he/him 
After using TypeScript there's some features that I'm terrified of that seem counter intuitive. All the following examples produce NO errors and are with every single strict TS option enabled.
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I use type predicates about as much as type casting: rarely. They’re both powerful yet unsafe. Occasionally you need to tell TS that you know better than the type system.
I have 12 uses of type predicates and 81 uses of "type casting". They would be even more powerful if they were safe.
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If your 12 uses of type predicates is similar to your example of a string primitive, it’s actually safer to move the typeof inline as a type guard. The predicates are only useful for nested objects. It would be great if they were safe and forced an explicit cast to be unsafe.
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Here's a few instances of my usages of type predicates. It's not really an option to inline all of these, especially `isStatement`. They're essential for refinements of very large unions.pic.twitter.com/XC2FWCZls0
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'as' is an escape hatch much like 'any'—“don’t bother me, just let me write this.” It lets you cast up or down, just not to an unrelated type. It can almost always be avoided. 1/2
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If you just want a “safe” cast (well, safe if we naively assume mutable properties are covariantly typed), you can declare a new variable: let a: string; let b: string | number = a;
let c: "foo" = a; 
c is an unsafe downcast and is caught as such
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