Handle missing func keyword

Author: kimdv

Sources/SwiftParser/Declarations.swift

@@ -232,7 +232,7 @@ extension Parser {
     case (.lhs(.extension), let handle)?:
       return RawDeclSyntax(self.parseExtensionDeclaration(attrs, handle))
     case (.lhs(.func), let handle)?:
-      return RawDeclSyntax(self.parseFuncDeclaration(attrs, handle))
+      return RawDeclSyntax(self.parseFuncDeclaration(attrs, isMissingFuncKeyword() ? .missing(.keyword(.func)) : handle))
     case (.lhs(.subscript), let handle)?:
       return RawDeclSyntax(self.parseSubscriptDeclaration(attrs, handle))
     case (.lhs(.`init`), let handle)?:
@@ -283,10 +283,7 @@ extension Parser {
         )
       }
 
-      let isPossibleFuncIdentifier = self.at(.identifier, .wildcard)
-      let isPossibleFuncParen = self.peek(isAt: .leftParen, .binaryOperator)
-      // Treat operators specially because they're likely to be functions.
-      if (isPossibleFuncIdentifier && isPossibleFuncParen) || self.at(anyIn: Operator.self) != nil {
+      if isMissingFuncKeyword() {
         return RawDeclSyntax(self.parseFuncDeclaration(attrs, .missing(.keyword(.func))))
       }
     }
@@ -298,6 +295,13 @@ extension Parser {
       )
     )
   }
+
+  fileprivate mutating func isMissingFuncKeyword() -> Bool {
+    let isPossibleFuncIdentifier = self.at(.identifier, .wildcard)
+    let isPossibleFuncParen = self.peek(isAt: .leftParen, .binaryOperator)
+    // Treat operators specially because they're likely to be functions.
+    return (isPossibleFuncIdentifier && isPossibleFuncParen) || self.at(anyIn: Operator.self) != nil
+  }
 }
 
 extension Parser {

Tests/SwiftParserTest/translated/RecoveryTests.swift

@@ -2107,13 +2107,7 @@ final class RecoveryTests: ParserTestCase {
     )
   }
 
-  func testRecovery120() {
-    assertParse(
-      """
-      //===--- Recovery for wrong decl introducer keyword.
-      """
-    )
-  }
+  // MARK: - Recovery for wrong decl introducer keyword.
 
   func testRecovery121() {
     assertParse(
@@ -2125,19 +2119,19 @@ final class RecoveryTests: ParserTestCase {
       }
       """,
       diagnostics: [
-        // TODO: Old parser expected error on line 2: expected 'func' keyword in instance method declaration
-        DiagnosticSpec(message: "unexpected code 'notAKeyword() {}' before function")
-      ]
+        DiagnosticSpec(message: "expected 'func' in function", fixIts: ["insert 'func'"])
+      ],
+      fixedSource: """
+        class WrongDeclIntroducerKeyword1 {
+          func notAKeyword() {}
+          func foo() {}
+          class func bar() {}
+        }
+        """
     )
   }
 
-  func testRecovery122() {
-    assertParse(
-      """
-      //===--- Recovery for wrong inheritance clause.
-      """
-    )
-  }
+  // MARK: - Recovery for wrong inheritance clause.
 
   func testRecovery123() {
     assertParse(