Fix unusedArguments shadowing bug

Snapshots/Issues/1183.swift

@@ -0,0 +1,21 @@
+func typeMismatch(
+    for symbol: String,
+    index: Int,
+    expected types: [String],
+    got: String
+) -> RuntimeErrorType {
+    var types = Set(types).sorted()
+    if let index = types.firstIndex(of: "block") {
+        types.append(types.remove(at: index))
+    }
+    let expected: String
+    switch types.count {
+    case 1:
+        expected = types[0]
+    case 2:
+        expected = "\(types[0]) or \(types[1])"
+    default:
+        expected = "\(types.dropLast().joined(separator: ", ")), or \(types.last!)"
+    }
+    return .typeMismatch(for: symbol, index: index, expected: expected, got: got)
+}

Snapshots/Issues/1184.swift

@@ -0,0 +1,4 @@
+func foo(index: Int) {
+    for index in 0 ..< 1 {}
+    print(index)
+}

Sources/Rules.swift

@@ -3675,6 +3675,7 @@ public struct _FormatRules {
             var isDeclaration = false
             var wasDeclaration = false
             var isConditional = false
+            var isGuard = false
             var locals = locals
             var tempLocals = Set<String>()
             func pushLocals() {
@@ -3701,6 +3702,8 @@ public struct _FormatRules {
                 }
                 let token = formatter.tokens[i]
                 switch token {
+                case .keyword("guard"):
+                    isGuard = true
                 case .keyword("let"), .keyword("var"), .keyword("func"), .keyword("for"):
                     isDeclaration = true
                     var i = i
@@ -3728,15 +3731,26 @@ public struct _FormatRules {
                         }
                     }
                 case .startOfScope("{"):
-                    if !formatter.isStartOfClosure(at: i) {
-                        pushLocals()
-                    }
                     guard let endIndex = formatter.endOfScope(at: i) else {
                         argNames.removeAll()
                         return
                     }
-                    removeUsed(from: &argNames, with: &associatedData,
-                               locals: locals, in: i + 1 ..< endIndex)
+                    if formatter.isStartOfClosure(at: i) {
+                        removeUsed(from: &argNames, with: &associatedData,
+                                   locals: locals, in: i + 1 ..< endIndex)
+                    } else if isGuard {
+                        removeUsed(from: &argNames, with: &associatedData,
+                                   locals: locals, in: i + 1 ..< endIndex)
+                        pushLocals()
+                    } else {
+                        let prevLocals = locals
+                        pushLocals()
+                        removeUsed(from: &argNames, with: &associatedData,
+                                   locals: locals, in: i + 1 ..< endIndex)
+                        locals = prevLocals
+                    }
+
+                    isGuard = false
                     i = endIndex
                 case .endOfScope("case"), .endOfScope("default"):
                     pushLocals()

Tests/RulesTests+Redundancy.swift

@@ -5161,6 +5161,18 @@ class RedundancyTests: RulesTests {
         testFormatting(for: input, rule: FormatRules.unusedArguments)
     }
 
+    func testShadowedUsedArguments4() {
+        let input = """
+        func foo(bar: Int) {
+            if let bar = baz {
+                return
+            }
+            print(bar)
+        }
+        """
+        testFormatting(for: input, rule: FormatRules.unusedArguments)
+    }
+
     func testTryArgumentNotMarkedUnused() {
         let input = """
         func foo(bar: String) throws -> String? {