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Move BitMask into Operators lint pass

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This commit is contained in:
Jason Newcomb 2022-05-31 22:14:43 -04:00
parent 751131b4ac
commit 68a7fd22ad
8 changed files with 179 additions and 166 deletions
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4
clippy_lints/src/lib.register_all.rs
View File

@ -15,8 +15,6 @@ store.register_group(true, "clippy::all", Some("clippy_all"), vec![
LintId::of(await_holding_invalid::AWAIT_HOLDING_INVALID_TYPE),
LintId::of(await_holding_invalid::AWAIT_HOLDING_LOCK),
LintId::of(await_holding_invalid::AWAIT_HOLDING_REFCELL_REF),
LintId::of(bit_mask::BAD_BIT_MASK),
LintId::of(bit_mask::INEFFECTIVE_BIT_MASK),
LintId::of(blacklisted_name::BLACKLISTED_NAME),
LintId::of(blocks_in_if_conditions::BLOCKS_IN_IF_CONDITIONS),
LintId::of(bool_assert_comparison::BOOL_ASSERT_COMPARISON),
@ -259,6 +257,8 @@ store.register_group(true, "clippy::all", Some("clippy_all"), vec![
LintId::of(open_options::NONSENSICAL_OPEN_OPTIONS),
LintId::of(operators::ABSURD_EXTREME_COMPARISONS),
LintId::of(operators::ASSIGN_OP_PATTERN),
LintId::of(operators::BAD_BIT_MASK),
LintId::of(operators::INEFFECTIVE_BIT_MASK),
LintId::of(operators::MISREFACTORED_ASSIGN_OP),
LintId::of(option_env_unwrap::OPTION_ENV_UNWRAP),
LintId::of(overflow_check_conditional::OVERFLOW_CHECK_CONDITIONAL),

4
clippy_lints/src/lib.register_correctness.rs
View File

@ -8,8 +8,6 @@ store.register_group(true, "clippy::correctness", Some("clippy_correctness"), ve
LintId::of(attrs::DEPRECATED_SEMVER),
LintId::of(attrs::MISMATCHED_TARGET_OS),
LintId::of(attrs::USELESS_ATTRIBUTE),
LintId::of(bit_mask::BAD_BIT_MASK),
LintId::of(bit_mask::INEFFECTIVE_BIT_MASK),
LintId::of(booleans::LOGIC_BUG),
LintId::of(casts::CAST_REF_TO_MUT),
LintId::of(casts::CAST_SLICE_DIFFERENT_SIZES),
@ -51,6 +49,8 @@ store.register_group(true, "clippy::correctness", Some("clippy_correctness"), ve
LintId::of(non_octal_unix_permissions::NON_OCTAL_UNIX_PERMISSIONS),
LintId::of(open_options::NONSENSICAL_OPEN_OPTIONS),
LintId::of(operators::ABSURD_EXTREME_COMPARISONS),
LintId::of(operators::BAD_BIT_MASK),
LintId::of(operators::INEFFECTIVE_BIT_MASK),
LintId::of(option_env_unwrap::OPTION_ENV_UNWRAP),
LintId::of(ptr::INVALID_NULL_PTR_USAGE),
LintId::of(ptr::MUT_FROM_REF),

6
clippy_lints/src/lib.register_lints.rs
View File

@ -54,9 +54,6 @@ store.register_lints(&[
await_holding_invalid::AWAIT_HOLDING_INVALID_TYPE,
await_holding_invalid::AWAIT_HOLDING_LOCK,
await_holding_invalid::AWAIT_HOLDING_REFCELL_REF,
bit_mask::BAD_BIT_MASK,
bit_mask::INEFFECTIVE_BIT_MASK,
bit_mask::VERBOSE_BIT_MASK,
blacklisted_name::BLACKLISTED_NAME,
blocks_in_if_conditions::BLOCKS_IN_IF_CONDITIONS,
bool_assert_comparison::BOOL_ASSERT_COMPARISON,
@ -434,9 +431,12 @@ store.register_lints(&[
open_options::NONSENSICAL_OPEN_OPTIONS,
operators::ABSURD_EXTREME_COMPARISONS,
operators::ASSIGN_OP_PATTERN,
operators::BAD_BIT_MASK,
operators::FLOAT_ARITHMETIC,
operators::INEFFECTIVE_BIT_MASK,
operators::INTEGER_ARITHMETIC,
operators::MISREFACTORED_ASSIGN_OP,
operators::VERBOSE_BIT_MASK,
option_env_unwrap::OPTION_ENV_UNWRAP,
option_if_let_else::OPTION_IF_LET_ELSE,
overflow_check_conditional::OVERFLOW_CHECK_CONDITIONAL,

