18 lines
679 B
Rust
18 lines
679 B
Rust
macro_rules! if_downcast_into {
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($in_ty:ty, $out_ty:ty, $val:ident, $body:expr) => ({
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if std::any::TypeId::of::<$in_ty>() == std::any::TypeId::of::<$out_ty>() {
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// Store the value in an `Option` so we can `take`
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// it after casting to `&mut dyn Any`.
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let mut slot = Some($val);
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// Re-write the `$val` ident with the downcasted value.
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let $val = (&mut slot as &mut dyn std::any::Any)
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.downcast_mut::<Option<$out_ty>>()
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.unwrap()
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.take()
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.unwrap();
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// Run the $body in scope of the replaced val.
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$body
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}
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})
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}
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