Document having only src/bin/*.rs binaries is valid

[nekomachi-touge]

Problem

I found the following section of the cargo book could make readers think they must provide src/main.rs.

cargo/src/doc/src/reference/cargo-targets.md

Lines 30 to 34 in 59ecb11

	Binary targets are executable programs that can be run after being compiled.
	The default binary filename is `src/main.rs`, which defaults to the name of
	the package. Additional binaries are stored in the [`src/bin/`
	directory][package layout]. The settings for each binary can be [customized]
	in the `[[bin]]` tables in `Cargo.toml`.

However, it is also valid to have only src/bin/*.rs binaries and not to have src/main.rs.
I believe clarifying this situation on the book will help readers when arranging codes for binaries.

Proposed Solution

Changing the section like below should work:

Binary targets are executable programs that can be run after being compiled. 
The default binary filename is `src/main.rs`, which defaults to the name of 
the package. Additionally one or more binaries are stored in the [`src/bin/`
 directory][package layout]. In this case the default binary `src/main.rs` 
is not required. The settings for each binary can be [customized] in the
`[[bin]]` tables in `Cargo.toml`.

Notes

No response

[epage]

Thanks for providing this feedback on the confusion you had! It looks like the suggested change is the addition of

n this case the default binary src/main.rs is not required.

It feels odd to call out that a default is not required, that is generally the case for a default.

For brainstorming purposes, another approach is something like

Binary targets are executable programs that can be run after being compiled. 
A binary's source can be `src/main.rs` and/or stored in the  [`src/bin/` 
directory][package layout].  For `src/main.rs`, the default binary name is the package name. The settings for each binary can be [customized] 
in the `[[bin]]` tables in `Cargo.toml`. 

[nekomachi-touge]

@epage Thank you for the quick response!

I support your fix.
Using and/or make the section much clearer than my take, and also stating *.rs are sources sounds more natural than the original text.
Maybe we need to make sure the text is wrapped at 80 characters though.

I'm considering making a PR after waiting feedbacks for a couple of days.
Nevermind, I'll wait for the removal of the S-triage tag.

[nekomachi-touge]

Since no one seems to submit another proposal, I’m going to make a PR based on the @epage ‘s text to keep this issue from being stale.