change magic number unclosed_delimiter_show_limit to const

Signed-off-by: xizheyin <[email protected]>

Author: xizheyin

compiler/rustc_parse/src/lexer/tokentrees.rs

@@ -8,6 +8,8 @@ use super::diagnostics::{
 };
 use super::{Lexer, UnmatchedDelim};
 
+const UNCLOSED_DELIMITER_SHOW_LIMIT: usize = 5;
+
 impl<'psess, 'src> Lexer<'psess, 'src> {
     // Lex into a token stream. The `Spacing` in the result is that of the
     // opening delimiter.
@@ -55,8 +57,7 @@ impl<'psess, 'src> Lexer<'psess, 'src> {
         let msg = "this file contains an unclosed delimiter";
         let mut err = self.dcx().struct_span_err(self.token.span, msg);
 
-        let unclosed_delimiter_show_limit = 5;
-        let len = usize::min(unclosed_delimiter_show_limit, self.diag_info.open_delimiters.len());
+        let len = usize::min(UNCLOSED_DELIMITER_SHOW_LIMIT, self.diag_info.open_delimiters.len());
         for &(_, span) in &self.diag_info.open_delimiters[..len] {
             err.span_label(span, "unclosed delimiter");
             self.diag_info.unmatched_delims.push(UnmatchedDelim {
@@ -67,14 +68,14 @@ impl<'psess, 'src> Lexer<'psess, 'src> {
             });
         }
 
-        if let Some((_, span)) = self.diag_info.open_delimiters.get(unclosed_delimiter_show_limit)
-            && self.diag_info.open_delimiters.len() >= unclosed_delimiter_show_limit + 2
+        if let Some((_, span)) = self.diag_info.open_delimiters.get(UNCLOSED_DELIMITER_SHOW_LIMIT)
+            && self.diag_info.open_delimiters.len() >= UNCLOSED_DELIMITER_SHOW_LIMIT + 2
         {
             err.span_label(
                 *span,
                 format!(
                     "another {} unclosed delimiters begin from here",
-                    self.diag_info.open_delimiters.len() - unclosed_delimiter_show_limit
+                    self.diag_info.open_delimiters.len() - UNCLOSED_DELIMITER_SHOW_LIMIT
                 ),
             );
         }