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type.isLiteral() returns false for boolean literals

See original GitHub issue

TypeScript Version: 3.1.0-dev.20180728 (new in 3.0.1)

Search Terms: isLiteral()

Code

Create a boolean literal in the compiler api.
Call isLiteral() on it.

Change seems to be done here:

https://github.com/Microsoft/TypeScript/commit/e46d214fceb72cc76145779543bf871ce9ff66b0#diff-233e1126c0abc811c4098757f9e4516eR428

Expected behavior: true for a boolean literal type (true or false)

Actual behavior: false

I have a few tests for assumptions about the compiler api in ts-simple-ast and this one started failing. Maybe it’s not a bug, but I thought I would log it anyway to find out why this behaviour changed.

Is it because it doesn’t have the Unit flag while string and number literals do? For what it’s worth, in checker.ts it will internally return true for boolean literals in isLiteralType.

Issue Analytics

State:
Created 5 years ago
Reactions:2
Comments:7 (6 by maintainers)

Top GitHub Comments

1reaction

marijnhcommented, Jul 8, 2019

I just ran into this too (needing to use undocumented internals to get at the value of a boolean literal type). So to second @Kingwl 's question—is the intent to add a BooleanLiteralType interface to the public API? Anything someone undertaking such a change should be careful about?

1reaction

ajafffcommented, Jul 31, 2018

That said, as an API user it does seem a bit unexpected that boolean literal types aren’t included with LiteralType, but I don’t have a use case where it would matter.

I need it quite often and it’s annoying, see #22269

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