Merge pull request swiftlang#139 from google/fix-casts

Fix force cast rule to only fire on "as!".

Author: dabelknap

Sources/SwiftFormatRules/NeverForceUnwrap.swift

@@ -23,8 +23,8 @@ import SwiftSyntax
 /// - SeeAlso: https://google.github.io/swift#force-unwrapping-and-force-casts
 public final class NeverForceUnwrap: SyntaxLintRule {
 
-  // Checks if "XCTest" is an import statement
   public override func visit(_ node: SourceFileSyntax) {
+    // Tracks whether "XCTest" is imported in the source file before processing the individual
     setImportsXCTest(context: context, sourceFile: node)
     super.visit(node)
   }
@@ -35,7 +35,11 @@ public final class NeverForceUnwrap: SyntaxLintRule {
   }
 
   public override func visit(_ node: AsExprSyntax) {
+    // Only fire if we're not in a test file and if there is an exclamation mark following the `as`
+    // keyword.
     guard !context.importsXCTest else { return }
+    guard let questionOrExclamation = node.questionOrExclamationMark else { return }
+    guard questionOrExclamation.tokenKind == .exclamationMark else { return }
     diagnose(.doNotForceCast(name: node.typeName.description), on: node)
   }
 }
@@ -44,6 +48,7 @@ extension Diagnostic.Message {
   static func doNotForceUnwrap(name: String) -> Diagnostic.Message {
     return .init(.warning, "do not force unwrap '\(name)'")
   }
+
   static func doNotForceCast(name: String) -> Diagnostic.Message {
     return .init(.warning, "do not force cast to '\(name)'")
   }