Anders Hejlsberg

Looks like some pretty dramatic performance overhead.

The general problem we face here is that lots of valid JavaScript code has derived constructors that aren't proper subtypes of their base constructors. In other words, the derived constructors...

This is basically a duplicate of #42384 (which in turn is a duplicate of a much older issue for the same scenario, but I can't locate that right now). You'd...

It's interesting, though... We could consider having a `typeof value.red === "number"` narrow the type of `value` by intersecting with `Record`, and we could do similar narrowing for other types...

Hmm, I'm not sure about this one. The thing that strikes me is the convoluted use of generics in `asLiteral`. It constrains `T` to an array type, when really all...

@andrewbranch The root cause of #50787 is that we consider the apparent type of an unconstrained type parameter to be `{}` in non-strictNullChecks mode. This then gets us in trouble...

This is still a design limitation. For mostly historical reasons we have two fundamentally different kinds of enums in the language, _numeric_ and _literal_. Numeric enums are just like the...

@typescript-bot test this @typescript-bot user test this inline @typescript-bot run dt @typescript-bot perf test faster

@typescript-bot test this @typescript-bot user test this inline @typescript-bot run dt @typescript-bot perf test faster @typescript-bot test top100

This change has surprisingly few effects: Performance, user code test suite, and DT test suite are unaffected. One new error in top100 test suite, correctly identifying an issue in `vscode`....