confusing diagnostic when variable name equals function name

[matthiaskrgr]

rustc 1.30.0-nightly (02cb8f2a4 2018-08-29)
code:

struct VersionInfo {
    commit_hash: Option<String>,
}

impl VersionInfo {
    pub fn new() -> VersionInfo {
        let commit_hash: Option<String>;

        if false {
            commit_hash = commit_hash();
        } else {
            commit_hash = Some(String::from("bla"));
        }

        VersionInfo {
            commit_hash,
        }
    }
}


fn commit_hash() -> Option<String> {
    Some("hi".to_string())
}

This causes a very confusing error message

error[E0618]: expected function, found enum variant `commit_hash`
  --> rustc_tools_util/src/lib.rs:11:27
   |
8  |         let commit_hash: Option<String>;
   |             ----------- `commit_hash` defined here
...
11 |             commit_hash = commit_hash();
   |                           ^^^^^^^^^^^^^ not a function
help: `commit_hash` is a unit variant, you need to write it without the parenthesis
   |
11 |             commit_hash = commit_hash;
   |                           ^^^^^^^^^^^
error: aborting due to previous error

First, the message talks about "enum variant", does it mean struct variant?
Second, I don't get why it does not compile anyway.
If I rename commit_hash() to get_commit_hash() it builds, but why can't it figure out that that a var and function are different things even if they have the same name?

Fun fact:
this doesn't build either

    pub fn new() -> VersionInfo {
        let commit_hash: Option<String>;
        commit_hash = commit_hash();

        VersionInfo {
            commit_hash,
        }
    }

but this does:

    pub fn new() -> VersionInfo {
        let commit_hash: Option<String> = commit_hash();

        VersionInfo {
            commit_hash,
        }
    }

Shouldn't the 2 snippets behave identical?

[estebank]

Shouldn't the 2 snippets behave identical?

They are not because on the second case the local binding commit_hash doesn't exist yet, so the mod level commit_hash function is not yet shadowed. In the other case, the function commit_hash has been shadowed by the local binding, so it fails to compile.

First, the message talks about "enum variant", does it mean struct variant?

No, it's just confused thinking that commit_variant is Option::None.

---

The error message should mention the shadowing of the function.

[matthiaskrgr]

Just ran into this again with a more simple case :(

fn a() {}

fn main() {
    let a: bool = false;
    if a {
        a();
    }
}

IMO this should compile because we know that fn a() is of type Fn .. and not bool so if a querying the let a variable is the only thing that makes sense here..?

The error message is not really helping imo

error[E0618]: expected function, found `bool`
 --> src/main.rs:7:9
  |
5 |     let a: bool = false;
  |         - `a` has type `bool`
6 |     if a {
7 |         a();
  |         ^--
  |         |
  |         call expression requires function

I wonder if type ascription could solve this:
if a: bool {