Add borrow_as_ptr lint

Closes: #6995

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

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);
+}

tests/ui/borrow_as_ptr.rs

@@ -0,0 +1,10 @@
+// run-rustfix
+#![warn(clippy::borrow_as_ptr)]
+
+fn main() {
+    let val = 1;
+    let _p = &val as *const i32;
+
+    let mut val_mut = 1;
+    let _p_mut = &mut val_mut as *mut i32;
+}

tests/ui/borrow_as_ptr.stderr

@@ -0,0 +1,16 @@
+error: borrow as raw pointer
+  --> $DIR/borrow_as_ptr.rs:6:14
+   |
+LL |     let _p = &val as *const i32;
+   |              ^^^^^^^^^^^^^^^^^^ help: try: `std::ptr::addr_of!(val)`
+   |
+   = note: `-D clippy::borrow-as-ptr` implied by `-D warnings`
+
+error: borrow as raw pointer
+  --> $DIR/borrow_as_ptr.rs:9:18
+   |
+LL |     let _p_mut = &mut val_mut as *mut i32;
+   |                  ^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `std::ptr::addr_of_mut!(val_mut)`
+
+error: aborting due to 2 previous errors
+

tests/ui/borrow_as_ptr_no_std.fixed

@@ -0,0 +1,22 @@
+// run-rustfix
+#![warn(clippy::borrow_as_ptr)]
+#![feature(lang_items, start, libc)]
+#![no_std]
+
+#[start]
+fn main(_argc: isize, _argv: *const *const u8) -> isize {
+    let val = 1;
+    let _p = core::ptr::addr_of!(val);
+
+    let mut val_mut = 1;
+    let _p_mut = core::ptr::addr_of_mut!(val_mut);
+    0
+}
+
+#[panic_handler]
+fn panic(_info: &core::panic::PanicInfo) -> ! {
+    loop {}
+}
+
+#[lang = "eh_personality"]
+extern "C" fn eh_personality() {}

tests/ui/borrow_as_ptr_no_std.rs

@@ -0,0 +1,22 @@
+// run-rustfix
+#![warn(clippy::borrow_as_ptr)]
+#![feature(lang_items, start, libc)]
+#![no_std]
+
+#[start]
+fn main(_argc: isize, _argv: *const *const u8) -> isize {
+    let val = 1;
+    let _p = &val as *const i32;
+
+    let mut val_mut = 1;
+    let _p_mut = &mut val_mut as *mut i32;
+    0
+}
+
+#[panic_handler]
+fn panic(_info: &core::panic::PanicInfo) -> ! {
+    loop {}
+}
+
+#[lang = "eh_personality"]
+extern "C" fn eh_personality() {}

tests/ui/borrow_as_ptr_no_std.stderr

@@ -0,0 +1,16 @@
+error: borrow as raw pointer
+  --> $DIR/borrow_as_ptr_no_std.rs:9:14
+   |
+LL |     let _p = &val as *const i32;
+   |              ^^^^^^^^^^^^^^^^^^ help: try: `core::ptr::addr_of!(val)`
+   |
+   = note: `-D clippy::borrow-as-ptr` implied by `-D warnings`
+
+error: borrow as raw pointer
+  --> $DIR/borrow_as_ptr_no_std.rs:12:18
+   |
+LL |     let _p_mut = &mut val_mut as *mut i32;
+   |                  ^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `core::ptr::addr_of_mut!(val_mut)`
+
+error: aborting due to 2 previous errors
+

tests/ui/cast_alignment.rs

@@ -4,7 +4,13 @@
 extern crate libc;
 
 #[warn(clippy::cast_ptr_alignment)]
-#[allow(clippy::no_effect, clippy::unnecessary_operation, clippy::cast_lossless)]
+#[allow(
+    clippy::no_effect,
+    clippy::unnecessary_operation,
+    clippy::cast_lossless,
+    clippy::borrow_as_ptr
+)]
+
 fn main() {
     /* These should be warned against */
 

tests/ui/cast_alignment.stderr

@@ -1,25 +1,25 @@
 error: casting from `*const u8` to a more-strictly-aligned pointer (`*const u16`) (1 < 2 bytes)
-  --> $DIR/cast_alignment.rs:12:5
+  --> $DIR/cast_alignment.rs:18:5
    |
 LL |     (&1u8 as *const u8) as *const u16;
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = note: `-D clippy::cast-ptr-alignment` implied by `-D warnings`
 
 error: casting from `*mut u8` to a more-strictly-aligned pointer (`*mut u16`) (1 < 2 bytes)
-  --> $DIR/cast_alignment.rs:13:5
+  --> $DIR/cast_alignment.rs:19:5
    |
 LL |     (&mut 1u8 as *mut u8) as *mut u16;
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: casting from `*const u8` to a more-strictly-aligned pointer (`*const u16`) (1 < 2 bytes)
-  --> $DIR/cast_alignment.rs:16:5
+  --> $DIR/cast_alignment.rs:22:5
    |
 LL |     (&1u8 as *const u8).cast::<u16>();
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: casting from `*mut u8` to a more-strictly-aligned pointer (`*mut u16`) (1 < 2 bytes)
-  --> $DIR/cast_alignment.rs:17:5
+  --> $DIR/cast_alignment.rs:23:5
    |
 LL |     (&mut 1u8 as *mut u8).cast::<u16>();
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

tests/ui/cast_ref_to_mut.rs

@@ -1,5 +1,5 @@
 #![warn(clippy::cast_ref_to_mut)]
-#![allow(clippy::no_effect)]
+#![allow(clippy::no_effect, clippy::borrow_as_ptr)]
 
 extern "C" {
     // N.B., mutability can be easily incorrect in FFI calls -- as

tests/ui/mutex_atomic.rs

@@ -1,6 +1,7 @@
 #![warn(clippy::all)]
 #![warn(clippy::mutex_integer)]
 #![warn(clippy::mutex_atomic)]
+#![allow(clippy::borrow_as_ptr)]
 
 fn main() {
     use std::sync::Mutex;