microsoft / microsoft/TypeScript
Can't infer unique symbol types via another variable
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Description
Literals such as 0 can be inferred correctly but unique symbols are not.
TypeScript Version: 3.7.x-dev.20191224
Search Terms:
Code
let revision: symbol;
const rev = revision = Symbol();
rev === revision;
Expected behavior:
Type rev is unique symbol.
Actual behavior:
Type rev is symbol. Can't even declare that rev is a unique symbol.
Playground Link: https://www.typescriptlang.org/play/index.html?ts=3.8.0-dev.20191224&ssl=1&ssc=1&pln=3&pc=18#code/DYUwLgBATiBuCWBneB7AdgLgogngWwCMVgBuAKAGN1FIZYIBeaOJVNRiAZXyOAAoAlOTqMGTOq3QkgA
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Research direction
Start by reproducing the example in the linked TypeScript Playground using the reported 3.8.0-dev version, then compare inference for the literal example with inference for the unique-symbol assignment. No source file or test is named in the issue; done means rev is inferred as a unique symbol rather than symbol in the provided code.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- typescript
- Domain
- compilers
- Issue type
- Bug
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Activity status
- Stale
- Clarity
- Clearly specified
- Newbie friendliness
- 35/100