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 /// **What it does:** This lint checks for structure field patterns bound to wildcards.
   9 ///
  10 /// **Why is this bad?** Using `..` instead is shorter and leaves the focus on the fields that are actually bound.
  11 ///
  12 /// **Known problems:** None.
  13 ///
  14 /// **Example:**
  15 /// ```rust
  16 /// let { a: _, b: ref b, c: _ } = ..
  17 /// ```
  18 declare_lint! {
  19     pub UNNEEDED_FIELD_PATTERN, Warn,
  20     "Struct fields are bound to a wildcard instead of using `..`"
  21 }
  22
  23 /// **What it does:** This lint checks for function arguments having the similar names differing by an underscore
  24 ///
  25 /// **Why is this bad?** It affects code readability
  26 ///
  27 /// **Known problems:** None.
  28 ///
  29 /// **Example:**
  30 /// ```rust
  31 /// fn foo(a: i32, _a: i32) {}
  32 /// ```
  33 declare_lint! {
  34     pub DUPLICATE_UNDERSCORE_ARGUMENT, Warn,
  35     "Function arguments having names which only differ by an underscore"
  36 }
  37
  38 /// **What it does:** This lint detects closures called in the same expression where they are defined.
  39 ///
  40 /// **Why is this bad?** It is unnecessarily adding to the expression's complexity.
  41 ///
  42 /// **Known problems:** None.
  43 ///
  44 /// **Example:**
  45 /// ```rust
  46 /// (|| 42)()
  47 /// ```
  48 declare_lint! {
  49     pub REDUNDANT_CLOSURE_CALL, Warn,
  50     "Closures should not be called in the expression they are defined"
  51 }
  52
  53 /// **What it does:** This lint detects expressions of the form `--x`
  54 ///
  55 /// **Why is this bad?** It can mislead C/C++ programmers to think `x` was decremented.
  56 ///
  57 /// **Known problems:** None.
  58 ///
  59 /// **Example:**
  60 /// ```rust
  61 /// --x;
  62 /// ```
  63 declare_lint! {
  64     pub DOUBLE_NEG, Warn,
  65     "`--x` is a double negation of `x` and not a pre-decrement as in C or C++"
  66 }
  67
  68 /// **What it does:** Warns on hexadecimal literals with mixed-case letter digits.
  69 ///
  70 /// **Why is this bad?** It looks confusing.
  71 ///
  72 /// **Known problems:** None.
  73 ///
  74 /// **Example:**
  75 /// ```rust
  76 /// let y = 0x1a9BAcD;
  77 /// ```
  78 declare_lint! {
  79     pub MIXED_CASE_HEX_LITERALS, Warn,
  80     "letter digits in hex literals should be either completely upper- or lowercased"
  81 }
  82
  83 /// **What it does:** Warns if literal suffixes are not separated by an underscore.
  84 ///
  85 /// **Why is this bad?** It is much less readable.
  86 ///
  87 /// **Known problems:** None.
  88 ///
  89 /// **Example:**
  90 /// ```rust
  91 /// let y = 123832i32;
  92 /// ```
  93 declare_lint! {
  94     pub UNSEPARATED_LITERAL_SUFFIX, Allow,
  95     "literal suffixes should be separated with an underscore"
  96 }
  97
  98
  99 #[derive(Copy, Clone)]
 100 pub struct MiscEarly;
 101
 102 impl LintPass for MiscEarly {
 103     fn get_lints(&self) -> LintArray {
 104         lint_array!(UNNEEDED_FIELD_PATTERN, DUPLICATE_UNDERSCORE_ARGUMENT, REDUNDANT_CLOSURE_CALL,
 105                     DOUBLE_NEG, MIXED_CASE_HEX_LITERALS, UNSEPARATED_LITERAL_SUFFIX)
 106     }
 107 }
 108
 109 impl EarlyLintPass for MiscEarly {
 110     fn check_pat(&mut self, cx: &EarlyContext, pat: &Pat) {
 111         if let PatKind::Struct(ref npat, ref pfields, _) = pat.node {
 112             let mut wilds = 0;
 113             let type_name = npat.segments.last().expect("A path must have at least one segment").identifier.name;
 114
 115             for field in pfields {
 116                 if field.node.pat.node == PatKind::Wild {
 117                     wilds += 1;
 118                 }
 119             }
 120             if !pfields.is_empty() && wilds == pfields.len() {
 121                 span_help_and_lint(cx,
 122                                    UNNEEDED_FIELD_PATTERN,
 123                                    pat.span,
 124                                    "All the struct fields are matched to a wildcard pattern, consider using `..`.",
 125                                    &format!("Try with `{} {{ .. }}` instead", type_name));
 126                 return;
 127             }
 128             if wilds > 0 {
 129                 let mut normal = vec![];
 130
 131                 for field in pfields {
 132                     if field.node.pat.node != PatKind::Wild {
 133                         if let Ok(n) = cx.sess().codemap().span_to_snippet(field.span) {
 134                             normal.push(n);
 135                         }
 136                     }
 137                 }
 138                 for field in pfields {
 139                     if field.node.pat.node == PatKind::Wild {
 140                         wilds -= 1;
 141                         if wilds > 0 {
 142                             span_lint(cx,
 143                                       UNNEEDED_FIELD_PATTERN,
 144                                       field.span,
 145                                       "You matched a field with a wildcard pattern. Consider using `..` instead");
 146                         } else {
 147                             span_help_and_lint(cx,
 148                                                UNNEEDED_FIELD_PATTERN,
 149                                                field.span,
 150                                                "You matched a field with a wildcard pattern. Consider using `..` \
 151                                                 instead",
 152                                                &format!("Try with `{} {{ {}, .. }}`",
 153                                                         type_name,
 154                                                         normal[..].join(", ")));
 155                         }
 156                     }
 157                 }
 158             }
 159         }
 160     }
 161
 162     fn check_fn(&mut self, cx: &EarlyContext, _: FnKind, decl: &FnDecl, _: &Block, _: Span, _: NodeId) {
 163         let mut registered_names: HashMap<String, Span> = HashMap::new();
 164
 165         for arg in &decl.inputs {
 166             if let PatKind::Ident(_, sp_ident, None) = arg.pat.node {
