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
 109 #[derive(Copy, Clone)]
 110 pub struct MiscEarly;
 111
 112 impl LintPass for MiscEarly {
 113     fn get_lints(&self) -> LintArray {
 114         lint_array!(UNNEEDED_FIELD_PATTERN, DUPLICATE_UNDERSCORE_ARGUMENT, REDUNDANT_CLOSURE_CALL,
 115                     DOUBLE_NEG, MIXED_CASE_HEX_LITERALS, UNSEPARATED_LITERAL_SUFFIX)
 116     }
 117 }
 118
 119 impl EarlyLintPass for MiscEarly {
 120     fn check_pat(&mut self, cx: &EarlyContext, pat: &Pat) {
 121         if let PatKind::Struct(ref npat, ref pfields, _) = pat.node {
 122             let mut wilds = 0;
 123             let type_name = npat.segments.last().expect("A path must have at least one segment").identifier.name;
 124
 125             for field in pfields {
 126                 if field.node.pat.node == PatKind::Wild {
 127                     wilds += 1;
 128                 }
 129             }
 130             if !pfields.is_empty() && wilds == pfields.len() {
 131                 span_help_and_lint(cx,
 132                                    UNNEEDED_FIELD_PATTERN,
 133                                    pat.span,
 134                                    "All the struct fields are matched to a wildcard pattern, consider using `..`.",
 135                                    &format!("Try with `{} {{ .. }}` instead", type_name));
 136                 return;
 137             }
 138             if wilds > 0 {
 139                 let mut normal = vec![];
 140
 141                 for field in pfields {
 142                     if field.node.pat.node != PatKind::Wild {
 143                         if let Ok(n) = cx.sess().codemap().span_to_snippet(field.span) {
 144                             normal.push(n);
 145                         }
 146                     }
 147                 }
 148                 for field in pfields {
 149                     if field.node.pat.node == PatKind::Wild {
 150                         wilds -= 1;
 151                         if wilds > 0 {
 152                             span_lint(cx,
 153                                       UNNEEDED_FIELD_PATTERN,
 154                                       field.span,
 155                                       "You matched a field with a wildcard pattern. Consider using `..` instead");
 156                         } else {
 157                             span_help_and_lint(cx,
 158                                                UNNEEDED_FIELD_PATTERN,
 159                                                field.span,
 160                                                "You matched a field with a wildcard pattern. Consider using `..` \
 161                                                 instead",
 162                                                &format!("Try with `{} {{ {}, .. }}`",
 163                                                         type_name,
 164                                                         normal[..].join(", ")));
 165                         }
 166                     }
 167                 }
 168             }
 169         }
 170     }
 171
 172     fn check_fn(&mut self, cx: &EarlyContext, _: FnKind, decl: &FnDecl, _: &Block, _: Span, _: NodeId) {
 173         let mut registered_names: HashMap<String, Span> = HashMap::new();
 174
 175         for arg in &decl.inputs {
 176             if let PatKind::Ident(_, sp_ident, None) = arg.pat.node {
 177                 let arg_name = sp_ident.node.to_string();
 178
 179                 if arg_name.starts_with('_') {
 180                     if let Some(correspondence) = registered_names.get(&arg_name[1..]) {
 181                         span_lint(cx,
 182                                   DUPLICATE_UNDERSCORE_ARGUMENT,
 183                                   *correspondence,
 184                                   &format!("`{}` already exists, having another argument having almost the same \
 185                                             name makes code comprehension and documentation more difficult",
 186                                            arg_name[1..].to_owned()));;
 187                     }
 188                 } else {
 189                     registered_names.insert(arg_name, arg.pat.span);
 190                 }
 191             }
 192         }
 193     }
 194
 195     fn check_expr(&mut self, cx: &EarlyContext, expr: &Expr) {
 196         match expr.node {
 197             ExprKind::Call(ref paren, _) => {
 198                 if let ExprKind::Paren(ref closure) = paren.node {
 199                     if let ExprKind::Closure(_, ref decl, ref block, _) = closure.node {
 200                         span_lint_and_then(cx,
 201                                            REDUNDANT_CLOSURE_CALL,
 202                                            expr.span,
