diff --git a/clippy_lints/src/implicit_saturating_sub.rs b/clippy_lints/src/implicit_saturating_sub.rs index 127c73ed6..453ff09bf 100644 --- a/clippy_lints/src/implicit_saturating_sub.rs +++ b/clippy_lints/src/implicit_saturating_sub.rs @@ -1,11 +1,13 @@ -use clippy_utils::diagnostics::span_lint_and_sugg; -use clippy_utils::{higher, is_integer_literal, peel_blocks_with_stmt, SpanlessEq}; +use clippy_utils::diagnostics::{span_lint_and_sugg, span_lint_and_then}; +use clippy_utils::source::snippet_opt; +use clippy_utils::{higher, is_integer_literal, path_to_local, peel_blocks, peel_blocks_with_stmt, SpanlessEq}; use rustc_ast::ast::LitKind; use rustc_data_structures::packed::Pu128; use rustc_errors::Applicability; -use rustc_hir::{BinOpKind, Expr, ExprKind, QPath}; +use rustc_hir::{BinOp, BinOpKind, Expr, ExprKind, HirId, QPath}; use rustc_lint::{LateContext, LateLintPass}; use rustc_session::declare_lint_pass; +use rustc_span::Span; declare_clippy_lint! { /// ### What it does @@ -50,73 +52,229 @@ impl<'tcx> LateLintPass<'tcx> for ImplicitSaturatingSub { // Check if the conditional expression is a binary operation && let ExprKind::Binary(ref cond_op, cond_left, cond_right) = cond.kind - - // Ensure that the binary operator is >, !=, or < - && (BinOpKind::Ne == cond_op.node || BinOpKind::Gt == cond_op.node || BinOpKind::Lt == cond_op.node) - - // Check if assign operation is done - && let Some(target) = subtracts_one(cx, then) - - // Extracting out the variable name - && let ExprKind::Path(QPath::Resolved(_, ares_path)) = target.kind { - // Handle symmetric conditions in the if statement - let (cond_var, cond_num_val) = if SpanlessEq::new(cx).eq_expr(cond_left, target) { - if BinOpKind::Gt == cond_op.node || BinOpKind::Ne == cond_op.node { - (cond_left, cond_right) - } else { - return; - } - } else if SpanlessEq::new(cx).eq_expr(cond_right, target) { - if BinOpKind::Lt == cond_op.node || BinOpKind::Ne == cond_op.node { - (cond_right, cond_left) - } else { - return; - } + check_with_condition(cx, expr, cond_op.node, cond_left, cond_right, then); + } else if let Some(higher::If { + cond, + then: if_block, + r#else: Some(else_block), + }) = higher::If::hir(expr) + && let ExprKind::Binary(ref cond_op, cond_left, cond_right) = cond.kind + { + check_manual_check(cx, expr, cond_op, cond_left, cond_right, if_block, else_block); + } + } +} + +fn check_manual_check<'tcx>( + cx: &LateContext<'tcx>, + expr: &Expr<'tcx>, + condition: &BinOp, + left_hand: &Expr<'tcx>, + right_hand: &Expr<'tcx>, + if_block: &Expr<'tcx>, + else_block: &Expr<'tcx>, +) { + let ty = cx.typeck_results().expr_ty(left_hand); + if ty.is_numeric() && !ty.is_signed() { + match condition.node { + BinOpKind::Gt | BinOpKind::Ge => check_gt( + cx, + condition.span, + expr.span, + left_hand, + right_hand, + if_block, + else_block, + ), + BinOpKind::Lt | BinOpKind::Le => check_gt( + cx, + condition.span, + expr.span, + right_hand, + left_hand, + if_block, + else_block, + ), + _ => {}, + } + } +} + +fn check_gt( + cx: &LateContext<'_>, + condition_span: Span, + expr_span: Span, + big_var: &Expr<'_>, + little_var: &Expr<'_>, + if_block: &Expr<'_>, + else_block: &Expr<'_>, +) { + if let Some(big_var) = Var::new(big_var) + && let Some(little_var) = Var::new(little_var) + { + check_subtraction(cx, condition_span, expr_span, big_var, little_var, if_block, else_block); + } +} + +struct Var { + span: Span, + hir_id: HirId, +} + +impl Var { + fn new(expr: &Expr<'_>) -> Option { + path_to_local(expr).map(|hir_id| Self { + span: expr.span, + hir_id, + }) + } +} + +fn check_subtraction( + cx: &LateContext<'_>, + condition_span: Span, + expr_span: Span, + big_var: Var, + little_var: Var, + if_block: &Expr<'_>, + else_block: &Expr<'_>, +) { + let if_block = peel_blocks(if_block); + let else_block = peel_blocks(else_block); + if is_integer_literal(if_block, 0) { + // We need to check this case as well to prevent infinite recursion. + if is_integer_literal(else_block, 0) { + // Well, seems weird but who knows? + return; + } + // If the subtraction is done in the `else` block, then we need to also revert the two + // variables as it means that the check was reverted too. + check_subtraction(cx, condition_span, expr_span, little_var, big_var, else_block, if_block); + return; + } + if is_integer_literal(else_block, 0) + && let ExprKind::Binary(op, left, right) = if_block.kind + && let BinOpKind::Sub = op.node + { + let local_left = path_to_local(left); + let local_right = path_to_local(right); + if Some(big_var.hir_id) == local_left && Some(little_var.hir_id) == local_right { + // This part of the condition is voluntarily split from the one before to ensure that + // if `snippet_opt` fails, it won't try the next conditions. + if let Some(big_var_snippet) = snippet_opt(cx, big_var.span) + && let Some(little_var_snippet) = snippet_opt(cx, little_var.span) + { + span_lint_and_sugg( + cx, + IMPLICIT_SATURATING_SUB, + expr_span, + "manual arithmetic check found", + "replace it with", + format!