Lies We Tell Ourselves Using TypeScript v2
summary
A concise demo shows a fetch from the Star Wars API that compiles yet throws at runtime, exposing how TypeScript is intentionally not provably sound. Ten lines of code produce four distinct bugs — bad fetch typings via res.json, unsafe catch handling, function-overload mismatch, and mutation that widens types when appendEntries mutates a list. Fixes use declaration merging, unknown in catch variables, generics and conditional types, which mitigate each failure but introduce their own trade-offs and hazards.
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chapters (13)
- 0:00Introduction
- 0:55Im terribly sorry
- 2:11The code
- 5:03A Tale of Fetch
- 5:56TypeScript at its Boundaries
- 6:36Unsafe Operations
- 9:22Error Handling
- 10:53Unknown to the Rescue
- 11:31Function Overloads
- 17:48Generics
- 19:08Summary
- 20:53More Lies
- 24:59Epilog
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