The value no longer satisfies the constraint after passing through `identity`, which seems counterintuitive
Open
Nobody has claimed this yet.
A-type-system
C-discussion
T-compiler
T-types
- Dominant language
- Rust
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- 119k
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Description
use std::convert::identity;
fn foo<F: for<'a> FnOnce(&'a ()) -> &'a ()>(f: F) {
f(&());
}
fn main() {
//foo(identity(|x| x));
foo(|x| x);
}
I'm not sure if this is a generic or something issue
Contributor guide
First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
Start by compiling the minimal Rust snippet in the issue and compare the behavior of the direct closure with the identity version. Trace the relevant generic and trait-bound handling in the compiler, then confirm the behavior with a focused regression test or a documented explanation of the constraint.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- rust
- Domain
- compilers
- Issue type
- Bug
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Activity status
- Stale
- Clarity
- Needs clarification
- Newbie friendliness
- 25/100