fix: widen mutable property literal types

[harshmathurx]

Fixes #11174.

This widens primitive literal initializers for mutable object/class properties, so noUnnecessaryConditions does not treat checks like guard.current after { current: false } as permanently falsy.

Added regression coverage for object and class properties.

@ematipico this follows up on the confirmed issue.

AI assistance disclosure: I used AI assistance to inspect the relevant inference path and draft the patch; I reviewed the changes and ran the focused checks locally.

[changeset-bot]

🦋 Changeset detected

Latest commit: e38cd48

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 13 packages

Name	Type
@biomejs/biome	Patch
@biomejs/cli-win32-x64	Patch
@biomejs/cli-win32-arm64	Patch
@biomejs/cli-darwin-x64	Patch
@biomejs/cli-darwin-arm64	Patch
@biomejs/cli-linux-x64	Patch
@biomejs/cli-linux-arm64	Patch
@biomejs/cli-linux-x64-musl	Patch
@biomejs/cli-linux-arm64-musl	Patch
@biomejs/wasm-web	Patch
@biomejs/wasm-bundler	Patch
@biomejs/wasm-nodejs	Patch
@biomejs/backend-jsonrpc	Patch

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[coderabbitai]

Walkthrough

Property initialisers now widen literal bigint, boolean, number, string, and template values to their primitive types. Object and regular-expression literals retain literal types. Class and object property inference uses this widening. Valid cases cover mutable object properties and private class fields. A patch changeset documents the noUnnecessaryConditions correction.

Possibly related PRs

• biomejs/biome#10108: Both PRs modify noUnnecessaryConditions behaviour and its tests.
• biomejs/biome#11138: Both PRs modify JavaScript property type inference in local_inference.rs.

Suggested labels: A-Linter, L-JavaScript, A-Type-Inference

Suggested reviewers: ematipico, dyc3

🚥 Pre-merge checks | ✅ 4

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly summarises the main change: widening mutable property literal types.
Description check	✅ Passed	The description directly explains the fix, affected rule, regression coverage, and linked issue.
Linked Issues check	✅ Passed	The changes widen primitive literals for mutable object and class properties and add regression tests, matching issue #11174.
Out of Scope Changes check	✅ Passed	The changes are limited to type widening, targeted regression tests, and the related changeset.

✨ Finishing Touches

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[coderabbitai]

🧹 Nitpick comments (1)

crates/biome_js_type_info/src/local_inference.rs (1)

1904-1930: 📐 Maintainability & Code Quality | 🔵 Trivial | ⚡ Quick win

Add rustdoc for the widening contract.

Document both helpers with /// comments. State which primitive literal types widen, and why object and regular-expression literals remain literal types.

As per coding guidelines, use rustdoc for new rule changes and document contracts for future contributors.

🤖 Prompt for AI Agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@crates/biome_js_type_info/src/local_inference.rs` around lines 1904 - 1930,
Add rustdoc comments to reference_to_widened_property_value and
widen_property_value_type_data describing that bigint, boolean, number, string,
and template literals widen to their primitive types, while object and
regular-expression literals remain literal types to preserve their structural or
identity-specific information.

Source: Coding guidelines

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Nitpick comments:
In `@crates/biome_js_type_info/src/local_inference.rs`:
- Around line 1904-1930: Add rustdoc comments to
reference_to_widened_property_value and widen_property_value_type_data
describing that bigint, boolean, number, string, and template literals widen to
their primitive types, while object and regular-expression literals remain
literal types to preserve their structural or identity-specific information.

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ℹ️ Review info

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Run ID: c060588d-fa3b-4da9-a0f3-9cc243559eb5

📥 Commits

Reviewing files that changed from the base of the PR and between db36fb4 and e38cd48.

⛔ Files ignored due to path filters (1)

• crates/biome_js_analyze/tests/specs/suspicious/noUnnecessaryConditions/valid.ts.snap is excluded by !**/*.snap and included by **

📒 Files selected for processing (3)

• .changeset/witty-badgers-widen.md
• crates/biome_js_analyze/tests/specs/suspicious/noUnnecessaryConditions/valid.ts
• crates/biome_js_type_info/src/local_inference.rs

[codspeed-hq]

Merging this PR will degrade performance by 14.63%

❌ 1 regressed benchmark
✅ 61 untouched benchmarks
⏩ 237 skipped benchmarks¹

Warning

Please fix the performance issues or acknowledge them on CodSpeed.

Performance Changes

	Benchmark	BASE	HEAD	Efficiency
❌	js_analyzer[index_3894593175024091846.js]	73.9 ms	86.5 ms	-14.63%

Tip

Investigate this regression by commenting @codspeedbot fix this regression on this PR, or directly use the CodSpeed MCP with your agent.

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_{Comparing harshmathurx:fix/no-unnecessary-conditions-mutable-property (e38cd48) with main (f34e15c)²}

Footnotes

1. 237 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

2. No successful run was found on main (db36fb4) during the generation of this report, so f34e15c was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