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Having used both Haskell and main stream programming languages I did not at all think that was confusing. The type of "fn foo(x: int) -> string" is quite obviously "fn(x: int) -> string" for people coming from languages like C. I do not see how a colon would make anything more clear. Imagine the function "fn bar(x: fn(x: int) -> string)", would that be more clear with a colon?

On the other hand the enum thing is certainly surprising.

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> Imagine the function "fn bar(x: fn(x: int) -> string)", would that be more clear with a colon?

In your example, why bother naming the inner "x" variable for the function param? It cannot be used on the right-hand-side (definition of "bar"). For that reason, the notation is not exactly "clear". In OCaml the annotation would be:

bar( x : int -> string )

In Rust you can write ```f: fn(i32) -> i32```.

Ocaml's syntax is more consistent, I agree, but its colon operator has different precedence than in Rust, so I am not sure its rational applies to Rust.

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