use rustc::hir::*;
-use rustc::hir::def::{Def, PathResolution};
use rustc::lint::*;
-use rustc_const_eval::lookup_const_by_id;
+use rustc::{declare_lint, lint_array};
+use if_chain::if_chain;
use syntax::ast::LitKind;
use syntax::codemap::Span;
-use utils::span_lint;
+use crate::utils::{span_lint, span_lint_and_then};
+use crate::utils::sugg::Sugg;
+use crate::consts::{constant, Constant};
-/// **What it does:** This lint checks for incompatible bit masks in comparisons.
+/// **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:
+/// 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 | 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).
+/// **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.
+/// 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.
///
-/// **Known problems:** None
+/// **Known problems:** None.
///
-/// **Example:** `x & 1 == 2` (also see table above)
-declare_lint! {
+/// **Example:**
+/// ```rust
+/// if (x & 1 == 2) { … }
+/// ```
+declare_clippy_lint! {
pub BAD_BIT_MASK,
- Warn,
- "expressions of the form `_ & mask == select` that will only ever return `true` or `false` \
- (because in the example `select` containing bits that `mask` doesn't have)"
+ correctness,
+ "expressions of the form `_ & mask == select` that will only ever return `true` or `false`"
}
-/// **What it does:** This lint checks for bit masks in comparisons which can be removed without changing the outcome. The basic structure can be seen in the following table:
+/// **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.
+/// **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).
+/// **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:** `x | 1 > 3` (also see table above)
-declare_lint! {
+/// **Example:**
+/// ```rust
+/// if (x | 1 > 3) { … }
+/// ```
+declare_clippy_lint! {
pub INEFFECTIVE_BIT_MASK,
- Warn,
+ correctness,
"expressions where a bit mask will be rendered useless by a comparison, e.g. `(x | 1) > 2`"
}
-/// Checks for incompatible bit masks in comparisons, e.g. `x & 1 == 2`.
-/// This cannot work because the bit that makes up the value two was
-/// zeroed out by the bit-and with 1. So 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:
+/// **What it does:** Checks for bit masks that can be replaced by a call
+/// to `trailing_zeros`
///
-/// |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` |
-///
-/// This lint is **deny** by default
-///
-/// There is also a lint that warns on ineffective masks that is *warn*
-/// by default.
+/// **Why is this bad?** `x.trailing_zeros() > 4` is much clearer than `x & 15
+/// == 0`
///
-/// |Comparison|Bit Op |Example |equals |Formula|
-/// |`>` / `<=`|`|` / `^`|`x | 2 > 3`|`x > 3`|`¹ && m <= c`|
-/// |`<` / `>=`|`|` / `^`|`x ^ 1 < 4`|`x < 4`|`¹ && m < c` |
+/// **Known problems:** llvm generates better code for `x & 15 == 0` on x86
///
-/// `¹ power_of_two(c + 1)`
-#[derive(Copy,Clone)]
-pub struct BitMask;
+/// **Example:**
+/// ```rust
+/// x & 0x1111 == 0
