compiler/rustc_lint/src/redundant_semicolon.rs

   1 use crate::{EarlyContext, EarlyLintPass, LintContext};
   2 use rustc_ast::{Block, StmtKind};
   3 use rustc_errors::Applicability;
   4 use rustc_span::Span;
   5
   6 declare_lint! {
   7     /// The `redundant_semicolons` lint detects unnecessary trailing
   8     /// semicolons.
   9     ///
  10     /// ### Example
  11     ///
  12     /// ```rust
  13     /// let _ = 123;;
  14     /// ```
  15     ///
  16     /// {{produces}}
  17     ///
  18     /// ### Explanation
  19     ///
  20     /// Extra semicolons are not needed, and may be removed to avoid confusion
  21     /// and visual clutter.
  22     pub REDUNDANT_SEMICOLONS,
  23     Warn,
  24     "detects unnecessary trailing semicolons"
  25 }
  26
  27 declare_lint_pass!(RedundantSemicolons => [REDUNDANT_SEMICOLONS]);
  28
  29 impl EarlyLintPass for RedundantSemicolons {
  30     fn check_block(&mut self, cx: &EarlyContext<'_>, block: &Block) {
  31         let mut seq = None;
  32         for stmt in block.stmts.iter() {
  33             match (&stmt.kind, &mut seq) {
  34                 (StmtKind::Empty, None) => seq = Some((stmt.span, false)),
  35                 (StmtKind::Empty, Some(seq)) => *seq = (seq.0.to(stmt.span), true),
  36                 (_, seq) => maybe_lint_redundant_semis(cx, seq),
  37             }
  38         }
  39         maybe_lint_redundant_semis(cx, &mut seq);
  40     }
  41 }
  42
  43 fn maybe_lint_redundant_semis(cx: &EarlyContext<'_>, seq: &mut Option<(Span, bool)>) {
  44     if let Some((span, multiple)) = seq.take() {
  45         // FIXME: Find a better way of ignoring the trailing
  46         // semicolon from macro expansion
  47         if span == rustc_span::DUMMY_SP {
  48             return;
  49         }
  50
  51         cx.struct_span_lint(REDUNDANT_SEMICOLONS, span, |lint| {
  52             let (msg, rem) = if multiple {
  53                 ("unnecessary trailing semicolons", "remove these semicolons")
  54             } else {
  55                 ("unnecessary trailing semicolon", "remove this semicolon")
  56             };
  57             lint.build(msg).span_suggestion(span, rem, "", Applicability::MaybeIncorrect).emit();
  58         });
  59     }
  60 }