rustc_lint/
nonstandard_style.rs

1use rustc_abi::ExternAbi;
2use rustc_attr_parsing::AttributeParser;
3use rustc_errors::Applicability;
4use rustc_hir::attrs::{AttributeKind, ReprAttr};
5use rustc_hir::def::{DefKind, Res};
6use rustc_hir::def_id::DefId;
7use rustc_hir::intravisit::{FnKind, Visitor};
8use rustc_hir::{Attribute, GenericParamKind, PatExprKind, PatKind, find_attr};
9use rustc_middle::hir::nested_filter::All;
10use rustc_middle::ty::AssocContainer;
11use rustc_session::config::CrateType;
12use rustc_session::{declare_lint, declare_lint_pass};
13use rustc_span::def_id::LocalDefId;
14use rustc_span::{BytePos, Ident, Span, sym};
15use {rustc_ast as ast, rustc_hir as hir};
16
17use crate::lints::{
18    NonCamelCaseType, NonCamelCaseTypeSub, NonSnakeCaseDiag, NonSnakeCaseDiagSub,
19    NonUpperCaseGlobal, NonUpperCaseGlobalSub, NonUpperCaseGlobalSubTool,
20};
21use crate::{EarlyContext, EarlyLintPass, LateContext, LateLintPass, LintContext};
22
23declare_lint! {
24    /// The `non_camel_case_types` lint detects types, variants, traits and
25    /// type parameters that don't have camel case names.
26    ///
27    /// ### Example
28    ///
29    /// ```rust
30    /// struct my_struct;
31    /// ```
32    ///
33    /// {{produces}}
34    ///
35    /// ### Explanation
36    ///
37    /// The preferred style for these identifiers is to use "camel case", such
38    /// as `MyStruct`, where the first letter should not be lowercase, and
39    /// should not use underscores between letters. Underscores are allowed at
40    /// the beginning and end of the identifier, as well as between
41    /// non-letters (such as `X86_64`).
42    pub NON_CAMEL_CASE_TYPES,
43    Warn,
44    "types, variants, traits and type parameters should have camel case names"
45}
46
47declare_lint_pass!(NonCamelCaseTypes => [NON_CAMEL_CASE_TYPES]);
48
49/// Some unicode characters *have* case, are considered upper case or lower case, but they *can't*
50/// be upper cased or lower cased. For the purposes of the lint suggestion, we care about being able
51/// to change the char's case.
52fn char_has_case(c: char) -> bool {
53    let mut l = c.to_lowercase();
54    let mut u = c.to_uppercase();
55    while let Some(l) = l.next() {
56        match u.next() {
57            Some(u) if l != u => return true,
58            _ => {}
59        }
60    }
61    u.next().is_some()
62}
63
64fn is_camel_case(name: &str) -> bool {
65    let name = name.trim_matches('_');
66    if name.is_empty() {
67        return true;
68    }
69
70    // start with a non-lowercase letter rather than non-uppercase
71    // ones (some scripts don't have a concept of upper/lowercase)
72    !name.chars().next().unwrap().is_lowercase()
73        && !name.contains("__")
74        && !name.chars().collect::<Vec<_>>().array_windows().any(|&[fst, snd]| {
75            // contains a capitalisable character followed by, or preceded by, an underscore
76            char_has_case(fst) && snd == '_' || char_has_case(snd) && fst == '_'
77        })
78}
79
80fn to_camel_case(s: &str) -> String {
81    s.trim_matches('_')
82        .split('_')
83        .filter(|component| !component.is_empty())
84        .map(|component| {
85            let mut camel_cased_component = String::new();
86
87            let mut new_word = true;
88            let mut prev_is_lower_case = true;
89
90            for c in component.chars() {
91                // Preserve the case if an uppercase letter follows a lowercase letter, so that
92                // `camelCase` is converted to `CamelCase`.
