Created a branded type for identifier-escaped strings by weswigham · Pull Request #16915 · microsoft/TypeScript

Then flowed it throughout the compiler, finding and fixing a handful of bugs relating to underscore-prefixed identifiers in the process. Includes a test for two (new) cases noticed - diagnostics from conflicting symbols from export *'s, and enums with underscore prefixed member emit. I mentioned this while talking among the team last week. This can be done in place of/alongside #16868. Additionall

[efcl]

Interanalな`__String`型

[teppeis]

TypeScript 2.5でエスケープ済みのIdentifierを表す__Stringという新しい型が定義され、Symbol.name, Symbol.getName(), Identifier.textなどがstringから__Stringに変更された