Change:
<ins> error[E0107]: this enum takes 2 type arguments but only 1 type argument was supplied --> $DIR/issue-75883.rs:6:21 | LL |     pub fn run() -> Result<_> { |                     ^^^^^^ - supplied 1 type argument |                     | |                     expected 2 type arguments | note: enum defined here, with 2 type parameters: `T`, `E` --> $SRC_DIR/core/src/result.rs:LL:COL | LL | pub enum Result<T, E> { |          ^^^^^^ -  - help: add missing type argument | LL |     pub fn run() -> Result<_, E> { |                             ^^^ error[E0107]: this enum takes 2 type arguments but only 1 type argument was supplied --> $DIR/issue-75883.rs:15:35 | LL |     pub fn interact(&mut self) -> Result<_> { |                                   ^^^^^^ - supplied 1 type argument |                                   | |                                   expected 2 type arguments | note: enum defined here, with 2 type parameters: `T`, `E` --> $SRC_DIR/core/src/result.rs:LL:COL | LL | pub enum Result<T, E> { |          ^^^^^^ -  - help: add missing type argument | LL |     pub fn interact(&mut self) -> Result<_, E> { |                                           ^^^ error[E0121]: the type placeholder `_` is not allowed within types on item signatures --> $DIR/issue-75883.rs:15:42 | LL |     pub fn interact(&mut self) -> Result<_> { |                                          ^ not allowed in type signatures error[E0121]: the type placeholder `_` is not allowed within types on item signatures --> $DIR/issue-75883.rs:6:28 | LL |     pub fn run() -> Result<_> { |                            ^ not allowed in type signatures error: aborting due to 4 previous errors Some errors have detailed explanations: E0107, E0121. For more information about an error, try `rustc --explain E0107`. </ins>

Discussion:
<!-- If you're using the stable version of the compiler, you should also check if the bug also exists in the beta or nightly versions. --: Note: Same error on stable and beta. <!-- Include a backtrace in the code block by setting in your environment. E.g. . --<details<summary<strongBacktrace</strong</summary<p</p</details
this works for me on latest nightly. If you update your version of the compiler, does it work for you?
Oh oops, I was missing , sorry:
Slightly smaller: If you change to , it works, so I think this is while trying to infer .
glacier ""
This issue has been fixed by , marking as .

<!-- Thank you for finding an Internal Compiler Error! If possible, try to provide a minimal verifiable example. You can read "Rust Bug Minimization Patterns" for how to create smaller examples. --Hi, it appears that I've stumbled upon an internal compiler error. I'm sorry that I can't provide a minimal example, but I'm not on a level to understand what is going on (at least for now, heh :P). I'm just here, because the compiler told me to go here. I have, however, pushed a commit of my project in the state that yields the error: The error occurs when running or , for that matter. <!-- If you're using the stable version of the compiler, you should also check if the bug also exists in the beta or nightly versions. --: Also happens on nightly: <!-- Include a backtrace in the code block by setting in your environment. E.g. . --<details<summary<strongBacktrace</strong</summary<p</p</detailsI hope this helps. Please tell me, if there's more you need me to do.
reduced: `
modify labels: -E-needs-mcve
Assigning as and removing .
This ICEs since modify labels: +regression-from-stable-to-stable
This issue has been fixed by , marking as .