Quality of life, misleading error messages when extracting values from a slice of a pointer (from vectors and slices)

[joshring]

import std::io;


macro transpose4x4_mat(a, b, c, d)
{
    Matrix4x4{float} mat;
   
    mat.m[0..3] = *a[..];
    mat.m[4..7] = *b[..];
    mat.m[8..11] = *c[..];
    mat.m[12..15] = *d[..];
    
    mat = mat.transpose();
    
    *a = mat.m[0..3];
    *b = mat.m[4..7];
    *c = mat.m[8..11];
    *d = mat.m[12..15];
}

fn void main() 
{
    float[<4>] a = { 0,1,2,3 };
    float[<4>] b = { 4,5,6,7 };
    float[<4>] c = { 8,9,10,11 };
    float[<4>] d = { 12,13,14,15 };
    
    transpose4x4_mat(&a, &b, &c, &d);
    
    io::printn(a);
    io::printn(b);
    io::printn(c);
    io::printn(d);
}

mat.m[0..3] = *a[..];
^^
(/home/josh/git/pffft_c3/src/pffft.c3:96:22) Error: Omitting end index is not allowed for pointers or flexible array members.

so then you think, ok i'll add the end index:

mat.m[0..3] = *a[..3];
^^^^^^
(/home/josh/git/pffft_c3/src/pffft.c3:96:20) Error: Cannot dereference a value of type 'float[<4>][]', it must be a pointer.

this is super confusing, the actual solutions are either:

mat.m[0..3] = (*a)[..];
// or
mat.m[0..3] = a.[..];

but neither of these solutions are mentioned in the error messages

This applies to both vectors and slices as input to this macro

[lerno]

This should be better now. Please test it!

[joshring]

It's better, but could perhaps give an example:

Omitting the end index is not allowed for pointers, did you perhaps forget to dereference the pointer before slicing wih []? eg (*ptr)[..]

because in the code I was dereferencing it, it was complaining because I forgot the brackets around the dereference