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::{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
 145 #[derive(Copy, Clone)]
 146 pub struct MiscEarly;
 147
 148 impl LintPass for MiscEarly {
 149     fn get_lints(&self) -> LintArray {
 150         lint_array!(UNNEEDED_FIELD_PATTERN, DUPLICATE_UNDERSCORE_ARGUMENT, REDUNDANT_CLOSURE_CALL,
 151                     DOUBLE_NEG, MIXED_CASE_HEX_LITERALS, UNSEPARATED_LITERAL_SUFFIX,
 152                     ZERO_PREFIXED_LITERAL)
 153     }
 154 }
 155
 156 impl EarlyLintPass for MiscEarly {
 157     fn check_pat(&mut self, cx: &EarlyContext, pat: &Pat) {
 158         if let PatKind::Struct(ref npat, ref pfields, _) = pat.node {
 159             let mut wilds = 0;
 160             let type_name = npat.segments.last().expect("A path must have at least one segment").identifier.name;
 161
 162             for field in pfields {
 163                 if field.node.pat.node == PatKind::Wild {
 164                     wilds += 1;
 165                 }
 166             }
 167             if !pfields.is_empty() && wilds == pfields.len() {
 168                 span_help_and_lint(cx,
 169                                    UNNEEDED_FIELD_PATTERN,
 170                                    pat.span,
 171                                    "All the struct fields are matched to a wildcard pattern, consider using `..`.",
 172                                    &format!("Try with `{} {{ .. }}` instead", type_name));
 173                 return;
 174             }
 175             if wilds > 0 {
 176                 let mut normal = vec![];
 177
 178                 for field in pfields {
 179                     if field.node.pat.node != PatKind::Wild {
 180                         if let Ok(n) = cx.sess().codemap().span_to_snippet(field.span) {
 181                             normal.push(n);
 182                         }
 183                     }
 184                 }
 185                 for field in pfields {
 186                     if field.node.pat.node == PatKind::Wild {
 187                         wilds -= 1;
 188                         if wilds > 0 {
 189                             span_lint(cx,
 190                                       UNNEEDED_FIELD_PATTERN,
 191                                       field.span,
 192                                       "You matched a field with a wildcard pattern. Consider using `..` instead");
 193                         } else {
 194                             span_help_and_lint(cx,
 195                                                UNNEEDED_FIELD_PATTERN,
 196                                                field.span,
 197                                                "You matched a field with a wildcard pattern. Consider using `..` \
 198                                                 instead",
 199                                                &format!("Try with `{} {{ {}, .. }}`",
 200                                                         type_name,
 201                                                         normal[..].join(", ")));
 202                         }
 203                     }
 204                 }
 205             }
 206         }
 207     }
 208
 209     fn check_fn(&mut self, cx: &EarlyContext, _: FnKind, decl: &FnDecl, _: &Block, _: Span, _: NodeId) {
 210         let mut registered_names: HashMap<String, Span> = HashMap::new();
 211
 212         for arg in &decl.inputs {
 213             if let PatKind::Ident(_, sp_ident, None) = arg.pat.node {
 214                 let arg_name = sp_ident.node.to_string();
 215
 216                 if arg_name.starts_with('_') {
 217                     if let Some(correspondence) = registered_names.get(&arg_name[1..]) {
 218                         span_lint(cx,
 219                                   DUPLICATE_UNDERSCORE_ARGUMENT,
 220                                   *correspondence,
 221                                   &format!("`{}` already exists, having another argument having almost the same \
 222                                             name makes code comprehension and documentation more difficult",
 223                                            arg_name[1..].to_owned()));;
 224                     }
 225                 } else {
 226                     registered_names.insert(arg_name, arg.pat.span);
 227                 }
 228             }
 229         }
 230     }
 231
 232     fn check_expr(&mut self, cx: &EarlyContext, expr: &Expr) {
 233         match expr.node {
 234             ExprKind::Call(ref paren, _) => {
 235                 if let ExprKind::Paren(ref closure) = paren.node {
 236                     if let ExprKind::Closure(_, ref decl, ref block, _) = closure.node {
 237                         span_lint_and_then(cx,
 238                                            REDUNDANT_CLOSURE_CALL,
 239                                            expr.span,
 240                                            "Try not to call a closure in the expression where it is declared.",
 241                                            |db| {
 242                                                if decl.inputs.is_empty() {
 243                                                    let hint = snippet(cx, block.span, "..").into_owned();
