Static rustc_lint_defs::builtin::IRREFUTABLE_LET_PATTERNS

pub static IRREFUTABLE_LET_PATTERNS: &'static Lint

The irrefutable_let_patterns lint detects irrefutable patterns in if lets, while lets, and if let guards.

Example

if let _ = 123 {
    println!("always runs!");
}

{{produces}}

Explanation

There usually isn’t a reason to have an irrefutable pattern in an if let or while let statement, because the pattern will always match successfully. A let or loop statement will suffice. However, when generating code with a macro, forbidding irrefutable patterns would require awkward workarounds in situations where the macro doesn’t know if the pattern is refutable or not. This lint allows macros to accept this form, while alerting for a possibly incorrect use in normal code.

See RFC 2086 for more details.