Parsing Octal Literals and Escapes

#51837

// allowed outside of strict mode
function loose() {
    // numeric octal
    console.log(0170);

    // octal string escapes
    console.log("\170");
    console.log("\0170");
}

// errors in strict mode
function strict() {
    "use strict";

    // numeric octal
    "use strict"; console.log(0170);

    // octal string escape
    "use strict"; console.log("\170");
    "use strict"; console.log("\0170");
}

function errorsAlways() {
    // octal template string escapes
    console.log(`\170`);
    console.log(`\0170`);
}

// valid ALWAYS
function validAlways() {
    // explicit octal
    console.log(0o170);

    // not even an octal string escape sequence
    console.log("\0o170");

    // Tagged Template Strings
    console.log(String.raw `\170`);
    console.log(String.raw `\0170`);
}

4.9 Playground
PR Build

• In JS, octal numeric literals have a leading zero
  • It is an error to use this in strict mode
• Octals also exist in string escape sequences
  • Don't need a leading zero(!)
  • It is an error to use this in strict mode
• Octals also exist in template strings
  • It is an error to use this in any mode
• You may write 0o170 in any mode
• "\0o170" is not a string escape sequence, though.
• You may write String.raw`\170` and get the string "slash one seven zero"
• TS currently fails to error on \170 in strict mode.
• This PR fixes this, but also treats octals in sloppy-mode is if they were in strict mode.
• Does anyone want to stand up for sloppy mode?
  • No.
• Think this is technically Annex B, so we can claim your engine technically might not support this.
• Steelman case: Someone using TS for JS-only tooling purposes?
  • Probably rare, and parse errors can be ignored.
• Saves some performance.
• Conclusion: Ship it!

Testing Node 12.20

#53194

• Made it so 5.0 says Node 12 is a minimum (even though we work on lower than that right now).
• But Node 12 is old.
  • Should we have set our minimum to higher?
  • Feels like it's a bit too late for that.
• Our infra can't use stuff like ?? and ?. if we have to test on Node 12.
• Also, stable sort is only mandated in ES2019 (so questionable if Node 12 can "guarantee" that even if it always has)
• Could we say "TypeScript 5.x will always support Node 12?"
  • That's going to be 2.5 years! Node 12 doesn't even get security updates anymore, does it?
  • Node 12 goes out of maintenance in April.
  • TypeScript 5.1 goes out just after that - doesn't make sense to support.
• Conclusion: should say Node 14 is what's supported in 5.1, so don't add a test runner we'd have to rip out immediately.