Merge pull request #55 from froth/super

Implementation of `super` keyword

src/ast/expr.rs

@@ -115,6 +115,7 @@ impl Display for Expr {
             Get(object, name) => write!(f, "(Get {}.{})", object, name.name),
             Set(object, name, value) => write!(f, "(Set {}.{} = {})", object, name.name, value),
             This => write!(f, "this"),
+            Super(method) => write!(f, "(super.{})", method.name),
         }
     }
 }
@@ -132,6 +133,7 @@ pub enum ExprType {
     Get(Box<Expr>, NameExpr),
     Set(Box<Expr>, NameExpr, Box<Expr>),
     This,
+    Super(NameExpr),
 }
 
 impl ExprType {

src/ast/name.rs

@@ -19,6 +19,14 @@ impl NameExpr {
             src: src.clone(),
         }
     }
+
+    pub fn super_name(location: SourceSpan, src: Arc<NamedSource<String>>) -> Self {
+        NameExpr {
+            name: Name::super_name(),
+            location,
+            src: src.clone(),
+        }
+    }
 }
 
 #[derive(Debug, Clone, PartialEq, Eq, Hash)]
@@ -33,6 +41,10 @@ impl Name {
         Name(TokenType::This.to_string())
     }
 
+    pub fn super_name() -> Self {
+        Name(TokenType::Super.to_string())
+    }
+
     pub fn init() -> Self {
         Name(String::from(INIT))
     }

src/interpreter/expression.rs

@@ -1,13 +1,17 @@
 use miette::SourceSpan;
 
-use crate::ast::{
-    expr::{Expr, ExprType},
-    name::NameExpr,
-    token::{Token, TokenType},
+use crate::{
+    ast::{
+        expr::{Expr, ExprType},
+        name::{Name, NameExpr},
+        token::{Token, TokenType},
+    },
+    interpreter::runtime_error::RuntimeError,
 };
 
 use super::{
-    literal::LiteralInterpreter, runtime_error::RuntimeError::*, types::Type, value::Value,
+    callable::Callable, literal::LiteralInterpreter, runtime_error::RuntimeError::*, types::Type,
+    value::Value,
 };
 use super::{Interpreter, Result};
 
@@ -27,6 +31,7 @@ impl Interpreter {
             Get(object, name) => self.get(object, name, location),
             Set(object, name, value) => self.set(object, name, value, location),
             This => self.read_variable(&NameExpr::this(location, expr.src.clone())),
+            Super(method) => self.interpret_super(method, location),
         }
     }
 
@@ -127,6 +132,48 @@ impl Interpreter {
         }
     }
 
+    fn interpret_super(&mut self, method_expr: &NameExpr, location: SourceSpan) -> Result<Value> {
+        let distance = self
+            .locals
+            .get(&NameExpr {
+                name: Name::super_name(),
+                location,
+                src: method_expr.src.clone(),
+            })
+            .expect("super local was undefined bug in resolver");
+        let superclass = self
+            .environment
+            .borrow()
+            .get_at(*distance, &Name::super_name())
+            .expect("super value not in environment: bug in interpreter");
+        let superclass = if let Value::Callable(Callable::Class(class)) = superclass {
+            class
+        } else {
+            panic!("super value not a class: bug in interpreter");
+        };
+        let object = self
+            .environment
+            .borrow()
+            .get_at(distance - 1, &Name::this())
+            .expect("object in super call was not in environment: bug in interpreter");
+        let object = if let Value::Instance(instance) = object {
+            instance
+        } else {
+            panic!("object value not an instance: bug in interpreter");
+        };
+        let method = superclass.find_method(&method_expr.name);
+        let method_name = method_expr.name.clone();
+        if let Some(method) = method {
+            Ok(Value::Callable(Callable::Function(method.bind(&object))))
+        } else {
+            Err(RuntimeError::UndefinedProperty {
+                name: method_name,
+                src: method_expr.src.clone(),
+                location: method_expr.location,
+            })
+        }
+    }
+
     fn handle_numbers(
         &mut self,
         left: &Expr,

src/interpreter/statement.rs

@@ -96,8 +96,17 @@ impl Interpreter {
             })
             .transpose()?;
 
-        let mut env = self.environment.borrow_mut();
-        env.define(name, Value::Nil);
+        self.environment.borrow_mut().define(name, Value::Nil);
+
+        if let Some(superclass) = &superclass {
+            let mut local_env = Environment::from_parent(self.environment.clone());
+            local_env.define(
+                &Name::super_name(),
+                Value::Callable(Callable::Class(superclass.clone())),
+            );
+            self.environment = Rc::new(RefCell::new(local_env))
+        }
+
         let methods = methods
             .iter()
             .map(|m| {
@@ -113,8 +122,22 @@ impl Interpreter {
                 )
             })
             .collect();
-        let class = Callable::Class(Class::new(name.clone(), superclass, methods));
-        env.assign(name, &Value::Callable(class));
+        let class = Callable::Class(Class::new(name.clone(), superclass.clone(), methods));
+
+        if superclass.is_some() {
+            let parent = self
+                .environment
+                .borrow()
+                .parent
+                .as_ref()
+                .expect("created above")
+                .clone();
+            self.environment = parent;
+        }
+
+        self.environment
+            .borrow_mut()
+            .assign(name, &Value::Callable(class));
         Ok(())
     }
 

