Clippy lints / Nursery
Clippy lint · Nursery · checked with Clippy 0.1.99
clippy::uninhabited_references: dereferencing a reference to an uninhabited type would be undefined behavior
What it meansIt detects references to uninhabited types, such as ! and warns when those are either dereferenced or returned from a function. It is in the nursery group and off by default.
What you see
warning: dereferencing a reference to an uninhabited type would be undefined behavior --> main.rs:3:20 | 3 | fn create_ref() -> &'static std::convert::Infallible { | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ | = help: for further information visit https://rust-lang.github.io/rust-clippy/stable/index.html#uninhabited_references = note: `-W clippy::uninhabited-references` implied by `-W clippy::nursery`
Real output of Clippy 0.1.99 (Rust 1.99) on the example below. Names and line numbers in yours will differ.
Does it matter?
Dereferencing a reference to an uninhabited type would create an instance of such a type, which cannot exist. This constitutes undefined behaviour. Such a reference could have been created by unsafe code.
New lints still being finished. Off by default and may have false positives.
How to fix it
Clippy does not fix this one automatically. Change the code by hand:
Flagged
fn create_ref() -> &'static std::convert::Infallible {
unsafe { std::mem::transmute(&()) }
}
Turn it off, or on
It is off by default. To use it, set it to warn or deny:
Whole crate (Cargo.toml)
[lints.clippy]
uninhabited_references = "warn"In code
#![warn(clippy::uninhabited_references)]One run
cargo clippy -- -W clippy::uninhabited-referencesThe [lints] table needs Rust 1.74 or newer. In a workspace, put it under [workspace.lints.clippy] and add [lints] workspace = true to each member.
Clippy's own documentation
What it does
It detects references to uninhabited types, such as ! and
warns when those are either dereferenced or returned from a function.
Why is this bad?
Dereferencing a reference to an uninhabited type would create
an instance of such a type, which cannot exist. This constitutes
undefined behaviour. Such a reference could have been created
by unsafe code.
Example
The following function can return a reference to an uninhabited type
(Infallible) because it uses unsafe code to create it. However,
the user of such a function could dereference the return value and
trigger an undefined behavior from safe code.
fn create_ref() -> &'static std::convert::Infallible {
unsafe { std::mem::transmute(&()) }
}
From the Clippy lint list (0.1.99), part of the Rust project, MIT or Apache-2.0. Official entry.
Related lints
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- type_repetition_in_boundstype `T` has already been used as a bound predicate
- unnecessary_struct_initializationunnecessary struct building
- unused_peekable`peek` never called on `Peekable` iterator
- unused_roundingused the `ceil` method with a whole number float
All 847 Clippy lints · Rust compiler errors · Cargo.toml checker
Up next
Related lintclippy::redundant_cloneChecks for a redundant clone() (and its relatives) which clones an owned value that is going to be dropped without further useRead it next →Did this answer your question?