closes #25294; adds a test case (#25833)

closes #25294

tests/ccgbugs2/m25294/c.nim

@@ -0,0 +1,13 @@
+template a(T: type): int =
+  when T is uint64: 1 else: 2
+
+type
+  M*[T] = object
+    data*: seq[T]
+    b: seq[int]
+    indices*: array[a(T), int64]
+  U = distinct uint64
+  D* = object
+    c: M[U]
+    v: array[180000, int64]
+    g*: M[uint64]

tests/ccgbugs2/m25294/t.nim

@@ -0,0 +1,5 @@
+import ./c
+
+proc p*(): D =
+  let c = M[uint64](data: @[0], indices: [1])
+  result = D(g: c)

tests/ccgbugs2/t25294.nim

@@ -0,0 +1,18 @@
+discard """
+  matrix: "--mm:refc; --mm:orc"
+"""
+
+import ./m25294/[c, t]
+
+block:
+  let a = new D
+  a[] = p()
+  discard a[]
+block:
+  let a = new D
+  a[] = p()
+  discard a[]
+block:
+  let a = new D
+  a[] = p()
+  discard a[]