Incorrect type mismatch resolving when using return in closure

[seppo0010]

The following code is failing to compile in stable and nightly

fn main() {
    let a = |hello| { return hello + 1; };
    let _ = a(2);
}

with the following message:

rustc 1.15.0 (10893a9a3 2017-01-19)
error[E0271]: type mismatch resolving `<i32 as std::ops::Add>::Output == ()`
 --> <anon>:2:30
  |
2 |     let a = |hello| { return hello + 1; };
  |                              ^^^^^^^^^ expected i32, found ()
  |
  = note: expected type `i32`
  = note:    found type `()`

error: aborting due to previous error

If I remove the return and the semicolon, it works as expected.

Adding the type i32 to _ or adding a type to the parameter (e.g.: 2u32) fixes the problem.

[Spoonbender]

Triage: no change