Remove the `CoroutineWitness` type #144157

compiler-errors · 2025-07-18T20:23:05Z

It's no longer needed, since it always just matches the def id and substs of the Coroutine that it's contained within.

This PR reworks a bit of obligation stalling logic and dtorck constraint behavior, but otherwise it's pretty straightforward.

This luckily was very easy to do because of the setup work in:

Unify CoroutineWitness sooner in typeck, and stall coroutine obligations based off of TypingEnv #141762

r? @lcnr or reassign (e.g. to oli, who probably would also be down to review)

compiler-errors · 2025-07-18T20:23:18Z

@bors2 try @rust-timer queue

(and crater when it's ready)

rust-bors · 2025-07-18T20:23:21Z

⌛ Trying commit a25d83f with merge 0282016…

To cancel the try build, run the command @bors2 try cancel.

Remove the `CoroutineWitness` type It's no longer needed, since it just always the `Coroutine` that it's contained within. This PR reworks a bit of obligation stalling logic and dtorck constraint behavior, but otherwise it's pretty straightforward. r? `@lcnr` or reassign (e.g. to oli, who probably would also be down to review)

compiler-errors · 2025-07-18T21:16:49Z

compiler/rustc_middle/src/ty/print/pretty.rs

@@ -905,6 +905,7 @@ pub trait PrettyPrinter<'tcx>: Printer<'tcx> + fmt::Write {
                    }
                } else {
                    p!(print_def_path(did, args));
+                    // TODO: Restore witness types?


I'll probably leave these out. Otherwise we could have query cycles here.

compiler-errors · 2025-07-18T21:18:24Z

compiler/rustc_ty_utils/src/needs_drop.rs

                        } else {
+                            // TODO: We could still recurse into upvars and the resume here.


This is definitely a FIXME for later. I don't think this has any side effect.

I don't think we should 😁 you could even inline always_drop_component to just return Err(AlwaysRequiresDrop) here

rust-bors · 2025-07-18T22:37:55Z

☀️ Try build successful (CI)
Build commit: 0282016 (028201683a76a5cd349729c6819c46607119c4e8, parent: 8f08b3a32478b8d0507732800ecb548a76e0fd0c)

rust-timer · 2025-07-18T23:47:30Z

Finished benchmarking commit (0282016): comparison URL.

Overall result: ✅ improvements - no action needed

Benchmarking this pull request means it may be perf-sensitive – we'll automatically label it not fit for rolling up. You can override this, but we strongly advise not to, due to possible changes in compiler perf.

@bors rollup=never
@rustbot label: -S-waiting-on-perf -perf-regression

Instruction count

Our most reliable metric. Used to determine the overall result above. However, even this metric can be noisy.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-0.2%	[-0.3%, -0.2%]	3
All ❌✅ (primary)	-	-	0

Max RSS (memory usage)

Results (secondary -3.8%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-3.8%	[-3.8%, -3.8%]	1
All ❌✅ (primary)	-	-	0

Cycles

This benchmark run did not return any relevant results for this metric.

Binary size

Results (primary -0.0%, secondary -0.3%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-0.0%	[-0.0%, -0.0%]	4
Improvements ✅ (secondary)	-0.3%	[-0.7%, -0.1%]	12
All ❌✅ (primary)	-0.0%	[-0.0%, -0.0%]	4

Bootstrap: 465.311s -> 466.27s (0.21%)
Artifact size: 374.60 MiB -> 374.58 MiB (-0.00%)

compiler-errors · 2025-07-18T23:49:47Z

@craterbot check

craterbot · 2025-07-18T23:50:02Z

👌 Experiment pr-144157 created and queued.
🤖 Automatically detected try build 0282016
🔍 You can check out the queue and this experiment's details.

ℹ️ Crater is a tool to run experiments across parts of the Rust ecosystem. Learn more

compiler/rustc_next_trait_solver/src/solve/trait_goals.rs

compiler/rustc_trait_selection/src/traits/query/dropck_outlives.rs

compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs

lcnr · 2025-07-21T08:15:09Z

compiler/rustc_trait_selection/src/traits/select/mod.rs

+                            })
+                    } else {
+                        unreachable!(
+                            "tried to assemble `Sized` for coroutine without enabled feature"


why does the copy_clone_conditions talk about Sized in the ICE msg xd

Copy paste mistake

still talks about Sized :3

compiler/rustc_trait_selection/src/traits/select/mod.rs

compiler/rustc_ty_utils/src/needs_drop.rs

tests/ui/coroutine/clone-impl.rs

lcnr

general question: do we need to stall on CoroutineClosure as well?

compiler-errors · 2025-07-21T13:04:53Z

general question: do we need to stall on CoroutineClosure as well?

