Internal error for dynamic argument

[Charles]

The program below works in Cobra 0.9.3, but not 0.9.4:

class X

    def foo(c as char)
        pass

    def foo(s as String)
        pass

    def foo(obj as Object)
        pass

    def main
        x = 'aoeu' to dynamic
        .foo(x)

changeset:2966 from ticket:189 caused the change

Commenting out this code in Expr.cobra (around line 752) will allow the above program to compile and run without error:

                            /#
                            if winner inherits BoxMember # .no-warnings.
                                # to-do: 2012-07-01 CE: the following just isn't ready
                                if winner.name not in ['format', 'invoke', 'split', 'sort']  # to-do: hack
                                    params = winner.params
                                    if _checkParamsCount(winner, args, params)
                                        if needInferOutArgs, _inferOutArgs(args, params, false) 
                                        _checkArgsAssignable(winner, args, params)
                            #/

[hopscc]

The cause is actually in _checkArgsAssignable where the contextType field is updated after determining the arg is assignable to the parameterType (about line 940-ish).

The root cause is a poor choice for the best overloaded method (and the use of a dynamic arg).

Though to be fair it would be an edge case optimisation on work on ticket:130/ticket:321 to choose the correct overload in the first case.

Program Source code corrections include changing the order of the overloaded methods OR explicitly casting the arg to disambiguate the overload needed.

The compiler code prior to the current setting contextType for this case compiled so it would be reasonable to fallback to that for this case (Overloaded method with dynamic arg(s))
but a more general fix may be to just determine that the combination is inherently
error prone to auto resolve and emit a warning...
A subsequent failure would then indicate that some more code hinting ( per the warning) is needed.

I have a fix (as per the first option above) just waiting for tests..

[hopscc]

Patch to not update contextType on BoxMembers that are both overloads and have args with dynamic types.
Above failing program as new test

[Charles]

Regarding the patch, we'll see if this sticks or not:

                if defnIsOverload and arg.type.nonNil inherits DynamicType 
                        pass 
                else 
                        arg.contextType = param.type 

The whole point of setting the .contextType is that most of the time it is necessary. We might get away without it though if we switch to C# dynamic.

[hopscc]

prior to changeset:2966 it wasnt passing through that code at all (and presumably wasnt setting contextType for any overloads) so its probably not necessary for them..
With the above its setting them for overloads except those that have dynamic args

[Charles]

changeset:2986