feat: reorganize Rust code style guidelines in AGENTS.md for clarity, no expect, panic

Author: kosiew

AGENTS.md

@@ -17,8 +17,7 @@
 - All modules, classes, and functions should include docstrings.
 - Tests must use descriptive function names, pytest style assertions, and be
   grouped in classes when appropriate.
-- Rust code must pass `cargo fmt`, `cargo clippy`, and `cargo tomlfmt` and
-  should omit unnecessary parentheses around `if` conditions.
+- Rust code must pass `cargo fmt`, `cargo clippy`, and `cargo tomlfmt`.
 - Install the pre-commit hooks with `pre-commit install` and run them with
   `pre-commit run --files <file1> <file2>` or `pre-commit run --all-files`.
 
@@ -36,6 +35,18 @@ If installation is blocked by a proxy, see the [offline installation guide](http
   - `./ci/scripts/rust_clippy.sh`
   - `./ci/scripts/rust_toml_fmt.sh`
 
+## Rust Code Style
+
+When generating Rust code for DataFusion, follow these guidelines:
+
+1. Do not add unnecessary parentheses around `if` conditions:
+   - Correct: `if some_condition`
+   - Incorrect: `if (some_condition)`
+
+2. Do not use `expect()` or `panic!()` except in tests - use proper error handling with `Result` types
+
+3. Follow the standard Rust style conventions from rustfmt
+
 ## Code Organization
 - Keep functions focused and under about 50 lines.
 - Break complex tasks into well-named helper functions and reuse existing