Fix use of invoke

[yuyichao]

• Use tuple type instead of tuples (Ref Inline invoke (take 3) plus a few other tweaks julia#18444 and it's easier to infer in general)
• Use eval instead of invoke to see newly defined methods. The old method won't work after Inline invoke (take 3) plus a few other tweaks julia#18444 or after automatic recompilation of dependent functions julia#265 is fixed.

[stevengj]

Thanks. (Travis failure seems to be an unrelated Conda download timeout.)