#![deny(missing_docs)] incompatible with #[clap(flatten)]

[jared-mackey]

Code

use clap::Clap;

/// Docs included
#[derive(Clap)]
#[clap(author, version)]
struct Opts {
    /// Document debug
    #[clap(short, long)]
    debug: bool,

    /// Flatten
    #[clap(flatten)]
    thing: ThingConfig,

}

/// Thing CLI Configuration
#[derive(Clap)]
#[clap(name = "thing")]
struct ThingConfig {
    /// Thing URI
    #[clap(long)]
    uri: String,
}

Steps to reproduce the issue

1. Run cargo build
2. ???
3. PROFIT!!!

Version

• Rust: rustc 1.47.0-nightly (de521cbb3 2020-08-21)

• Clap: "3.0.0-beta.1"

Actual Behavior Summary

When compiling with a doc on the flattened thing: ThingConfig

error: methods and doc comments are not allowed for flattened entry
  --> src/clapped.rs
   |
45 |     #[clap(flatten)]
   |            ^^^^^^^

When compiling without it (since I can't)

error: missing documentation for the crate

Expected Behavior Summary

Flattened options should not raise a missing docs warning.

[CreepySkeleton]

I have recently fixed this in structopt but forgot to port the fix here. Will do ASAP