Add new lint (modulo_arithmetic)
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mgr-inz-rafal
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@ -1186,6 +1186,7 @@ Released 2018-09-13
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[`mixed_case_hex_literals`]: https://rust-lang.github.io/rust-clippy/master/index.html#mixed_case_hex_literals
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[`module_inception`]: https://rust-lang.github.io/rust-clippy/master/index.html#module_inception
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[`module_name_repetitions`]: https://rust-lang.github.io/rust-clippy/master/index.html#module_name_repetitions
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[`modulo_arithmetic`]: https://rust-lang.github.io/rust-clippy/master/index.html#modulo_arithmetic
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[`modulo_one`]: https://rust-lang.github.io/rust-clippy/master/index.html#modulo_one
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[`multiple_crate_versions`]: https://rust-lang.github.io/rust-clippy/master/index.html#multiple_crate_versions
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[`multiple_inherent_impl`]: https://rust-lang.github.io/rust-clippy/master/index.html#multiple_inherent_impl
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@ -6,7 +6,7 @@
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A collection of lints to catch common mistakes and improve your [Rust](https://github.com/rust-lang/rust) code.
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[There are 341 lints included in this crate!](https://rust-lang.github.io/rust-clippy/master/index.html)
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[There are 342 lints included in this crate!](https://rust-lang.github.io/rust-clippy/master/index.html)
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We have a bunch of lint categories to allow you to choose how much Clippy is supposed to ~~annoy~~ help you:
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@ -239,6 +239,7 @@ macro_rules! declare_clippy_lint {
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pub mod missing_const_for_fn;
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pub mod missing_doc;
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pub mod missing_inline;
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pub mod modulo_arithmetic;
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pub mod mul_add;
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pub mod multiple_crate_versions;
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pub mod mut_key;
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@ -667,6 +668,7 @@ pub fn register_plugins(store: &mut lint::LintStore, sess: &Session, conf: &Conf
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&missing_const_for_fn::MISSING_CONST_FOR_FN,
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&missing_doc::MISSING_DOCS_IN_PRIVATE_ITEMS,
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&missing_inline::MISSING_INLINE_IN_PUBLIC_ITEMS,
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&modulo_arithmetic::MODULO_ARITHMETIC,
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&mul_add::MANUAL_MUL_ADD,
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&multiple_crate_versions::MULTIPLE_CRATE_VERSIONS,
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&mut_key::MUTABLE_KEY_TYPE,
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@ -943,6 +945,7 @@ pub fn register_plugins(store: &mut lint::LintStore, sess: &Session, conf: &Conf
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store.register_late_pass(|| box comparison_chain::ComparisonChain);
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store.register_late_pass(|| box mul_add::MulAddCheck);
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store.register_late_pass(|| box mut_key::MutableKeyType);
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store.register_late_pass(|| box modulo_arithmetic::ModuloArithmetic);
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store.register_early_pass(|| box reference::DerefAddrOf);
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store.register_early_pass(|| box reference::RefInDeref);
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store.register_early_pass(|| box double_parens::DoubleParens);
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@ -1003,6 +1006,7 @@ pub fn register_plugins(store: &mut lint::LintStore, sess: &Session, conf: &Conf
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LintId::of(&misc::FLOAT_CMP_CONST),
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LintId::of(&missing_doc::MISSING_DOCS_IN_PRIVATE_ITEMS),
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LintId::of(&missing_inline::MISSING_INLINE_IN_PUBLIC_ITEMS),
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LintId::of(&modulo_arithmetic::MODULO_ARITHMETIC),
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LintId::of(&panic_unimplemented::PANIC),
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LintId::of(&panic_unimplemented::TODO),
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LintId::of(&panic_unimplemented::UNIMPLEMENTED),
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149
clippy_lints/src/modulo_arithmetic.rs
Normal file
149
clippy_lints/src/modulo_arithmetic.rs
Normal file
@ -0,0 +1,149 @@
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use crate::consts::{constant, Constant};
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use crate::utils::{sext, span_lint_and_then};
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use if_chain::if_chain;
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use rustc::declare_lint_pass;
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use rustc::hir::*;
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use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
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use rustc::ty::{self};
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use rustc_session::declare_tool_lint;
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use std::fmt::Display;
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declare_clippy_lint! {
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/// **What it does:** Checks for modulo arithemtic.
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///
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/// **Why is this bad?** The results of modulo (%) operation might differ
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/// depending on the language, when negative numbers are involved.
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/// If you interop with different languages it might be beneficial
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/// to double check all places that use modulo arithmetic.
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///
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/// For example, in Rust `17 % -3 = 2`, but in Python `17 % -3 = -1`.
