clippy_lints/src/redundant_field_names.rs

   1 use crate::utils::{meets_msrv, 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_semver::RustcVersion;
   7 use rustc_session::{declare_tool_lint, impl_lint_pass};
   8
   9 const REDUNDANT_FIELD_NAMES_MSRV: RustcVersion = RustcVersion::new(1, 17, 0);
  10
  11 declare_clippy_lint! {
  12     /// **What it does:** Checks for fields in struct literals where shorthands
  13     /// could be used.
  14     ///
  15     /// **Why is this bad?** If the field and variable names are the same,
  16     /// the field name is redundant.
  17     ///
  18     /// **Known problems:** None.
  19     ///
  20     /// **Example:**
  21     /// ```rust
  22     /// let bar: u8 = 123;
  23     ///
  24     /// struct Foo {
  25     ///     bar: u8,
  26     /// }
  27     ///
  28     /// let foo = Foo { bar: bar };
  29     /// ```
  30     /// the last line can be simplified to
  31     /// ```ignore
  32     /// let foo = Foo { bar };
  33     /// ```
  34     pub REDUNDANT_FIELD_NAMES,
  35     style,
  36     "checks for fields in struct literals where shorthands could be used"
  37 }
  38
  39 pub struct RedundantFieldNames {
  40     msrv: Option<RustcVersion>,
  41 }
  42
  43 impl RedundantFieldNames {
  44     #[must_use]
  45     pub fn new(msrv: Option<RustcVersion>) -> Self {
  46         Self { msrv }
  47     }
  48 }
  49
  50 impl_lint_pass!(RedundantFieldNames => [REDUNDANT_FIELD_NAMES]);
  51
  52 impl EarlyLintPass for RedundantFieldNames {
  53     fn check_expr(&mut self, cx: &EarlyContext<'_>, expr: &Expr) {
  54         if !meets_msrv(self.msrv.as_ref(), &REDUNDANT_FIELD_NAMES_MSRV) {
  55             return;
  56         }
  57
  58         if in_external_macro(cx.sess, expr.span) {
  59             return;
  60         }
  61         if let ExprKind::Struct(_, ref fields, _) = expr.kind {
  62             for field in fields {
  63                 if field.is_shorthand {
  64                     continue;
  65                 }
  66                 if let ExprKind::Path(None, path) = &field.expr.kind {
  67                     if path.segments.len() == 1
  68                         && path.segments[0].ident == field.ident
  69                         && path.segments[0].args.is_none()
  70                     {
  71                         span_lint_and_sugg(
  72                             cx,
  73                             REDUNDANT_FIELD_NAMES,
  74                             field.span,
  75                             "redundant field names in struct initialization",
  76                             "replace it with",
  77                             field.ident.to_string(),
  78                             Applicability::MachineApplicable,
  79                         );
  80                     }
  81                 }
  82             }
  83         }
  84     }
  85     extract_msrv_attr!(EarlyContext);
  86 }