Fix inconsistent symbol mangling with -Zverbose

[tmiasko]

Always skip arguments that are the defaults of their respective
parameters, to avoid generating inconsistent symbols for builds
with -Zverbose flag and without it.

[rust-highfive]

r? @Mark-Simulacrum

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[tmiasko]

This removes printing of arguments equal to defaults introduced in #92191@jackh726. I could make this customizable, if this is something you find useful, but if not I would prefer to just remove it.

[jackh726]

I don't remember what exactly prompted me to add this; I think it was when I was looking through the logs and was a bit confused with what was happening (though IIRC I was confused about the wrong this).

Regardless, it's a bit unfortunate that symbol mangling and printing are so linked. I would expect that we shouldn't have to worry too much about -Z verbose printing; lifetimes, for example, are much different.

I don't feel strongly one way or the other on removing this with or without adding an alternative. When I'm combing through logs for something, I almost always enable -Z verbose, and I probably wouldn't think to enable something else too.

[Mark-Simulacrum]

I agree that it seems unfortunate logs and symbols are so tightly tied together, but ultimately not really related to this particular PR.

I'm inclined to r+ this and if a strong use case comes along for emitting the defaults we can do so in the future, perhaps gated on a flag that is more obviously crate-graph-wide necessary (or fix the symbol mangling to not be affected).

@bors r+ rollup

[bors]

📌 Commit 3158372 has been approved by Mark-Simulacrum