Bug: no-invalid-this: false positive with this in class field

Environment

Node version: v16.13.1 npm version: 8.3.0 Local ESLint version: 8.6.0 Global ESLint version: N/A Operating System: Ubuntu 20.04.2 LTS

What parser are you using?

Default (Espree)

What did you do?

Configuration

{
    "parserOptions": {
        "ecmaVersion": "latest",
        "sourceType": "module"
    },
    "rules": {
        "no-invalid-this": 2
    }
}

class Foo {
    bar = this;
}

What did you expect to happen?

No error reported.

What actually happened?

$ npx eslint index.js 

/home/regseb/testcase/index.js
  2:11  error  Unexpected 'this'  no-invalid-this

✖ 1 problem (1 error, 0 warnings)

Participation

• I am willing to submit a pull request for this issue.

Additional comments

No error reported with this configuration (without "sourceType": "module"):

{
    "parserOptions": {
        "ecmaVersion": "latest"
    },
    "rules": {
        "no-invalid-this": 2
    }
}

[mdjermanovic]

To clarify, this rule only flags any use of this where the value of this is undefined (for example, at the top level of modules), which isn’t the case in the provided example. If this is an object, the rule doesn’t make assumptions about whether a particular usage makes sense or not.

This bug is reproducible in v8.0.0 as well. It happens only when PropertyDefinition#value is ThisExpression. Due to a higher specificity of "PropertyDefinition > *.value", ThisExpression gets called first and is therefore mistakenly treated as if it were in an outer context.

I’ll work on the fix.

[ljharb]

ah, i misunderstood the purpose of the rule then.