struct initialization incorrectly suggests using assoc function

[lcnr]

Code

struct Foo {
    field: u32,
}

impl Foo {
    fn field(&self) -> u32 {
        self.field
    }

    fn new() -> Foo {
        Foo { field }
    }
}

Current output

error[E0425]: cannot find value `field` in this scope
  --> src/lib.rs:11:15
   |
11 |         Foo { field }
   |               ^^^^^ a field by this name exists in `Self`
   |
help: consider using the associated function
   |
11 |         Foo { self.field }
   |               +++++

We should not suggest using self.field inside of a struct initializer.

[compiler-errors]

This is two problems:

1. field -> self.field breaks the field initializer shorthand
2. We shouldn't suggest self. unless we know this is call expr.

(2.) happens even without initializers:

struct Foo {
    field: u32,
}

impl Foo {
    fn field(&self) -> u32 {
        self.field
    }

    fn new() {
        field;
    }
}

error[[E0425]](https://doc.rust-lang.org/stable/error_codes/E0425.html): cannot find value `field` in this scope
  --> src/lib.rs:11:9
   |
11 |         field;
   |         ^^^^^ a field by this name exists in `Self`
   |
help: consider using the associated function
   |
11 |         self.field;
   |         +++++