rust-macro-comma-test

Comprehensive test suite for trailing comma support in macros provided by std.

Read the source here.

The //~ tags in the source denote the compiler output on the latest version that this test was run (beta channel, the day before the 1.22 release). They do not actually do anything, and they most certainly do not represent the desired compiler output. (If you want to try seeing what happens if you stick this file in rust-lang/rust/src/test/compile-fail, though, be my guest.)

Running the test

git clone https://github.com/ExpHP/rust-macro-comma-test
cd rust-macro-comma-test

cargo build

# to additionally test concat_idents! and select!
cargo build --features=nightly

(you'll have to eyeball the output against the source to make sense of the results)

Caveats

This only tests the treatment of an extra , at the end of a valid list of arguments. It does not check that e.g. mac!(,) or mac!(arg,,) are forbidden. (Those are worth testing since they're backcompat hazards; but I left them out for now to make the file easier to review, so that it is not a random mixture of "desirable" errors and "undesirable" errors.)