TXR Lisp:

Using quasiquote-style pattern:

   (if-match ^#S(point x ,x y ,y) obj
     (prinl (+ x y))

Or using @(struct ...) pattern operator:

   (if-match @(struct point x @x y @y) obj
     (prinl (+ x y))

All done with macros. Expansion, compilation, disassembly:

  4> (flow '(if-match @(struct point x @x y @y) (new (point 1 2))
              (prinl (+ x y)))
       expand
       prinl
       compile-toplevel
       disassemble)
  (let ((#:g0062 (struct-from-args 'point 1 2)))
    (let* (#:result-0065
           x y)
      (if (if (subtypep (typeof #:g0062)
                        'point)
            (let ((#:x0063 (slot #:g0062 'x))
                  (#:y0064 (slot #:g0062 'y)))
              (sys:setq x #:x0063)
              (sys:setq y #:y0064)
              (sys:setq #:result-0065
                (prinl (+ x y)))
              t))
        #:result-0065
        ())))
  data:
      0: point
      1: 1
      2: 2
      3: x
      4: y
  syms:
      0: struct-from-args
      1: subtypep
      2: typeof
      3: slot
      4: prinl
      5: sys:b+
  code:
      0: 2003000E gcall t14 0 d0 d1 d2
      1: 04000000
      2: 04020401
      3: 20010005 gcall t5 2 t14
      4: 000E0002
      5: 20020002 gcall t2 1 t5 d0
      6: 00050001
      7: 00000400
      8: 38000016 if t2 22
      9: 00000002
     10: 2002000A gcall t10 3 t14 d3
     11: 000E0003
     12: 00000403
     13: 20020009 gcall t9 3 t14 d4
     14: 000E0003
     15: 00000404
     16: 20020006 gcall t6 5 t10 t9
     17: 000A0005
     18: 00000009
     19: 2001000D gcall t13 4 t6
     20: 00060004
     21: 1000000D end t13
     22: 10000000 end nil
  instruction count:
     10
  #<sys:vm-desc: 9966330>

I see this is doing something silly: (subtypep (typeof x) y) is just (typep x y), but costs an extra gcall instruction.

Either the pattern matcher should do this, or the compiler should have that as an algebraic reduction, or both.

Let's do the compiler for fun:

  $ git diff stdlib
  diff --git a/stdlib/compiler.tl b/stdlib/compiler.tl
  index 58685741..a837571e 100644
  --- a/stdlib/compiler.tl
  +++ b/stdlib/compiler.tl
  @@ -1411,6 +1411,8 @@ (defmeth compiler comp-fun-form (me oreg env form)
              (set form (rlcp ^(,bin ,a ,b) form)))
             ((- @a)
              (set form (rlcp ^(neg ,a) form)))
  +          ((subtypep (typeof @a) @b)
  +           (set form (rlcp ^(typep ,a ,b) form)))
             ((@(or ignore nilf) . @args)
              (if (eql sym 'ignore)
                (each ((a args))

Note that we are using pattern matching here to recognize and rewrite this case. In return we will obtain better code from pattern matching:

  $ make
  TXR stdlib/compiler.tl -> stdlib/compiler.tlo
  $ ./txr
  This is the TXR Lisp interactive listener of TXR 291.
  Quit with :quit or Ctrl-D on an empty line. Ctrl-X ? for cheatsheet.
  TXR is not a toy, but should be kept within easy reach of children.
  1> (flow '(if-match @(struct point x @x y @y) (new (point 1 2))
              (prinl (+ x y)))
       expand
       prinl
       compile-toplevel
       disassemble)
  (let ((#:g0024 (struct-from-args 'point 1 2)))
    (let* (#:result-0028
           x y)
      (if (if (subtypep (typeof #:g0024)  ;; this hasn't changed, of course
                        'point)
          (let ((#:x0026 (slot #:g0024 'x))
                (#:y0027 (slot #:g0024 'y)))
            (sys:setq x #:x0026)
            (sys:setq y #:y0027)
            (sys:setq #:result-0028
              (prinl (+ x y)))
              t))
        #:result-0028
        ())))
  ** expr-1:1: warning: if-match: no such struct type: point
  ** expr-1:1: warning: new: point does not name a struct type
  data:
      0: point
      1: 1
      2: 2
      3: x
      4: y
  syms:
      0: struct-from-args
      1: typep              ;;; no mention of subtypep here any more!
      2: slot
      3: prinl
      4: sys:b+
  code:
      0: 2003000E gcall t14 0 d0 d1 d2
      1: 04000000
      2: 04020401
      3: 20020002 gcall t2 1 t14 d0
      4: 000E0001
      5: 00000400
      6: 38000014 if t2 20
      7: 00000002
      8: 2002000A gcall t10 2 t14 d3
      9: 000E0002
     10: 00000403
     11: 20020009 gcall t9 2 t14 d4
     12: 000E0002
     13: 00000404
     14: 20020006 gcall t6 4 t10 t9
     15: 000A0004
     16: 00000009
     17: 2001000D gcall t13 3 t6
     18: 00060003
     19: 1000000D end t13
     20: 10000000 end nil
  instruction count:
      9                              ;; down by one
  #<sys:vm-desc: 92c94d0>

Ship it!