93                if prev_is_lower_case && c.is_uppercase() {
94                    new_word = true;
95                }
96
97                if new_word {
98                    camel_cased_component.extend(c.to_uppercase());
99                } else {
100                    camel_cased_component.extend(c.to_lowercase());
101                }
102
103                prev_is_lower_case = c.is_lowercase();
104                new_word = false;
105            }
106
107            camel_cased_component
108        })
109        .fold((String::new(), None), |(acc, prev): (String, Option<String>), next| {
110            // separate two components with an underscore if their boundary cannot
111            // be distinguished using an uppercase/lowercase case distinction
112            let join = if let Some(prev) = prev {
113                let l = prev.chars().last().unwrap();
114                let f = next.chars().next().unwrap();
115                !char_has_case(l) && !char_has_case(f)
116            } else {
117                false
118            };
119            (acc + if join { "_" } else { "" } + &next, Some(next))
120        })
121        .0
122}
123
124impl NonCamelCaseTypes {
125    fn check_case(&self, cx: &EarlyContext<'_>, sort: &str, ident: &Ident) {
126        let name = ident.name.as_str();
127
128        if !is_camel_case(name) {
129            let cc = to_camel_case(name);
130            let sub = if *name != cc {
131                NonCamelCaseTypeSub::Suggestion { span: ident.span, replace: cc }
132            } else {
133                NonCamelCaseTypeSub::Label { span: ident.span }
134            };
135            cx.emit_span_lint(
136                NON_CAMEL_CASE_TYPES,
137                ident.span,
138                NonCamelCaseType { sort, name, sub },
139            );
140        }
141    }
142}
143
144impl EarlyLintPass for NonCamelCaseTypes {
145    fn check_item(&mut self, cx: &EarlyContext<'_>, it: &ast::Item) {
146        let has_repr_c = matches!(
147            AttributeParser::parse_limited(cx.sess(), &it.attrs, sym::repr, it.span, it.id, None),
148            Some(Attribute::Parsed(AttributeKind::Repr { reprs, ..})) if reprs.iter().any(|(r, _)| r == &ReprAttr::ReprC)
149        );
150
151        if has_repr_c {
152            return;
153        }
154
155        match &it.kind {
156            ast::ItemKind::TyAlias(box ast::TyAlias { ident, .. })
157            | ast::ItemKind::Enum(ident, ..)
158            | ast::ItemKind::Struct(ident, ..)
159            | ast::ItemKind::Union(ident, ..) => self.check_case(cx, "type", ident),
160            ast::ItemKind::Trait(box ast::Trait { ident, .. }) => {
161                self.check_case(cx, "trait", ident)
162            }
163            ast::ItemKind::TraitAlias(ident, _, _) => self.check_case(cx, "trait alias", ident),
164
165            // N.B. This check is only for inherent associated types, so that we don't lint against
166            // trait impls where we should have warned for the trait definition already.
167            ast::ItemKind::Impl(ast::Impl { of_trait: None, items, .. }) => {
168                for it in items {
169                    // FIXME: this doesn't respect `#[allow(..)]` on the item itself.
170                    if let ast::AssocItemKind::Type(alias) = &it.kind {
171                        self.check_case(cx, "associated type", &alias.ident);
172                    }
173                }
174            }
175            _ => (),
176        }
177    }
178
179    fn check_trait_item(&mut self, cx: &EarlyContext<'_>, it: &ast::AssocItem) {
180        if let ast::AssocItemKind::Type(alias) = &it.kind {
181            self.check_case(cx, "associated type", &alias.ident);
182        }
183    }
184
185    fn check_variant(&mut self, cx: &EarlyContext<'_>, v: &ast::Variant) {
186        self.check_case(cx, "variant", &v.ident);
187    }
188
189    fn check_generic_param(&mut self, cx: &EarlyContext<'_>, param: &ast::GenericParam) {
190        if let ast::GenericParamKind::Type { .. } = param.kind {
191            self.check_case(cx, "type parameter", &param.ident);
192        }
193    }
194}
195
196declare_lint! {
197    /// The `non_snake_case` lint detects variables, methods, functions,
198    /// lifetime parameters and modules that don't have snake case names.
