use clippy_utils::diagnostics::{span_lint_and_sugg, span_lint_hir_and_then}; use clippy_utils::eq_expr_value; use clippy_utils::source::snippet_opt; use clippy_utils::ty::{implements_trait, is_type_diagnostic_item}; use if_chain::if_chain; use rustc_ast::ast::LitKind; use rustc_errors::Applicability; use rustc_hir::intravisit::{walk_expr, FnKind, Visitor}; use rustc_hir::{BinOpKind, Body, Expr, ExprKind, FnDecl, UnOp}; use rustc_lint::{LateContext, LateLintPass}; use rustc_session::{declare_lint_pass, declare_tool_lint}; use rustc_span::def_id::LocalDefId; use rustc_span::source_map::Span; use rustc_span::sym; declare_clippy_lint! { /// ### What it does /// Checks for boolean expressions that can be written more /// concisely. /// /// ### Why is this bad? /// Readability of boolean expressions suffers from /// unnecessary duplication. /// /// ### Known problems /// Ignores short circuiting behavior of `||` and /// `&&`. Ignores `|`, `&` and `^`. /// /// ### Example /// ```ignore /// if a && true {} /// if !(a == b) {} /// ``` /// /// Use instead: /// ```rust,ignore /// if a {} /// if a != b {} /// ``` #[clippy::version = "pre 1.29.0"] pub NONMINIMAL_BOOL, complexity, "boolean expressions that can be written more concisely" } declare_clippy_lint! { /// ### What it does /// Checks for boolean expressions that contain terminals that /// can be eliminated. /// /// ### Why is this bad? /// This is most likely a logic bug. /// /// ### Known problems /// Ignores short circuiting behavior. /// /// ### Example /// ```rust,ignore /// // The `b` is unnecessary, the expression is equivalent to `if a`. /// if a && b || a { ... } /// ``` /// /// Use instead: /// ```rust,ignore /// if a {} /// ``` #[clippy::version = "pre 1.29.0"] pub OVERLY_COMPLEX_BOOL_EXPR, correctness, "boolean expressions that contain terminals which can be eliminated" } // For each pairs, both orders are considered. const METHODS_WITH_NEGATION: [(&str, &str); 2] = [("is_some", "is_none"), ("is_err", "is_ok")]; declare_lint_pass!(NonminimalBool => [NONMINIMAL_BOOL, OVERLY_COMPLEX_BOOL_EXPR]); impl<'tcx> LateLintPass<'tcx> for NonminimalBool { fn check_fn( &mut self, cx: &LateContext<'tcx>, _: FnKind<'tcx>, _: &'tcx FnDecl<'_>, body: &'tcx Body<'_>, _: Span, _: LocalDefId, ) { NonminimalBoolVisitor { cx }.visit_body(body); } } struct NonminimalBoolVisitor<'a, 'tcx> { cx: &'a LateContext<'tcx>, } use quine_mc_cluskey::Bool; struct Hir2Qmm<'a, 'tcx, 'v> { terminals: Vec<&'v Expr<'v>>, cx: &'a LateContext<'tcx>, } impl<'a, 'tcx, 'v> Hir2Qmm<'a, 'tcx, 'v> { fn extract(&mut self, op: BinOpKind, a: &[&'v Expr<'_>], mut v: Vec) -> Result, String> { for a in a { if let ExprKind::Binary(binop, lhs, rhs) = &a.kind { if binop.node == op { v = self.extract(op, &[lhs, rhs], v)?; continue; } } v.push(self.run(a)?); } Ok(v) } fn run(&mut self, e: &'v Expr<'_>) -> Result { fn negate(bin_op_kind: BinOpKind) -> Option { match bin_op_kind { BinOpKind::Eq => Some(BinOpKind::Ne), BinOpKind::Ne => Some(BinOpKind::Eq), BinOpKind::Gt => Some(BinOpKind::Le), BinOpKind::Ge => Some(BinOpKind::Lt), BinOpKind::Lt => Some(BinOpKind::Ge), BinOpKind::Le => Some(BinOpKind::Gt), _ => None, } } // prevent folding of `cfg!` macros and the like if !e.span.from_expansion() { match &e.kind { ExprKind::Unary(UnOp::Not, inner) => return Ok(Bool::Not(Box::new(self.run(inner)?))), ExprKind::Binary(binop, lhs, rhs) => match &binop.node { BinOpKind::Or => { return Ok(Bool::Or(self.extract(BinOpKind::Or, &[lhs, rhs], Vec::new())?)); }, BinOpKind::And => { return Ok(Bool::And(self.extract(BinOpKind::And, &[lhs, rhs], Vec::new())?)); }, _ => (), }, ExprKind::Lit(lit) => match lit.node { LitKind::Bool(true) => return Ok(Bool::True), LitKind::Bool(false) => return Ok(Bool::False), _ => (), }, _ => (), } } for (n, expr) in self.terminals.iter().enumerate() { if eq_expr_value(self.cx, e, expr) { #[expect(clippy::cast_possible_truncation)] return Ok(Bool::Term(n as u8)); } if_chain! { if let ExprKind::Binary(e_binop, e_lhs, e_rhs) = &e.kind; if implements_ord(self.cx, e_lhs); if