[perl #78406] [BUG] Readonly error on *second iteration* in Rakudo!?

[Will Coleda via RT]

On Sat Oct 16 12:53:02 2010, masak wrote:
> <masak> rakudo: for ^8 { say .fmt("%03b") }
> <p6eval> rakudo 064702: OUTPUT«000␤001␤010␤011␤100␤101␤110␤111␤»
> <masak> rakudo: for ^8 { .=fmt("%03b"); .say }
> <p6eval> rakudo 064702: OUTPUT«000␤Cannot modify readonly value␤  in
> '&infix:<=>' [...]
> <masak> bug or not? why does it die on the second iteration?
> <masak> rakudo: for ^8 -> $_ is copy { .=fmt("%03b"); .say }
> <p6eval> rakudo 064702: OUTPUT«000␤001␤010␤011␤100␤101␤110␤111␤»
> <colomon> could it somehow be checking what the value already was?
> <colomon> rakudo: for ^8 { $_ = 0; .say }
> <p6eval> rakudo 064702: OUTPUT«0␤Cannot modify readonly value␤  in
> '&infix:<=>' [...]
> <colomon> rakudo: for 0, 0, 0 { $_ = 0; .say }
> <p6eval> rakudo 064702: OUTPUT«Cannot modify readonly value␤  in
> '&infix:<=>' [...]
> <colomon> ???????
> <colomon> still have no clue why the bug
> <masak> so you agree it's a bug?
> <colomon> seems like it's got to be, one way or the other.
> * masak submits rakudobug
> <colomon> I mean, either going through the loop the first time is
> wrong, or not going through it the second time is.
> <colomon> unless there's something really subtle and disturbing going 
on.

Now it (properly, I think), dies on the first iteration:

17:05 < [Coke]>   rakudo: for ^8 { .=fmt("%03b"); .say }
17:05 <+p6eval> rakudo 33f1cf: OUTPUT«Cannot assign to a non-container␤  
in
                method dispatch:<.=> at src/gen/CORE.setting:714␤  in 
block
                <anon> at /tmp/fh4hsVBFkr:1␤  in method reify at
                src/gen/CORE.setting:3755␤  in method reify at
                src/gen/CORE.setting:3660␤  in method reify at
                src/gen/CORE.setting:366…


Closable with tests.

-- 
Will "Coke" Coleda