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https://doc.rust-lang.org/nightly/std/net/struct.Ipv4Addr.html#method.is_global documents such addresses as not being global, so I expect the doc test to fail.

The job pr-check-2 failed! Check out the build log: (web) (plain enhanced) (plain)

   0: __rustc::rust_begin_unwind
   1: core::panicking::panic_fmt
   2: core::panicking::assert_failed_inner
   3: core::panicking::assert_failed
   4: rust_out::main::_doctest_main_library_core_src_net_ip_addr_rs_291_0
   5: rust_out::main
   6: core::ops::function::FnOnce::call_once
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.

---- library/core/src/net/ip_addr.rs - net::ip_addr::IpAddr::is_global (line 291) stdout end ----

According to https://www.iana.org/assignments/iana-ipv4-special-registry/iana-ipv4-special-registry.xhtml, these special addresses are global:

192.175.48.0/24 	Direct Delegation AS112 Service 	[[RFC7534](https://www.iana.org/go/rfc7534)] 	1996-01 	N/A 	True 	True 	True 	True 	False
192.52.193.0/24 	AMT 	[[RFC7450](https://www.iana.org/go/rfc7450)] 	2014-12 	N/A 	True 	True 	True 	True 	False
192.31.196.0/24 	AS112-v4 	[[RFC7535](https://www.iana.org/go/rfc7535)] 	2014-12 	N/A 	True 	True 	True 	True 	False
192.0.0.10/32 	Traversal Using Relays around NAT Anycast 	[[RFC8155](https://www.iana.org/go/rfc8155)] 	2017-02 	N/A 	True 	True 	True 	True 	False
192.0.0.9/32 	Port Control Protocol Anycast 	[[RFC7723](https://www.iana.org/go/rfc7723)] 	2015-10 	N/A 	True 	True 	True 	True 	False

seems like this is an awkward method to write good docs for in that case...

IPs have a one-hot classification, being a documentation IP means it isn't global https://play.rust-lang.org/?version=nightly&mode=debug&edition=2024&gist=4d02d0c8fe5827b36b87a3b9dbbc0605. Based on the comment from @hkBst this also seems like a correct classification for the two IPs in question here.

seems like this is an awkward method to write good docs for in that case...

What makes the docs incorrect or bad?

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What makes the docs incorrect or bad?

Not incorrect, that is definitely a global IP in the original. My intention with this pull request was to use a global IP reserved for documentation so that some random IP address wasn't being used. I should have done more research before opening this, please forgive me for wasting time.

I am still learning Rust, so while I was reading the docs, I was under the impression that the global IP currently in the docs was a special global IP address that had a certain use case, but when I looked it up, it seems to be an arbitrarily chosen IP for demonstration. I was thinking that using a global IP address that is more general or perhaps reserved for examples would make the documentation for the is_global() method more clear.

Well, it is probably randomly chosen :) They don't really say but I assume IETF5737 is probably meant for documentation where you might actually interact with the IP addresses (like pinging/connecting), and not so much for documenting effectively "this is what x kind of IP could look like". That would make it a bit tough to write IETF docs about anything other than documentation IPs.

I should have done more research before opening this, please forgive me for wasting time.

There is no waste and it's not a problem! New ideas are always welcome, and everybody learns in situations like this.

I am going to close this though, since I don't think it is actionable.

I am still learning Rust, so while I was reading the docs, I was under the impression that the global IP currently in the docs was a special global IP address that had a certain use case, but when I looked it up, it seems to be an arbitrarily chosen IP for demonstration

To address this a bit more directly; most of the IPs in this section of the docs are arbitrary and for demonstration. There are a range of values that match the is_* queries, most of the examples try to choose a couple that look kind of different.