From 21669a023bee939af0114291c4e1b8edb0d7d96e Mon Sep 17 00:00:00 2001
From: "Vazrupe (HyeonGyu Lee)" <vazrupe@naver.com>
Date: Mon, 23 Sep 2019 18:24:47 +0900
Subject: [PATCH] Add duplicate keyword argument error

Fixes #116
---
 Cargo.lock                      |  1 +
 parser/src/error.rs             |  4 ++++
 parser/src/function.rs          | 15 +++++++++++++++
 tests/snippets/function_args.py |  7 +++++++
 4 files changed, 27 insertions(+)

diff --git a/Cargo.lock b/Cargo.lock
index 1dc654460..02c6349b6 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -1221,6 +1221,7 @@ dependencies = [
  "cfg-if 0.1.9 (registry+https://github.com/rust-lang/crates.io-index)",
  "futures 0.1.29 (registry+https://github.com/rust-lang/crates.io-index)",
  "js-sys 0.3.27 (registry+https://github.com/rust-lang/crates.io-index)",
+ "num-bigint 0.2.3 (registry+https://github.com/rust-lang/crates.io-index)",
  "num-traits 0.2.8 (registry+https://github.com/rust-lang/crates.io-index)",
  "rustpython-compiler 0.1.0",
  "rustpython-parser 0.1.0",
diff --git a/parser/src/error.rs b/parser/src/error.rs
index fc53ebb0d..c946ee854 100644
--- a/parser/src/error.rs
+++ b/parser/src/error.rs
@@ -21,6 +21,7 @@ pub enum LexicalErrorType {
     UnicodeError,
     NestingError,
     PositionalArgumentError,
+    DuplicateKeywordArgumentError,
     UnrecognizedToken { tok: char },
     FStringError(FStringErrorType),
     OtherError(String),
@@ -33,6 +34,9 @@ impl fmt::Display for LexicalErrorType {
             LexicalErrorType::FStringError(error) => write!(f, "Got error in f-string: {}", error),
             LexicalErrorType::UnicodeError => write!(f, "Got unexpected unicode"),
             LexicalErrorType::NestingError => write!(f, "Got unexpected nesting"),
+            LexicalErrorType::DuplicateKeywordArgumentError => {
+                write!(f, "keyword argument repeated")
+            }
             LexicalErrorType::PositionalArgumentError => {
                 write!(f, "positional argument follows keyword argument")
             }
diff --git a/parser/src/function.rs b/parser/src/function.rs
index 552bdfd10..d20cf8a9a 100644
--- a/parser/src/function.rs
+++ b/parser/src/function.rs
@@ -1,3 +1,5 @@
+use std::collections::HashSet;
+
 use crate::ast;
 use crate::error::{LexicalError, LexicalErrorType};
 
@@ -6,9 +8,22 @@ type FunctionArgument = (Option<Option<String>>, ast::Expression);
 pub fn parse_args(func_args: Vec<FunctionArgument>) -> Result<ast::ArgumentList, LexicalError> {
     let mut args = vec![];
     let mut keywords = vec![];
+
+    let mut keyword_names = HashSet::with_capacity(func_args.len());
     for (name, value) in func_args {
         match name {
             Some(n) => {
+                if let Some(keyword_name) = n.clone() {
+                    if keyword_names.contains(&keyword_name) {
+                        return Err(LexicalError {
+                            error: LexicalErrorType::DuplicateKeywordArgumentError,
+                            location: value.location.clone(),
+                        });
+                    }
+
+                    keyword_names.insert(keyword_name.clone());
+                }
+
                 keywords.push(ast::Keyword { name: n, value });
             }
             None => {
diff --git a/tests/snippets/function_args.py b/tests/snippets/function_args.py
index 903a43f9b..4441c9416 100644
--- a/tests/snippets/function_args.py
+++ b/tests/snippets/function_args.py
@@ -95,3 +95,10 @@ assert kwargs == [('a', 1), ('b', 2)]
 
 kwargs = func(a=1, b=2, c=3)
 assert kwargs == [('a', 1), ('b', 2), ('c', 3)]
+
+
+def inc(n):
+    return n + 1
+
+with assert_raises(SyntaxError):
+    exec("inc(n=1, n=2)")