Closes #441.
[Jump to usage instructions](#usage)
##Lints
-There are 73 lints included in this crate:
+There are 74 lints included in this crate:
name | default | meaning
-------------------------------------------------------------------------------------------------------|---------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
[unstable_as_mut_slice](https://github.com/Manishearth/rust-clippy/wiki#unstable_as_mut_slice) | warn | as_mut_slice is not stable and can be replaced by &mut v[..]see https://github.com/rust-lang/rust/issues/27729
[unstable_as_slice](https://github.com/Manishearth/rust-clippy/wiki#unstable_as_slice) | warn | as_slice is not stable and can be replaced by & v[..]see https://github.com/rust-lang/rust/issues/27729
[unused_collect](https://github.com/Manishearth/rust-clippy/wiki#unused_collect) | warn | `collect()`ing an iterator without using the result; this is usually better written as a for loop
+[useless_transmute](https://github.com/Manishearth/rust-clippy/wiki#useless_transmute) | warn | transmutes that have the same to and from types
[while_let_loop](https://github.com/Manishearth/rust-clippy/wiki#while_let_loop) | warn | `loop { if let { ... } else break }` can be written as a `while let` loop
[while_let_on_iterator](https://github.com/Manishearth/rust-clippy/wiki#while_let_on_iterator) | warn | using a while-let loop instead of a for loop on an iterator
[wrong_pub_self_convention](https://github.com/Manishearth/rust-clippy/wiki#wrong_pub_self_convention) | allow | defining a public method named with an established prefix (like "into_") that takes `self` with the wrong convention
pub mod needless_update;
pub mod no_effect;
pub mod temporary_assignment;
+pub mod transmute;
mod reexport {
pub use syntax::ast::{Name, Ident, NodeId};
reg.register_late_lint_pass(box no_effect::NoEffectPass);
reg.register_late_lint_pass(box map_clone::MapClonePass);
reg.register_late_lint_pass(box temporary_assignment::TemporaryAssignmentPass);
+ reg.register_late_lint_pass(box transmute::UselessTransmute);
reg.register_lint_group("clippy_pedantic", vec![
methods::OPTION_UNWRAP_USED,
returns::LET_AND_RETURN,
returns::NEEDLESS_RETURN,
temporary_assignment::TEMPORARY_ASSIGNMENT,
+ transmute::USELESS_TRANSMUTE,
types::BOX_VEC,
types::LET_UNIT_VALUE,
types::LINKEDLIST,
--- /dev/null
+use rustc::lint::*;
+use rustc_front::hir::*;
+use utils;
+
+declare_lint! {
+ pub USELESS_TRANSMUTE,
+ Warn,
+ "transmutes that have the same to and from types"
+}
+
+pub struct UselessTransmute;
+
+impl LintPass for UselessTransmute {
+ fn get_lints(&self) -> LintArray {
+ lint_array!(USELESS_TRANSMUTE)
+ }
+}
+
+impl LateLintPass for UselessTransmute {
+ fn check_expr(&mut self, cx: &LateContext, e: &Expr) {
+ if let ExprCall(ref path_expr, ref args) = e.node {
+ if let ExprPath(None, _) = path_expr.node {
+ let def_id = cx.tcx.def_map.borrow()[&path_expr.id].def_id();
+
+ if utils::match_def_path(cx, def_id, &["core", "intrinsics", "transmute"]) {
+ let from_ty = cx.tcx.expr_ty(&args[0]);
+ let to_ty = cx.tcx.expr_ty(e);
+
+ if from_ty == to_ty {
+ cx.span_lint(USELESS_TRANSMUTE, e.span,
+ &format!("transmute from a type (`{}`) to itself", from_ty));
+ }
+ }
+ }
+ }
+ }
+}
--- /dev/null
+#![feature(core)]
+#![feature(plugin)]
+#![plugin(clippy)]
+#![deny(useless_transmute)]
+
+extern crate core;
+
+use std::mem::transmute as my_transmute;
+use std::vec::Vec as MyVec;
+
+fn my_vec() -> MyVec<i32> {
+ vec![]
+}
+
+#[allow(needless_lifetimes)]
+unsafe fn _generic<'a, T, U: 'a>(t: &'a T) {
+ let _: &'a T = core::intrinsics::transmute(t);
+ //~^ ERROR transmute from a type (`&'a T`) to itself
+
+ let _: &'a U = core::intrinsics::transmute(t);
+}
+
+fn main() {
+ unsafe {
+ let _: Vec<i32> = core::intrinsics::transmute(my_vec());
+ //~^ ERROR transmute from a type (`collections::vec::Vec<i32>`) to itself
+
+ let _: Vec<i32> = core::mem::transmute(my_vec());
+ //~^ ERROR transmute from a type (`collections::vec::Vec<i32>`) to itself
+
+ let _: Vec<i32> = std::intrinsics::transmute(my_vec());
+ //~^ ERROR transmute from a type (`collections::vec::Vec<i32>`) to itself
+
+ let _: Vec<i32> = std::mem::transmute(my_vec());
+ //~^ ERROR transmute from a type (`collections::vec::Vec<i32>`) to itself
+
+ let _: Vec<i32> = my_transmute(my_vec());
+ //~^ ERROR transmute from a type (`collections::vec::Vec<i32>`) to itself
+
+ let _: Vec<u32> = core::intrinsics::transmute(my_vec());
+ let _: Vec<u32> = core::mem::transmute(my_vec());
+ let _: Vec<u32> = std::intrinsics::transmute(my_vec());
+ let _: Vec<u32> = std::mem::transmute(my_vec());
+ let _: Vec<u32> = my_transmute(my_vec());
+ }
+}