[Issue 14742] New: Changing function signatures breaks code

[via Digitalmars-d-bugs]

https://issues.dlang.org/show_bug.cgi?id=14742

          Issue ID: 14742
           Summary: Changing function signatures breaks code
           Product: D
           Version: D2
          Hardware: All
                OS: All
            Status: NEW
          Severity: regression
          Priority: P1
         Component: phobos
          Assignee: nobody at puremagic.com
          Reporter: thecybershadow at gmail.com

This issue is a follow-up to my GitHub comment:

https://github.com/D-Programming-Language/phobos/pull/3422#issuecomment-115654816

Reposting it here so it doesn't get lost:

"""
OK, so this actually broke code for me.

I have a wrapper that wraps arbitrary file operation functions and makes them
atomic (by writing to a temporary file and renaming it onto the target). I use
ParameterTypeTuple to find which parameter contains the "target path" string,
which doesn't work now that the function is a template.

I also had a similar breakage when std.file.copy gained a third optional
parameter. Since the usual way to create a function wrapper (using
ParameterTypeTuple) does not account for optional parameters, the parameter
became non-optional in the wrapped function, which broke code using it.

It seems to me that to truly avoid all breaking changes, we can't touch any
Phobos function signatures at all. This is probably too drastic, so I think we
need to establish some conventions of what breaking changes are acceptable.
"""

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