Values from interpolate-hcl can be negative

[akre54]

mapbox-gl-js version: v1.12.0

browser: Node, Chrome

Steps to Trigger Behavior

Create an expression using interpolate-hcl between red and white.

const {expression} = require('mapbox-gl/dist/style-spec')
expression.createExpression(['interpolate-hcl', ['linear'], 2 / 9, 0, 'red', 1, 'white'], {type: 'color'}).value.expression

Sometimes the values are negative. Perhaps this is due to floating point errors? I'm trying to create a map legend with 10 stops, so often the label value is 2/9, 4/9, etc.

Link to Demonstration

https://jsbin.com/boxanun/edit?html,output

Expected Behavior

Returned RGB values should be positive, in the range of 0..1.

Actual Behavior

RGB values can be negative

[akre54]

Assuming relevant: d3/d3-color#39