test/statements/assign/indexed_assign_to_array_in_struct/struct_matrix.wgsl

struct Uniforms {
  i : u32;
};

struct OuterS {
  m1 : mat2x4<f32>;
};

[[group(1), binding(4)]] var<uniform> uniforms : Uniforms;

[[stage(compute), workgroup_size(1)]]
fn main() {
  var s1 : OuterS;
  s1.m1[uniforms.i] = vec4<f32>(1.0);
  s1.m1[uniforms.i][uniforms.i] = 1.0;
}