From 2ef7eef1726a6caac2b67ffce538d374a8765373 Mon Sep 17 00:00:00 2001
From: Mauri de Souza Meneguzzo <mauri870@gmail.com>
Date: Sun, 29 Oct 2023 20:51:34 -0300
Subject: [PATCH 1/3] runtime: add missing runtime error prefix to
 PanicNilError

Errors that implement runtime.Error should have a "runtime error: "
prefix, with the solo exception of runtime.plainError (on purpose).

Calling panic(nil) results in a PanicNilError that violates this
constraint.

This CL changes the error from panic(nil) from:

panic called with nil argument

to

runtime error: panic called with nil argument

Fixes #63813
---
 src/runtime/panic.go | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/runtime/panic.go b/src/runtime/panic.go
index 5f54ee4b012d7b..928b75cb7c703f 100644
--- a/src/runtime/panic.go
+++ b/src/runtime/panic.go
@@ -704,7 +704,7 @@ type PanicNilError struct {
 	_ [0]*PanicNilError
 }
 
-func (*PanicNilError) Error() string { return "panic called with nil argument" }
+func (*PanicNilError) Error() string { return "runtime error: panic called with nil argument" }
 func (*PanicNilError) RuntimeError() {}
 
 var panicnil = &godebugInc{name: "panicnil"}

From d04cb4bf67e524bc55a85fbd9ba0a371e45cbb8c Mon Sep 17 00:00:00 2001
From: Mauri de Souza Meneguzzo <mauri870@gmail.com>
Date: Wed, 13 Dec 2023 18:16:26 -0300
Subject: [PATCH 2/3] add test

---
 src/runtime/panic_test.go | 54 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 54 insertions(+)

diff --git a/src/runtime/panic_test.go b/src/runtime/panic_test.go
index b8a300f6b10c20..13b6d5326aacb6 100644
--- a/src/runtime/panic_test.go
+++ b/src/runtime/panic_test.go
@@ -5,6 +5,7 @@
 package runtime_test
 
 import (
+	"runtime"
 	"strings"
 	"testing"
 )
@@ -46,3 +47,56 @@ func TestPanicWithDirectlyPrintableCustomTypes(t *testing.T) {
 		})
 	}
 }
+
+func TestPanicNilErrorPrefix(t *testing.T) {
+	tests := []struct {
+		name      string
+		wantPanic string
+		fn        func()
+	}{
+		{
+			name: "panic(nil)",
+			fn: func() {
+				panic(nil)
+			},
+		},
+		{
+			name: "panic((any)(nil))",
+			fn: func() {
+				var foo any = nil
+				panic(foo)
+			},
+		},
+		{
+			name: "panic((error)(nil))",
+			fn: func() {
+				var err error
+				panic(err)
+			},
+		},
+	}
+
+	for _, tt := range tests {
+		tt := tt
+		t.Run(tt.name, func(t *testing.T) {
+			defer func() {
+				r := recover()
+				if r == nil {
+					t.Fatal("expected a panic")
+				}
+
+				re, ok := r.(runtime.Error)
+				if !ok {
+					t.Fatalf("wrong panic type: got %T, want runtime.Error", r)
+				}
+				got := re.Error()
+				want := "runtime error: panic called with nil argument"
+				if !strings.Contains(got, want) {
+					t.Fatalf("got: %s, want: %s", got, want)
+				}
+			}()
+
+			tt.fn()
+		})
+	}
+}

From 69738780be374af8f410afef9406b57339b959fa Mon Sep 17 00:00:00 2001
From: Mauri de Souza Meneguzzo <mauri870@gmail.com>
Date: Wed, 13 Dec 2023 19:39:45 -0300
Subject: [PATCH 3/3] fix panic test for old issue

---
 test/fixedbugs/issue19658.go | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/test/fixedbugs/issue19658.go b/test/fixedbugs/issue19658.go
index 1e13573b72bc97..7d2dc5ae5cd93b 100644
--- a/test/fixedbugs/issue19658.go
+++ b/test/fixedbugs/issue19658.go
@@ -47,7 +47,7 @@ func main() {
 		Input  string
 		Expect string
 	}{
-		{"", "nil", "panic: panic called with nil argument"},
+		{"", "nil", "panic: runtime error: panic called with nil argument"},
 		{"errors.New", `"test"`, "panic: test"},
 		{"S", "S{}", "panic: s-stringer"},
 		{"byte", "8", "panic: 8"},