std.ComptimeStringMap gives compile error when giving an empty list

[FanShupei]

Zig Version

0.12.0-dev.1800+559e216f3

Steps to Reproduce and Observed Behavior

When compiling the following code,

const std = @import("std");
pub fn main() void {
    const dict = std.ComptimeStringMap(i32, .{});
    // const dict = std.ComptimeStringMap(i32, .{.{"nothing", 0}});
    std.debug.print("{?}\n", .{dict.get("anything")});
}

it gives the following compile error:

/home/fsp/.zvm/master/lib/std/comptime_string_map.zig:74:35: error: indexing into empty array is not allowed
        const min_len = sorted_kvs[0].key.len;
                        ~~~~~~~~~~^~~
/home/fsp/.zvm/master/lib/std/comptime_string_map.zig:14:36: note: called from here
    return ComptimeStringMapWithEql(V, kvs_list, defaultEql);
           ~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~
1.zig:3:39: note: called from here
    const dict = std.ComptimeStringMap(i32, .{});
                 ~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~
referenced by:
    callMain: /home/fsp/.zvm/master/lib/std/start.zig:575:17
    initEventLoopAndCallMain: /home/fsp/.zvm/master/lib/std/start.zig:519:34
    remaining reference traces hidden; use '-freference-trace' to see all reference traces

I believe the root cause is that ComptimeStringMapWithEql does not handle the special case that the list is empty.

Expected Behavior

When providing an empty list, std.ComptimeStringMap shall behave as an empty dict, instead of generating compile error.

[Rexicon226]

what would be the purpose of an empty comptime string map?
if anything, it should be a compile error to not have anything in the tuple.

[FanShupei]

I'm not thoughtful enough to see the expected behavior itself is controversial, but I insist the current behavior extremely confuses users. The expected behavior may be changed to the following:

Expected Behavior: If an empty list should be supported, it shall be behave as an empty dict. If it's intentionally disallowed, it should give a clear error message and be reflected in documentation.

Personally I think an empty string map should be allowed, for consistency, like Zig already has zero-length tuple and zero-length array. The behavior is intuitive and I haven't see any footgun for it.

I agree that deliberately construct an empty comptime map is quite meaningless. But the feature may be useful in metaproramming.

[xdBronch]

theres actually an unrelated PR open i stumbled across that fixes this #17731. you can see here that it defaults to 0 and will just always return null from the get function if the tuple is empty