getOpaqueDecl

pub fn getOpaqueDecl(zir: *const Zir, opaque_decl: Inst.Index) UnwrappedOpaqueDecl {
    const inst_data = zir.instructions.get(@backingInt(opaque_decl));
    assert(inst_data.tag == .extended);
    assert(inst_data.data.extended.opcode == .opaque_decl);
    const small: Inst.OpaqueDecl.Small = @bitCast(inst_data.data.extended.small);
    const extra = zir.extraData(Inst.OpaqueDecl, inst_data.data.extended.operand);
    var extra_index = extra.end;
    const captures_len: u32 = if (small.has_captures_len) blk: {
        const captures_len = zir.extra[extra_index];
        extra_index += 1;
        break :blk captures_len;
    } else 0;
    const decls_len: u32 = if (small.has_decls_len) blk: {
        const decls_len = zir.extra[extra_index];
        extra_index += 1;
        break :blk decls_len;
    } else 0;
    const captures: []const Inst.Capture = @ptrCast(zir.extra[extra_index..][0..captures_len]);
    extra_index += captures_len;
    const capture_names: []const NullTerminatedString = @ptrCast(zir.extra[extra_index..][0..captures_len]);
    extra_index += captures_len;
    const decls: []const Inst.Index = @ptrCast(zir.extra[extra_index..][0..decls_len]);
    extra_index += decls_len;
    return .{
        .src_line = extra.data.src_line,
        .src_column = extra.data.src_column,
        .src_node = extra.data.src_node,
        .name_strategy = small.name_strategy,
        .captures = captures,
        .capture_names = capture_names,
        .decls = decls,
    };
}