fn parse_union_type_definition(&mut self) -> ParseResult<UnionTypeDefinition> {
        self.parse_keyword("union")?;
        let name = self.parse_identifier()?;
        let directives = self.parse_constant_directives()?;
        let members = self.parse_union_member_types()?;
        Ok(UnionTypeDefinition {
            name,
            directives,
            members,
        })
    }
/**
     * UnionTypeDefinition :
     *   - Description? union Name Directives? UnionMemberTypes?
     */
UnionTypeDefinition :
- Description. union Name Directives.
UnionTypeDefinition : - Description . union Name Directives .
fn parse_union_type_definition(&mut self) -> ParseResult<UnionTypeDefinition> {
        self.parse_keyword("union")?;
        let name = self.parse_identifier()?;
        let directives = self.parse_constant_directives()?;
        let members = self.parse_union_member_types()?;
        Ok(UnionTypeDefinition {
            name,
            directives,
            members,
        })
    }
fn parse_union_type_definition ( & mut self ) -> ParseResult < UnionTypeDefinition > { self . parse_keyword ( " " ) ? ; let name = self . parse_identifier ( ) ? ; let directives = self . parse_constant_directives ( ) ? ; let members = self . parse_union_member_types ( ) ? ; Ok ( UnionTypeDefinition { name , directives , members , } ) }
UnionTypeDefinition :
   - Description?
UnionTypeDefinition : - Description?
&mut self
&mut self