Some sort of compiler bug

Imported from http://bugzilla.roxen.com/bugzilla/show_bug.cgi?id=2767

Reported by Martin Nilsson, IDA nilsson@pike.ida.liu.se

The following code

  mapping basun = ([ "foo":Image.Image(10,10) ]);
  add_constant("basun", basun);
  program p = compile_string("Image.Image i=basun.foo;\n"
    "mixed x() { return basun; }", "-");

gives the following error

-:1:Couldn't store constant.
`==: illegal argument 2
Pike/7.3/build/sunos-5.8-i86pc/test-install/pike/7.3.16/lib/modules/Image.s
o.image:
    Image.Image( 10 x 10 /* 0.3Kb */)->`==(mapping[1])

Pike/7.3/build/sunos-5.8-i86pc/test-install/pike/7.3.16/lib/master.pike:223
:
    master()->compile_string("Image.Image i=basun.foo;\nmixed x() { return
basun; }","-",0)

If however the declaration of i is removed of the return is changed from basun to i it works.