Remove implicit conversion from DeclBaseName to Identifier

This conversion just existed to aid migration from Identifier to
DeclBaseName and is no longer needed. It will technically not even be
correct once special names are introduced.

Author: ahoppen

include/swift/AST/Identifier.h

@@ -250,11 +250,6 @@ class DeclBaseName {
     return Ident.get() < RHS.Ident.get();
   }
 
-  // TODO: Remove once migration to DeclBaseName has been completed
-  operator Identifier() {
-    return getIdentifier();
-  }
-
   const void *getAsOpaquePointer() const { return Ident.get(); }
 
   static DeclBaseName getFromOpaquePointer(void *P) {

lib/Sema/CSDiag.cpp

@@ -7009,7 +7009,7 @@ static bool diagnoseKeyPathComponents(ConstraintSystem *CS, KeyPathExpr *KPE,
     switch (auto kind = component.getKind()) {
     case KeyPathExpr::Component::Kind::UnresolvedProperty: {
       auto componentFullName = component.getUnresolvedDeclName();
-      componentName = componentFullName.getBaseName();
+      componentName = componentFullName.getBaseIdentifier();
       break;
     }
 

lib/Sema/TypeCheckConstraints.cpp

@@ -1036,7 +1036,7 @@ TypeExpr *PreCheckExpression::simplifyNestedTypeExpr(UnresolvedDotExpr *UDE) {
   if (!UDE->getName().isSimpleName())
     return nullptr;
 
-  auto Name = UDE->getName().getBaseName();
+  auto Name = UDE->getName().getBaseIdentifier();
   auto NameLoc = UDE->getNameLoc().getBaseNameLoc();
 
   // Qualified type lookup with a module base is represented as a DeclRefExpr