From f8b3e2a100fdb28cad24948703439d2964c31580 Mon Sep 17 00:00:00 2001
From: Vincent Ambo <mail@tazj.in>
Date: Sun, 17 Jan 2021 12:13:52 +0300
Subject: refactor(tazjin/rlox): Move treewalk interpreter into subdirectory

Change-Id: I9163f75db5a1ff75e1b1f81bad78fd9d8ddb104a
Reviewed-on: https://cl.tvl.fyi/c/depot/+/2409
Reviewed-by: tazjin <mail@tazj.in>
Tested-by: BuildkiteCI
---
 users/tazjin/rlox/src/interpreter.rs | 482 -----------------------------------
 1 file changed, 482 deletions(-)
 delete mode 100644 users/tazjin/rlox/src/interpreter.rs

(limited to 'users/tazjin/rlox/src/interpreter.rs')

diff --git a/users/tazjin/rlox/src/interpreter.rs b/users/tazjin/rlox/src/interpreter.rs
deleted file mode 100644
index c9de3831c8..0000000000
--- a/users/tazjin/rlox/src/interpreter.rs
+++ /dev/null
@@ -1,482 +0,0 @@
-use crate::errors::{Error, ErrorKind};
-use crate::parser::{self, Block, Expr, Literal, Statement};
-use crate::resolver;
-use crate::scanner::{self, TokenKind};
-use std::collections::HashMap;
-use std::rc::Rc;
-use std::sync::RwLock;
-
-// Implementation of built-in functions.
-mod builtins;
-
-#[cfg(test)]
-mod tests;
-
-// Tree-walk interpreter
-
-// Representation of all callables, including builtins & user-defined
-// functions.
-#[derive(Clone, Debug)]
-pub enum Callable {
-    Builtin(&'static dyn builtins::Builtin),
-    Function {
-        func: Rc<parser::Function>,
-        closure: Rc<RwLock<Environment>>,
-    },
-}
-
-impl Callable {
-    fn arity(&self) -> usize {
-        match self {
-            Callable::Builtin(builtin) => builtin.arity(),
-            Callable::Function { func, .. } => func.params.len(),
-        }
-    }
-
-    fn call(&self, lox: &mut Interpreter, args: Vec<Value>) -> Result<Value, Error> {
-        match self {
-            Callable::Builtin(builtin) => builtin.call(args),
-
-            Callable::Function { func, closure } => {
-                let mut fn_env: Environment = Default::default();
-                fn_env.enclosing = Some(closure.clone());
-
-                for (param, value) in func.params.iter().zip(args.into_iter()) {
-                    fn_env.define(param, value)?;
-                }
-
-                let result =
-                    lox.interpret_block_with_env(Some(Rc::new(RwLock::new(fn_env))), &func.body);
-
-                match result {
-                    // extract returned values if applicable
-                    Err(Error {
-                        kind: ErrorKind::FunctionReturn(value),
-                        ..
-                    }) => Ok(value),
-
-                    // otherwise just return the result itself
-                    _ => result,
-                }
-            }
-        }
-    }
-}
-
-// Representation of an in-language value.
-#[derive(Clone, Debug)]
-pub enum Value {
-    Literal(Literal),
-    Callable(Callable),
-}
-
-impl PartialEq for Value {
-    fn eq(&self, other: &Self) -> bool {
-        match (self, other) {
-            (Value::Literal(lhs), Value::Literal(rhs)) => lhs == rhs,
-            // functions do not have equality
-            _ => false,
-        }
-    }
-}
-
-impl From<Literal> for Value {
-    fn from(lit: Literal) -> Value {
-        Value::Literal(lit)
-    }
-}
-
-impl Value {
-    fn expect_literal(self) -> Result<Literal, Error> {
-        match self {
-            Value::Literal(lit) => Ok(lit),
-            _ => unimplemented!(), // which error? which line?