 244                                                    db.span_suggestion(expr.span, "Try doing something like: ", hint);
 245                                                }
 246                                            });
 247                     }
 248                 }
 249             }
 250             ExprKind::Unary(UnOp::Neg, ref inner) => {
 251                 if let ExprKind::Unary(UnOp::Neg, _) = inner.node {
 252                     span_lint(cx,
 253                               DOUBLE_NEG,
 254                               expr.span,
 255                               "`--x` could be misinterpreted as pre-decrement by C programmers, is usually a no-op");
 256                 }
 257             }
 258             ExprKind::Lit(ref lit) => {
 259                 if_let_chain! {[
 260                     let LitKind::Int(value, ..) = lit.node,
 261                     let Some(src) = snippet_opt(cx, lit.span),
 262                     let Some(firstch) = src.chars().next(),
 263                     char::to_digit(firstch, 10).is_some()
 264                 ], {
 265                     let mut prev = '\0';
 266                     for ch in src.chars() {
 267                         if ch == 'i' || ch == 'u' {
 268                             if prev != '_' {
 269                                 span_lint(cx, UNSEPARATED_LITERAL_SUFFIX, lit.span,
 270                                           "integer type suffix should be separated by an underscore");
 271                             }
 272                             break;
 273                         }
 274                         prev = ch;
 275                     }
 276                     if src.starts_with("0x") {
 277                         let mut seen = (false, false);
 278                         for ch in src.chars() {
 279                             match ch {
 280                                 'a' ... 'f' => seen.0 = true,
 281                                 'A' ... 'F' => seen.1 = true,
 282                                 'i' | 'u'   => break,   // start of suffix already
 283                                 _ => ()
 284                             }
 285                         }
 286                         if seen.0 && seen.1 {
 287                             span_lint(cx, MIXED_CASE_HEX_LITERALS, lit.span,
 288                                       "inconsistent casing in hexadecimal literal");
 289                         }
 290                     } else if src.starts_with("0b") || src.starts_with("0o") {
 291                         /* nothing to do */
 292                     } else if value != 0 && src.starts_with('0') {
 293                         span_lint_and_then(cx,
 294                                            ZERO_PREFIXED_LITERAL,
 295                                            lit.span,
 296                                            "this is a decimal constant",
 297                                            |db| {
 298                             db.span_suggestion(lit.span, "if you mean to use a decimal constant, remove the `0` to remove confusion:", src[1..].to_string());
 299                             db.span_suggestion(lit.span, "if you mean to use an octal constant, use `0o`:", format!("0o{}", &src[1..]));
 300                         });
 301                     }
 302                 }}
 303                 if_let_chain! {[
 304                     let LitKind::Float(..) = lit.node,
 305                     let Some(src) = snippet_opt(cx, lit.span),
 306                     let Some(firstch) = src.chars().next(),
 307                     char::to_digit(firstch, 10).is_some()
 308                 ], {
 309                     let mut prev = '\0';
 310                     for ch in src.chars() {
 311                         if ch == 'f' {
 312                             if prev != '_' {
 313                                 span_lint(cx, UNSEPARATED_LITERAL_SUFFIX, lit.span,
 314                                           "float type suffix should be separated by an underscore");
 315                             }
 316                             break;
 317                         }
 318                         prev = ch;
 319                     }
 320                 }}
 321             }
 322             _ => ()
 323         }
 324     }
 325
 326     fn check_block(&mut self, cx: &EarlyContext, block: &Block) {
 327         for w in block.stmts.windows(2) {
 328             if_let_chain! {[
 329                 let StmtKind::Local(ref local) = w[0].node,
 330                 let Option::Some(ref t) = local.init,
 331                 let ExprKind::Closure(_, _, _, _) = t.node,
 332                 let PatKind::Ident(_, sp_ident, _) = local.pat.node,
 333                 let StmtKind::Semi(ref second) = w[1].node,
 334                 let ExprKind::Assign(_, ref call) = second.node,
 335                 let ExprKind::Call(ref closure, _) = call.node,
 336                 let ExprKind::Path(_, ref path) = closure.node
 337             ], {
 338                 if sp_ident.node == (&path.segments[0]).identifier {
 339                     span_lint(cx, REDUNDANT_CLOSURE_CALL, second.span, "Closure called just once immediately after it was declared");
 340                 }
 341             }}
 342         }
 343     }
 344 }