199    ///
200    /// ### Example
201    ///
202    /// ```rust
203    /// let MY_VALUE = 5;
204    /// ```
205    ///
206    /// {{produces}}
207    ///
208    /// ### Explanation
209    ///
210    /// The preferred style for these identifiers is to use "snake case",
211    /// where all the characters are in lowercase, with words separated with a
212    /// single underscore, such as `my_value`.
213    pub NON_SNAKE_CASE,
214    Warn,
215    "variables, methods, functions, lifetime parameters and modules should have snake case names"
216}
217
218declare_lint_pass!(NonSnakeCase => [NON_SNAKE_CASE]);
219
220impl NonSnakeCase {
221    fn to_snake_case(mut name: &str) -> String {
222        let mut words = vec![];
223        // Preserve leading underscores
224        name = name.trim_start_matches(|c: char| {
225            if c == '_' {
226                words.push(String::new());
227                true
228            } else {
229                false
230            }
231        });
232        for s in name.split('_') {
233            let mut last_upper = false;
234            let mut buf = String::new();
235            if s.is_empty() {
236                continue;
237            }
238            for ch in s.chars() {
239                if !buf.is_empty() && buf != "'" && ch.is_uppercase() && !last_upper {
240                    words.push(buf);
241                    buf = String::new();
242                }
243                last_upper = ch.is_uppercase();
244                buf.extend(ch.to_lowercase());
245            }
246            words.push(buf);
247        }
248        words.join("_")
249    }
250
251    /// Checks if a given identifier is snake case, and reports a diagnostic if not.
252    fn check_snake_case(&self, cx: &LateContext<'_>, sort: &str, ident: &Ident) {
253        fn is_snake_case(ident: &str) -> bool {
254            if ident.is_empty() {
255                return true;
256            }
257            let ident = ident.trim_start_matches('\'');
258            let ident = ident.trim_matches('_');
259
260            if ident.contains("__") {
261                return false;
262            }
263
264            // This correctly handles letters in languages with and without
265            // cases, as well as numbers and underscores.
266            !ident.chars().any(char::is_uppercase)
267        }
268
269        let name = ident.name.as_str();
270
271        if !is_snake_case(name) {
272            let span = ident.span;
273            let sc = NonSnakeCase::to_snake_case(name);
274            // We cannot provide meaningful suggestions
275            // if the characters are in the category of "Uppercase Letter".
276            let sub = if name != sc {
277                // We have a valid span in almost all cases, but we don't have one when linting a
278                // crate name provided via the command line.
279                if !span.is_dummy() {
280                    let sc_ident = Ident::from_str_and_span(&sc, span);
281                    if sc_ident.is_reserved() {
282                        // We shouldn't suggest a reserved identifier to fix non-snake-case
283                        // identifiers. Instead, recommend renaming the identifier entirely or, if
284                        // permitted, escaping it to create a raw identifier.
285                        if sc_ident.name.can_be_raw() {
286                            NonSnakeCaseDiagSub::RenameOrConvertSuggestion {
287                                span,
288                                suggestion: sc_ident,
289                            }
290                        } else {
291                            NonSnakeCaseDiagSub::SuggestionAndNote { span }
292                        }
293                    } else {
294                        NonSnakeCaseDiagSub::ConvertSuggestion { span, suggestion: sc.clone() }
295                    }
296                } else {
297                    NonSnakeCaseDiagSub::Help
298                }
299            } else {
300                NonSnakeCaseDiagSub::Label { span }
301            };
302            cx.emit_span_lint(NON_SNAKE_CASE, span, NonSnakeCaseDiag { sort, name, sc, sub });
303        }
304    }
305}
306
307impl<'tcx> LateLintPass<'tcx> for NonSnakeCase {
308    fn check_mod(&mut self, cx: &LateContext<'_>, _: &'tcx hir::Mod<'tcx>, id: hir::HirId) {
309        if id != hir::CRATE_HIR_ID {
310            return;
311        }
312
313        // Issue #45127: don't enforce `snake_case` for binary crates as binaries are not intended
314        // to be distributed and depended on like libraries. The lint is not suppressed for cdylib
315        // or staticlib because it's not clear what the desired lint behavior for those are.
