In a language where arrays are fixed-size, I think the proper solution is to have arrays not indexed by integers, but by a custom modular type that depends on the array with values in [0,n) that allows literals in the range [-n, n-1], with literal ‘-1’ being a different way to write ‘n-1’, etc.

You’d need a way to get that type, for example as

  float a[10,20]          // two-dimensional array of floats
  typeof(a.dims(0)) i = 0 // modular type with values in [0,9]
  typeof(a.dims(1)) j = 0 // modular type with values in [0,19]

or, slightly neater:

  auto i = a.indextype(0)
  auto j = a.indextype(1)

Ugly syntax, but in a modern language, most code would probably do something like

  for (i,j,value) in a

where the types are inferred.

Having those modular types means the compiler would do the arithmetic correct for the array, while the negative literals allow programmers to specify “last” and “next to last” correctly.