Implement lexing for boolean values

dust-lang/src/abstract_tree.rs

@@ -35,6 +35,7 @@ pub enum Statement {
 
     // Expressions
     Add(Box<Node>, Box<Node>),
+    BuiltInValue(Box<Node>),
     PropertyAccess(Box<Node>, Box<Node>),
     List(Vec<Node>),
     Multiply(Box<Node>, Box<Node>),
@@ -50,6 +51,7 @@ impl Statement {
         match self {
             Statement::Add(left, _) => left.statement.expected_type(variables),
             Statement::Assign(_, _) => None,
+            Statement::BuiltInValue(reserved) => reserved.statement.expected_type(variables),
             Statement::Constant(value) => Some(value.r#type(variables)),
             Statement::Identifier(identifier) => variables
                 .get(identifier)
@@ -58,8 +60,7 @@ impl Statement {
             Statement::Multiply(left, _) => left.statement.expected_type(variables),
             Statement::PropertyAccess(_, _) => None,
             Statement::ReservedIdentifier(reserved) => match reserved {
-                ReservedIdentifier::IsEven => Some(Type::Boolean),
-                ReservedIdentifier::IsOdd => Some(Type::Boolean),
+                ReservedIdentifier::IsEven | ReservedIdentifier::IsOdd => Some(Type::Boolean),
                 ReservedIdentifier::Length => Some(Type::Integer),
             },
         }
@@ -69,23 +70,24 @@ impl Statement {
 impl Display for Statement {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
         match self {
-            Statement::Assign(left, right) => write!(f, "{} = {}", left, right),
-            Statement::Add(left, right) => write!(f, "{} + {}", left, right),
-            Statement::PropertyAccess(left, right) => write!(f, "{}.{}", left, right),
+            Statement::Assign(left, right) => write!(f, "{left} = {right}"),
+            Statement::Add(left, right) => write!(f, "{left} + {right}"),
+            Statement::BuiltInValue(reserved) => write!(f, "{reserved}"),
+            Statement::PropertyAccess(left, right) => write!(f, "{left}.{right}"),
             Statement::List(nodes) => {
                 write!(f, "[")?;
                 for (i, node) in nodes.iter().enumerate() {
                     if i > 0 {
                         write!(f, ", ")?;
                     }
-                    write!(f, "{}", node)?;
+                    write!(f, "{node}")?;
                 }
                 write!(f, "]")
             }
-            Statement::Multiply(left, right) => write!(f, "{} * {}", left, right),
-            Statement::Constant(value) => write!(f, "{}", value),
-            Statement::Identifier(identifier) => write!(f, "{}", identifier),
-            Statement::ReservedIdentifier(identifier) => write!(f, "{}", identifier),
+            Statement::Multiply(left, right) => write!(f, "{left} * {right}"),
+            Statement::Constant(value) => write!(f, "{value}"),
+            Statement::Identifier(identifier) => write!(f, "{identifier}"),
+            Statement::ReservedIdentifier(identifier) => write!(f, "{identifier}"),
         }
     }
 }

dust-lang/src/analyzer.rs

@@ -40,6 +40,9 @@ impl Analyzer {
 
                 self.analyze_node(right)?;
             }
+            Statement::BuiltInValue(node) => {
+                self.analyze_node(node)?;
+            }
             Statement::Constant(_) => {}
             Statement::Identifier(_) => {
                 return Err(AnalyzerError::UnexpectedIdentifier {

dust-lang/src/lex.rs

@@ -57,7 +57,7 @@ impl<'a> Lexer<'a> {
         let (token, span) = if let Some(c) = self.peek_char() {
             match c {
                 '0'..='9' => self.lex_number()?,
-                'a'..='z' | 'A'..='Z' => self.lex_identifier()?,
+                'a'..='z' | 'A'..='Z' => self.lex_alphabetical()?,
                 '+' => {
                     self.position += 1;
                     (Token::Plus, (self.position - 1, self.position))
@@ -124,6 +124,19 @@ impl<'a> Lexer<'a> {
         self.source[self.position..].chars().nth(1)
     }
 
