API: expose IntrinsicType

<!-- 🚨 STOP 🚨 𝗦𝗧𝗢𝗣 🚨 𝑺𝑻𝑶𝑷 🚨 --> <!-- Half of all issues filed here are duplicates, answered in the FAQ, or not appropriate for the bug tracker. Please help us by doing the following steps before logging an issue: * Search: https://github.com/Microsoft/TypeScript/search?type=Issues * Read the CONTRIBUTING guidelines: https://github.com/Microsoft/TypeScript/blob/master/CONTRIBUTING.md * Read the FAQ: https://github.com/Microsoft/TypeScript/wiki/FAQ --> <!-- If you have a QUESTION: THIS IS NOT A FORUM FOR QUESTIONS. Ask questions at http://stackoverflow.com/questions/tagged/typescript or https://gitter.im/Microsoft/TypeScript --> <!-- If you have a SUGGESTION: Most suggestion reports are duplicates, please search extra hard before logging a new suggestion. See https://github.com/Microsoft/TypeScript-wiki/blob/master/Writing-Good-Design-Proposals.md --> <!-- If you have a BUG: Please fill in the *entire* template below. --> <!-- Please try to reproduce the issue with `typescript@next`. It may have already been fixed. --> **TypeScript Version:** 2.7.2, 2.8.0-dev.20180228 <!-- Search terms you tried before logging this (so others can find this issue more easily) --> **Search Terms:** IntrinsicType There's currently no (official) way to distinguish the literal types `true` and `false`. Although `ts.TypeFlags.BooleanLiteral` is included in `ts.TypeFlags.Literal` it's no `ts.LiteralType`. Therefore I cannot access the value of the literal. I need access to the internal `ts.IntrinsicType` for that. TSLint just declared the type in their project, which might break at any time... My current workaround is `checker.typeToString(type) === 'false'`. If you expose `ts.IntrinsicType`, does it make sense to expose `ts.TypeFlags.Intrisic` too?