+/// ```
+declare_clippy_lint! {
+ pub VERBOSE_BIT_MASK,
+ style,
+ "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 {
+ pub fn new(verbose_bit_mask_threshold: u64) -> Self {
+ Self {
+ verbose_bit_mask_threshold,
+ }
+ }
+}
impl LintPass for BitMask {
fn get_lints(&self) -> LintArray {
- lint_array!(BAD_BIT_MASK, INEFFECTIVE_BIT_MASK)
+ lint_array!(BAD_BIT_MASK, INEFFECTIVE_BIT_MASK, VERBOSE_BIT_MASK)
}
}
-impl LateLintPass for BitMask {
- fn check_expr(&mut self, cx: &LateContext, e: &Expr) {
- if let ExprBinary(ref cmp, ref left, ref right) = e.node {
+impl<'a, 'tcx> LateLintPass<'a, 'tcx> for BitMask {
+ fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, e: &'tcx Expr) {
+ if let ExprKind::Binary(ref cmp, ref left, ref right) = e.node {
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)
+ 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)
+ check_compare(cx, right, invert_cmp(cmp.node), cmp_val, e.span)
}
}
}
+ if_chain! {
+ if let ExprKind::Binary(ref op, ref left, ref right) = e.node;
+ if BinOpKind::Eq == op.node;
+ if let ExprKind::Binary(ref op1, ref left1, ref right1) = left.node;
+ if BinOpKind::BitAnd == op1.node;
+ if let ExprKind::Lit(ref lit) = right1.node;
+ if let LitKind::Int(n, _) = lit.node;
+ if let ExprKind::Lit(ref lit1) = right.node;
+ if let LitKind::Int(0, _) = lit1.node;
+ if n.leading_zeros() == n.count_zeros();
+ if n > u128::from(self.verbose_bit_mask_threshold);
+ then {
+ span_lint_and_then(cx,
+ VERBOSE_BIT_MASK,
+ e.span,
+ "bit mask could be simplified with a call to `trailing_zeros`",
+ |db| {
+ let sugg = Sugg::hir(cx, left1, "...").maybe_par();
+ db.span_suggestion(e.span, "try", format!("{}.trailing_zeros() >= {}", sugg, n.count_ones()));
+ });
+ }
+ }
}
}
-fn invert_cmp(cmp: BinOp_) -> BinOp_ {
+fn invert_cmp(cmp: BinOpKind) -> BinOpKind {
match cmp {
- BiEq => BiEq,
- BiNe => BiNe,
- BiLt => BiGt,
- BiGt => BiLt,
- BiLe => BiGe,
- BiGe => BiLe,
- _ => BiOr, // Dummy
+ BinOpKind::Eq => BinOpKind::Eq,
+ BinOpKind::Ne => BinOpKind::Ne,
+ BinOpKind::Lt => BinOpKind::Gt,
+ BinOpKind::Gt => BinOpKind::Lt,
+ BinOpKind::Le => BinOpKind::Ge,
+ BinOpKind::Ge => BinOpKind::Le,
+ _ => BinOpKind::Or, // Dummy
}
}
-fn check_compare(cx: &LateContext, bit_op: &Expr, cmp_op: BinOp_, cmp_value: u64, span: &Span) {
- if let ExprBinary(ref op, ref left, ref right) = bit_op.node {
- if op.node != BiBitAnd && op.node != BiBitOr {
+fn check_compare(cx: &LateContext, bit_op: &Expr, cmp_op: BinOpKind, cmp_value: u128, span: Span) {
+ if let ExprKind::Binary(ref op, ref left, ref right) = bit_op.node {
+ if op.node != BinOpKind::BitAnd && op.node != BinOpKind::BitOr {
return;
}
fetch_int_literal(cx, right)
}
}
-fn check_bit_mask(cx: &LateContext, bit_op: BinOp_, cmp_op: BinOp_, mask_value: u64, cmp_value: u64, span: &Span) {
+fn check_bit_mask(cx: &LateContext, bit_op: BinOpKind, cmp_op: BinOpKind, mask_value: u128, cmp_value: u128, span: Span) {
match cmp_op {
- BiEq | BiNe => {
- match bit_op {
- BiBitAnd => {
