clippy_lints/src/redundant_field_names.rs

   1 use syntax::ast::Name;
   2 use rustc::lint::*;
   3 use rustc::hir::*;
   4 use utils::{match_qpath, match_var, span_lint_and_sugg};
   5 use utils::paths;
   6
   7 /// **What it does:** Checks for fields in struct literals where shorthands
   8 /// could be used.
   9 ///
  10 /// **Why is this bad?** If the field and variable names are the same,
  11 /// the field name is redundant.
  12 ///
  13 /// **Known problems:** None.
  14 ///
  15 /// **Example:**
  16 /// ```rust
  17 /// let bar: u8 = 123;
  18 ///
  19 /// struct Foo {
  20 ///     bar: u8,
  21 /// }
  22 ///
  23 /// let foo = Foo{ bar: bar }
  24 /// ```
  25 declare_lint! {
  26     pub REDUNDANT_FIELD_NAMES,
  27     Warn,
  28     "checks for fields in struct literals where shorthands could be used"
  29 }
  30
  31 pub struct RedundantFieldNames;
  32
  33 impl LintPass for RedundantFieldNames {
  34     fn get_lints(&self) -> LintArray {
  35         lint_array!(REDUNDANT_FIELD_NAMES)
  36     }
  37 }
  38
  39 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for RedundantFieldNames {
  40     fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
  41         if let ExprStruct(ref path, ref fields, _) = expr.node {
  42             for field in fields {
  43                 let name = field.name.node;
  44
  45                 if is_range_struct_field(path, &name) {
  46                     continue;
  47                 }
  48
  49                 if match_var(&field.expr, name) && !field.is_shorthand {
  50                     span_lint_and_sugg (
  51                         cx,
  52                         REDUNDANT_FIELD_NAMES,
  53                         field.span,
  54                         "redundant field names in struct initialization",
  55                         "replace it with",
  56                         name.to_string()
  57                     );
  58                 }
  59             }
  60         }
  61     }
  62 }
  63
  64 /// ```rust
  65 /// let start = 0;
  66 /// let _ = start..;
  67 ///
  68 /// let end = 0;
  69 /// let _ = ..end;
  70 ///
  71 /// let _ = start..end;
  72 /// ```
  73 fn is_range_struct_field(path: &QPath, name: &Name) -> bool {
  74     match name.as_str().as_ref() {
  75         "start" => {
  76             match_qpath(path, &paths::RANGE_STD) || match_qpath(path, &paths::RANGE_FROM_STD)
  77                 || match_qpath(path, &paths::RANGE_INCLUSIVE_STD)
  78         },
  79         "end" => {
  80             match_qpath(path, &paths::RANGE_STD) || match_qpath(path, &paths::RANGE_TO_STD)
  81                 || match_qpath(path, &paths::RANGE_INCLUSIVE_STD)
  82                 || match_qpath(path, &paths::RANGE_TO_INCLUSIVE_STD)
  83         },
  84         _ => false,
  85     }
  86 }