id	summary	reporter	owner	description	type	status	priority	milestone	component	version	severity	resolution	keywords	cc	lang	patch	platform
1253	[BUG] hash iterator interface changed, needs errata or deprecation notice	pmichaud		"The following code worked in Parrot 1.0.0 (r37535) and Parrot 1.3.0 (r39599):

{{{
$ cat hash-1.pir
.sub 'main'
    .local pmc hash, hash_it
    hash = new ['Hash']
    hash['1'] = 'a' 
    hash['2'] = 'b'
    hash['3'] = 'c'

    hash_it = iter hash
  loop:
    unless hash_it goto done
    $P0 = shift hash_it
    $P1 = concat $P0, 'x'
    say $P1
    goto loop
  done:
.end

$ 37535/parrot hash-1.pir
1x
2x
3x
$ 39599/parrot hash-1.pir
1x
2x
3x
}}}

The same code fails in 1.4.0 (r40185) and current trunk:

{{{
$ 40185/parrot hash-1.pir
Multiple Dispatch: No suitable candidate found for 'concatenate_str', with signature 'PSP->P'
current instr.: 'main' pc 24 (hash-1.pir:12)
$ trunk/parrot hash-1.pir
Multiple Dispatch: No suitable candidate found for 'concatenate_str', with signature 'PSP->P'
current instr.: 'main' pc 24 (hash-1.pir:13)
$ 
}}}

The problem is not limited to the concat opcode -- other opcodes cause problems also:

{{{
$ cat hash-2.pir
.sub 'main'
    .local pmc hash, hash_it
    hash = new ['Hash']
    hash['1'] = 'a' 
    hash['2'] = 'b'
    hash['3'] = 'c'

    hash_it = iter hash
  loop:
    unless hash_it goto done
    $P0 = shift hash_it
    $P1 = add $P0, 100
    say $P1
    goto loop
  done:
.end

$ 37535/parrot hash-2.pir
101
102
103
$ 39599/parrot hash-2.pir
101
102
103
$ 40185/parrot hash-2.pir
Multiple Dispatch: No suitable candidate found for 'add_int', with signature 'PIP->P'
current instr.: 'main' pc 24 (hash-2.pir:12)
$ trunk/parrot hash-2.pir
Multiple Dispatch: No suitable candidate found for 'add_int', with signature 'PIP->P'
current instr.: 'main' pc 24 (hash-2.pir:13)
$ 
}}}

The underlying problem appears to be that starting with the 1.4.0 release, hash iterators began returning HashIteratorKey PMCs instead of String PMCs:

{{{
$ cat hash-3.pir
.sub 'main'
    .local pmc hash, hash_it
    hash = new ['Hash']
    hash['1'] = 'a' 
    hash['2'] = 'b'
    hash['3'] = 'c'

    hash_it = iter hash
  loop:
    unless hash_it goto done
    $P0 = shift hash_it
    $P1 = typeof $P0
    say $P1
    goto loop
  done:
.end

$ 37535/parrot hash-3.pir
String
String
String
$ 39599/parrot hash-3.pir
String
String
String
$ 40185/parrot hash-3.pir
HashIteratorKey
HashIteratorKey
HashIteratorKey
$ trunk/parrot hash-3.pir
HashIteratorKey
HashIteratorKey
HashIteratorKey
$ 
}}}

It seems to me that a change of this sort should have been preceded by a deprecation notice -- as far as I can tell no such notice was given.  Regardless, returning a HashIteratorKey PMC would seem to be the least usable or useful of any of the options available.

Pm"	bug	new	normal		core	1.7.0	release			whiteknight allison