- if mask_value & cmp_value != cmp_value {
- if cmp_value != 0 {
- span_lint(cx,
- BAD_BIT_MASK,
- *span,
- &format!("incompatible bit mask: `_ & {}` can never be equal to `{}`",
- mask_value,
- cmp_value));
- }
- } else if mask_value == 0 {
- span_lint(cx, BAD_BIT_MASK, *span, "&-masking with zero");
- }
+ BinOpKind::Eq | BinOpKind::Ne => match bit_op {
+ BinOpKind::BitAnd => if mask_value & cmp_value != cmp_value {
+ if cmp_value != 0 {
+ span_lint(
+ cx,
+ BAD_BIT_MASK,
+ span,
+ &format!(
+ "incompatible bit mask: `_ & {}` can never be equal to `{}`",
+ mask_value,
+ cmp_value
+ ),
+ );
}
- BiBitOr => {
- if mask_value | cmp_value != cmp_value {
- span_lint(cx,
- BAD_BIT_MASK,
- *span,
- &format!("incompatible bit mask: `_ | {}` can never be equal to `{}`",
- mask_value,
- cmp_value));
- }
- }
- _ => (),
- }
- }
- BiLt | BiGe => {
- match bit_op {
- BiBitAnd => {
- if mask_value < cmp_value {
- span_lint(cx,
- BAD_BIT_MASK,
- *span,
- &format!("incompatible bit mask: `_ & {}` will always be lower than `{}`",
- mask_value,
- cmp_value));
- } else if mask_value == 0 {
- span_lint(cx, BAD_BIT_MASK, *span, "&-masking with zero");
- }
- }
- BiBitOr => {
- if mask_value >= cmp_value {
- span_lint(cx,
- BAD_BIT_MASK,
- *span,
- &format!("incompatible bit mask: `_ | {}` will never be lower than `{}`",
- mask_value,
- cmp_value));
- } else {
- check_ineffective_lt(cx, *span, mask_value, cmp_value, "|");
- }
- }
- BiBitXor => check_ineffective_lt(cx, *span, mask_value, cmp_value, "^"),
- _ => (),
- }
- }
- BiLe | BiGt => {
- match bit_op {
- BiBitAnd => {
- if mask_value <= cmp_value {
- span_lint(cx,
- BAD_BIT_MASK,
- *span,
- &format!("incompatible bit mask: `_ & {}` will never be higher than `{}`",
- mask_value,
- cmp_value));
- } else if mask_value == 0 {
- span_lint(cx, BAD_BIT_MASK, *span, "&-masking with zero");
- }
- }
- BiBitOr => {
- if mask_value > cmp_value {
- span_lint(cx,
- BAD_BIT_MASK,
- *span,
- &format!("incompatible bit mask: `_ | {}` will always be higher than `{}`",
- mask_value,
- cmp_value));
- } else {
- check_ineffective_gt(cx, *span, mask_value, cmp_value, "|");
- }
- }
- BiBitXor => check_ineffective_gt(cx, *span, mask_value, cmp_value, "^"),
- _ => (),
- }
- }
+ } else if mask_value == 0 {
+ span_lint(cx, BAD_BIT_MASK, span, "&-masking with zero");
+ },
+ BinOpKind::BitOr => if mask_value | cmp_value != cmp_value {
+ span_lint(
+ cx,
+ BAD_BIT_MASK,
+ span,
+ &format!(
+ "incompatible bit mask: `_ | {}` can never be equal to `{}`",
+ mask_value,
+ cmp_value
+ ),
+ );
+ },
+ _ => (),
+ },
+ BinOpKind::Lt | BinOpKind::Ge => match bit_op {
+ BinOpKind::BitAnd => if mask_value < cmp_value {
+ span_lint(
+ cx,
+ BAD_BIT_MASK,
+ span,
+ &format!(
+ "incompatible bit mask: `_ & {}` will always be lower than `{}`",
+ mask_value,
+ cmp_value
+ ),
+ );
+ } else if mask_value == 0 {
+ span_lint(cx, BAD_BIT_MASK, span, "&-masking with zero");
+ },
+ BinOpKind::BitOr => if mask_value >= cmp_value {
+ span_lint(
+ cx,
