Enable patterns in return syntax about test-case HOT 3 CLOSED

Right now you might do this:

#[test_case(2, 2 => 2 + 2)]
fn test(a: usize, b: usize) -> usize { a + b }

which is pretty nice, but it means we need have a way to distinguish between expression and pattern.

Two ideas:

• Breaking change: Let change => token into -> token inside attribute macro for expressions and use => for patterns.
• Use match keyword to indicate pattern

#[test_case(MyEnum::Foo('a', 5) => match MyEnum::Foo(_, 5))]

But this is ambiguous - you don't know if match is a match expression or only pattern indication.

• Use pat or pattern new keyword to indicate pattern

#[test_case(MyEnum::Foo('a', 5) => pattern MyEnum::Foo(_, 5))]

from test-case.

I have been working on parser combinators library and pattern matching was necessary.
So I created on my local branch solution:

#[test_case("abcd" => matches (Foo("a", "bc"), _) )]
#[test_case("abcd" => (Foo("a", "bc"), "d") )] // Simple assert_eq! comparison when no keyword used.
#[test_case("ab"   => panics "[Bar]" )]
#[test_case(""     => panics "[Baz, Bar(Bar)]" )]
fn test<'a, T: Debug>(input: &'a str) -> (T, &'a str) {
    parse(input).unwrap()
}

This solution uses two new keywords: matches for pattern matching and panics for adding #[should_panic(expected = "[Bar]") attribute.

It is backward compatible so I don't have to sed few thousands of tests, and it solves two issues at the same time.

from test-case.

Created v1.0.0-alpha-1 with this feature because it's really useful for me :)

from test-case.