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Mixing async functions and &mut leads to overflow evaluating requirement #55809

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agrif opened this issue Nov 9, 2018 · 7 comments
Closed

Mixing async functions and &mut leads to overflow evaluating requirement #55809

agrif opened this issue Nov 9, 2018 · 7 comments

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@agrif
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@agrif agrif commented Nov 9, 2018

Code:

#![feature(async_await, await_macro, futures_api)]

// Consider this a stand-in for tokio::io::AsyncRead
trait Foo { }
impl Foo for () { }
impl<'a, T> Foo for &'a mut T where T: Foo { }

// Consider this a stand-in for tokio::io::read
async fn foo_async<T>(_v: T) -> u8 where T: Foo {
    0
}

// this should just act exactly like foo_async...
async fn bad<T>(v: T) -> u8 where T: Foo {
    await!(foo_async(v))
}

// let's see if it is!
async fn async_main() {
    let mut v = ();
    
    // compiler error:
    let _ = await!(bad(&mut v));
    // totally fine:
    let _ = await!(foo_async(&mut v));
    // also totally fine:
    let _ = await!(bad(v));
}

fn main() {
    let _ = async_main();
}

Playground.

This fails to compile:

Compiling playground v0.0.1 (/playground)
error[E0275]: overflow evaluating the requirement `[static generator@src/main.rs:9:49: 11:2 {}]: std::marker::Freeze`
  |
  = help: consider adding a `#![recursion_limit="128"]` attribute to your crate
  = note: required because of the requirements on the impl of `std::marker::Freeze` for `[static generator@src/main.rs:9:49: 11:2 {}]`
[ ... line repeated many, many times ... ]
  = note: required because it appears within the type `impl std::future::Future`
  = note: required because it appears within the type `impl std::future::Future`
  = note: required because it appears within the type `{impl std::future::Future, ()}`
  = note: required because it appears within the type `[static generator@src/main.rs:14:42: 16:2 v:&mut () {impl std::future::Future, ()}]`
  = note: required because it appears within the type `std::future::GenFuture<[static generator@src/main.rs:14:42: 16:2 v:&mut () {impl std::future::Future, ()}]>`
  = note: required because it appears within the type `impl std::future::Future`
  = note: required because it appears within the type `impl std::future::Future`
  = note: required because it appears within the type `for<'r, 's> {(), impl std::future::Future, impl std::future::Future, impl std::future::Future}`
  = note: required because it appears within the type `[static generator@src/main.rs:19:23: 28:2 for<'r, 's> {(), impl std::future::Future, impl std::future::Future, impl std::future::Future}]`

error: aborting due to previous error

For more information about this error, try `rustc --explain E0275`.
error: Could not compile `playground`.

This might be related to #50674, except that the code that triggers it seems more likely to be valid. I ran into this bug when trying to use tokio to read data and pass it off to serde. At the very least, the error message is extremely confusing.

Slightly modifying this code will occasionally trigger another compiler error (something about DeBruijn indices) but I have lost the exact code that triggers it.

@paracat
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@paracat paracat commented Nov 25, 2018

i have produced the same error in a project:

https://github.com/paracat/reflow/commit/d25aa1f4364c70f512d58cb6946d56faece5b5d8

though i haven't extracted a minimal snippet, the cause of the problem is in the latest commit that only changes several lines

i have also found the code that produces the DeBruijn error. It's the commit before this one. It seems whether ? is used for error handling matters

apart from the two last commits that produce these two different errors, previous commits compile fine

i believe this is related to #53989

@nikomatsakis
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@nikomatsakis nikomatsakis commented Feb 22, 2019

Maybe related to #55809 ?

@eminence
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@eminence eminence commented Feb 23, 2019

@nikomatsakis that link is just back to this same issue. What issue did you actually mean to link?

@nikomatsakis
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@nikomatsakis nikomatsakis commented Mar 5, 2019

@eminence good point, I don't remember anymore =)

@nikomatsakis
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@nikomatsakis nikomatsakis commented Mar 5, 2019

Marking as blocking -- we should be trying to figure out what is happening here, at least, and deciding whether to block on it.

@nikomatsakis nikomatsakis self-assigned this Mar 5, 2019
@nikomatsakis
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@nikomatsakis nikomatsakis commented Mar 5, 2019

Assigning to myself to try and do some investigation.

