2 constants, snippet_opt, snippet_with_applicability, span_help_and_lint, span_lint, span_lint_and_sugg,
5 use if_chain::if_chain;
6 use rustc::lint::{in_external_macro, EarlyContext, EarlyLintPass, LintArray, LintContext, LintPass};
7 use rustc::{declare_lint_pass, declare_tool_lint};
8 use rustc_data_structures::fx::FxHashMap;
9 use rustc_errors::Applicability;
11 use syntax::source_map::Span;
12 use syntax::visit::{walk_expr, FnKind, Visitor};
14 declare_clippy_lint! {
15 /// **What it does:** Checks for structure field patterns bound to wildcards.
17 /// **Why is this bad?** Using `..` instead is shorter and leaves the focus on
18 /// the fields that are actually bound.
20 /// **Known problems:** None.
24 /// let { a: _, b: ref b, c: _ } = ..
26 pub UNNEEDED_FIELD_PATTERN,
28 "struct fields bound to a wildcard instead of using `..`"
31 declare_clippy_lint! {
32 /// **What it does:** Checks for function arguments having the similar names
33 /// differing by an underscore.
35 /// **Why is this bad?** It affects code readability.
37 /// **Known problems:** None.
41 /// fn foo(a: i32, _a: i32) {}
43 pub DUPLICATE_UNDERSCORE_ARGUMENT,
45 "function arguments having names which only differ by an underscore"
48 declare_clippy_lint! {
49 /// **What it does:** Detects closures called in the same expression where they
52 /// **Why is this bad?** It is unnecessarily adding to the expression's
55 /// **Known problems:** None.
61 pub REDUNDANT_CLOSURE_CALL,
63 "throwaway closures called in the expression they are defined"
66 declare_clippy_lint! {
67 /// **What it does:** Detects expressions of the form `--x`.
69 /// **Why is this bad?** It can mislead C/C++ programmers to think `x` was
72 /// **Known problems:** None.
81 "`--x`, which is a double negation of `x` and not a pre-decrement as in C/C++"
84 declare_clippy_lint! {
85 /// **What it does:** Warns on hexadecimal literals with mixed-case letter
88 /// **Why is this bad?** It looks confusing.
90 /// **Known problems:** None.
94 /// let y = 0x1a9BAcD;
96 pub MIXED_CASE_HEX_LITERALS,
98 "hex literals whose letter digits are not consistently upper- or lowercased"
101 declare_clippy_lint! {
102 /// **What it does:** Warns if literal suffixes are not separated by an
105 /// **Why is this bad?** It is much less readable.
107 /// **Known problems:** None.
111 /// let y = 123832i32;
113 pub UNSEPARATED_LITERAL_SUFFIX,
115 "literals whose suffix is not separated by an underscore"
118 declare_clippy_lint! {
119 /// **What it does:** Warns if an integral constant literal starts with `0`.
121 /// **Why is this bad?** In some languages (including the infamous C language
123 /// family), this marks an octal constant. In Rust however, this is a decimal
124 /// constant. This could
125 /// be confusing for both the writer and a reader of the constant.
127 /// **Known problems:** None.
135 /// println!("{}", a);
139 /// prints `123`, while in C:
142 /// #include <stdio.h>
146 /// printf("%d\n", a);
150 /// prints `83` (as `83 == 0o123` while `123 == 0o173`).
151 pub ZERO_PREFIXED_LITERAL,
153 "integer literals starting with `0`"
156 declare_clippy_lint! {
157 /// **What it does:** Warns if a generic shadows a built-in type.
159 /// **Why is this bad?** This gives surprising type errors.
161 /// **Known problems:** None.
166 /// impl<u32> Foo<u32> {
167 /// fn impl_func(&self) -> u32 {
172 pub BUILTIN_TYPE_SHADOW,
174 "shadowing a builtin type"
177 declare_clippy_lint! {
178 /// **What it does:** Checks for patterns in the form `name @ _`.
