Add support Class field declarations

[DrawAChicken]

This is required because Acorn uses acorn-class-fields.

[DrawAChicken]

What is wrong with CL

[ajvincent]

Looking at the build logs versus https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Classes#browser_compatibility, the bug is obvious. Classes field support started in Node 12, but the .travis.yml file mandates testing against Node 6, 8, and 10.

[palant]

Looking at the build logs versus https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Classes#browser_compatibility, the bug is obvious. Classes field support started in Node 12, but the .travis.yml file mandates testing against Node 6, 8, and 10.

No, the Node version is irrelevant here. The parser used is acorn, and the issue is that test/compare-acorn-es2019/ directory is being processed without the acorn-class-fields plugin. Here:

escodegen/test/compare-acorn-es2019.js

Lines 39 to 45 in 7a48a21

	options = {
	ranges: true,
	locations: false,
	ecmaVersion: 10
	};
	tree = acorn.parse(code, options);

And here:

escodegen/test/compare-acorn-es2019.js

Lines 58 to 64 in 7a48a21

	options = {
	ranges: true,
	locations: false,
	ecmaVersion: 10
	};
	tree = acorn.parse(code, options);

[kevincox]

I added a PR that supersedes this with more tests that pass: #465