clippy_lints/src/misc_early.rs

   1 use rustc::lint::*;
   2 use std::collections::HashMap;
   3 use std::char;
   4 use syntax::ast::*;
   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};
   8
   9 /// **What it does:** Checks for structure field patterns bound to wildcards.
  10 ///
  11 /// **Why is this bad?** Using `..` instead is shorter and leaves the focus on
  12 /// the fields that are actually bound.
  13 ///
  14 /// **Known problems:** None.
  15 ///
  16 /// **Example:**
  17 /// ```rust
  18 /// let { a: _, b: ref b, c: _ } = ..
  19 /// ```
  20 declare_lint! {
  21     pub UNNEEDED_FIELD_PATTERN,
  22     Warn,
  23     "struct fields bound to a wildcard instead of using `..`"
  24 }
  25
  26 /// **What it does:** Checks for function arguments having the similar names
  27 /// differing by an underscore.
  28 ///
  29 /// **Why is this bad?** It affects code readability.
  30 ///
  31 /// **Known problems:** None.
  32 ///
  33 /// **Example:**
  34 /// ```rust
  35 /// fn foo(a: i32, _a: i32) {}
  36 /// ```
  37 declare_lint! {
  38     pub DUPLICATE_UNDERSCORE_ARGUMENT,
  39     Warn,
  40     "function arguments having names which only differ by an underscore"
  41 }
  42
  43 /// **What it does:** Detects closures called in the same expression where they are defined.
  44 ///
  45 /// **Why is this bad?** It is unnecessarily adding to the expression's complexity.
  46 ///
  47 /// **Known problems:** None.
  48 ///
  49 /// **Example:**
  50 /// ```rust
  51 /// (|| 42)()
  52 /// ```
  53 declare_lint! {
  54     pub REDUNDANT_CLOSURE_CALL,
  55     Warn,
  56     "throwaway closures called in the expression they are defined"
  57 }
  58
  59 /// **What it does:** Detects expressions of the form `--x`.
  60 ///
  61 /// **Why is this bad?** It can mislead C/C++ programmers to think `x` was
  62 /// decremented.
  63 ///
  64 /// **Known problems:** None.
  65 ///
  66 /// **Example:**
  67 /// ```rust
  68 /// --x;
  69 /// ```
  70 declare_lint! {
  71     pub DOUBLE_NEG,
  72     Warn,
  73     "`--x`, which is a double negation of `x` and not a pre-decrement as in C/C++"
  74 }
  75
  76 /// **What it does:** Warns on hexadecimal literals with mixed-case letter digits.
  77 ///
  78 /// **Why is this bad?** It looks confusing.
  79 ///
  80 /// **Known problems:** None.
  81 ///
  82 /// **Example:**
  83 /// ```rust
  84 /// let y = 0x1a9BAcD;
  85 /// ```
  86 declare_lint! {
  87     pub MIXED_CASE_HEX_LITERALS,
  88     Warn,
  89     "hex literals whose letter digits are not consistently upper- or lowercased"
  90 }
  91
  92 /// **What it does:** Warns if literal suffixes are not separated by an underscore.
  93 ///
  94 /// **Why is this bad?** It is much less readable.
  95 ///
  96 /// **Known problems:** None.
  97 ///
  98 /// **Example:**
  99 /// ```rust
 100 /// let y = 123832i32;
 101 /// ```
 102 declare_lint! {
 103     pub UNSEPARATED_LITERAL_SUFFIX,
 104     Allow,
 105     "literals whose suffix is not separated by an underscore"
 106 }
 107
 108 /// **What it does:** Warns if an integral constant literal starts with `0`.
 109 ///
 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.
 113 ///
 114 /// **Known problems:** None.
 115 ///
 116 /// **Example:**
 117 ///
 118 /// In Rust:
 119 /// ```rust
 120 /// fn main() {
 121 ///     let a = 0123;
 122 ///     println!("{}", a);
 123 /// }
 124 /// ```
 125 ///
 126 /// prints `123`, while in C:
 127 ///
 128 /// ```c
 129 /// #include <stdio.h>
 130 ///
 131 /// int main() {
 132 ///     int a = 0123;
 133 ///     printf("%d\n", a);
 134 /// }
 135 /// ```
 136 ///
 137 /// prints `83` (as `83 == 0o123` while `123 == 0o173`).
 138 declare_lint! {
 139     pub ZERO_PREFIXED_LITERAL,
 140     Warn,
 141     "integer literals starting with `0`"
 142 }
 143
 144 /// **What it does:** Warns if a generic shadows a built-in type.
 145 ///
 146 /// **Why is this bad?** This gives surprising type errors.
 147 ///
 148 /// **Known problems:** None.
