[SE-0112] Strip the "Code" suffix from imported error types.

The actual code is always the nested type "Code", so it's silly to
have names like "EKErrorCode.Code". Use "EKError.Code" instead.

Author: DougGregor

lib/ClangImporter/ClangImporter.cpp

@@ -2722,11 +2722,14 @@ auto ClangImporter::Implementation::importFullName(
       baseName = baseName.substr(removePrefix.size());
       strippedPrefix = true;
     }
+  }
 
-    // If the error is an error enum, it will be mapped to the 'Code'
-    // enum nested within an NSError-containing struct. Strip the word
-    // "Code" off the end of the name, if it's there, because it's
-    // redundant.
+  // If the error is an error enum, it will be mapped to the 'Code'
+  // enum nested within an NSError-containing struct. Strip the word
+  // "Code" off the end of the name, if it's there, because it's
+  // redundant.
+  if (auto enumDecl = dyn_cast<clang::EnumDecl>(D)) {
+    auto enumInfo = getEnumInfo(enumDecl, &clangSema.getPreprocessor());
     if (enumInfo.isErrorEnum() && baseName.size() > 4 &&
         camel_case::getLastWord(baseName) == "Code")
       baseName = baseName.substr(0, baseName.size() - 4);

stdlib/public/SDK/CloudKit/CloudKit.swift

@@ -2,7 +2,7 @@
 import Foundation
 
 @available(macOS 10.10, iOS 8.0, *)
-extension CKErrorCode {
+extension CKError {
   /// Retrieve partial error results associated by item ID.
   public var partialErrorsByItemID: [NSObject : Error]? {
     return userInfo[CKPartialErrorsByItemIDKey] as? [NSObject : Error]

stdlib/public/SDK/Contacts/Contacts.swift

@@ -14,7 +14,7 @@
 import Foundation
 
 @available(macOS 10.11, iOS 9.0, *)
-extension CNErrorCode {
+extension CNError {
   /// One or more CNContact, CNGroup or CNContainer objects for which
   /// the error applies.
   public var affectedRecords: [AnyObject]? {

test/ClangModules/Inputs/enum-error.h

@@ -12,4 +12,11 @@ typedef NS_ERROR_ENUM(int, TestError, TestErrorDomain) {
   TETwo,
 };
 
+extern NSString *const OtherErrorDomain;
+typedef NS_ERROR_ENUM(int, OtherErrorCode, OtherErrorDomain) {
+  OtherA,
+  OtherB,
+  OtherC,
+};
+
 TestError getErr();

test/ClangModules/enum-error.swift

@@ -16,6 +16,9 @@
 
 import Foundation
 
+func testDropCode(other: OtherError) -> OtherError.Code {
+  return other.code
+}
 
 func testError() {
   let testErrorNSError = NSError(domain: TestErrorDomain,