zig compiler assertion

gistfile1.zig.c

const std  = @import("std");
const warn = std.debug.warn;
const fmt  = std.fmt;
const mem  = std.mem;

var alloc = &std.heap.DirectAllocator.init().allocator;

pub const Expr = union(enum) {
    Literal: Literal,
};

pub const Literal = union(enum) {
    Number: f64,
    Bool: bool,
};

pub fn main() !void {
    const s = try fmt.allocPrint(alloc, "{}", Expr{.Literal=Literal{.Bool=true}});
    warn("{}\n",s);
}

gistfile2.txt

ryzen crafting-interpreters-zig/bugs [master●] » zig build-exe ./main.zig 
zig: /home/cgag/bin/zig/src/codegen.cpp:4721: LLVMOpaqueValue* ir_render_union_tag(CodeGen*, IrExecutable*, IrInstructionUnionTag*): Assertion `union_type->data.unionation.gen_tag_index != SIZE_MAX' failed.
[1]    29563 abort (core dumped)  zig run ./main.zig