let ExprKind::Binary(expr_binop, expr_lhs, expr_rhs) = &expr.kind; if negate(e_binop.node) == Some(expr_binop.node); if eq_expr_value(self.cx, e_lhs, expr_lhs); if eq_expr_value(self.cx, e_rhs, expr_rhs); then { #[expect(clippy::cast_possible_truncation)] return Ok(Bool::Not(Box::new(Bool::Term(n as u8)))); } } } let n = self.terminals.len(); self.terminals.push(e); if n < 32 { #[expect(clippy::cast_possible_truncation)] Ok(Bool::Term(n as u8)) } else { Err("too many literals".to_owned()) } } } struct SuggestContext<'a, 'tcx, 'v> { terminals: &'v [&'v Expr<'v>], cx: &'a LateContext<'tcx>, output: String, } impl<'a, 'tcx, 'v> SuggestContext<'a, 'tcx, 'v> { fn recurse(&mut self, suggestion: &Bool) -> Option<()> { use quine_mc_cluskey::Bool::{And, False, Not, Or, Term, True}; match suggestion { True => { self.output.push_str("true"); }, False => { self.output.push_str("false"); }, Not(inner) => match **inner { And(_) | Or(_) => { self.output.push('!'); self.output.push('('); self.recurse(inner); self.output.push(')'); }, Term(n) => { let terminal = self.terminals[n as usize]; if let Some(str) = simplify_not(self.cx, terminal) { self.output.push_str(&str); } else { self.output.push('!'); let snip = snippet_opt(self.cx, terminal.span)?; self.output.push_str(&snip); } }, True | False | Not(_) => { self.output.push('!'); self.recurse(inner)?; }, }, And(v) => { for (index, inner) in v.iter().enumerate() { if index > 0 { self.output.push_str(" && "); } if let Or(_) = *inner { self.output.push('('); self.recurse(inner); self.output.push(')'); } else { self.recurse(inner); } } }, Or(v) => { for (index, inner) in v.iter().rev().enumerate() { if index > 0 { self.output.push_str(" || "); } self.recurse(inner); } }, &Term(n) => { let snip = snippet_opt(self.cx, self.terminals[n as usize].span.source_callsite())?; self.output.push_str(&snip); }, } Some(()) } } fn simplify_not(cx: &LateContext<'_>, expr: &Expr<'_>) -> Option { match &expr.kind { ExprKind::Binary(binop, lhs, rhs) => { if !implements_ord(cx, lhs) { return None; } match binop.node { BinOpKind::Eq => Some(" != "), BinOpKind::Ne => Some(" == "), BinOpKind::Lt => Some(" >= "), BinOpKind::Gt => Some(" <= "), BinOpKind::Le => Some(" > "), BinOpKind::Ge => Some(" < "), _ => None, } .and_then(|op| { Some(format!( "{}{op}{}", snippet_opt(cx, lhs.span)?, snippet_opt(cx, rhs.span)? )) }) }, ExprKind::MethodCall(path, receiver, [], _) => { let type_of_receiver = cx.typeck_results().expr_ty(receiver); if !is_type_diagnostic_item(cx, type_of_receiver, sym::Option) && !is_type_diagnostic_item(cx, type_of_receiver, sym::Result) { return None; } METHODS_WITH_NEGATION .iter() .copied() .flat_map(|(a, b)| vec![(a, b), (b, a)]) .find(|&(a, _)| { let path: &str = path.ident.name.as_str(); a == path }) .and_then(|(_, neg_method)| Some(format!("{}.{neg_method}()", snippet_opt(cx, receiver.span)?))) }, _ => None, } } fn suggest(cx: &LateContext<'_>, suggestion: &Bool, terminals: &[&Expr<'_>]) -> String { let mut suggest_context = SuggestContext { terminals, cx, output: String::new(), }; suggest_context.recurse(suggestion); suggest_context.output } fn simple_negate(b: Bool) -> Bool { use quine_mc_cluskey::Bool::{And, False, Not, Or, Term, True}; match b { True => False, False => True, t @ Term(_) => Not(Box::new(t)), And(mut v) => { for el in &mut v { *el = simple_negate(::std::mem::replace(el, True)); } Or(v) }, Or(mut v) => { for el in &mut v { *el = simple_negate(::std::mem::replace(el, True)); } And(v) }, Not(inner) => *inner, } } #[derive(Default)] struct Stats { terminals: [usize; 32], negations: usize, ops: usize, } fn terminal_stats(b: &Bool) -> Stats { fn recurse(b: &Bool, stats: &mut Stats) { match b { True | False => stats.ops += 1, Not(inner) => { match **inner { And(_) | Or(_) => stats.ops += 1, // brackets are also operations _ => stats.negations += 1, } recurse(inner, stats); }, And(v) | Or(v) => { stats.ops += v.len() - 1; for inner in v { recurse(inner, stats); } }, &Term(n) => stats.terminals[n as usize] += 1, } } use