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update const_err description

This commit is contained in:
Ralf Jung 2021-01-01 18:41:10 +01:00
parent 5be27b7a70
commit 69a997bef2
1 changed files with 7 additions and 26 deletions
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33
compiler/rustc_lint_defs/src/builtin.rs
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@ -238,41 +238,22 @@ declare_lint! {
///
/// ```rust,compile_fail
/// #![allow(unconditional_panic)]
/// let x: &'static i32 = &(1 / 0);
/// const C: i32 = 1/0;
/// ```
///
/// {{produces}}
///
/// ### Explanation
///
/// This lint detects code that is very likely incorrect. If this lint is
/// allowed, then the code will not be evaluated at compile-time, and
/// instead continue to generate code to evaluate at runtime, which may
/// panic during runtime.
/// This lint detects constants that fail to evaluate. Allowing the lint will accept the
/// constant declaration, but any use of this constant will still lead to a hard error. This is
/// a future incompatibility lint; the plan is to eventually entirely forbid even declaring
/// constants that cannot be evaluated. See [issue #71800] for more details.
///
/// Note that this lint may trigger in either inside or outside of a
/// [const context]. Outside of a [const context], the compiler can
/// sometimes evaluate an expression at compile-time in order to generate
/// more efficient code. As the compiler becomes better at doing this, it
/// needs to decide what to do when it encounters code that it knows for
/// certain will panic or is otherwise incorrect. Making this a hard error
/// would prevent existing code that exhibited this behavior from
/// compiling, breaking backwards-compatibility. However, this is almost
/// certainly incorrect code, so this is a deny-by-default lint. For more
/// details, see [RFC 1229] and [issue #28238].
///
/// Note that there are several other more specific lints associated with
/// compile-time evaluation, such as [`arithmetic_overflow`],
/// [`unconditional_panic`].
///
/// [const context]: https://doc.rust-lang.org/reference/const_eval.html#const-context
/// [RFC 1229]: https://github.com/rust-lang/rfcs/blob/master/text/1229-compile-time-asserts.md
/// [issue #28238]: https://github.com/rust-lang/rust/issues/28238
/// [`arithmetic_overflow`]: deny-by-default.html#arithmetic-overflow
/// [`unconditional_panic`]: deny-by-default.html#unconditional-panic
/// [issue #71800]: https://github.com/rust-lang/rust/issues/71800
pub CONST_ERR,
Deny,
"constant evaluation detected erroneous expression",
"constant evaluation encountered erroneous expression",
report_in_external_macro
}