Remove conflicting AsRef implementation for PyObject #5897

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1. coderabbitai

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   youknowone

   on Jul 4, 2025
2. youknowone commented on Jul 4, 2025

   

   youknowone

   on Jul 4, 2025

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   @coderabbitai Please make a patch to remove it

   👀React with 👀1Reacted by coderabbitai
3. coderabbitai commented on Jul 4, 2025

   

   coderabbitaibot

   on Jul 4, 2025 – with coderabbitai

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   🏁 Script executed:

   #!/bin/bash
   # Fetch information about issue #5897 from the RustPython repository
   gh issue view 5897 --repo RustPython/RustPython --json title,body,state,labels,comments --jq '{title: .title, body: .body, state: .state, labels: [.labels[].name], comments: [.comments[].body]}'
   

   Length of output: 1100

   ---

   🏁 Script executed:

   #!/bin/bash
   # First, let's examine the current implementation around lines 865-870 in vm/src/object/core.rs
   sed -n '860,875p' vm/src/object/core.rs
   

   Length of output: 359

   ---

   🏁 Script executed:

   #!/bin/bash
   # Let's get more context around this implementation to understand the full scope
   sed -n '850,880p' vm/src/object/core.rs
   

   Length of output: 592

   ---

   Task: Remove conflicting AsRef implementation for PyObject

   • Remove the conflicting impl AsRef<Self> for PyObject block from vm/src/object/core.rs
   • This resolves the compilation conflict with std's blanket implementation

   @youknowone I've planned the patch to remove the conflicting AsRef<Self> for PyObject implementation from vm/src/object/core.rs. The issue is that this custom implementation conflicts with Rust's standard library blanket implementation impl<T> AsRef<T> for T.

   The solution is to simply remove the custom implementation since it's redundant - PyObject will still have AsRef<PyObject> functionality through the standard library's blanket implementation. Another agent will execute the actual code changes.

   ---

   ⏳ Preparing changes...
4. coderabbitai commented on Jul 4, 2025

   

   coderabbitaibot

   on Jul 4, 2025 – with coderabbitai

   Last edited by coderabbitai

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   A summary of the changes CodeRabbit can apply:

   • Remove the conflicting impl AsRef<Self> for PyObject block from lines 865-870 in vm/src/object/core.rs to resolve overlap with Rust’s standard library blanket implementation and prevent trait implementation conflicts.

   A summary of the context that CodeRabbit is considering across the codebase:

   Let me verify the exact location and content of the conflicting AsRef implementation.

   Show context details

   Shell Result:

   Shell script executed:
   

   sed -n '860,875p' vm/src/object/core.rs

   Output:
   

   fn as_ref(&self) -> &PyObject {
       self
   }
   

   }

   impl AsRef for PyObject {
   #[inline(always)]
   fn as_ref(&self) -> &Self {
   self
   }
   }

   impl<'a, T: PyObjectPayload> From<&'a Py> for &'a PyObject {
   #[inline(always)]
   fn from(py_ref: &'a Py) -> Self {
   py_ref.as_object()

   I need to understand why this implementation conflicts with the standard library's blanket implementation.

   Show context details

   Web Result:

   Web search query executed:

   rust "impl AsRef<Self> for T" blanket implementation conflict standard library
   

   Result:

   The Rust standard library has a known conflict issue with a "blanket implementation" that looks like this:
   
   ```rust
   impl<T> AsRef<T> for T {
       fn as_ref(&self) -> &T {
           self
       }
   }
   ```
   
   This implementation is effectively saying for any type `T`, `T` implements `AsRef<T>` by simply returning a reference to itself.
   
   ### Why is it called a "blanket implementation"?
   Because it applies universally to all types `T`.
   
   ### Conflict Issues:
   If you try to write your own implementation like:
   
   ```rust
   impl<T> AsRef<Self> for T {
       // Some code here
   }
   ```
   
   or similarly overlapping implementations, the Rust compiler will complain about conflicting implementations (overlapping or conflicting trait implementations) because the standard library's impl is very broad and already covers cases involving `AsRef` for the same type `T`.
   
   ### Explanation:
   - The standard library's `impl<T> AsRef<T> for T` is a blanket impl that covers all types and says that each type implements `AsRef` of itself.
   - If you try to create an implementation that overlaps or conflicts with this, e.g., `impl AsRef<Self> for T` or a type that could be the same as `T`, then Rust won't allow it due to the orphan rules and coherence rules.
   - Rust requires all trait implementations to be non-overlapping and unambiguous.
   
   ### How can you avoid this conflict?
   - Avoid implementing `impl AsRef<Self> for T` generically.
   - Use more specific or different types for your implementations instead of universal or generic `T`.
   - Implement `AsRef<U>` for a specific type `T` where `U` is not `T`.
   - Newtype pattern: Wrap the type and implement traits on the wrapper.
   
   ---
   
   If you want, I can help with a code example or more detailed help for a specific use case. Would you like that?
   

   • Executed edits - (🔄 Check again to try again)
5. coderabbitai commented on Jul 4, 2025

   

   coderabbitaibot

   on Jul 4, 2025 – with coderabbitai

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   Creating a PR to execute the edits....

   The changes have been created in this pull request: View PR
6. youknowone

   closed this as completedon Jul 5, 2025