 149 ///
 150 /// **Example:**
 151 ///
 152 /// ```rust
 153 /// impl<u32> Foo<u32> {
 154 ///     fn impl_func(&self) -> u32 {
 155 ///         42
 156 ///     }
 157 /// }
 158 /// ```
 159 declare_lint! {
 160     pub BUILTIN_TYPE_SHADOW,
 161     Warn,
 162     "shadowing a builtin type"
 163 }
 164
 165
 166 #[derive(Copy, Clone)]
 167 pub struct MiscEarly;
 168
 169 impl LintPass for MiscEarly {
 170     fn get_lints(&self) -> LintArray {
 171         lint_array!(UNNEEDED_FIELD_PATTERN,
 172                     DUPLICATE_UNDERSCORE_ARGUMENT,
 173                     REDUNDANT_CLOSURE_CALL,
 174                     DOUBLE_NEG,
 175                     MIXED_CASE_HEX_LITERALS,
 176                     UNSEPARATED_LITERAL_SUFFIX,
 177                     ZERO_PREFIXED_LITERAL,
 178                     BUILTIN_TYPE_SHADOW)
 179     }
 180 }
 181
 182 impl EarlyLintPass for MiscEarly {
 183     fn check_generics(&mut self, cx: &EarlyContext, gen: &Generics) {
 184         for ty in &gen.ty_params {
 185             let name = ty.ident.name.as_str();
 186             if constants::BUILTIN_TYPES.contains(&&*name) {
 187                 span_lint(cx,
 188                           BUILTIN_TYPE_SHADOW,
 189                           ty.span,
 190                           &format!("This generic shadows the built-in type `{}`", name));
 191             }
 192         }
 193     }
 194
 195     fn check_pat(&mut self, cx: &EarlyContext, pat: &Pat) {
 196         if let PatKind::Struct(ref npat, ref pfields, _) = pat.node {
 197             let mut wilds = 0;
 198             let type_name = npat.segments.last().expect("A path must have at least one segment").identifier.name;
 199
 200             for field in pfields {
 201                 if field.node.pat.node == PatKind::Wild {
 202                     wilds += 1;
 203                 }
 204             }
 205             if !pfields.is_empty() && wilds == pfields.len() {
 206                 span_help_and_lint(cx,
 207                                    UNNEEDED_FIELD_PATTERN,
 208                                    pat.span,
 209                                    "All the struct fields are matched to a wildcard pattern, consider using `..`.",
 210                                    &format!("Try with `{} {{ .. }}` instead", type_name));
 211                 return;
 212             }
 213             if wilds > 0 {
 214                 let mut normal = vec![];
 215
 216                 for field in pfields {
 217                     if field.node.pat.node != PatKind::Wild {
 218                         if let Ok(n) = cx.sess().codemap().span_to_snippet(field.span) {
 219                             normal.push(n);
 220                         }
 221                     }
 222                 }
 223                 for field in pfields {
 224                     if field.node.pat.node == PatKind::Wild {
 225                         wilds -= 1;
 226                         if wilds > 0 {
 227                             span_lint(cx,
 228                                       UNNEEDED_FIELD_PATTERN,
 229                                       field.span,
 230                                       "You matched a field with a wildcard pattern. Consider using `..` instead");
 231                         } else {
 232                             span_help_and_lint(cx,
 233                                                UNNEEDED_FIELD_PATTERN,
 234                                                field.span,
 235                                                "You matched a field with a wildcard pattern. Consider using `..` \
 236                                                 instead",
 237                                                &format!("Try with `{} {{ {}, .. }}`",
 238                                                         type_name,
 239                                                         normal[..].join(", ")));
 240                         }
 241                     }
 242                 }
 243             }
 244         }
 245     }
 246
 247     fn check_fn(&mut self, cx: &EarlyContext, _: FnKind, decl: &FnDecl, _: Span, _: NodeId) {
 248         let mut registered_names: HashMap<String, Span> = HashMap::new();
 249
 250         for arg in &decl.inputs {
 251             if let PatKind::Ident(_, sp_ident, None) = arg.pat.node {
 252                 let arg_name = sp_ident.node.to_string();
 253
 254                 if arg_name.starts_with('_') {
 255                     if let Some(correspondence) = registered_names.get(&arg_name[1..]) {
 256                         span_lint(cx,
 257                                   DUPLICATE_UNDERSCORE_ARGUMENT,
 258                                   *correspondence,
 259                                   &format!("`{}` already exists, having another argument having almost the same \
 260                                             name makes code comprehension and documentation more difficult",
 261                                            arg_name[1..].to_owned()));;
 262                     }
 263                 } else {
 264                     registered_names.insert(arg_name, arg.pat.span);
 265                 }
 266             }
 267         }
 268     }
 269
 270     fn check_expr(&mut self, cx: &EarlyContext, expr: &Expr) {
 271         match expr.node {
 272             ExprKind::Call(ref paren, _) => {
 273                 if let ExprKind::Paren(ref closure) = paren.node {
 274                     if let ExprKind::Closure(_, ref decl, ref block, _) = closure.node {
 275                         span_lint_and_then(cx,
 276                                            REDUNDANT_CLOSURE_CALL,
 277                                            expr.span,
 278                                            "Try not to call a closure in the expression where it is declared.",