-        }
-    }
-}
-
-#[derive(Debug, Default)]
-pub struct Environment {
-    enclosing: Option<Rc<RwLock<Environment>>>,
-    values: HashMap<String, Value>,
-}
-
-impl Environment {
-    fn define(&mut self, name: &scanner::Token, value: Value) -> Result<(), Error> {
-        let ident = identifier_str(name)?;
-        self.values.insert(ident.into(), value);
-        Ok(())
-    }
-
-    fn get(&self, ident: &str, line: usize, depth: usize) -> Result<Value, Error> {
-        if depth > 0 {
-            match &self.enclosing {
-                None => {
-                    return Err(Error {
-                        line,
-                        kind: ErrorKind::InternalError(format!(
-                            "invalid depth {} for {}",
-                            depth, ident
-                        )),
-                    })
-                }
-                Some(parent) => {
-                    let env = parent.read().expect("fatal: environment lock poisoned");
-                    return env.get(ident, line, depth - 1);
-                }
-            }
-        }
-
-        self.values
-            .get(ident)
-            .map(Clone::clone)
-            .ok_or_else(|| Error {
-                line,
-                kind: ErrorKind::UndefinedVariable(ident.into()),
-            })
-    }
-
-    fn assign(&mut self, name: &scanner::Token, value: Value) -> Result<(), Error> {
-        let ident = identifier_str(name)?;
-
-        match self.values.get_mut(ident) {
-            Some(target) => {
-                *target = value;
-                Ok(())
-            }
-            None => {
-                if let Some(parent) = &self.enclosing {
-                    return parent.write().unwrap().assign(name, value);
-                }
-
-                Err(Error {
-                    line: name.line,
-                    kind: ErrorKind::UndefinedVariable(ident.into()),
-                })
-            }
-        }
-    }
-}
-
-fn identifier_str(name: &scanner::Token) -> Result<&str, Error> {
-    if let TokenKind::Identifier(ident) = &name.kind {
-        Ok(ident)
-    } else {
-        Err(Error {
-            line: name.line,
-            kind: ErrorKind::InternalError("unexpected identifier kind".into()),
-        })
-    }
-}
-
-#[derive(Debug)]
-pub struct Interpreter {
-    env: Rc<RwLock<Environment>>,
-}
-
-impl Interpreter {
-    /// Create a new interpreter and configure the initial global
-    /// variable set.
-    pub fn create() -> Self {
-        let mut globals = HashMap::new();
-
-        globals.insert(
-            "clock".into(),
-            Value::Callable(Callable::Builtin(&builtins::Clock {})),
-        );
-
-        Interpreter {
-            env: Rc::new(RwLock::new(Environment {
-                enclosing: None,
-                values: globals,
-            })),
-        }
-    }
-
-    // Environment modification helpers
-    fn define_var(&mut self, name: &scanner::Token, value: Value) -> Result<(), Error> {
-        self.env
-            .write()
-            .expect("environment lock is poisoned")
-            .define(name, value)
-    }
-
-    fn assign_var(&mut self, name: &scanner::Token, value: Value) -> Result<(), Error> {
-        self.env
-            .write()
-            .expect("environment lock is poisoned")
-            .assign(name, value)
-    }
-
-    fn get_var(&mut self, var: &parser::Variable) -> Result<Value, Error> {
-        let ident = identifier_str(&var.name)?;
-        let depth = var.depth.ok_or_else(|| Error {
-            line: var.name.line,
-            kind: ErrorKind::UndefinedVariable(ident.into()),
-        })?;
-
-        self.env
-            .read()
-            .expect("environment lock is poisoned")
-            .get(ident, var.name.line, depth)
-    }
-
-    // Interpreter itself
-    pub fn interpret(&mut self, mut program: Block) -> Result<Value, Error> {
-        let globals = self.env.read()
-            .expect("static globals lock poisoned")
-            .values.keys().map(Clone::clone)
-            .collect::<Vec<String>>();
-
-        resolver::resolve(&globals, &mut program)?;
-        self.interpret_block_with_env(None, &program)
-    }
-
-    /// Interpret the block in the supplied environment. If no
-    /// environment is supplied, a new one is created using the
-    /// current one as its parent.
-    fn interpret_block_with_env(
-        &mut self,
-        env: Option<Rc<RwLock<Environment>>>,
-        block: &parser::Block,
-    ) -> Result<Value, Error> {
-        let env = match env {
-            Some(env) => env,
-            None => {
-                let env: Rc<RwLock<Environment>> = Default::default();
-                set_enclosing_env(&env, self.env.clone());
-                env
-            }
-        };
-
-        let previous = std::mem::replace(&mut self.env, env);
-        let result = self.interpret_block(block);
-
-        // Swap it back, discarding the child env.
