We need a name for the option described in #13778

The exact behavior that this flag would enable is, briefly:

• Read expressions of the form expr[i] will now be T | undefined where T is the index signature type
• Read expressions of the form expr.prop will now be T | undefined where T is the index signature type if an index signature on expr exists but not a declared property named prop
• string and number index signatures are both subjected to this treatment
• Write expressions expr[i] = v and expr.prop = v are unaffected
• Type expressions TypeName[number] and TypeName["prop"] are unaffected

Good candidate flag names should follow these rules and goals:

• Do not start with strict since this flag would not get turned on by the global --strict setting
• Follow an existing convention (see the list at (https://aka.ms/tsconfig.json)
• Convey the intent of the flag along with its behavior, somehow
• Avoid problematic terms (e.g. do not reference mental illnesses)

This is an open-ended approval voting issue. Rules:

• Use 👍 reaction on as many as you like
  • Top-upvoted options will be given the most consideration
  • This is an advisory vote; final say is still up to the TypeScript team
• You may propose new options; comments must be of exactly the form `–proposedOptionName`
  • Follow the above guidance - no --strictFoo!
• No discussion here; discuss in #13778. Non-option comments will be deleted
• Sharing this link on social media is encouraged!

I will seed this with some of the names suggested at our last meeting. We may also cull options that aren’t receiving a lot of votes to help keep the comment count manageable.