@nikomatsakis nikomatsakis removed their assignment Mar 5, 2019
@davidtwco davidtwco self-assigned this Mar 12, 2019
davidtwco added a commit to davidtwco/rust that referenced this issue Mar 13, 2019
This commit adds a regression test for rust-lang#55809 which checks that a
overflow does not occur when evaluating a requirement for async
functions and `&mut` arguments in some specific circumstances.
@davidtwco
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@davidtwco davidtwco commented Mar 13, 2019

This code compiles successfully when I check locally against nightly and a build of master, I've submitted #59156 with a regression test.

Centril added a commit to Centril/rust that referenced this issue Mar 13, 2019
[wg-async-await] Add regression test for rust-lang#55809.

Fixes rust-lang#55809.

This PR adds a regression test for rust-lang#55809 which checks that a
overflow does not occur when evaluating a requirement for async
functions and `&mut` arguments in some specific circumstances.
Mark-Simulacrum added a commit to Mark-Simulacrum/rust that referenced this issue Mar 14, 2019
[wg-async-await] Add regression test for rust-lang#55809.

Fixes rust-lang#55809.

This PR adds a regression test for rust-lang#55809 which checks that a
overflow does not occur when evaluating a requirement for async
functions and `&mut` arguments in some specific circumstances.
kennytm added a commit to kennytm/rust that referenced this issue Mar 15, 2019
[wg-async-await] Add regression test for rust-lang#55809.

Fixes rust-lang#55809.

This PR adds a regression test for rust-lang#55809 which checks that a
overflow does not occur when evaluating a requirement for async
functions and `&mut` arguments in some specific circumstances.
bors added a commit that referenced this issue Mar 15, 2019
Rollup of 31 pull requests

Successful merges:

 - #58803 (fs::copy() unix: set file mode early)
 - #58854 (appveyor: Use VS2017 for all our images)
 - #58855 (std: Spin for a global malloc lock on wasm32)
 - #58873 (Fix "Auto-hide item methods documentation" setting)
 - #58933 (Move alloc::prelude::* to alloc::prelude::v1, make alloc a subset of std)
 - #58938 (core: ensure VaList passes improper_ctypes lint)
 - #58941 (MIPS: add r6 support)
 - #58949 (SGX target: Expose thread id function in os module)
 - #58976 (Default to integrated `rust-lld` linker for UEFI targets)
 - #58986 ([CI] Update binutils for powerpc64 and powerpc64le)
 - #59009 (Fix SGX implementations of read/write_vectored.)
 - #59025 (Fix generic argument lookup for Self)
 - #59036 (Fix ICE in MIR pretty printing)
 - #59037 (Avoid some common false positives in intra doc link checking)
 - #59038 (Track embedded-book in the toolstate)
 - #59072 (we can now skip should_panic tests with the libtest harness)
 - #59079 (add suggestions to invalid macro item error)
 - #59082 (A few improvements to comments in user-facing crates)
 - #59102 (Consistent naming for duration_float methods and additional f32 methods)
 - #59106 (Add peer_addr function to UdpSocket)
 - #59118 (rustc: fix ICE when trait alias has bare Self)
 - #59139 (Unregress using scalar unions in constants.)
 - #59146 (Suggest return lifetime when there's only one named lifetime)
 - #59147 (Make std time tests more robust for platform differences)
 - #59152 (Stabilize Range*::contains.)
 - #59156 ([wg-async-await] Add regression test for #55809.)
 - #59158 (Revert "Don't generate minification variable if minification disabled")
 - #59169 (Add `-Z allow_features=...` flag)
 - #59175 (Don't run test launching `echo` since that doesn't exist on Windows)
 - #59180 (Use try blocks in rustc_codegen_ssa)
 - #59185 (No old chestnuts in iter::repeat docs)

Failed merges:

 - #58901 (Change `std::fs::copy` to use `copyfile` on MacOS and iOS)
 - #59055 (CI: Set job names.)

r? @ghost
Centril added a commit to Centril/rust that referenced this issue Mar 16, 2019
[wg-async-await] Add regression test for rust-lang#55809.

Fixes rust-lang#55809.

This PR adds a regression test for rust-lang#55809 which checks that a
overflow does not occur when evaluating a requirement for async
functions and `&mut` arguments in some specific circumstances.
kennytm added a commit to kennytm/rust that referenced this issue Mar 16, 2019
[wg-async-await] Add regression test for rust-lang#55809.

