use crate::utils::{
- is_normalizable, last_path_segment, match_def_path, paths, snippet, span_lint, span_lint_and_sugg,
+ in_constant, is_normalizable, last_path_segment, match_def_path, paths, snippet, span_lint, span_lint_and_sugg,
span_lint_and_then, sugg,
};
use if_chain::if_chain;
-use rustc_ast::ast;
+use rustc_ast as ast;
use rustc_errors::Applicability;
use rustc_hir::{Expr, ExprKind, GenericArg, Mutability, QPath, TyKind, UnOp};
use rustc_lint::{LateContext, LateLintPass};
-use rustc_middle::ty::{self, Ty};
+use rustc_middle::ty::{self, cast::CastKind, Ty};
use rustc_session::{declare_lint_pass, declare_tool_lint};
+use rustc_span::DUMMY_SP;
+use rustc_typeck::check::{cast::CastCheck, FnCtxt, Inherited};
use std::borrow::Cow;
declare_clippy_lint! {
"transmutes that have the same to and from types or could be a cast/coercion"
}
+// FIXME: Merge this lint with USELESS_TRANSMUTE once that is out of the nursery.
+declare_clippy_lint! {
+ /// **What it does:**Checks for transmutes that could be a pointer cast.
+ ///
+ /// **Why is this bad?** Readability. The code tricks people into thinking that
+ /// something complex is going on.
+ ///
+ /// **Known problems:** None.
+ ///
+ /// **Example:**
+ ///
+ /// ```rust
+ /// # let p: *const [i32] = &[];
+ /// unsafe { std::mem::transmute::<*const [i32], *const [u16]>(p) };
+ /// ```
+ /// Use instead:
+ /// ```rust
+ /// # let p: *const [i32] = &[];
+ /// p as *const [u16];
+ /// ```
+ pub TRANSMUTES_EXPRESSIBLE_AS_PTR_CASTS,
+ complexity,
+ "transmutes that could be a pointer cast"
+}
+
declare_clippy_lint! {
/// **What it does:** Checks for transmutes between a type `T` and `*T`.
///
///
/// **Why is this bad?** This can always be rewritten with `&` and `*`.
///
- /// **Known problems:** None.
+ /// **Known problems:**
+ /// - `mem::transmute` in statics and constants is stable from Rust 1.46.0,
+ /// while dereferencing raw pointer is not stable yet.
+ /// If you need to do this in those places,
+ /// you would have to use `transmute` instead.
///
/// **Example:**
/// ```rust,ignore
"transmute between collections of layout-incompatible types"
}
-declare_clippy_lint! {
- /// **What it does:**
- ///
- /// **Why is this bad?**
- ///
- /// **Known problems:** None.
- ///
- /// **Example:**
- ///
- /// ```rust
- /// // example code where clippy issues a warning
- /// ```
- /// Use instead:
- /// ```rust
- /// // example code which does not raise clippy warning
- /// ```
- pub TRANSMUTES_EXPRESSIBLE_AS_PTR_CASTS,
- complexity,
- "default lint description"
-}
-
declare_lint_pass!(Transmute => [
CROSSPOINTER_TRANSMUTE,
TRANSMUTE_PTR_TO_REF,
if let Some(def_id) = cx.qpath_res(qpath, path_expr.hir_id).opt_def_id();
if match_def_path(cx, def_id, &paths::TRANSMUTE);
then {
+ // Avoid suggesting from/to bits and dereferencing raw pointers in const contexts.
+ // See https://github.com/rust-lang/rust/issues/73736 for progress on making them `const fn`.
+ // And see https://github.com/rust-lang/rust/issues/51911 for dereferencing raw pointers.
