Add size tests for moved locals in generators

Author: tmandry

src/test/run-pass/async-await/async-fn-size-moved-locals.rs

@@ -0,0 +1,98 @@
+// Test that we don't duplicate storage for futures moved around in .await, and
+// for futures moved into other futures.
+//
+// The exact sizes can change by a few bytes (we'd like to know when they do).
+// What we don't want to see is the wrong multiple of 1024 (the size of BigFut)
+// being reflected in the size.
+//
+// See issue #59123 for a full explanation.
+
+// edition:2018
+
+#![feature(async_await)]
+
+use std::future::Future;
+use std::pin::Pin;
+use std::task::{Context, Poll};
+
+const BIG_FUT_SIZE: usize = 1024;
+struct BigFut([u8; BIG_FUT_SIZE]);
+
+impl BigFut {
+    fn new() -> Self {
+        BigFut([0; BIG_FUT_SIZE])
+    } }
+
+impl Drop for BigFut {
+    fn drop(&mut self) {}
+}
+
+impl Future for BigFut {
+    type Output = ();
+
+    fn poll(self: Pin<&mut Self>, _ctx: &mut Context<'_>) -> Poll<Self::Output> {
+        Poll::Ready(())
+    }
+}
+
+#[allow(dead_code)]
+struct Joiner {
+    a: Option<BigFut>,
+    b: Option<BigFut>,
+    c: Option<BigFut>,
+}
+
+impl Future for Joiner {
+    type Output = ();
+
+    fn poll(self: Pin<&mut Self>, _ctx: &mut Context<'_>) -> Poll<Self::Output> {
+        Poll::Ready(())
+    }
+}
+
+fn noop() {}
+
+async fn single() {
+    let x = BigFut::new();
+    x.await;
+}
+
+async fn single_with_noop() {
+    let x = BigFut::new();
+    noop();
+    x.await;
+}
+
+async fn joined() {
+    let a = BigFut::new();
+    let b = BigFut::new();
+    let c = BigFut::new();
+
+    let joiner = Joiner {
+        a: Some(a),
+        b: Some(b),
+        c: Some(c),
+    };
+    joiner.await
+}
+
+async fn joined_with_noop() {
+    let a = BigFut::new();
+    let b = BigFut::new();
+    let c = BigFut::new();
+
+    let joiner = Joiner {
+        a: Some(a),
+        b: Some(b),
+        c: Some(c),
+    };
+    noop();
+    joiner.await
+}
+
+fn main() {
+    assert_eq!(1028, std::mem::size_of_val(&single()));
+    assert_eq!(1032, std::mem::size_of_val(&single_with_noop()));
+    assert_eq!(3084, std::mem::size_of_val(&joined()));
+    assert_eq!(3084, std::mem::size_of_val(&joined_with_noop()));
+}

src/test/run-pass/generator/size-moved-locals.rs

@@ -0,0 +1,48 @@
+// Test that we don't duplicate storage for a variable that is moved to another
+// binding. This used to happen in the presence of unwind and drop edges (see
+// `complex` below.)
+//
+// The exact sizes here can change (we'd like to know when they do). What we
+// don't want to see is the `complex` generator size being upwards of 2048 bytes
+// (which would indicate it is reserving space for two copies of Foo.)
+//
+// See issue #59123 for a full explanation.
+
+// edition:2018
+
+#![feature(generators, generator_trait)]
+
+use std::ops::Generator;
+
+const FOO_SIZE: usize = 1024;
+struct Foo([u8; FOO_SIZE]);
+
+impl Drop for Foo {
+    fn drop(&mut self) {}
+}
+
+fn simple() -> impl Generator<Yield = (), Return = ()> {
+    static || {
+        let first = Foo([0; FOO_SIZE]);
+        let _second = first;
+        yield;
+        // _second dropped here
+    }
+}
+
+fn noop() {}
+
+fn complex() -> impl Generator<Yield = (), Return = ()> {
+    static || {
+        let first = Foo([0; FOO_SIZE]);
+        noop();
+        let _second = first;
+        yield;
+        // _second dropped here
+    }
+}
+
+fn main() {
+    assert_eq!(1028, std::mem::size_of_val(&simple()));
+    assert_eq!(1032, std::mem::size_of_val(&complex()));
+}