 167                 let arg_name = sp_ident.node.to_string();
 168
 169                 if arg_name.starts_with('_') {
 170                     if let Some(correspondence) = registered_names.get(&arg_name[1..]) {
 171                         span_lint(cx,
 172                                   DUPLICATE_UNDERSCORE_ARGUMENT,
 173                                   *correspondence,
 174                                   &format!("`{}` already exists, having another argument having almost the same \
 175                                             name makes code comprehension and documentation more difficult",
 176                                            arg_name[1..].to_owned()));;
 177                     }
 178                 } else {
 179                     registered_names.insert(arg_name, arg.pat.span);
 180                 }
 181             }
 182         }
 183     }
 184
 185     fn check_expr(&mut self, cx: &EarlyContext, expr: &Expr) {
 186         match expr.node {
 187             ExprKind::Call(ref paren, _) => {
 188                 if let ExprKind::Paren(ref closure) = paren.node {
 189                     if let ExprKind::Closure(_, ref decl, ref block, _) = closure.node {
 190                         span_lint_and_then(cx,
 191                                            REDUNDANT_CLOSURE_CALL,
 192                                            expr.span,
 193                                            "Try not to call a closure in the expression where it is declared.",
 194                                            |db| {
 195                                                if decl.inputs.is_empty() {
 196                                                    let hint = snippet(cx, block.span, "..").into_owned();
 197                                                    db.span_suggestion(expr.span, "Try doing something like: ", hint);
 198                                                }
 199                                            });
 200                     }
 201                 }
 202             }
 203             ExprKind::Unary(UnOp::Neg, ref inner) => {
 204                 if let ExprKind::Unary(UnOp::Neg, _) = inner.node {
 205                     span_lint(cx,
 206                               DOUBLE_NEG,
 207                               expr.span,
 208                               "`--x` could be misinterpreted as pre-decrement by C programmers, is usually a no-op");
 209                 }
 210             }
 211             ExprKind::Lit(ref lit) => {
 212                 if_let_chain! {[
 213                     let LitKind::Int(..) = lit.node,
 214                     let Some(src) = snippet_opt(cx, lit.span),
 215                     let Some(firstch) = src.chars().next(),
 216                     char::to_digit(firstch, 10).is_some()
 217                 ], {
 218                     let mut prev = '\0';
 219                     for ch in src.chars() {
 220                         if ch == 'i' || ch == 'u' {
 221                             if prev != '_' {
 222                                 span_lint(cx, UNSEPARATED_LITERAL_SUFFIX, lit.span,
 223                                           "integer type suffix should be separated by an underscore");
 224                             }
 225                             break;
 226                         }
 227                         prev = ch;
 228                     }
 229                     if src.starts_with("0x") {
 230                         let mut seen = (false, false);
 231                         for ch in src.chars() {
 232                             match ch {
 233                                 'a' ... 'f' => seen.0 = true,
 234                                 'A' ... 'F' => seen.1 = true,
 235                                 'i' | 'u'   => break,   // start of suffix already
 236                                 _ => ()
 237                             }
 238                         }
 239                         if seen.0 && seen.1 {
 240                             span_lint(cx, MIXED_CASE_HEX_LITERALS, lit.span,
 241                                       "inconsistent casing in hexadecimal literal");
 242                         }
 243                     }
 244                 }}
 245                 if_let_chain! {[
 246                     let LitKind::Float(..) = lit.node,
 247                     let Some(src) = snippet_opt(cx, lit.span),
 248                     let Some(firstch) = src.chars().next(),
 249                     char::to_digit(firstch, 10).is_some()
 250                 ], {
 251                     let mut prev = '\0';
 252                     for ch in src.chars() {
 253                         if ch == 'f' {
 254                             if prev != '_' {
 255                                 span_lint(cx, UNSEPARATED_LITERAL_SUFFIX, lit.span,
 256                                           "float type suffix should be separated by an underscore");
 257                             }
 258                             break;
 259                         }
 260                         prev = ch;
 261                     }
 262                 }}
 263             }
 264             _ => ()
 265         }
 266     }
 267
 268     fn check_block(&mut self, cx: &EarlyContext, block: &Block) {
 269         for w in block.stmts.windows(2) {
 270             if_let_chain! {[
 271                 let StmtKind::Local(ref local) = w[0].node,
 272                 let Option::Some(ref t) = local.init,
 273                 let ExprKind::Closure(_, _, _, _) = t.node,
 274                 let PatKind::Ident(_, sp_ident, _) = local.pat.node,
 275                 let StmtKind::Semi(ref second) = w[1].node,
 276                 let ExprKind::Assign(_, ref call) = second.node,
 277                 let ExprKind::Call(ref closure, _) = call.node,
 278                 let ExprKind::Path(_, ref path) = closure.node
 279             ], {
 280                 if sp_ident.node == (&path.segments[0]).identifier {
 281                     span_lint(cx, REDUNDANT_CLOSURE_CALL, second.span, "Closure called just once immediately after it was declared");
 282                 }
 283             }}
 284         }
 285     }
 286 }