2
clippy_lints/src/lib.register_pedantic.rs
View File

@ -4,7 +4,6 @@
store.register_group(true, "clippy::pedantic", Some("clippy_pedantic"), vec![
LintId::of(attrs::INLINE_ALWAYS),
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),
@ -76,6 +75,7 @@ store.register_group(true, "clippy::pedantic", Some("clippy_pedantic"), vec![
LintId::of(no_effect::NO_EFFECT_UNDERSCORE_BINDING),
LintId::of(non_expressive_names::MANY_SINGLE_CHAR_NAMES),
LintId::of(non_expressive_names::SIMILAR_NAMES),
LintId::of(operators::VERBOSE_BIT_MASK),
LintId::of(pass_by_ref_or_value::LARGE_TYPES_PASSED_BY_VALUE),
LintId::of(pass_by_ref_or_value::TRIVIALLY_COPY_PASS_BY_REF),
LintId::of(ranges::RANGE_MINUS_ONE),

6
clippy_lints/src/lib.rs
View File

@ -177,7 +177,6 @@ mod assertions_on_constants;
mod async_yields_async;
mod attrs;
mod await_holding_invalid;
mod bit_mask;
mod blacklisted_name;
mod blocks_in_if_conditions;
mod bool_assert_comparison;
@ -582,8 +581,6 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
store.register_late_pass(|| Box::new(eq_op::EqOp));
store.register_late_pass(|| Box::new(enum_clike::UnportableVariant));
store.register_late_pass(|| Box::new(float_literal::FloatLiteral));
let verbose_bit_mask_threshold = conf.verbose_bit_mask_threshold;
store.register_late_pass(move || Box::new(bit_mask::BitMask::new(verbose_bit_mask_threshold)));
store.register_late_pass(|| Box::new(ptr::Ptr));
store.register_late_pass(|| Box::new(ptr_eq::PtrEq));
store.register_late_pass(|| Box::new(needless_bool::NeedlessBool));
@ -936,7 +933,8 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
store.register_late_pass(|| Box::new(default_instead_of_iter_empty::DefaultIterEmpty));
store.register_late_pass(move || Box::new(manual_rem_euclid::ManualRemEuclid::new(msrv)));
store.register_late_pass(move || Box::new(manual_retain::ManualRetain::new(msrv)));
store.register_late_pass(|| Box::new(operators::Operators::default()));
let verbose_bit_mask_threshold = conf.verbose_bit_mask_threshold;
store.register_late_pass(move || Box::new(operators::Operators::new(verbose_bit_mask_threshold)));
// add lints here, do not remove this comment, it's used in `new_lint`
}

168
clippy_lints/src/bit_mask.rs → clippy_lints/src/operators/bit_mask.rs
View File

