Can't call methods on a macro invocation

[kmcallister]

vec!().is_empty() fails to parse with "unexpected token: .". An extra set of parentheses around vec!() is required.

[alexcrichton]

Closing as a dupe of #5941. Currently it's a limitation that if a macro starts a line that it expands to a statement instead of an expression, and you've also discovered the current workaround.