slices: refactor DeleteFunc to improve code readability

Reuse IndexFunc function to avoid confusing subscript indexing, and to reduce code nesting depth.

Change-Id: I309416ebf928071f71054433e078f0fda802fba8
GitHub-Last-Rev: af54738bda
GitHub-Pull-Request: golang/go#61154
Reviewed-on: https://go-review.googlesource.com/c/go/+/507635
Run-TryBot: Ian Lance Taylor <iant@golang.org>
Auto-Submit: Ian Lance Taylor <iant@google.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
Run-TryBot: Ian Lance Taylor <iant@google.com>
Reviewed-by: Heschi Kreinick <heschi@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>

src/slices/slices.go

@@ -228,21 +228,18 @@ func Delete[S ~[]E, E any](s S, i, j int) S {
 // zeroing those elements so that objects they reference can be garbage
 // collected.
 func DeleteFunc[S ~[]E, E any](s S, del func(E) bool) S {
-	// Don't start copying elements until we find one to delete.
-	for i, v := range s {
-		if del(v) {
-			j := i
-			for i++; i < len(s); i++ {
-				v = s[i]
-				if !del(v) {
-					s[j] = v
-					j++
-				}
-			}
-			return s[:j]
-		}
-	}
+	i := IndexFunc(s, del)
+	if i == -1 {
 		return s
+	}
+	// Don't start copying elements until we find one to delete.
+	for j := i + 1; j < len(s); j++ {
+		if v := s[j]; !del(v) {
+			s[i] = v
+			i++
+		}
+	}
+	return s[:i]
 }
 
 // Replace replaces the elements s[i:j] by the given v, and returns the