180 /// **Why is this bad?** It's almost always more readable to just use direct
183 /// **Known problems:** None.
187 /// # let v = Some("abc");
191 /// y @ _ => (), // easier written as `y`,
194 pub REDUNDANT_PATTERN,
196 "using `name @ _` in a pattern"
199 declare_clippy_lint! {
200 /// **What it does:** Checks for tuple patterns with a wildcard
201 /// pattern (`_`) is next to a rest pattern (`..`).
203 /// _NOTE_: While `_, ..` means there is at least one element left, `..`
204 /// means there are 0 or more elements left. This can make a difference
205 /// when refactoring, but shouldn't result in errors in the refactored code,
206 /// since the wildcard pattern isn't used anyway.
207 /// **Why is this bad?** The wildcard pattern is unneeded as the rest pattern
208 /// can match that element as well.
210 /// **Known problems:** None.
214 /// # struct TupleStruct(u32, u32, u32);
215 /// # let t = TupleStruct(1, 2, 3);
218 /// TupleStruct(0, .., _) => (),
222 /// can be written as
224 /// # struct TupleStruct(u32, u32, u32);
225 /// # let t = TupleStruct(1, 2, 3);
228 /// TupleStruct(0, ..) => (),
232 pub UNNEEDED_WILDCARD_PATTERN,
234 "tuple patterns with a wildcard pattern (`_`) is next to a rest pattern (`..`)"
237 declare_lint_pass!(MiscEarlyLints => [
238 UNNEEDED_FIELD_PATTERN,
239 DUPLICATE_UNDERSCORE_ARGUMENT,
240 REDUNDANT_CLOSURE_CALL,
242 MIXED_CASE_HEX_LITERALS,
243 UNSEPARATED_LITERAL_SUFFIX,
244 ZERO_PREFIXED_LITERAL,
247 UNNEEDED_WILDCARD_PATTERN,
250 // Used to find `return` statements or equivalents e.g., `?`
251 struct ReturnVisitor {
258 Self { found_return: false }
262 impl<'ast> Visitor<'ast> for ReturnVisitor {
263 fn visit_expr(&mut self, ex: &'ast Expr) {
264 if let ExprKind::Ret(_) = ex.kind {
265 self.found_return = true;
266 } else if let ExprKind::Try(_) = ex.kind {
267 self.found_return = true;
274 impl EarlyLintPass for MiscEarlyLints {
275 fn check_generics(&mut self, cx: &EarlyContext<'_>, gen: &Generics) {
276 for param in &gen.params {
277 if let GenericParamKind::Type { .. } = param.kind {
278 let name = param.ident.as_str();
279 if constants::BUILTIN_TYPES.contains(&&*name) {
284 &format!("This generic shadows the built-in type `{}`", name),
291 fn check_pat(&mut self, cx: &EarlyContext<'_>, pat: &Pat) {
292 if let PatKind::Struct(ref npat, ref pfields, _) = pat.kind {
297 .expect("A path must have at least one segment")
301 for field in pfields {
302 if let PatKind::Wild = field.pat.kind {
306 if !pfields.is_empty() && wilds == pfields.len() {
309 UNNEEDED_FIELD_PATTERN,
311 "All the struct fields are matched to a wildcard pattern, consider using `..`.",
312 &format!("Try with `{} {{ .. }}` instead", type_name),
317 let mut normal = vec![];
319 for field in pfields {
320 match field.pat.kind {
323 if let Ok(n) = cx.sess().source_map().span_to_snippet(field.span) {
329 for field in pfields {
330 if let PatKind::Wild = field.pat.kind {
335 UNNEEDED_FIELD_PATTERN,
337 "You matched a field with a wildcard pattern. Consider using `..` instead",
342 UNNEEDED_FIELD_PATTERN,
344 "You matched a field with a wildcard pattern. Consider using `..` \