src/parser/expression.rs

@@ -1,3 +1,5 @@
+use miette::SourceSpan;
+
 use crate::ast::expr::Expr;
 use crate::ast::literal::Literal;
 use crate::ast::name::{Name, NameExpr};
@@ -208,6 +210,7 @@ impl Parser {
                 location: token.location,
                 src: self.src.clone(),
             },
+            Super => self.parse_super(token.location)?,
             Eof => Err(UnexpectedEof {
                 src: token.src.clone(),
                 location: (
@@ -223,6 +226,37 @@ impl Parser {
         };
         Ok(expr)
     }
+
+    fn parse_super(&mut self, super_location: SourceSpan) -> Result<Expr> {
+        consume!(self, TokenType::Dot, |t: &Token| {
+            ExpectedDot {
+                src: t.src.clone(),
+                location: self.previous_if_eof(t.location),
+            }
+        });
+
+        let method = if let TokenType::Identifier(name) = &self.peek().token_type {
+            let location = self.peek().location;
+            let name = name.clone().into();
+            self.advance();
+            NameExpr {
+                name,
+                location,
+                src: self.src.clone(),
+            }
+        } else {
+            return Err(ExpectedIdentifier {
+                src: self.src.clone(),
+                location: self.peek().location,
+            });
+        };
+        let location = super_location.until(method.location);
+        Ok(Expr {
+            expr_type: ExprType::Super(method),
+            location,
+            src: self.src.clone(),
+        })
+    }
 }
 
 #[cfg(test)]
@@ -449,4 +483,17 @@ mod test {
             "(Set (variable object).name = (true))"
         )
     }
+
+    #[test]
+    fn parse_super() {
+        let name: String = "name".into();
+        let tokens = vec![
+            token(TokenType::Super),
+            token(TokenType::Dot),
+            token(TokenType::Identifier(name.clone())),
+            token(TokenType::Eof),
+        ];
+        let expr = parse_expr(tokens).unwrap();
+        assert_eq!(expr.to_string().trim_end(), "(super.name)")
+    }
 }

src/parser/parser_error.rs

@@ -70,6 +70,14 @@ pub enum ParserError {
         location: SourceSpan,
     },
 
+    #[error("Expected '.'")]
+    ExpectedDot {
+        #[source_code]
+        src: Arc<NamedSource<String>>,
+        #[label("here")]
+        location: SourceSpan,
+    },
+
     #[error("Invalid assignment target")]
     InvalidAssignmentTarget {
         #[source_code]

src/resolver/expr.rs

@@ -0,0 +1,93 @@
+use std::sync::Arc;
+
+use miette::{NamedSource, SourceSpan};
+
+use super::{resolution_error::ResolutionError, ClassType, Resolver, Result};
+use crate::ast::{
+    expr::{Expr, ExprType::*},
+    name::NameExpr,
+};
+
+impl Resolver {
+    pub(super) fn resolve_expr(&mut self, expression: &Expr) -> Result<()> {
+        match &expression.expr_type {
+            Assign(name_expr, expr) => {
+                self.resolve_expr(expr)?;
+                self.resolve_local(name_expr);
+                Ok(())
+            }
+            Binary(lhs, _, rhs) => {
+                self.resolve_expr(lhs)?;
+                self.resolve_expr(rhs)
+            }
+            Logical(lhs, _, rhs) => {
+                self.resolve_expr(lhs)?;
+                self.resolve_expr(rhs)
+            }
+            Grouping(expr) => self.resolve_expr(expr),
+            Literal(_) => Ok(()),
+            Unary(_, expr) => self.resolve_expr(expr),
+            Variable(name_expr) => self.resolve_var_expr(name_expr),
+            Call(name, arguments) => {
+                self.resolve_expr(name)?;
+                arguments.iter().try_for_each(|e| self.resolve_expr(e))
+            }
+            Get(expr, _) => self.resolve_expr(expr),
+            Set(expr, _, object) => {
+                self.resolve_expr(expr)?;
+                self.resolve_expr(object)
+            }
+            This => self.resolve_this(expression.location, &expression.src),
+            Super(_) => self.resolve_super(expression.location, &expression.src),
+        }
+    }
+
+    fn resolve_var_expr(&mut self, name_expr: &NameExpr) -> Result<()> {
+        if let Some(false) = self.scopes.last().and_then(|s| s.get(&name_expr.name)) {
+            Err(ResolutionError::InitializedWithSelf {
+                name: name_expr.name.clone(),
+                src: name_expr.src.clone(),
+                location: name_expr.location,
+            })
+        } else {
+            self.resolve_local(name_expr);
+            Ok(())
+        }
+    }
+
+    fn resolve_this(&mut self, location: SourceSpan, src: &Arc<NamedSource<String>>) -> Result<()> {
+        if self.current_class.is_none() {
+            Err(ResolutionError::InvalidThis {
+                src: src.clone(),
+                location,
+            })
+        } else {
+            let name_expr = NameExpr::this(location, src.clone());
+            self.resolve_local(&name_expr);
+            Ok(())
+        }
+    }
+
+    fn resolve_super(
+        &mut self,
+        location: SourceSpan,
+        src: &Arc<NamedSource<String>>,
+    ) -> Result<()> {
+        use ResolutionError::*;
+        match self.current_class {
+            None => Err(SuperOutsideClass {
+                src: src.clone(),
+                location,
+            }),
+            Some(ClassType::Class) => Err(SuperWithoutSuperclass {
+                src: src.clone(),
+                location,
+            }),
+            Some(ClassType::Subclass) => {
+                let name_expr = NameExpr::super_name(location, src.clone());
+                self.resolve_local(&name_expr);
+                Ok(())
+            }
+        }
+    }
+}