swift-format: Eliminate intermediate array in checkForUnrecognizedRules

Author: AnthonyLatsis

Sources/swift-format/Frontend/ConfigurationProvider.swift

@@ -40,9 +40,11 @@ final class ConfigurationProvider {
     // emit them into the diagnosticsEngine as warnings.
     // That way they will be printed out, but we'll continue execution on the valid rules.
 
-    let invalidRules = configuration.rules.filter { !RuleRegistry.rules.keys.contains($0.key) }
-    for rule in invalidRules {
-      diagnosticsEngine.emitWarning("Configuration contains an unrecognized rule: \(rule.key)", location: nil)
+    for (key, _) in configuration.rules {
+      if RuleRegistry.rules.keys.contains(key) {
+        continue
+      }
+      diagnosticsEngine.emitWarning("Configuration contains an unrecognized rule: \(key)", location: nil)
     }
   }