Situation: we had code like:

type Foo interface {
  Bar(arg1, arg2 string)
  ...
}

and tests like:

do := func(arg1, arg2 string) { ... }
// ... bunch of code ...
myBarMock.EXPECT().Bar(wantArg1, wantArg2).Do(do)

Then we added an argument to Bar:

type Foo interface {
  Bar(arg1, arg2, arg3 string)
  ...
}

and updated the EXPECT():

do := func(arg1, arg2 string) { ... }
// ... bunch of code ...
myBarMock.EXPECT().Bar(wantArg1, wantArg2, wantArg3).Do(do)

... but forgot to update do. The result was "panic: reflect: Call with too many input arguments" with no strong indication that what was wrong was the do function, rather than some place where the third argument hadn't been added (e.g. missing wantArg3).
It would be nice if the message said something more obvious like "EXPECT.()Do() function doesn't match the mock signature".