rust-lang/rust — pull request #18958 by pcwalton (2014-11-14 17:24:10+00:00)
Title: librustc: Always parse `macro!()`/`macro![]` as expressions if not

followed by a semicolon.

This allows code like `vec![1i, 2, 3].len();` to work.

This breaks code that uses macros as statements without putting
semicolons after them, such as:

fn main() {
...
assert!(a == b)
assert!(c == d)
println(...);
}

It also breaks code that uses macros as items without semicolons:

fn main() {
local_data_key!(foo)

println("hello world")
}

Add semicolons to fix this code. Those two examples can be fixed as
follows:

fn main() {
...
assert!(a == b);
assert!(c == d);
println(...);
}

fn main() {
local_data_key!(foo);

println("hello world")
}

RFC #378.

Closes #18635.

[breaking-change]

r? @alexcrichton