Serialization: Recover from missing raw types on an enum

Recover from a raw type hidden behind an internal or implementation-only
import by dropping the whole enum when the raw type is unavailable. This
scenario should happen only when looking at non-public decl for indexing or
debugging, or if dependencies somehow changed and left behind a stale
swiftmodule file.

rdar://147091863

Author: xymus

lib/Serialization/Deserialization.cpp

@@ -5037,7 +5037,9 @@ class DeclDeserializer {
       theEnum->setImplicit();
     theEnum->setIsObjC(isObjC);
 
-    theEnum->setRawType(MF.getType(rawTypeID));
+    Type rawType;
+    SET_OR_RETURN_ERROR(rawType, MF.getTypeChecked(rawTypeID));
+    theEnum->setRawType(rawType);
 
     handleInherited(theEnum, inheritedIDs);
 

test/Serialization/Recovery/implementation-only-missing.swift

@@ -63,6 +63,24 @@ public protocol HiddenProtocolWithOverride {
 
 public class HiddenClass {}
 
+public struct HiddenRawType: ExpressibleByStringLiteral, Equatable, CustomStringConvertible {
+
+    fileprivate var staticValue: String
+
+    public init(stringLiteral value: String) {
+        self.init(value)
+    }
+
+    public init(_ value: String) {
+        self.staticValue = value
+    }
+
+    public static func == (lhs: HiddenRawType, rhs: HiddenRawType) -> Bool {
+        return lhs.staticValue == rhs.staticValue
+    }
+
+    public var description: String { self.staticValue }
+}
 
 //--- PublicLib.swift
 
@@ -125,6 +143,10 @@ struct StructInheritingFromComposition : CompositionMemberInheriting & Compositi
 class ClassInheritingFromComposition : CompositionMemberInheriting & CompositionMemberSimple {}
 protocol InheritingFromCompositionDirect : CompositionMemberSimple & HiddenProtocol2 {}
 
+// rdar://147091863
+enum InternalEnumWithRawType: HiddenRawType {
+    case a
+}
 
 //--- Client.swift