feat(eslint-plugin): [no-shadow] exclude external type declaration merging

[idan-at]

Lately (not sure exactly which version), this snippet started failing no the no-shadow rule:

import type { Foo } from 'bar';
declare module 'bar' {
  export interface Foo {
    x: string;
  }

It shouldn't fail, since this is the way to extend external types in typescript (there's no re-declaration here)

This PR fixes it.

[typescript-eslint]

Thanks for the PR, @idan-at!

typescript-eslint is a 100% community driven project, and we are incredibly grateful that you are contributing to that community.

The core maintainers work on this in their personal time, so please understand that it may not be possible for them to review your work immediately.

Thanks again!

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[nx-cloud]

Nx Cloud Report

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	Node 12.x - nx test @typescript-eslint/parser
	Node 12.x - nx test @typescript-eslint/eslint-plugin-internal
	Node 12.x - nx test @typescript-eslint/experimental-utils
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	Node 12.x - nx test @typescript-eslint/scope-manager
	Node 12.x - nx test @typescript-eslint/eslint-plugin
	Node 12.x - nx test @typescript-eslint/visitor-keys
	Node 12.x - nx test @typescript-eslint/parser
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	Node 12.x - nx test @typescript-eslint/experimental-utils
	Node 12.x - nx run-many --target=build --all --parallel
	Node 12.x - nx test @typescript-eslint/scope-manager
	Node 12.x - nx test @typescript-eslint/visitor-keys
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[codecov]

Codecov Report

Merging #3959 (a57c4a0) into master (7842090) will increase coverage by 0.26%.
The diff coverage is 90.00%.

❗ Current head a57c4a0 differs from pull request most recent head b85322f. Consider uploading reports for the commit b85322f to get more accurate results

@@            Coverage Diff             @@
##           master    #3959      +/-   ##
==========================================
+ Coverage   93.12%   93.39%   +0.26%     
==========================================
  Files         277      151     -126     
  Lines        9781     8103    -1678     
  Branches     2851     2572     -279     
==========================================
- Hits         9109     7568    -1541     
+ Misses        244      181      -63     
+ Partials      428      354      -74     

Flag	Coverage Δ
unittest	93.39% <90.00%> (+0.26%)	⬆️

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

Impacted Files	Coverage Δ
packages/eslint-plugin/src/rules/no-shadow.ts	76.51% <90.00%> (+1.10%)	⬆️
packages/scope-manager/src/referencer/Reference.ts
packages/scope-manager/src/lib/es2019.string.ts
.../scope-manager/src/variable/ImplicitLibVariable.ts
packages/scope-manager/src/scope/CatchScope.ts
packages/scope-manager/src/lib/esnext.intl.ts
packages/scope-manager/src/lib/es2021.ts
...ckages/scope-manager/src/referencer/VisitorBase.ts
...e-manager/src/scope/FunctionExpressionNameScope.ts
packages/scope-manager/src/lib/esnext.symbol.ts
... and 117 more

[JoshuaKGoldberg]

Looks great, thanks! Just requesting changes on the dead-ish code: either getting rid of it or adding a test case to exercise it.

[bradzacher]

perfect - thanks for thsi!

nice work making it so strict - this is amazing!