New lint: decimal_bit_mask

CHANGELOG.md

@@ -5791,6 +5791,7 @@ Released 2018-09-13
 [`cyclomatic_complexity`]: https://rust-lang.github.io/rust-clippy/master/index.html#cyclomatic_complexity
 [`dbg_macro`]: https://rust-lang.github.io/rust-clippy/master/index.html#dbg_macro
 [`debug_assert_with_mut_call`]: https://rust-lang.github.io/rust-clippy/master/index.html#debug_assert_with_mut_call
+[`decimal_bit_mask`]: https://rust-lang.github.io/rust-clippy/master/index.html#decimal_bit_mask
 [`decimal_literal_representation`]: https://rust-lang.github.io/rust-clippy/master/index.html#decimal_literal_representation
 [`declare_interior_mutable_const`]: https://rust-lang.github.io/rust-clippy/master/index.html#declare_interior_mutable_const
 [`default_constructed_unit_structs`]: https://rust-lang.github.io/rust-clippy/master/index.html#default_constructed_unit_structs

clippy_lints/src/decimal_bit_mask.rs

@@ -0,0 +1,103 @@
+use clippy_utils::diagnostics::span_lint;
+use clippy_utils::source::snippet_opt;
+use rustc_hir::*;
+use rustc_lint::{LateContext, LateLintPass};
+use rustc_session::declare_lint_pass;
+use rustc_span::source_map::Spanned;
+
+declare_clippy_lint! {
+    /// ### What it does
+    /// Checks for decimal literals used as bit masks in bitwise operations.
+    ///
+    /// ### Why is this bad?
+    /// Using decimal literals for bit masks can make the code less readable and obscure the intended bit pattern.
+    /// Binary or hexadecimal literals make the bit pattern more explicit and easier to understand at a glance.
+    ///
+    /// ### Example
+    /// ```rust,no_run
+    /// let a = 15 & 6; // Bit pattern is not immediately clear
+    /// ```
+    /// Use instead:
+    /// ```rust,no_run
+    /// let a = 0b1111 & 0b0110;
+    /// ```
+    #[clippy::version = "1.87.0"]
+    pub DECIMAL_BIT_MASK,
+    nursery,
+    "default lint description"
+}
+
+declare_lint_pass!(DecimalBitMask => [DECIMAL_BIT_MASK]);
+
+impl<'tcx> LateLintPass<'tcx> for DecimalBitMask {
+    fn check_expr(&mut self, cx: &LateContext<'tcx>, e: &'tcx Expr<'_>) {
+        if let ExprKind::Binary(
+            Spanned {
+                node: BinOpKind::BitAnd | BinOpKind::BitOr | BinOpKind::BitXor,
+                ..
+            },
+            Expr {
+                kind: kind1,
+                span: span1,
+                ..
+            },
+            Expr {
+                kind: kind2,
+                span: span2,
+                ..
+            },
+        ) = &e.kind
+        {
+            if let ExprKind::Lit(_) = kind1
+                && let Some(snippet) = snippet_opt(cx, *span1)
+                && !snippet.starts_with("0b")
+                && !snippet.starts_with("0x")
+            {
+                span_lint(
+                    cx,
+                    DECIMAL_BIT_MASK,
+                    e.span,
+                    "Using decimal literal for bit mask. Consider using binary (0b...) or hexadecimal (0x...) notation for better readability.",
+                );
+            }
+
+            if let ExprKind::Lit(_) = kind2
+                && let Some(snippet) = snippet_opt(cx, *span2)
+                && !snippet.starts_with("0b")
+                && !snippet.starts_with("0x")
+            {
+                span_lint(
+                    cx,
+                    DECIMAL_BIT_MASK,
+                    e.span,
+                    "Using decimal literal for bit mask. Consider using binary (0b...) or hexadecimal (0x...) notation for better readability.",
+                );
+            }
+        }
+        if let ExprKind::AssignOp(
+            Spanned {
+                node: AssignOpKind::BitAndAssign | AssignOpKind::BitOrAssign | AssignOpKind::BitXorAssign,
+                ..
+            },
+            _,
+            Expr {
+                kind: ExprKind::Lit(_),
+                span,
+                ..
+            },
+        ) = &e.kind
+        {
+            if let Some(snippet) = snippet_opt(cx, *span)
+                && !snippet.starts_with("0b")
+                && !snippet.starts_with("0x")
+            {
+                span_lint(
+                    cx,
+                    DECIMAL_BIT_MASK,
+                    e.span,
+                    "Using decimal literal for bit mask. Consider using binary (0b...) or hexadecimal (0x...) notation for better readability.",
+                );
+            }
+        }
+    }
+}

