Merge pull request scala#5770 from som-snytt/issue/6714

SI-6714 Update assignment preserves apply args

Author: lrytz

src/compiler/scala/tools/nsc/typechecker/Typers.scala

@@ -4759,7 +4759,7 @@ trait Typers extends Adaptations with Tags with TypersTracking with PatternTyper
               Select(vble.duplicate, prefix) setPos fun.pos.focus, args) setPos tree.pos.makeTransparent
           ) setPos tree.pos
 
-        def mkUpdate(table: Tree, indices: List[Tree]) =
+        def mkUpdate(table: Tree, indices: List[Tree], argss: List[List[Tree]]) =
           gen.evalOnceAll(table :: indices, context.owner, context.unit) {
             case tab :: is =>
               def mkCall(name: Name, extraArgs: Tree*) = (
@@ -4768,9 +4768,10 @@ trait Typers extends Adaptations with Tags with TypersTracking with PatternTyper
                   is.map(i => i()) ++ extraArgs
                 ) setPos tree.pos
               )
+              def mkApplies(core: Tree) = argss.foldLeft(core)((x, args) => Apply(x, args))
               mkCall(
                 nme.update,
-                Apply(Select(mkCall(nme.apply), prefix) setPos fun.pos, args) setPos tree.pos
+                Apply(Select(mkApplies(mkCall(nme.apply)), prefix) setPos fun.pos, args) setPos tree.pos
               )
             case _ => EmptyTree
           }
@@ -4785,9 +4786,18 @@ trait Typers extends Adaptations with Tags with TypersTracking with PatternTyper
               mkAssign(Select(qq1, vname) setPos qual.pos)
             }
 
+          case Apply(fn, extra) if qual.isInstanceOf[ApplyToImplicitArgs] =>
+            fn match {
+              case treeInfo.Applied(Select(table, nme.apply), _, indices :: Nil) =>
+                // table(indices)(implicits)
+                mkUpdate(table, indices, extra :: Nil)
+              case _  => UnexpectedTreeAssignmentConversionError(qual)
+            }
+
           case Apply(fn, indices) =>
             fn match {
-              case treeInfo.Applied(Select(table, nme.apply), _, _) => mkUpdate(table, indices)
+              case treeInfo.Applied(Select(table, nme.apply), _, Nil) =>
+                mkUpdate(table, indices, Nil)
               case _  => UnexpectedTreeAssignmentConversionError(qual)
             }
         }

test/files/neg/t6714.check

@@ -0,0 +1,7 @@
+t6714.scala:19: error: Unexpected tree during assignment conversion.
+  a(1)(9000) += 20  // Not OK
+      ^
+t6714.scala:21: error: Unexpected tree during assignment conversion.
+  b(1)(5) += 20     // Not OK
+      ^
+two errors found

test/files/neg/t6714.scala

@@ -0,0 +1,22 @@
+
+case class A(a: Int, index: Int) {
+  def apply(i: Int)(implicit ev: Int): A = new A(ev, i)
+  def update(i: Int, value: Int): A = if (i == index) A(i, value) else A(i, 0)
+  def +(j: Int) = a + j
+}
+
+case class B(a: Int, index: Int) {
+  def apply(i: Int)(j: Int)(implicit ev: Int): B = new B(j + ev, i)
+  def update(i: Int, value: Int): B = if (i == index) B(i, value) else B(i, 0)
+  def +(j: Int) = a + j
+}
+
+object Test extends App {
+  implicit def ev: Int = 8000
+  val a = A(5, 1)
+  a(1) = 10         // OK
+  a(1) += 20        // OK
+  a(1)(9000) += 20  // Not OK
+  val b = B(5, 1)
+  b(1)(5) += 20     // Not OK
+}

test/files/run/t6714.scala

@@ -0,0 +1,19 @@
+
+case class A(a: Int, index: Int) {
+  def apply(i: Int)(implicit ev: Int): A = new A(ev, i)
+  def update(i: Int, value: Int): A = if (i == index) A(i, value) else A(i, 0)
+  def +(j: Int) = a + j
+}
+
+object Test extends App {
+  def checkA(x: A, y: Int, z: Int) = assert(x == A(y, z))
+  implicit def ev: Int = 8000
+  val a = A(5, 1)
+  checkA(a(1) = 10, 1, 10)
+  checkA(a(1) += 20, 1, 8020)
+}
+
+/*
+ A(1,10)
+ A(1,8020) // was A(8000,0)
+ */