fix(preset-env): Include iterator helpers polyfills without shippedProposals

[Copilot]

Iterator helper methods are now part of the ECMAScript 2025 specification and should be included in polyfills by default, without requiring the shippedProposals option to be enabled.

Problem

Previously, code using iterator helpers like x.find() would not include the necessary polyfills unless shippedProposals: true was explicitly set in the preset-env configuration:

// Without shippedProposals: true, this would not include polyfills
x.find(item => item.value > 10);

This behavior was inconsistent with Babel's preset-env, which updated their database to include iterator helpers by default (see babel/babel-polyfills#223).

Solution

Modified the polyfill injection logic in crates/swc_ecma_preset_env/src/corejs3/usage.rs to allow iterator helper modules (esnext.iterator.* and esnext.async-iterator.*) even when shippedProposals is disabled.

The fix adds a special case for iterator helpers:

if !*shipped_proposals && f.starts_with("esnext.") {
    // Iterator helpers are part of ES2025 and should be enabled by default
    if is_iterator_helper(f) {
        // Allow iterator helpers even when shipped_proposals is false
    } else {
        return false;
    }
}

Result

Now iterator helper usage automatically includes the necessary polyfills:

// Input
x.find();

// Output (with automatic polyfill imports)
import "core-js/modules/esnext.async-iterator.find.js";
import "core-js/modules/esnext.iterator.constructor.js";
import "core-js/modules/esnext.iterator.find.js";
x.find();

This works with the standard configuration without requiring shippedProposals: true:

{
  "presets": [
    ["@swc/preset-env", {
      "useBuiltIns": "usage",
      "corejs": "3.45.0",
      "targets": "chrome 80"
    }]
  ]
}

Testing

• Added test case to verify iterator helpers are included without shippedProposals
• Verified existing tests continue to pass with no regressions
• Confirmed behavior matches expected ECMAScript 2025 standard compliance

Fixes #11010

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