From d8a66ffc3907f1fa6d67dcc65f2d688c8b27b71c Mon Sep 17 00:00:00 2001
From: Luke Shumaker <lukeshu@lukeshu.com>
Date: Thu, 23 Feb 2023 18:18:53 -0700
Subject: =?UTF-8?q?decode:=20Rename=20expectRune=E2=86=92expectRuneOrPanic?=
 =?UTF-8?q?,=20add=20a=20doc=20comment?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 decode.go | 38 ++++++++++++++++++++++----------------
 1 file changed, 22 insertions(+), 16 deletions(-)

diff --git a/decode.go b/decode.go
index a136668..10b3685 100644
--- a/decode.go
+++ b/decode.go
@@ -296,7 +296,13 @@ func (dec *Decoder) peekRuneType() (jsonparse.RuneType, *DecodeError) {
 	return t, nil
 }
 
-func (dec *Decoder) expectRune(ec rune, et jsonparse.RuneType) *DecodeError {
+// expectRuneOrPanic is for when you *know* what the next
+// non-whitespace rune is going to be; for it to be anything else
+// would be a syntax error.  It will return an error for I/O errors
+// and syntax errors, but panic if the result is not what was
+// expected; as that would indicate a bug in the agreement between the
+// parser and the decoder.
+func (dec *Decoder) expectRuneOrPanic(ec rune, et jsonparse.RuneType) *DecodeError {
 	ac, at, err := dec.readRune()
 	if err != nil {
 		return err
@@ -1042,7 +1048,7 @@ func (dec *Decoder) decodeObject(gTyp reflect.Type, decodeKey, decodeVal func()
 		if err := decodeKey(); err != nil {
 			return err
 		}
-		if err := dec.expectRune(':', jsonparse.RuneTypeObjectColon); err != nil {
+		if err := dec.expectRuneOrPanic(':', jsonparse.RuneTypeObjectColon); err != nil {
 			return err
 		}
 		if err := decodeVal(); err != nil {
@@ -1054,7 +1060,7 @@ func (dec *Decoder) decodeObject(gTyp reflect.Type, decodeKey, decodeVal func()
 		}
 		switch t {
 		case jsonparse.RuneTypeObjectComma:
-			if err := dec.expectRune('"', jsonparse.RuneTypeStringBeg); err != nil {
+			if err := dec.expectRuneOrPanic('"', jsonparse.RuneTypeStringBeg); err != nil {
 				return err
 			}
 			goto decodeMember
@@ -1195,7 +1201,7 @@ func (dec *Decoder) decodeString(gTyp reflect.Type, out fastio.RuneWriter) *Deco
 					_, _ = out.WriteRune(utf8.RuneError)
 					break
 				}
-				if err := dec.expectRune('\\', jsonparse.RuneTypeStringEsc); err != nil {
+				if err := dec.expectRuneOrPanic('\\', jsonparse.RuneTypeStringEsc); err != nil {
 					return err
 				}
 				t, err = dec.peekRuneType()
@@ -1206,7 +1212,7 @@ func (dec *Decoder) decodeString(gTyp reflect.Type, out fastio.RuneWriter) *Deco
 					_, _ = out.WriteRune(utf8.RuneError)
 					break
 				}
-				if err := dec.expectRune('u', jsonparse.RuneTypeStringEscU); err != nil {
+				if err := dec.expectRuneOrPanic('u', jsonparse.RuneTypeStringEscU); err != nil {
 					return err
 				}
 
@@ -1255,27 +1261,27 @@ func (dec *Decoder) decodeBool(gTyp reflect.Type) (bool, *DecodeError) {
 	}
 	switch c {
 	case 't':
-		if err := dec.expectRune('r', jsonparse.RuneTypeTrueR); err != nil {
+		if err := dec.expectRuneOrPanic('r', jsonparse.RuneTypeTrueR); err != nil {
 			return false, err
 		}
-		if err := dec.expectRune('u', jsonparse.RuneTypeTrueU); err != nil {
+		if err := dec.expectRuneOrPanic('u', jsonparse.RuneTypeTrueU); err != nil {
 			return false, err
 		}
-		if err := dec.expectRune('e', jsonparse.RuneTypeTrueE); err != nil {
+		if err := dec.expectRuneOrPanic('e', jsonparse.RuneTypeTrueE); err != nil {
 			return false, err
 		}
 		return true, nil
 	case 'f':
-		if err := dec.expectRune('a', jsonparse.RuneTypeFalseA); err != nil {
+		if err := dec.expectRuneOrPanic('a', jsonparse.RuneTypeFalseA); err != nil {
 			return false, err
 		}
-		if err := dec.expectRune('l', jsonparse.RuneTypeFalseL); err != nil {
+		if err := dec.expectRuneOrPanic('l', jsonparse.RuneTypeFalseL); err != nil {
 			return false, err
 		}
-		if err := dec.expectRune('s', jsonparse.RuneTypeFalseS); err != nil {
+		if err := dec.expectRuneOrPanic('s', jsonparse.RuneTypeFalseS); err != nil {
 			return false, err
 		}
-		if err := dec.expectRune('e', jsonparse.RuneTypeFalseE); err != nil {
+		if err := dec.expectRuneOrPanic('e', jsonparse.RuneTypeFalseE); err != nil {
 			return false, err
 		}
 		return false, nil
@@ -1285,16 +1291,16 @@ func (dec *Decoder) decodeBool(gTyp reflect.Type) (bool, *DecodeError) {
 }
 
 func (dec *Decoder) decodeNull() *DecodeError {
-	if err := dec.expectRune('n', jsonparse.RuneTypeNullN); err != nil {
+	if err := dec.expectRuneOrPanic('n', jsonparse.RuneTypeNullN); err != nil {
 		return err
 	}
-	if err := dec.expectRune('u', jsonparse.RuneTypeNullU); err != nil {
+	if err := dec.expectRuneOrPanic('u', jsonparse.RuneTypeNullU); err != nil {
 		return err
 	}
-	if err := dec.expectRune('l', jsonparse.RuneTypeNullL1); err != nil {
+	if err := dec.expectRuneOrPanic('l', jsonparse.RuneTypeNullL1); err != nil {
 		return err
 	}
-	if err := dec.expectRune('l', jsonparse.RuneTypeNullL2); err != nil {
+	if err := dec.expectRuneOrPanic('l', jsonparse.RuneTypeNullL2); err != nil {
 		return err
 	}
 	return nil
-- 
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