This is an automated cherry-pick of pingcap#50146

Signed-off-by: ti-chi-bot <ti-community-prow-bot@tidb.io>

expression/builtin_cast.go

@@ -2254,6 +2254,10 @@ func WrapWithCastAsString(ctx sessionctx.Context, expr Expression) Expression {
 		charset, collate := expr.CharsetAndCollation()
 		tp.SetCharset(charset)
 		tp.SetCollate(collate)
+	} else if exprTp.GetType() == mysql.TypeBit {
+		// Implicitly casting BIT to string will make it a binary
+		tp.SetCharset(charset.CharsetBin)
+		tp.SetCollate(charset.CollationBin)
 	} else {
 		charset, collate := ctx.GetSessionVars().GetCharsetInfo()
 		tp.SetCharset(charset)

expression/builtin_string.go

@@ -768,7 +768,7 @@ func (c *reverseFunctionClass) getFunction(ctx sessionctx.Context, args []Expres
 	bf.tp.SetFlen(args[0].GetType().GetFlen())
 	addBinFlag(bf.tp)
 	var sig builtinFunc
-	if types.IsBinaryStr(argTp) {
+	if types.IsBinaryStr(argTp) || types.IsTypeBit(argTp) {
 		sig = &builtinReverseSig{bf}
 		sig.setPbCode(tipb.ScalarFuncSig_Reverse)
 	} else {

expression/collation.go

@@ -177,6 +177,8 @@ func deriveCoercibilityForColumn(c *Column) Coercibility {
 	// For specified type null, it should return CoercibilityIgnorable, which means it got the lowest priority in DeriveCollationFromExprs.
 	if c.RetType.GetType() == mysql.TypeNull {
 		return CoercibilityIgnorable
+	} else if types.IsTypeBit(c.RetType) {
+		return CoercibilityImplicit
 	}
 
 	switch c.RetType.EvalType() {
@@ -374,6 +376,8 @@ func inferCollation(exprs ...Expression) *ExprCollation {
 	dstCharset, dstCollation := exprs[0].GetType().GetCharset(), exprs[0].GetType().GetCollate()
 	if exprs[0].GetType().EvalType() == types.ETJson {
 		dstCharset, dstCollation = charset.CharsetUTF8MB4, charset.CollationUTF8MB4
+	} else if types.IsTypeBit(exprs[0].GetType()) {
+		dstCharset, dstCollation = charset.CharsetBin, charset.CollationBin
 	}
 	unknownCS := false
 
@@ -384,6 +388,8 @@ func inferCollation(exprs ...Expression) *ExprCollation {
 		// see details https://github.com/pingcap/tidb/issues/31320#issuecomment-1010599311
 		if arg.GetType().EvalType() == types.ETJson {
 			argCharset, argCollation = charset.CharsetUTF8MB4, charset.CollationUTF8MB4
+		} else if types.IsTypeBit(arg.GetType()) {
+			argCharset, argCollation = charset.CharsetBin, charset.CollationBin
 		}
 		// If one of the arguments is binary charset, we allow it can be used with other charsets.
 		// If they have the same coercibility, let the binary charset one to be the winner because binary has more precedence.