clippy_lints/src/redundant_field_names.rs

   1 use crate::utils::span_lint_and_sugg;
   2 use rustc::lint::{EarlyContext, EarlyLintPass, LintArray, LintPass};
   3 use rustc::{declare_tool_lint, lint_array};
   4 use rustc_errors::Applicability;
   5 use syntax::ast::*;
   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 /// the last line can be simplified to
  26 /// ```rust
  27 /// let foo = Foo{ bar }
  28 /// ```
  29 declare_clippy_lint! {
  30     pub REDUNDANT_FIELD_NAMES,
  31     style,
  32     "checks for fields in struct literals where shorthands could be used"
  33 }
  34
  35 pub struct RedundantFieldNames;
  36
  37 impl LintPass for RedundantFieldNames {
  38     fn get_lints(&self) -> LintArray {
  39         lint_array!(REDUNDANT_FIELD_NAMES)
  40     }
  41
  42     fn name(&self) -> &'static str {
  43         "RedundantFieldNames"
  44     }
  45 }
  46
  47 impl EarlyLintPass for RedundantFieldNames {
  48     fn check_expr(&mut self, cx: &EarlyContext<'_>, expr: &Expr) {
  49         if let ExprKind::Struct(_, ref fields, _) = expr.node {
  50             for field in fields {
  51                 if field.is_shorthand {
  52                     continue;
  53                 }
  54                 if let ExprKind::Path(None, path) = &field.expr.node {
  55                     if path.segments.len() == 1
  56                         && path.segments[0].ident == field.ident
  57                         && path.segments[0].args.is_none()
  58                     {
  59                         span_lint_and_sugg(
  60                             cx,
  61                             REDUNDANT_FIELD_NAMES,
  62                             field.span,
  63                             "redundant field names in struct initialization",
  64                             "replace it with",
  65                             field.ident.to_string(),
  66                             Applicability::MachineApplicable,
  67                         );
  68                     }
  69                 }
  70             }
  71         }
  72     }
  73 }