+    fn peek_until_whitespace(&self) -> Option<&str> {
+        let start = self.position;
+        let end = self.source[self.position..]
+            .find(char::is_whitespace)
+            .map(|i| i + start);
+
+        if let Some(end) = end {
+            Some(&self.source[start..end])
+        } else {
+            None
+        }
+    }
+
     /// Lex an integer or float token.
     fn lex_number(&mut self) -> Result<(Token, Span), LexError> {
         let start_pos = self.position;
@@ -167,7 +180,7 @@ impl<'a> Lexer<'a> {
     }
 
     /// Lex an identifier token.
-    fn lex_identifier(&mut self) -> Result<(Token, Span), LexError> {
+    fn lex_alphabetical(&mut self) -> Result<(Token, Span), LexError> {
         let start_pos = self.position;
 
         while let Some(c) = self.peek_char() {
@@ -180,6 +193,8 @@ impl<'a> Lexer<'a> {
 
         let string = &self.source[start_pos..self.position];
         let token = match string {
+            "true" => Token::Boolean(true),
+            "false" => Token::Boolean(false),
             "is_even" => Token::ReservedIdentifier(ReservedIdentifier::IsEven),
             "is_odd" => Token::ReservedIdentifier(ReservedIdentifier::IsOdd),
             "length" => Token::ReservedIdentifier(ReservedIdentifier::Length),
@@ -212,6 +227,26 @@ impl From<ParseIntError> for LexError {
 mod tests {
     use super::*;
 
+    #[test]
+    fn r#true() {
+        let input = "true";
+
+        assert_eq!(
+            lex(input),
+            Ok(vec![(Token::Boolean(true), (0, 4)), (Token::Eof, (4, 4)),])
+        )
+    }
+
+    #[test]
+    fn r#false() {
+        let input = "false";
+
+        assert_eq!(
+            lex(input),
+            Ok(vec![(Token::Boolean(false), (0, 5)), (Token::Eof, (5, 5))])
+        )
+    }
+
     #[test]
     fn integer_property_access() {
         let input = "42.is_even";

dust-lang/src/token.rs

@@ -6,6 +6,7 @@ use crate::Identifier;
 
 #[derive(Debug, PartialEq, Clone)]
 pub enum Token {
+    Boolean(bool),
     Comma,
     Dot,
     Eof,
@@ -24,8 +25,11 @@ pub enum Token {
 
 #[derive(Debug, Clone, Eq, PartialEq, PartialOrd, Ord, Serialize, Deserialize)]
 pub enum ReservedIdentifier {
+    // Number properties
     IsEven,
     IsOdd,
+
+    // List properties
     Length,
 }
 

dust-lang/src/vm.rs

@@ -42,6 +42,7 @@ impl Vm {
         variables: &mut HashMap<Identifier, Value>,
     ) -> Result<Option<Value>, VmError> {
         match node.statement {
+            Statement::BuiltInValue(node) => self.run_node(*node, variables),
             Statement::Constant(value) => Ok(Some(value.clone())),
             Statement::Identifier(_) => Ok(None),
             Statement::ReservedIdentifier(_) => Ok(None),
@@ -143,6 +144,16 @@ impl Vm {
                                 });
                             }
                         }
+                        _ => {
+                            return Err(VmError::ExpectedDifferentReservedIdentifier {
+                                position: right_span,
+                                expected: vec![
+                                    ReservedIdentifier::IsEven,
+                                    ReservedIdentifier::IsOdd,
+                                    ReservedIdentifier::Length,
+                                ],
+                            })
+                        }
                     }
                 }
 
@@ -170,11 +181,25 @@ pub enum VmError {
 
     // Anaylsis Failures
     // These should be prevented by running the analyzer before the VM
-    ExpectedIdentifier { position: Span },
-    ExpectedIdentifierOrInteger { position: Span },
-    ExpectedInteger { position: Span },
-    ExpectedList { position: Span },
-    ExpectedValue { position: Span },
+    ExpectedIdentifier {
+        position: Span,
+    },
+    ExpectedIdentifierOrInteger {
+        position: Span,
+    },
+    ExpectedInteger {
+        position: Span,
+    },
+    ExpectedList {
+        position: Span,
+    },
+    ExpectedDifferentReservedIdentifier {
+        position: Span,
+        expected: Vec<ReservedIdentifier>,
+    },
+    ExpectedValue {
+        position: Span,
+    },
 }
 
 impl From<ParseError> for VmError {