Clean up NoLeadingUnderscores (swiftlang#95)

Author: LaurenWhite

tools/swift-format/Sources/Rules/NoLeadingUnderscores.swift

@@ -11,27 +11,27 @@ import SwiftSyntax
 ///
 /// - SeeAlso: https://google.github.io/swift#naming-conventions-are-not-access-control
 public final class NoLeadingUnderscores: SyntaxLintRule {
-  
+
   public override func visit(_ node: AssociatedtypeDeclSyntax) {
     diagnoseUnderscoreViolation(name: node.identifier)
   }
-  
+
   public override func visit(_ node: ClassDeclSyntax) {
     diagnoseUnderscoreViolation(name: node.identifier)
     super.visit(node) // Visit children despite override
   }
-  
+
   public override func visit(_ node: EnumDeclSyntax) {
     diagnoseUnderscoreViolation(name: node.identifier)
     super.visit(node)
   }
-  
+
   public override func visit(_ node: EnumCaseDeclSyntax) {
     for element in node.elements {
       diagnoseUnderscoreViolation(name: element.identifier)
     }
   }
-  
+
   public override func visit(_ node: FunctionDeclSyntax) {
     diagnoseUnderscoreViolation(name: node.identifier)
     // Check parameter names of function
@@ -52,16 +52,16 @@ public final class NoLeadingUnderscores: SyntaxLintRule {
     }
     super.visit(node)
   }
-  
+
   public override func visit(_ node: PrecedenceGroupDeclSyntax) {
     diagnoseUnderscoreViolation(name: node.identifier)
   }
-  
+
   public override func visit(_ node: ProtocolDeclSyntax) {
     diagnoseUnderscoreViolation(name: node.identifier)
     super.visit(node)
   }
-  
+
   public override func visit(_ node: StructDeclSyntax) {
     diagnoseUnderscoreViolation(name: node.identifier)
     // Check generic parameter names
@@ -72,11 +72,11 @@ public final class NoLeadingUnderscores: SyntaxLintRule {
     }
     super.visit(node)
   }
-  
+
   public override func visit(_ node: TypealiasDeclSyntax) {
     diagnoseUnderscoreViolation(name: node.identifier)
   }
-  
+
   public override func visit(_ node: InitializerDeclSyntax) {
     // Check parameter names of initializer
     let parameters = node.parameters.parameterList
@@ -90,26 +90,23 @@ public final class NoLeadingUnderscores: SyntaxLintRule {
     }
     super.visit(node)
   }
-  
+
   public override func visit(_ node: VariableDeclSyntax) {
-    for binding in node.bindings {
-      if let pat = binding.pattern as? IdentifierPatternSyntax {
-        diagnoseUnderscoreViolation(name: pat.identifier)
-      }
+    for id in node.identifiers {
+      diagnoseUnderscoreViolation(name: id.identifier)
     }
     super.visit(node)
   }
-  
+
   func diagnoseUnderscoreViolation(name: TokenSyntax) {
     let leadingChar = name.text.first
-    if leadingChar == "_" {
-      diagnose(.doNotLeadWithUnderscore(identifier: name.text), on: name)
-    }
+    guard leadingChar == "_" else { return }
+    diagnose(.doNotLeadWithUnderscore(identifier: name.text), on: name)
   }
 }
 
 extension Diagnostic.Message {
   static func doNotLeadWithUnderscore(identifier: String) -> Diagnostic.Message {
-    return .init(.warning, "Identifier \(identifier) should not lead with '_'")
+    return .init(.warning, "identifier \(identifier) should not lead with '_'")
   }
 }