[FixCode] Apply coercion fixits on return statement and initialization as well. rdar://27891589 rdar://27891426

We saw manual migration is necessary on these cases to add 'as Type'. This patch starts
to issue compiler fixits on return statement and initialization just like in other type-mismatch
cases.

Author: nkcsgexi

lib/Sema/CSDiag.cpp

@@ -4026,6 +4026,8 @@ bool FailureDiagnosis::diagnoseContextualConversionError() {
   case CTP_DictionaryKey:
   case CTP_DictionaryValue:
   case CTP_AssignSource:
+  case CTP_Initialization:
+  case CTP_ReturnStmt:
     tryRawRepresentableFixIts(diag, CS, exprType, contextualType,
                               KnownProtocolKind::ExpressibleByIntegerLiteral,
                               expr) ||

test/FixCode/fixits-apply-objc.swift

@@ -21,3 +21,11 @@ func foo(an : Any) {
   let a3 : AnyObject!
   a3 = an
 }
+
+func foo1(_ an : Any) {
+  let obj: AnyObject = an
+}
+
+func foo2(_ messageData: Any?) -> AnyObject? {
+  return messageData
+}

test/FixCode/fixits-apply-objc.swift.result

@@ -21,3 +21,11 @@ func foo(an : Any) {
   let a3 : AnyObject!
   a3 = an as AnyObject!
 }
+
+func foo1(_ an : Any) {
+  let obj: AnyObject = an as AnyObject
+}
+
+func foo2(_ messageData: Any?) -> AnyObject? {
+  return messageData as AnyObject?
+}

test/FixCode/fixits-apply.swift.result

@@ -28,7 +28,7 @@ struct MyMask : OptionSet {
 }
 
 func supported() -> MyMask {
-  return MyMask.Bingo
+  return MyMask(rawValue: UInt(MyMask.Bingo))
 }
 
 struct MyEventMask2 : OptionSet {