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feat(minifier): remove empty [] and {} declaration #16855

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Merged
Boshen merged 1 commit into from
Dec 15, 2025
Merged

feat(minifier): remove empty [] and {} declaration #16855

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28 changes: 20 additions & 8 deletions crates/oxc_minifier/src/peephole/remove_unused_declaration.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -18,16 +18,21 @@ impl<'a> PeepholeOptimizations {
if !Self::can_remove_unused_declarators(ctx) {
return false;
}
if let BindingPatternKind::BindingIdentifier(ident) = &decl.id.kind {
// Unsafe to remove `using`, unable to statically determine usage of [Symbol.dispose].
if decl.kind.is_using() {
return false;
}
if let Some(symbol_id) = ident.symbol_id.get() {
return ctx.scoping().symbol_is_unused(symbol_id);
// Unsafe to remove `using`, unable to statically determine usage of [Symbol.dispose].
if decl.kind.is_using() {
return false;
}
match &decl.id.kind {
BindingPatternKind::BindingIdentifier(ident) => {
if let Some(symbol_id) = ident.symbol_id.get() {
return ctx.scoping().symbol_is_unused(symbol_id);
}
false
}
BindingPatternKind::ArrayPattern(ident) => ident.is_empty(),
BindingPatternKind::ObjectPattern(ident) => ident.is_empty(),
BindingPatternKind::AssignmentPattern(_) => false,
}
false
}

pub fn remove_unused_variable_declaration(
Expand Down Expand Up @@ -117,6 +122,13 @@ mod test {
test_options("var x", "", &options);
test_options("var x = 1", "", &options);
test_options("var x = foo", "foo", &options);
test_options("var [] = []", "", &options);
test_options("var [] = [1]", "", &options);
test_options("var [] = [foo]", "foo", &options);
test_options("var {} = {}", "", &options);
test_options("var {} = { a: 1 }", "", &options);
test_options("var {} = { foo }", "foo", &options);
test_options("var {} = { foo: { a } }", "a", &options);
test_same_options("var x; foo(x)", &options);
test_same_options("export var x", &options);
test_same_options("using x = foo", &options);
Expand Down
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