2 use std::collections::HashMap;
5 use syntax::codemap::Span;
6 use syntax::visit::FnKind;
7 use utils::{constants, span_lint, span_help_and_lint, snippet, snippet_opt, span_lint_and_then};
9 /// **What it does:** Checks for structure field patterns bound to wildcards.
11 /// **Why is this bad?** Using `..` instead is shorter and leaves the focus on
12 /// the fields that are actually bound.
14 /// **Known problems:** None.
18 /// let { a: _, b: ref b, c: _ } = ..
21 pub UNNEEDED_FIELD_PATTERN,
23 "struct fields bound to a wildcard instead of using `..`"
26 /// **What it does:** Checks for function arguments having the similar names
27 /// differing by an underscore.
29 /// **Why is this bad?** It affects code readability.
31 /// **Known problems:** None.
35 /// fn foo(a: i32, _a: i32) {}
38 pub DUPLICATE_UNDERSCORE_ARGUMENT,
40 "function arguments having names which only differ by an underscore"
43 /// **What it does:** Detects closures called in the same expression where they are defined.
45 /// **Why is this bad?** It is unnecessarily adding to the expression's complexity.
47 /// **Known problems:** None.
54 pub REDUNDANT_CLOSURE_CALL,
56 "throwaway closures called in the expression they are defined"
59 /// **What it does:** Detects expressions of the form `--x`.
61 /// **Why is this bad?** It can mislead C/C++ programmers to think `x` was
64 /// **Known problems:** None.
73 "`--x`, which is a double negation of `x` and not a pre-decrement as in C/C++"
76 /// **What it does:** Warns on hexadecimal literals with mixed-case letter digits.
78 /// **Why is this bad?** It looks confusing.
80 /// **Known problems:** None.
84 /// let y = 0x1a9BAcD;
87 pub MIXED_CASE_HEX_LITERALS,
89 "hex literals whose letter digits are not consistently upper- or lowercased"
92 /// **What it does:** Warns if literal suffixes are not separated by an underscore.
94 /// **Why is this bad?** It is much less readable.
96 /// **Known problems:** None.
100 /// let y = 123832i32;
103 pub UNSEPARATED_LITERAL_SUFFIX,
105 "literals whose suffix is not separated by an underscore"
108 /// **What it does:** Warns if an integral constant literal starts with `0`.
110 /// **Why is this bad?** In some languages (including the infamous C language and most of its
111 /// familly), this marks an octal constant. In Rust however, this is a decimal constant. This could
112 /// be confusing for both the writer and a reader of the constant.
114 /// **Known problems:** None.
122 /// println!("{}", a);
126 /// prints `123`, while in C:
129 /// #include <stdio.h>
133 /// printf("%d\n", a);
137 /// prints `83` (as `83 == 0o123` while `123 == 0o173`).
139 pub ZERO_PREFIXED_LITERAL,
141 "integer literals starting with `0`"
144 /// **What it does:** Warns if a generic shadows a built-in type.
146 /// **Why is this bad?** This gives surprising type errors.
148 /// **Known problems:** None.
153 /// impl<u32> Foo<u32> {
154 /// fn impl_func(&self) -> u32 {
160 pub BUILTIN_TYPE_SHADOW,
162 "shadowing a builtin type"
166 #[derive(Copy, Clone)]
167 pub struct MiscEarly;
169 impl LintPass for MiscEarly {
170 fn get_lints(&self) -> LintArray {
171 lint_array!(UNNEEDED_FIELD_PATTERN, DUPLICATE_UNDERSCORE_ARGUMENT, REDUNDANT_CLOSURE_CALL,
172 DOUBLE_NEG, MIXED_CASE_HEX_LITERALS, UNSEPARATED_LITERAL_SUFFIX,
173 ZERO_PREFIXED_LITERAL, BUILTIN_TYPE_SHADOW)
177 impl EarlyLintPass for MiscEarly {
178 fn check_generics(&mut self, cx: &EarlyContext, gen: &Generics) {
179 for ty in &gen.ty_params {
180 let name = ty.ident.name.as_str();
181 if constants::BUILTIN_TYPES.contains(&&*name) {
185 &format!("This generic shadows the built-in type `{}`", name));
190 fn check_pat(&mut self, cx: &EarlyContext, pat: &Pat) {
191 if let PatKind::Struct(ref npat, ref pfields, _) = pat.node {
193 let type_name = npat.segments.last().expect("A path must have at least one segment").identifier.name;
195 for field in pfields {
196 if field.node.pat.node == PatKind::Wild {
200 if !pfields.is_empty() && wilds == pfields.len() {
201 span_help_and_lint(cx,
202 UNNEEDED_FIELD_PATTERN,
204 "All the struct fields are matched to a wildcard pattern, consider using `..`.",