+ let const_context = in_constant(cx, e.hir_id);
+
let from_ty = cx.typeck_results().expr_ty(&args[0]);
let to_ty = cx.typeck_results().expr_ty(e);
- match (&from_ty.kind, &to_ty.kind) {
+ match (&from_ty.kind(), &to_ty.kind()) {
_ if from_ty == to_ty => span_lint(
cx,
USELESS_TRANSMUTE,
&format!("transmute from a `{}` to a `char`", from_ty),
|diag| {
let arg = sugg::Sugg::hir(cx, &args[0], "..");
- let arg = if let ty::Int(_) = from_ty.kind {
+ let arg = if let ty::Int(_) = from_ty.kind() {
arg.as_ty(ast::UintTy::U32.name_str())
} else {
arg
},
(ty::Ref(_, ty_from, from_mutbl), ty::Ref(_, ty_to, to_mutbl)) => {
if_chain! {
- if let (&ty::Slice(slice_ty), &ty::Str) = (&ty_from.kind, &ty_to.kind);
- if let ty::Uint(ast::UintTy::U8) = slice_ty.kind;
+ if let (&ty::Slice(slice_ty), &ty::Str) = (&ty_from.kind(), &ty_to.kind());
+ if let ty::Uint(ast::UintTy::U8) = slice_ty.kind();
if from_mutbl == to_mutbl;
then {
let postfix = if *from_mutbl == Mutability::Mut {
Applicability::Unspecified,
);
} else {
- if cx.tcx.erase_regions(&from_ty) != cx.tcx.erase_regions(&to_ty) {
+ if (cx.tcx.erase_regions(&from_ty) != cx.tcx.erase_regions(&to_ty))
+ && !const_context {
span_lint_and_then(
cx,
TRANSMUTE_PTR_TO_PTR,
},
)
},
- (ty::Int(_) | ty::Uint(_), ty::Float(_)) => span_lint_and_then(
+ (ty::Int(_) | ty::Uint(_), ty::Float(_)) if !const_context => span_lint_and_then(
cx,
TRANSMUTE_INT_TO_FLOAT,
e.span,
&format!("transmute from a `{}` to a `{}`", from_ty, to_ty),
|diag| {
let arg = sugg::Sugg::hir(cx, &args[0], "..");
- let arg = if let ty::Int(int_ty) = from_ty.kind {
+ let arg = if let ty::Int(int_ty) = from_ty.kind() {
arg.as_ty(format!(
"u{}",
int_ty.bit_width().map_or_else(|| "size".to_string(), |v| v.to_string())
);
},
),
- (ty::Float(float_ty), ty::Int(_) | ty::Uint(_)) => span_lint_and_then(
+ (ty::Float(float_ty), ty::Int(_) | ty::Uint(_)) if !const_context => span_lint_and_then(
cx,
TRANSMUTE_FLOAT_TO_INT,
e.span,
arg = sugg::Sugg::NonParen(format!("{}.to_bits()", arg.maybe_par()).into());
// cast the result of `to_bits` if `to_ty` is signed
- arg = if let ty::Int(int_ty) = to_ty.kind {
+ arg = if let ty::Int(int_ty) = to_ty.kind() {
arg.as_ty(int_ty.name_str().to_string())
} else {
arg
);
}
},
- _ => return,
+ (_, _) if can_be_expressed_as_pointer_cast(cx, e, from_ty, to_ty) => span_lint_and_then(
+ cx,
+ TRANSMUTES_EXPRESSIBLE_AS_PTR_CASTS,
+ e.span,
+ &format!(
+ "transmute from `{}` to `{}` which could be expressed as a pointer cast instead",
+ from_ty,
+ to_ty
+ ),
+ |diag| {
+ if let Some(arg) = sugg::Sugg::hir_opt(cx, &args[0]) {
+ let sugg = arg.as_ty(&to_ty.to_string()).to_string();
+ diag.span_suggestion(e.span, "try", sugg, Applicability::MachineApplicable);
+ }
+ }
+ ),
+ _ => {
+ return;
+ },
}
}
}
false
}
}
+
+/// Check if the type conversion can be expressed as a pointer cast, instead of
+/// a transmute. In certain cases, including some invalid casts from array
+/// references to pointers, this may cause additional errors to be emitted and/or
+/// ICE error messages. This function will panic if that occurs.
+fn can_be_expressed_as_pointer_cast<'tcx>(
+ cx: &LateContext<'tcx>,
+ e: &'tcx Expr<'_>,
+ from_ty: Ty<'tcx>,
+ to_ty: Ty<'tcx>,
+) -> bool {
+ use CastKind::{AddrPtrCast, ArrayPtrCast, FnPtrAddrCast, FnPtrPtrCast, PtrAddrCast, PtrPtrCast};
+ matches!(
+ check_cast(cx, e, from_ty, to_ty),
+ Some(PtrPtrCast | PtrAddrCast | AddrPtrCast | ArrayPtrCast | FnPtrPtrCast | FnPtrAddrCast)
+ )
+}
+
+/// If a cast from `from_ty` to `to_ty` is valid, returns an Ok containing the kind of
+/// the cast. In certain cases, including some invalid casts from array references
+/// to pointers, this may cause additional errors to be emitted and/or ICE error
+/// messages. This function will panic if that occurs.
+fn check_cast<'tcx>(cx: &LateContext<'tcx>, e: &'tcx Expr<'_>, from_ty: Ty<'tcx>, to_ty: Ty<'tcx>) -> Option<CastKind> {
+ let hir_id = e.hir_id;
+ let local_def_id = hir_id.owner;
+
+ Inherited::build(cx.tcx, local_def_id).enter(|inherited| {
+ let fn_ctxt = FnCtxt::new(&inherited, cx.param_env, hir_id);
+
+ // If we already have errors, we can't be sure we can pointer cast.
+ assert!(
+ !fn_ctxt.errors_reported_since_creation(),
+ "Newly created FnCtxt contained errors"
+ );
+
+ if let Ok(check) = CastCheck::new(
+ &fn_ctxt, e, from_ty, to_ty,
+ // We won't show any error to the user, so we don't care what the span is here.
+ DUMMY_SP, DUMMY_SP,
+ ) {
+ let res = check.do_check(&fn_ctxt);
+
+ // do_check's documentation says that it might return Ok and create
+ // errors in the fcx instead of returing Err in some cases. Those cases
+ // should be filtered out before getting here.
+ assert!(
+ !fn_ctxt.errors_reported_since_creation(),
+ "`fn_ctxt` contained errors after cast check!"
+ );
+
+ res.ok()
+ } else {
+ None
+ }
+ })
+}
projects / rust.git / blobdiff