fix #11480, disallow delete operator on readonly property or index signature

[HerringtonDarkholme]

Fixes #11480

It changed more tests than I thought. Should we check delete operator only if it is a property access or indexer?

[RyanCavanaugh]

Looks good to me. Pretty stupid that we allowed delete x; before

[HerringtonDarkholme]

Sorry, I didn't catch your point.

Do you mean "check readonly property only when delete property access or indexer" is good or "disallow delete anything other than property access or indexer"?

For the latter, I think it would break namespace.

namespace A {
  export var a = 123;
  delete a;
}

And it would break unintentional code like

// in other file like html
window.globalProperty = 123
// in ts
declare var globalProperty
delete globalPropery

[RyanCavanaugh]

I believe both of those should be errors for the sake of clarity (unless there are some compelling use cases from real code to bring up).

In the namespace case, it would be very confusing because the behavior would have to change (to become an error) depending on whether you wrote export (since non-exported vars don't become properties). Writing delete A.a is much clearer.

In the global case, we often require globals to be prefixed by window. anyway, which seems like the correct thing to do here as well. And since we'd have to resolve this differently in modules vs non-modules anyway, it's also confusing in that regard.

[HerringtonDarkholme]

@ahejlsberg I found resolvedIndexInfo is removed in #11929 . Is it intended?
I need indexInfo in checkDeleteExpression, otherwise I need to handle delete in getPropertyTypeForIndexType

[mhegazy]

@HerringtonDarkholme can you refresh the PR.

[HerringtonDarkholme]

@dotnet-bot test ci please

Hmmm, it seems node.6 CI breaks due to mismatched shasum check.

[mhegazy]

@dotnet-bot test ci please