Add borrow_as_ptr lint

Closes: rust-lang#6995 Signed-off-by: Federico Guerinoni <guerinoni.federico@gmail.com> Co-authored-by: Paolo Barbolini <paolo@paolo565.org>

Author: 2 people

CHANGELOG.md

@@ -2887,6 +2887,7 @@ Released 2018-09-13
 [`blocks_in_if_conditions`]: https://rust-lang.github.io/rust-clippy/master/index.html#blocks_in_if_conditions
 [`bool_assert_comparison`]: https://rust-lang.github.io/rust-clippy/master/index.html#bool_assert_comparison
 [`bool_comparison`]: https://rust-lang.github.io/rust-clippy/master/index.html#bool_comparison
+[`borrow_as_ptr`]: https://rust-lang.github.io/rust-clippy/master/index.html#borrow_as_ptr
 [`borrow_interior_mutable_const`]: https://rust-lang.github.io/rust-clippy/master/index.html#borrow_interior_mutable_const
 [`borrowed_box`]: https://rust-lang.github.io/rust-clippy/master/index.html#borrowed_box
 [`box_collection`]: https://rust-lang.github.io/rust-clippy/master/index.html#box_collection

README.md

@@ -5,7 +5,7 @@
 
 A collection of lints to catch common mistakes and improve your [Rust](https://github.com/rust-lang/rust) code.
 
-[There are over 450 lints included in this crate!](https://rust-lang.github.io/rust-clippy/master/index.html)
+[There are over 500 lints included in this crate!](https://rust-lang.github.io/rust-clippy/master/index.html)
 
 Lints are divided into categories, each with a default [lint level](https://doc.rust-lang.org/rustc/lints/levels.html).
 You can choose how much Clippy is supposed to ~~annoy~~ help you by changing the lint level by category.

clippy_lints/src/borrow_as_ptr.rs

@@ -0,0 +1,97 @@
+use clippy_utils::diagnostics::span_lint_and_sugg;
+use clippy_utils::is_no_std_crate;
+use clippy_utils::source::snippet_opt;
+use clippy_utils::{meets_msrv, msrvs};
+use if_chain::if_chain;
+use rustc_errors::Applicability;
+use rustc_hir::{BorrowKind, Expr, ExprKind, Mutability, TyKind};
+use rustc_lint::{LateContext, LateLintPass};
+use rustc_semver::RustcVersion;
+use rustc_session::{declare_tool_lint, impl_lint_pass};
+
+declare_clippy_lint! {
+ /// ### What it does
+ /// Checks for the usage of `&expr as *const T` or
+ /// `&mut expr as *mut T`, and suggest using `ptr::addr_of` or
+ /// `ptr::addr_of_mut` instead.
+ ///
+ /// ### Why is this bad?
+ /// This would improve readability and avoid creating a reference
+ /// that points to an uninitialized value or unaligned place.
+ /// Read the `ptr::addr_of` docs for more information.
+ ///
+ /// ### Example
+ /// ```rust
+ /// let val = 1;
+ /// let p = &val as *const i32;
+ ///
+ /// let mut val_mut = 1;
+ /// let p_mut = &mut val_mut as *mut i32;
+ /// ```
+ /// Use instead:
+ /// ```rust
+ /// let val = 1;
+ /// let p = std::ptr::addr_of!(val);
+ ///
+ /// let mut val_mut = 1;
+ /// let p_mut = std::ptr::addr_of_mut!(val_mut);
+ /// ```
+ #[clippy::version = "1.60.0"]
+ pub BORROW_AS_PTR,
+ pedantic,
+ "borrowing just to cast to a raw pointer"
+}
+
+impl_lint_pass!(BorrowAsPtr => [BORROW_AS_PTR]);
+
+pub struct BorrowAsPtr {
+ msrv: Option<RustcVersion>,
+}
+
+impl BorrowAsPtr {
+ #[must_use]
+ pub fn new(msrv: Option<RustcVersion>) -> Self {
+ Self { msrv }
+ }
+}
+
+impl<'tcx> LateLintPass<'tcx> for BorrowAsPtr {
+ fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
+ if !meets_msrv(self.msrv.as_ref(), &msrvs::BORROW_AS_PTR) {
+ return;
+ }
+
+ if expr.span.from_expansion() {
+ return;
+ }
+
+ if_chain! {
+ if let ExprKind::Cast(left_expr, ty) = &expr.kind;
+ if let TyKind::Ptr(_) = ty.kind;
+ if let ExprKind::AddrOf(BorrowKind::Ref, mutability, e) = &left_expr.kind;
+
+ then {
+ let core_or_std = if is_no_std_crate(cx) { "core" } else { "std" };
+ let macro_name = match mutability {
+ Mutability::Not => "addr_of",
+ Mutability::Mut => "addr_of_mut",
+ };
+
+ span_lint_and_sugg(
+ cx,
+ BORROW_AS_PTR,
+ expr.span,
+ "borrow as raw pointer",
+ "try",
+ format!(
+ "{}::ptr::{}!({})",
+ core_or_std,
+ macro_name,
+ snippet_opt(cx, e.span).unwrap()
+ ),
+ Applicability::MachineApplicable,
+ );
+ }
+ }
+ }
+}

