Summary

Given a statement like:

result = (
    f(111111111111111111111111111111111111111111111111111111111111111111111111111111111)
    + 1
)()

When we go to parenthesize the target of the assignment, we use maybe_parenthesize_expression with Parenthesize::IfBreaks. This then checks if the call on the right-hand side needs to be parenthesized, the implementation of which looks like:

impl NeedsParentheses for ExprCall {
    fn needs_parentheses(
        &self,
        _parent: AnyNodeRef,
        context: &PyFormatContext,
    ) -> OptionalParentheses {
        if CallChainLayout::from_expression(self.into(), context.source())
            == CallChainLayout::Fluent
        {
            OptionalParentheses::Multiline
        } else if context.comments().has_dangling(self) {
            OptionalParentheses::Always
        } else {
            self.func.needs_parentheses(self.into(), context)
        }
    }
}

Checking for self.func.needs_parentheses(self.into(), context) is problematic, since, as in the example above, self.func may already be parenthesized -- in which case, we don't want to parenthesize the entire expression. If we do, we end up with this non-ideal formatting:

result = (
    (
        f(
            111111111111111111111111111111111111111111111111111111111111111111111111111111111
        )
        + 1
    )()
)

This PR modifies the NeedsParentheses implementations for call chain expressions to return Never if the inner expression has its own parentheses, in which case, the formatting implementations for those expressions will preserve them anyway.

Closes #7370.

Test Plan

Zulip improves a bit, everything else is unchanged.

Before:

After: