2 get_trait_def_id, implements_trait, in_macro, match_type, paths, snippet_opt, span_lint_and_sugg,
3 span_lint_and_then, SpanlessEq,
5 use if_chain::if_chain;
6 use rustc::declare_lint_pass;
7 use rustc::hir::intravisit::*;
9 use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
10 use rustc_errors::Applicability;
11 use rustc_session::declare_tool_lint;
12 use syntax::ast::LitKind;
13 use syntax::source_map::Span;
15 declare_clippy_lint! {
16 /// **What it does:** Checks for boolean expressions that can be written more
19 /// **Why is this bad?** Readability of boolean expressions suffers from
20 /// unnecessary duplication.
22 /// **Known problems:** Ignores short circuiting behavior of `||` and
23 /// `&&`. Ignores `|`, `&` and `^`.
27 /// if a && true // should be: if a
28 /// if !(a == b) // should be: if a != b
32 "boolean expressions that can be written more concisely"
35 declare_clippy_lint! {
36 /// **What it does:** Checks for boolean expressions that contain terminals that
37 /// can be eliminated.
39 /// **Why is this bad?** This is most likely a logic bug.
41 /// **Known problems:** Ignores short circuiting behavior.
45 /// if a && b || a { ... }
47 /// The `b` is unnecessary, the expression is equivalent to `if a`.
50 "boolean expressions that contain terminals which can be eliminated"
53 // For each pairs, both orders are considered.
54 const METHODS_WITH_NEGATION: [(&str, &str); 2] = [("is_some", "is_none"), ("is_err", "is_ok")];
56 declare_lint_pass!(NonminimalBool => [NONMINIMAL_BOOL, LOGIC_BUG]);
58 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for NonminimalBool {
61 cx: &LateContext<'a, 'tcx>,
62 _: intravisit::FnKind<'tcx>,
68 NonminimalBoolVisitor { cx }.visit_body(body)
72 struct NonminimalBoolVisitor<'a, 'tcx> {
73 cx: &'a LateContext<'a, 'tcx>,
76 use quine_mc_cluskey::Bool;
77 struct Hir2Qmm<'a, 'tcx, 'v> {
78 terminals: Vec<&'v Expr>,
79 cx: &'a LateContext<'a, 'tcx>,
82 impl<'a, 'tcx, 'v> Hir2Qmm<'a, 'tcx, 'v> {
83 fn extract(&mut self, op: BinOpKind, a: &[&'v Expr], mut v: Vec<Bool>) -> Result<Vec<Bool>, String> {
85 if let ExprKind::Binary(binop, lhs, rhs) = &a.kind {
87 v = self.extract(op, &[lhs, rhs], v)?;
96 fn run(&mut self, e: &'v Expr) -> Result<Bool, String> {
97 fn negate(bin_op_kind: BinOpKind) -> Option<BinOpKind> {
99 BinOpKind::Eq => Some(BinOpKind::Ne),
100 BinOpKind::Ne => Some(BinOpKind::Eq),
101 BinOpKind::Gt => Some(BinOpKind::Le),
102 BinOpKind::Ge => Some(BinOpKind::Lt),
103 BinOpKind::Lt => Some(BinOpKind::Ge),
104 BinOpKind::Le => Some(BinOpKind::Gt),
109 // prevent folding of `cfg!` macros and the like
110 if !e.span.from_expansion() {
112 ExprKind::Unary(UnNot, inner) => return Ok(Bool::Not(box self.run(inner)?)),
113 ExprKind::Binary(binop, lhs, rhs) => match &binop.node {
114 BinOpKind::Or => return Ok(Bool::Or(self.extract(BinOpKind::Or, &[lhs, rhs], Vec::new())?)),
115 BinOpKind::And => return Ok(Bool::And(self.extract(BinOpKind::And, &[lhs, rhs], Vec::new())?)),
118 ExprKind::Lit(lit) => match lit.node {
119 LitKind::Bool(true) => return Ok(Bool::True),
120 LitKind::Bool(false) => return Ok(Bool::False),
126 for (n, expr) in self.terminals.iter().enumerate() {
127 if SpanlessEq::new(self.cx).ignore_fn().eq_expr(e, expr) {
128 #[allow(clippy::cast_possible_truncation)]
129 return Ok(Bool::Term(n as u8));
133 if let ExprKind::Binary(e_binop, e_lhs, e_rhs) = &e.kind;
134 if implements_ord(self.cx, e_lhs);
135 if let ExprKind::Binary(expr_binop, expr_lhs, expr_rhs) = &expr.kind;
136 if negate(e_binop.node) == Some(expr_binop.node);
137 if SpanlessEq::new(self.cx).ignore_fn().eq_expr(e_lhs, expr_lhs);
138 if SpanlessEq::new(self.cx).ignore_fn().eq_expr(e_rhs, expr_rhs);
140 #[allow(clippy::cast_possible_truncation)]
141 return Ok(Bool::Not(Box::new(Bool::Term(n as u8))));
145 let n = self.terminals.len();
146 self.terminals.push(e);
148 #[allow(clippy::cast_possible_truncation)]
149 Ok(Bool::Term(n as u8))
151 Err("too many literals".to_owned())
156 struct SuggestContext<'a, 'tcx, 'v> {
157 terminals: &'v [&'v Expr],
158 cx: &'a LateContext<'a, 'tcx>,
162 impl<'a, 'tcx, 'v> SuggestContext<'a, 'tcx, 'v> {
163 fn recurse(&mut self, suggestion: &Bool) -> Option<()> {
164 use quine_mc_cluskey::Bool::*;
167 self.output.push_str("true");
170 self.output.push_str("false");
172 Not(inner) => match **inner {
174 self.output.push('!');
175 self.output.push('(');
177 self.output.push(')');
180 let terminal = self.terminals[n as usize];
181 if let Some(str) = simplify_not(self.cx, terminal) {
182 self.output.push_str(&str)
184 self.output.push('!');
185 let snip = snippet_opt(self.cx, terminal.span)?;
186 self.output.push_str(&snip);
189 True | False | Not(_) => {
190 self.output.push('!');
191 self.recurse(inner)?;
195 for (index, inner) in v.iter().enumerate() {
197 self.output.push_str(" && ");
199 if let Or(_) = *inner {
200 self.output.push('(');
202 self.output.push(')');
209 for (index, inner) in v.iter().enumerate() {
211 self.output.push_str(" || ");
217 let snip = snippet_opt(self.cx, self.terminals[n as usize].span)?;
218 self.output.push_str(&snip);
225 fn simplify_not(cx: &LateContext<'_, '_>, expr: &Expr) -> Option<String> {
227 ExprKind::Binary(binop, lhs, rhs) => {
228 if !implements_ord(cx, lhs) {
233 BinOpKind::Eq => Some(" != "),
234 BinOpKind::Ne => Some(" == "),
235 BinOpKind::Lt => Some(" >= "),
236 BinOpKind::Gt => Some(" <= "),
237 BinOpKind::Le => Some(" > "),
238 BinOpKind::Ge => Some(" < "),
244 snippet_opt(cx, lhs.span)?,
246 snippet_opt(cx, rhs.span)?
250 ExprKind::MethodCall(path, _, args) if args.len() == 1 => {
251 let type_of_receiver = cx.tables.expr_ty(&args[0]);
252 if !match_type(cx, type_of_receiver, &paths::OPTION) && !match_type(cx, type_of_receiver, &paths::RESULT) {
255 METHODS_WITH_NEGATION
258 .flat_map(|(a, b)| vec![(a, b), (b, a)])
260 let path: &str = &path.ident.name.as_str();
263 .and_then(|(_, neg_method)| Some(format!("{}.{}()", snippet_opt(cx, args[0].span)?, neg_method)))
269 fn suggest(cx: &LateContext<'_, '_>, suggestion: &Bool, terminals: &[&Expr]) -> String {
270 let mut suggest_context = SuggestContext {
273 output: String::new(),
275 suggest_context.recurse(suggestion);
276 suggest_context.output
279 fn simple_negate(b: Bool) -> Bool {
280 use quine_mc_cluskey::Bool::*;
284 t @ Term(_) => Not(Box::new(t)),
287 *el = simple_negate(::std::mem::replace(el, True));
293 *el = simple_negate(::std::mem::replace(el, True));
297 Not(inner) => *inner,
303 terminals: [usize; 32],
308 fn terminal_stats(b: &Bool) -> Stats {
309 fn recurse(b: &Bool, stats: &mut Stats) {
311 True | False => stats.ops += 1,
314 And(_) | Or(_) => stats.ops += 1, // brackets are also operations
315 _ => stats.negations += 1,
317 recurse(inner, stats);
320 stats.ops += v.len() - 1;
322 recurse(inner, stats);
325 &Term(n) => stats.terminals[n as usize] += 1,
328 use quine_mc_cluskey::Bool::*;
329 let mut stats = Stats::default();
330 recurse(b, &mut stats);
334 impl<'a, 'tcx> NonminimalBoolVisitor<'a, 'tcx> {
335 fn bool_expr(&self, e: &'tcx Expr) {
336 let mut h2q = Hir2Qmm {
337 terminals: Vec::new(),
340 if let Ok(expr) = h2q.run(e) {
341 if h2q.terminals.len() > 8 {
342 // QMC has exponentially slow behavior as the number of terminals increases
343 // 8 is reasonable, it takes approximately 0.2 seconds.
348 let stats = terminal_stats(&expr);
349 let mut simplified = expr.simplify();
350 for simple in Bool::Not(Box::new(expr)).simplify() {
352 Bool::Not(_) | Bool::True | Bool::False => {},
353 _ => simplified.push(Bool::Not(Box::new(simple.clone()))),
355 let simple_negated = simple_negate(simple);
356 if simplified.iter().any(|s| *s == simple_negated) {
359 simplified.push(simple_negated);
361 let mut improvements = Vec::new();
362 'simplified: for suggestion in &simplified {
363 let simplified_stats = terminal_stats(suggestion);
364 let mut improvement = false;
366 // ignore any "simplifications" that end up requiring a terminal more often
367 // than in the original expression
368 if stats.terminals[i] < simplified_stats.terminals[i] {
369 continue 'simplified;
371 if stats.terminals[i] != 0 && simplified_stats.terminals[i] == 0 {
376 "this boolean expression contains a logic bug",
379 h2q.terminals[i].span,
380 "this expression can be optimized out by applying boolean operations to the \
385 "it would look like the following",
386 suggest(self.cx, suggestion, &h2q.terminals),
387 // nonminimal_bool can produce minimal but
388 // not human readable expressions (#3141)
389 Applicability::Unspecified,
393 // don't also lint `NONMINIMAL_BOOL`
396 // if the number of occurrences of a terminal decreases or any of the stats
397 // decreases while none increases
398 improvement |= (stats.terminals[i] > simplified_stats.terminals[i])
399 || (stats.negations > simplified_stats.negations && stats.ops == simplified_stats.ops)
400 || (stats.ops > simplified_stats.ops && stats.negations == simplified_stats.negations);
403 improvements.push(suggestion);
406 let nonminimal_bool_lint = |suggestions: Vec<_>| {
411 "this boolean expression can be simplified",
416 suggestions.into_iter(),
417 // nonminimal_bool can produce minimal but
418 // not human readable expressions (#3141)
419 Applicability::Unspecified,
424 if improvements.is_empty() {
425 let mut visitor = NotSimplificationVisitor { cx: self.cx };
426 visitor.visit_expr(e);
428 nonminimal_bool_lint(
431 .map(|suggestion| suggest(self.cx, suggestion, &h2q.terminals))
439 impl<'a, 'tcx> Visitor<'tcx> for NonminimalBoolVisitor<'a, 'tcx> {
440 fn visit_expr(&mut self, e: &'tcx Expr) {
441 if in_macro(e.span) {
445 ExprKind::Binary(binop, _, _) if binop.node == BinOpKind::Or || binop.node == BinOpKind::And => {
448 ExprKind::Unary(UnNot, inner) => {
449 if self.cx.tables.node_types()[inner.hir_id].is_bool() {
455 _ => walk_expr(self, e),
458 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
459 NestedVisitorMap::None
463 fn implements_ord<'a, 'tcx>(cx: &'a LateContext<'a, 'tcx>, expr: &Expr) -> bool {
464 let ty = cx.tables.expr_ty(expr);
465 get_trait_def_id(cx, &paths::ORD).map_or(false, |id| implements_trait(cx, ty, id, &[]))
468 struct NotSimplificationVisitor<'a, 'tcx> {
469 cx: &'a LateContext<'a, 'tcx>,
472 impl<'a, 'tcx> Visitor<'tcx> for NotSimplificationVisitor<'a, 'tcx> {
473 fn visit_expr(&mut self, expr: &'tcx Expr) {
474 if let ExprKind::Unary(UnNot, inner) = &expr.kind {
475 if let Some(suggestion) = simplify_not(self.cx, inner) {
480 "this boolean expression can be simplified",
483 Applicability::MachineApplicable,
488 walk_expr(self, expr);
490 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
491 NestedVisitorMap::None