From 63d68bf4d3cbac82f6d9faf19acd5589603a17ee Mon Sep 17 00:00:00 2001
From: Nicolas Stucki <nicolas.stucki@gmail.com>
Date: Thu, 5 Jan 2017 09:58:21 +0100
Subject: [PATCH] Fix #1878: Generate fields for final vars.

---
 .../dotty/tools/dotc/transform/Memoize.scala  |  2 +-
 tests/run/final-var.check                     |  4 ++++
 tests/run/final-var.scala                     | 20 +++++++++++++++++++
 3 files changed, 25 insertions(+), 1 deletion(-)
 create mode 100644 tests/run/final-var.check
 create mode 100644 tests/run/final-var.scala

diff --git a/compiler/src/dotty/tools/dotc/transform/Memoize.scala b/compiler/src/dotty/tools/dotc/transform/Memoize.scala
index 0314d4ec4b10..63edc0256c1d 100644
--- a/compiler/src/dotty/tools/dotc/transform/Memoize.scala
+++ b/compiler/src/dotty/tools/dotc/transform/Memoize.scala
@@ -102,7 +102,7 @@ import Decorators._
           case _ => t
         }
         skipBlocks(tree.rhs) match {
-          case lit: Literal if sym.is(Final) && isIdempotentExpr(tree.rhs) =>
+          case lit: Literal if sym.is(Final, butNot = Mutable) && isIdempotentExpr(tree.rhs) =>
             // duplicating scalac behavior: for final vals that have rhs as constant, we do not create a field
             // and instead return the value. This seemingly minor optimization has huge effect on initialization
             // order and the values that can be observed during superconstructor call
diff --git a/tests/run/final-var.check b/tests/run/final-var.check
new file mode 100644
index 000000000000..7565230c01f7
--- /dev/null
+++ b/tests/run/final-var.check
@@ -0,0 +1,4 @@
+false
+true
+false
+true
diff --git a/tests/run/final-var.scala b/tests/run/final-var.scala
new file mode 100644
index 000000000000..94a6c453cbda
--- /dev/null
+++ b/tests/run/final-var.scala
@@ -0,0 +1,20 @@
+object Test {
+  def main(args: Array[String]): Unit = {
+    println(Obj.myFinalVar)
+    Obj.myFinalVar = true
+    println(Obj.myFinalVar)
+
+    val o = new Cls
+    println(o.myFinalVar)
+    o.myFinalVar = true
+    println(o.myFinalVar)
+  }
+}
+
+object Obj {
+  final var myFinalVar: Boolean = false
+}
+
+class Cls {
+  final var myFinalVar: Boolean = false
+}