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, NestedVisitorMap, Visitor};
9 use rustc_hir::{BinOpKind, Body, Expr, ExprKind, FnDecl, HirId, UnOp};
10 use rustc_lint::{LateContext, LateLintPass};
11 use rustc_middle::hir::map::Map;
12 use rustc_session::{declare_lint_pass, declare_tool_lint};
13 use rustc_span::source_map::Span;
16 declare_clippy_lint! {
18 /// Checks for boolean expressions that can be written more
21 /// ### Why is this bad?
22 /// Readability of boolean expressions suffers from
23 /// unnecessary duplication.
25 /// ### Known problems
26 /// Ignores short circuiting behavior of `||` and
27 /// `&&`. Ignores `|`, `&` and `^`.
31 /// if a && true // should be: if a
32 /// if !(a == b) // should be: if a != b
34 #[clippy::version = "pre 1.29.0"]
37 "boolean expressions that can be written more concisely"
40 declare_clippy_lint! {
42 /// Checks for boolean expressions that contain terminals that
43 /// can be eliminated.
45 /// ### Why is this bad?
46 /// This is most likely a logic bug.
48 /// ### Known problems
49 /// Ignores short circuiting behavior.
53 /// if a && b || a { ... }
55 /// The `b` is unnecessary, the expression is equivalent to `if a`.
56 #[clippy::version = "pre 1.29.0"]
59 "boolean expressions that contain terminals which can be eliminated"
62 // For each pairs, both orders are considered.
63 const METHODS_WITH_NEGATION: [(&str, &str); 2] = [("is_some", "is_none"), ("is_err", "is_ok")];
65 declare_lint_pass!(NonminimalBool => [NONMINIMAL_BOOL, LOGIC_BUG]);
67 impl<'tcx> LateLintPass<'tcx> for NonminimalBool {
70 cx: &LateContext<'tcx>,
77 NonminimalBoolVisitor { cx }.visit_body(body);
81 struct NonminimalBoolVisitor<'a, 'tcx> {
82 cx: &'a LateContext<'tcx>,
85 use quine_mc_cluskey::Bool;
86 struct Hir2Qmm<'a, 'tcx, 'v> {
87 terminals: Vec<&'v Expr<'v>>,
88 cx: &'a LateContext<'tcx>,
91 impl<'a, 'tcx, 'v> Hir2Qmm<'a, 'tcx, 'v> {
92 fn extract(&mut self, op: BinOpKind, a: &[&'v Expr<'_>], mut v: Vec<Bool>) -> Result<Vec<Bool>, String> {
94 if let ExprKind::Binary(binop, lhs, rhs) = &a.kind {
96 v = self.extract(op, &[lhs, rhs], v)?;
100 v.push(self.run(a)?);
105 fn run(&mut self, e: &'v Expr<'_>) -> Result<Bool, String> {
106 fn negate(bin_op_kind: BinOpKind) -> Option<BinOpKind> {
108 BinOpKind::Eq => Some(BinOpKind::Ne),
109 BinOpKind::Ne => Some(BinOpKind::Eq),
110 BinOpKind::Gt => Some(BinOpKind::Le),
111 BinOpKind::Ge => Some(BinOpKind::Lt),
112 BinOpKind::Lt => Some(BinOpKind::Ge),
113 BinOpKind::Le => Some(BinOpKind::Gt),
118 // prevent folding of `cfg!` macros and the like
119 if !e.span.from_expansion() {
121 ExprKind::Unary(UnOp::Not, inner) => return Ok(Bool::Not(Box::new(self.run(inner)?))),
122 ExprKind::Binary(binop, lhs, rhs) => match &binop.node {
124 return Ok(Bool::Or(self.extract(BinOpKind::Or, &[lhs, rhs], Vec::new())?));
127 return Ok(Bool::And(self.extract(BinOpKind::And, &[lhs, rhs], Vec::new())?));
131 ExprKind::Lit(lit) => match lit.node {
132 LitKind::Bool(true) => return Ok(Bool::True),
133 LitKind::Bool(false) => return Ok(Bool::False),
139 for (n, expr) in self.terminals.iter().enumerate() {
140 if eq_expr_value(self.cx, e, expr) {
141 #[allow(clippy::cast_possible_truncation)]
142 return Ok(Bool::Term(n as u8));
146 if let ExprKind::Binary(e_binop, e_lhs, e_rhs) = &e.kind;
147 if implements_ord(self.cx, e_lhs);
148 if let ExprKind::Binary(expr_binop, expr_lhs, expr_rhs) = &expr.kind;
149 if negate(e_binop.node) == Some(expr_binop.node);
150 if eq_expr_value(self.cx, e_lhs, expr_lhs);
151 if eq_expr_value(self.cx, e_rhs, expr_rhs);
153 #[allow(clippy::cast_possible_truncation)]
154 return Ok(Bool::Not(Box::new(Bool::Term(n as u8))));
