1 use clippy_utils::diagnostics::{span_lint_and_sugg, span_lint_and_then};
2 use clippy_utils::source::snippet_opt;
3 use clippy_utils::ty::{implements_trait, is_type_diagnostic_item};
4 use clippy_utils::{eq_expr_value, get_trait_def_id, paths};
5 use if_chain::if_chain;
6 use rustc_ast::ast::LitKind;
7 use rustc_errors::Applicability;
8 use rustc_hir::intravisit::{walk_expr, FnKind, Visitor};
9 use rustc_hir::{BinOpKind, Body, Expr, ExprKind, FnDecl, HirId, UnOp};
10 use rustc_lint::{LateContext, LateLintPass};
11 use rustc_session::{declare_lint_pass, declare_tool_lint};
12 use rustc_span::source_map::Span;
15 declare_clippy_lint! {
17 /// Checks for boolean expressions that can be written more
20 /// ### Why is this bad?
21 /// Readability of boolean expressions suffers from
22 /// unnecessary duplication.
24 /// ### Known problems
25 /// Ignores short circuiting behavior of `||` and
26 /// `&&`. Ignores `|`, `&` and `^`.
30 /// if a && true // should be: if a
31 /// if !(a == b) // should be: if a != b
33 #[clippy::version = "pre 1.29.0"]
36 "boolean expressions that can be written more concisely"
39 declare_clippy_lint! {
41 /// Checks for boolean expressions that contain terminals that
42 /// can be eliminated.
44 /// ### Why is this bad?
45 /// This is most likely a logic bug.
47 /// ### Known problems
48 /// Ignores short circuiting behavior.
52 /// if a && b || a { ... }
54 /// The `b` is unnecessary, the expression is equivalent to `if a`.
55 #[clippy::version = "pre 1.29.0"]
58 "boolean expressions that contain terminals which can be eliminated"
61 // For each pairs, both orders are considered.
62 const METHODS_WITH_NEGATION: [(&str, &str); 2] = [("is_some", "is_none"), ("is_err", "is_ok")];
64 declare_lint_pass!(NonminimalBool => [NONMINIMAL_BOOL, LOGIC_BUG]);
66 impl<'tcx> LateLintPass<'tcx> for NonminimalBool {
69 cx: &LateContext<'tcx>,
76 NonminimalBoolVisitor { cx }.visit_body(body);
80 struct NonminimalBoolVisitor<'a, 'tcx> {
81 cx: &'a LateContext<'tcx>,
84 use quine_mc_cluskey::Bool;
85 struct Hir2Qmm<'a, 'tcx, 'v> {
86 terminals: Vec<&'v Expr<'v>>,
87 cx: &'a LateContext<'tcx>,
90 impl<'a, 'tcx, 'v> Hir2Qmm<'a, 'tcx, 'v> {
91 fn extract(&mut self, op: BinOpKind, a: &[&'v Expr<'_>], mut v: Vec<Bool>) -> Result<Vec<Bool>, String> {
93 if let ExprKind::Binary(binop, lhs, rhs) = &a.kind {
95 v = self.extract(op, &[lhs, rhs], v)?;
104 fn run(&mut self, e: &'v Expr<'_>) -> Result<Bool, String> {
105 fn negate(bin_op_kind: BinOpKind) -> Option<BinOpKind> {
107 BinOpKind::Eq => Some(BinOpKind::Ne),
108 BinOpKind::Ne => Some(BinOpKind::Eq),
109 BinOpKind::Gt => Some(BinOpKind::Le),
110 BinOpKind::Ge => Some(BinOpKind::Lt),
111 BinOpKind::Lt => Some(BinOpKind::Ge),
112 BinOpKind::Le => Some(BinOpKind::Gt),
117 // prevent folding of `cfg!` macros and the like
118 if !e.span.from_expansion() {
120 ExprKind::Unary(UnOp::Not, inner) => return Ok(Bool::Not(Box::new(self.run(inner)?))),
121 ExprKind::Binary(binop, lhs, rhs) => match &binop.node {
123 return Ok(Bool::Or(self.extract(BinOpKind::Or, &[lhs, rhs], Vec::new())?));
126 return Ok(Bool::And(self.extract(BinOpKind::And, &[lhs, rhs], Vec::new())?));
130 ExprKind::Lit(lit) => match lit.node {
131 LitKind::Bool(true) => return Ok(Bool::True),
132 LitKind::Bool(false) => return Ok(Bool::False),
138 for (n, expr) in self.terminals.iter().enumerate() {
139 if eq_expr_value(self.cx, e, expr) {
140 #[allow(clippy::cast_possible_truncation)]
141 return Ok(Bool::Term(n as u8));
145 if let ExprKind::Binary(e_binop, e_lhs, e_rhs) = &e.kind;
146 if implements_ord(self.cx, e_lhs);
147 if let ExprKind::Binary(expr_binop, expr_lhs, expr_rhs) = &expr.kind;
148 if negate(e_binop.node) == Some(expr_binop.node);
149 if eq_expr_value(self.cx, e_lhs, expr_lhs);