 279                                            |db| {
 280                             if decl.inputs.is_empty() {
 281                                 let hint = snippet(cx, block.span, "..").into_owned();
 282                                 db.span_suggestion(expr.span, "Try doing something like: ", hint);
 283                             }
 284                         });
 285                     }
 286                 }
 287             },
 288             ExprKind::Unary(UnOp::Neg, ref inner) => {
 289                 if let ExprKind::Unary(UnOp::Neg, _) = inner.node {
 290                     span_lint(cx,
 291                               DOUBLE_NEG,
 292                               expr.span,
 293                               "`--x` could be misinterpreted as pre-decrement by C programmers, is usually a no-op");
 294                 }
 295             },
 296             ExprKind::Lit(ref lit) => {
 297                 if_let_chain! {[
 298                     let LitKind::Int(value, ..) = lit.node,
 299                     let Some(src) = snippet_opt(cx, lit.span),
 300                     let Some(firstch) = src.chars().next(),
 301                     char::to_digit(firstch, 10).is_some()
 302                 ], {
 303                     let mut prev = '\0';
 304                     for ch in src.chars() {
 305                         if ch == 'i' || ch == 'u' {
 306                             if prev != '_' {
 307                                 span_lint(cx, UNSEPARATED_LITERAL_SUFFIX, lit.span,
 308                                           "integer type suffix should be separated by an underscore");
 309                             }
 310                             break;
 311                         }
 312                         prev = ch;
 313                     }
 314                     if src.starts_with("0x") {
 315                         let mut seen = (false, false);
 316                         for ch in src.chars() {
 317                             match ch {
 318                                 'a' ... 'f' => seen.0 = true,
 319                                 'A' ... 'F' => seen.1 = true,
 320                                 'i' | 'u'   => break,   // start of suffix already
 321                                 _ => ()
 322                             }
 323                         }
 324                         if seen.0 && seen.1 {
 325                             span_lint(cx, MIXED_CASE_HEX_LITERALS, lit.span,
 326                                       "inconsistent casing in hexadecimal literal");
 327                         }
 328                     } else if src.starts_with("0b") || src.starts_with("0o") {
 329                         /* nothing to do */
 330                     } else if value != 0 && src.starts_with('0') {
 331                         span_lint_and_then(cx,
 332                                            ZERO_PREFIXED_LITERAL,
 333                                            lit.span,
 334                                            "this is a decimal constant",
 335                                            |db| {
 336                             db.span_suggestion(
 337                                 lit.span,
 338                                 "if you mean to use a decimal constant, remove the `0` to remove confusion:",
 339                                 src[1..].to_string(),
 340                             );
 341                             db.span_suggestion(
 342                                 lit.span,
 343                                 "if you mean to use an octal constant, use `0o`:",
 344                                 format!("0o{}", &src[1..]),
 345                             );
 346                         });
 347                     }
 348                 }}
 349                 if_let_chain! {[
 350                     let LitKind::Float(..) = lit.node,
 351                     let Some(src) = snippet_opt(cx, lit.span),
 352                     let Some(firstch) = src.chars().next(),
 353                     char::to_digit(firstch, 10).is_some()
 354                 ], {
 355                     let mut prev = '\0';
 356                     for ch in src.chars() {
 357                         if ch == 'f' {
 358                             if prev != '_' {
 359                                 span_lint(cx, UNSEPARATED_LITERAL_SUFFIX, lit.span,
 360                                           "float type suffix should be separated by an underscore");
 361                             }
 362                             break;
 363                         }
 364                         prev = ch;
 365                     }
 366                 }}
 367             },
 368             _ => (),
 369         }
 370     }
 371
 372     fn check_block(&mut self, cx: &EarlyContext, block: &Block) {
 373         for w in block.stmts.windows(2) {
 374             if_let_chain! {[
 375                 let StmtKind::Local(ref local) = w[0].node,
 376                 let Option::Some(ref t) = local.init,
 377                 let ExprKind::Closure(_, _, _, _) = t.node,
 378                 let PatKind::Ident(_, sp_ident, _) = local.pat.node,
 379                 let StmtKind::Semi(ref second) = w[1].node,
 380                 let ExprKind::Assign(_, ref call) = second.node,
 381                 let ExprKind::Call(ref closure, _) = call.node,
 382                 let ExprKind::Path(_, ref path) = closure.node
 383             ], {
 384                 if sp_ident.node == (&path.segments[0]).identifier {
 385                     span_lint(
 386                         cx,
 387                         REDUNDANT_CLOSURE_CALL,
 388                         second.span,
 389                         "Closure called just once immediately after it was declared",
 390                     );
 391                 }
 392             }}
 393         }
 394     }
 395 }