Improve error reporting: override method does not match abstract member

[anton-pt]

What

When overriding an abstract member like this:

type Base() =
    abstract member Member: int * string -> string
    default x.Member (i, s) = s

type Derived1() =
    inherit Base()
    override x.Member() = 5

type Derived2() =
    inherit Base()
    override x.Member (i : int) = "Hello"

type Derived3() =
    inherit Base()
    override x.Member (s : string, i : int) = sprintf "Hello %s" s

FSI yields the error message
error FS0856: This override takes a different number of arguments to the corresponding abstract member
for the definitions in Derived1 and Derived2 and
error FS0001: This expression was expected to have type int but here has type string
for the definition in Derived3.

Why

The error message does not suggest the correct signature of the abstract methods so you don't know if you have them in the right order, etc. This can be quite a pain when inheriting from a class with a lot of members (such as a WPF Window) and trying to find the right overload.

How

In all 3 cases above, the error message should include the full type signature(s) for Member (including any overloads).

Bonus round

It would also be great to provide suggestions for members which can be overridden if the programmer has a typo in the method name, such as:

type Derived4() =
    inherit Base()
    override x.Memer (i, s) = sprintf "Hello %d" i

This currently produces the error:
error FS0855: No abstract or interface member was found that corresponds to this override

[forki]

WIP PR at #1950

[isaacabraham]

@forki can this be closed?

[forki]

Yep Am 20.01.2017 16:35 schrieb "Isaac Abraham" <notifications@github.com>:

…

@forki <https://github.com/forki> can this be closed? — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <#1430 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AADgNMjrNF_IGBAZhtpsFrdLVw_6m-xWks5rUNRCgaJpZM4Jjpoh> .