implement chapter 12 in rust

rust/rox/src/parser.rs

@@ -25,6 +25,8 @@ pub enum ParserError {
     SemicolonAfterValueExpected(usize),
     #[error("line {0}: expected ';' after expression.")]
     SemicolonAfterExpressionExpected(usize),
+    #[error("line {0}: expected class name.")]
+    ClassNameExpected(usize),
     #[error("line {0}: expected variable name.")]
     VariableNameExpected(usize),
     #[error("line {0}: invalid assignment target.")]
@@ -57,6 +59,12 @@ pub enum ParserError {
     LeftBraceBeforeFunctionBodyExpected(usize),
     #[error("line {0}: expected ';' after return value.")]
     SemicolonAfterReturnExpected(usize),
+    #[error("line {0}: expected '{{' before class body.")]
+    LeftBraceBeforeClassExpected(usize),
+    #[error("line {0}: expected '}}' after class body.")]
+    RightBraceAfterClassExpected(usize),
+    #[error("line {0}: expected property name after '.'.")]
+    PropertyNameAfterDotExpected(usize),
 }
 
 /// Parse the Lox language.
@@ -174,7 +182,9 @@ impl Parser {
     }
 
     fn declaration(&mut self) -> Result<Statement, ParserError> {
-        if self.matches(&[Fun]) {
+        if self.matches(&[Class]) {
+            self.class_declaration()
+        } else if self.matches(&[Fun]) {
             self.function()
         } else if self.matches(&[Var]) {
             self.var_declaration()
@@ -297,6 +307,28 @@ impl Parser {
         Ok(Statement::Return { keyword, value })
     }
 
+    fn class_declaration(&mut self) -> Result<Statement, ParserError> {
+        let line = self.current_token.line;
+        let name = self
+            .consume(&Identifier)
+            .ok_or(ParserError::ClassNameExpected(line))?
+            .clone();
+
+        self.consume(&LeftBrace)
+            .ok_or(ParserError::LeftBraceBeforeClassExpected(line))?;
+
+        let mut methods = Vec::new();
+        while !self.check(&RightBrace) && !self.is_at_end() {
+            let method = self.function()?;
+            methods.push(method);
+        }
+
+        self.consume(&RightBrace)
+            .ok_or(ParserError::RightBraceAfterClassExpected(line))?;
+
+        Ok(Statement::Class { name, methods })
+    }
+
     fn var_declaration(&mut self) -> Result<Statement, ParserError> {
         let line = self.current_token.line;
         let name = self
@@ -409,6 +441,12 @@ impl Parser {
                     name,
                     value: Box::new(value),
                 })
+            } else if let Expression::Get { object, name } = expr {
+                Ok(Expression::Set {
+                    object,
+                    name,
+                    value: Box::new(value),
+                })
             } else {
                 Err(ParserError::InvalidAssignmentTarget(equals.line))
             }
@@ -490,6 +528,17 @@ impl Parser {
         loop {
             if self.matches(&[LeftParen]) {
                 expr = self.finish_call(expr)?;
+            } else if self.matches(&[Dot]) {
+                let line = self.current_token.line;
+
+                let name = self
+                    .consume(&Identifier)
+                    .ok_or(ParserError::PropertyNameAfterDotExpected(line))?
+                    .clone();
+                expr = Expression::Get {
+                    object: Box::new(expr),
+                    name,
+                }
             } else {
                 break;
             }
@@ -536,6 +585,10 @@ impl Parser {
             Ok(Expression::Literal {
                 value: token::Literal::Nil,
             })
+        } else if self.matches(&[This]) {
+            Ok(Expression::This {
+                keyword: self.previous()?.clone(),
+            })
         } else if self.matches(&[Identifier]) {
             let prev = self.previous()?.clone();
             Ok(Expression::Variable { name: prev })