316        if cx.tcx.crate_types().iter().all(|&crate_type| crate_type == CrateType::Executable) {
317            return;
318        }
319
320        let crate_ident = if let Some(name) = &cx.tcx.sess.opts.crate_name {
321            Some(Ident::from_str(name))
322        } else {
323            find_attr!(cx.tcx.hir_attrs(hir::CRATE_HIR_ID), AttributeKind::CrateName{name, name_span,..} => (name, name_span)).map(
324                |(&name, &span)| {
325                    // Discard the double quotes surrounding the literal.
326                    let sp = cx
327                        .sess()
328                        .source_map()
329                        .span_to_snippet(span)
330                        .ok()
331                        .and_then(|snippet| {
332                            let left = snippet.find('"')?;
333                            let right = snippet.rfind('"').map(|pos| snippet.len() - pos)?;
334
335                            Some(
336                                span
337                                    .with_lo(span.lo() + BytePos(left as u32 + 1))
338                                    .with_hi(span.hi() - BytePos(right as u32)),
339                            )
340                        })
341                        .unwrap_or(span);
342
343                    Ident::new(name, sp)
344                },
345            )
346        };
347
348        if let Some(ident) = &crate_ident {
349            self.check_snake_case(cx, "crate", ident);
350        }
351    }
352
353    fn check_generic_param(&mut self, cx: &LateContext<'_>, param: &hir::GenericParam<'_>) {
354        if let GenericParamKind::Lifetime { .. } = param.kind {
355            self.check_snake_case(cx, "lifetime", &param.name.ident());
356        }
357    }
358
359    fn check_fn(
360        &mut self,
361        cx: &LateContext<'_>,
362        fk: FnKind<'_>,
363        _: &hir::FnDecl<'_>,
364        _: &hir::Body<'_>,
365        _: Span,
366        id: LocalDefId,
367    ) {
368        match &fk {
369            FnKind::Method(ident, sig, ..) => match cx.tcx.associated_item(id).container {
370                AssocContainer::InherentImpl => {
371                    if sig.header.abi != ExternAbi::Rust
372                        && find_attr!(cx.tcx.get_all_attrs(id), AttributeKind::NoMangle(..))
373                    {
374                        return;
375                    }
376                    self.check_snake_case(cx, "method", ident);
377                }
378                AssocContainer::Trait => {
379                    self.check_snake_case(cx, "trait method", ident);
380                }
381                AssocContainer::TraitImpl(_) => {}
382            },
383            FnKind::ItemFn(ident, _, header) => {
384                // Skip foreign-ABI #[no_mangle] functions (Issue #31924)
385                if header.abi != ExternAbi::Rust
386                    && find_attr!(cx.tcx.get_all_attrs(id), AttributeKind::NoMangle(..))
