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Diffstat (limited to '')
| -rw-r--r-- | src/tools/clippy/clippy_lints/src/operators/arithmetic_side_effects.rs | 173 |
1 files changed, 173 insertions, 0 deletions
diff --git a/src/tools/clippy/clippy_lints/src/operators/arithmetic_side_effects.rs b/src/tools/clippy/clippy_lints/src/operators/arithmetic_side_effects.rs new file mode 100644 index 000000000..83b69fbb3 --- /dev/null +++ b/src/tools/clippy/clippy_lints/src/operators/arithmetic_side_effects.rs @@ -0,0 +1,173 @@ +#![allow( + // False positive + clippy::match_same_arms +)] + +use super::ARITHMETIC_SIDE_EFFECTS; +use clippy_utils::{consts::constant_simple, diagnostics::span_lint}; +use rustc_ast as ast; +use rustc_data_structures::fx::FxHashSet; +use rustc_hir as hir; +use rustc_lint::{LateContext, LateLintPass}; +use rustc_middle::ty::Ty; +use rustc_session::impl_lint_pass; +use rustc_span::source_map::{Span, Spanned}; + +const HARD_CODED_ALLOWED: &[&str] = &[ + "f32", + "f64", + "std::num::Saturating", + "std::string::String", + "std::num::Wrapping", +]; + +#[derive(Debug)] +pub struct ArithmeticSideEffects { + allowed: FxHashSet<String>, + // Used to check whether expressions are constants, such as in enum discriminants and consts + const_span: Option<Span>, + expr_span: Option<Span>, +} + +impl_lint_pass!(ArithmeticSideEffects => [ARITHMETIC_SIDE_EFFECTS]); + +impl ArithmeticSideEffects { + #[must_use] + pub fn new(mut allowed: FxHashSet<String>) -> Self { + allowed.extend(HARD_CODED_ALLOWED.iter().copied().map(String::from)); + Self { + allowed, + const_span: None, + expr_span: None, + } + } + + /// Checks assign operators (+=, -=, *=, /=) of integers in a non-constant environment that + /// won't overflow. + fn has_valid_assign_op(op: &Spanned<hir::BinOpKind>, rhs: &hir::Expr<'_>, rhs_refs: Ty<'_>) -> bool { + if !Self::is_literal_integer(rhs, rhs_refs) { + return false; + } + if let hir::BinOpKind::Div | hir::BinOpKind::Mul = op.node + && let hir::ExprKind::Lit(ref lit) = rhs.kind + && let ast::LitKind::Int(1, _) = lit.node + { + return true; + } + false + } + + /// Checks "raw" binary operators (+, -, *, /) of integers in a non-constant environment + /// already handled by the CTFE. + fn has_valid_bin_op(lhs: &hir::Expr<'_>, lhs_refs: Ty<'_>, rhs: &hir::Expr<'_>, rhs_refs: Ty<'_>) -> bool { + Self::is_literal_integer(lhs, lhs_refs) && Self::is_literal_integer(rhs, rhs_refs) + } + + /// Checks if the given `expr` has any of the inner `allowed` elements. + fn is_allowed_ty(&self, cx: &LateContext<'_>, expr: &hir::Expr<'_>) -> bool { + self.allowed.contains( + cx.typeck_results() + .expr_ty(expr) + .to_string() + .split('<') + .next() + .unwrap_or_default(), + ) + } + + /// Explicit integers like `1` or `i32::MAX`. Does not take into consideration references. + fn is_literal_integer(expr: &hir::Expr<'_>, expr_refs: Ty<'_>) -> bool { + let is_integral = expr_refs.is_integral(); + let is_literal = matches!(expr.kind, hir::ExprKind::Lit(_)); + is_integral && is_literal + } + + fn issue_lint(&mut self, cx: &LateContext<'_>, expr: &hir::Expr<'_>) { + span_lint(cx, ARITHMETIC_SIDE_EFFECTS, expr.span, "arithmetic detected"); + self.expr_span = Some(expr.span); + } + + /// Manages when the lint should be triggered. Operations in constant environments, hard coded + /// types, custom allowed types and non-constant operations that won't overflow are ignored. + fn manage_bin_ops( + &mut self, + cx: &LateContext<'_>, + expr: &hir::Expr<'_>, + op: &Spanned<hir::BinOpKind>, + lhs: &hir::Expr<'_>, + rhs: &hir::Expr<'_>, + ) { + if constant_simple(cx, cx.typeck_results(), expr).is_some() { + return; + } + if !matches!( + op.node, + hir::BinOpKind::Add + | hir::BinOpKind::Sub + | hir::BinOpKind::Mul + | hir::BinOpKind::Div + | hir::BinOpKind::Rem + | hir::BinOpKind::Shl + | hir::BinOpKind::Shr + ) { + return; + }; + if self.is_allowed_ty(cx, lhs) || self.is_allowed_ty(cx, rhs) { + return; + } + let lhs_refs = cx.typeck_results().expr_ty(lhs).peel_refs(); + let rhs_refs = cx.typeck_results().expr_ty(rhs).peel_refs(); + let has_valid_assign_op = Self::has_valid_assign_op(op, rhs, rhs_refs); + if has_valid_assign_op || Self::has_valid_bin_op(lhs, lhs_refs, rhs, rhs_refs) { + return; + } + self.issue_lint(cx, expr); + } +} + +impl<'tcx> LateLintPass<'tcx> for ArithmeticSideEffects { + fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'_>) { + if self.expr_span.is_some() || self.const_span.map_or(false, |sp| sp.contains(expr.span)) { + return; + } + match &expr.kind { + hir::ExprKind::Binary(op, lhs, rhs) | hir::ExprKind::AssignOp(op, lhs, rhs) => { + self.manage_bin_ops(cx, expr, op, lhs, rhs); + }, + hir::ExprKind::Unary(hir::UnOp::Neg, _) => { + if constant_simple(cx, cx.typeck_results(), expr).is_none() { + self.issue_lint(cx, expr); + } + }, + _ => {}, + } + } + + fn check_body(&mut self, cx: &LateContext<'_>, body: &hir::Body<'_>) { + let body_owner = cx.tcx.hir().body_owner(body.id()); + let body_owner_def_id = cx.tcx.hir().local_def_id(body_owner); + let body_owner_kind = cx.tcx.hir().body_owner_kind(body_owner_def_id); + if let hir::BodyOwnerKind::Const | hir::BodyOwnerKind::Static(_) = body_owner_kind { + let body_span = cx.tcx.hir().span_with_body(body_owner); + if let Some(span) = self.const_span && span.contains(body_span) { + return; + } + self.const_span = Some(body_span); + } + } + + fn check_body_post(&mut self, cx: &LateContext<'_>, body: &hir::Body<'_>) { + let body_owner = cx.tcx.hir().body_owner(body.id()); + let body_span = cx.tcx.hir().span(body_owner); + if let Some(span) = self.const_span && span.contains(body_span) { + return; + } + self.const_span = None; + } + + fn check_expr_post(&mut self, _: &LateContext<'tcx>, expr: &'tcx hir::Expr<'_>) { + if Some(expr.span) == self.expr_span { + self.expr_span = None; + } + } +} |