[R] Add a type method for Expression

[asfimport]

This would allow for more consistent syntax when extracting the type of an expression.

A block like this:

if (inherits(x, "Expression")) { 
class <- x$type()$ToString() 
} else { 
class <- type(x)$ToString() 
}

would be simplified to

class <- type(x)$ToString()

Reporter: Dragoș Moldovan-Grünfeld / @dragosmg
Assignee: Dragoș Moldovan-Grünfeld / @dragosmg

Related issues:

• [R] Implement bindings for lubridate::tz (Discovered while testing)

PRs and other links:

• GitHub Pull Request #12447

_{Note: This issue was originally created as ARROW-15712. Please see the migration documentation for further details.}

[asfimport]

Nicola Crane / @thisisnic:
Issue resolved by pull request 12447
#12447