1 use crate::utils::{constants, snippet, snippet_opt, span_help_and_lint, span_lint, span_lint_and_then};
2 use if_chain::if_chain;
3 use rustc::lint::{in_external_macro, EarlyContext, EarlyLintPass, LintArray, LintContext, LintPass};
4 use rustc::{declare_tool_lint, lint_array};
5 use rustc_data_structures::fx::FxHashMap;
6 use rustc_errors::Applicability;
9 use syntax::source_map::Span;
10 use syntax::visit::{walk_expr, FnKind, Visitor};
12 /// **What it does:** Checks for structure field patterns bound to wildcards.
14 /// **Why is this bad?** Using `..` instead is shorter and leaves the focus on
15 /// the fields that are actually bound.
17 /// **Known problems:** None.
21 /// let { a: _, b: ref b, c: _ } = ..
23 declare_clippy_lint! {
24 pub UNNEEDED_FIELD_PATTERN,
26 "struct fields bound to a wildcard instead of using `..`"
29 /// **What it does:** Checks for function arguments having the similar names
30 /// differing by an underscore.
32 /// **Why is this bad?** It affects code readability.
34 /// **Known problems:** None.
38 /// fn foo(a: i32, _a: i32) {}
40 declare_clippy_lint! {
41 pub DUPLICATE_UNDERSCORE_ARGUMENT,
43 "function arguments having names which only differ by an underscore"
46 /// **What it does:** Detects closures called in the same expression where they
49 /// **Why is this bad?** It is unnecessarily adding to the expression's
52 /// **Known problems:** None.
58 declare_clippy_lint! {
59 pub REDUNDANT_CLOSURE_CALL,
61 "throwaway closures called in the expression they are defined"
64 /// **What it does:** Detects expressions of the form `--x`.
66 /// **Why is this bad?** It can mislead C/C++ programmers to think `x` was
69 /// **Known problems:** None.
75 declare_clippy_lint! {
78 "`--x`, which is a double negation of `x` and not a pre-decrement as in C/C++"
81 /// **What it does:** Warns on hexadecimal literals with mixed-case letter
84 /// **Why is this bad?** It looks confusing.
86 /// **Known problems:** None.
90 /// let y = 0x1a9BAcD;
92 declare_clippy_lint! {
93 pub MIXED_CASE_HEX_LITERALS,
95 "hex literals whose letter digits are not consistently upper- or lowercased"
98 /// **What it does:** Warns if literal suffixes are not separated by an
101 /// **Why is this bad?** It is much less readable.
103 /// **Known problems:** None.
107 /// let y = 123832i32;
109 declare_clippy_lint! {
110 pub UNSEPARATED_LITERAL_SUFFIX,
112 "literals whose suffix is not separated by an underscore"
115 /// **What it does:** Warns if an integral constant literal starts with `0`.
117 /// **Why is this bad?** In some languages (including the infamous C language
119 /// family), this marks an octal constant. In Rust however, this is a decimal
120 /// constant. This could
121 /// be confusing for both the writer and a reader of the constant.
123 /// **Known problems:** None.
131 /// println!("{}", a);
135 /// prints `123`, while in C:
138 /// #include <stdio.h>
142 /// printf("%d\n", a);
146 /// prints `83` (as `83 == 0o123` while `123 == 0o173`).
147 declare_clippy_lint! {
148 pub ZERO_PREFIXED_LITERAL,
150 "integer literals starting with `0`"
153 /// **What it does:** Warns if a generic shadows a built-in type.
155 /// **Why is this bad?** This gives surprising type errors.
157 /// **Known problems:** None.
162 /// impl<u32> Foo<u32> {
163 /// fn impl_func(&self) -> u32 {
168 declare_clippy_lint! {
169 pub BUILTIN_TYPE_SHADOW,
171 "shadowing a builtin type"
174 #[derive(Copy, Clone)]
175 pub struct MiscEarly;
177 impl LintPass for MiscEarly {
178 fn get_lints(&self) -> LintArray {
180 UNNEEDED_FIELD_PATTERN,
181 DUPLICATE_UNDERSCORE_ARGUMENT,
182 REDUNDANT_CLOSURE_CALL,
184 MIXED_CASE_HEX_LITERALS,
185 UNSEPARATED_LITERAL_SUFFIX,
186 ZERO_PREFIXED_LITERAL,
192 // Used to find `return` statements or equivalents e.g. `?`
193 struct ReturnVisitor {
199 Self { found_return: false }
203 impl<'ast> Visitor<'ast> for ReturnVisitor {
204 fn visit_expr(&mut self, ex: &'ast Expr) {
205 if let ExprKind::Ret(_) = ex.node {
206 self.found_return = true;
207 } else if let ExprKind::Try(_) = ex.node {
208 self.found_return = true;
215 impl EarlyLintPass for MiscEarly {
216 fn check_generics(&mut self, cx: &EarlyContext<'_>, gen: &Generics) {
217 for param in &gen.params {
218 if let GenericParamKind::Type { .. } = param.kind {
219 let name = param.ident.as_str();
220 if constants::BUILTIN_TYPES.contains(&&*name) {
225 &format!("This generic shadows the built-in type `{}`", name),
232 fn check_pat(&mut self, cx: &EarlyContext<'_>, pat: &Pat, _: &mut bool) {
233 if let PatKind::Struct(ref npat, ref pfields, _) = pat.node {
238 .expect("A path must have at least one segment")
242 for field in pfields {
243 if let PatKind::Wild = field.node.pat.node {
