Originally raised at dart-lang/sdk#43460 by @jensjoha.

"Create missing overrides" when using DAS creates bad code here:

abstract class Foo<E, F> {
  E hello(Foo<E, F> x);
}

class Bar implements Foo<String, String> {
}

The cause is commas in the choices:

[12:44:34 PM] [General] [Info] Calling insertSnippet with:
${1|Foo<String, String>,Object|} ${2:x}

These should be escaped somewhere.