Forgetting to call a variant constructor causes a confusing error message

[arielb1]

STR

struct Foo(u32);

fn test() -> Foo { Foo }

fn main() {
}

Confusing result

error[E0308]: mismatched types
 --> <anon>:3:20
  |
3 | fn test() -> Foo { Foo }
  |                    ^^^ expected struct `Foo`, found fn item
  |
  = note: expected type `Foo`
  = note:    found type `fn(u32) -> Foo {Foo::{{constructor}}}`

[arielb1]

The error message mentions function items, which is confusing to new users.

[estebank]

non-fn-like structs have better output, we should perform the same for fn-like structs:

error[E0423]: expected value, found struct `Bar`
 --> src/main.rs:9:21
  |
9 | fn test2() -> Bar { Bar }
  |                     ^^^ did you mean `Bar { /* fields */ }`?

[estebank]

Mentoring instructions:

In note_type_err, check wether values can be decomposed into Some(ValuePairs::Types(exp_found). If it can, check wether exp_found.found is a TypeVariant::TyFnPtr(_) with an FnSig.output() == exp_found.expected. If that is the case, add a note to the diag like for E-423.