fix reserved words

[cometkim]

The compiler prefixes conflicting ident names with $$ to prevent the output from containing a SyntaxError or unintentionally declarying conflicting names.

However, some of the managed keywords are outdated (keywords listed on the Future reserved words in older standards section), some are not actually keywords, and the list of Chrome global variables is far too extensive.

Changes

• Clarify actual JavaScript's keywords and other reserved words
• Includes only the JavaScript standard builtins. classnames from Chrome are no longer prefixed
• Refactor the keywords scripts and manage a single regular OCaml module.
• Use OCaml Hashtbl instead of binary search (keywords are small enough)

Future works

If a name is not an actual JS keyword, there should be no problem defining the identifier with the name inside the module scope, even if it is used in the globalThis scope. But the SyntaxError only occurs in the CommonJS system.

IMHO we need a way to allow using those names if users want. In a previous PR I proposed a syntax using exotic ident.

// "require" is a reserved word

let require = ""
// This will be `$$require` in the output

let \"require" = ""
// This will be `require` in the output

However, this cannot be implemented in the current parser. If necessary, the scanner would have to be modified to keep exotic tokens, which would significantly increase the complexity of printers.

[cometkim]

But the SyntaxError only occurs in the CommonJS system.

I just modified the test and now they only throw a SyntaxError for names that are directly related to CommonJS module system.

• module
• exprots
• require
• __dirname
• __filename

Others should be fine to allow.

[cometkim]

I removed the codegen script at b1275cb since now we can manage keywords manually.

I ran the syntax benchmark and there were no noticeable perf changes by using OCaml Set instead of binary search.

[cometkim]

I noticed that it isn't BST. Also, it is a list that can never be changed, it does not benefit from using an immutable tree. I replaced it with a Hashtbl to optimize lookups.

[cknitt]

LGTM! Thanks a lot!