clippy_lints/src/lib.register_lints.rs

@@ -59,6 +59,7 @@ store.register_lints(&[
  bool_assert_comparison::BOOL_ASSERT_COMPARISON,
  booleans::LOGIC_BUG,
  booleans::NONMINIMAL_BOOL,
+ borrow_as_ptr::BORROW_AS_PTR,
  bytecount::NAIVE_BYTECOUNT,
  cargo_common_metadata::CARGO_COMMON_METADATA,
  case_sensitive_file_extension_comparisons::CASE_SENSITIVE_FILE_EXTENSION_COMPARISONS,

clippy_lints/src/lib.register_pedantic.rs

@@ -7,6 +7,7 @@ store.register_group(true, "clippy::pedantic", Some("clippy_pedantic"), vec![
  LintId::of(await_holding_invalid::AWAIT_HOLDING_LOCK),
  LintId::of(await_holding_invalid::AWAIT_HOLDING_REFCELL_REF),
  LintId::of(bit_mask::VERBOSE_BIT_MASK),
+ LintId::of(borrow_as_ptr::BORROW_AS_PTR),
  LintId::of(bytecount::NAIVE_BYTECOUNT),
  LintId::of(case_sensitive_file_extension_comparisons::CASE_SENSITIVE_FILE_EXTENSION_COMPARISONS),
  LintId::of(casts::CAST_LOSSLESS),

clippy_lints/src/lib.rs

@@ -174,6 +174,7 @@ mod blacklisted_name;
 mod blocks_in_if_conditions;
 mod bool_assert_comparison;
 mod booleans;
+mod borrow_as_ptr;
 mod bytecount;
 mod cargo_common_metadata;
 mod case_sensitive_file_extension_comparisons;
@@ -857,6 +858,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
  store.register_late_pass(|| Box::new(return_self_not_must_use::ReturnSelfNotMustUse));
  store.register_late_pass(|| Box::new(init_numbered_fields::NumberedFields));
  store.register_early_pass(|| Box::new(single_char_lifetime_names::SingleCharLifetimeNames));
+ store.register_late_pass(move || Box::new(borrow_as_ptr::BorrowAsPtr::new(msrv)));
  // add lints here, do not remove this comment, it's used in `new_lint`
 }
 

clippy_utils/src/msrvs.rs

@@ -14,6 +14,7 @@ macro_rules! msrv_aliases {
 msrv_aliases! {
  1,53,0 { OR_PATTERNS }
  1,52,0 { STR_SPLIT_ONCE }
+ 1,51,0 { BORROW_AS_PTR }
  1,50,0 { BOOL_THEN }
  1,47,0 { TAU }
  1,46,0 { CONST_IF_MATCH }

tests/ui/as_conversions.rs

@@ -1,6 +1,7 @@
 // aux-build:macro_rules.rs
 
 #![warn(clippy::as_conversions)]
+#![allow(clippy::borrow_as_ptr)]
 
 #[macro_use]
 extern crate macro_rules;

tests/ui/as_conversions.stderr

@@ -1,5 +1,5 @@
 error: using a potentially dangerous silent `as` conversion
- --> $DIR/as_conversions.rs:14:13
+ --> $DIR/as_conversions.rs:15:13
  |
 LL | let i = 0u32 as u64;
  | ^^^^^^^^^^^
@@ -8,15 +8,15 @@ LL | let i = 0u32 as u64;
  = help: consider using a safe wrapper for this conversion
 
 error: using a potentially dangerous silent `as` conversion
- --> $DIR/as_conversions.rs:16:13
+ --> $DIR/as_conversions.rs:17:13
  |
 LL | let j = &i as *const u64 as *mut u64;
  | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  |
  = help: consider using a safe wrapper for this conversion
 
 error: using a potentially dangerous silent `as` conversion
- --> $DIR/as_conversions.rs:16:13
+ --> $DIR/as_conversions.rs:17:13
  |
 LL | let j = &i as *const u64 as *mut u64;
  | ^^^^^^^^^^^^^^^^

tests/ui/borrow_as_ptr.fixed

@@ -0,0 +1,10 @@
+// run-rustfix
+#![warn(clippy::borrow_as_ptr)]
+
+fn main() {
+ let val = 1;
+ let _p = std::ptr::addr_of!(val);
+
+ let mut val_mut = 1;
+ let _p_mut = std::ptr::addr_of_mut!(val_mut);
+}