387                {
388                    return;
389                }
390                self.check_snake_case(cx, "function", ident);
391            }
392            FnKind::Closure => (),
393        }
394    }
395
396    fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
397        if let hir::ItemKind::Mod(ident, _) = it.kind {
398            self.check_snake_case(cx, "module", &ident);
399        }
400    }
401
402    fn check_ty(&mut self, cx: &LateContext<'_>, ty: &hir::Ty<'_, hir::AmbigArg>) {
403        if let hir::TyKind::FnPtr(hir::FnPtrTy { param_idents, .. }) = &ty.kind {
404            for param_ident in *param_idents {
405                if let Some(param_ident) = param_ident {
406                    self.check_snake_case(cx, "variable", param_ident);
407                }
408            }
409        }
410    }
411
412    fn check_trait_item(&mut self, cx: &LateContext<'_>, item: &hir::TraitItem<'_>) {
413        if let hir::TraitItemKind::Fn(_, hir::TraitFn::Required(param_idents)) = item.kind {
414            self.check_snake_case(cx, "trait method", &item.ident);
415            for param_ident in param_idents {
416                if let Some(param_ident) = param_ident {
417                    self.check_snake_case(cx, "variable", param_ident);
418                }
419            }
420        }
421    }
422
423    fn check_pat(&mut self, cx: &LateContext<'_>, p: &hir::Pat<'_>) {
424        if let PatKind::Binding(_, hid, ident, _) = p.kind {
425            if let hir::Node::PatField(field) = cx.tcx.parent_hir_node(hid) {
426                if !field.is_shorthand {
427                    // Only check if a new name has been introduced, to avoid warning
428                    // on both the struct definition and this pattern.
429                    self.check_snake_case(cx, "variable", &ident);
430                }
431                return;
432            }
433            self.check_snake_case(cx, "variable", &ident);
434        }
435    }
436
437    fn check_struct_def(&mut self, cx: &LateContext<'_>, s: &hir::VariantData<'_>) {
438        for sf in s.fields() {
439            self.check_snake_case(cx, "structure field", &sf.ident);
440        }
441    }
442}
443
444declare_lint! {
445    /// The `non_upper_case_globals` lint detects static items that don't have
446    /// uppercase identifiers.
447    ///
448    /// ### Example
449    ///
450    /// ```rust
451    /// static max_points: i32 = 5;
452    /// ```
453    ///
454    /// {{produces}}
455    ///
456    /// ### Explanation
457    ///
458    /// The preferred style is for static item names to use all uppercase
459    /// letters such as `MAX_POINTS`.
460    pub NON_UPPER_CASE_GLOBALS,
461    Warn,
462    "static constants should have uppercase identifiers"
463}
464
465declare_lint_pass!(NonUpperCaseGlobals => [NON_UPPER_CASE_GLOBALS]);
466
467impl NonUpperCaseGlobals {
468    fn check_upper_case(cx: &LateContext<'_>, sort: &str, did: Option<LocalDefId>, ident: &Ident) {
469        let name = ident.name.as_str();
470        if name.chars().any(|c| c.is_lowercase()) {
471            let uc = NonSnakeCase::to_snake_case(name).to_uppercase();
472
473            // If the item is exported, suggesting changing it's name would be breaking-change
474            // and could break users without a "nice" applicable fix, so let's avoid it.
475            let can_change_usages = if let Some(did) = did {
476                !cx.tcx.effective_visibilities(()).is_exported(did)
477            } else {
478                false
479            };
480
481            // We cannot provide meaningful suggestions
482            // if the characters are in the category of "Lowercase Letter".
483            let sub = if *name != uc {
484                NonUpperCaseGlobalSub::Suggestion {
485                    span: ident.span,
486                    replace: uc.clone(),
487                    applicability: if can_change_usages {
488                        Applicability::MachineApplicable
489                    } else {
490                        Applicability::MaybeIncorrect
491                    },
492                }
493            } else {
494                NonUpperCaseGlobalSub::Label { span: ident.span }
495            };
496
497            struct UsageCollector<'a, 'tcx> {
498                cx: &'tcx LateContext<'a>,
499                did: DefId,
500                collected: Vec<Span>,
501            }
502
503            impl<'v, 'tcx> Visitor<'v> for UsageCollector<'v, 'tcx> {
504                type NestedFilter = All;
505
506                fn maybe_tcx(&mut self) -> Self::MaybeTyCtxt {
507                    self.cx.tcx
508                }
509
510                fn visit_path(
511                    &mut self,
512                    path: &rustc_hir::Path<'v>,
513                    _id: rustc_hir::HirId,
514                ) -> Self::Result {
515                    if let Some(final_seg) = path.segments.last()
516                        && final_seg.res.opt_def_id() == Some(self.did)
517                    {
518                        self.collected.push(final_seg.ident.span);
519                    }
520                }
521            }
522
523            cx.emit_span_lint_lazy(NON_UPPER_CASE_GLOBALS, ident.span, || {
524                // Compute usages lazily as it can expansive and useless when the lint is allowed.
