compiler/rustc_lint/src/redundant_semicolon.rs

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