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sebmck's profile
Sebastian
Sebastian
Sebastian
Verified account
@sebmck

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SebastianVerified account

@sebmck

JavaScript boy and “lovely thoughtleader” ⌨️ he/him ♂️

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Joined April 2011

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    1. Sebastian‏Verified account @sebmck 22 Jun 2019
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      • Report NetzDG Violation

      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.

      10 replies 6 retweets 92 likes
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    2. Sebastian‏Verified account @sebmck 22 Jun 2019
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      Type predicates are just an annotation and aren't actually checked. Meaning you can do some pretty wacky and unsafe things. Is there an technical constraint preventing TS from checking these?pic.twitter.com/qtIIzM1Cat

      9 replies 1 retweet 17 likes
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    3. Steven‏ @styfle 22 Jun 2019
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      Replying to @sebmck

      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.

      1 reply 0 retweets 2 likes
    4. Sebastian‏Verified account @sebmck 22 Jun 2019
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      Replying to @styfle

      I have 12 uses of type predicates and 81 uses of "type casting". They would be even more powerful if they were safe.

      2 replies 0 retweets 1 like
    5. Steven‏ @styfle 22 Jun 2019
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      Replying to @sebmck

      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.

      2 replies 0 retweets 1 like
    6. Steven‏ @styfle 22 Jun 2019
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      Replying to @styfle @sebmck

      Maybe this is because “unknown” came out after type predicates so the purpose was originally to pass in “any” and get back a type. But with “unknown”, that’s kinda a better way to runtime check the type. Cc @drosenwasser @SeaRyanC

      1 reply 0 retweets 1 like
      Sebastian‏Verified account @sebmck 22 Jun 2019
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      Replying to @styfle @drosenwasser @SeaRyanC

      unknown refinements are even more finnicky though. Type predicates are useful to abstract out refinement logic.

      7:56 PM - 22 Jun 2019
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      • Sibelius Seraphini
      0 replies 0 retweets 1 like

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