Add .WHERE, .DEFINITE and .REPR to list of reserved methods

[schultzdavid]

These are three items from the Checklist for 2026.01 (#4758), which were introduced with commits a0a198d, 62927745 and 971b2fa4 respectively. They apply from Rakudo 2026.01 (as is stated in the new text).

Question: Do all three VMs for Rakudo have a moving or compacting garbage collector? I found evidence of this only for MoarVM (here), but am not sure about the particular JVM and JS VM.

Context: The two other files that say something about WHERE explain that its return value may change due to garbage collection:

• doc/Language/mop.rakudoc (website)
• doc/Type/Mu.rakudoc (website)

These files don't need changing because of these commits, but we could take the occasion to make sure that both places tell the complete and correct story.

[schultzdavid]

PR can be merged.

The point about garbage collection is a separate and minor topic.

[schultzdavid]

I think one should also append a warning about using .WHAT & co. together with hyperoperators:

B<Warning:> Using the above-named special methods together with hyperoperators
can lead to unexpected results.
For example, as of Rakudo v2026.02,
C<[1,2,3]».WHAT> gives C<Array> instead of C<[Int, Int, Int]>.
(Calls like C<[1,2,3]».&WHAT> or C<[1,2,3]»."WHAT"()> do give C<[Int,Int, Int]>,
but their behavior is not guaranteed by the test suite.)

Indeed, despite rather extensive searching I did not find any tests of combinations of hyperoperators with WHAT/WHO/HOW/VAR/WHERE/DEFINITE/REPR.

[lizmat]

Please make a rakudo issue for this. [1,2,3]>>.WHAT is being codegenned as [123].WHAT, completely losing the >> aspect.

[schultzdavid]

Rakudo issue created here: rakudo/rakudo#6084 :)