fixes #4653

compiler/ccgexprs.nim

@@ -670,6 +670,8 @@ proc genDeref(p: BProc, e: PNode, d: var TLoc; enforceDeref=false) =
     #if e[0].kind != nkBracketExpr:
     #  message(e.info, warnUser, "CAME HERE " & renderTree(e))
     expr(p, e.sons[0], d)
+    if e.sons[0].typ.skipTypes(abstractInst).kind == tyRef:
+      d.s = OnHeap
   else:
     var a: TLoc
     let typ = skipTypes(e.sons[0].typ, abstractInst)

tests/ccgbugs/twrong_rc_for_refarray.nim

@@ -0,0 +1,26 @@
+discard """
+  output: '''m[0][0] = 1.0
+m[0][0] = 2.0'''
+"""
+# bug #4653
+type
+  Vector = ref array[2, float64]
+  Matrix = ref array[2, Vector]
+
+proc newVector(): Vector =
+  new(result)
+
+proc newMatrix(): Matrix =
+  new(result)
+  for ix in 0 .. 1:
+    result[ix] = newVector()
+
+let m = newMatrix()
+
+m[0][0] = 1.0
+echo "m[0][0] = ", m[0][0]
+
+GC_fullCollect()
+
+m[0][0] = 2.0
+echo "m[0][0] = ", m[0][0]