When using suggestions, squash must be enabled

danger/commit_messages/Dangerfile

@@ -80,7 +80,7 @@ def unicode_emoji_regex
   ))x
 end
 
-def lint_commit(commit)
+def lint_commit(commit) # rubocop:disable Metrics/AbcSize
   # For now we'll ignore merge commits, as getting rid of those is a problem
   # separate from enforcing good commit messages.
   return false if commit.message.start_with?('Merge branch')
@@ -114,6 +114,16 @@ def lint_commit(commit)
     )
   end
 
+  # Fail if a suggestion commit is used and squash is not enabled
+  if commit.message.start_with?('Apply suggestion to') && !gitlab.mr_json['squash']
+    fail_commit(
+      commit,
+      'If you are applying suggestions, squash needs to be enabled in the merge request'
+    )
+
+    failures = true
+  end
+
   unless subject_starts_with_capital?(subject)
     fail_commit(commit, 'The commit subject must start with a capital letter')
     failures = true