a[1]
a[1][2, 3][4, 5, 6]
a[b[c[d]]].e[f[g], h[i, j]]

a(1)[2]
a(1)[2] { 3 }
a(1) { 2 }[3]
a(1) { 2 }[3] { 4 }

(1 + 2)[3]

foo[:bar] # a

#0
foo[
  #1
  # 2
  a, # 3
  # 4
  b, # 5
  # 6
] # 7
# 8

foo(
  a, # 1
  b, # 2
)[
  # 3
  c, # 4
  # 5
][
  d, # 6
] { |e|
  # y
}

a[1] = 2
a[0, 1] = 2
a[0, b[1], foo(2).bar?, *c, {}] = d
a[&b] = nil
a[1, 2, &b] = nil

a[
  # 1
  true, # 2
  # 3
] =
  # 4
  false # 5

a[
  a, # 1
  b, # 2
  &c # 3
] = d

v = nil
v[] = 1
v[2, 3] = 4

foo(
  a[1] = 2, # 2
  3,
)

foo.bar(1, 2)[1] = 2

foo.bar(
  # 1
  1,
  2,
)[1] = 2

[1].map { |n| n.abs }[0] = 1

[
  1, # 1
][2].foo(3)[4] { 5 }

foo.bar = 1
foo(1, 2)[3].bar(4).baz = 5, 6

a.[] # a
a.[](1, 2)
a.[] 1, 2
a.[][]
a.[](1, 2)[]

a.[]= # a
a.[]=(1, 2)
a.[]= 1, 2

# syntax error: a.[1], a.[1]=