346 &format!("Try with `{} {{ {}, .. }}`", type_name, normal[..].join(", ")),
354 if let PatKind::Ident(_, ident, Some(ref right)) = pat.kind {
355 if let PatKind::Wild = right.kind {
361 "the `{} @ _` pattern can be written as just `{}`",
362 ident.name, ident.name,
365 format!("{}", ident.name),
366 Applicability::MachineApplicable,
371 check_unneeded_wildcard_pattern(cx, pat);
374 fn check_fn(&mut self, cx: &EarlyContext<'_>, _: FnKind<'_>, decl: &FnDecl, _: Span, _: NodeId) {
375 let mut registered_names: FxHashMap<String, Span> = FxHashMap::default();
377 for arg in &decl.inputs {
378 if let PatKind::Ident(_, ident, None) = arg.pat.kind {
379 let arg_name = ident.to_string();
381 if arg_name.starts_with('_') {
382 if let Some(correspondence) = registered_names.get(&arg_name[1..]) {
385 DUPLICATE_UNDERSCORE_ARGUMENT,
388 "`{}` already exists, having another argument having almost the same \
389 name makes code comprehension and documentation more difficult",
390 arg_name[1..].to_owned()
395 registered_names.insert(arg_name, arg.pat.span);
401 fn check_expr(&mut self, cx: &EarlyContext<'_>, expr: &Expr) {
402 if in_external_macro(cx.sess(), expr.span) {
406 ExprKind::Call(ref paren, _) => {
407 if let ExprKind::Paren(ref closure) = paren.kind {
408 if let ExprKind::Closure(_, _, _, ref decl, ref block, _) = closure.kind {
409 let mut visitor = ReturnVisitor::new();
410 visitor.visit_expr(block);
411 if !visitor.found_return {
414 REDUNDANT_CLOSURE_CALL,
416 "Try not to call a closure in the expression where it is declared.",
418 if decl.inputs.is_empty() {
419 let mut app = Applicability::MachineApplicable;
421 snippet_with_applicability(cx, block.span, "..", &mut app).into_owned();
422 db.span_suggestion(expr.span, "Try doing something like: ", hint, app);
430 ExprKind::Unary(UnOp::Neg, ref inner) => {
431 if let ExprKind::Unary(UnOp::Neg, _) = inner.kind {
436 "`--x` could be misinterpreted as pre-decrement by C programmers, is usually a no-op",
440 ExprKind::Lit(ref lit) => Self::check_lit(cx, lit),
445 fn check_block(&mut self, cx: &EarlyContext<'_>, block: &Block) {
446 for w in block.stmts.windows(2) {
448 if let StmtKind::Local(ref local) = w[0].kind;
449 if let Option::Some(ref t) = local.init;
450 if let ExprKind::Closure(..) = t.kind;
451 if let PatKind::Ident(_, ident, _) = local.pat.kind;
452 if let StmtKind::Semi(ref second) = w[1].kind;
453 if let ExprKind::Assign(_, ref call) = second.kind;
454 if let ExprKind::Call(ref closure, _) = call.kind;
455 if let ExprKind::Path(_, ref path) = closure.kind;
457 if ident == path.segments[0].ident {
460 REDUNDANT_CLOSURE_CALL,
462 "Closure called just once immediately after it was declared",
471 impl MiscEarlyLints {
472 fn check_lit(cx: &EarlyContext<'_>, lit: &Lit) {
473 // We test if first character in snippet is a number, because the snippet could be an expansion
474 // from a built-in macro like `line!()` or a proc-macro like `#[wasm_bindgen]`.
475 // Note that this check also covers special case that `line!()` is eagerly expanded by compiler.
476 // See <https://github.com/rust-lang/rust-clippy/issues/4507> for a regression.
477 // FIXME: Find a better way to detect those cases.
