1 use crate::utils::{constants, snippet_opt, span_lint, span_lint_and_help, span_lint_and_sugg, span_lint_and_then};
3 BindingMode, Expr, ExprKind, GenericParamKind, Generics, Lit, LitFloatType, LitIntType, LitKind, Mutability,
4 NodeId, Pat, PatKind, UnOp,
6 use rustc_ast::visit::FnKind;
7 use rustc_data_structures::fx::FxHashMap;
8 use rustc_errors::Applicability;
9 use rustc_lint::{EarlyContext, EarlyLintPass, LintContext};
10 use rustc_middle::lint::in_external_macro;
11 use rustc_session::{declare_lint_pass, declare_tool_lint};
12 use rustc_span::source_map::Span;
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.
29 /// let f = Foo { a: 0, b: 0, c: 0 };
33 /// Foo { a: _, b: 0, .. } => {},
34 /// Foo { a: _, b: _, c: _ } => {},
39 /// Foo { b: 0, .. } => {},
43 pub UNNEEDED_FIELD_PATTERN,
45 "struct fields bound to a wildcard instead of using `..`"
48 declare_clippy_lint! {
49 /// **What it does:** Checks for function arguments having the similar names
50 /// differing by an underscore.
52 /// **Why is this bad?** It affects code readability.
54 /// **Known problems:** None.
59 /// fn foo(a: i32, _a: i32) {}
62 /// fn bar(a: i32, _b: i32) {}
64 pub DUPLICATE_UNDERSCORE_ARGUMENT,
66 "function arguments having names which only differ by an underscore"
69 declare_clippy_lint! {
70 /// **What it does:** Detects expressions of the form `--x`.
72 /// **Why is this bad?** It can mislead C/C++ programmers to think `x` was
75 /// **Known problems:** None.
84 "`--x`, which is a double negation of `x` and not a pre-decrement as in C/C++"
87 declare_clippy_lint! {
88 /// **What it does:** Warns on hexadecimal literals with mixed-case letter
91 /// **Why is this bad?** It looks confusing.
93 /// **Known problems:** None.
98 /// let y = 0x1a9BAcD;
101 /// let y = 0x1A9BACD;
103 pub MIXED_CASE_HEX_LITERALS,
105 "hex literals whose letter digits are not consistently upper- or lowercased"
108 declare_clippy_lint! {
109 /// **What it does:** Warns if literal suffixes are not separated by an
112 /// **Why is this bad?** It is much less readable.
114 /// **Known problems:** None.
119 /// let y = 123832i32;
122 /// let y = 123832_i32;
124 pub UNSEPARATED_LITERAL_SUFFIX,
126 "literals whose suffix is not separated by an underscore"
129 declare_clippy_lint! {
130 /// **What it does:** Warns if an integral constant literal starts with `0`.
132 /// **Why is this bad?** In some languages (including the infamous C language
134 /// family), this marks an octal constant. In Rust however, this is a decimal
135 /// constant. This could
136 /// be confusing for both the writer and a reader of the constant.
138 /// **Known problems:** None.
146 /// println!("{}", a);
150 /// prints `123`, while in C:
153 /// #include <stdio.h>
157 /// printf("%d\n", a);
161 /// prints `83` (as `83 == 0o123` while `123 == 0o173`).
162 pub ZERO_PREFIXED_LITERAL,
164 "integer literals starting with `0`"
167 declare_clippy_lint! {
168 /// **What it does:** Warns if a generic shadows a built-in type.
170 /// **Why is this bad?** This gives surprising type errors.
172 /// **Known problems:** None.
177 /// impl<u32> Foo<u32> {
178 /// fn impl_func(&self) -> u32 {
183 pub BUILTIN_TYPE_SHADOW,
185 "shadowing a builtin type"
188 declare_clippy_lint! {
189 /// **What it does:** Checks for patterns in the form `name @ _`.
191 /// **Why is this bad?** It's almost always more readable to just use direct
194 /// **Known problems:** None.
198 /// # let v = Some("abc");
212 pub REDUNDANT_PATTERN,
214 "using `name @ _` in a pattern"
217 declare_clippy_lint! {
218 /// **What it does:** Checks for tuple patterns with a wildcard
219 /// pattern (`_`) is next to a rest pattern (`..`).
221 /// _NOTE_: While `_, ..` means there is at least one element left, `..`
222 /// means there are 0 or more elements left. This can make a difference
223 /// when refactoring, but shouldn't result in errors in the refactored code,
224 /// since the wildcard pattern isn't used anyway.
