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[no-unsafe-member-access] Extending namespaces trigger error #2740

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susnux opened this issue Nov 5, 2020 · 1 comment · Fixed by #2753
Closed
3 tasks done

[no-unsafe-member-access] Extending namespaces trigger error #2740

susnux opened this issue Nov 5, 2020 · 1 comment · Fixed by #2753
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bug Something isn't working good first issue Good for newcomers package: eslint-plugin Issues related to @typescript-eslint/eslint-plugin

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@susnux
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susnux commented Nov 5, 2020

  • I have tried restarting my IDE and the issue persists.
  • I have updated to the latest version of the packages.
  • I have read the FAQ and my problem is not listed.

Repro

declare namespace FG {
	interface A {}
}

interface B extends FG.A {
}

You can also look at this example repo: https://github.com/susnux/typescript-eslint-no-unsafe-member-access

Expected Result
No error message

Actual Result

typescript-eslint-no-unsafe-member-access/src/test.d.ts
6:21 error Unsafe member access .A on an any value @typescript-eslint/no-unsafe-member-access

Additional Info
Nothing special, you can simply reproduce this.
I experienced the same issue (this) as reported by @tao-cumplido in #1868.

Versions

package version
@typescript-eslint/eslint-plugin 2.27.0
@typescript-eslint/parser `2.27.0
@typescript-eslint/typescript-estree 2.27.0
@typescript-eslint/experimental-utils 2.27.0
TypeScript 4.0.5
node 12.18.4
npm 6.14.6
@bradzacher bradzacher added bug Something isn't working good first issue Good for newcomers package: eslint-plugin Issues related to @typescript-eslint/eslint-plugin labels Nov 6, 2020
@bradzacher
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The root of this problem is that for TSInterfaceHeritage we emit a MemberExpression for the heritage.

class B extends FG.A {} // FG.A is a MemberExpression ✅
type B = FG.A; // FG.A is a TSQualifiedName ✅

class B implements FG.A {} // FG.A is a MemberExpression ❌
interface B extends FG.A {} // FG.A is a MemberExpression ❌

https://astexplorer.net/#/gist/4d80b0e52f9c5a85c3e8e5965159c0b0/f19196f6c60b81e792172e7c0adcfc8f676270d0

However - this is a type-only location, so ideally it should be a TSQualifiedName.

Why do we emit a MemberExpression?

Because TS emits a PropertyAccessExpression here - and our parser (mostly) just converts TS's AST as written.

Why does TS emit this?

Because the TS parser shares the logic for parsing this between:

  • class extends
  • interface extends
  • class implements

TS has a semantic error to prevent you from doing anything too stupid - however it does allow some stupid code: microsoft/TypeScript#41420

What's the fix?

Pretty straight-forward - the selectors need to be updated to ignore any MemberExpression whose parent is either TSInterfaceHeritage or TSClassImplements.

typescript-eslint/packages/eslint-plugin/src/rules/no-unsafe-member-access.ts

Lines 74 to 75 in e82698c

MemberExpression: checkMemberExpression,
'MemberExpression[computed = true] > *.property'(

@hsmitty93 hsmitty93 mentioned this issue Nov 11, 2020
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bug Something isn't working good first issue Good for newcomers package: eslint-plugin Issues related to @typescript-eslint/eslint-plugin
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@susnux @bradzacher