-        self.env = previous;
-
-        return result;
-    }
-
-    fn interpret_block(&mut self, program: &Block) -> Result<Value, Error> {
-        let mut value = Value::Literal(Literal::Nil);
-
-        for stmt in program {
-            value = self.interpret_stmt(stmt)?;
-        }
-
-        Ok(value)
-    }
-
-    fn interpret_stmt(&mut self, stmt: &Statement) -> Result<Value, Error> {
-        let value = match stmt {
-            Statement::Expr(expr) => self.eval(expr)?,
-            Statement::Print(expr) => {
-                let result = self.eval(expr)?;
-                let output = format!("{:?}", result);
-                println!("{}", output);
-                Value::Literal(Literal::String(output))
-            }
-            Statement::Var(var) => return self.interpret_var(var),
-            Statement::Block(block) => return self.interpret_block_with_env(None, block),
-            Statement::If(if_stmt) => return self.interpret_if(if_stmt),
-            Statement::While(while_stmt) => return self.interpret_while(while_stmt),
-            Statement::Function(func) => return self.interpret_function(func.clone()),
-            Statement::Return(ret) => {
-                return Err(Error {
-                    line: 0,
-                    kind: ErrorKind::FunctionReturn(self.eval(&ret.value)?),
-                })
-            }
-        };
-
-        Ok(value)
-    }
-
-    fn interpret_var(&mut self, var: &parser::Var) -> Result<Value, Error> {
-        let init = var.initialiser.as_ref().ok_or_else(|| Error {
-            line: var.name.line,
-            kind: ErrorKind::InternalError("missing variable initialiser".into()),
-        })?;
-        let value = self.eval(init)?;
-        self.define_var(&var.name, value.clone())?;
-        Ok(value)
-    }
-
-    fn interpret_if(&mut self, if_stmt: &parser::If) -> Result<Value, Error> {
-        let condition = self.eval(&if_stmt.condition)?;
-
-        if eval_truthy(&condition) {
-            self.interpret_stmt(&if_stmt.then_branch)
-        } else if let Some(else_branch) = &if_stmt.else_branch {
-            self.interpret_stmt(else_branch)
-        } else {
-            Ok(Value::Literal(Literal::Nil))
-        }
-    }
-
-    fn interpret_while(&mut self, stmt: &parser::While) -> Result<Value, Error> {
-        let mut value = Value::Literal(Literal::Nil);
-        while eval_truthy(&self.eval(&stmt.condition)?) {
-            value = self.interpret_stmt(&stmt.body)?;
-        }
-
-        Ok(value)
-    }
-
-    fn interpret_function(&mut self, func: Rc<parser::Function>) -> Result<Value, Error> {
-        let name = func.name.clone();
-        let value = Value::Callable(Callable::Function {
-            func,
-            closure: self.env.clone(),
-        });
-        self.define_var(&name, value.clone())?;
-        Ok(value)
-    }
-
-    fn eval(&mut self, expr: &Expr) -> Result<Value, Error> {
-        match expr {
-            Expr::Assign(assign) => self.eval_assign(assign),
-            Expr::Literal(lit) => Ok(lit.clone().into()),
-            Expr::Grouping(grouping) => self.eval(&*grouping.0),
-            Expr::Unary(unary) => self.eval_unary(unary),
-            Expr::Binary(binary) => self.eval_binary(binary),
-            Expr::Variable(var) => self.get_var(var),
-            Expr::Logical(log) => self.eval_logical(log),
-            Expr::Call(call) => self.eval_call(call),
-        }
-    }
-
-    fn eval_unary(&mut self, expr: &parser::Unary) -> Result<Value, Error> {
-        let right = self.eval(&*expr.right)?;
-
-        match (&expr.operator.kind, right) {
-            (TokenKind::Minus, Value::Literal(Literal::Number(num))) => {
-                Ok(Literal::Number(-num).into())
-            }
-            (TokenKind::Bang, right) => Ok(Literal::Boolean(!eval_truthy(&right)).into()),
-
-            (op, right) => Err(Error {
-                line: expr.operator.line,
-                kind: ErrorKind::TypeError(format!(
-                    "Operator '{:?}' can not be called with argument '{:?}'",
-                    op, right
-                )),
-            }),
-        }
-    }
-
-    fn eval_binary(&mut self, expr: &parser::Binary) -> Result<Value, Error> {
-        let left = self.eval(&*expr.left)?.expect_literal()?;
-        let right = self.eval(&*expr.right)?.expect_literal()?;
-
-        let result = match (&expr.operator.kind, left, right) {
-            // Numeric
-            (TokenKind::Minus, Literal::Number(l), Literal::Number(r)) => Literal::Number(l - r),
-            (TokenKind::Slash, Literal::Number(l), Literal::Number(r)) => Literal::Number(l / r),
-            (TokenKind::Star, Literal::Number(l), Literal::Number(r)) => Literal::Number(l * r),
-            (TokenKind::Plus, Literal::Number(l), Literal::Number(r)) => Literal::Number(l + r),
-
-            // Strings
-            (TokenKind::Plus, Literal::String(l), Literal::String(r)) => {
-                Literal::String(format!("{}{}", l, r))
-            }
-
-            // Comparators (on numbers only?)
