10000 [no-extra-parens] False positive when calling generic function with single argument and type parameter with parentheses · Issue #2314 · typescript-eslint/typescript-eslint · GitHub
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[no-extra-parens] False positive when calling generic function with single argument and type parameter with parentheses #2314

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cherryblossom000 opened this issue Jul 21, 2020 · 1 comment · Fixed by #2319
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[no-extra-parens] False positive when calling generic function with single argument and type parameter with parentheses #2314

cherryblossom000 opened this issue Jul 21, 2020 · 1 comment · Fixed by #2319
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bug Something isn't working package: eslint-plugin Issues related to @typescript-eslint/eslint-plugin

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cherryblossom000 commented Jul 21, 2020 •
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Repro

{
  "rules": {
    "@typescript-eslint/no-extra-parens": 2
  }
}
declare module 'test' {
  class C {}
  export = C
}
declare const f: <T>(x: any) => any

f<import('test')>(1)

Expected Result

No errors because f<import('test')>1 isn't valid syntax.

Actual Result

8:18  error  Unnecessary parentheses around expression  @typescript-eslint/no-extra-parens

Additional Info

This seems to be because of getParentSyntaxParen used in isParentheszied in eslint-utils. Normally, the 1 in f(1) isn't considered to be parenthesised because the ( to the left of 1 is the same the first ( after f. With f<import('test')>(1), the first ( after f is the one used in import('test'), so 1 is reported for being an unnecessarily parenthesised literal.

This function is used in ESLint in isParenthesized -> hasExcessParensWithPrecedence -> checkCallNew.

This could be fixed by reducing the precedence of the argument node.

Versions

package version
@typescript-eslint/eslint-plugin 3.7.0
@typescript-eslint/parser 3.7.0
TypeScript 3.9.7
ESLint 7.5.0
node 12.18.2
npm 6.14.5
@cherryblossom000 cherryblossom000 added package: eslint-plugin Issues related to @typescript-eslint/eslint-plugin triage Waiting for team members to take a look labels Jul 21, 2020
@bradzacher bradzacher added bug Something isn't working and removed triage Waiting for team members to take a look labels Jul 21, 2020
@cherryblossom000
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This also happens for any type parameter containing parentheses:

f<(A | B) & C>(1)

@cherryblossom000 cherryblossom000 changed the title [no-extra-parens] False positive when calling generic function with single argument and import(...) type [no-extra-parens] False positive when calling generic function with single argument and type parameter with parentheses Jul 22, 2020
@cherryblossom000 cherryblossom000 mentioned this issue Jul 22, 2020
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