No, coroutine-closures don't actually really "contain" a witness, and don't use it in their copy/clone and auto trait impls anyways. The fact it stores a witness in its vars is kinda just for convenience for constructing the coroutine type when computing the return type.

lcnr

gamer!

r=me, unsure whether to block on #144156. Waiting on crater seems fine, wouldn't expect there to be any issues though :3

compiler-errors · 2025-07-21T17:51:49Z

I'll land this after #144156, unless you expect that PR to be blocked for some reason.

In that case, I'd prefer if we invert the stack of these and land this PR without the first commit, and then rebase THAT one to use the new logic for checking the drop-ness of the interior types.

compiler-errors · 2025-07-21T17:52:00Z

I'll take this out of draft for the pings and to mark it as blocked.

rustbot · 2025-07-21T17:52:05Z

Some changes occurred in compiler/rustc_sanitizers

cc @rcvalle

Some changes occurred to the CTFE machinery

cc @RalfJung, @oli-obk, @lcnr

changes to the core type system

cc @compiler-errors, @lcnr

Some changes occurred to the core trait solver

cc @rust-lang/initiative-trait-system-refactor

Some changes occurred in compiler/rustc_codegen_cranelift

cc @bjorn3

Some changes occurred in src/tools/clippy

cc @rust-lang/clippy

Some changes occurred to the CTFE / Miri interpreter

cc @rust-lang/miri

Some changes occurred in exhaustiveness checking

cc @Nadrieril

This PR changes rustc_public

cc @oli-obk, @celinval, @ouz-a

Some changes occurred to MIR optimizations

cc @rust-lang/wg-mir-opt

Some changes occurred in compiler/rustc_codegen_ssa

cc @WaffleLapkin

compiler-errors · 2025-07-21T17:52:05Z

@rustbot blocked

rust-log-analyzer · 2025-07-21T18:39:36Z

The job aarch64-gnu-llvm-19-1 failed! Check out the build log: (web) (plain enhanced) (plain)

Click to see the possible cause of the failure (guessed by this bot)


---- [debuginfo-gdb] tests/debuginfo/function-names.rs stdout ----
NOTE: compiletest thinks it is using GDB version 15001000

error: check directive(s) from `/checkout/tests/debuginfo/function-names.rs` not found in debugger output. errors:
    (function-names.rs:40) `[...]static fn function_names::const_generic_fn_non_int<{CONST#ffa3db4ca1d52dce}>();`
the following subset of check directive(s) was found successfully:
    (function-names.rs:10) `90: static fn function_names::main();`
    (function-names.rs:12) `192: static fn function_names::generic_func<i32>(i32) -> i32;`
    (function-names.rs:16) `160: static fn function_names::GenericStruct<i32, i32>::impl_function<i32, i32>();`
    (function-names.rs:17) `148: static fn function_names::Mod1::TestStruct2::impl_function();`
    (function-names.rs:18) `132: static fn function_names::TestStruct1::impl_function();`
    (function-names.rs:22) `152: static fn function_names::Mod1::{impl#1}::trait_function();`
    (function-names.rs:23) `137: static fn function_names::{impl#1}::trait_function();`
    (function-names.rs:24) `169: static fn function_names::{impl#3}::trait_function<i32>();`
    (function-names.rs:25) `183: static fn function_names::{impl#5}::trait_function3<function_names::TestStruct1>();`
    (function-names.rs:26) `188: static fn function_names::{impl#6}::trait_function<i32, 1>();`
    (function-names.rs:30) `194: static fn function_names::generic_func::{closure#0}<i32>(*mut function_names::generic_func::{closure_env#0}<i32>);`
    (function-names.rs:31) `107: static fn function_names::main::{closure#0}(*mut function_names::main::{closure_env#0});`
    (function-names.rs:32) `162: static fn function_names::{impl#2}::impl_function::{closure#0}<i32, i32>(*mut function_names::{impl#2}::impl_function::{closure_env#0}<i32, i32>);`
    (function-names.rs:39) `200: static fn function_names::const_generic_fn_bool<false>();`
    (function-names.rs:41) `202: static fn function_names::const_generic_fn_signed_int<-7>();`
    (function-names.rs:42) `203: static fn function_names::const_generic_fn_unsigned_int<14>();`
status: exit status: 0
command: PYTHONPATH="/checkout/src/etc" "/usr/bin/gdb" "-quiet" "-batch" "-nx" "-command=/checkout/obj/build/aarch64-unknown-linux-gnu/test/debuginfo/function-names.gdb/function-names.debugger.script"
--- stdout -------------------------------
GNU gdb (Ubuntu 15.1-1ubuntu2) 15.1
Copyright (C) 2024 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.
Type "show copying" and "show warranty" for details.
This GDB was configured as "aarch64-linux-gnu".
Type "show configuration" for configuration details.
For bug reporting instructions, please see:
<https://www.gnu.org/software/gdb/bugs/>.
Find the GDB manual and other documentation resources online at:
    <http://www.gnu.org/software/gdb/documentation/>.

