Self-closing elements spanning multiple lines emit warnings

[Jondolf]

Code

//! The following syntax outputs an error, even though it is a valid SVG!
//! It thinks that `<rect />` is unclosed when it spans multiple lines.
//!
//! <svg width="512" height="512" viewBox="0 0 512" fill="none" xmlns="http://www.w3.org/2000/svg">
//!     <rect
//!         width="256"
//!         height="256"
//!         fill="#5064C8"
//!         stroke="black"
//!     />
//! </svg>
//!
//! However, putting it on a single line works like expected:
//!
//! <svg width="512" height="512" viewBox="0 0 512" fill="none" xmlns="http://www.w3.org/2000/svg">
//!     <rect width="256" height="256" fill="#5064C8" stroke="black" />
//! </svg>
//!
//! "Normal" HTML elements like `<img />` do work like normal, even if they span multiple lines,
//! both with and without an outer div.
//!
//! <div>
//!     <img
//!         src="https://github.com/rust-lang/rust-artwork/blob/master/logo/rust-logo-512x512.png?raw=true"
//!         width="512"
//!         height="512"
//!     />
//! </div>

fn main() {
    println!("Hello, world!");
}

Reproduction Steps

1. Embed an SVG into rustdoc with a self-closing element like <rect /> or <path />, formatted to span multiple lines.
2. Run cargo doc.
3. See the output.

Expected Outcome

No warnings.

Actual Output

$ cargo doc
 Documenting rustdoc_bug v0.1.0 (/home/joona/Programming/rustdoc_bug)
warning: unclosed HTML tag `rect`
 --> src/main.rs:4:9
  |
4 | //!     <rect
  |         ^^^^^
  |
  = note: `#[warn(rustdoc::invalid_html_tags)]` on by default

warning: `rustdoc_bug` (bin "rustdoc_bug" doc) generated 1 warning
    Finished `dev` profile [unoptimized + debuginfo] target(s) in 0.17s
   Generated /home/joona/Programming/rustdoc_bug/target/doc/rustdoc_bug/index.html

Version

rustdoc 1.89.0

Additional Details

It's possible that this applies to any non-HTML elements. In my case, I ran into it with SVGs. I store (small) SVGs in my src directory, and use #[doc = include_str!("path/to/image.svg")] to embed them in docs, but I get warnings unless I force self-closing elements to span only one line.

[lolbinarycat]

<img> is part of ALLOW_UNCLOSED, since it is frequently used as <img> (this is one of the many quirks of html5 that exist in order to make it try to correct errors).

basically, <img> is always treated as self-closing, and rustdoc actually contains a further bug that means it won't even lint on <img