cmd/pprof: graphviz node names are funny with generics

[bradfitz]

Go 1.18.3.

Not sure what I expect when I use `go tool pprof's web mode to see the graphviz SVG output on a node using generics, but not this:

Either without the newlines, or with the concrete types (if/when available)?

FWIW, that's from:

// Set populates an entry in a map, making the map if necessary.
//
// That is, it assigns (*m)[k] = v, making *m if it was nil.
func Set[K comparable, V any, T ~map[K]V](m *T, k K, v V) {
	if *m == nil {
		*m = make(map[K]V)
	}
	(*m)[k] = v
}

[prattmic]

I wonder if google/pprof#689 will address this. I’m skeptical though, as bad escaping should most likely cause parse errors.

[prattmic]

No, this seems to be different.

In pprof, the type name is main.Set[...] in my test (your package is named mak, right?). pprof or dot (not sure where this lives) replaces . with a newline to separate the package and symbol name onto different lines. This seems to be getting caught up in that rule.

[prattmic]

There is an even worse case with pkg.(*T[...]).f turning into pkg..f, even in the text view. Both of these are covered by google/pprof#705.

[prattmic]

Fix in google/pprof#717

[gopherbot]

Change https://go.dev/cl/420234 mentions this issue: cmd: vendor github.com/google/pprof to fix mangled type parameter symbol names

[odeke-em]

Thank you for filing this bug @bradfitz and for the quick response and fix @prattmic! I think fixing this for Go1.19 is useful as it is just updating the dependency. I have sent a CL vendoring the fix in https://go-review.googlesource.com/c/go/+/420234. @ianlancetaylor @rsc can I kindly implore you to let this fly in the Go1.19 release :-) or perhaps should we wait until the next point release and also backport too?