225 /// **Why is this bad?** The wildcard pattern is unneeded as the rest pattern
226 /// can match that element as well.
228 /// **Known problems:** None.
232 /// # struct TupleStruct(u32, u32, u32);
233 /// # let t = TupleStruct(1, 2, 3);
236 /// TupleStruct(0, .., _) => (),
242 /// TupleStruct(0, ..) => (),
246 pub UNNEEDED_WILDCARD_PATTERN,
248 "tuple patterns with a wildcard pattern (`_`) is next to a rest pattern (`..`)"
251 declare_lint_pass!(MiscEarlyLints => [
252 UNNEEDED_FIELD_PATTERN,
253 DUPLICATE_UNDERSCORE_ARGUMENT,
255 MIXED_CASE_HEX_LITERALS,
256 UNSEPARATED_LITERAL_SUFFIX,
257 ZERO_PREFIXED_LITERAL,
260 UNNEEDED_WILDCARD_PATTERN,
263 impl EarlyLintPass for MiscEarlyLints {
264 fn check_generics(&mut self, cx: &EarlyContext<'_>, gen: &Generics) {
265 for param in &gen.params {
266 if let GenericParamKind::Type { .. } = param.kind {
267 let name = param.ident.as_str();
268 if constants::BUILTIN_TYPES.contains(&&*name) {
273 &format!("this generic shadows the built-in type `{}`", name),
280 fn check_pat(&mut self, cx: &EarlyContext<'_>, pat: &Pat) {
281 if let PatKind::Struct(ref npat, ref pfields, _) = pat.kind {
286 .expect("A path must have at least one segment")
290 for field in pfields {
291 if let PatKind::Wild = field.pat.kind {
295 if !pfields.is_empty() && wilds == pfields.len() {
298 UNNEEDED_FIELD_PATTERN,
300 "all the struct fields are matched to a wildcard pattern, consider using `..`",
302 &format!("try with `{} {{ .. }}` instead", type_name),
307 for field in pfields {
308 if let PatKind::Wild = field.pat.kind {
313 UNNEEDED_FIELD_PATTERN,
315 "you matched a field with a wildcard pattern, consider using `..` instead",
318 let mut normal = vec![];
320 for field in pfields {
321 match field.pat.kind {
324 if let Ok(n) = cx.sess().source_map().span_to_snippet(field.span) {
333 UNNEEDED_FIELD_PATTERN,
335 "you matched a field with a wildcard pattern, consider using `..` \
338 &format!("try with `{} {{ {}, .. }}`", type_name, normal[..].join(", ")),
346 if let PatKind::Ident(left, ident, Some(ref right)) = pat.kind {
347 let left_binding = match left {
348 BindingMode::ByRef(Mutability::Mut) => "ref mut ",
349 BindingMode::ByRef(Mutability::Not) => "ref ",
350 BindingMode::ByValue(..) => "",
353 if let PatKind::Wild = right.kind {
359 "the `{} @ _` pattern can be written as just `{}`",
360 ident.name, ident.name,
363 format!("{}{}", left_binding, ident.name),
364 Applicability::MachineApplicable,
369 check_unneeded_wildcard_pattern(cx, pat);
372 fn check_fn(&mut self, cx: &EarlyContext<'_>, fn_kind: FnKind<'_>, _: Span, _: NodeId) {
373 let mut registered_names: FxHashMap<String, Span> = FxHashMap::default();
375 for arg in &fn_kind.decl().inputs {
376 if let PatKind::Ident(_, ident, None) = arg.pat.kind {
377 let arg_name = ident.to_string();
379 if let Some(arg_name) = arg_name.strip_prefix('_') {
380 if let Some(correspondence) = registered_names.get(arg_name) {
383 DUPLICATE_UNDERSCORE_ARGUMENT,
386 "`{}` already exists, having another argument having almost the same \
387 name makes code comprehension and documentation more difficult",
393 registered_names.insert(arg_name, arg.pat.span);
399 fn check_expr(&mut self, cx: &EarlyContext<'_>, expr: &Expr) {
400 if in_external_macro(cx.sess(), expr.span) {
404 ExprKind::Unary(UnOp::Neg, ref inner) => {
405 if let ExprKind::Unary(UnOp::Neg, _) = inner.kind {
410 "`--x` could be misinterpreted as pre-decrement by C programmers, is usually a no-op",
414 ExprKind::Lit(ref lit) => Self::check_lit(cx, lit),
420 impl MiscEarlyLints {
421 fn check_lit(cx: &EarlyContext<'_>, lit: &Lit) {
422 // We test if first character in snippet is a number, because the snippet could be an expansion
423 // from a built-in macro like `line!()` or a proc-macro like `#[wasm_bindgen]`.
