Add testcase for #14601 (#15677)

tests/destructor/tdestructor3.nim

@@ -127,4 +127,48 @@ proc test2() =
 echo "---------------"
 echo "app begin"
 test2()
-echo "app end"
+echo "app end"
+
+# bug #14601
+
+when true: # D20200607T202043
+  type Foo2 = object
+    x: int
+    x2: array[10, int]
+
+  type Vec = object
+    vals: seq[Foo2]
+
+  proc `=destroy`*(a: var Foo2) {.inline.} =
+    discard
+
+  proc initFoo2(x: int): Foo2 = Foo2(x: x)
+
+  proc add2(v: var Vec, a: Foo2) = # ditto with `a: sink Foo2`
+    v.vals.add a
+
+  proc add3(v: var Vec, a: Foo2) = # ditto with `a: sink Foo2`
+    v.vals = @[a]
+
+  proc add4(v: var Vec, a: sink Foo2) = # ditto with `a: sink Foo2`
+    v.vals.add a
+
+  proc add5(v: var Vec, a: sink Foo2) = # ditto with `a: sink Foo2`
+    v.vals = @[a]
+
+  proc main2()=
+    var a: Vec
+    var b = Foo2(x: 10)
+    a.add2 b # ok
+    a.vals.add Foo2(x: 10) # ok
+    a.add2 initFoo2(x = 10) # ok
+    a.add2 Foo2(x: 10) # bug
+    a.add3 initFoo2(x = 10) # ok
+    a.add3 Foo2(x: 10) # bug
+    a.add4 initFoo2(x = 10) # ok
+    a.add4 Foo2(x: 10) # bug
+    a.add5 initFoo2(x = 10) # ok
+    a.add5 Foo2(x: 10) # bug
+  main2()
+
+