Re-enable error recovery for contextual keywords used as identifiers

[thorn0]

yield = 3

causes an error: Unexpected reserved word 'yield' (playground), which should only happen in modules. In non-module code, yield is an acceptable identifier (spec). Prettier 2.2.1 handles this better thanks to the error recovery (playground).

Originally posted by @thorn0 in #10446 (comment)

[fisker]

var let = 3

Should not be error too.

[thorn0]

Turns out Prettier simply shouldn't rethrow Unexpected reserved word errors. See babel/babel#13033 (comment)
For the keywords like for, var, etc., the error message is different (Unexpected keyword).

[satya-nutella]

@thorn0 I would like to contribute to this if possible, I am a first time contributor here. Any directions on this would be awesome

[thorn0]

@meehawk Sorry, but I'm afraid this has been fixed by #10802.

Prettier 2.3.0
Playground link

--parser babel

Input:

yield = 3
var let = 3

Output:

yield = 3;
var let = 3;

[thorn0]

On the other hand, tests for this weren't added, so let's reopen the issue.

@meehawk Would you like to contribute tests?

[satya-nutella]

@thorn0 sure that sounds like an amazing place to start though I am not that experienced when it comes to testing. Do you have any pointers on how could I get started?

[thorn0]

https://github.com/prettier/prettier/blob/main/CONTRIBUTING.md#tests

[MohananT]

Can I start the tests for this fix? @thorn0