close nim-lang#11637(add testcase for nim-lang#11637) (nim-lang#15879)

* close nim-lang#11637(add testcase for nim-lang#11637)

* Update tests/vm/t11637.nim

Author: ringabout

tests/vm/t11637.nim

@@ -0,0 +1,52 @@
+type Foo = ref object
+  val: int
+
+proc `+`(a, b: Foo): Foo =
+  Foo(val: a.val + b.val)
+
+proc `*`(a: Foo, b: int): Foo =
+  Foo(val: a.val * b)
+
+proc `+=`(a: var Foo, b: Foo) =
+  a = Foo(
+    val: a.val + b.val
+  )
+
+proc foobar(a, b, c: Foo): tuple[bar, baz, buzz: Foo] =
+
+  let foo = a + b + c
+  result.bar = foo * 2
+
+  result.baz = foo * 3
+  result.buzz = result.baz
+
+  result.buzz += a * 10000
+  result.baz += b
+  result.buzz += b
+
+
+block: # Compile-Time
+  let
+    a {.compileTime.} = Foo(val: 1)
+    b {.compileTime.} = Foo(val: 2)
+    c {.compileTime.} = Foo(val: 3)
+    r {.compileTime.} = foobar(a, b, c)
+
+  static:
+    doAssert r.bar.val == 12
+    doAssert r.baz.val == 20
+    doAssert r.buzz.val == 10020
+
+####################################
+
+block: # Run-time
+  let
+    a = Foo(val: 1)
+    b = Foo(val: 2)
+    c = Foo(val: 3)
+    r = foobar(a, b, c)
+
+  # Expected values
+  doAssert r.bar.val == 12
+  doAssert r.baz.val == 20
+  doAssert r.buzz.val == 10020