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SwatinemSwatinem
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Add test for Future inflating arg size to 3x
This adds one more test that should track improvements to generator layout, like rust-lang#62958 and rust-lang#62575. In particular, this test highlights suboptimal layout, as the storage for the argument future is not being reused across its usage as `upvar`, `local` and `awaitee` (being polled to completion).
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‎tests/ui/async-await/future-sizes/async-awaiting-fut.rs

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// compile-flags: -Z print-type-sizes --crate-type lib
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// edition:2021
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// build-pass
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// ignore-pass
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async fn wait() {}
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async fn big_fut(arg: [u8; 1024]) {}
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async fn calls_fut(fut: impl std::future::Future<Output = ()>) {
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loop {
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wait().await;
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if true {
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return fut.await;
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} else {
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wait().await;
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}
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}
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}
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pub async fn test() {
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let fut = big_fut([0u8; 1024]);
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calls_fut(fut).await;
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}

‎tests/ui/async-await/future-sizes/async-awaiting-fut.stdout

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print-type-size type: `[async fn body@$DIR/async-awaiting-fut.rs:21:21: 24:2]`: 3078 bytes, alignment: 1 bytes
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print-type-size discriminant: 1 bytes
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print-type-size variant `Unresumed`: 0 bytes
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print-type-size variant `Suspend0`: 3077 bytes
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print-type-size local `.__awaitee`: 3077 bytes, offset: 0 bytes, alignment: 1 bytes
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print-type-size variant `Returned`: 0 bytes
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print-type-size variant `Panicked`: 0 bytes
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print-type-size type: `[async fn body@$DIR/async-awaiting-fut.rs:10:64: 19:2]`: 3077 bytes, alignment: 1 bytes
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print-type-size discriminant: 1 bytes
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print-type-size variant `Unresumed`: 2051 bytes
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print-type-size padding: 1026 bytes
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print-type-size upvar `.fut`: 1025 bytes, alignment: 1 bytes
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print-type-size variant `Suspend0`: 2052 bytes
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print-type-size local `.fut`: 1025 bytes, offset: 0 bytes, alignment: 1 bytes
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print-type-size local `..generator_field4`: 1 bytes
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print-type-size padding: 1 bytes
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print-type-size upvar `.fut`: 1025 bytes, alignment: 1 bytes
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print-type-size local `.__awaitee`: 1 bytes
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print-type-size variant `Suspend1`: 3076 bytes
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print-type-size padding: 1024 bytes
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print-type-size local `..generator_field4`: 1 bytes, alignment: 1 bytes
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print-type-size padding: 1 bytes
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print-type-size upvar `.fut`: 1025 bytes, alignment: 1 bytes
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print-type-size local `.__awaitee`: 1025 bytes
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print-type-size variant `Suspend2`: 2052 bytes
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print-type-size local `.fut`: 1025 bytes, offset: 0 bytes, alignment: 1 bytes
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print-type-size local `..generator_field4`: 1 bytes
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print-type-size padding: 1 bytes
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print-type-size upvar `.fut`: 1025 bytes, alignment: 1 bytes
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print-type-size local `.__awaitee`: 1 bytes
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print-type-size variant `Returned`: 2051 bytes
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print-type-size padding: 1026 bytes
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print-type-size upvar `.fut`: 1025 bytes, alignment: 1 bytes
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print-type-size variant `Panicked`: 2051 bytes
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print-type-size padding: 1026 bytes
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print-type-size upvar `.fut`: 1025 bytes, alignment: 1 bytes
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print-type-size type: `std::mem::ManuallyDrop<[async fn body@$DIR/async-awaiting-fut.rs:10:64: 19:2]>`: 3077 bytes, alignment: 1 bytes
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print-type-size field `.value`: 3077 bytes
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print-type-size type: `std::mem::MaybeUninit<[async fn body@$DIR/async-awaiting-fut.rs:10:64: 19:2]>`: 3077 bytes, alignment: 1 bytes
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print-type-size variant `MaybeUninit`: 3077 bytes
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print-type-size field `.uninit`: 0 bytes
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print-type-size field `.value`: 3077 bytes
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print-type-size type: `[async fn body@$DIR/async-awaiting-fut.rs:8:35: 8:37]`: 1025 bytes, alignment: 1 bytes
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print-type-size discriminant: 1 bytes
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print-type-size variant `Unresumed`: 1024 bytes
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print-type-size upvar `.arg`: 1024 bytes, offset: 0 bytes, alignment: 1 bytes
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print-type-size variant `Returned`: 1024 bytes
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print-type-size upvar `.arg`: 1024 bytes, offset: 0 bytes, alignment: 1 bytes
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print-type-size variant `Panicked`: 1024 bytes
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print-type-size upvar `.arg`: 1024 bytes, offset: 0 bytes, alignment: 1 bytes
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print-type-size type: `std::mem::ManuallyDrop<[async fn body@$DIR/async-awaiting-fut.rs:8:35: 8:37]>`: 1025 bytes, alignment: 1 bytes
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print-type-size field `.value`: 1025 bytes
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print-type-size type: `std::mem::MaybeUninit<[async fn body@$DIR/async-awaiting-fut.rs:8:35: 8:37]>`: 1025 bytes, alignment: 1 bytes
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print-type-size variant `MaybeUninit`: 1025 bytes
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print-type-size field `.uninit`: 0 bytes
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print-type-size field `.value`: 1025 bytes
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print-type-size type: `[async fn body@$DIR/async-awaiting-fut.rs:6:17: 6:19]`: 1 bytes, alignment: 1 bytes
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print-type-size discriminant: 1 bytes
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print-type-size variant `Unresumed`: 0 bytes
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print-type-size variant `Returned`: 0 bytes
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print-type-size variant `Panicked`: 0 bytes
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print-type-size type: `std::mem::ManuallyDrop<bool>`: 1 bytes, alignment: 1 bytes
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print-type-size field `.value`: 1 bytes
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print-type-size type: `std::mem::MaybeUninit<bool>`: 1 bytes, alignment: 1 bytes
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print-type-size variant `MaybeUninit`: 1 bytes
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print-type-size field `.uninit`: 0 bytes
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print-type-size field `.value`: 1 bytes
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print-type-size type: `std::task::Poll<()>`: 1 bytes, alignment: 1 bytes
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print-type-size discriminant: 1 bytes
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print-type-size variant `Ready`: 0 bytes
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print-type-size field `.0`: 0 bytes
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print-type-size variant `Pending`: 0 bytes

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