-            (TokenKind::Greater, Literal::Number(l), Literal::Number(r)) => Literal::Boolean(l > r),
-            (TokenKind::GreaterEqual, Literal::Number(l), Literal::Number(r)) => {
-                Literal::Boolean(l >= r)
-            }
-            (TokenKind::Less, Literal::Number(l), Literal::Number(r)) => Literal::Boolean(l < r),
-            (TokenKind::LessEqual, Literal::Number(l), Literal::Number(r)) => {
-                Literal::Boolean(l <= r)
-            }
-
-            // Equality
-            (TokenKind::Equal, l, r) => Literal::Boolean(l == r),
-            (TokenKind::BangEqual, l, r) => Literal::Boolean(l != r),
-
-            (op, left, right) => {
-                return Err(Error {
-                    line: expr.operator.line,
-                    kind: ErrorKind::TypeError(format!(
-                        "Operator '{:?}' can not be called with arguments '({:?}, {:?})'",
-                        op, left, right
-                    )),
-                })
-            }
-        };
-
-        Ok(result.into())
-    }
-
-    fn eval_assign(&mut self, assign: &parser::Assign) -> Result<Value, Error> {
-        let value = self.eval(&assign.value)?;
-        self.assign_var(&assign.name, value.clone())?;
-        Ok(value)
-    }
-
-    fn eval_logical(&mut self, logical: &parser::Logical) -> Result<Value, Error> {
-        let left = eval_truthy(&self.eval(&logical.left)?);
-        let right = eval_truthy(&self.eval(&logical.right)?);
-
-        match &logical.operator.kind {
-            TokenKind::And => Ok(Literal::Boolean(left && right).into()),
-            TokenKind::Or => Ok(Literal::Boolean(left || right).into()),
-            kind => Err(Error {
-                line: logical.operator.line,
-                kind: ErrorKind::InternalError(format!("Invalid logical operator: {:?}", kind)),
-            }),
-        }
-    }
-
-    fn eval_call(&mut self, call: &parser::Call) -> Result<Value, Error> {
-        let callable = match self.eval(&call.callee)? {
-            Value::Callable(c) => c,
-            Value::Literal(v) => {
-                return Err(Error {
-                    line: call.paren.line,
-                    kind: ErrorKind::RuntimeError(format!("not callable: {:?}", v)),
-                })
-            }
-        };
-
-        let mut args = vec![];
-        for arg in &call.args {
-            args.push(self.eval(arg)?);
-        }
-
-        if callable.arity() != args.len() {
-            return Err(Error {
-                line: call.paren.line,
-                kind: ErrorKind::RuntimeError(format!(
-                    "Expected {} arguments, but got {}",
-                    callable.arity(),
-                    args.len(),
-                )),
-            });
-        }
-
-        callable.call(self, args)
-    }
-}
-
-// Interpreter functions not dependent on interpreter-state.
-
-fn eval_truthy(lit: &Value) -> bool {
-    if let Value::Literal(lit) = lit {
-        match lit {
-            Literal::Nil => false,
-            Literal::Boolean(b) => *b,
-            _ => true,
-        }
-    } else {
-        false
-    }
-}
-
-fn set_enclosing_env(this: &RwLock<Environment>, parent: Rc<RwLock<Environment>>) {
-    this.write()
-        .expect("environment lock is poisoned")
-        .enclosing = Some(parent);
-}
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