@ -1,161 +1,23 @@
use clippy_utils::consts::{constant, Constant};
use clippy_utils::diagnostics::{span_lint, span_lint_and_then};
use clippy_utils::sugg::Sugg;
use rustc_ast::ast::LitKind;
use rustc_errors::Applicability;
use clippy_utils::diagnostics::span_lint;
use rustc_hir::{BinOpKind, Expr, ExprKind};
use rustc_lint::{LateContext, LateLintPass};
use rustc_session::{declare_tool_lint, impl_lint_pass};
use rustc_lint::LateContext;
use rustc_span::source_map::Span;
declare_clippy_lint! {
/// ### What it does
/// Checks for incompatible bit masks in comparisons.
///
/// The formula for detecting if an expression of the type `_ <bit_op> m
/// <cmp_op> c` (where `<bit_op>` is one of {`&`, `|`} and `<cmp_op>` is one of
/// {`!=`, `>=`, `>`, `!=`, `>=`, `>`}) can be determined from the following
/// table:
///
/// |Comparison |Bit Op|Example |is always|Formula |
/// |------------|------|-------------|---------|----------------------|
/// |`==` or `!=`| `&` |`x & 2 == 3` |`false` |`c & m != c` |
/// |`<` or `>=`| `&` |`x & 2 < 3` |`true` |`m < c` |
/// |`>` or `<=`| `&` |`x & 1 > 1` |`false` |`m <= c` |
/// |`==` or `!=`| `\|` |`x \| 1 == 0`|`false` |`c \| m != c` |
/// |`<` or `>=`| `\|` |`x \| 1 < 1` |`false` |`m >= c` |
/// |`<=` or `>` | `\|` |`x \| 1 > 0` |`true` |`m > c` |
///
/// ### Why is this bad?
/// If the bits that the comparison cares about are always
/// set to zero or one by the bit mask, the comparison is constant `true` or
/// `false` (depending on mask, compared value, and operators).
///
/// So the code is actively misleading, and the only reason someone would write
/// this intentionally is to win an underhanded Rust contest or create a
/// test-case for this lint.
///
/// ### Example
/// ```rust
/// # let x = 1;
/// if (x & 1 == 2) { }
/// ```
#[clippy::version = "pre 1.29.0"]
pub BAD_BIT_MASK,
correctness,
"expressions of the form `_ & mask == select` that will only ever return `true` or `false`"
}
use super::{BAD_BIT_MASK, INEFFECTIVE_BIT_MASK};
declare_clippy_lint! {
/// ### What it does
/// Checks for bit masks in comparisons which can be removed
/// without changing the outcome. The basic structure can be seen in the
/// following table:
///
/// |Comparison| Bit Op |Example |equals |
/// |----------|----------|------------|-------|
/// |`>` / `<=`|`\|` / `^`|`x \| 2 > 3`|`x > 3`|
/// |`<` / `>=`|`\|` / `^`|`x ^ 1 < 4` |`x < 4`|
///
/// ### Why is this bad?
/// Not equally evil as [`bad_bit_mask`](#bad_bit_mask),
/// but still a bit misleading, because the bit mask is ineffective.
///
/// ### Known problems
/// False negatives: This lint will only match instances
/// where we have figured out the math (which is for a power-of-two compared
/// value). This means things like `x | 1 >= 7` (which would be better written
/// as `x >= 6`) will not be reported (but bit masks like this are fairly
/// uncommon).
///
/// ### Example
/// ```rust
/// # let x = 1;
/// if (x | 1 > 3) { }
/// ```
#[clippy::version = "pre 1.29.0"]
pub INEFFECTIVE_BIT_MASK,
correctness,
"expressions where a bit mask will be rendered useless by a comparison, e.g., `(x | 1) > 2`"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for bit masks that can be replaced by a call
/// to `trailing_zeros`
///
/// ### Why is this bad?
/// `x.trailing_zeros() > 4` is much clearer than `x & 15
/// == 0`
///
/// ### Known problems
/// llvm generates better code for `x & 15 == 0` on x86
///
/// ### Example
/// ```rust
/// # let x = 1;
/// if x & 0b1111 == 0 { }
/// ```
#[clippy::version = "pre 1.29.0"]
pub VERBOSE_BIT_MASK,
pedantic,
"expressions where a bit mask is less readable than the corresponding method call"
}
#[derive(Copy, Clone)]
pub struct BitMask {
verbose_bit_mask_threshold: u64,
}
impl BitMask {
#[must_use]
pub fn new(verbose_bit_mask_threshold: u64) -> Self {
Self {
verbose_bit_mask_threshold,
}
}
}
impl_lint_pass!(BitMask => [BAD_BIT_MASK, INEFFECTIVE_BIT_MASK, VERBOSE_BIT_MASK]);
impl<'tcx> LateLintPass<'tcx> for BitMask {
fn check_expr(&mut self, cx: &LateContext<'tcx>, e: &'tcx Expr<'_>) {
if let ExprKind::Binary(cmp, left, right) = &e.kind {
if cmp.node.is_comparison() {
if let Some(cmp_opt) = fetch_int_literal(cx, right) {
check_compare(cx, left, cmp.node, cmp_opt, e.span);
} else if let Some(cmp_val) = fetch_int_literal(cx, left) {
check_compare(cx, right, invert_cmp(cmp.node), cmp_val, e.span);
}
}
}
if let ExprKind::Binary(op, left, right) = &e.kind
&& BinOpKind::Eq == op.node
&& let ExprKind::Binary(op1, left1, right1) = &left.kind
&& BinOpKind::BitAnd == op1.node
&& let ExprKind::Lit(lit) = &right1.kind
&& let LitKind::Int(n, _) = lit.node
&& let ExprKind::Lit(lit1) = &right.kind
&& let LitKind::Int(0, _) = lit1.node
&& n.leading_zeros() == n.count_zeros()
&& n > u128::from(self.verbose_bit_mask_threshold)
{
span_lint_and_then(
cx,
VERBOSE_BIT_MASK,
e.span,
"bit mask could be simplified with a call to `trailing_zeros`",
|diag| {
let sugg = Sugg::hir(cx, left1, "...").maybe_par();
diag.span_suggestion(
e.span,
"try",
format!("{}.trailing_zeros() >= {}", sugg, n.count_ones()),
Applicability::MaybeIncorrect,
);
},
);
pub(super) fn check<'tcx>(
cx: &LateContext<'tcx>,
e: &'tcx Expr<'_>,
op: BinOpKind,
left: &'tcx Expr<'_>,
right: &'tcx Expr<'_>,
) {
if op.is_comparison() {
if let Some(cmp_opt) = fetch_int_literal(cx, right) {
check_compare(cx, left, op, cmp_opt, e.span);
} else if let Some(cmp_val) = fetch_int_literal(cx, left) {
check_compare(cx, right, invert_cmp(op), cmp_val, e.span);
}
}
}

