Allow passing var kwarg with the same name as posonly arg

Author: msimacek

graalpython/com.oracle.graal.python.test/src/com/oracle/graal/python/test/grammar/PositionalOnlyArgTests.java

@@ -40,9 +40,10 @@
  */
 package com.oracle.graal.python.test.grammar;
 
-import com.oracle.graal.python.test.PythonTests;
 import org.junit.Test;
 
+import com.oracle.graal.python.test.PythonTests;
+
 public class PositionalOnlyArgTests {
 
     @Test
@@ -245,4 +246,12 @@ public void lambda04() {
                         "print(x(1, 2))";
         PythonTests.assertPrints("3\n", source);
     }
+
+    @Test
+    public void postionalOnlyOverlapsWithKwargs() {
+        String source = "def f(a, b, /, **kwargs):" +
+                        "  print(a, b, kwargs.get('a'))\n" +
+                        "f(1, 2, a=3)";
+        PythonTests.assertPrints("1 2 3\n", source);
+    }
 }

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/nodes/argument/CreateArgumentsNode.java

@@ -491,12 +491,17 @@ Object[] applyCached(Object callee, @SuppressWarnings("unused") Signature callee
 
                 if (kwIdx != -1) {
                     if (positionalOnlyArgIndex > -1 && kwIdx < positionalOnlyArgIndex) {
-                        throw raise.raise(PythonBuiltinClassType.TypeError, "%s() got some positional-only arguments passed as keyword arguments: '%s'", CreateArgumentsNode.getName(callee), name);
+                        if (unusedKeywords != null) {
+                            unusedKeywords[k++] = kwArg;
+                        } else {
+                            throw raise.raise(PythonBuiltinClassType.TypeError, "%s() got some positional-only arguments passed as keyword arguments: '%s'", CreateArgumentsNode.getName(callee), name);
+                        }
+                    } else {
+                        if (PArguments.getArgument(arguments, kwIdx) != null) {
+                            throw raise.raise(PythonBuiltinClassType.TypeError, "%s() got multiple values for argument '%s'", CreateArgumentsNode.getName(callee), name);
+                        }
+                        PArguments.setArgument(arguments, kwIdx, kwArg.getValue());
                     }
-                    if (PArguments.getArgument(arguments, kwIdx) != null) {
-                        throw raise.raise(PythonBuiltinClassType.TypeError, "%s() got multiple values for argument '%s'", CreateArgumentsNode.getName(callee), name);
-                    }
-                    PArguments.setArgument(arguments, kwIdx, kwArg.getValue());
                 } else if (unusedKeywords != null) {
                     unusedKeywords[k++] = kwArg;
                 } else {