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`underscore_literal_suffix` future-compatibility warnings #42326

qnighy opened this Issue May 31, 2017 · 0 comments


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qnighy commented May 31, 2017

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 #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

qnighy added a commit to qnighy/rust that referenced this issue May 31, 2017

nagisa added a commit to nagisa/rust that referenced this issue Jun 8, 2017

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