src/librustc_lint/redundant_semicolon.rs

   1 use crate::{EarlyContext, EarlyLintPass, LintContext};
   2 use rustc_ast::ast::{ExprKind, Stmt, StmtKind};
   3 use rustc_errors::Applicability;
   4
   5 declare_lint! {
   6     pub REDUNDANT_SEMICOLON,
   7     Warn,
   8     "detects unnecessary trailing semicolons"
   9 }
  10
  11 declare_lint_pass!(RedundantSemicolon => [REDUNDANT_SEMICOLON]);
  12
  13 impl EarlyLintPass for RedundantSemicolon {
  14     fn check_stmt(&mut self, cx: &EarlyContext<'_>, stmt: &Stmt) {
  15         if let StmtKind::Semi(expr) = &stmt.kind {
  16             if let ExprKind::Tup(ref v) = &expr.kind {
  17                 if v.is_empty() {
  18                     // Strings of excess semicolons are encoded as empty tuple expressions
  19                     // during the parsing stage, so we check for empty tuple expressions
  20                     // which span only semicolons
  21                     if let Ok(source_str) = cx.sess().source_map().span_to_snippet(stmt.span) {
  22                         if source_str.chars().all(|c| c == ';') {
  23                             let multiple = (stmt.span.hi() - stmt.span.lo()).0 > 1;
  24                             let msg = if multiple {
  25                                 "unnecessary trailing semicolons"
  26                             } else {
  27                                 "unnecessary trailing semicolon"
  28                             };
  29                             cx.struct_span_lint(REDUNDANT_SEMICOLON, stmt.span, |lint| {
  30                                 let mut err = lint.build(&msg);
  31                                 let suggest_msg = if multiple {
  32                                     "remove these semicolons"
  33                                 } else {
  34                                     "remove this semicolon"
  35                                 };
  36                                 err.span_suggestion(
  37                                     stmt.span,
  38                                     &suggest_msg,
  39                                     String::new(),
  40                                     Applicability::MaybeIncorrect,
  41                                 );
  42                                 err.emit();
  43                             });
  44                         }
  45                     }
  46                 }
  47             }
  48         }
  49     }
  50 }