 203                                            "Try not to call a closure in the expression where it is declared.",
 204                                            |db| {
 205                                                if decl.inputs.is_empty() {
 206                                                    let hint = snippet(cx, block.span, "..").into_owned();
 207                                                    db.span_suggestion(expr.span, "Try doing something like: ", hint);
 208                                                }
 209                                            });
 210                     }
 211                 }
 212             }
 213             ExprKind::Unary(UnOp::Neg, ref inner) => {
 214                 if let ExprKind::Unary(UnOp::Neg, _) = inner.node {
 215                     span_lint(cx,
 216                               DOUBLE_NEG,
 217                               expr.span,
 218                               "`--x` could be misinterpreted as pre-decrement by C programmers, is usually a no-op");
 219                 }
 220             }
 221             ExprKind::Lit(ref lit) => {
 222                 if_let_chain! {[
 223                     let LitKind::Int(..) = lit.node,
 224                     let Some(src) = snippet_opt(cx, lit.span),
 225                     let Some(firstch) = src.chars().next(),
 226                     char::to_digit(firstch, 10).is_some()
 227                 ], {
 228                     let mut prev = '\0';
 229                     for ch in src.chars() {
 230                         if ch == 'i' || ch == 'u' {
 231                             if prev != '_' {
 232                                 span_lint(cx, UNSEPARATED_LITERAL_SUFFIX, lit.span,
 233                                           "integer type suffix should be separated by an underscore");
 234                             }
 235                             break;
 236                         }
 237                         prev = ch;
 238                     }
 239                     if src.starts_with("0x") {
 240                         let mut seen = (false, false);
 241                         for ch in src.chars() {
 242                             match ch {
 243                                 'a' ... 'f' => seen.0 = true,
 244                                 'A' ... 'F' => seen.1 = true,
 245                                 'i' | 'u'   => break,   // start of suffix already
 246                                 _ => ()
 247                             }
 248                         }
 249                         if seen.0 && seen.1 {
 250                             span_lint(cx, MIXED_CASE_HEX_LITERALS, lit.span,
 251                                       "inconsistent casing in hexadecimal literal");
 252                         }
 253                     }
 254                 }}
 255                 if_let_chain! {[
 256                     let LitKind::Float(..) = lit.node,
 257                     let Some(src) = snippet_opt(cx, lit.span),
 258                     let Some(firstch) = src.chars().next(),
 259                     char::to_digit(firstch, 10).is_some()
 260                 ], {
 261                     let mut prev = '\0';
 262                     for ch in src.chars() {
 263                         if ch == 'f' {
 264                             if prev != '_' {
 265                                 span_lint(cx, UNSEPARATED_LITERAL_SUFFIX, lit.span,
 266                                           "float type suffix should be separated by an underscore");
 267                             }
 268                             break;
 269                         }
 270                         prev = ch;
 271                     }
 272                 }}
 273             }
 274             _ => ()
 275         }
 276     }
 277
 278     fn check_block(&mut self, cx: &EarlyContext, block: &Block) {
 279         for w in block.stmts.windows(2) {
 280             if_let_chain! {[
 281                 let StmtKind::Local(ref local) = w[0].node,
 282                 let Option::Some(ref t) = local.init,
 283                 let ExprKind::Closure(_, _, _, _) = t.node,
 284                 let PatKind::Ident(_, sp_ident, _) = local.pat.node,
 285                 let StmtKind::Semi(ref second) = w[1].node,
 286                 let ExprKind::Assign(_, ref call) = second.node,
 287                 let ExprKind::Call(ref closure, _) = call.node,
 288                 let ExprKind::Path(_, ref path) = closure.node
 289             ], {
 290                 if sp_ident.node == (&path.segments[0]).identifier {
 291                     span_lint(cx, REDUNDANT_CLOSURE_CALL, second.span, "Closure called just once immediately after it was declared");
 292                 }
 293             }}
 294         }
 295     }
 296 }