clippy_lints/src/declared_lints.rs

@@ -91,6 +91,7 @@ pub static LINTS: &[&::declare_clippy_lint::LintInfo] = &[
     crate::crate_in_macro_def::CRATE_IN_MACRO_DEF_INFO,
     crate::create_dir::CREATE_DIR_INFO,
     crate::dbg_macro::DBG_MACRO_INFO,
+    crate::decimal_bit_mask::DECIMAL_BIT_MASK_INFO,
     crate::default::DEFAULT_TRAIT_ACCESS_INFO,
     crate::default::FIELD_REASSIGN_WITH_DEFAULT_INFO,
     crate::default_constructed_unit_structs::DEFAULT_CONSTRUCTED_UNIT_STRUCTS_INFO,

clippy_lints/src/lib.rs

@@ -105,6 +105,7 @@ mod copy_iterator;
 mod crate_in_macro_def;
 mod create_dir;
 mod dbg_macro;
+mod decimal_bit_mask;
 mod default;
 mod default_constructed_unit_structs;
 mod default_instead_of_iter_empty;
@@ -830,5 +831,6 @@ pub fn register_lint_passes(store: &mut rustc_lint::LintStore, conf: &'static Co
     store.register_late_pass(|_| Box::new(cloned_ref_to_slice_refs::ClonedRefToSliceRefs::new(conf)));
     store.register_late_pass(|_| Box::new(infallible_try_from::InfallibleTryFrom));
     store.register_late_pass(|_| Box::new(coerce_container_to_any::CoerceContainerToAny));
+    store.register_late_pass(|_| Box::new(decimal_bit_mask::DecimalBitMask));
     // add lints here, do not remove this comment, it's used in `new_lint`
 }

tests/ui/decimal_bit_mask.rs

@@ -0,0 +1,50 @@
+#![allow(clippy::no_effect)]
+#![warn(clippy::decimal_bit_mask)]
+fn main() {
+    let mut x = 0;
+    // BAD: Bitwise operation, decimal literal, one literal
+    x & 99; //~ decimal_bit_mask
+    x | 99; //~ decimal_bit_mask
+    x ^ 99; //~ decimal_bit_mask
+    x &= 99; //~ decimal_bit_mask
+    x |= 99; //~ decimal_bit_mask
+    x ^= 99; //~ decimal_bit_mask
+
+    // BAD: Bitwise operation, decimal literal, two literals
+    0b1010 & 99; //~ decimal_bit_mask
+    0b1010 | 99; //~ decimal_bit_mask
+    0b1010 ^ 99; //~ decimal_bit_mask
+    99 & 0b1010; //~ decimal_bit_mask
+    99 | 0b1010; //~ decimal_bit_mask
+    99 ^ 0b1010; //~ decimal_bit_mask
+    0xD | 99; //~ decimal_bit_mask
+    88 & 99; //~ decimal_bit_mask
+
+    // GOOD: Bitwise operation, binary/hex literal, one literal
+    x & 0b1010;
+    x | 0b1010;
+    x ^ 0b1010;
+    x &= 0b1010;
+    x |= 0b1010;
+    x ^= 0b1010;
+    x & 0xD;
+
+    // GOOD: Bitwise operation, binary/hex literal, two literals
+    0b1010 & 0b1101;
+    0xD ^ 0xF;
+
+    // GOOD: Numeric operations, any literal
+    x += 99;
+    x -= 0b1010;
+    x *= 0xD;
+    99 + 99;
+    0b1010 - 0b1101;
+    0xD * 0xD;
+
+    // GOOD: Bitwise operations, variables only
+    let y = 0;
+    x & y;
+    x &= y;
+    x + y;
+    x += y;
+}

