Fix double evaluation of scrutinee with side-effects, add test

2 files changed, 17 insertions, 0 deletions

diff --git a/tests/run/isInstanceOf-eval.check b/tests/run/isInstanceOf-eval.check
new file mode 100644
index 000000000..1191247b6
--- /dev/null
+++ b/tests/run/isInstanceOf-eval.check
@@ -0,0 +1,2 @@
+1
+2
diff --git a/tests/run/isInstanceOf-eval.scala b/tests/run/isInstanceOf-eval.scala
new file mode 100644
index 000000000..aa907b697
--- /dev/null
+++ b/tests/run/isInstanceOf-eval.scala
@@ -0,0 +1,15 @@
+object Test extends dotty.runtime.LegacyApp {
+  lazy val any = {
+    println(1)
+    1: Any
+  }
+
+  any.isInstanceOf[Int]
+
+  lazy val int = {
+    println(2)
+    2
+  }
+
+  int.isInstanceOf[Int]
+}