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Variable labeling of complex match arms should be able to label the whole arm #673

@steveklabnik

Description

@steveklabnik

Issue by Manishearth
Friday Jun 27, 2014 at 17:41 GMT

For earlier discussion, see rust-lang/rust#15219

This issue was labelled with: B-RFC, I-papercut in the Rust repository


If I have a match arm like this:

0x2A | 0x2D | 0x2E | 0x30 .. 0x39 | 0x41 .. 0x5A | 0x5F | 0x61..0x7A => {}

the following does not work:

a @ 0x2A | 0x2D | 0x2E | 0x30 .. 0x39 | 0x41 .. 0x5A | 0x5F | 0x61..0x7A => {println("{}",a)}
a @ (0x2A | 0x2D | 0x2E | 0x30 .. 0x39 | 0x41 .. 0x5A | 0x5F | 0x61..0x7A) => {println("{}",a)}

In the former example, the a is bound to the first literal only, and in the latter the compiler thinks that it is a tuple (and complains about the lack of commas).

Of course, one can do

a @ 0x2A | a @ 0x2D | a@ 0x2E | a@ 0x30 .. 0x39 /* etc */=> {println("{}",a)}

but that is cumbersome.

Could we get a way to easily bind a variable to the entire match arm?

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