("{big_var_snippet}.saturating_sub({little_var_snippet})"), + Applicability::MachineApplicable, + ); + } + } else if Some(little_var.hir_id) == local_left + && Some(big_var.hir_id) == local_right + && let Some(big_var_snippet) = snippet_opt(cx, big_var.span) + && let Some(little_var_snippet) = snippet_opt(cx, little_var.span) + { + span_lint_and_then( + cx, + IMPLICIT_SATURATING_SUB, + condition_span, + "inverted arithmetic check before subtraction", + |diag| { + diag.span_note( + if_block.span, + format!("this subtraction underflows when `{little_var_snippet} < {big_var_snippet}`"), + ); + diag.span_suggestion( + if_block.span, + "try replacing it with", + format!("{big_var_snippet} - {little_var_snippet}"), + Applicability::MaybeIncorrect, + ); + }, + ); + } + } +} + +fn check_with_condition<'tcx>( + cx: &LateContext<'tcx>, + expr: &Expr<'tcx>, + cond_op: BinOpKind, + cond_left: &Expr<'tcx>, + cond_right: &Expr<'tcx>, + then: &Expr<'tcx>, +) { + // Ensure that the binary operator is >, !=, or < + if (BinOpKind::Ne == cond_op || BinOpKind::Gt == cond_op || BinOpKind::Lt == cond_op) + + // Check if assign operation is done + && let Some(target) = subtracts_one(cx, then) + + // Extracting out the variable name + && let ExprKind::Path(QPath::Resolved(_, ares_path)) = target.kind + { + // Handle symmetric conditions in the if statement + let (cond_var, cond_num_val) = if SpanlessEq::new(cx).eq_expr(cond_left, target) { + if BinOpKind::Gt == cond_op || BinOpKind::Ne == cond_op { + (cond_left, cond_right) } else { return; - }; - - // Check if the variable in the condition statement is an integer - if !cx.typeck_results().expr_ty(cond_var).is_integral() { + } + } else if SpanlessEq::new(cx).eq_expr(cond_right, target) { + if BinOpKind::Lt == cond_op || BinOpKind::Ne == cond_op { + (cond_right, cond_left) + } else { return; } + } else { + return; + }; - // Get the variable name - let var_name = ares_path.segments[0].ident.name.as_str(); - match cond_num_val.kind { - ExprKind::Lit(cond_lit) => { - // Check if the constant is zero - if let LitKind::Int(Pu128(0), _) = cond_lit.node { - if cx.typeck_results().expr_ty(cond_left).is_signed() { - } else { - print_lint_and_sugg(cx, var_name, expr); - }; - } - }, - ExprKind::Path(QPath::TypeRelative(_, name)) => { - if name.ident.as_str() == "MIN" - && let Some(const_id) = cx.typeck_results().type_dependent_def_id(cond_num_val.hir_id) - && let Some(impl_id) = cx.tcx.impl_of_method(const_id) - && let None = cx.tcx.impl_trait_ref(impl_id) // An inherent impl - && cx.tcx.type_of(impl_id).instantiate_identity().is_integral() - { + // Check if the variable in the condition statement is an integer + if !cx.typeck_results().expr_ty(cond_var).is_integral() { + return; + } + + // Get the variable name + let var_name = ares_path.segments[0].ident.name.as_str(); + match cond_num_val.kind { + ExprKind::Lit(cond_lit) => { + // Check if the constant is zero + if let LitKind::Int(Pu128(0), _) = cond_lit.node { + if cx.typeck_results().expr_ty(cond_left).is_signed() { + } else { print_lint_and_sugg(cx, var_name, expr); - } - }, - ExprKind::Call(func, []) => { - if let ExprKind::Path(QPath::TypeRelative(_, name)) = func.kind - && name.ident.as_str() == "min_value" - && let Some(func_id) = cx.typeck_results().type_dependent_def_id(func.hir_id) - && let Some(impl_id) = cx.tcx.impl_of_method(func_id) - && let None = cx.tcx.impl_trait_ref(impl_id) // An inherent impl - && cx.tcx.type_of(impl_id).instantiate_identity().is_integral() - { - print_lint_and_sugg(cx, var_name, expr); - } - }, - _ => (), - } + }; + } + }, + ExprKind::Path(QPath::TypeRelative(_, name)) => { + if name.ident.as_str() == "MIN" + && let Some(const_id) = cx.typeck_results().type_dependent_def_id(cond_num_val.hir_id) + && let Some(impl_id) = cx.tcx.impl_of_method(const_id) + && let None = cx.tcx.impl_trait_ref(impl_id) // An inherent impl + && cx.tcx.type_of(impl_id).instantiate_identity().is_integral() + { + print_lint_and_sugg(cx, var_name, expr); + } + }, + ExprKind::Call(func, []) => { + if let ExprKind::Path(QPath::TypeRelative(_, name)) = func.kind + && name.ident.as_str() == "min_value" + && let Some(func_id) = cx.typeck_results().type_dependent_def_id(func.hir_id) + && let Some(impl_id) = cx.tcx.impl_of_method(func_id) + && let None = cx.tcx.impl_trait_ref(impl_id) // An inherent impl + && cx.tcx.type_of(impl_id).instantiate_identity().is_integral() + { + print_lint_and_sugg(cx, var_name, expr); + } + }, + _ => (), } } }