let-defined lambdas aren't combined.

[tcr]

Similar to how top-level functions with multiple definitions are folded into a match statement (see the comment "There are multiple impls of this function, so expand this into a case statement" in convert.rs for code that can be reused) lambdas with multiple definitions should be folded into one match statement also.

To repro, save this as test.hs:

module Test()
where

example :: ()
example = do
    let isDefault (Just condition) = Left condition
        isDefault Nothing = Right ()

Running cargo run --manifest-path corollary/Cargo.toml -- test.hs currently outputs this:

// Original file: "test.hs"
// File auto-generated using Corollary.

#[macro_use] use corollary_support::*;

pub fn example() -> () {
    /*do*/ {
        let isDefault = |Some(condition)| {
            Left(condition)
        };

        let isDefault = |None| {
            Right(())
        };
    }
}

Expected output:

pub fn example() -> () {
    /*do*/ {
        let isDefault = |_0| {
            match _0 {
                Some(condition) {
                    Left(condition)
                }
                None {
                    Right(())
                }
            }
        };
    }
}