clippy_lints/src/redundant_field_names.rs

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