From 652231a683bfa927472e5d5a3410e11c9484a684 Mon Sep 17 00:00:00 2001
From: Noah <33094578+coolreader18@users.noreply.github.com>
Date: Fri, 13 Mar 2020 20:22:46 -0500
Subject: [PATCH 1/2] Error on positional-only parameters passed as keywords

---
 vm/src/obj/objfunction.rs | 17 +++++++++++++++--
 1 file changed, 15 insertions(+), 2 deletions(-)

diff --git a/vm/src/obj/objfunction.rs b/vm/src/obj/objfunction.rs
index 703c8bfae8..c363dd5281 100644
--- a/vm/src/obj/objfunction.rs
+++ b/vm/src/obj/objfunction.rs
@@ -15,7 +15,8 @@ use crate::pyobject::{
 };
 use crate::scope::Scope;
 use crate::slots::{SlotCall, SlotDescriptor};
-use crate::vm::VirtualMachine;
+use crate::VirtualMachine;
+use itertools::Itertools;
 
 pub type PyFunctionRef = PyRef<PyFunction>;
 
@@ -72,6 +73,7 @@ impl PyFunction {
     ) -> PyResult<()> {
         let nargs = func_args.args.len();
         let nexpected_args = code_object.arg_names.len();
+        let posonly_args = &code_object.arg_names[..code_object.posonlyarg_count];
 
         // This parses the arguments from args and kwargs into
         // the proper variables keeping into account default values
@@ -126,12 +128,16 @@ impl PyFunction {
             bytecode::Varargs::None => None,
         };
 
+        let mut posonly_passed_as_kwarg = Vec::new();
         // Handle keyword arguments
         for (name, value) in func_args.kwargs {
             // Check if we have a parameter with this name:
             if code_object.arg_names.contains(&name) || code_object.kwonlyarg_names.contains(&name)
             {
-                if locals.contains_key(&name, vm) {
+                if posonly_args.contains(&name) {
+                    posonly_passed_as_kwarg.push(name);
+                    continue;
+                } else if locals.contains_key(&name, vm) {
                     return Err(
                         vm.new_type_error(format!("Got multiple values for argument '{}'", name))
                     );
@@ -146,6 +152,13 @@ impl PyFunction {
                 );
             }
         }
+        if !posonly_passed_as_kwarg.is_empty() {
+            return Err(vm.new_type_error(format!(
+                "{}() got some positional-only arguments passed as keyword arguments: '{}'",
+                &code_object.obj_name,
+                posonly_passed_as_kwarg.into_iter().format(", "),
+            )));
+        }
 
         // Add missing positional arguments, if we have fewer positional arguments than the
         // function definition calls for

From aad212299f4012b0bca8ddcc8e3c6e81959415a3 Mon Sep 17 00:00:00 2001
From: Noah <33094578+coolreader18@users.noreply.github.com>
Date: Fri, 13 Mar 2020 20:23:09 -0500
Subject: [PATCH 2/2] Add tests for positional/keyword only arguments

---
 tests/snippets/function_args.py | 17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/tests/snippets/function_args.py b/tests/snippets/function_args.py
index d1754a62f0..eb4f94b8a3 100644
--- a/tests/snippets/function_args.py
+++ b/tests/snippets/function_args.py
@@ -41,7 +41,6 @@ def va2(*args, **kwargs):
     assert args == (5, 4)
     assert len(kwargs) == 0
 
-
 va2(5, 4)
 x = (5, 4)
 va2(*x)
@@ -114,3 +113,19 @@ def f(a):
 y = {'a': 2}
 with assert_raises(TypeError):
     f(**x, **y)
+
+
+def f(a, b, /, c, d, *, e, f):
+    return a + b + c + d + e + f
+
+assert f(1,2,3,4,e=5,f=6) == 21
+assert f(1,2,3,d=4,e=5,f=6) == 21
+assert f(1,2,c=3,d=4,e=5,f=6) == 21
+with assert_raises(TypeError):
+    f(1,b=2,c=3,d=4,e=5,f=6)
+with assert_raises(TypeError):
+    f(a=1,b=2,c=3,d=4,e=5,f=6)
+with assert_raises(TypeError):
+    f(1,2,3,4,5,f=6)
+with assert_raises(TypeError):
+    f(1,2,3,4,5,6)