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, in_macro, 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
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`.
57 "boolean expressions that contain terminals which can be eliminated"
60 // For each pairs, both orders are considered.
61 const METHODS_WITH_NEGATION: [(&str, &str); 2] = [("is_some", "is_none"), ("is_err", "is_ok")];
63 declare_lint_pass!(NonminimalBool => [NONMINIMAL_BOOL, LOGIC_BUG]);
65 impl<'tcx> LateLintPass<'tcx> for NonminimalBool {
68 cx: &LateContext<'tcx>,
75 NonminimalBoolVisitor { cx }.visit_body(body);
79 struct NonminimalBoolVisitor<'a, 'tcx> {
80 cx: &'a LateContext<'tcx>,
83 use quine_mc_cluskey::Bool;
84 struct Hir2Qmm<'a, 'tcx, 'v> {
85 terminals: Vec<&'v Expr<'v>>,
86 cx: &'a LateContext<'tcx>,
89 impl<'a, 'tcx, 'v> Hir2Qmm<'a, 'tcx, 'v> {
90 fn extract(&mut self, op: BinOpKind, a: &[&'v Expr<'_>], mut v: Vec<Bool>) -> Result<Vec<Bool>, String> {
92 if let ExprKind::Binary(binop, lhs, rhs) = &a.kind {
94 v = self.extract(op, &[lhs, rhs], v)?;
103 fn run(&mut self, e: &'v Expr<'_>) -> Result<Bool, String> {
104 fn negate(bin_op_kind: BinOpKind) -> Option<BinOpKind> {
106 BinOpKind::Eq => Some(BinOpKind::Ne),
107 BinOpKind::Ne => Some(BinOpKind::Eq),
108 BinOpKind::Gt => Some(BinOpKind::Le),
109 BinOpKind::Ge => Some(BinOpKind::Lt),
110 BinOpKind::Lt => Some(BinOpKind::Ge),
111 BinOpKind::Le => Some(BinOpKind::Gt),
116 // prevent folding of `cfg!` macros and the like
117 if !e.span.from_expansion() {
119 ExprKind::Unary(UnOp::Not, inner) => return Ok(Bool::Not(Box::new(self.run(inner)?))),
120 ExprKind::Binary(binop, lhs, rhs) => match &binop.node {
122 return Ok(Bool::Or(self.extract(BinOpKind::Or, &[lhs, rhs], Vec::new())?));
125 return Ok(Bool::And(self.extract(BinOpKind::And, &[lhs, rhs], Vec::new())?));
129 ExprKind::Lit(lit) => match lit.node {
130 LitKind::Bool(true) => return Ok(Bool::True),
131 LitKind::Bool(false) => return Ok(Bool::False),
137 for (n, expr) in self.terminals.iter().enumerate() {
138 if eq_expr_value(self.cx, e, expr) {
139 #[allow(clippy::cast_possible_truncation)]
140 return Ok(Bool::Term(n as u8));
144 if let ExprKind::Binary(e_binop, e_lhs, e_rhs) = &e.kind;
145 if implements_ord(self.cx, e_lhs);
146 if let ExprKind::Binary(expr_binop, expr_lhs, expr_rhs) = &expr.kind;
147 if negate(e_binop.node) == Some(expr_binop.node);
148 if eq_expr_value(self.cx, e_lhs, expr_lhs);
149 if eq_expr_value(self.cx, e_rhs, expr_rhs);
151 #[allow(clippy::cast_possible_truncation)]
152 return Ok(Bool::Not(Box::new(Bool::Term(n as u8))));
156 let n = self.terminals.len();
157 self.terminals.push(e);
159 #[allow(clippy::cast_possible_truncation)]
160 Ok(Bool::Term(n as u8))
162 Err("too many literals".to_owned())
167 struct SuggestContext<'a, 'tcx, 'v> {
168 terminals: &'v [&'v Expr<'v>],
169 cx: &'a LateContext<'tcx>,
173 impl<'a, 'tcx, 'v> SuggestContext<'a, 'tcx, 'v> {
174 fn recurse(&mut self, suggestion: &Bool) -> Option<()> {
175 use quine_mc_cluskey::Bool::{And, False, Not, Or, Term, True};
178 self.output.push_str("true");
181 self.output.push_str("false");
183 Not(inner) => match **inner {
185 self.output.push('!');
186 self.output.push('(');
188 self.output.push(')');
191 let terminal = self.terminals[n as usize];
192 if let Some(str) = simplify_not(self.cx, terminal) {
193 self.output.push_str(&str);
195 self.output.push('!');
196 let snip = snippet_opt(self.cx, terminal.span)?;
197 self.output.push_str(&snip);
200 True | False | Not(_) => {
201 self.output.push('!');
202 self.recurse(inner)?;
206 for (index, inner) in v.iter().enumerate() {
208 self.output.push_str(" && ");
210 if let Or(_) = *inner {
211 self.output.push('(');
213 self.output.push(')');
220 for (index, inner) in v.iter().rev().enumerate() {
222 self.output.push_str(" || ");
228 let snip = snippet_opt(self.cx, self.terminals[n as usize].span)?;
229 self.output.push_str(&snip);
236 fn simplify_not(cx: &LateContext<'_>, expr: &Expr<'_>) -> Option<String> {
238 ExprKind::Binary(binop, lhs, rhs) => {
239 if !implements_ord(cx, lhs) {
244 BinOpKind::Eq => Some(" != "),
245 BinOpKind::Ne => Some(" == "),
246 BinOpKind::Lt => Some(" >= "),
247 BinOpKind::Gt => Some(" <= "),
248 BinOpKind::Le => Some(" > "),
249 BinOpKind::Ge => Some(" < "),
255 snippet_opt(cx, lhs.span)?,
257 snippet_opt(cx, rhs.span)?
