avoid generating inlined keyword unpacking code when signature has only optional arguments

Cython/Compiler/Nodes.py

@@ -2055,9 +2055,13 @@ class DefNode(FuncDefNode):
         code.putln('}')
 
         # now fill up the required arguments with values from the kw dict
-        code.putln('switch (PyTuple_GET_SIZE(%s)) {' % Naming.args_cname)
-        needs_break = False
+        last_required_arg = -1
         for i, arg in enumerate(all_args):
+            if not arg.default:
+                last_required_arg = i
+        if last_required_arg >= 0:
+            code.putln('switch (PyTuple_GET_SIZE(%s)) {' % Naming.args_cname)
+            for i, arg in enumerate(all_args[:last_required_arg+1]):
                 if i <= max_positional_args:
                     if self.star_arg and i == max_positional_args:
                         code.putln('default:')
@@ -2065,10 +2069,7 @@ class DefNode(FuncDefNode):
                         code.putln('case %2d:' % i)
                 if arg.default:
                     # handled in ParseOptionalKeywords() below
-                needs_break = True
                     continue
-            else:
-                needs_break = False
                 code.putln('values[%d] = PyDict_GetItem(%s, %s);' % (
                         i, Naming.kwds_cname, arg.name_entry.pystring_cname))
                 if i < min_positional_args:
@@ -2095,8 +2096,6 @@ class DefNode(FuncDefNode):
                                 self.name.utf8encode(), arg.name_entry.pystring_cname))
                         code.putln(code.error_goto(self.pos))
                         code.putln('}')
-        if needs_break:
-            code.putln('break;')
             code.putln('}')
 
         code.putln('if (unlikely(kw_args > 0)) {')