Fixed index out of range error

Author: mikefarah

go.mod

@@ -30,5 +30,6 @@ require (
 	golang.org/x/xerrors v0.0.0-20220907171357-04be3eba64a2 // indirect
 )
 
-go 1.21
+go 1.21.0
+
 toolchain go1.22.5

pkg/yqlib/expression_parser_test.go

@@ -11,6 +11,11 @@ func getExpressionParser() ExpressionParserInterface {
 	return ExpressionParser
 }
 
+func TestParserCreateMapColonOnItsOwn(t *testing.T) {
+	_, err := getExpressionParser().ParseExpression(":")
+	test.AssertResultComplex(t, "':' expects 2 args but there is 0", err.Error())
+}
+
 func TestParserNoMatchingCloseBracket(t *testing.T) {
 	_, err := getExpressionParser().ParseExpression(".cat | with(.;.bob")
 	test.AssertResultComplex(t, "bad expression - probably missing close bracket on WITH", err.Error())

pkg/yqlib/lexer.go

@@ -126,7 +126,7 @@ func handleToken(tokens []*token, index int, postProcessedTokens []*token) (toke
 	if tokenIsOpType(currentToken, createMapOpType) {
 		log.Debugf("tokenIsOpType: createMapOpType")
 		// check the previous token is '[', means we are slice, but dont have a first number
-		if tokens[index-1].TokenType == traverseArrayCollect {
+		if index > 0 && tokens[index-1].TokenType == traverseArrayCollect {
 			log.Debugf("previous token is : traverseArrayOpType")
 			// need to put the number 0 before this token, as that is implied
 			postProcessedTokens = append(postProcessedTokens, &token{TokenType: operationToken, Operation: createValueOperation(0, "0")})