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Prefer not to early return from derived visitables #124263

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Prefer not to early return from derived visitables #124263

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34 changes: 22 additions & 12 deletions compiler/rustc_macros/src/type_visitable.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -32,18 +32,29 @@ pub fn type_visitable_derive(mut s: synstructure::Structure<'_>) -> proc_macro2:
}

s.add_bounds(synstructure::AddBounds::Generics);
let body_visit = s.each(|bind| {
quote! {
match ::rustc_ast_ir::visit::VisitorResult::branch(
::rustc_middle::ty::visit::TypeVisitable::visit_with(#bind, __visitor)
) {
::core::ops::ControlFlow::Continue(()) => {},
::core::ops::ControlFlow::Break(r) => {
return ::rustc_ast_ir::visit::VisitorResult::from_residual(r);
},
let body_visit =
s.each_variant(|vi| {
if let Some((last, rest)) = vi.bindings().split_last() {
// Avoid early returning after visiting the final binding, so that LLVM can TCO the call.
rest.iter()
.map(|bind| quote! {
match ::rustc_ast_ir::visit::VisitorResult::branch(
::rustc_middle::ty::visit::TypeVisitable::visit_with(#bind, __visitor)
) {
::core::ops::ControlFlow::Continue(()) => {},
::core::ops::ControlFlow::Break(r) => {
return ::rustc_ast_ir::visit::VisitorResult::from_residual(r);
},
}
})
.chain(std::iter::once(quote! {
::rustc_middle::ty::visit::TypeVisitable::visit_with(#last, __visitor)
}))
.collect()
} else {
quote! { <__V::Result as ::rustc_ast_ir::visit::VisitorResult>::output() }
}
}
});
});
s.bind_with(|_| synstructure::BindStyle::Move);

s.bound_impl(
Expand All @@ -54,7 +65,6 @@ pub fn type_visitable_derive(mut s: synstructure::Structure<'_>) -> proc_macro2:
__visitor: &mut __V
) -> __V::Result {
match *self { #body_visit }
<__V::Result as ::rustc_ast_ir::visit::VisitorResult>::output()
}
},
)
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