quine_mc_cluskey::Bool::{And, False, Not, Or, Term, True}; let mut stats = Stats::default(); recurse(b, &mut stats); stats } impl<'a, 'tcx> NonminimalBoolVisitor<'a, 'tcx> { fn bool_expr(&self, e: &'tcx Expr<'_>) { let mut h2q = Hir2Qmm { terminals: Vec::new(), cx: self.cx, }; if let Ok(expr) = h2q.run(e) { if h2q.terminals.len() > 8 { // QMC has exponentially slow behavior as the number of terminals increases // 8 is reasonable, it takes approximately 0.2 seconds. // See #825 return; } let stats = terminal_stats(&expr); let mut simplified = expr.simplify(); for simple in Bool::Not(Box::new(expr)).simplify() { match simple { Bool::Not(_) | Bool::True | Bool::False => {}, _ => simplified.push(Bool::Not(Box::new(simple.clone()))), } let simple_negated = simple_negate(simple); if simplified.iter().any(|s| *s == simple_negated) { continue; } simplified.push(simple_negated); } let mut improvements = Vec::with_capacity(simplified.len()); 'simplified: for suggestion in &simplified { let simplified_stats = terminal_stats(suggestion); let mut improvement = false; for i in 0..32 { // ignore any "simplifications" that end up requiring a terminal more often // than in the original expression if stats.terminals[i] < simplified_stats.terminals[i] { continue 'simplified; } if stats.terminals[i] != 0 && simplified_stats.terminals[i] == 0 { span_lint_hir_and_then( self.cx, OVERLY_COMPLEX_BOOL_EXPR, e.hir_id, e.span, "this boolean expression contains a logic bug", |diag| { diag.span_help( h2q.terminals[i].span, "this expression can be optimized out by applying boolean operations to the \ outer expression", ); diag.span_suggestion( e.span, "it would look like the following", suggest(self.cx, suggestion, &h2q.terminals), // nonminimal_bool can produce minimal but // not human readable expressions (#3141) Applicability::Unspecified, ); }, ); // don't also lint `NONMINIMAL_BOOL` return; } // if the number of occurrences of a terminal decreases or any of the stats // decreases while none increases improvement |= (stats.terminals[i] > simplified_stats.terminals[i]) || (stats.negations > simplified_stats.negations && stats.ops == simplified_stats.ops) || (stats.ops > simplified_stats.ops && stats.negations == simplified_stats.negations); } if improvement { improvements.push(suggestion); } } let nonminimal_bool_lint = |suggestions: Vec<_>| { span_lint_hir_and_then( self.cx, NONMINIMAL_BOOL, e.hir_id, e.span, "this boolean expression can be simplified", |diag| { diag.span_suggestions( e.span, "try", suggestions.into_iter(), // nonminimal_bool can produce minimal but // not human readable expressions (#3141) Applicability::Unspecified, ); }, ); }; if improvements.is_empty() { let mut visitor = NotSimplificationVisitor { cx: self.cx }; visitor.visit_expr(e); } else { nonminimal_bool_lint( improvements .into_iter() .map(|suggestion| suggest(self.cx, suggestion, &h2q.terminals)) .collect(), ); } } } } impl<'a, 'tcx> Visitor<'tcx> for NonminimalBoolVisitor<'a, 'tcx> { fn visit_expr(&mut self, e: &'tcx Expr<'_>) { if !e.span.from_expansion() { match &e.kind { ExprKind::Binary(binop, _, _) if binop.node == BinOpKind::Or || binop.node == BinOpKind::And => { self.bool_expr(e); }, ExprKind::Unary(UnOp::Not, inner) => { if self.cx.typeck_results().node_types()[inner.hir_id].is_bool() { self.bool_expr(e); } }, _ => {}, } } walk_expr(self, e); } } fn implements_ord(cx: &LateContext<'_>, expr: &Expr<'_>) -> bool { let ty = cx.typeck_results().expr_ty(expr); cx.tcx .get_diagnostic_item(sym::Ord) .map_or(false, |id| implements_trait(cx, ty, id, &[])) } struct NotSimplificationVisitor<'a, 'tcx> { cx: &'a LateContext<'tcx>, } impl<'a, 'tcx> Visitor<'tcx> for NotSimplificationVisitor<'a, 'tcx> { fn visit_expr(&mut self, expr: &'tcx Expr<'_>) { if let ExprKind::Unary(UnOp::Not, inner) = &expr.kind { if let Some(suggestion) = simplify_not(self.cx, inner) { span_lint_and_sugg( self.cx, NONMINIMAL_BOOL, expr.span, "this boolean expression can be simplified", "try", suggestion, Applicability::MachineApplicable, ); } } walk_expr(self, expr); } }