Update and fix staticcheck

vendor/honnef.co/go/tools/ir/irutil/util.go

@@ -0,0 +1,70 @@
+package irutil
+
+import (
+	"honnef.co/go/tools/ir"
+)
+
+func Reachable(from, to *ir.BasicBlock) bool {
+	if from == to {
+		return true
+	}
+	if from.Dominates(to) {
+		return true
+	}
+
+	found := false
+	Walk(from, func(b *ir.BasicBlock) bool {
+		if b == to {
+			found = true
+			return false
+		}
+		return true
+	})
+	return found
+}
+
+func Walk(b *ir.BasicBlock, fn func(*ir.BasicBlock) bool) {
+	seen := map[*ir.BasicBlock]bool{}
+	wl := []*ir.BasicBlock{b}
+	for len(wl) > 0 {
+		b := wl[len(wl)-1]
+		wl = wl[:len(wl)-1]
+		if seen[b] {
+			continue
+		}
+		seen[b] = true
+		if !fn(b) {
+			continue
+		}
+		wl = append(wl, b.Succs...)
+	}
+}
+
+func Vararg(x *ir.Slice) ([]ir.Value, bool) {
+	var out []ir.Value
+	slice, ok := x.X.(*ir.Alloc)
+	if !ok {
+		return nil, false
+	}
+	for _, ref := range *slice.Referrers() {
+		if ref == x {
+			continue
+		}
+		if ref.Block() != x.Block() {
+			return nil, false
+		}
+		idx, ok := ref.(*ir.IndexAddr)
+		if !ok {
+			return nil, false
+		}
+		if len(*idx.Referrers()) != 1 {
+			return nil, false
+		}
+		store, ok := (*idx.Referrers())[0].(*ir.Store)
+		if !ok {
+			return nil, false
+		}
+		out = append(out, store.Val)
+	}
+	return out, true
+}