Syntactic sugar to encourage use of named arguments

Ideas
264
  1. It’s as explicit as you can get. It says, run function f while binding the variable with the name x to the parameter with the name x. Equivalently, it says run runction f while binding the variable x as the argument into the parameter x.
  2. My understand from the PEP is that f(x=) is exactly syntactically equivalent to f(x=x). So that anything that can be done wih the latter can be done with the former.

Type checking example:

def foo(x: float):
    ...

x = "Hello World!"

foo(x=)  # Expected type 'float', got 'str' instead.

Refactoring variable or parameter names is a little tricker. I would expect if I refactor x to be named y in foo that my IDE would do the following:

def foo(y: float):
    ...

x = "Hello World!"

foo(y=x)  # Expected type 'float', got 'str' instead.

and I refactored variable x to z that my IDE would do

def foo(x: float):
    ...

z = "Hello World!"

foo(x=z)  # Expected type 'float', got 'str' instead.

That is, it would detect the breaking of the variable name ↔ parameter name matching required for PEP 736 abbreviation and thus stop doing it.

I wouldn’t be opposed to my tools being able to detect foo(x=x) and suggest I convert it to foo(x=), though I know others would be, so I hope that any tool that makes those suggestions would be configurable to suppress that suggestion.

Here’s an important downside: Right now in my IDE if I have

def foo(x):
    ...

x = 42

foo(x=x)

I can click on the first x in x=x and then hit a hotkey that will jump my cursor to the x in the foo() function definition. I can also click on the second x in x=x and hit a hotkey that will jump my cursor to the x = 42 variable definition (or maybe its last modification? I’m not sure). If PEP 736 is used so that the code becomes foo(x=) it is now ambiguous where the hotkey should send me when I select the x. Perhaps it could treat placing the cursor after the equals sign the same way it used to treat clicking the second x in x=x. In any case, this IDE feature will become slightly less nice with PEP 736 I think.

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