clippy_lints/src/redundant_field_names.rs

   1 use crate::utils::span_lint_and_sugg;
   2 use rustc_ast::ast::{Expr, ExprKind};
   3 use rustc_errors::Applicability;
   4 use rustc_lint::{EarlyContext, EarlyLintPass};
   5 use rustc_session::{declare_lint_pass, declare_tool_lint};
   6
   7 declare_clippy_lint! {
   8     /// **What it does:** Checks for fields in struct literals where shorthands
   9     /// could be used.
  10     ///
  11     /// **Why is this bad?** If the field and variable names are the same,
  12     /// the field name is redundant.
  13     ///
  14     /// **Known problems:** None.
  15     ///
  16     /// **Example:**
  17     /// ```rust
  18     /// let bar: u8 = 123;
  19     ///
  20     /// struct Foo {
  21     ///     bar: u8,
  22     /// }
  23     ///
  24     /// let foo = Foo { bar: bar };
  25     /// ```
  26     /// the last line can be simplified to
  27     /// ```ignore
  28     /// let foo = Foo { bar };
  29     /// ```
  30     pub REDUNDANT_FIELD_NAMES,
  31     style,
  32     "checks for fields in struct literals where shorthands could be used"
  33 }
  34
  35 declare_lint_pass!(RedundantFieldNames => [REDUNDANT_FIELD_NAMES]);
  36
  37 impl EarlyLintPass for RedundantFieldNames {
  38     fn check_expr(&mut self, cx: &EarlyContext<'_>, expr: &Expr) {
  39         if let ExprKind::Struct(_, ref fields, _) = expr.kind {
  40             for field in fields {
  41                 if field.is_shorthand {
  42                     continue;
  43                 }
  44                 if let ExprKind::Path(None, path) = &field.expr.kind {
  45                     if path.segments.len() == 1
  46                         && path.segments[0].ident == field.ident
  47                         && path.segments[0].args.is_none()
  48                     {
  49                         span_lint_and_sugg(
  50                             cx,
  51                             REDUNDANT_FIELD_NAMES,
  52                             field.span,
  53                             "redundant field names in struct initialization",
  54                             "replace it with",
  55                             field.ident.to_string(),
  56                             Applicability::MachineApplicable,
  57                         );
  58                     }
  59                 }
  60             }
  61         }
  62     }
  63 }