JRUBY-4039 demonstrates a breakage in JRuby where previously a Ruby
Array used as a List would coerce Fixnum contents only to Long
objects. In 1.4.0RC1, this broke because of a unification of some
coercion logic...the merged logic tried to coerce Fixnum to the
smallest-possible Java numeric type when no target type was specified
(or when the target type was Object). Because the Array started
returning Byte for small Fixnums, a List<Long> reference started to
blow up.
Ignoring the generic stuff for the moment, I have come to the
conclusion that Fixnums should always coerce to Long unless a specific
target type is specified. I have made this change for this bug in
commit 72d49b9 but it required fixing some tests. Specifically, BSF
and coercion tests that expected the narrower types to be coming out.
My justification is as follows: For a given Fixnum n, calling the same
method or coercing to an unknown or general type (like Object) should
produce the same type of object as doing the same operation for n + 1.
The original behavior that coerced to the narrowest type meant that
numeric code iterating over a sequence of numbers might return any of
the numeric Java types, and numeric code counting from 0 to n might
produce any of those types as well. This is unexpected behavior for
almost anyone, and making Fixnum always coerce to long/Long resolves
it.
This change needs to go into 1.4 because it represents a regression.
I'm writing to get input on whether my logic here is sound, or if
there's anything I've overlooked. It was not so bad to fix the BSF
tests, but I had to rewrite an entire example that tested for the
narrower types.
Input desired :)
- Charlie
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