Make sure that prefixes are not accidentally erased

Author: nicolasstucki

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

@@ -45,15 +45,13 @@ class UnusedRefs extends MiniPhase {
       tree.tpe.widen match {
         case _: MethodOrPoly => tree // Do the transformation higher in the tree if needed
         case _ =>
-          tree match {
-            case _: RefTree | _: TypeApply => defaultValue(tree.tpe)
-            case Apply(_ , args) =>
-            def allArgs(t: Tree, acc: List[Tree]): List[Tree] = t match {
-              case Apply(fun, args) => allArgs(fun, args ::: acc)
-              case _ => acc
-            }
-            seq(allArgs(tree, Nil), defaultValue(tree.tpe))
+          def qualAndArgs(t: Tree, acc: List[Tree]): List[Tree] = t match {
+            case TypeApply(fun, _) => qualAndArgs(fun, acc)
+            case Apply(fun, args) => qualAndArgs(fun, args ::: acc)
+            case Select(qual, _) => qual :: acc
+            case _ => acc
           }
+          seq(qualAndArgs(tree, Nil), defaultValue(tree.tpe))
       }
     }
   }

tests/run/unused-select-prefix.check

@@ -0,0 +1,4 @@
+Test0
+Test1
+Test2
+Test3

tests/run/unused-select-prefix.scala

@@ -0,0 +1,32 @@
+object Test {
+
+  def main(args: Array[String]): Unit = {
+    {
+      println("Test0")
+      Test
+    }.foo0
+
+    {
+      println("Test1")
+      Test
+    }.foo1()
+
+    {
+      println("Test2")
+      Test
+    }.foo2[Int]
+
+    {
+      println("Test3")
+      Test
+    }.foo3[Int]()
+
+    ()
+  }
+
+  unused def foo0: Int = 0
+  unused def foo1(): Int = 1
+  unused def foo2[T]: Int = 2
+  unused def foo3[T](): Int = 3
+
+}