runtime: don't duplicate reraised panic values in printpanics

Change the output printed when crashing with a reraised panic value
to not duplicate that value.

Changes output of panicking with "PANIC", recovering, and reraising
from:

  panic: PANIC [recovered]
    panic: PANIC

to:

  panic: PANIC [recovered, reraised]

Fixes #71517

Change-Id: Id59938c4ea0df555b851ffc650fe6f94c0845499
Reviewed-on: https://go-review.googlesource.com/c/go/+/645916
Reviewed-by: Michael Knyszek <mknyszek@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>

1 files changed, 52 insertions, 0 deletions

diff --git a/src/runtime/testdata/testprog/crash.go b/src/runtime/testdata/testprog/crash.go
index bdc395f652..56dd701ffb 100644
--- a/src/runtime/testdata/testprog/crash.go
+++ b/src/runtime/testdata/testprog/crash.go
@@ -19,6 +19,9 @@ func init() {
 	register("StringPanic", StringPanic)
 	register("NilPanic", NilPanic)
 	register("CircularPanic", CircularPanic)
+	register("ReraisedPanic", ReraisedPanic)
+	register("ReraisedMiddlePanic", ReraisedMiddlePanic)
+	register("ReraisedPanicSandwich", ReraisedPanicSandwich)
 }
 
 func test(name string) {
@@ -137,3 +140,52 @@ func (e exampleCircleEndError) Error() string {
 func CircularPanic() {
 	panic(exampleCircleStartError{})
 }
+
+func ReraisedPanic() {
+	defer func() {
+		panic(recover())
+	}()
+	panic("message")
+}
+
+func ReraisedMiddlePanic() {
+	defer func() {
+		recover()
+		panic("outer")
+	}()
+	func() {
+		defer func() {
+			panic(recover())
+		}()
+		func() {
+			defer func() {
+				recover()
+				panic("middle")
+			}()
+			panic("inner")
+		}()
+	}()
+}
+
+// Panic sandwich:
+//
+//	panic("outer") =>
+//	recovered, panic("inner") =>
+//	panic(recovered outer panic value)
+//
+// Exercises the edge case where we reraise a panic value,
+// but with another panic in the middle.
+func ReraisedPanicSandwich() {
+	var outer any
+	defer func() {
+		recover()
+		panic(outer)
+	}()
+	func() {
+		defer func() {
+			outer = recover()
+			panic("inner")
+		}()
+		panic("outer")
+	}()
+}