Bug report

Bug summary

I occasionally want the alpha value of the patch in a histogram's legend to be different than the alpha value used to plot the legend. However, when I call set_alpha on a legend handle, the color of the patch in the legend changes.

Code for reproduction

import matplotlib.pyplot as plt

plt.hist([1, 2, 3], alpha = 0.25, label = 'data', color = 'red')
legend = plt.legend()
for lh in legend.legendHandles:
    lh.set_alpha(1.0)

Actual outcome

Work-around

I can get the result I desire if I call set_edgecolor() and set_facecolor():

plt.hist([1, 2, 3], alpha = 0.25, label = 'data', color = 'red')
legend = plt.legend()
for lh in legend.legendHandles:
    lh.set_facecolor(lh.get_facecolor())
    lh.set_edgecolor(lh.get_edgecolor())
    lh.set_alpha(1.0)

Expected outcome

Matplotlib version

• Matplotlib v2.2.2
• Installed from Anaconda (default channel)
• Backend: module://ipykernel.pylab.backend_inline
• Jupyter version: 5.5.0