478 let lit_snip = match snippet_opt(cx, lit.span) {
479 Some(snip) if snip.chars().next().map_or(false, |c| c.is_digit(10)) => snip,
483 if let LitKind::Int(value, lit_int_type) = lit.kind {
484 let suffix = match lit_int_type {
485 LitIntType::Signed(ty) => ty.name_str(),
486 LitIntType::Unsigned(ty) => ty.name_str(),
487 LitIntType::Unsuffixed => "",
490 let maybe_last_sep_idx = lit_snip.len() - suffix.len() - 1;
491 // Do not lint when literal is unsuffixed.
492 if !suffix.is_empty() && lit_snip.as_bytes()[maybe_last_sep_idx] != b'_' {
495 UNSEPARATED_LITERAL_SUFFIX,
497 "integer type suffix should be separated by an underscore",
499 format!("{}_{}", &lit_snip[..=maybe_last_sep_idx], suffix),
500 Applicability::MachineApplicable,
504 if lit_snip.starts_with("0x") {
505 let mut seen = (false, false);
506 for ch in lit_snip.as_bytes()[2..=maybe_last_sep_idx].iter() {
508 b'a'..=b'f' => seen.0 = true,
509 b'A'..=b'F' => seen.1 = true,
512 if seen.0 && seen.1 {
515 MIXED_CASE_HEX_LITERALS,
517 "inconsistent casing in hexadecimal literal",
522 } else if lit_snip.starts_with("0b") || lit_snip.starts_with("0o") {
524 } else if value != 0 && lit_snip.starts_with('0') {
527 ZERO_PREFIXED_LITERAL,
529 "this is a decimal constant",
533 "if you mean to use a decimal constant, remove the `0` to avoid confusion",
534 lit_snip.trim_start_matches(|c| c == '_' || c == '0').to_string(),
535 Applicability::MaybeIncorrect,
539 "if you mean to use an octal constant, use `0o`",
540 format!("0o{}", lit_snip.trim_start_matches(|c| c == '_' || c == '0')),
541 Applicability::MaybeIncorrect,
546 } else if let LitKind::Float(_, LitFloatType::Suffixed(float_ty)) = lit.kind {
547 let suffix = float_ty.name_str();
548 let maybe_last_sep_idx = lit_snip.len() - suffix.len() - 1;
549 if lit_snip.as_bytes()[maybe_last_sep_idx] != b'_' {
552 UNSEPARATED_LITERAL_SUFFIX,
554 "float type suffix should be separated by an underscore",
556 format!("{}_{}", &lit_snip[..=maybe_last_sep_idx], suffix),
557 Applicability::MachineApplicable,
564 fn check_unneeded_wildcard_pattern(cx: &EarlyContext<'_>, pat: &Pat) {
565 if let PatKind::TupleStruct(_, ref patterns) | PatKind::Tuple(ref patterns) = pat.kind {
566 fn span_lint(cx: &EarlyContext<'_>, span: Span, only_one: bool) {
569 UNNEEDED_WILDCARD_PATTERN,
572 "this pattern is unneeded as the `..` pattern can match that element"
574 "these patterns are unneeded as the `..` pattern can match those elements"
576 if only_one { "remove it" } else { "remove them" },
578 Applicability::MachineApplicable,
582 #[allow(clippy::trivially_copy_pass_by_ref)]
583 fn is_wild<P: std::ops::Deref<Target = Pat>>(pat: &&P) -> bool {
584 if let PatKind::Wild = pat.kind {
591 if let Some(rest_index) = patterns.iter().position(|pat| pat.is_rest()) {
592 if let Some((left_index, left_pat)) = patterns[..rest_index]
599 span_lint(cx, left_pat.span.until(patterns[rest_index].span), left_index == 0);
602 if let Some((right_index, right_pat)) =
603 patterns[rest_index + 1..].iter().take_while(is_wild).enumerate().last()
607 patterns[rest_index].span.shrink_to_hi().to(right_pat.span),