+ BAD_BIT_MASK,
+ span,
+ &format!(
+ "incompatible bit mask: `_ | {}` will never be lower than `{}`",
+ mask_value,
+ cmp_value
+ ),
+ );
+ } else {
+ check_ineffective_lt(cx, span, mask_value, cmp_value, "|");
+ },
+ BinOpKind::BitXor => check_ineffective_lt(cx, span, mask_value, cmp_value, "^"),
+ _ => (),
+ },
+ BinOpKind::Le | BinOpKind::Gt => match bit_op {
+ BinOpKind::BitAnd => if mask_value <= cmp_value {
+ span_lint(
+ cx,
+ BAD_BIT_MASK,
+ span,
+ &format!(
+ "incompatible bit mask: `_ & {}` will never be higher than `{}`",
+ mask_value,
+ cmp_value
+ ),
+ );
+ } else if mask_value == 0 {
+ span_lint(cx, BAD_BIT_MASK, span, "&-masking with zero");
+ },
+ BinOpKind::BitOr => if mask_value > cmp_value {
+ span_lint(
+ cx,
+ BAD_BIT_MASK,
+ span,
+ &format!(
+ "incompatible bit mask: `_ | {}` will always be higher than `{}`",
+ mask_value,
+ cmp_value
+ ),
+ );
+ } else {
+ check_ineffective_gt(cx, span, mask_value, cmp_value, "|");
+ },
+ BinOpKind::BitXor => check_ineffective_gt(cx, span, mask_value, cmp_value, "^"),
+ _ => (),
+ },
_ => (),
}
}
-fn check_ineffective_lt(cx: &LateContext, span: Span, m: u64, c: u64, op: &str) {
+fn check_ineffective_lt(cx: &LateContext, span: Span, m: u128, c: u128, op: &str) {
if c.is_power_of_two() && m < c {
- span_lint(cx,
- INEFFECTIVE_BIT_MASK,
- span,
- &format!("ineffective bit mask: `x {} {}` compared to `{}`, is the same as x compared directly",
- op,
- m,
- c));
+ span_lint(
+ cx,
+ INEFFECTIVE_BIT_MASK,
+ span,
+ &format!(
+ "ineffective bit mask: `x {} {}` compared to `{}`, is the same as x compared directly",
+ op,
+ m,
+ c
+ ),
+ );
}
}
-fn check_ineffective_gt(cx: &LateContext, span: Span, m: u64, c: u64, op: &str) {
+fn check_ineffective_gt(cx: &LateContext, span: Span, m: u128, c: u128, op: &str) {
if (c + 1).is_power_of_two() && m <= c {
- span_lint(cx,
- INEFFECTIVE_BIT_MASK,
- span,
- &format!("ineffective bit mask: `x {} {}` compared to `{}`, is the same as x compared directly",
- op,
- m,
- c));
+ span_lint(
+ cx,
+ INEFFECTIVE_BIT_MASK,
+ span,
+ &format!(
+ "ineffective bit mask: `x {} {}` compared to `{}`, is the same as x compared directly",
+ op,
+ m,
+ c
+ ),
+ );
}
}
-fn fetch_int_literal(cx: &LateContext, lit: &Expr) -> Option<u64> {
- match lit.node {
- ExprLit(ref lit_ptr) => {
- if let LitKind::Int(value, _) = lit_ptr.node {
- Some(value) //TODO: Handle sign
- } else {
- None
- }
- }
- ExprPath(_, _) => {
- {
- // Important to let the borrow expire before the const lookup to avoid double
- // borrowing.
- let def_map = cx.tcx.def_map.borrow();
- match def_map.get(&lit.id) {
- Some(&PathResolution { base_def: Def::Const(def_id), .. }) => Some(def_id),
- _ => None,
- }
- }
- .and_then(|def_id| lookup_const_by_id(cx.tcx, def_id, None))
- .and_then(|(l, _ty)| fetch_int_literal(cx, l))
- }
+fn fetch_int_literal(cx: &LateContext, lit: &Expr) -> Option<u128> {
+ match constant(cx, cx.tables, lit)?.0 {
+ Constant::Int(n) => Some(n),
_ => None,
}
}
projects / rust.git / blobdiff