Doc test accepts semicolon struct definition with braces

[rasmuspeders1]

This doc test code compiles fine even though the code would not be accepted normally. Notice the semicolon in struct Example{}; this semicolon is not allowed in the actual code but is accepted in the doc example.

/// # Example
/// ```
/// struct Example{};
/// ```
struct Example{}

I would have expected a compile error when running the cargo test command.

Instead it compiles and runs the doc example without problems.

Meta

rustc --version --verbose:

rustc 1.72.0-nightly (839e9a6e1 2023-07-02)
binary: rustc
commit-hash: 839e9a6e1210934fd24b15548b811a97c77138fc
commit-date: 2023-07-02
host: x86_64-unknown-linux-gnu
release: 1.72.0-nightly
LLVM version: 16.0.5

[rasmuspeders1]

Sorry if this is a potential duplicate or if this is expected behavior.
I found issue #91398 which indicates that rust doc did indeed handle this as I would expect at some point earlier.

[lukas-code]

I think this is expected behavior. Because the doctest contains no main function, it gets wrapped in an implicit main function and this is perfectly valid rust code:

fn main() {
    struct Example{};
}

It's an item statement, followed by an empty statement.

The issue you linked fails to compile, because its doctest does contain a main function and is therefore not wrapped in another main function.

Sources:

• The Rust Reference on Statements
• The rustdoc book on pre-processing examples

[rasmuspeders1]

I see now. Thanks.
I was expecting to be able to rely on the doc test code always compiling if copy pasted and compiled as a standalone program.
I can see how I cannot always rely on this and how it is not something that can(or maybe even should) be fixed easily.

[jyn514]

i'm going to close this since it's not a bug.