[1.38] Regression: expected one of `!`, `.`, `::`, `;`, `?`, `{`, `}`, or an operator, found `is`

[petrochenkov]

#63628 (comment)

expected one of !, ., ::, ;, ?, {, }, or an operator, found is

./reg/google-games1/1.0.10+20190627/beta-2019-08-13.txt:[INFO] [stdout] error: expected one of `!`, `.`, `::`, `;`, `?`, `{`, `}`, or an operator, found `is`

Minimized reproduction, run with rustdoc --test (all the whitespace is important!):

/// #
///
///     ident ident
fn f() {}

Apparently something makes this comment look like code to rustdoc, so it tries to doctest it.

Actually, stable rustdoc also gives an error for this, from what I tried locally, not sure why it passed on crater.
cc @rust-lang/rustdoc

@shepmaster explains what happens in #63628 (comment).

[GuillaumeGomez]

It's not a bug, it's markdown, litterally. Like @shepmaster wrote, it's considered as a code block.

[Aloso]

@GuillaumeGomez it's a code block, but it's not a doctest, it might not even be Rust syntax.

Doctests can only be written with the

```
```

syntax.

[GuillaumeGomez]

No:

/// # Foo
///
///     let x = 12;
///
/// indeed
///
/// ``````
/// println!("foo");
/// ``````
pub fn foo() {}

Running with rustdoc --test, I had two tests.

[Mark-Simulacrum]

Closing as won't fix / expected breakage.