fixes #6843

tests/statictypes/tstackmatrix.nim

@@ -0,0 +1,29 @@
+discard """
+  output: "(M: 3, N: 3, fp: ...)"
+"""
+
+# bug #6843
+
+type
+  OrderType = enum colMajor, rowMajor
+  Matrix[A] = object
+    M, N: int
+    fp: ptr A # float pointer
+  DoubleArray64[M, N: static[int]] = array[M, array[N, float64]]
+
+
+proc stackMatrix[M, N: static[int]](a: var DoubleArray64[M, N], order = colMajor): Matrix[float64] =
+  Matrix[float64](
+    fp: addr a[0][0],
+    M: (if order == colMajor: N else: M),
+    N: (if order == colMajor: M else: N)
+  )
+
+var
+  data = [
+    [1'f64, 2, 3],
+    [4'f64, 5, 6],
+    [7'f64, 8, 9]
+  ]
+  m = stackMatrix(data)
+echo m