Repository navigation
Typecast string to string literal #12879
Description
Activity
Also, the non templated version the function works as intended
function type(val: any){ return <'this is string literal'>val; } // stringLiteral appears as ' let stringLiteral: "this is string literal" ' let stringLiteral = type('this is string literal');In 2.1 we preserve literal types of expressions and variables for a long as possible, but when we infer a literal type for a mutable location such as a
letorvarvariable, we widen to the base primitive type. However, if you declareiShouldBeStringLiteralusingconstyou shouldn't need thetypefunction at all.For more details see #10676.
Thank you very much. Problem solved
- locked and limited conversation to collaborators
on Jun 19, 2018
TypeScript Version: 2.1.4
Code
Expected behavior:
Before updating to typescript 2.1.4 the function transformed string to string literals with the same value
Actual behavior:
Now, even though the function returns a string literal type, assigning the return value to a variable / object property, will downcast it to string
In the second image, I would expect
xto be of type'String literal'This is especially in redux like scenarions, where you have to switch based on a constant and need the exhaustive checking in order to get type safety inside every case branch
edit: I know the solution is a bit hackish, but it helps a lot. If there is any other way of doing this, I'm more than open to suggestions