fix: add test and incorrect assign statement

pkg/dsl/parser/parser.go

@@ -33,6 +33,8 @@ type Parser struct {
 	l *lexer.Lexer
 	// the current token being processed
 	currentToken token.Token
+	// the token before currentToken
+	previousToken token.Token
 	// the next token after currentToken
 	peekToken token.Token
 	// a slice of error messages that are generated during parsing
@@ -82,6 +84,8 @@ func (p *Parser) next() {
 		peek := p.l.NextToken()
 		// if the token is not an ignored token (e.g. whitespace or comments), update the currentToken and peekToken fields and exit the loop
 		if !token.IsIgnores(peek.Type) {
+			// set the previousToken before changing currentToken
+			p.previousToken = p.currentToken
 			// set the currentToken field to the previous peekToken value
 			p.currentToken = p.peekToken
 			// set the peekToken field to the new peek value
@@ -118,6 +122,18 @@ func (p *Parser) currentTokenIs(tokens ...token.Type) bool {
 	return false
 }
 
+// previousTokenIs checks if the Parser's previousToken type is any of the given types
+func (p *Parser) previousTokenIs(tokens ...token.Type) bool {
+	for _, t := range tokens {
+		if p.previousToken.Type == t {
+			// if a match is found, return true
+			return true
+		}
+	}
+	// if no match is found, return false
+	return false
+}
+
 // peekTokenIs checks if the Parser's peekToken is any of the given token types
 func (p *Parser) peekTokenIs(tokens ...token.Type) bool {
 	// iterate through the given token types and check if any of them match the peekToken's type
@@ -588,7 +604,7 @@ func (p *Parser) parseExpression(precedence int) (ast.Expression, error) {
 	var exp ast.Expression
 	var err error
 
-	if p.currentTokenIs(token.NEWLINE) {
+	if p.currentTokenIs(token.NEWLINE) && p.previousTokenIs(token.LP, token.AND, token.OR, token.IN, token.NOT, token.ASSIGN) {
 		// advance to the next token
 		p.next()
 	}

pkg/dsl/parser/parser_test.go

@@ -896,5 +896,24 @@ var _ = Describe("parser", func() {
 			Expect(rs1.Name.Literal).Should(Equal("check_balance"))
 			Expect(rs1.Expression).Should(Equal("\nbalance >= amount && amount <= 5000\n\t\t"))
 		})
+
+		It("Case 25 - Multi-line Permission Expression w/ Rule - should fail", func() {
+			pr := NewParser(`
+			entity account {
+    			relation owner @user
+    			attribute balance float
+
+    			permission withdraw = check_balance(request.amount, balance)
+					owner
+			}
+	
+			rule check_balance(amount float, balance float) {
+				balance >= amount && amount <= 5000
+			}
+			`)
+
+			schema, err := pr.Parse()
+			Expect(err).Should(HaveOccurred())
+		})
 	})
 })