Unable to compute `limit()` over a variable coming from a list

[maxale]

Steps To Reproduce

Consider an example:

sage: x = var('x',n=3)
sage: f = sum(x); f
x0 + x1 + x2
sage: f.limit(x[1]=1)
  Cell In[3], line 1
    f.limit(x[Integer(1)]=Integer(1))
            ^
SyntaxError: expression cannot contain assignment, perhaps you meant "=="?

sage: f.limit(x[1]==1)
[...]
ValueError: call the limit function like this, e.g. limit(expr, x=2).

Expected Behavior

It should be possible to computing limit without confusing its argument with an assignment. It'd would be much safer to have an interface like .limit(x[1], 1), where the variable and its value are separated.

Actual Behavior

Sage thinks x[1]=1 is an assignment and gives an error.

Additional Information

I was able to compute the limit via the following very roundabout way:

sage: f.limit(**{str(x[1]):1})
x0 + x2 + 1

Environment

• OS: Ubuntu 24.04.1 LTS
• Sage Version: 10.5.beta6

Checklist

• I have searched the existing issues for a bug report that matches the one I want to file, without success.
• I have read the documentation and troubleshoot guide