111
clippy_lints/src/operators/mod.rs
View File

@ -4,8 +4,10 @@ use rustc_session::{declare_tool_lint, impl_lint_pass};
mod absurd_extreme_comparisons;
mod assign_op_pattern;
mod bit_mask;
mod misrefactored_assign_op;
mod numeric_arithmetic;
mod verbose_bit_mask;
declare_clippy_lint! {
/// ### What it does
@ -146,9 +148,103 @@ declare_clippy_lint! {
"having a variable on both sides of an assign op"
}
#[derive(Default)]
declare_clippy_lint! {
/// ### What it does
/// Checks for incompatible bit masks in comparisons.
///
/// The formula for detecting if an expression of the type `_ <bit_op> m
/// <cmp_op> c` (where `<bit_op>` is one of {`&`, `|`} and `<cmp_op>` is one of
/// {`!=`, `>=`, `>`, `!=`, `>=`, `>`}) can be determined from the following
/// table:
///
/// |Comparison |Bit Op|Example |is always|Formula |
/// |------------|------|-------------|---------|----------------------|
/// |`==` or `!=`| `&` |`x & 2 == 3` |`false` |`c & m != c` |
/// |`<` or `>=`| `&` |`x & 2 < 3` |`true` |`m < c` |
/// |`>` or `<=`| `&` |`x & 1 > 1` |`false` |`m <= c` |
/// |`==` or `!=`| `\|` |`x \| 1 == 0`|`false` |`c \| m != c` |
/// |`<` or `>=`| `\|` |`x \| 1 < 1` |`false` |`m >= c` |
/// |`<=` or `>` | `\|` |`x \| 1 > 0` |`true` |`m > c` |
///
/// ### Why is this bad?
/// If the bits that the comparison cares about are always
/// set to zero or one by the bit mask, the comparison is constant `true` or
/// `false` (depending on mask, compared value, and operators).
///
/// So the code is actively misleading, and the only reason someone would write
/// this intentionally is to win an underhanded Rust contest or create a
/// test-case for this lint.
///
/// ### Example
/// ```rust
/// # let x = 1;
/// if (x & 1 == 2) { }
/// ```
#[clippy::version = "pre 1.29.0"]
pub BAD_BIT_MASK,
correctness,
"expressions of the form `_ & mask == select` that will only ever return `true` or `false`"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for bit masks in comparisons which can be removed
/// without changing the outcome. The basic structure can be seen in the
/// following table:
///
/// |Comparison| Bit Op |Example |equals |
/// |----------|----------|------------|-------|
/// |`>` / `<=`|`\|` / `^`|`x \| 2 > 3`|`x > 3`|
/// |`<` / `>=`|`\|` / `^`|`x ^ 1 < 4` |`x < 4`|
///
/// ### Why is this bad?
/// Not equally evil as [`bad_bit_mask`](#bad_bit_mask),
/// but still a bit misleading, because the bit mask is ineffective.
///
/// ### Known problems
/// False negatives: This lint will only match instances
/// where we have figured out the math (which is for a power-of-two compared
/// value). This means things like `x | 1 >= 7` (which would be better written
/// as `x >= 6`) will not be reported (but bit masks like this are fairly
/// uncommon).
///
/// ### Example
/// ```rust
/// # let x = 1;
/// if (x | 1 > 3) { }
/// ```
#[clippy::version = "pre 1.29.0"]
pub INEFFECTIVE_BIT_MASK,
correctness,
"expressions where a bit mask will be rendered useless by a comparison, e.g., `(x | 1) > 2`"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for bit masks that can be replaced by a call
/// to `trailing_zeros`
///
/// ### Why is this bad?
/// `x.trailing_zeros() > 4` is much clearer than `x & 15
/// == 0`
///
/// ### Known problems
/// llvm generates better code for `x & 15 == 0` on x86
///
/// ### Example
/// ```rust
/// # let x = 1;
/// if x & 0b1111 == 0 { }
/// ```
#[clippy::version = "pre 1.29.0"]
pub VERBOSE_BIT_MASK,
pedantic,
"expressions where a bit mask is less readable than the corresponding method call"
}
pub struct Operators {
arithmetic_context: numeric_arithmetic::Context,
verbose_bit_mask_threshold: u64,
}
impl_lint_pass!(Operators => [
ABSURD_EXTREME_COMPARISONS,
@ -156,7 +252,18 @@ impl_lint_pass!(Operators => [
FLOAT_ARITHMETIC,
ASSIGN_OP_PATTERN,
MISREFACTORED_ASSIGN_OP,
BAD_BIT_MASK,
INEFFECTIVE_BIT_MASK,
VERBOSE_BIT_MASK,
]);
impl Operators {
pub fn new(verbose_bit_mask_threshold: u64) -> Self {
Self {
arithmetic_context: numeric_arithmetic::Context::default(),
verbose_bit_mask_threshold,
}
}
}
impl<'tcx> LateLintPass<'tcx> for Operators {
fn check_expr(&mut self, cx: &LateContext<'tcx>, e: &'tcx Expr<'_>) {
match e.kind {
@ -165,6 +272,8 @@ impl<'tcx> LateLintPass<'tcx> for Operators {
absurd_extreme_comparisons::check(cx, e, op.node, lhs, rhs);
}
self.arithmetic_context.check_binary(cx, e, op.node, lhs, rhs);
bit_mask::check(cx, e, op.node, lhs, rhs);
verbose_bit_mask::check(cx, e, op.node, lhs, rhs, self.verbose_bit_mask_threshold);
},
ExprKind::AssignOp(op, lhs, rhs) => {
self.arithmetic_context.check_binary(cx, e, op.node, lhs, rhs);

