Prepare for moving the parser into the Ruff monorepo (#40)

ruff_python_ast/Cargo.toml

@@ -0,0 +1,15 @@
+[package]
+name = "ruff_python_ast"
+version = "0.2.0"
+description = "AST definitions for Ruff"
+authors = ["Charlie Marsh <charlie.r.marsh@gmail.com>"]
+edition = "2021"
+repository = "https://github.com/astral-sh/ruff"
+license = "MIT"
+
+[dependencies]
+ruff_text_size = { workspace = true }
+
+is-macro = { workspace = true }
+num-bigint = { workspace = true }
+static_assertions = { workspace = true }

ruff_python_ast/src/lib.rs

@@ -0,0 +1,48 @@
+//! Python AST node definitions and utilities.
+//!
+//! AST nodes are very similary defined like [Python AST](https://docs.python.org/3/library/ast.html).
+//! But a few exceptions exist due to ruff_python_parser optimization.
+//! They can be transformed to matching Python-styled AST in reasonable cost.
+//!
+//! [PythonArguments] is replaced by [Arguments]. The new [Arguments] type representation uses a new type
+//! [ArgWithDefault] to represent arguments with default values. See each type documentation for more details.
+//!
+//! A few top-level sum types are renamed to human friendly names.
+//! [CmpOp] refers `cmpop`
+//! [UnaryOp] refers `unaryop`
+//! [BoolOp] refers `boolop`
+//! [WithItem] refers `withitem`
+//! [ExceptHandler] refers `excepthandler`
+//!
+
+mod nodes;
+
+pub use nodes::*;
+use ruff_text_size::{TextRange, TextSize};
+
+pub trait Ranged {
+    fn range(&self) -> TextRange;
+
+    fn start(&self) -> TextSize {
+        self.range().start()
+    }
+
+    fn end(&self) -> TextSize {
+        self.range().end()
+    }
+}
+
+impl Ranged for TextRange {
+    fn range(&self) -> TextRange {
+        *self
+    }
+}
+
+impl<T> Ranged for &T
+where
+    T: Ranged,
+{
+    fn range(&self) -> TextRange {
+        T::range(self)
+    }
+}