150 if eq_expr_value(self.cx, e_rhs, expr_rhs);
152 #[allow(clippy::cast_possible_truncation)]
153 return Ok(Bool::Not(Box::new(Bool::Term(n as u8))));
157 let n = self.terminals.len();
158 self.terminals.push(e);
160 #[allow(clippy::cast_possible_truncation)]
161 Ok(Bool::Term(n as u8))
163 Err("too many literals".to_owned())
168 struct SuggestContext<'a, 'tcx, 'v> {
169 terminals: &'v [&'v Expr<'v>],
170 cx: &'a LateContext<'tcx>,
174 impl<'a, 'tcx, 'v> SuggestContext<'a, 'tcx, 'v> {
175 fn recurse(&mut self, suggestion: &Bool) -> Option<()> {
176 use quine_mc_cluskey::Bool::{And, False, Not, Or, Term, True};
179 self.output.push_str("true");
182 self.output.push_str("false");
184 Not(inner) => match **inner {
186 self.output.push('!');
187 self.output.push('(');
189 self.output.push(')');
192 let terminal = self.terminals[n as usize];
193 if let Some(str) = simplify_not(self.cx, terminal) {
194 self.output.push_str(&str);
196 self.output.push('!');
197 let snip = snippet_opt(self.cx, terminal.span)?;
198 self.output.push_str(&snip);
201 True | False | Not(_) => {
202 self.output.push('!');
203 self.recurse(inner)?;
207 for (index, inner) in v.iter().enumerate() {
209 self.output.push_str(" && ");
211 if let Or(_) = *inner {
212 self.output.push('(');
214 self.output.push(')');
221 for (index, inner) in v.iter().rev().enumerate() {
223 self.output.push_str(" || ");
229 let snip = snippet_opt(self.cx, self.terminals[n as usize].span)?;
230 self.output.push_str(&snip);
237 fn simplify_not(cx: &LateContext<'_>, expr: &Expr<'_>) -> Option<String> {
239 ExprKind::Binary(binop, lhs, rhs) => {
240 if !implements_ord(cx, lhs) {
245 BinOpKind::Eq => Some(" != "),
246 BinOpKind::Ne => Some(" == "),
247 BinOpKind::Lt => Some(" >= "),
248 BinOpKind::Gt => Some(" <= "),
249 BinOpKind::Le => Some(" > "),
250 BinOpKind::Ge => Some(" < "),
256 snippet_opt(cx, lhs.span)?,
258 snippet_opt(cx, rhs.span)?
262 ExprKind::MethodCall(path, args, _) if args.len() == 1 => {
263 let type_of_receiver = cx.typeck_results().expr_ty(&args[0]);
264 if !is_type_diagnostic_item(cx, type_of_receiver, sym::Option)
265 && !is_type_diagnostic_item(cx, type_of_receiver, sym::Result)
269 METHODS_WITH_NEGATION
272 .flat_map(|(a, b)| vec![(a, b), (b, a)])
274 let path: &str = path.ident.name.as_str();
277 .and_then(|(_, neg_method)| Some(format!("{}.{}()", snippet_opt(cx, args[0].span)?, neg_method)))
283 fn suggest(cx: &LateContext<'_>, suggestion: &Bool, terminals: &[&Expr<'_>]) -> String {
284 let mut suggest_context = SuggestContext {
287 output: String::new(),
289 suggest_context.recurse(suggestion);
290 suggest_context.output
293 fn simple_negate(b: Bool) -> Bool {
294 use quine_mc_cluskey::Bool::{And, False, Not, Or, Term, True};
298 t @ Term(_) => Not(Box::new(t)),
301 *el = simple_negate(::std::mem::replace(el, True));
307 *el = simple_negate(::std::mem::replace(el, True));
311 Not(inner) => *inner,
317 terminals: [usize; 32],
322 fn terminal_stats(b: &Bool) -> Stats {
323 fn recurse(b: &Bool, stats: &mut Stats) {
325 True | False => stats.ops += 1,
328 And(_) | Or(_) => stats.ops += 1, // brackets are also operations
329 _ => stats.negations += 1,
331 recurse(inner, stats);
334 stats.ops += v.len() - 1;
336 recurse(inner, stats);
339 &Term(n) => stats.terminals[n as usize] += 1,
342 use quine_mc_cluskey::Bool::{And, False, Not, Or, Term, True};
343 let mut stats = Stats::default();
344 recurse(b, &mut stats);
348 impl<'a, 'tcx> NonminimalBoolVisitor<'a, 'tcx> {
349 fn bool_expr(&self, e: &'tcx Expr<'_>) {
350 let mut h2q = Hir2Qmm {
351 terminals: Vec::new(),
354 if let Ok(expr) = h2q.run(e) {
355 if h2q.terminals.len() > 8 {
356 // QMC has exponentially slow behavior as the number of terminals increases
357 // 8 is reasonable, it takes approximately 0.2 seconds.
