span: make frontierHeap type-safe

This patch makes `frontierHeap` type-safe by replacing the usage of the
go standard library heap package with the cockroach copy of the heap
package that uses generics.

Release note: None

Author: andyyang890

pkg/util/span/BUILD.bazel

@@ -15,6 +15,7 @@ go_library(
         "//pkg/keys",
         "//pkg/roachpb",
         "//pkg/util/buildutil",
+        "//pkg/util/container/heap",
         "//pkg/util/hlc",
         "//pkg/util/interval",
         "//pkg/util/syncutil",
@@ -34,6 +35,7 @@ go_test(
     embed = [":span"],
     deps = [
         "//pkg/roachpb",
+        "//pkg/util/container/heap",
         "//pkg/util/hlc",
         "//pkg/util/leaktest",
         "//pkg/util/log",

pkg/util/span/frontier.go

@@ -6,7 +6,6 @@
 package span
 
 import (
-	"container/heap"
 	"fmt"
 	"iter"
 	"strings"
@@ -17,6 +16,7 @@ import (
 	_ "github.com/cockroachdb/cockroach/pkg/keys"
 	"github.com/cockroachdb/cockroach/pkg/roachpb"
 	"github.com/cockroachdb/cockroach/pkg/util/buildutil"
+	"github.com/cockroachdb/cockroach/pkg/util/container/heap"
 	"github.com/cockroachdb/cockroach/pkg/util/hlc"
 	"github.com/cockroachdb/cockroach/pkg/util/interval"
 	"github.com/cockroachdb/cockroach/pkg/util/syncutil"
@@ -135,6 +135,8 @@ type btreeFrontier struct {
 	disallowMutationWhileIterating atomic.Bool
 }
 
+var _ Frontier = (*btreeFrontier)(nil)
+
 // btreeFrontierEntry represents a timestamped span. It is used as the nodes in both
 // the tree and heap needed to keep the Frontier.
 // btreeFrontierEntry implements interval/generic interface.
@@ -652,6 +654,8 @@ func (e *btreeFrontierEntry) isEmptyRange() bool {
 // of the heap.
 type frontierHeap []*btreeFrontierEntry
 
+var _ heap.Interface[*btreeFrontierEntry] = (*frontierHeap)(nil)
+
 // Len implements heap.Interface.
 func (h frontierHeap) Len() int { return len(h) }
 
@@ -670,15 +674,14 @@ func (h frontierHeap) Swap(i, j int) {
 }
 
 // Push implements heap.Interface.
-func (h *frontierHeap) Push(x interface{}) {
+func (h *frontierHeap) Push(x *btreeFrontierEntry) {
 	n := len(*h)
-	entry := x.(*btreeFrontierEntry)
-	entry.heapIdx = n
-	*h = append(*h, entry)
+	x.heapIdx = n
+	*h = append(*h, x)
 }
 
 // Pop implements heap.Interface.
-func (h *frontierHeap) Pop() interface{} {
+func (h *frontierHeap) Pop() *btreeFrontierEntry {
 	old := *h
 	n := len(old)
 	entry := old[n-1]

pkg/util/span/frontier_test.go

@@ -6,14 +6,14 @@
 package span
 
 import (
-	"container/heap"
 	"context"
 	"fmt"
 	"math/rand"
 	"strings"
 	"testing"
 
 	"github.com/cockroachdb/cockroach/pkg/roachpb"
+	"github.com/cockroachdb/cockroach/pkg/util/container/heap"
 	"github.com/cockroachdb/cockroach/pkg/util/hlc"
 	"github.com/cockroachdb/cockroach/pkg/util/leaktest"
 	"github.com/cockroachdb/cockroach/pkg/util/log"