assignDestructure

fn assignDestructure(gz: *GenZir, scope: *Scope, node: Ast.Node.Index) InnerError!void {
    try emitDbgNode(gz, node);
    const astgen = gz.astgen;
    const tree = astgen.tree;

    const full = tree.assignDestructure(node);
    if (full.comptime_token != null and gz.is_comptime) {
        return astgen.appendErrorTok(full.comptime_token.?, "redundant comptime keyword in already comptime scope", .{});
    }

    // If this expression is marked comptime, we must wrap the whole thing in a comptime block.
    var gz_buf: GenZir = undefined;
    const inner_gz = if (full.comptime_token) |_| bs: {
        gz_buf = gz.makeSubBlock(scope);
        gz_buf.is_comptime = true;
        break :bs &gz_buf;
    } else gz;
    defer if (full.comptime_token) |_| inner_gz.unstack();

    const rl_components = try astgen.arena.alloc(ResultInfo.Loc.DestructureComponent, full.ast.variables.len);
    for (rl_components, full.ast.variables) |*variable_rl, variable_node| {
        if (tree.nodeTag(variable_node) == .identifier) {
            // This intentionally does not support `@"_"` syntax.
            const ident_name = tree.tokenSlice(tree.nodeMainToken(variable_node));
            if (mem.eql(u8, ident_name, "_")) {
                variable_rl.* = .discard;
                continue;
            }
        }
        variable_rl.* = .{ .typed_ptr = .{
            .inst = try lvalExpr(inner_gz, scope, variable_node),
            .src_node = variable_node,
        } };
    }

    const ri: ResultInfo = .{ .rl = .{ .destructure = .{
        .src_node = node,
        .components = rl_components,
    } } };

    _ = try expr(inner_gz, scope, ri, full.ast.value_expr);

    if (full.comptime_token) |_| {
        const comptime_block_inst = try gz.makeBlockInst(.block_comptime, node);
        _ = try inner_gz.addBreak(.break_inline, comptime_block_inst, .void_value);
        try inner_gz.setBlockComptimeBody(comptime_block_inst, .comptime_keyword);
        try gz.instructions.append(gz.astgen.gpa, comptime_block_inst);
    }
}