FieldDescribe.cls

public without sharing class FieldDescribe {
	private static final Map<String, SObjectType> SOBJECT_TYPES = Schema.getGlobalDescribe();
	
	private final SObjectField field;
	
	
	public FieldDescribe(SObjectField field) {
		this.field = field;
	}
	
	
	public SObjectType sObjectType() {
		try {
			new Account().put(field, null);
			return Account.SObjectType;
		}
		catch (SObjectException e) {
			return SOBJECT_TYPES.get(e.getMessage().substringBefore('.'));
		}
	}
	
	
	// Note: only for demonstration purposes
	public SObjectType sObjectTypeStable() {
		for(ChildRelationship relationship : parentType().getDescribe().getChildRelationships()) {
			if(relationship.getField() == field) {
				return relationship.getChildSObject();
			}
		}
		return null;
	}
	
	
	public SObjectType parentType() {
		List<SObjectType> parentTypes = parentTypes();
		
		if(parentTypes.size() > 1) {
			throw new CustomException(field + ' is referencing multiple types');
		}
		
		return parentTypes[0];
	}
	
	
	public List<SObjectType> parentTypes() {
		List<SObjectType> result = field.getDescribe().getReferenceTo();
		
		if(result.isEmpty()) {
			throw new CustomException(field + ' is not a reference');
		}
		
		return result;
	}
	
	
	class CustomException extends Exception {}
}