205 &format!("Try with `{} {{ .. }}` instead", type_name));
209 let mut normal = vec![];
211 for field in pfields {
212 if field.node.pat.node != PatKind::Wild {
213 if let Ok(n) = cx.sess().codemap().span_to_snippet(field.span) {
218 for field in pfields {
219 if field.node.pat.node == PatKind::Wild {
223 UNNEEDED_FIELD_PATTERN,
225 "You matched a field with a wildcard pattern. Consider using `..` instead");
227 span_help_and_lint(cx,
228 UNNEEDED_FIELD_PATTERN,
230 "You matched a field with a wildcard pattern. Consider using `..` \
232 &format!("Try with `{} {{ {}, .. }}`",
234 normal[..].join(", ")));
242 fn check_fn(&mut self, cx: &EarlyContext, _: FnKind, decl: &FnDecl, _: Span, _: NodeId) {
243 let mut registered_names: HashMap<String, Span> = HashMap::new();
245 for arg in &decl.inputs {
246 if let PatKind::Ident(_, sp_ident, None) = arg.pat.node {
247 let arg_name = sp_ident.node.to_string();
249 if arg_name.starts_with('_') {
250 if let Some(correspondence) = registered_names.get(&arg_name[1..]) {
252 DUPLICATE_UNDERSCORE_ARGUMENT,
254 &format!("`{}` already exists, having another argument having almost the same \
255 name makes code comprehension and documentation more difficult",
256 arg_name[1..].to_owned()));;
259 registered_names.insert(arg_name, arg.pat.span);
265 fn check_expr(&mut self, cx: &EarlyContext, expr: &Expr) {
267 ExprKind::Call(ref paren, _) => {
268 if let ExprKind::Paren(ref closure) = paren.node {
269 if let ExprKind::Closure(_, ref decl, ref block, _) = closure.node {
270 span_lint_and_then(cx,
271 REDUNDANT_CLOSURE_CALL,
273 "Try not to call a closure in the expression where it is declared.",
275 if decl.inputs.is_empty() {
276 let hint = snippet(cx, block.span, "..").into_owned();
277 db.span_suggestion(expr.span, "Try doing something like: ", hint);
283 ExprKind::Unary(UnOp::Neg, ref inner) => {
284 if let ExprKind::Unary(UnOp::Neg, _) = inner.node {
288 "`--x` could be misinterpreted as pre-decrement by C programmers, is usually a no-op");
291 ExprKind::Lit(ref lit) => {
293 let LitKind::Int(value, ..) = lit.node,
294 let Some(src) = snippet_opt(cx, lit.span),
295 let Some(firstch) = src.chars().next(),
296 char::to_digit(firstch, 10).is_some()
299 for ch in src.chars() {
300 if ch == 'i' || ch == 'u' {
302 span_lint(cx, UNSEPARATED_LITERAL_SUFFIX, lit.span,
303 "integer type suffix should be separated by an underscore");
309 if src.starts_with("0x") {
310 let mut seen = (false, false);
311 for ch in src.chars() {
313 'a' ... 'f' => seen.0 = true,
314 'A' ... 'F' => seen.1 = true,
315 'i' | 'u' => break, // start of suffix already
319 if seen.0 && seen.1 {
320 span_lint(cx, MIXED_CASE_HEX_LITERALS, lit.span,
321 "inconsistent casing in hexadecimal literal");
323 } else if src.starts_with("0b") || src.starts_with("0o") {
325 } else if value != 0 && src.starts_with('0') {
326 span_lint_and_then(cx,
327 ZERO_PREFIXED_LITERAL,
329 "this is a decimal constant",
331 db.span_suggestion(lit.span, "if you mean to use a decimal constant, remove the `0` to remove confusion:", src[1..].to_string());
332 db.span_suggestion(lit.span, "if you mean to use an octal constant, use `0o`:", format!("0o{}", &src[1..]));
337 let LitKind::Float(..) = lit.node,
338 let Some(src) = snippet_opt(cx, lit.span),
339 let Some(firstch) = src.chars().next(),
340 char::to_digit(firstch, 10).is_some()
343 for ch in src.chars() {
346 span_lint(cx, UNSEPARATED_LITERAL_SUFFIX, lit.span,
347 "float type suffix should be separated by an underscore");
359 fn check_block(&mut self, cx: &EarlyContext, block: &Block) {
360 for w in block.stmts.windows(2) {
362 let StmtKind::Local(ref local) = w[0].node,
363 let Option::Some(ref t) = local.init,
364 let ExprKind::Closure(_, _, _, _) = t.node,
365 let PatKind::Ident(_, sp_ident, _) = local.pat.node,
366 let StmtKind::Semi(ref second) = w[1].node,
367 let ExprKind::Assign(_, ref call) = second.node,
368 let ExprKind::Call(ref closure, _) = call.node,
369 let ExprKind::Path(_, ref path) = closure.node
371 if sp_ident.node == (&path.segments[0]).identifier {
372 span_lint(cx, REDUNDANT_CLOSURE_CALL, second.span, "Closure called just once immediately after it was declared");