src/librustc_lint/redundant_semicolon.rs

   1 use crate::lint::{EarlyLintPass, LintPass, EarlyContext, LintArray, LintContext};
   2 use syntax::ast::{Stmt, StmtKind, ExprKind};
   3 use syntax::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                             let mut err = cx.struct_span_lint(
  30                                 REDUNDANT_SEMICOLON,
  31                                 stmt.span,
  32                                 &msg
  33                             );
  34                             let suggest_msg = if multiple {
  35                                 "remove these semicolons"
  36                             } else {
  37                                 "remove this semicolon"
  38                             };
  39                             err.span_suggestion(
  40                                 stmt.span,
  41                                 &suggest_msg,
  42                                 String::new(),
  43                                 Applicability::MaybeIncorrect
  44                             );
  45                             err.emit();
  46                         }
  47                     }
  48                 }
  49             }
  50         }
  51     }
  52 }