tests/ui/decimal_bit_mask.stderr

@@ -0,0 +1,97 @@
+error: Using decimal literal for bit mask. Consider using binary (0b...) or hexadecimal (0x...) notation for better readability.
+  --> tests/ui/decimal_bit_mask.rs:6:5
+   |
+LL |     x & 99;
+   |     ^^^^^^
+   |
+   = note: `-D clippy::decimal-bit-mask` implied by `-D warnings`
+   = help: to override `-D warnings` add `#[allow(clippy::decimal_bit_mask)]`
+
+error: Using decimal literal for bit mask. Consider using binary (0b...) or hexadecimal (0x...) notation for better readability.
+  --> tests/ui/decimal_bit_mask.rs:7:5
+   |
+LL |     x | 99;
+   |     ^^^^^^
+
+error: Using decimal literal for bit mask. Consider using binary (0b...) or hexadecimal (0x...) notation for better readability.
+  --> tests/ui/decimal_bit_mask.rs:8:5
+   |
+LL |     x ^ 99;
+   |     ^^^^^^
+
+error: Using decimal literal for bit mask. Consider using binary (0b...) or hexadecimal (0x...) notation for better readability.
+  --> tests/ui/decimal_bit_mask.rs:9:5
+   |
+LL |     x &= 99;
+   |     ^^^^^^^
+
+error: Using decimal literal for bit mask. Consider using binary (0b...) or hexadecimal (0x...) notation for better readability.
+  --> tests/ui/decimal_bit_mask.rs:10:5
+   |
+LL |     x |= 99;
+   |     ^^^^^^^
+
+error: Using decimal literal for bit mask. Consider using binary (0b...) or hexadecimal (0x...) notation for better readability.
+  --> tests/ui/decimal_bit_mask.rs:11:5
+   |
+LL |     x ^= 99;
+   |     ^^^^^^^
+
+error: Using decimal literal for bit mask. Consider using binary (0b...) or hexadecimal (0x...) notation for better readability.
+  --> tests/ui/decimal_bit_mask.rs:14:5
+   |
+LL |     0b1010 & 99;
+   |     ^^^^^^^^^^^
+
+error: Using decimal literal for bit mask. Consider using binary (0b...) or hexadecimal (0x...) notation for better readability.
+  --> tests/ui/decimal_bit_mask.rs:15:5
+   |
+LL |     0b1010 | 99;
+   |     ^^^^^^^^^^^
+
+error: Using decimal literal for bit mask. Consider using binary (0b...) or hexadecimal (0x...) notation for better readability.
+  --> tests/ui/decimal_bit_mask.rs:16:5
+   |
+LL |     0b1010 ^ 99;
+   |     ^^^^^^^^^^^
+
+error: Using decimal literal for bit mask. Consider using binary (0b...) or hexadecimal (0x...) notation for better readability.
+  --> tests/ui/decimal_bit_mask.rs:17:5
+   |
+LL |     99 & 0b1010;
+   |     ^^^^^^^^^^^
+
+error: Using decimal literal for bit mask. Consider using binary (0b...) or hexadecimal (0x...) notation for better readability.
+  --> tests/ui/decimal_bit_mask.rs:18:5
+   |
+LL |     99 | 0b1010;
+   |     ^^^^^^^^^^^
+
+error: Using decimal literal for bit mask. Consider using binary (0b...) or hexadecimal (0x...) notation for better readability.
+  --> tests/ui/decimal_bit_mask.rs:19:5
+   |
+LL |     99 ^ 0b1010;
+   |     ^^^^^^^^^^^
+
+error: Using decimal literal for bit mask. Consider using binary (0b...) or hexadecimal (0x...) notation for better readability.
+  --> tests/ui/decimal_bit_mask.rs:20:5
+   |
+LL |     0xD | 99;
+   |     ^^^^^^^^
+
+error: Using decimal literal for bit mask. Consider using binary (0b...) or hexadecimal (0x...) notation for better readability.
+  --> tests/ui/decimal_bit_mask.rs:21:5
+   |
+LL |     88 & 99;
+   |     ^^^^^^^
+
+error: Using decimal literal for bit mask. Consider using binary (0b...) or hexadecimal (0x...) notation for better readability.
+  --> tests/ui/decimal_bit_mask.rs:21:5
+   |
+LL |     88 & 99;
+   |     ^^^^^^^
+   |
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
+
+error: aborting due to 15 previous errors
+