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Diffstat (limited to '')
-rw-r--r-- | src/tools/clippy/clippy_lints/src/implicit_saturating_add.rs | 114 |
1 files changed, 114 insertions, 0 deletions
diff --git a/src/tools/clippy/clippy_lints/src/implicit_saturating_add.rs b/src/tools/clippy/clippy_lints/src/implicit_saturating_add.rs new file mode 100644 index 000000000..bf1351829 --- /dev/null +++ b/src/tools/clippy/clippy_lints/src/implicit_saturating_add.rs @@ -0,0 +1,114 @@ +use clippy_utils::consts::{constant, Constant}; +use clippy_utils::diagnostics::span_lint_and_sugg; +use clippy_utils::get_parent_expr; +use clippy_utils::source::snippet_with_applicability; +use if_chain::if_chain; +use rustc_ast::ast::{LitIntType, LitKind}; +use rustc_errors::Applicability; +use rustc_hir::{BinOpKind, Block, Expr, ExprKind, Stmt, StmtKind}; +use rustc_lint::{LateContext, LateLintPass}; +use rustc_middle::ty::{Int, IntTy, Ty, Uint, UintTy}; +use rustc_session::{declare_lint_pass, declare_tool_lint}; + +declare_clippy_lint! { + /// ### What it does + /// Checks for implicit saturating addition. + /// + /// ### Why is this bad? + /// The built-in function is more readable and may be faster. + /// + /// ### Example + /// ```rust + ///let mut u:u32 = 7000; + /// + /// if u != u32::MAX { + /// u += 1; + /// } + /// ``` + /// Use instead: + /// ```rust + ///let mut u:u32 = 7000; + /// + /// u = u.saturating_add(1); + /// ``` + #[clippy::version = "1.65.0"] + pub IMPLICIT_SATURATING_ADD, + style, + "Perform saturating addition instead of implicitly checking max bound of data type" +} +declare_lint_pass!(ImplicitSaturatingAdd => [IMPLICIT_SATURATING_ADD]); + +impl<'tcx> LateLintPass<'tcx> for ImplicitSaturatingAdd { + fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'tcx>) { + if_chain! { + if let ExprKind::If(cond, then, None) = expr.kind; + if let ExprKind::DropTemps(expr1) = cond.kind; + if let Some((c, op_node, l)) = get_const(cx, expr1); + if let BinOpKind::Ne | BinOpKind::Lt = op_node; + if let ExprKind::Block(block, None) = then.kind; + if let Block { + stmts: + [Stmt + { kind: StmtKind::Expr(ex) | StmtKind::Semi(ex), .. }], + expr: None, ..} | + Block { stmts: [], expr: Some(ex), ..} = block; + if let ExprKind::AssignOp(op1, target, value) = ex.kind; + let ty = cx.typeck_results().expr_ty(target); + if Some(c) == get_int_max(ty); + if clippy_utils::SpanlessEq::new(cx).eq_expr(l, target); + if BinOpKind::Add == op1.node; + if let ExprKind::Lit(ref lit) = value.kind; + if let LitKind::Int(1, LitIntType::Unsuffixed) = lit.node; + if block.expr.is_none(); + then { + let mut app = Applicability::MachineApplicable; + let code = snippet_with_applicability(cx, target.span, "_", &mut app); + let sugg = if let Some(parent) = get_parent_expr(cx, expr) && let ExprKind::If(_cond, _then, Some(else_)) = parent.kind && else_.hir_id == expr.hir_id {format!("{{{code} = {code}.saturating_add(1); }}")} else {format!("{code} = {code}.saturating_add(1);")}; + span_lint_and_sugg(cx, IMPLICIT_SATURATING_ADD, expr.span, "manual saturating add detected", "use instead", sugg, app); + } + } + } +} + +fn get_int_max(ty: Ty<'_>) -> Option<u128> { + match ty.peel_refs().kind() { + Int(IntTy::I8) => i8::max_value().try_into().ok(), + Int(IntTy::I16) => i16::max_value().try_into().ok(), + Int(IntTy::I32) => i32::max_value().try_into().ok(), + Int(IntTy::I64) => i64::max_value().try_into().ok(), + Int(IntTy::I128) => i128::max_value().try_into().ok(), + Int(IntTy::Isize) => isize::max_value().try_into().ok(), + Uint(UintTy::U8) => u8::max_value().try_into().ok(), + Uint(UintTy::U16) => u16::max_value().try_into().ok(), + Uint(UintTy::U32) => u32::max_value().try_into().ok(), + Uint(UintTy::U64) => u64::max_value().try_into().ok(), + Uint(UintTy::U128) => Some(u128::max_value()), + Uint(UintTy::Usize) => usize::max_value().try_into().ok(), + _ => None, + } +} + +fn get_const<'tcx>(cx: &LateContext<'tcx>, expr: &Expr<'tcx>) -> Option<(u128, BinOpKind, &'tcx Expr<'tcx>)> { + if let ExprKind::Binary(op, l, r) = expr.kind { + let tr = cx.typeck_results(); + if let Some((Constant::Int(c), _)) = constant(cx, tr, r) { + return Some((c, op.node, l)); + }; + if let Some((Constant::Int(c), _)) = constant(cx, tr, l) { + return Some((c, invert_op(op.node)?, r)); + } + } + None +} + +fn invert_op(op: BinOpKind) -> Option<BinOpKind> { + use rustc_hir::BinOpKind::{Ge, Gt, Le, Lt, Ne}; + match op { + Lt => Some(Gt), + Le => Some(Ge), + Ne => Some(Ne), + Ge => Some(Le), + Gt => Some(Lt), + _ => None, + } +} |