Bail on any found recursion when expanding opaque types

[hkratz]

Fixes #87450. More of a bandaid because it does not fix the exponential complexity of the type folding used for opaque type expansion.

[rust-highfive]

Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @davidtwco (or someone else) soon.

Please see the contribution instructions for more information.

[davidtwco]

Could you add the test case from #87450?

[lqd]

Since this test is exercizing exponential compile times, how long does it take to compile with this PR ? (it would be good not to slow down CI and contributors' tests too much with a huge stress test :)

[hkratz]

Since this test is exercizing exponential compile times, how long does it take to compile with this PR ? (it would be good not to slow down CI and contributors' tests too much with a huge stress test :)

It is pretty fast on the testcase from issue 87450: From >400 seconds with master down to 0.06:

$ rm build/x86_64-unknown-linux-gnu/test/ui/impl-trait/issue-87450/stamp; ./x.py test src/test/ui/impl-trait/issue-87450.rs
[...]
test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured; 12184 filtered out; finished in 0.06s

One would need to add much more recursion to get a significant runtime (i.e. >20 wrap() calls).

[davidtwco]

@bors r+

[bors]

📌 Commit 2aa1996 has been approved by davidtwco

[bors]

⌛ Testing commit 2aa1996 with merge 92f015cefdfc37b37b6e9392a638f1fc9fdf3b7f...

[rust-log-analyzer]

The job x86_64-gnu-aux failed! Check out the build log: (web) (plain)

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

error: RPC failed; curl 56 GnuTLS recv error (-54): Error in the pull function.
fatal: The remote end hung up unexpectedly
fatal: early EOF
fatal: index-pack failed
thread 'main' panicked at 'assertion failed: status.success()', src/tools/cargotest/main.rs:125:13
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

command did not execute successfully: "/checkout/obj/build/x86_64-unknown-linux-gnu/stage0-tools-bin/cargotest" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2-tools-bin/cargo" "/checkout/obj/build/ct"
expected success, got: exit status: 101
expected success, got: exit status: 101


Build completed unsuccessfully in 0:24:57
make: *** [check-aux] Error 1
Makefile:44: recipe for target 'check-aux' failed

[bors]

💔 Test failed - checks-actions

[hkratz]

error: RPC failed; curl 56 GnuTLS recv error (-54): Error in the pull function.
fatal: The remote end hung up unexpectedly

Looks like an intermittent connectivity issue?

[jyn514]

@bors retry

[bors]

⌛ Testing commit 2aa1996 with merge 8d57c0a...

[bors]

☀️ Test successful - checks-actions
Approved by: davidtwco
Pushing 8d57c0a to master...