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_middle::lint::in_external_macro;
   6 use rustc_session::{declare_lint_pass, declare_tool_lint};
   7
   8 declare_clippy_lint! {
   9     /// **What it does:** Checks for fields in struct literals where shorthands
  10     /// could be used.
  11     ///
  12     /// **Why is this bad?** If the field and variable names are the same,
  13     /// the field name is redundant.
  14     ///
  15     /// **Known problems:** None.
  16     ///
  17     /// **Example:**
  18     /// ```rust
  19     /// let bar: u8 = 123;
  20     ///
  21     /// struct Foo {
  22     ///     bar: u8,
  23     /// }
  24     ///
  25     /// let foo = Foo { bar: bar };
  26     /// ```
  27     /// the last line can be simplified to
  28     /// ```ignore
  29     /// let foo = Foo { bar };
  30     /// ```
  31     pub REDUNDANT_FIELD_NAMES,
  32     style,
  33     "checks for fields in struct literals where shorthands could be used"
  34 }
  35
  36 declare_lint_pass!(RedundantFieldNames => [REDUNDANT_FIELD_NAMES]);
  37
  38 impl EarlyLintPass for RedundantFieldNames {
  39     fn check_expr(&mut self, cx: &EarlyContext<'_>, expr: &Expr) {
  40         if in_external_macro(cx.sess, expr.span) {
  41             return;
  42         }
  43         if let ExprKind::Struct(_, ref fields, _) = expr.kind {
  44             for field in fields {
  45                 if field.is_shorthand {
  46                     continue;
  47                 }
  48                 if let ExprKind::Path(None, path) = &field.expr.kind {
  49                     if path.segments.len() == 1
  50                         && path.segments[0].ident == field.ident
  51                         && path.segments[0].args.is_none()
  52                     {
  53                         span_lint_and_sugg(
  54                             cx,
  55                             REDUNDANT_FIELD_NAMES,
  56                             field.span,
  57                             "redundant field names in struct initialization",
  58                             "replace it with",
  59                             field.ident.to_string(),
  60                             Applicability::MachineApplicable,
  61                         );
  62                     }
  63                 }
  64             }
  65         }
  66     }
  67 }