Object downconversion in VM should not copy (#10378)

Hopefully the type-check phase already rejected all the invalid
conversions by the time we execute the VM bytecode.

Problem reported by chrisheller on the Nim Forum

1 files changed, 17 insertions, 0 deletions

diff --git a/tests/vm/tconstobj.nim b/tests/vm/tconstobj.nim
index 021fcb728..3cf256eed 100644
--- a/tests/vm/tconstobj.nim
+++ b/tests/vm/tconstobj.nim
@@ -48,3 +48,20 @@ let people = {
 }.toTable()
 
 echo people["001"]
+
+# Object downconversion should not copy
+
+type
+  SomeBaseObj  {.inheritable.} = object of RootObj
+    txt : string
+  InheritedFromBase = object of SomeBaseObj
+    other : string
+
+proc initBase(sbo: var SomeBaseObj) =
+  sbo.txt = "Initialized string from base"
+
+static:
+  var ifb2: InheritedFromBase
+  initBase(SomeBaseObj(ifb2))
+  echo repr(ifb2)
+  doAssert(ifb2.txt == "Initialized string from base")