go/types, types2: use correct predicate when asserting comma-ok types

While at it and unrelated, up-date testdata/manual.go sample file so
we can just copy its contents into a test file after debugging, without
fixing the date.

Fixes #66878.

Change-Id: Ie49a341b78d99bdc0f1a0ba1ca42fa2d3a807bd6
Reviewed-on: https://go-review.googlesource.com/c/go/+/580075
Auto-Submit: Robert Griesemer <gri@google.com>
Reviewed-by: Robert Griesemer <gri@google.com>
Reviewed-by: Robert Findley <rfindley@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>

1 files changed, 21 insertions, 0 deletions

diff --git a/src/internal/types/testdata/fixedbugs/issue66878.go b/src/internal/types/testdata/fixedbugs/issue66878.go
new file mode 100644
index 0000000000..bd6315f9c3
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue66878.go
@@ -0,0 +1,21 @@
+// 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 p
+
+func _[T bool](ch chan T) {
+	var _, _ T = <-ch
+}
+
+// offending code snippets from issue
+
+func _[T ~bool](ch <-chan T) {
+	var x, ok T = <-ch
+	println(x, ok)
+}
+
+func _[T ~bool](m map[int]T) {
+	var x, ok T = m[0]
+	println(x, ok)
+}