Cannot write doc-tests in markdown files

[jyn514]

Currently, it gives this error:

error[E0585]: found a documentation comment that doesn't document anything
 --> /checkout/src/doc/rustdoc/src/what-to-include.md:68:1
  |
7 | /// ```
  | ^^^^^^^
  |
  = help: doc comments must come before what they document, maybe a comment was intended with `//`?

Rustdoc should always run doctests in markdown, since there's no code to document.

Originally posted by @jyn514 in #75778 (comment)

[GuillaumeGomez]

I tested with:

# hello

This is test time!

```rust
let x = 12;
```

And ran it without issues:

$ rustdoc --test foo.md 

running 1 test
test foo.md - hello (line 5) ... ok

test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out

[steveklabnik]

That's something different though; this is about doc tests inside of code blocks in markdown files.

@jyn514 it's not clear from your post; the error here is about not having an item to document. If you create one, does it properly do this, or not?

[GuillaumeGomez]

Just like @steveklabnik pointed out, a bit more context would be welcome. :)

[jyn514]

Hmm, I can no longer reproduce this. @AndyGauge do you happen to have a copy of the code that caused this failure? The error message in e9e5b2a#r475234292 doesn't match up with the code you have.

[GuillaumeGomez]

We didn't hear from @AndyGauge since then so I'll close this until we have more information.