525                // cf. https://github.com/rust-lang/rust/pull/142645#issuecomment-2993024625
526                let usages = if can_change_usages
527                    && *name != uc
528                    && let Some(did) = did
529                {
530                    let mut usage_collector =
531                        UsageCollector { cx, did: did.to_def_id(), collected: Vec::new() };
532                    cx.tcx.hir_walk_toplevel_module(&mut usage_collector);
533                    usage_collector
534                        .collected
535                        .into_iter()
536                        .map(|span| NonUpperCaseGlobalSubTool { span, replace: uc.clone() })
537                        .collect()
538                } else {
539                    vec![]
540                };
541
542                NonUpperCaseGlobal { sort, name, sub, usages }
543            });
544        }
545    }
546}
547
548impl<'tcx> LateLintPass<'tcx> for NonUpperCaseGlobals {
549    fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
550        let attrs = cx.tcx.hir_attrs(it.hir_id());
551        match it.kind {
552            hir::ItemKind::Static(_, ident, ..)
553                if !find_attr!(attrs, AttributeKind::NoMangle(..)) =>
554            {
555                NonUpperCaseGlobals::check_upper_case(
556                    cx,
557                    "static variable",
558                    Some(it.owner_id.def_id),
559                    &ident,
560                );
561            }
562            hir::ItemKind::Const(ident, ..) => {
563                NonUpperCaseGlobals::check_upper_case(
564                    cx,
565                    "constant",
566                    Some(it.owner_id.def_id),
567                    &ident,
568                );
569            }
570            _ => {}
571        }
572    }
573
574    fn check_trait_item(&mut self, cx: &LateContext<'_>, ti: &hir::TraitItem<'_>) {
575        if let hir::TraitItemKind::Const(..) = ti.kind {
576            NonUpperCaseGlobals::check_upper_case(cx, "associated constant", None, &ti.ident);
577        }
578    }
579
580    fn check_impl_item(&mut self, cx: &LateContext<'_>, ii: &hir::ImplItem<'_>) {
581        if let hir::ImplItemKind::Const(..) = ii.kind
582            && let hir::ImplItemImplKind::Inherent { .. } = ii.impl_kind
583        {
584            NonUpperCaseGlobals::check_upper_case(cx, "associated constant", None, &ii.ident);
585        }
586    }
587
588    fn check_pat(&mut self, cx: &LateContext<'_>, p: &hir::Pat<'_>) {
589        // Lint for constants that look like binding identifiers (#7526)
590        if let PatKind::Expr(hir::PatExpr {
591            kind: PatExprKind::Path(hir::QPath::Resolved(None, path)),
592            ..
593        }) = p.kind
594        {
595            if let Res::Def(DefKind::Const, _) = path.res
596                && let [segment] = path.segments
597            {
598                NonUpperCaseGlobals::check_upper_case(
599                    cx,
600                    "constant in pattern",
601                    None,
602                    &segment.ident,
603                );
604            }
605        }
606    }
607
608    fn check_generic_param(&mut self, cx: &LateContext<'_>, param: &hir::GenericParam<'_>) {
609        if let GenericParamKind::Const { .. } = param.kind {
610            NonUpperCaseGlobals::check_upper_case(
611                cx,
612                "const parameter",
613                Some(param.def_id),
614                &param.name.ident(),
615            );
616        }
617    }
618}
619
620#[cfg(test)]
621mod tests;
rustc_lint/nonstandard_style.rs

rustc_lint/
nonstandard_style.rs
