manual_map suggestion cannot be applied: if let.. else if let .. chain

[matthiaskrgr]

Lint name: manual_map

I tried this code:

fn fun(a: Option<i32>) -> Option<i32> {
    if let Some(i) = a {
        Some(1 + i)
    } else if let Some(j) = a {
        Some(3 + j)
    } else {
        None
    }
}

Clippy suggests this:

warning: manual implementation of `Option::map`
  --> src/main.rs:8:12
   |
8  |       } else if let Some(j) = a {
   |  ____________^
9  | |         Some(3 + j)
10 | |     } else {
11 | |         None
12 | |     }
   | |_____^ help: try this: `a.map(|j| 3 + j)`
   |
   = note: `#[warn(clippy::manual_map)]` on by default
   = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#manual_map

warning: 2 warnings emitted

but it fails to apply because we have an if .. else if .. else chain which is not taken into account and the suggestion causes syntax errors.

The following errors were reported:
error: expected `{`, found `a`
 --> src/main.rs:8:12
  |
8 |     } else a.map(|j| 3 + j)
  |            ^---------------
  |            |
  |            expected `{`
  |            help: try placing this code inside a block: `{ a.map(|j| 3 + j) }`

error: aborting due to previous error

cc @Jarcho ?

[camsteffen]

I think it should still suggest with a block else { a.map(|j| 3 + j) }, so not a false positive.