feat: handle expect in parser

* map both assert/expect to Token::Expect
* use the new token in the parser
* new unit test to expect

crates/aiken-lang/src/parser/lexer.rs

@@ -87,7 +87,8 @@ pub fn lexer() -> impl Parser<char, Vec<(Token, Span)>, Error = ParseError> {
         "trace" => Token::Trace,
         "error" => Token::ErrorTerm,
         "as" => Token::As,
-        "assert" => Token::Assert,
+        "assert" => Token::Expect,
+        "expect" => Token::Expect,
         "const" => Token::Const,
         "fn" => Token::Fn,
         "test" => Token::Test,

crates/aiken-lang/src/parser/token.rs

@@ -60,7 +60,6 @@ pub enum Token {
     NewLine,
     // Keywords (alphabetically):
     As,
-    Assert,
     Const,
     Fn,
     If,
@@ -141,7 +140,6 @@ impl fmt::Display for Token {
             Token::EmptyLine => "EMPTYLINE",
             Token::NewLine => "NEWLINE",
             Token::As => "as",
-            Token::Assert => "assert",
             Token::Expect => "expect",
             Token::When => "when",
             Token::Is => "is",