Should methods of including objects have the same parameter names as those of an included object?

[MaryamZi]

Description:
jBallerina currently disallows the following since the name of the parameter is different.

type Config object {
    function get(string k) returns anydata;
};

class ConfigImpl {
    *Config;

    function get(string key) returns anydata { // `key` instead of `k` as parameter name

    }
}

But I'm not sure if the spec requires this? (These may be due to checks left over from an older implementation).

The spec only says

A type-reference to a class is treated as a reference to the class's type; only the types of the methods and fields are copied from the referenced type. An object-field-descriptor or method-decl in a object-type-descriptor can override respectively an object-field-descriptor or method-decl of the same name in an included object-type-descriptor, provided the type declared for the field or method in the overriding descriptor is a subtype of the type declared in the overridden descriptor. An object-field-descriptor cannot override a method-decl, nor can a method-decl override an object-field-descriptor. It is an error if an object-type-descriptor has two or more object-type-inclusions that include an object-field-descriptor with the same name, unless those object-field-descriptors are overridden by an object-field-descriptor in the including object-type-descriptor. It is an error if an object-type-descriptor has two or more object-type-inclusions that include method-decls with the same name but different function-signatures, unless those method-decls are overridden by a method-decl in the including object-type-descriptor.

In general, of course we do not consider the names of parameters for typing, and this particular case is disallowed via an additional check for object type inclusion.

The following are allowed (as expected).

type Config record {
    function (string k) returns anydata get;
};

type ConfigImpl record {
    *Config;
    // overrding like this is allowed since it is a subtype of `get` from `Config`
    function (string key) returns anydata get;
};

function get(string key) returns anydata {

}

function (string k) returns anydata getFunc = get;

Related issues:

• Clarification on multiple object type inclusions with the same method signature #1230, When are two function signatures the same? #1234, but for a wider set of conditions and multiple inclusions
• Should object method param names be equal in declaration and definition? #124

[jclark]

I don't think the spec requires the parameter names to be the same.

[MaryamZi]

Thank you, we will get rid of this restriction in jBallerina.