Harden Closure Capture Parsing

Fix a regression where we didn't recognize unowned(safe) in closure
captures.

Fixes #722

rdar://99657725

Author: CodaFi

Sources/SwiftParser/Expressions.swift

@@ -1694,15 +1694,17 @@ extension Parser {
           // Parse identifier (',' identifier)*
           var keepGoing: RawTokenSyntax? = nil
           repeat {
+            let unexpected: RawUnexpectedNodesSyntax?
             let name: RawTokenSyntax
             if self.currentToken.isIdentifier {
+              unexpected = nil
               name = self.consumeIdentifier()
             } else {
-              name = self.eat(.wildcardKeyword)
+              (unexpected, name) = self.expect(.wildcardKeyword)
             }
             keepGoing = consume(if: .comma)
             params.append(RawClosureParamSyntax(
-              name: name, trailingComma: keepGoing, arena: self.arena))
+              unexpected, name: name, trailingComma: keepGoing, arena: self.arena))
           } while keepGoing != nil && loopProgress.evaluate(currentToken)
         }
 
@@ -1751,7 +1753,11 @@ extension Parser {
         specifiers.append(self.consumeIdentifier())
         if let lparen = self.consume(if: .leftParen) {
           specifiers.append(lparen)
-          specifiers.append(self.expectWithoutLookahead(.identifier, "unsafe"))
+          if self.currentToken.tokenText == "safe" {
+            specifiers.append(self.expectWithoutLookahead(.identifier, "safe"))
+          } else {
+            specifiers.append(self.expectWithoutLookahead(.identifier, "unsafe"))
+          }
           specifiers.append(self.expectWithoutLookahead(.rightParen))
         }
       } else if (self.currentToken.isIdentifier || self.at(.selfKeyword)) {

Tests/SwiftParserTest/Expressions.swift

@@ -443,7 +443,7 @@ final class ExpressionTests: XCTestCase {
     )
   }
 
-  func testClouserExpression() {
+  func testClosureExpression() {
     AssertParse(
       """
       let :(#^DIAG_1^#..)->

Tests/SwiftParserTest/Types.swift

@@ -39,5 +39,9 @@ final class TypeTests: XCTestCase {
                 throws -> Void in }
                 """,
                 { $0.parseClosureExpression() })
+
+    AssertParse("""
+                { [weak a, unowned(safe) self, b = 3] (a: Int, b: Int, _: Int) -> Int in }
+                """)
   }
 }