Add duplicate arguments check (#8)

Cargo.lock

@@ -1493,7 +1493,7 @@ dependencies = [
 
 [[package]]
 name = "rust-python-linter"
-version = "0.0.7"
+version = "0.0.8"
 dependencies = [
  "anyhow",
  "bincode",

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "rust-python-linter"
-version = "0.0.7"
+version = "0.0.8"
 edition = "2021"
 
 [lib]

resources/test/src/foo.py

@@ -1 +1,5 @@
 from bar import *
+
+
+def baz(x: int, x: int) -> None:
+    pass

src/check.rs

@@ -3,6 +3,7 @@ use serde::{Deserialize, Serialize};
 
 #[derive(Serialize, Deserialize)]
 pub enum CheckKind {
+    DuplicateArgumentName,
     ImportStarUsage,
     IfTuple,
 }
@@ -11,16 +12,18 @@ impl CheckKind {
     /// A four-letter shorthand code for the check.
     pub fn code(&self) -> &'static str {
         match self {
-            CheckKind::ImportStarUsage => "F403",
+            CheckKind::DuplicateArgumentName => "F831",
             CheckKind::IfTuple => "F634",
+            CheckKind::ImportStarUsage => "F403",
         }
     }
 
     /// The body text for the check.
     pub fn body(&self) -> &'static str {
         match self {
-            CheckKind::ImportStarUsage => "Unable to detect undefined names",
+            CheckKind::DuplicateArgumentName => "Duplicate argument name in function definition",
             CheckKind::IfTuple => "If test is a tuple, which is always `True`",
+            CheckKind::ImportStarUsage => "Unable to detect undefined names",
         }
     }
 }

src/checker.rs

@@ -1,7 +1,9 @@
-use rustpython_parser::ast::{ExprKind, Stmt, StmtKind, Suite};
+use std::collections::HashSet;
+
+use rustpython_parser::ast::{Arg, Arguments, ExprKind, Stmt, StmtKind, Suite};
 
 use crate::check::{Check, CheckKind};
-use crate::visitor::{walk_stmt, Visitor};
+use crate::visitor::{walk_arguments, walk_stmt, Visitor};
 
 struct Checker {
     checks: Vec<Check>,
@@ -32,6 +34,38 @@ impl Visitor for Checker {
         }
         walk_stmt(self, stmt);
     }
+
+    fn visit_arguments(&mut self, arguments: &Arguments) {
+        // Collect all the arguments into a single vector.
+        let mut all_arguments: Vec<&Arg> = arguments
+            .posonlyargs
+            .iter()
+            .chain(arguments.kwonlyargs.iter())
+            .chain(arguments.args.iter())
+            .collect();
+        if let Some(arg) = &arguments.vararg {
+            all_arguments.push(arg);
+        }
+        if let Some(arg) = &arguments.kwarg {
+            all_arguments.push(arg);
+        }
+
+        // Search for duplicates.
+        let mut idents: HashSet<String> = HashSet::new();
+        for arg in all_arguments {
+            let ident = &arg.node.arg;
+            if idents.contains(ident) {
+                self.checks.push(Check {
+                    kind: CheckKind::DuplicateArgumentName,
+                    location: arg.location,
+                });
+                break;
+            }
+            idents.insert(ident.clone());
+        }
+
+        walk_arguments(self, arguments);
+    }
 }
 
 pub fn check_ast(python_ast: &Suite) -> Vec<Check> {