247 if !pfields.is_empty() && wilds == pfields.len() {
250 UNNEEDED_FIELD_PATTERN,
252 "All the struct fields are matched to a wildcard pattern, consider using `..`.",
253 &format!("Try with `{} {{ .. }}` instead", type_name),
258 let mut normal = vec![];
260 for field in pfields {
261 match field.node.pat.node {
264 if let Ok(n) = cx.sess().source_map().span_to_snippet(field.span) {
270 for field in pfields {
271 if let PatKind::Wild = field.node.pat.node {
276 UNNEEDED_FIELD_PATTERN,
278 "You matched a field with a wildcard pattern. Consider using `..` instead",
283 UNNEEDED_FIELD_PATTERN,
285 "You matched a field with a wildcard pattern. Consider using `..` \
287 &format!("Try with `{} {{ {}, .. }}`", type_name, normal[..].join(", ")),
296 fn check_fn(&mut self, cx: &EarlyContext<'_>, _: FnKind<'_>, decl: &FnDecl, _: Span, _: NodeId) {
297 let mut registered_names: FxHashMap<String, Span> = FxHashMap::default();
299 for arg in &decl.inputs {
300 if let PatKind::Ident(_, ident, None) = arg.pat.node {
301 let arg_name = ident.to_string();
303 if arg_name.starts_with('_') {
304 if let Some(correspondence) = registered_names.get(&arg_name[1..]) {
307 DUPLICATE_UNDERSCORE_ARGUMENT,
310 "`{}` already exists, having another argument having almost the same \
311 name makes code comprehension and documentation more difficult",
312 arg_name[1..].to_owned()
317 registered_names.insert(arg_name, arg.pat.span);
323 fn check_expr(&mut self, cx: &EarlyContext<'_>, expr: &Expr) {
324 if in_external_macro(cx.sess(), expr.span) {
328 ExprKind::Call(ref paren, _) => {
329 if let ExprKind::Paren(ref closure) = paren.node {
330 if let ExprKind::Closure(_, _, _, ref decl, ref block, _) = closure.node {
331 let mut visitor = ReturnVisitor::new();
332 visitor.visit_expr(block);
333 if !visitor.found_return {
336 REDUNDANT_CLOSURE_CALL,
338 "Try not to call a closure in the expression where it is declared.",
340 if decl.inputs.is_empty() {
341 let hint = snippet(cx, block.span, "..").into_owned();
342 db.span_suggestion_with_applicability(
344 "Try doing something like: ",
346 Applicability::MachineApplicable, // snippet
355 ExprKind::Unary(UnOp::Neg, ref inner) => {
356 if let ExprKind::Unary(UnOp::Neg, _) = inner.node {
361 "`--x` could be misinterpreted as pre-decrement by C programmers, is usually a no-op",
365 ExprKind::Lit(ref lit) => self.check_lit(cx, lit),
370 fn check_block(&mut self, cx: &EarlyContext<'_>, block: &Block) {
371 for w in block.stmts.windows(2) {
373 if let StmtKind::Local(ref local) = w[0].node;
374 if let Option::Some(ref t) = local.init;
375 if let ExprKind::Closure(..) = t.node;
376 if let PatKind::Ident(_, ident, _) = local.pat.node;
377 if let StmtKind::Semi(ref second) = w[1].node;
378 if let ExprKind::Assign(_, ref call) = second.node;
379 if let ExprKind::Call(ref closure, _) = call.node;
380 if let ExprKind::Path(_, ref path) = closure.node;
382 if ident == path.segments[0].ident {
385 REDUNDANT_CLOSURE_CALL,
387 "Closure called just once immediately after it was declared",
397 fn check_lit(self, cx: &EarlyContext<'_>, lit: &Lit) {
399 if let LitKind::Int(value, ..) = lit.node;
400 if let Some(src) = snippet_opt(cx, lit.span);
401 if let Some(firstch) = src.chars().next();
402 if char::to_digit(firstch, 10).is_some();
405 for ch in src.chars() {
406 if ch == 'i' || ch == 'u' {
408 span_lint(cx, UNSEPARATED_LITERAL_SUFFIX, lit.span,
409 "integer type suffix should be separated by an underscore");
415 if src.starts_with("0x") {
416 let mut seen = (false, false);
417 for ch in src.chars() {
419 'a' ..= 'f' => seen.0 = true,
420 'A' ..= 'F' => seen.1 = true,
421 'i' | 'u' => break, // start of suffix already
425 if seen.0 && seen.1 {
426 span_lint(cx, MIXED_CASE_HEX_LITERALS, lit.span,
427 "inconsistent casing in hexadecimal literal");
429 } else if src.starts_with("0b") || src.starts_with("0o") {
431 } else if value != 0 && src.starts_with('0') {
432 span_lint_and_then(cx,
433 ZERO_PREFIXED_LITERAL,
435 "this is a decimal constant",
437 db.span_suggestion_with_applicability(
439 "if you mean to use a decimal constant, remove the `0` to remove confusion",
440 src.trim_start_matches(|c| c == '_' || c == '0').to_string(),
441 Applicability::MaybeIncorrect,
443 db.span_suggestion_with_applicability(
445 "if you mean to use an octal constant, use `0o`",
446 format!("0o{}", src.trim_start_matches(|c| c == '_' || c == '0')),
447 Applicability::MaybeIncorrect,
454 if let LitKind::Float(..) = lit.node;
455 if let Some(src) = snippet_opt(cx, lit.span);
456 if let Some(firstch) = src.chars().next();
457 if char::to_digit(firstch, 10).is_some();
460 for ch in src.chars() {
463 span_lint(cx, UNSEPARATED_LITERAL_SUFFIX, lit.span,
464 "float type suffix should be separated by an underscore");