362 let stats = terminal_stats(&expr);
363 let mut simplified = expr.simplify();
364 for simple in Bool::Not(Box::new(expr)).simplify() {
366 Bool::Not(_) | Bool::True | Bool::False => {},
367 _ => simplified.push(Bool::Not(Box::new(simple.clone()))),
369 let simple_negated = simple_negate(simple);
370 if simplified.iter().any(|s| *s == simple_negated) {
373 simplified.push(simple_negated);
375 let mut improvements = Vec::with_capacity(simplified.len());
376 'simplified: for suggestion in &simplified {
377 let simplified_stats = terminal_stats(suggestion);
378 let mut improvement = false;
380 // ignore any "simplifications" that end up requiring a terminal more often
381 // than in the original expression
382 if stats.terminals[i] < simplified_stats.terminals[i] {
383 continue 'simplified;
385 if stats.terminals[i] != 0 && simplified_stats.terminals[i] == 0 {
390 "this boolean expression contains a logic bug",
393 h2q.terminals[i].span,
394 "this expression can be optimized out by applying boolean operations to the \
397 diag.span_suggestion(
399 "it would look like the following",
400 suggest(self.cx, suggestion, &h2q.terminals),
401 // nonminimal_bool can produce minimal but
402 // not human readable expressions (#3141)
403 Applicability::Unspecified,
407 // don't also lint `NONMINIMAL_BOOL`
410 // if the number of occurrences of a terminal decreases or any of the stats
411 // decreases while none increases
412 improvement |= (stats.terminals[i] > simplified_stats.terminals[i])
413 || (stats.negations > simplified_stats.negations && stats.ops == simplified_stats.ops)
414 || (stats.ops > simplified_stats.ops && stats.negations == simplified_stats.negations);
417 improvements.push(suggestion);
420 let nonminimal_bool_lint = |suggestions: Vec<_>| {
425 "this boolean expression can be simplified",
427 diag.span_suggestions(
430 suggestions.into_iter(),
431 // nonminimal_bool can produce minimal but
432 // not human readable expressions (#3141)
433 Applicability::Unspecified,
438 if improvements.is_empty() {
439 let mut visitor = NotSimplificationVisitor { cx: self.cx };
440 visitor.visit_expr(e);
442 nonminimal_bool_lint(
445 .map(|suggestion| suggest(self.cx, suggestion, &h2q.terminals))
453 impl<'a, 'tcx> Visitor<'tcx> for NonminimalBoolVisitor<'a, 'tcx> {
454 fn visit_expr(&mut self, e: &'tcx Expr<'_>) {
455 if !e.span.from_expansion() {
457 ExprKind::Binary(binop, _, _) if binop.node == BinOpKind::Or || binop.node == BinOpKind::And => {
460 ExprKind::Unary(UnOp::Not, inner) => {
461 if self.cx.typeck_results().node_types()[inner.hir_id].is_bool() {
472 fn implements_ord<'tcx>(cx: &LateContext<'tcx>, expr: &Expr<'_>) -> bool {
473 let ty = cx.typeck_results().expr_ty(expr);
474 get_trait_def_id(cx, &paths::ORD).map_or(false, |id| implements_trait(cx, ty, id, &[]))
477 struct NotSimplificationVisitor<'a, 'tcx> {
478 cx: &'a LateContext<'tcx>,
481 impl<'a, 'tcx> Visitor<'tcx> for NotSimplificationVisitor<'a, 'tcx> {
482 fn visit_expr(&mut self, expr: &'tcx Expr<'_>) {
483 if let ExprKind::Unary(UnOp::Not, inner) = &expr.kind {
484 if let Some(suggestion) = simplify_not(self.cx, inner) {
489 "this boolean expression can be simplified",
492 Applicability::MachineApplicable,
497 walk_expr(self, expr);