fix #14339, #13511, #14420: fixes limited VM support for addr (#16002)

* fix #14339: fixes limited VM support for addr

* strengthen test

* reference bug #16003

* also fixes #13511

* also fixes #14420

tests/misc/taddr.nim

@@ -123,3 +123,83 @@ block:
   block: # pending bug #15959
     when false:
       proc byLent2[T](a: T): lent type(a[0]) = a[0]
+
+proc test14420() = # bug #14420
+  # s/proc/template/ would hit bug #16005
+  block:
+    type Foo = object
+      x: float
+
+    proc fn(a: var Foo): var float =
+      ## WAS: discard <- turn this into a comment (or a `discard`) and error disappears
+      # result = a.x # this works
+      a.x #  WAS: Error: limited VM support for 'addr'
+
+    proc fn2(a: var Foo): var float =
+      result = a.x # this works
+      a.x #  WAS: Error: limited VM support for 'addr'
+
+    var a = Foo()
+    discard fn(a)
+    discard fn2(a)
+
+  block:
+    proc byLent2[T](a: T): lent T =
+      runnableExamples: discard
+      a
+    proc byLent3[T](a: T): lent T =
+      runnableExamples: discard
+      result = a
+    var a = 10
+    let x3 = byLent3(a) # works
+    let x2 = byLent2(a) # WAS: Error: internal error: genAddr: nkStmtListExpr
+
+  block:
+    type MyOption[T] = object
+      case has: bool
+      of true:
+        value: T
+      of false:
+        discard
+    func some[T](val: T): MyOption[T] =
+      result = MyOption[T](has: true, value: val)
+    func get[T](opt: MyOption[T]): lent T =
+      doAssert opt.has
+      # result = opt.value # this was ok
+      opt.value # this had the bug
+    let x = some(10)
+    doAssert x.get() == 10
+
+template test14339() = # bug #14339
+  block:
+    type
+      Node = ref object
+        val: int
+    proc bar(c: Node): var int =
+      var n = c # was: Error: limited VM support for 'addr'
+      c.val
+    var a = Node()
+    discard a.bar()
+  block:
+    type
+      Node = ref object
+        val: int
+    proc bar(c: Node): var int =
+      var n = c
+      doAssert n.val == n[].val
+      n.val
+    var a = Node(val: 3)
+    a.bar() = 5
+    when nimvm:
+      doAssert a.val == 5
+    else:
+      when not defined(js): # pending bug #16003
+        doAssert a.val == 5
+
+template main =
+  # xxx wrap all other tests here like that so they're also tested in VM
+  test14420()
+  test14339()
+
+static: main()
+main()