fix(typescript-estree): support override modifier for parameter property

[sosukesuzuki]

ref: prettier/prettier#11017

Support TS 4.3 override modifier for parameter properties.

TS Playground Link

[typescript-eslint]

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[sosukesuzuki]

babel/parser cannot parse override modifier for parameter properties, I'll report and fix it.

[sosukesuzuki]

babel/babel#13427

[codecov]

Codecov Report

Merging #3485 (90bd914) into master (44452dd) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master    #3485   +/-   ##
=======================================
  Coverage   92.63%   92.63%           
=======================================
  Files         325      325           
  Lines       11226    11227    +1     
  Branches     3163     3164    +1     
=======================================
+ Hits        10399    10400    +1     
  Misses        367      367           
  Partials      460      460           

Flag	Coverage Δ
unittest	92.63% <100.00%> (+<0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
packages/typescript-estree/src/convert.ts	98.27% <100.00%> (+<0.01%)	⬆️

[bradzacher]

I'm not sure about this. It currently is an explicit TS error, so I think that babel has it right.

This should probably be a syntax error, and something we shouldn't support explicitly.

I think this is another case where prettier could access the underlying TS ast to look for the existence of a bad modifier (until such time that we have support for syntax errors?)

[sosukesuzuki]

For example, in this case the override modifier of the parameter property is required. TypeScript Playground Link(The noImplicitOverride option is not set to true in this link, please set it to true manually.)
Also in TypeScript complier, override modifier for parameter property is allowed explicitly. (ref: microsoft/TypeScript#43831)

[bradzacher]

OH! I see.
microsoft/TypeScript#43831 was released as part of the RC.

When I built the feature, I used the playground to figure out what was supported.
The playground doesn't ever use the RC version, so I was working against 4.3-beta.
So when I tested the parameter property case, it was a TS error.

But that PR obviously makes it supported - and testing against 4.3.2 it does work without an error.
This is correct then.

[bradzacher]

LGTM - one suggestion:
could you please add a test for this case with JUST the override as this emits as a parameter property:

class SpecializedComponent extends SomeComponent {
  constructor(override param: string) {
      super();
  }
}

repl

[bradzacher]

thanks for this!