tree-wide: Audit panic error messages

These shouldn't happen, but if they do, then let's make it easier to
debug.

1 files changed, 9 insertions, 9 deletions

diff --git a/decode.go b/decode.go
index 976cc6a..1ff8938 100644
--- a/decode.go
+++ b/decode.go
@@ -209,7 +209,7 @@ func (dec *Decoder) DecodeThenEOF(ptr any) (err error) {
 	}
 	c, s, t, _ := dec.io.ReadRuneType()
 	if t != jsonparse.RuneTypeEOF {
-		panic("should not happen")
+		panic(fmt.Errorf("should not happen: .ReadRuneType returned non-EOF after decode without .Reset being called: %v", t))
 	}
 	if s > 0 {
 		return &DecodeError{
@@ -283,7 +283,7 @@ func (dec *Decoder) unreadRune() {
 	if err := dec.io.UnreadRune(); err != nil {
 		// .UnreadRune() must succeed if the previous call was
 		// .ReadRune(), which it always is for this code.
-		panic("should not happen")
+		panic(fmt.Errorf("should not happen: UnreadRune: %w", err))
 	}
 }
 
@@ -302,7 +302,7 @@ func (dec *Decoder) expectRune(ec rune, et jsonparse.RuneType) *DecodeError {
 		return err
 	}
 	if ac != ec || at != et {
-		panic("should not happen")
+		panic(fmt.Errorf("should not happen: expected %q/%v but got %q/%v", ec, et, ac, at))
 	}
 	return nil
 }
@@ -964,7 +964,7 @@ func (dec *Decoder) decodeAny() (any, *DecodeError) {
 	case jsonparse.RuneTypeNullN:
 		return nil, dec.decodeNull()
 	default:
-		panic("should not happen")
+		panic(fmt.Errorf("should not happen: unexpected runeType at beginning of value: %v", t))
 	}
 }
 
@@ -1061,10 +1061,10 @@ func (dec *Decoder) decodeObject(gTyp reflect.Type, decodeKey, decodeVal func()
 		case jsonparse.RuneTypeObjectEnd:
 			return nil
 		default:
-			panic("should not happen")
+			panic(fmt.Errorf("should not happen: unexpected runeType after k/v pair in object: %v", t))
 		}
 	default:
-		panic("should not happen")
+		panic(fmt.Errorf("should not happen: unexpected runeType after opening '{' of object: %v", t))
 	}
 }
 
@@ -1136,7 +1136,7 @@ func (dec *Decoder) decodeArray(gTyp reflect.Type, decodeMember func() *DecodeEr
 		case jsonparse.RuneTypeArrayEnd:
 			return nil
 		default:
-			panic("should not happen")
+			panic(fmt.Errorf("should not happen: unexpected runeType after array item: %v", t))
 		}
 	}
 }
@@ -1175,7 +1175,7 @@ func (dec *Decoder) decodeString(gTyp reflect.Type, out fastio.RuneWriter) *Deco
 			case 't':
 				_, _ = out.WriteRune('\t')
 			default:
-				panic("should not happen")
+				panic(fmt.Errorf("should not happen: unexpected rune after backslash: %q", c))
 			}
 		case jsonparse.RuneTypeStringEscUA:
 			uhex[0], _ = jsonparse.HexToInt(c)
@@ -1253,7 +1253,7 @@ func (dec *Decoder) decodeString(gTyp reflect.Type, out fastio.RuneWriter) *Deco
 		case jsonparse.RuneTypeStringEnd:
 			return nil
 		default:
-			panic("should not happen")
+			panic(fmt.Errorf("should not happen: unexpected runeType in string: %v", t))
 		}
 	}
 }