Fixes rust-lang#55809.

This PR adds a regression test for rust-lang#55809 which checks that a
overflow does not occur when evaluating a requirement for async
functions and `&mut` arguments in some specific circumstances.
bors added a commit that referenced this issue Mar 16, 2019
Rollup of 37 pull requests

Successful merges:

 - #58854 (appveyor: Use VS2017 for all our images)
 - #58855 (std: Spin for a global malloc lock on wasm32)
 - #58873 (Fix "Auto-hide item methods documentation" setting)
 - #58901 (Change `std::fs::copy` to use `copyfile` on MacOS and iOS)
 - #58933 (Move alloc::prelude::* to alloc::prelude::v1, make alloc a subset of std)
 - #58938 (core: ensure VaList passes improper_ctypes lint)
 - #58941 (MIPS: add r6 support)
 - #58949 (SGX target: Expose thread id function in os module)
 - #58976 (Default to integrated `rust-lld` linker for UEFI targets)
 - #58986 ([CI] Update binutils for powerpc64 and powerpc64le)
 - #59009 (Fix SGX implementations of read/write_vectored.)
 - #59025 (Fix generic argument lookup for Self)
 - #59036 (Fix ICE in MIR pretty printing)
 - #59037 (Avoid some common false positives in intra doc link checking)
 - #59038 (Track embedded-book in the toolstate)
 - #59072 (we can now skip should_panic tests with the libtest harness)
 - #59079 (add suggestions to invalid macro item error)
 - #59082 (A few improvements to comments in user-facing crates)
 - #59102 (Consistent naming for duration_float methods and additional f32 methods)
 - #59118 (rustc: fix ICE when trait alias has bare Self)
 - #59139 (Unregress using scalar unions in constants.)
 - #59146 (Suggest return lifetime when there's only one named lifetime)
 - #59147 (Make std time tests more robust for platform differences)
 - #59152 (Stabilize Range*::contains.)
 - #59156 ([wg-async-await] Add regression test for #55809.)
 - #59158 (Revert "Don't generate minification variable if minification disabled")
 - #59169 (Add `-Z allow_features=...` flag)
 - #59173 (bootstrap: Default to a sensible llvm-suffix.)
 - #59175 (Don't run test launching `echo` since that doesn't exist on Windows)
 - #59180 (Use try blocks in rustc_codegen_ssa)
 - #59185 (No old chestnuts in iter::repeat docs)
 - #59201 (Remove restriction on isize/usize in repr(simd))
 - #59204 (Output diagnostic information for rustdoc)
 - #59206 (Improved test output)
 - #59208 (Reduce a Code Repetition Related to Bit Operation)
 - #59212 (Add x86_64 musl host to the manifest)
 - #59221 (Option and Result: Add references to documentation of as_ref and as_mut)

Failed merges:

 - #59055 (CI: Set job names.)

r? @ghost
bors added a commit that referenced this issue Mar 16, 2019
Rollup of 37 pull requests

Successful merges:

 - #58854 (appveyor: Use VS2017 for all our images)
 - #58855 (std: Spin for a global malloc lock on wasm32)
 - #58873 (Fix "Auto-hide item methods documentation" setting)
 - #58901 (Change `std::fs::copy` to use `copyfile` on MacOS and iOS)
 - #58933 (Move alloc::prelude::* to alloc::prelude::v1, make alloc a subset of std)
 - #58938 (core: ensure VaList passes improper_ctypes lint)
 - #58941 (MIPS: add r6 support)
 - #58949 (SGX target: Expose thread id function in os module)
 - #58976 (Default to integrated `rust-lld` linker for UEFI targets)
 - #58986 ([CI] Update binutils for powerpc64 and powerpc64le)
 - #59009 (Fix SGX implementations of read/write_vectored.)
 - #59025 (Fix generic argument lookup for Self)
 - #59036 (Fix ICE in MIR pretty printing)
 - #59037 (Avoid some common false positives in intra doc link checking)
 - #59038 (Track embedded-book in the toolstate)
 - #59072 (we can now skip should_panic tests with the libtest harness)
 - #59079 (add suggestions to invalid macro item error)
 - #59082 (A few improvements to comments in user-facing crates)
 - #59102 (Consistent naming for duration_float methods and additional f32 methods)
 - #59118 (rustc: fix ICE when trait alias has bare Self)
 - #59139 (Unregress using scalar unions in constants.)
 - #59146 (Suggest return lifetime when there's only one named lifetime)
 - #59147 (Make std time tests more robust for platform differences)
 - #59152 (Stabilize Range*::contains.)
 - #59156 ([wg-async-await] Add regression test for #55809.)
 - #59158 (Revert "Don't generate minification variable if minification disabled")
 - #59169 (Add `-Z allow_features=...` flag)
 - #59173 (bootstrap: Default to a sensible llvm-suffix.)
 - #59175 (Don't run test launching `echo` since that doesn't exist on Windows)
 - #59180 (Use try blocks in rustc_codegen_ssa)
 - #59185 (No old chestnuts in iter::repeat docs)
 - #59201 (Remove restriction on isize/usize in repr(simd))
 - #59204 (Output diagnostic information for rustdoc)
 - #59206 (Improved test output)
 - #59208 (Reduce a Code Repetition Related to Bit Operation)
 - #59212 (Add x86_64 musl host to the manifest)
 - #59221 (Option and Result: Add references to documentation of as_ref and as_mut)

Failed merges:

 - #59055 (CI: Set job names.)

r? @ghost
kennytm added a commit to kennytm/rust that referenced this issue Mar 16, 2019
[wg-async-await] Add regression test for rust-lang#55809.

Fixes rust-lang#55809.

This PR adds a regression test for rust-lang#55809 which checks that a
overflow does not occur when evaluating a requirement for async
functions and `&mut` arguments in some specific circumstances.
bors added a commit that referenced this issue Mar 16, 2019
Rollup of 37 pull requests

Successful merges:

 - #58854 (appveyor: Use VS2017 for all our images)
 - #58855 (std: Spin for a global malloc lock on wasm32)
 - #58873 (Fix "Auto-hide item methods documentation" setting)
 - #58901 (Change `std::fs::copy` to use `copyfile` on MacOS and iOS)
 - #58933 (Move alloc::prelude::* to alloc::prelude::v1, make alloc a subset of std)
 - #58938 (core: ensure VaList passes improper_ctypes lint)
 - #58941 (MIPS: add r6 support)
 - #58949 (SGX target: Expose thread id function in os module)
 - #58959 (Add release notes for PR #56243)
 - #58976 (Default to integrated `rust-lld` linker for UEFI targets)
 - #59009 (Fix SGX implementations of read/write_vectored.)
 - #59025 (Fix generic argument lookup for Self)
 - #59036 (Fix ICE in MIR pretty printing)
 - #59037 (Avoid some common false positives in intra doc link checking)
 - #59072 (we can now skip should_panic tests with the libtest harness)
 - #59079 (add suggestions to invalid macro item error)
 - #59082 (A few improvements to comments in user-facing crates)
 - #59102 (Consistent naming for duration_float methods and additional f32 methods)
 - #59118 (rustc: fix ICE when trait alias has bare Self)
 - #59139 (Unregress using scalar unions in constants.)
 - #59146 (Suggest return lifetime when there's only one named lifetime)
 - #59147 (Make std time tests more robust for platform differences)
 - #59152 (Stabilize Range*::contains.)
 - #59156 ([wg-async-await] Add regression test for #55809.)
 - #59158 (Revert "Don't generate minification variable if minification disabled")
 - #59169 (Add `-Z allow_features=...` flag)
 - #59173 (bootstrap: Default to a sensible llvm-suffix.)
 - #59175 (Don't run test launching `echo` since that doesn't exist on Windows)
 - #59180 (Use try blocks in rustc_codegen_ssa)
 - #59185 (No old chestnuts in iter::repeat docs)
 - #59201 (Remove restriction on isize/usize in repr(simd))
 - #59204 (Output diagnostic information for rustdoc)
 - #59206 (Improved test output)
 - #59208 (Reduce a Code Repetition Related to Bit Operation)
 - #59212 (Add x86_64 musl host to the manifest)
 - #59221 (Option and Result: Add references to documentation of as_ref and as_mut)
 - #59231 (Stabilize Option::copied)
@bors bors closed this in #59156 Mar 16, 2019
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