move arguments check from axline function into _AxLine class

johan12345 · johan12345 · commit da0b3449512d · 2020-10-26T07:46:30.000+01:00
diff --git a/lib/matplotlib/axes/_axes.py b/lib/matplotlib/axes/_axes.py
@@ -843,11 +843,6 @@ def axline(self, xy1, xy2=None, *, slope=None, **kwargs):
 
             >>> axline((0, 0), (1, 1), linewidth=4, color='r')
         """
-        if (xy2 is None and slope is None or
-                xy2 is not None and slope is not None):
-            raise TypeError(
-                "Exactly one of 'xy2' and 'slope' must be given")
-
         if slope is not None and (self.get_xscale() != 'linear' or
                                   self.get_yscale() != 'linear'):
             raise TypeError("'slope' cannot be used with non-linear scales")
diff --git a/lib/matplotlib/lines.py b/lib/matplotlib/lines.py
@@ -1406,6 +1406,12 @@ class _AxLine(Line2D):
 
     def __init__(self, xy1, xy2, slope, **kwargs):
         super().__init__([0, 1], [0, 1], **kwargs)
+        
+        if (xy2 is None and slope is None or
+                xy2 is not None and slope is not None):
+            raise TypeError(
+                "Exactly one of 'xy2' and 'slope' must be given")
+
         self._slope = slope
         self._xy1 = xy1
         self._xy2 = xy2
