Seemingly valid bit vector indexing yields parse errors

[meheff]

Code is below. Errors and the problematic code are in the comments

# my_lib
pub const W = s32:16;
pub const Z = s32:24;

import my_lib;

pub const A = s32:16;
pub const B = s32:24;

fn foo(x: u32) -> () {
// 0013:   let a = x[my_lib::W : s32:24];
// ~~~~~~~~~~~~~~~~~^------------------^ TypeInferenceError: uN[32] Value to index is not an array.
//  let a = x[my_lib::W : s32:24];

// 0017:   let b = x[my_lib::W : my_lib::Z];
// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~^ ParseError: Old-style cast only permitted for constant arrays/tuples and literal numbers.
//  let b = x[my_lib::W : my_lib::Z];

  // OK.
  let c = x[A:my_lib::Z];

  // OK.
  let d = x[A:B];

  ()
}

[mikex-oss]

Agreed this is confusing, but I guess this is because indices should be raw decimal literals, while constants always have a type?

Sized literals are not ever shown in the documentation:

https://google.github.io/xls/dslx_reference/#bit-slice-examples
https://github.com/google/xls/blob/main/xls/dslx/tests/bit_slice_syntax.x

[meheff]

Agreed this is confusing, but I guess this is because indices should be raw decimal literals, while constants always have a type?

Sized literals are not ever shown in the documentation:

https://google.github.io/xls/dslx_reference/#bit-slice-examples https://github.com/google/xls/blob/main/xls/dslx/tests/bit_slice_syntax.x

Indices using named constants works fine if the constants are locally declared, but not if they are imported (well, at least if the start index is imported). So support is inconsistent.