Left arrow ligature in JavaScript + Flow #113

SergioMorchon · 2019-09-24T11:00:44Z

Environment

Cascadia Code version number: 1909.16
Application (with version) used to display text: Visual Studio Code 1.38.1
OS platform and version: Windows 10 Pro, 18362
Screen resolution (i.e. 220dpi): 1920x1080 @ 100%

Any other software? No

Steps to reproduce

Open a JavaSript file that will be used with Flow (https://flow.org/).
Open the following flow file: react-redux.
You'll see declare type MapStateToProps<-S, -OP, +SP> =

Expected behavior

Don't apply a ligature in that case. It should keep as <-, because < is used to declare a generic, and - for write-only (see https://flow.org/en/docs/types/interfaces/#interface-property-variance-read-only-and-write-only-).

Actual behavior

That <-S is changed by a left arrow.

ExE-Boss · 2019-09-24T13:54:57Z

Same with TypeScript (and other programming languages with generics):

let foo: Bar<-3>;

aaronbell · 2019-09-24T15:49:34Z

It sounds like this is not something that can be special cased out in the font code (as in, ignore ligature when X occurs). That said, I can provide a stylistic set that turns off that specific ligature generally that would need to be accessible via font settings.

ExE-Boss · 2019-09-24T16:35:41Z

Another option would be to improve the TextMate language grammar so that, - followed by a number has a different TextMate scope from the enclosing generics. Same with Flow’s read‑only and write‑only modifiers (+ and -).

This will fix it in VS Code, but not on GitHub:

bterlson · 2019-09-25T19:25:32Z

FWIW, I think flow is uniquely impacted by this given its variance sigils for generic parameters. TypeScript is impacted, but I suspect only in very niche cases where users are passing a negative number literal type. I think C# generic syntax doesn't allow <-.

microsoft / cascadia-code

Left arrow ligature in JavaScript + Flow #113

Left arrow ligature in JavaScript + Flow #113

SergioMorchon commented Sep 24, 2019 •

edited

ExE-Boss commented Sep 24, 2019 •

edited

aaronbell commented Sep 24, 2019

ExE-Boss commented Sep 24, 2019 •

edited

bterlson commented Sep 25, 2019 •

edited

microsoft / cascadia-code

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Left arrow ligature in JavaScript + Flow #113

Left arrow ligature in JavaScript + Flow #113

Comments

SergioMorchon commented Sep 24, 2019 • edited

Environment

Steps to reproduce

Expected behavior

Actual behavior

ExE-Boss commented Sep 24, 2019 • edited

aaronbell commented Sep 24, 2019

ExE-Boss commented Sep 24, 2019 • edited

bterlson commented Sep 25, 2019 • edited

SergioMorchon commented Sep 24, 2019 •

edited

ExE-Boss commented Sep 24, 2019 •

edited

ExE-Boss commented Sep 24, 2019 •

edited

bterlson commented Sep 25, 2019 •

edited