Fix line stepping in debugger.

[vadimcn]

Attribute drop code to block's closing brace, instead of the line where the allocation was done.
Attribute function epilogues to function body's closing brace, rather than the function header.

Fixes#37032

r? @michaelwoerister

[vadimcn]

I've opted to ignore the fact that span.lo actually points after the brace, because doing it "correctly" would require analyzing codemap for multibyte characters (as you pointed out on IRC). Which is costly, and brings zero benefit: a brace is always followed by \n at the minimum, so the line number will be correct, which is all a debugger cares for. The only exception to that is when a brace is the last character in a file, but somehow this case also seems to work correctly.

[arielb1]

Multibyte characters? Isn't a brace always a single-byte character?

[michaelwoerister]

@arielb1 Yes, but not all scopes end with braces :)

a brace is always followed by \n at the minimum, so the line number will be correct

That's an interesting observation! From what you've written I assume you've tried it out in the debugger?

[michaelwoerister]

From what you've written I assume you've tried it out in the debugger?

The test case covers the interesting cases, I think.

[michaelwoerister]

@bors r+

[bors]

📌 Commit 209fe0d has been approved by michaelwoerister

[bors]

⌛ Testing commit 209fe0d with merge 0eb4d46...

[michaelwoerister]

🎉
Thanks again for the awesome PR, @vadimcn !

[bors]

☀️ Test successful - auto-linux-32-nopt-t, auto-linux-32-opt, auto-linux-64-cargotest, auto-linux-64-cross-freebsd, auto-linux-64-debug-opt, auto-linux-64-nopt-t, auto-linux-64-opt, auto-linux-64-opt-rustbuild, auto-linux-64-x-android-t, auto-linux-cross-opt, auto-linux-musl-64-opt, auto-mac-32-opt, auto-mac-64-opt, auto-mac-64-opt-rustbuild, auto-mac-cross-ios-opt, auto-win-gnu-32-opt, auto-win-gnu-32-opt-rustbuild, auto-win-gnu-64-opt, auto-win-msvc-32-opt, auto-win-msvc-64-cargotest, auto-win-msvc-64-opt, auto-win-msvc-64-opt-rustbuild
Approved by: michaelwoerister
Pushing 0eb4d46 to master...