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underscore_literal_suffix future-compatibility warnings #42326
Description
This is the summary issue for the UNDERSCORE_LITERAL_SUFFIX future-compatibility warning and other related errors. The goal of this page is describe why this change was made and how you can fix
code that is affected by it. It also provides a place to ask questions or register a complaint if you feel the change should not be made.
What is the warning for?
The underscore_literal_suffix warning is issued when you use _ as a literal suffix. Due to the behavior of the lexer, this is limited to these two situations:
- After char/string/byte/bytestring literals:
"Foo"_ - After float literals ending with
.:1._(this kind of construction is already banned by means of Disallow ._ in float literal. #41946)
This warning can always be fixed by removing the _ and inserting whitespaces if necessary.
When will this warning become a hard error?
At the beginning of each 6-week release cycle, the Rust compiler team
will review the set of outstanding future compatibility warnings and
nominate some of them for Final Comment Period. Toward the end of
the cycle, we will review any comments and make a final determination
whether to convert the warning into a hard error or remove it
entirely.
Activity
Add warning cycle rust-lang#42326.
steveklabnik commentedon Mar 12, 2019
Triage: it's been a few years, and looks like nobody has visited this issue.
pnkfelix commentedon Mar 18, 2022
Visiting as part of T-compiler backlog bonanza.
This lint appears implemented, perhaps via a
span_warn. I do not yet know if the warning it reports is included as part of acargo report future-incompat; I can look into that later.The current diagnostic output indicates that it is probably not using the usual lint infrastructure (that would enable using
allow/denyetc).Next steps are
cargo report future-incompatoutput, when relevant.@rustbot label: +S-tracking-needs-to-bake
nikomatsakis commentedon Mar 18, 2022
@pnkfelix is this "needs to bake"? It feels like we are ready to take next steps here (running on crater).
Rollup merge of rust-lang#103914 - nnethercote:close-42326, r=petroch…
Rollup merge of rust-lang#103914 - nnethercote:close-42326, r=petroch…