runtime: fix iterator returns map entries after clear (pre-swissmap)

Fixes #70189
Fixes #59411

Cq-Include-Trybots: luci.golang.try:gotip-linux-amd64-longtest-noswissmap
Change-Id: I4ef7ecd7e996330189309cb2a658cf34bf9e1119
Reviewed-on: https://go-review.googlesource.com/c/go/+/625275
Reviewed-by: Keith Randall <khr@golang.org>
Reviewed-by: Keith Randall <khr@google.com>
Auto-Submit: Keith Randall <khr@golang.org>
Reviewed-by: Michael Pratt <mpratt@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>

1 files changed, 38 insertions, 0 deletions

diff --git a/test/fixedbugs/issue70189.go b/test/fixedbugs/issue70189.go
new file mode 100644
index 0000000000..357ac537ad
--- /dev/null
+++ b/test/fixedbugs/issue70189.go
@@ -0,0 +1,38 @@
+// run -goexperiment noswissmap
+
+// Copyright 2024 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+func nan() float64 {
+	var x, y float64
+	return x / y
+}
+
+func main() {
+	m := map[float64]int{}
+
+	// Make a small map with nan keys
+	for i := 0; i < 8; i++ {
+		m[nan()] = i
+	}
+
+	// Start iterating on it.
+	start := true
+	for _, v := range m {
+		if start {
+			// Add some more elements.
+			for i := 0; i < 10; i++ {
+				m[float64(i)] = i
+			}
+			// Now clear the map.
+			clear(m)
+			start = false
+		} else {
+			// We should never reach here.
+			panic(v)
+		}
+	}
+}