158 let n = self.terminals.len();
159 self.terminals.push(e);
161 #[allow(clippy::cast_possible_truncation)]
162 Ok(Bool::Term(n as u8))
164 Err("too many literals".to_owned())
169 struct SuggestContext<'a, 'tcx, 'v> {
170 terminals: &'v [&'v Expr<'v>],
171 cx: &'a LateContext<'tcx>,
175 impl<'a, 'tcx, 'v> SuggestContext<'a, 'tcx, 'v> {
176 fn recurse(&mut self, suggestion: &Bool) -> Option<()> {
177 use quine_mc_cluskey::Bool::{And, False, Not, Or, Term, True};
180 self.output.push_str("true");
183 self.output.push_str("false");
185 Not(inner) => match **inner {
187 self.output.push('!');
188 self.output.push('(');
190 self.output.push(')');
193 let terminal = self.terminals[n as usize];
194 if let Some(str) = simplify_not(self.cx, terminal) {
195 self.output.push_str(&str);
197 self.output.push('!');
198 let snip = snippet_opt(self.cx, terminal.span)?;
199 self.output.push_str(&snip);
202 True | False | Not(_) => {
203 self.output.push('!');
204 self.recurse(inner)?;
208 for (index, inner) in v.iter().enumerate() {
210 self.output.push_str(" && ");
212 if let Or(_) = *inner {
213 self.output.push('(');
215 self.output.push(')');
222 for (index, inner) in v.iter().rev().enumerate() {
224 self.output.push_str(" || ");
230 let snip = snippet_opt(self.cx, self.terminals[n as usize].span)?;
231 self.output.push_str(&snip);
238 fn simplify_not(cx: &LateContext<'_>, expr: &Expr<'_>) -> Option<String> {
240 ExprKind::Binary(binop, lhs, rhs) => {
241 if !implements_ord(cx, lhs) {
246 BinOpKind::Eq => Some(" != "),
247 BinOpKind::Ne => Some(" == "),
248 BinOpKind::Lt => Some(" >= "),
249 BinOpKind::Gt => Some(" <= "),
250 BinOpKind::Le => Some(" > "),
251 BinOpKind::Ge => Some(" < "),
257 snippet_opt(cx, lhs.span)?,
259 snippet_opt(cx, rhs.span)?
263 ExprKind::MethodCall(path, _, args, _) if args.len() == 1 => {
264 let type_of_receiver = cx.typeck_results().expr_ty(&args[0]);
265 if !is_type_diagnostic_item(cx, type_of_receiver, sym::Option)
266 && !is_type_diagnostic_item(cx, type_of_receiver, sym::Result)
270 METHODS_WITH_NEGATION
273 .flat_map(|(a, b)| vec![(a, b), (b, a)])
275 let path: &str = &path.ident.name.as_str();
278 .and_then(|(_, neg_method)| Some(format!("{}.{}()", snippet_opt(cx, args[0].span)?, neg_method)))
284 fn suggest(cx: &LateContext<'_>, suggestion: &Bool, terminals: &[&Expr<'_>]) -> String {
285 let mut suggest_context = SuggestContext {
288 output: String::new(),
290 suggest_context.recurse(suggestion);
291 suggest_context.output
294 fn simple_negate(b: Bool) -> Bool {
295 use quine_mc_cluskey::Bool::{And, False, Not, Or, Term, True};
299 t @ Term(_) => Not(Box::new(t)),
302 *el = simple_negate(::std::mem::replace(el, True));
308 *el = simple_negate(::std::mem::replace(el, True));
312 Not(inner) => *inner,
318 terminals: [usize; 32],
323 fn terminal_stats(b: &Bool) -> Stats {
324 fn recurse(b: &Bool, stats: &mut Stats) {
326 True | False => stats.ops += 1,
329 And(_) | Or(_) => stats.ops += 1, // brackets are also operations
330 _ => stats.negations += 1,
332 recurse(inner, stats);
335 stats.ops += v.len() - 1;
337 recurse(inner, stats);
340 &Term(n) => stats.terminals[n as usize] += 1,
343 use quine_mc_cluskey::Bool::{And, False, Not, Or, Term, True};
344 let mut stats = Stats::default();
345 recurse(b, &mut stats);
349 impl<'a, 'tcx> NonminimalBoolVisitor<'a, 'tcx> {
350 fn bool_expr(&self, e: &'tcx Expr<'_>) {
351 let mut h2q = Hir2Qmm {
352 terminals: Vec::new(),
355 if let Ok(expr) = h2q.run(e) {
356 if h2q.terminals.len() > 8 {
357 // QMC has exponentially slow behavior as the number of terminals increases
358 // 8 is reasonable, it takes approximately 0.2 seconds.
