Optimize array! DSL (Round 2)

[moberegger]

Follow up to #14. This adopts some of the block param changes from #15.

Benchmarks below to just test the array! DSL both with and without a block in a manner that avoids diluting the change is much as possible.

---

json.array!

ruby 3.4.4 (2025-05-14 revision a38531fd3f) +YJIT +PRISM [arm64-darwin24]
Warming up --------------------------------------
              before   695.095k i/100ms
               after   916.521k i/100ms
Calculating -------------------------------------
              before      8.361M (± 2.2%) i/s  (119.61 ns/i) -     42.401M in   5.074102s
               after     12.024M (± 1.5%) i/s   (83.16 ns/i) -     60.490M in   5.031704s

Comparison:
               after: 12024496.6 i/s
              before:  8360774.5 i/s - 1.44x  slower

Calculating -------------------------------------
              before    40.000  memsize (     0.000  retained)
                         1.000  objects (     0.000  retained)
                         0.000  strings (     0.000  retained)
               after    40.000  memsize (     0.000  retained)
                         1.000  objects (     0.000  retained)
                         0.000  strings (     0.000  retained)

Comparison:
              before:         40 allocated
               after:         40 allocated - same

---

# Where array = [1, 2, 3]
json.array! array do |item|
end

ruby 3.4.4 (2025-05-14 revision a38531fd3f) +YJIT +PRISM [arm64-darwin24]
Warming up --------------------------------------
              before   307.043k i/100ms
               after   345.351k i/100ms
Calculating -------------------------------------
              before      3.309M (± 1.6%) i/s  (302.20 ns/i) -     16.580M in   5.011739s
               after      3.761M (± 3.6%) i/s  (265.90 ns/i) -     18.994M in   5.058330s

Comparison:
               after:  3760855.9 i/s
              before:  3309112.8 i/s - 1.14x  slower

Calculating -------------------------------------
              before   160.000  memsize (    40.000  retained)
                         4.000  objects (     1.000  retained)
                         0.000  strings (     0.000  retained)
               after   160.000  memsize (    40.000  retained)
                         4.000  objects (     1.000  retained)
                         0.000  strings (     0.000  retained)

Comparison:
              before:        160 allocated
               after:        160 allocated - same

---

json.array! posts, partial: "post", as: :post

ruby 3.4.4 (2025-05-14 revision a38531fd3f) +YJIT +PRISM [arm64-darwin24]
Warming up --------------------------------------
              before     1.303k i/100ms
               after     1.595k i/100ms
Calculating -------------------------------------
              before      4.748k (±34.2%) i/s  (210.60 μs/i) -     22.151k in   5.104390s
               after      4.729k (±42.3%) i/s  (211.47 μs/i) -     20.735k in   5.110369s

Comparison:
              before:     4748.2 i/s
               after:     4728.7 i/s - same-ish: difference falls within error

Calculating -------------------------------------
              before     5.952k memsize (   560.000  retained)
                        80.000  objects (     5.000  retained)
                        15.000  strings (     0.000  retained)
               after     5.952k memsize (   560.000  retained)
                        80.000  objects (     5.000  retained)
                        15.000  strings (     0.000  retained)

Comparison:
              before:       5952 allocated
               after:       5952 allocated - same

[moberegger]

Oh, I should also add a benchmark for array! partial:...