Merge pull request #732 from DougGregor/parse-zero-arg-selector

Parse Objective-C zero-argument selectors (e.g., `retain`).

Author: DougGregor

Sources/SwiftParser/Attributes.swift

@@ -451,6 +451,16 @@ extension Parser {
 
       if self.currentToken.isIdentifier || self.currentToken.isKeyword {
         let name = self.consumeAnyToken()
+
+        // If we hit a ')' we may have a zero-argument selector.
+        if self.at(.rightParen) && elements.isEmpty {
+          elements.append(RawObjCSelectorPieceSyntax(
+            name: name,
+            colon: nil,
+            arena: self.arena))
+          continue
+        }
+
         let (unexpectedBeforeColon, colon) = self.expect(.colon)
         elements.append(RawObjCSelectorPieceSyntax(
           name: name,

Tests/SwiftParserTest/Attributes.swift

@@ -57,4 +57,13 @@ final class AttributeTests: XCTestCase {
       ]
     )
   }
+
+  func testObjCAttribute() {
+    AssertParse(
+      """
+      @objc(zeroArg)
+      class A { }
+      """
+    )
+  }
 }