chars() iterator no longer compiling

[CodingAnarchy]

Back a couple weeks ago, I had a program with this code here:

for ch in msg.chars() {
        if !ch.is_alphabetic() { continue; }
        let s = caesar_shift(ch, key);
        e.push(s);
    }

This code compiled just fine, where msg is an &str parameter to the function in question.

Now, having duplicated the same code with the same variable as:

for ch in msg.chars() {
            if !ch.is_alphabetic() { continue; }
            let p = ch.to_digit(36).unwrap() - 10;  // Need to shift down by 10 for range of 0-25
            let c = alpha.chars().nth(p as usize).unwrap();
            e.push(c);
        }

the compiler presents this error:

src/lib/classical.rs:163:9: 168:10 error: mismatched types:
 expected `collections::string::String`,
    found `()`
(expected struct `collections::string::String`,
    found ()) [E0308]
src/lib/classical.rs:163         for ch in msg.chars() {
src/lib/classical.rs:164             if !ch.is_alphabetic() { continue; }
src/lib/classical.rs:165             let p = ch.to_digit(36).unwrap() - 10;  // Need to shift down by 10 for range of 0-25
src/lib/classical.rs:166             let c = alpha.chars().nth(p as usize).unwrap();
src/lib/classical.rs:167             e.push(c);
src/lib/classical.rs:168         }
note: in expansion of for loop expansion
src/lib/classical.rs:163:9: 168:10 note: expansion site
src/lib/classical.rs:163:9: 168:10 help: run `rustc --explain E0308` to see a detailed explanation

This was using the nightly build in both cases:

Now: rustc 1.4.0-nightly (f3f23bf9c 2015-08-30)
Then: rustc 1.4.0-nightly (ab450ef22 2015-08-14)

Strangely, the old code does not cause the compiler to error out, but I see literally no difference in the new code to speak of that would cause it to not understand what type msg is.

[eefriedman]

Please provide a complete example when asking questions or filing bug reports; see http://stackoverflow.com/help/mcve etc.

Please don't ask support questions on the issue tracker; you can ask on StackOverflow (http://stackoverflow.com) or the Rust discussion forum at https://users.rust-lang.org/ .

The terrible error message is tracked by #25228 .

[CodingAnarchy]

Ok, it was in fact that there was no return value in a path far removed from the code in question.

But to be fair, this wasn't a support question - it's clearly an issue if the compiler looks at working code and flags it as the issue.

As the issue is already be tracked, I'll close this as a duplication of #25228.