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///
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/// **Known problems:** None.
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///
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/// **Example:**
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/// ```rust
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/// let x = -17 % 3;
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/// ```
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pub MODULO_ARITHMETIC,
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restriction,
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"any modulo arithmetic statement"
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}
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declare_lint_pass!(ModuloArithmetic => [MODULO_ARITHMETIC]);
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struct OperandInfo {
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string_representation: Option<String>,
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is_negative: bool,
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is_integral: bool,
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}
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fn analyze_operand(operand: &Expr, cx: &LateContext<'_, '_>, expr: &Expr) -> Option<OperandInfo> {
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match constant(cx, cx.tables, operand) {
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Some((Constant::Int(v), _)) => match cx.tables.expr_ty(expr).kind {
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ty::Int(ity) => {
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let value = sext(cx.tcx, v, ity);
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return Some(OperandInfo {
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string_representation: Some(value.to_string()),
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is_negative: value < 0,
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is_integral: true,
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});
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},
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ty::Uint(_) => {
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return Some(OperandInfo {
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string_representation: None,
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is_negative: false,
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is_integral: true,
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});
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},
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_ => {},
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},
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Some((Constant::F32(f), _)) => {
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return Some(floating_point_operand_info(&f));
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},
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Some((Constant::F64(f), _)) => {
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return Some(floating_point_operand_info(&f));
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},
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_ => {},
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}
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None
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}
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fn floating_point_operand_info<T: Display + PartialOrd + From<f32>>(f: &T) -> OperandInfo {
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OperandInfo {
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string_representation: Some(format!("{:.3}", *f)),
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is_negative: *f < 0.0.into(),
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is_integral: false,
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}
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}
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fn might_have_negative_value(t: &ty::TyS<'_>) -> bool {
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t.is_signed() || t.is_floating_point()
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}
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fn check_const_operands<'a, 'tcx>(
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cx: &LateContext<'a, 'tcx>,
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expr: &'tcx Expr,
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lhs_operand: &OperandInfo,
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rhs_operand: &OperandInfo,
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) {
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if lhs_operand.is_negative ^ rhs_operand.is_negative {
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span_lint_and_then(
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cx,
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MODULO_ARITHMETIC,
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expr.span,
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&format!(
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"you are using modulo operator on constants with different signs: `{} % {}`",
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lhs_operand.string_representation.as_ref().unwrap(),
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rhs_operand.string_representation.as_ref().unwrap()
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),
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|db| {
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db.note("double check for expected result especially when interoperating with different languages");
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if lhs_operand.is_integral {
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db.note("or consider using `rem_euclid` or similar function");
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}
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},
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);
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}
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}
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fn check_non_const_operands<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr, operand: &Expr) {
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let operand_type = cx.tables.expr_ty(operand);
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if might_have_negative_value(operand_type) {
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span_lint_and_then(
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cx,
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MODULO_ARITHMETIC,
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expr.span,
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"you are using modulo operator on types that might have different signs",
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|db| {
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db.note("double check for expected result especially when interoperating with different languages");
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if operand_type.is_integral() {
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db.note("or consider using `rem_euclid` or similar function");
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}
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},
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);
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}
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}
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impl<'a, 'tcx> LateLintPass<'a, 'tcx> for ModuloArithmetic {
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fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
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match &expr.kind {
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ExprKind::Binary(op, lhs, rhs) | ExprKind::AssignOp(op, lhs, rhs) => {
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if let BinOpKind::Rem = op.node {
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let lhs_operand = analyze_operand(lhs, cx, expr);
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let rhs_operand = analyze_operand(rhs, cx, expr);
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if_chain! {
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if let Some(lhs_operand) = lhs_operand;
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if let Some(rhs_operand) = rhs_operand;
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then {
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check_const_operands(cx, expr, &lhs_operand, &rhs_operand);
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}
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else {
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check_non_const_operands(cx, expr, lhs);
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}
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}
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};
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},
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_ => {},
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}
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}
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}
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@ -6,7 +6,7 @@
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pub use lint::LINT_LEVELS;
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// begin lint list, do not remove this comment, it’s used in `update_lints`
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pub const ALL_LINTS: [Lint; 341] = [
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pub const ALL_LINTS: [Lint; 342] = [
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Lint {
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name: "absurd_extreme_comparisons",
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group: "correctness",
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@ -1183,6 +1183,13 @@
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deprecation: None,
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module: "enum_variants",
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},
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Lint {
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name: "modulo_arithmetic",
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group: "restriction",
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desc: "any modulo arithmetic statement",
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deprecation: None,
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module: "modulo_arithmetic",
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},
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Lint {
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name: "modulo_one",
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group: "correctness",
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