missing peer type resolution: `[:s]const T` and `[]T`

[andrewrk]

/home/andy/Downloads/zig/src/Sema.zig:28870:28: error: incompatible types: '[:0]const u8' and '[]u8'
        const field_name = if (anon_struct.names.len != 0)
                           ^~
/home/andy/Downloads/zig/src/Sema.zig:28871:42: note: type '[:0]const u8' here
            mod.intern_pool.stringToSlice(anon_struct.names[field_i])
            ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/andy/Downloads/zig/src/Sema.zig:28873:13: note: type '[]u8' here
            try std.fmt.allocPrint(sema.arena, "{d}", .{field_i});
            ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Reduction:

const std = @import("std");
const assert = std.debug.assert;
const expect = std.testing.expect;

test "peer type resolution with const sentinel slice and mutable slice" {
    var buf: [4]u8 = "blah".*;
    var a: [:0]const u8 = "hello";
    var b: []u8 = &buf;
    var t = true;
    const result1 = if (t) a else b;
    const result2 = if (!t) a else b;
    comptime assert(@TypeOf(result1) == []const u8);
    comptime assert(@TypeOf(result2) == []const u8);
    try expect(std.mem.eql(u8, a, "hello"));
    try expect(std.mem.eql(u8, b, "blah"));
}

test3.zig:10:21: error: incompatible types: '[:0]const u8' and '[]u8'
    const result1 = if (t) a else b;
                    ^~~~~~~~~~~~~~~
test3.zig:10:28: note: type '[:0]const u8' here
    const result1 = if (t) a else b;
                           ^
test3.zig:10:35: note: type '[]u8' here
    const result1 = if (t) a else b;
                                  ^

I will be opening a pull request for this in a few minutes.

[mlugg]

I will be opening a pull request for this in a few minutes.

I'm probably under 24 hours away from PRing a full rewrite of peer type resolution which should fix this issue and many others 😅

Feck. Well, I'll go ahead and still open mine