261 ExprKind::MethodCall(path, _, args, _) if args.len() == 1 => {
262 let type_of_receiver = cx.typeck_results().expr_ty(&args[0]);
263 if !is_type_diagnostic_item(cx, type_of_receiver, sym::Option)
264 && !is_type_diagnostic_item(cx, type_of_receiver, sym::Result)
268 METHODS_WITH_NEGATION
271 .flat_map(|(a, b)| vec![(a, b), (b, a)])
273 let path: &str = &path.ident.name.as_str();
276 .and_then(|(_, neg_method)| Some(format!("{}.{}()", snippet_opt(cx, args[0].span)?, neg_method)))
282 fn suggest(cx: &LateContext<'_>, suggestion: &Bool, terminals: &[&Expr<'_>]) -> String {
283 let mut suggest_context = SuggestContext {
286 output: String::new(),
288 suggest_context.recurse(suggestion);
289 suggest_context.output
292 fn simple_negate(b: Bool) -> Bool {
293 use quine_mc_cluskey::Bool::{And, False, Not, Or, Term, True};
297 t @ Term(_) => Not(Box::new(t)),
300 *el = simple_negate(::std::mem::replace(el, True));
306 *el = simple_negate(::std::mem::replace(el, True));
310 Not(inner) => *inner,
316 terminals: [usize; 32],
321 fn terminal_stats(b: &Bool) -> Stats {
322 fn recurse(b: &Bool, stats: &mut Stats) {
324 True | False => stats.ops += 1,
327 And(_) | Or(_) => stats.ops += 1, // brackets are also operations
328 _ => stats.negations += 1,
330 recurse(inner, stats);
333 stats.ops += v.len() - 1;
335 recurse(inner, stats);
338 &Term(n) => stats.terminals[n as usize] += 1,
341 use quine_mc_cluskey::Bool::{And, False, Not, Or, Term, True};
342 let mut stats = Stats::default();
343 recurse(b, &mut stats);
347 impl<'a, 'tcx> NonminimalBoolVisitor<'a, 'tcx> {
348 fn bool_expr(&self, e: &'tcx Expr<'_>) {
349 let mut h2q = Hir2Qmm {
350 terminals: Vec::new(),
353 if let Ok(expr) = h2q.run(e) {
354 if h2q.terminals.len() > 8 {
355 // QMC has exponentially slow behavior as the number of terminals increases
356 // 8 is reasonable, it takes approximately 0.2 seconds.
361 let stats = terminal_stats(&expr);
362 let mut simplified = expr.simplify();
363 for simple in Bool::Not(Box::new(expr)).simplify() {
365 Bool::Not(_) | Bool::True | Bool::False => {},
366 _ => simplified.push(Bool::Not(Box::new(simple.clone()))),
368 let simple_negated = simple_negate(simple);
369 if simplified.iter().any(|s| *s == simple_negated) {
372 simplified.push(simple_negated);
374 let mut improvements = Vec::with_capacity(simplified.len());
375 'simplified: for suggestion in &simplified {
376 let simplified_stats = terminal_stats(suggestion);
377 let mut improvement = false;
379 // ignore any "simplifications" that end up requiring a terminal more often
380 // than in the original expression
381 if stats.terminals[i] < simplified_stats.terminals[i] {
382 continue 'simplified;
384 if stats.terminals[i] != 0 && simplified_stats.terminals[i] == 0 {
389 "this boolean expression contains a logic bug",
392 h2q.terminals[i].span,
393 "this expression can be optimized out by applying boolean operations to the \
396 diag.span_suggestion(
398 "it would look like the following",
399 suggest(self.cx, suggestion, &h2q.terminals),
400 // nonminimal_bool can produce minimal but
401 // not human readable expressions (#3141)
402 Applicability::Unspecified,
406 // don't also lint `NONMINIMAL_BOOL`
409 // if the number of occurrences of a terminal decreases or any of the stats
410 // decreases while none increases
411 improvement |= (stats.terminals[i] > simplified_stats.terminals[i])
412 || (stats.negations > simplified_stats.negations && stats.ops == simplified_stats.ops)
413 || (stats.ops > simplified_stats.ops && stats.negations == simplified_stats.negations);
416 improvements.push(suggestion);
419 let nonminimal_bool_lint = |suggestions: Vec<_>| {
424 "this boolean expression can be simplified",
426 diag.span_suggestions(
429 suggestions.into_iter(),
430 // nonminimal_bool can produce minimal but
431 // not human readable expressions (#3141)
432 Applicability::Unspecified,
437 if improvements.is_empty() {
438 let mut visitor = NotSimplificationVisitor { cx: self.cx };
439 visitor.visit_expr(e);
441 nonminimal_bool_lint(
444 .map(|suggestion| suggest(self.cx, suggestion, &h2q.terminals))
452 impl<'a, 'tcx> Visitor<'tcx> for NonminimalBoolVisitor<'a, 'tcx> {
453 type Map = Map<'tcx>;
455 fn visit_expr(&mut self, e: &'tcx Expr<'_>) {
456 if in_macro(e.span) {
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() {
470 _ => walk_expr(self, e),
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