feat: add swc_ast_unknown to improve compatibility

[CPunisher]

See https://swc.rs/docs/plugin/ecmascript/compatibility

Summary by CodeRabbit

• Chores
  • Updated build configuration to enhance WebAssembly compilation support with specialized compiler settings.

_{✏️ Tip: You can customize this high-level summary in your review settings.}

[coderabbitai]

Walkthrough

A wasm32-specific configuration section is added to Cargo's config file, setting a compile-time cfg flag (swc_ast_unknown) when targeting WebAssembly 32-bit architecture.

Changes

Cohort / File(s)	Summary
Build configuration .cargo/config.toml	Added target-specific section for wasm32 architecture with rustflags set to --cfg=swc_ast_unknown

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~2 minutes

• Configuration-only change with no logic modifications
• Single isolated file addition
• Straightforward build flag setup

Poem

🐰 A whisker-twitch, a cfg so bright,
For wasm32, a compile-time light,
In Cargo's nest, a config gleams,
Where little flags fulfill our dreams!
~✨

Pre-merge checks and finishing touches

✅ Passed checks (3 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title 'feat: add swc_ast_unknown to improve compatibility' accurately describes the main change: adding a compile-time cfg flag to the Cargo configuration for wasm32 compatibility.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

✨ Finishing touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment

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📜 Recent review details

Configuration used: CodeRabbit UI

Review profile: CHILL

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between 0bcbf6b and 44b8e75.

📒 Files selected for processing (1)

• .cargo/config.toml (1 hunks)

🔇 Additional comments (1)

.cargo/config.toml (1)

6-7: Target-specific wasm32 configuration looks good.

The swc_ast_unknown flag is a legitimate SWC ecosystem flag used to guard backward compatibility code in encoding-related paths. Setting this via rustflags for wasm32 targets is the correct approach for handling cross-compilation configuration.

Please verify that:

1. The project's source code actually uses #[cfg(swc_ast_unknown)] conditions to conditionally compile code paths that require this flag.
2. This flag is necessary for the current version of swc_core specified in Cargo.toml.

If this change is motivated by a specific compatibility issue with a newer swc_core version, consider documenting that context (e.g., in a comment or commit message) for future maintainers.

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[Codex-]

Awesome, thank you!