Feature #13979: Ruby doesn't give error on keyword arguments that you can't refer to

• Status: Rejected
• Assignee: -
• Target version: -

[asterite (Ary Borenszweig)]

You can't use keywords as names for normal arguments. For example all of these give a syntax error:

def foo(class); end
def foo(def); end
def foo(if); end
# ... other keywords too

The reason is that there's no way to refer to these names because they are keywords.

However, we can use these names for keyword arguments. All of these work:

def foo(class: 1); end
def foo(def: 1); end
def foo(if: 1); end

But I think they should give a syntax error, because for example I can't refer to the argument "class" in the first line (same reason why the first snippet gives a syntax error).

[nobu (Nobuyoshi Nakada)]

• Description updated (diff)
• Status changed from Open to Rejected

Use Binding#local_variable_get.

[Eregon (Benoit Daloze)]

@nobu (Nobuyoshi Nakada) Is there any value to support such keyword arguments?
I think an early error might be less surprising here.

On the callee side, I think it's a lot more practical to use **keyrest in such a case like keyrest.fetch(:class, 1).

[asterite (Ary Borenszweig)]

Thank you nobu, I didn't know about Binding#local_variable_get

[nobu (Nobuyoshi Nakada)]

Eregon (Benoit Daloze) wrote:

@nobu (Nobuyoshi Nakada) Is there any value to support such keyword arguments?
I think an early error might be less surprising here.

I've heard the example that Rails (maybe ActiveSupport?) had used if: as short for "interface".
Binding#local_variable_get does not encourage to use such arguments.

[ko1 (Koichi Sasada)]

Binding#local_variable_get does not encourage to use such arguments.

But Binding#local_variable_get is introduced for this purpose :p