For help, type "help".
Type "apropos word" to search for commands related to "word".

File /checkout/tests/debuginfo/function-names.rs:
90: static fn function_names::main();
107: static fn function_names::main::{closure#0}(*mut function_names::main::{closure_env#0});
112: static fn function_names::main::{coroutine#1}(core::pin::Pin<&mut function_names::main::{coroutine_env#1}>, ()) -> core::ops::coroutine::CoroutineState<(), ()>;

File /rustc/FAKE_PREFIX/library/core/src/ptr/mod.rs:
804: static fn core::ptr::drop_in_place<function_names::main::{coroutine_env#1}>(*mut function_names::main::{coroutine_env#1});

File /checkout/tests/debuginfo/function-names.rs:
194: static fn function_names::generic_func::{closure#0}<i32>(*mut function_names::generic_func::{closure_env#0}<i32>);
192: static fn function_names::generic_func<i32>(i32) -> i32;

File /checkout/tests/debuginfo/function-names.rs:
160: static fn function_names::GenericStruct<i32, i32>::impl_function<i32, i32>();
148: static fn function_names::Mod1::TestStruct2::impl_function();
132: static fn function_names::TestStruct1::impl_function();
162: static fn function_names::{impl#2}::impl_function::{closure#0}<i32, i32>(*mut function_names::{impl#2}::impl_function::{closure_env#0}<i32, i32>);

File /checkout/tests/debuginfo/function-names.rs:
152: static fn function_names::Mod1::{impl#1}::trait_function();
137: static fn function_names::{impl#1}::trait_function();
169: static fn function_names::{impl#3}::trait_function<i32>();
183: static fn function_names::{impl#5}::trait_function3<function_names::TestStruct1>();
188: static fn function_names::{impl#6}::trait_function<i32, 1>();

File /checkout/tests/debuginfo/function-names.rs:
194: static fn function_names::generic_func::{closure#0}<i32>(*mut function_names::generic_func::{closure_env#0}<i32>);
107: static fn function_names::main::{closure#0}(*mut function_names::main::{closure_env#0});
162: static fn function_names::{impl#2}::impl_function::{closure#0}<i32, i32>(*mut function_names::{impl#2}::impl_function::{closure_env#0}<i32, i32>);

File /checkout/tests/debuginfo/function-names.rs:
200: static fn function_names::const_generic_fn_bool<false>();
201: static fn function_names::const_generic_fn_non_int<{CONST#a70c39591cb5f53d}>();
202: static fn function_names::const_generic_fn_signed_int<-7>();
203: static fn function_names::const_generic_fn_unsigned_int<14>();
------------------------------------------
stderr: none

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compiler-errors mentioned this pull request Jul 18, 2025

Check coroutine upvars in dtorck constraint #144156

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Check coroutine upvars and in dtorck constraint

5acaf41

compiler-errors force-pushed the no-witness branch from a25d83f to 56c25c2 Compare July 21, 2025 16:02

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compiler-errors added 2 commits July 21, 2025 17:27

Stall coroutines based off of ty::Coroutine, not ty::CoroutineWitness

61f4528

Extract borrowck coroutine drop-liveness hack

26b62b2

compiler-errors force-pushed the no-witness branch from 56c25c2 to 4625cb5 Compare July 21, 2025 17:27

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compiler-errors marked this pull request as ready for review July 21, 2025 17:52

rustbot added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Jul 21, 2025

rustbot added S-blocked Status: Blocked on something else such as an RFC or other implementation work. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Jul 21, 2025

compiler-errors added 2 commits July 21, 2025 17:53

Remove coroutine witness type

8edc110

Fix tools

4f96428

compiler-errors force-pushed the no-witness branch from 4625cb5 to 4f96428 Compare July 21, 2025 17:53

		} else {
		// TODO: We could still recurse into upvars and the resume here.

Remove the CoroutineWitness type #144157

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Remove the CoroutineWitness type #144157

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rust-timer commented Jul 18, 2025

Overall result: ✅ improvements - no action needed

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Remove the `CoroutineWitness` type #144157

Remove the `CoroutineWitness` type #144157

compiler-errors commented Jul 18, 2025 •

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