Cannot implicitly convert type 'string' to 'char'

'string' does not contain a definition for 'Add' and the best extension method overload 'CompletionSourceExtensions.Add(List<Func<CompletionContext, IEnumerable<CompletionItem>>>, Func<CompletionContext, IEnumerable<string>>)' requires a receiver of type 'System.Collections.Generic.List<System.Func<System.CommandLine.Completions.CompletionContext, System.Collections.Generic.IEnumerable<System.CommandLine.Completions.CompletionItem>>>'

Collection expression type 'string' must have an instance or extension method 'Add' that can be called with a single argument.

'string' does not contain a constructor that takes 0 arguments

'Option<string>' does not contain a definition for 'IsRequired'

Cannot implicitly convert type 'string' to 'char'

Cannot implicitly convert type 'string' to 'char'

'string' does not contain a definition for 'Add' and the best extension method overload 'CompletionSourceExtensions.Add(List<Func<CompletionContext, IEnumerable<CompletionItem>>>, Func<CompletionContext, IEnumerable<string>>)' requires a receiver of type 'System.Collections.Generic.List<System.Func<System.CommandLine.Completions.CompletionContext, System.Collections.Generic.IEnumerable<System.CommandLine.Completions.CompletionItem>>>'

Collection expression type 'string' must have an instance or extension method 'Add' that can be called with a single argument.