Improve C++ case printing

Author: WANGJIEKE

lib/PrintAsClang/DeclAndTypePrinter.cpp

@@ -394,16 +394,17 @@ class DeclAndTypePrinter::Implementation
                                     owningPrinter.interopContext);
       printer.printValueTypeDecl(ED, /*bodyPrinter=*/[&]() {
         ClangSyntaxPrinter syntaxPrinter(os);
-        os << "  enum class cases { ";
+        os << "  enum class cases {";
         llvm::interleaveComma(
             ED->getAllCases(), os, [&](const EnumCaseDecl *caseDecl) {
               llvm::interleaveComma(caseDecl->getElements(), os,
                                     [&](const EnumElementDecl *elementDecl) {
+                                      os << "\n    ";
                                       syntaxPrinter.printIdentifier(
                                           elementDecl->getNameStr());
                                     });
             });
-        os << " };\n";
+        os << "\n  };\n";
       });
       os << outOfLineDefinitions;
       outOfLineDefinitions.clear();

test/Interop/SwiftToCxx/enums/swift-enum-cases-in-cxx.swift

@@ -22,13 +22,26 @@ public enum EnumCaseIsCxxKeyword {
 }
 
 // CHECK: class EnumCaseIsCxxKeyword final {
-// CHECK: enum class cases { first, second, const_ };
+// CHECK:      enum class cases {
+// CHECK-NEXT:   first,
+// CHECK-NEXT:   second,
+// CHECK-NEXT:   const_
+// CHECK-NEXT: };
 
 // CHECK: class EnumCaseIsSwiftKeyword final {
-// CHECK: enum class cases { first, protocol };
+// CHECK:      enum class cases {
+// CHECK-NEXT:   first,
+// CHECK-NEXT:   protocol
+// CHECK-NEXT: };
 
 // CHECK: class EnumMultipleElementsInSingleCase final {
-// CHECK: enum class cases { first, second };
+// CHECK:      enum class cases {
+// CHECK-NEXT:   first,
+// CHECK-NEXT:   second
+// CHECK-NEXT: };
 
 // CHECK: class EnumSingleElementInSingleCase final {
-// CHECK: enum class cases { first, second };
+// CHECK:      enum class cases {
+// CHECK-NEXT:   first,
+// CHECK-NEXT:   second
+// CHECK-NEXT: };