Improve needs error reporting (#1303)

* Raise helpful error if the same needs is not unique

* Improve error message if duplicate needs found

* Removed test that only used to force a compilation failure

* fixed formatting

* Removed Changelog comments

* Removed deliberately failing test

Co-authored-by: David Simmons <davidsimmons@davids-mbp.home>

src/lucky/assignable.cr

@@ -30,6 +30,17 @@ module Lucky::Assignable
         {% raise "Using '?' in a 'needs' var name is no longer supported. Now Lucky generates a method ending in '?' if the type is 'Bool'." %}
       {% end %}
 
+      # Ensure that the needs variable name has not been previously defined.
+      {% previous_declaration = ASSIGNS.find { |d| d.var == declaration.var } %}
+      {% if previous_declaration %}
+        {% raise <<-ERROR
+          \n
+          Duplicate needs definition: '#{declaration}' defined in #{declaration.filename}:#{declaration.line_number}:#{declaration.column_number}
+          This needs is already defined as '#{previous_declaration}' in #{previous_declaration.filename}:#{previous_declaration.line_number}:#{previous_declaration.column_number}
+          ERROR
+        %}
+      {% end %}
+
       {% if declaration.type.stringify == "Bool" %}
         def {{ declaration.var }}?
           @{{ declaration.var }}