424 // Note that this check also covers special case that `line!()` is eagerly expanded by compiler.
425 // See <https://github.com/rust-lang/rust-clippy/issues/4507> for a regression.
426 // FIXME: Find a better way to detect those cases.
427 let lit_snip = match snippet_opt(cx, lit.span) {
428 Some(snip) if snip.chars().next().map_or(false, |c| c.is_digit(10)) => snip,
432 if let LitKind::Int(value, lit_int_type) = lit.kind {
433 let suffix = match lit_int_type {
434 LitIntType::Signed(ty) => ty.name_str(),
435 LitIntType::Unsigned(ty) => ty.name_str(),
436 LitIntType::Unsuffixed => "",
439 let maybe_last_sep_idx = if let Some(val) = lit_snip.len().checked_sub(suffix.len() + 1) {
442 return; // It's useless so shouldn't lint.
444 // Do not lint when literal is unsuffixed.
445 if !suffix.is_empty() && lit_snip.as_bytes()[maybe_last_sep_idx] != b'_' {
448 UNSEPARATED_LITERAL_SUFFIX,
450 "integer type suffix should be separated by an underscore",
452 format!("{}_{}", &lit_snip[..=maybe_last_sep_idx], suffix),
453 Applicability::MachineApplicable,
457 if lit_snip.starts_with("0x") {
458 if maybe_last_sep_idx <= 2 {
459 // It's meaningless or causes range error.
462 let mut seen = (false, false);
463 for ch in lit_snip.as_bytes()[2..=maybe_last_sep_idx].iter() {
465 b'a'..=b'f' => seen.0 = true,
466 b'A'..=b'F' => seen.1 = true,
469 if seen.0 && seen.1 {
472 MIXED_CASE_HEX_LITERALS,
474 "inconsistent casing in hexadecimal literal",
479 } else if lit_snip.starts_with("0b") || lit_snip.starts_with("0o") {
481 } else if value != 0 && lit_snip.starts_with('0') {
484 ZERO_PREFIXED_LITERAL,
486 "this is a decimal constant",
488 diag.span_suggestion(
490 "if you mean to use a decimal constant, remove the `0` to avoid confusion",
491 lit_snip.trim_start_matches(|c| c == '_' || c == '0').to_string(),
492 Applicability::MaybeIncorrect,
494 diag.span_suggestion(
496 "if you mean to use an octal constant, use `0o`",
497 format!("0o{}", lit_snip.trim_start_matches(|c| c == '_' || c == '0')),
498 Applicability::MaybeIncorrect,
503 } else if let LitKind::Float(_, LitFloatType::Suffixed(float_ty)) = lit.kind {
504 let suffix = float_ty.name_str();
505 let maybe_last_sep_idx = if let Some(val) = lit_snip.len().checked_sub(suffix.len() + 1) {
508 return; // It's useless so shouldn't lint.
510 if lit_snip.as_bytes()[maybe_last_sep_idx] != b'_' {
513 UNSEPARATED_LITERAL_SUFFIX,
515 "float type suffix should be separated by an underscore",
517 format!("{}_{}", &lit_snip[..=maybe_last_sep_idx], suffix),
518 Applicability::MachineApplicable,
525 fn check_unneeded_wildcard_pattern(cx: &EarlyContext<'_>, pat: &Pat) {
526 if let PatKind::TupleStruct(_, ref patterns) | PatKind::Tuple(ref patterns) = pat.kind {
527 fn span_lint(cx: &EarlyContext<'_>, span: Span, only_one: bool) {
530 UNNEEDED_WILDCARD_PATTERN,
533 "this pattern is unneeded as the `..` pattern can match that element"
535 "these patterns are unneeded as the `..` pattern can match those elements"
537 if only_one { "remove it" } else { "remove them" },
539 Applicability::MachineApplicable,
543 if let Some(rest_index) = patterns.iter().position(|pat| pat.is_rest()) {
544 if let Some((left_index, left_pat)) = patterns[..rest_index]
547 .take_while(|pat| matches!(pat.kind, PatKind::Wild))
551 span_lint(cx, left_pat.span.until(patterns[rest_index].span), left_index == 0);
554 if let Some((right_index, right_pat)) = patterns[rest_index + 1..]
556 .take_while(|pat| matches!(pat.kind, PatKind::Wild))
562 patterns[rest_index].span.shrink_to_hi().to(right_pat.span),