feat(minifier): remove unused import source/defer statements

[camc314]

fixes #16893
fixes #16894

[camc314]

• feat(minifier): remove unused import source/defer statements #17085 👈 (View in Graphite)
• main

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[Copilot]

Pull request overview

This PR extends the minifier's unused declaration removal functionality to handle import source and import defer statements, which are newer import phase proposals. When these imports are determined to be unused, they are completely removed (converted to empty statements) rather than converted to side-effect imports, since phase imports have specific semantics.

Key Changes

• Added logic to detect and remove unused import source/defer statements when the imported binding is not referenced
• Added comprehensive test coverage for both import source and import defer scenarios

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[codspeed-hq]

CodSpeed Performance Report

Merging #17085 will not alter performance

_{Comparing c/12-18-fix_minifier_remove_unused_import_source_defer_statements (743488a) with main (fb9e193)¹}

Summary

✅ 38 untouched
⏩ 7 skipped²

Footnotes

1. No successful run was found on main (1cc4253) during the generation of this report, so fb9e193 was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩

2. 7 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. ↩

[sapphi-red]

Suggested change

	if import_decl.phase.is_some() {
	if let Some(phase) = import_decl.phase {
	let (ImportPhase::Defer | ImportPhase::Source) = phase;

I'm not sure if this is idiomatic, but I think it'd be nice to have this check so that we notice we have to verify the condition here when a new phase is added.

[sapphi-red]

Suggested change

	test_same_options("import defer * as a from 'a'; foo(a.bar);", &options);
	test_same_options("import defer * as a from 'a'; foo(a);", &options);
	test_same_options("import defer * as a from 'a'; foo(a.bar);", &options);