[UseShorthandTypeNames] Fix shorthand for optional attributed types.

Like with `some/any` type sugar, when we simplify an `Optional` whose
type parameter is an attributed type, we need to wrap it in parentheses
so that the `?` doesn't bind with the contained type.

Fixes swiftlang#657.

Author: allevato

Sources/SwiftFormat/Rules/UseShorthandTypeNames.swift

@@ -238,11 +238,12 @@ public final class UseShorthandTypeNames: SyntaxFormatRule {
   ) -> TypeSyntax {
     var wrappedType = wrappedType
 
-    // Function types and some-or-any types must be wrapped in parentheses before using shorthand
-    // optional syntax, otherwise the "?" will bind incorrectly (in the function case it binds to
-    // only the result, and in the some-or-any case it only binds to the child protocol). Attach the
-    // leading trivia to the left-paren that we're adding in these cases.
+    // Certain types must be wrapped in parentheses before using shorthand optional syntax to avoid
+    // the "?" from binding incorrectly when re-parsed. Attach the leading trivia to the left-paren
+    // that we're adding in these cases.
     switch Syntax(wrappedType).as(SyntaxEnum.self) {
+    case .attributedType(let attributedType):
+      wrappedType = parenthesizedType(attributedType, leadingTrivia: leadingTrivia)
     case .functionType(let functionType):
       wrappedType = parenthesizedType(functionType, leadingTrivia: leadingTrivia)
     case .someOrAnyType(let someOrAnyType):
@@ -319,12 +320,11 @@ public final class UseShorthandTypeNames: SyntaxFormatRule {
   ) -> OptionalChainingExprSyntax? {
     guard var wrappedTypeExpr = expressionRepresentation(of: wrappedType) else { return nil }
 
-    // Function types and some-or-any types must be wrapped in parentheses before using shorthand
-    // optional syntax, otherwise the "?" will bind incorrectly (in the function case it binds to
-    // only the result, and in the some-or-any case it only binds to the child protocol). Attach the
-    // leading trivia to the left-paren that we're adding in these cases.
+    // Certain types must be wrapped in parentheses before using shorthand optional syntax to avoid
+    // the "?" from binding incorrectly when re-parsed. Attach the leading trivia to the left-paren
+    // that we're adding in these cases.
     switch Syntax(wrappedType).as(SyntaxEnum.self) {
-    case .functionType, .someOrAnyType:
+    case .attributedType, .functionType, .someOrAnyType:
       wrappedTypeExpr = parenthesizedExpr(wrappedTypeExpr, leadingTrivia: leadingTrivia)
     default:
       // Otherwise, the argument type can safely become an optional by simply appending a "?". If
@@ -448,6 +448,9 @@ public final class UseShorthandTypeNames: SyntaxFormatRule {
     case .someOrAnyType(let someOrAnyType):
       return ExprSyntax(TypeExprSyntax(type: someOrAnyType))
 
+    case .attributedType(let attributedType):
+      return ExprSyntax(TypeExprSyntax(type: attributedType))
+
     default:
       return nil
     }

Tests/SwiftFormatTests/Rules/UseShorthandTypeNamesTests.swift

@@ -692,4 +692,44 @@ final class UseShorthandTypeNamesTests: LintOrFormatRuleTestCase {
       ]
     )
   }
+
+  func testAttributedTypesInOptionalsAreParenthesized() {
+    // If we need to insert parentheses, verify that we do, but also verify that we don't insert
+    // them unnecessarily.
+    assertFormatting(
+      UseShorthandTypeNames.self,
+      input: """
+        var x: 1️⃣Optional<consuming P> = S()
+        var y: 2️⃣Optional<@Sendable (Int) -> Void> = S()
+        var z = [3️⃣Optional<consuming P>]([S()])
+        var a = [4️⃣Optional<@Sendable (Int) -> Void>]([S()])
+
+        var x: 5️⃣Optional<(consuming P)> = S()
+        var y: 6️⃣Optional<(@Sendable (Int) -> Void)> = S()
+        var z = [7️⃣Optional<(consuming P)>]([S()])
+        var a = [8️⃣Optional<(@Sendable (Int) -> Void)>]([S()])
+        """,
+      expected: """
+        var x: (consuming P)? = S()
+        var y: (@Sendable (Int) -> Void)? = S()
+        var z = [(consuming P)?]([S()])
+        var a = [(@Sendable (Int) -> Void)?]([S()])
+
+        var x: (consuming P)? = S()
+        var y: (@Sendable (Int) -> Void)? = S()
+        var z = [(consuming P)?]([S()])
+        var a = [(@Sendable (Int) -> Void)?]([S()])
+        """,
+      findings: [
+        FindingSpec("1️⃣", message: "use shorthand syntax for this 'Optional' type"),
+        FindingSpec("2️⃣", message: "use shorthand syntax for this 'Optional' type"),
+        FindingSpec("3️⃣", message: "use shorthand syntax for this 'Optional' type"),
+        FindingSpec("4️⃣", message: "use shorthand syntax for this 'Optional' type"),
+        FindingSpec("5️⃣", message: "use shorthand syntax for this 'Optional' type"),
+        FindingSpec("6️⃣", message: "use shorthand syntax for this 'Optional' type"),
+        FindingSpec("7️⃣", message: "use shorthand syntax for this 'Optional' type"),
+        FindingSpec("8️⃣", message: "use shorthand syntax for this 'Optional' type"),
+      ]
+    )
+  }
 }