getDeclaration

pub fn getDeclaration(zir: Zir, inst: Zir.Inst.Index) Inst.Declaration.Unwrapped {
    assert(zir.instructions.items(.tag)[@backingInt(inst)] == .declaration);
    const pl_node = zir.instructions.items(.data)[@backingInt(inst)].declaration;
    const extra = zir.extraData(Inst.Declaration, pl_node.payload_index);

    const flags_vals: [2]u32 = .{ extra.data.flags_0, extra.data.flags_1 };
    const flags: Inst.Declaration.Flags = @bitCast(flags_vals);

    var extra_index = extra.end;

    const name: NullTerminatedString = if (flags.id.hasName()) name: {
        const name = zir.extra[extra_index];
        extra_index += 1;
        break :name @fromBackingInt(@intCast(name));
    } else .empty;

    const lib_name: NullTerminatedString = if (flags.id.hasLibName()) lib_name: {
        const lib_name = zir.extra[extra_index];
        extra_index += 1;
        break :lib_name @fromBackingInt(@intCast(lib_name));
    } else .empty;

    const type_body_len: u32 = if (flags.id.hasTypeBody()) len: {
        const len = zir.extra[extra_index];
        extra_index += 1;
        break :len len;
    } else 0;
    const align_body_len: u32, const linksection_body_len: u32, const addrspace_body_len: u32 = lens: {
        if (!flags.id.hasSpecialBodies()) break :lens .{ 0, 0, 0 };
        const lens = zir.extra[extra_index..][0..3].*;
        extra_index += 3;
        break :lens lens;
    };
    const value_body_len: u32 = if (flags.id.hasValueBody()) len: {
        const len = zir.extra[extra_index];
        extra_index += 1;
        break :len len;
    } else 0;

    const type_body = zir.bodySlice(extra_index, type_body_len);
    extra_index += type_body_len;
    const align_body = zir.bodySlice(extra_index, align_body_len);
    extra_index += align_body_len;
    const linksection_body = zir.bodySlice(extra_index, linksection_body_len);
    extra_index += linksection_body_len;
    const addrspace_body = zir.bodySlice(extra_index, addrspace_body_len);
    extra_index += addrspace_body_len;
    const value_body = zir.bodySlice(extra_index, value_body_len);
    extra_index += value_body_len;

    return .{
        .src_node = pl_node.src_node,

        .src_line = flags.src_line,
        .src_column = flags.src_column,

        .kind = flags.id.kind(),
        .name = name,
        .is_pub = flags.id.isPub(),
        .is_threadlocal = flags.id.isThreadlocal(),
        .linkage = flags.id.linkage(),
        .lib_name = lib_name,

        .type_body = if (type_body_len == 0) null else type_body,
        .align_body = if (align_body_len == 0) null else align_body,
        .linksection_body = if (linksection_body_len == 0) null else linksection_body,
        .addrspace_body = if (addrspace_body_len == 0) null else addrspace_body,
        .value_body = if (value_body_len == 0) null else value_body,
    };
}