44
clippy_lints/src/operators/verbose_bit_mask.rs Normal file
View File

@ -0,0 +1,44 @@
use clippy_utils::diagnostics::span_lint_and_then;
use clippy_utils::sugg::Sugg;
use rustc_ast::ast::LitKind;
use rustc_errors::Applicability;
use rustc_hir::{BinOpKind, Expr, ExprKind};
use rustc_lint::LateContext;
use super::VERBOSE_BIT_MASK;
pub(super) fn check<'tcx>(
cx: &LateContext<'tcx>,
e: &'tcx Expr<'_>,
op: BinOpKind,
left: &'tcx Expr<'_>,
right: &'tcx Expr<'_>,
threshold: u64,
) {
if BinOpKind::Eq == op
&& let ExprKind::Binary(op1, left1, right1) = &left.kind
&& BinOpKind::BitAnd == op1.node
&& let ExprKind::Lit(lit) = &right1.kind
&& let LitKind::Int(n, _) = lit.node
&& let ExprKind::Lit(lit1) = &right.kind
&& let LitKind::Int(0, _) = lit1.node
&& n.leading_zeros() == n.count_zeros()
&& n > u128::from(threshold)
{
span_lint_and_then(
cx,
VERBOSE_BIT_MASK,
e.span,
"bit mask could be simplified with a call to `trailing_zeros`",
|diag| {
let sugg = Sugg::hir(cx, left1, "...").maybe_par();
diag.span_suggestion(
e.span,
"try",
format!("{}.trailing_zeros() >= {}", sugg, n.count_ones()),
Applicability::MaybeIncorrect,
);
},
);
}
}