Unexpected semilocon makes rustdoc to produce false negatives

[xDarksome]

I tried this code:

/// ```rust
/// struct S {}; // unexpected semicolon after struct def
///
/// fn main() {
///    assert_eq!(0, 1);
/// }
/// ```
mod m {}

cargo test

I expected to see this happen:

running 0 tests

test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00s


running 1 test
test src/lib.rs - m (line 1) ... FAILED

failures:

---- src/lib.rs - m (line 1) stdout ----
error: expected item, found `;`
 --> src/lib.rs:6:12
  |
2 | struct S {};
  |            ^ help: remove this semicolon
  |
  = help: braced struct declarations are not followed by a semicolon

error: aborting due to previous error

Couldn't compile the test.

failures:
    src/lib.rs - m (line 1)

test result: FAILED. 0 passed; 1 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.29s

Instead, this happened:

running 0 tests

test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00s


running 1 test
test src/lib.rs - m (line 1) ... ok

test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 1.06s

Meta

rustc --version --verbose:

binary: rustc
commit-hash: c8dfcfe046a7680554bf4eb612bad840e7631c4b
commit-date: 2021-09-06
host: x86_64-unknown-linux-gnu
release: 1.55.0
LLVM version: 12.0.1

Also, reproduces on playground (1.56.1 / 1.57.0-beta.3 / 1.58.0-nightly)

Putting struct def after the main function makes rustdoc to behave as expected:

/// ```rust
/// fn main() {
///    assert_eq!(0, 1);
/// }
///
/// struct S {}; // unexpected semicolon after struct def
/// ```
mod m {}

Implicit main function does the assertion correctly.

/// ```rust
/// struct S {}; // semicolon is OK here
/// assert_eq!(0, 1);
/// ```
mod m {}