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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,149 @@ | ||
| use crate::consts::{constant, Constant}; | ||
| use crate::utils::{sext, span_lint_and_then}; | ||
| use if_chain::if_chain; | ||
| use rustc::declare_lint_pass; | ||
| use rustc::hir::*; | ||
| use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass}; | ||
| use rustc::ty::{self}; | ||
| use rustc_session::declare_tool_lint; | ||
| use std::fmt::Display; | ||
|
|
||
| declare_clippy_lint! { | ||
| /// **What it does:** Checks for modulo arithemtic. | ||
| /// | ||
| /// **Why is this bad?** The results of modulo (%) operation might differ | ||
| /// depending on the language, when negative numbers are involved. | ||
| /// If you interop with different languages it might be beneficial | ||
| /// to double check all places that use modulo arithmetic. | ||
| /// | ||
| /// For example, in Rust `17 % -3 = 2`, but in Python `17 % -3 = -1`. | ||
| /// | ||
| /// **Known problems:** None. | ||
| /// | ||
| /// **Example:** | ||
| /// ```rust | ||
| /// let x = -17 % 3; | ||
| /// ``` | ||
| pub MODULO_ARITHMETIC, | ||
| restriction, | ||
| "any modulo arithmetic statement" | ||
| } | ||
|
|
||
| declare_lint_pass!(ModuloArithmetic => [MODULO_ARITHMETIC]); | ||
|
|
||
| struct OperandInfo { | ||
| string_representation: Option<String>, | ||
| is_negative: bool, | ||
| is_integral: bool, | ||
| } | ||
|
|
||
| fn analyze_operand(operand: &Expr, cx: &LateContext<'_, '_>, expr: &Expr) -> Option<OperandInfo> { | ||
| match constant(cx, cx.tables, operand) { | ||
| Some((Constant::Int(v), _)) => match cx.tables.expr_ty(expr).kind { | ||
| ty::Int(ity) => { | ||
| let value = sext(cx.tcx, v, ity); | ||
| return Some(OperandInfo { | ||
| string_representation: Some(value.to_string()), | ||
| is_negative: value < 0, | ||
| is_integral: true, | ||
| }); | ||
| }, | ||
| ty::Uint(_) => { | ||
| return Some(OperandInfo { | ||
| string_representation: None, | ||
| is_negative: false, | ||
| is_integral: true, | ||
| }); | ||
| }, | ||
| _ => {}, | ||
| }, | ||
| Some((Constant::F32(f), _)) => { | ||
| return Some(floating_point_operand_info(&f)); | ||
| }, | ||
| Some((Constant::F64(f), _)) => { | ||
| return Some(floating_point_operand_info(&f)); | ||
| }, | ||
| _ => {}, | ||
| } | ||
| None | ||
| } | ||
|
|
||
| fn floating_point_operand_info<T: Display + PartialOrd + From<f32>>(f: &T) -> OperandInfo { | ||
| OperandInfo { | ||
| string_representation: Some(format!("{:.3}", *f)), | ||
| is_negative: *f < 0.0.into(), | ||
| is_integral: false, | ||
| } | ||
| } | ||
|
|
||
| fn might_have_negative_value(t: &ty::TyS<'_>) -> bool { | ||
| t.is_signed() || t.is_floating_point() | ||
| } | ||
|
|
||
| fn check_const_operands<'a, 'tcx>( | ||
| cx: &LateContext<'a, 'tcx>, | ||
| expr: &'tcx Expr, | ||
| lhs_operand: &OperandInfo, | ||
| rhs_operand: &OperandInfo, | ||
| ) { | ||
| if lhs_operand.is_negative ^ rhs_operand.is_negative { | ||
| span_lint_and_then( | ||
| cx, | ||
| MODULO_ARITHMETIC, | ||
| expr.span, | ||
| &format!( | ||
| "you are using modulo operator on constants with different signs: `{} % {}`", | ||
| lhs_operand.string_representation.as_ref().unwrap(), | ||
| rhs_operand.string_representation.as_ref().unwrap() | ||
| ), | ||
| |db| { | ||
| db.note("double check for expected result especially when interoperating with different languages"); | ||
| if lhs_operand.is_integral { | ||
| db.note("or consider using `rem_euclid` or similar function"); | ||
| } | ||
| }, | ||
| ); | ||
| } | ||
| } | ||
|
|
||
| fn check_non_const_operands<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr, operand: &Expr) { | ||
| let operand_type = cx.tables.expr_ty(operand); | ||
| if might_have_negative_value(operand_type) { | ||
| span_lint_and_then( | ||
| cx, | ||
| MODULO_ARITHMETIC, | ||
| expr.span, | ||
| "you are using modulo operator on types that might have different signs", | ||
| |db| { | ||
| db.note("double check for expected result especially when interoperating with different languages"); | ||
| if operand_type.is_integral() { | ||
| db.note("or consider using `rem_euclid` or similar function"); | ||
| } | ||
| }, | ||
| ); | ||
| } | ||
| } | ||
|
|
||
| impl<'a, 'tcx> LateLintPass<'a, 'tcx> for ModuloArithmetic { | ||
| fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) { | ||
| match &expr.kind { | ||
| ExprKind::Binary(op, lhs, rhs) | ExprKind::AssignOp(op, lhs, rhs) => { | ||
| if let BinOpKind::Rem = op.node { | ||
| let lhs_operand = analyze_operand(lhs, cx, expr); | ||
| let rhs_operand = analyze_operand(rhs, cx, expr); | ||
| if_chain! { | ||
| if let Some(lhs_operand) = lhs_operand; | ||
| if let Some(rhs_operand) = rhs_operand; | ||
| then { | ||
| check_const_operands(cx, expr, &lhs_operand, &rhs_operand); | ||
| } | ||
| else { | ||
| check_non_const_operands(cx, expr, lhs); | ||
| } | ||
| } | ||
| }; | ||
| }, | ||
| _ => {}, | ||
| } | ||
| } | ||
| } |
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