Require named arguments after * in argument list

Author: msimacek

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/parser/antlr/Python3.g4

@@ -544,6 +544,11 @@ typedargslist [ArgDefListBuilder args]
             ( ',' ( kwargsparameter[args] ','? )? )?
 	| kwargsparameter[args] ','?
     )
+    {
+        if (!args.validateArgumentsAfterSplat()) {
+            throw new PythonRecognitionException("named arguments must follow bare *", this, _input, $ctx, getCurrentToken());
+        }
+    }
 ;
 
 defparameter [ArgDefListBuilder args]
@@ -609,6 +614,11 @@ varargslist returns [ArgDefListBuilder result]
                 ( ',' (vkwargsparameter[args] ','? )? )?
             | vkwargsparameter[args] ','?
 	)
+    {
+        if (!args.validateArgumentsAfterSplat()) {
+            throw new PythonRecognitionException("named arguments must follow bare *", this, _input, $ctx, getCurrentToken());
+        }
+    }
 	{ $result = args; }
 ;
 

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/parser/sst/ArgDefListBuilder.java

@@ -213,6 +213,10 @@ public boolean hasSplat() {
         return splatIndex > -1;
     }
 
+    public boolean validateArgumentsAfterSplat() {
+        return !(splatIndex > -1 && args != null && args.get(splatIndex).name == null && paramNames.size() <= splatIndex);
+    }
+
     /**
      *
      * @return The index to the positional only argument marker ('/'). Which means that all