46,7 @@ trait EtaExpansion { self: Analyzer =>
     *   - typedEta (when type checking a method value, `m _`).
     *
     **/
-  def etaExpand(unit: CompilationUnit, tree: Tree, owner: Symbol)(implicit creator: FreshNameCreator): Tree = {
+  def etaExpand(tree: Tree, owner: Symbol)(implicit creator: FreshNameCreator): Tree = {
     val tpe = tree.tpe
     var cnt = 0 // for NoPosition
     def freshName() = {
@@ -95,11 +95,12 @@ trait EtaExpansion { self: Analyzer =>
           liftoutPrefix(fun)
         case Apply(fn, args) =>
           val byName: Int => Option[Boolean] = fn.tpe.params.map(p => definitions.isByNameParamType(p.tpe)).lift
+          val liftedFn = liftoutPrefix(fn) // scala/bug#11465: lift fn before args
           val newArgs = mapWithIndex(args) { (arg, i) =>
             // with repeated params, there might be more or fewer args than params
             liftout(arg, byName(i).getOrElse(false))
           }
-          treeCopy.Apply(tree, liftoutPrefix(fn), newArgs).clearType()
+          treeCopy.Apply(tree, liftedFn, newArgs).clearType()
         case TypeApply(fn, args) =>
           treeCopy.TypeApply(tree, liftoutPrefix(fn), args).clearType()
         case Select(qual, name) =>

diff --git a/src/compiler/scala/tools/nsc/typechecker/Typers.scala b/src/compiler/scala/tools/nsc/typechecker/Typers.scala
@@ -3203,7 +3203,7 @@ trait Typers extends Adaptations with Tags with TypersTracking with PatternTyper
 
       if (tree.tpe.isDependentMethodType) DependentMethodTpeConversionToFunctionError(tree, tree.tpe) // TODO: support this
       else {
-        val expansion = etaExpand(context.unit, tree, context.owner)
+        val expansion = etaExpand(tree, context.owner)
         if (context.undetparams.isEmpty) typed(expansion, mode, pt)
         else instantiate(typed(expansion, mode), mode, pt)
       }

diff --git a/test/files/run/t11465.check b/test/files/run/t11465.check
@@ -0,0 +1,6 @@
+F
+Z
+55
+F
+Z
+55
diff --git a/test/files/run/t11465.scala b/test/files/run/t11465.scala
@@ -0,0 +1,5 @@
+object Test extends App {
+  def f = { println("F") ; 1 to 10 }
+  println { f.foldLeft{ println("Z"); 0 }(_ + _) }
+  println { (f.foldLeft{ println("Z"); 0 } _) (_ + _) }
+}
-Original file line number
+Diff line change
@@ -0,0 +1,6 @@
+    F
+    Z
+    F
+    Z