363 let stats = terminal_stats(&expr);
364 let mut simplified = expr.simplify();
365 for simple in Bool::Not(Box::new(expr)).simplify() {
367 Bool::Not(_) | Bool::True | Bool::False => {},
368 _ => simplified.push(Bool::Not(Box::new(simple.clone()))),
370 let simple_negated = simple_negate(simple);
371 if simplified.iter().any(|s| *s == simple_negated) {
374 simplified.push(simple_negated);
376 let mut improvements = Vec::with_capacity(simplified.len());
377 'simplified: for suggestion in &simplified {
378 let simplified_stats = terminal_stats(suggestion);
379 let mut improvement = false;
381 // ignore any "simplifications" that end up requiring a terminal more often
382 // than in the original expression
383 if stats.terminals[i] < simplified_stats.terminals[i] {
384 continue 'simplified;
386 if stats.terminals[i] != 0 && simplified_stats.terminals[i] == 0 {
391 "this boolean expression contains a logic bug",
394 h2q.terminals[i].span,
395 "this expression can be optimized out by applying boolean operations to the \
398 diag.span_suggestion(
400 "it would look like the following",
401 suggest(self.cx, suggestion, &h2q.terminals),
402 // nonminimal_bool can produce minimal but
403 // not human readable expressions (#3141)
404 Applicability::Unspecified,
408 // don't also lint `NONMINIMAL_BOOL`
411 // if the number of occurrences of a terminal decreases or any of the stats
412 // decreases while none increases
413 improvement |= (stats.terminals[i] > simplified_stats.terminals[i])
414 || (stats.negations > simplified_stats.negations && stats.ops == simplified_stats.ops)
415 || (stats.ops > simplified_stats.ops && stats.negations == simplified_stats.negations);
418 improvements.push(suggestion);
421 let nonminimal_bool_lint = |suggestions: Vec<_>| {
426 "this boolean expression can be simplified",
428 diag.span_suggestions(
431 suggestions.into_iter(),
432 // nonminimal_bool can produce minimal but
433 // not human readable expressions (#3141)
434 Applicability::Unspecified,
439 if improvements.is_empty() {
440 let mut visitor = NotSimplificationVisitor { cx: self.cx };
441 visitor.visit_expr(e);
443 nonminimal_bool_lint(
446 .map(|suggestion| suggest(self.cx, suggestion, &h2q.terminals))
454 impl<'a, 'tcx> Visitor<'tcx> for NonminimalBoolVisitor<'a, 'tcx> {
455 type Map = Map<'tcx>;
457 fn visit_expr(&mut self, e: &'tcx Expr<'_>) {
458 if !e.span.from_expansion() {
460 ExprKind::Binary(binop, _, _) if binop.node == BinOpKind::Or || binop.node == BinOpKind::And => {
463 ExprKind::Unary(UnOp::Not, inner) => {
464 if self.cx.typeck_results().node_types()[inner.hir_id].is_bool() {
473 fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
474 NestedVisitorMap::None
478 fn implements_ord<'tcx>(cx: &LateContext<'tcx>, expr: &Expr<'_>) -> bool {
479 let ty = cx.typeck_results().expr_ty(expr);
480 get_trait_def_id(cx, &paths::ORD).map_or(false, |id| implements_trait(cx, ty, id, &[]))
483 struct NotSimplificationVisitor<'a, 'tcx> {
484 cx: &'a LateContext<'tcx>,
487 impl<'a, 'tcx> Visitor<'tcx> for NotSimplificationVisitor<'a, 'tcx> {
488 type Map = Map<'tcx>;
490 fn visit_expr(&mut self, expr: &'tcx Expr<'_>) {
491 if let ExprKind::Unary(UnOp::Not, inner) = &expr.kind {
492 if let Some(suggestion) = simplify_not(self.cx, inner) {
497 "this boolean expression can be simplified",
500 Applicability::MachineApplicable,
505 walk_expr(self, expr);
507 fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
508 NestedVisitorMap::None