fix: address doctest regex span and stale eslint-disable in utils/constructor-name example

[Planeshifter]

Failing run: https://github.com/stdlib-js/stdlib/actions/runs/25195861572 (issue #11867, 2026-05-01)

Symptom:

lib/node_modules/@stdlib/utils/constructor-name/examples/index.js
  39:1   error  Displayed return value is `'String'`, but expected `undefined` instead  stdlib/doctest
  151:57 error  Unused eslint-disable directive (no problems were reported from 'no-buffer-constructor')

Root cause:

Error 1 (stdlib/doctest): The rule's RE_ANNOTATION regex uses [^;]*;\n to locate annotated expressions. [^;]* is greedy and matches any non-semicolon character, including newlines. The original noop() body contained only // Do nothing... — no semicolon — so the regex spanned from function noop across the entire function body and the trailing blank line to console.log( constructorName( 'a' ) ); on line 44. The rule then associated // => 'String' with the function identifier, evaluated the combined expression in a VM sandbox, and got undefined (not 'String').

Error 2 (unused eslint-disable-line): The no-buffer-constructor rule is no longer active in the project's ESLint configuration, making the inline directive on line 151 stale.

Fix:

Two minimal edits to lib/node_modules/@stdlib/utils/constructor-name/examples/index.js:

1. Add return; // eslint-disable-line no-useless-return after // Do nothing... in noop(). This inserts a semicolon inside the function body, causing RE_ANNOTATION's [^;]* to stop inside the function instead of spanning across it. The // Do nothing... comment is preserved to match stdlib noop conventions. The no-useless-return disable is required because ESLint flags a bare return; at the end of a void function. The RE_ESLINT_INLINE preprocessor in the stdlib/doctest rule strips eslint-disable-line comments before running RE_ANNOTATION, so the doctest fix is unaffected by the suppression comment.

2. Remove // eslint-disable-line no-buffer-constructor from line 151. The rule is not present in etc/eslint/.eslintrc.js, .eslintrc.examples.js, or .eslintrc.overrides.js, confirming the directive is stale.

Neither change alters the runtime behavior of the example. noop is only consumed by constructorName( noop ) to demonstrate a 'Function' result; its return value is never used.

Validation:

• Reviewed regex trace: with return; in the body (comment stripped by RE_ESLINT_INLINE), [^;]* matches noop() {\n\t// Do nothing...\n\treturn and stops at ;. The following \n} does not match \n//, so the wrong match attempt fails. The regex then correctly matches console.log( constructorName( 'a' ) );\n// => 'String' as intended.
• Confirmed no-buffer-constructor absent from all project ESLint configs; removing the directive will not introduce a new error.
• Coverage: utils/constructor-name 100% (statements, branches, functions, lines).
• Three independent reviewers (two opus, one sonnet) over two cycles: all approved.

Reviewer notes:

• Reviewer C (style) noted that the README (lib/node_modules/@stdlib/utils/constructor-name/README.md) still shows the original // Do nothing...-only noop body. The README is not processed by stdlib/doctest (the rule is disabled for markdown), so this is not a lint issue. Aligning the README is out of scope but could be done as a follow-up.
• Several other // eslint-disable-line no-buffer-constructor directives exist elsewhere in the repo (e.g., buffer/from-buffer, buffer/from-array, assert/is-gzip-buffer). Those are separate packages and out of scope here, but a repo-wide cleanup may be warranted.

Related: issue #11867 (clusters 1 and 2 of that issue — symbol/async-iterator and ndarray/fancy — are addressed separately in draft PR #11882)

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Coverage Report

Package	Statements	Branches	Functions	Lines
utils/constructor-name	$\color{green}126/126$ $\color{green}+100.00%$	$\color{green}12/12$ $\color{green}+100.00%$	$\color{green}1/1$ $\color{green}+100.00%$	$\color{green}126/126$ $\color{green}+100.00%$

The above coverage report was generated for the changes in this PR.

[kgryte]

This PR is a duplicate of another PR. The lint error was already resolved, but we are still in need of a general solution for when the doctest return annotation is matched incorrectly.

[kgryte]

Ref: #11906