[Fix rubocop#12374] Fix a false positive for `Layout/SpaceBeforeSemic…

…olon`

Fixes rubocop#12374.

This PR fixes a false positive for `Layout/SpaceBeforeSemicolon`
when a space between an opening lambda brace and a semicolon.

NOTE: When `Token#left_curly_brace?` supports `:tLAMBEG`,
the condition `token.type == :tLAMBEG` can be removed.

changelog/fix_a_false_positive_for_layout_space_before_semicolon.md

@@ -0,0 +1 @@
+* [#12374](https://github.com/rubocop/rubocop/issues/12374): Fix a false positive for `Layout/SpaceBeforeSemicolon` when a space between an opening lambda brace and a semicolon. ([@koic][])

lib/rubocop/cop/mixin/space_before_punctuation.rb

@@ -36,7 +36,7 @@ def space_missing?(token1, token2)
       end
 
       def space_required_after?(token)
-        token.left_curly_brace? && space_required_after_lcurly?
+        (token.left_curly_brace? || token.type == :tLAMBEG) && space_required_after_lcurly?
       end
 
       def space_required_after_lcurly?

spec/rubocop/cop/layout/space_before_semicolon_spec.rb

@@ -45,6 +45,10 @@
       it 'accepts a space between an opening brace and a semicolon' do
         expect_no_offenses('test { ; }')
       end
+
+      it 'accepts a space between an opening lambda brace and a semicolon' do
+        expect_no_offenses('-> { ; }')
+      end
     end
 
     context 'when EnforcedStyle for SpaceInsideBlockBraces is no_space' do