[Issue 13517] Only touch .di generated file if changed

[via Digitalmars-d-bugs]

https://issues.dlang.org/show_bug.cgi?id=13517

--- Comment #14 from Ketmar Dark <ketmar at ketmar.no-ip.org> ---
(In reply to Andrei Alexandrescu from comment #13)
> With respect, that's exactly what happens. This is disproportionate response
> to a simple matter.
this proposal leads to increasing complexity of compiler code. and it's for
nothing, actually, 'cause this work can be easily done with external script or
with build tool itself if it's not 'make'.

i'm just strogly against:
1. adding unnecessary code to compiler.
2. turning dmd to half-baked build tool.

> Now consider there's scripting around the build system that only touches
> xyz.di if it has new content.
then we have strange hidden dependency: .di file *seems* to be dependend of .d
file, yet it is clearly older than .d file and somehow it's not regenerated
(why?). so the build tool which relies on timestamps is either confused or the
user need to remember the dependency but don't inform build tool about it.

i see only added complexity here. such complexity is unnecessary for small
projects with small build times, and it can easily turn to complete disaster
with big complex projects (been there, seen that). complex projects *will*
fight with this feature if their build tools are timestamp-based (or build
process will *inevitably* go out of control). and it's really easy to do this
with simple comparison script (ah, just do 'sort' and then calculate md5, for
example).

that's why i'm saying that overal win is close to nothing, but compiler
implementation gains more code.

all in all you aren't convinced me. but your position is clear to me now, so we
can stop arguing and wait for PR. and then let Walter to decide.

sorry for being rude, it was luck of clear understanding from my side.

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