refactor(tazjin/rlox): Move entrypoints into interpreters r/2123

Right now this introduces a simple mechanism to flip between the
interpreters.

Change-Id: I92ee920c53d76ab6b664ac671993a6d6426af61a
Reviewed-on: https://cl.tvl.fyi/c/depot/+/2412
Reviewed-by: tazjin <mail@tazj.in>
Tested-by: BuildkiteCI

5 files changed, 69 insertions, 48 deletions

diff --git a/users/tazjin/rlox/src/bytecode/mod.rs b/users/tazjin/rlox/src/bytecode/mod.rs
new file mode 100644
index 0000000000..412e73106e
--- /dev/null
+++ b/users/tazjin/rlox/src/bytecode/mod.rs
@@ -0,0 +1,7 @@
+//! Bytecode interpreter for Lox.
+//!
+//! https://craftinginterpreters.com/chunks-of-bytecode.html
+
+pub fn main() {
+    unimplemented!()
+}
diff --git a/users/tazjin/rlox/src/main.rs b/users/tazjin/rlox/src/main.rs
index 1c1dd6f42f..13a5748187 100644
--- a/users/tazjin/rlox/src/main.rs
+++ b/users/tazjin/rlox/src/main.rs
@@ -4,56 +4,16 @@ use std::io;
 use std::io::Write;
 use std::process;
 
+mod bytecode;
 mod errors;
 mod parser;
 mod scanner;
 mod treewalk;
 
 fn main() {
-    let mut args = env::args();
-
-    if args.len() > 2 {
-        println!("Usage: rlox [script]");
-        process::exit(1);
-    } else if let Some(file) = args.nth(1) {
-        run_file(&file);
-    } else {
-        run_prompt();
-    }
-}
-
-// Run Lox code from a file and print results to stdout
-fn run_file(file: &str) {
-    let contents = fs::read_to_string(file).expect("failed to read the input file");
-    let mut lox = treewalk::interpreter::Interpreter::create();
-    run(&mut lox, &contents);
-}
-
-// Evaluate Lox code interactively in a shitty REPL.
-fn run_prompt() {
-    let mut line = String::new();
-    let mut lox = treewalk::interpreter::Interpreter::create();
-
-    loop {
-        print!("> ");
-        io::stdout().flush().unwrap();
-        io::stdin()
-            .read_line(&mut line)
-            .expect("failed to read user input");
-        run(&mut lox, &line);
-        line.clear();
-    }
-}
-
-fn run(lox: &mut treewalk::interpreter::Interpreter, code: &str) {
-    let chars: Vec<char> = code.chars().collect();
-
-    let result = scanner::scan(&chars)
-        .and_then(|tokens| parser::parse(tokens))
-        .and_then(|program| lox.interpret(program).map_err(|e| vec![e]));
-
-    if let Err(errors) = result {
-        report_errors(errors);
+    match env::var("LOX_INTERPRETER").as_ref().map(String::as_str) {
+        Ok("treewalk") => treewalk::main(),
+        _ => bytecode::main(),
     }
 }
 
diff --git a/users/tazjin/rlox/src/treewalk/interpreter.rs b/users/tazjin/rlox/src/treewalk/interpreter.rs
index 32822d72fa..5b47dc0248 100644
--- a/users/tazjin/rlox/src/treewalk/interpreter.rs
+++ b/users/tazjin/rlox/src/treewalk/interpreter.rs
@@ -1,7 +1,7 @@
 use crate::errors::{Error, ErrorKind};
 use crate::parser::{self, Block, Expr, Literal, Statement};
-use crate::treewalk::resolver;
 use crate::scanner::{self, TokenKind};
+use crate::treewalk::resolver;
 use std::collections::HashMap;
 use std::rc::Rc;
 use std::sync::RwLock;
@@ -223,9 +223,13 @@ impl Interpreter {
 
     // Interpreter itself
     pub fn interpret(&mut self, mut program: Block) -> Result<Value, Error> {
-        let globals = self.env.read()
+        let globals = self
+            .env
+            .read()
             .expect("static globals lock poisoned")
-            .values.keys().map(Clone::clone)
+            .values
+            .keys()
+            .map(Clone::clone)
             .collect::<Vec<String>>();
 
         resolver::resolve(&globals, &mut program)?;
diff --git a/users/tazjin/rlox/src/treewalk/interpreter/builtins.rs b/users/tazjin/rlox/src/treewalk/interpreter/builtins.rs
index 614f30ff3b..0ec6ae08c3 100644
--- a/users/tazjin/rlox/src/treewalk/interpreter/builtins.rs
+++ b/users/tazjin/rlox/src/treewalk/interpreter/builtins.rs
@@ -2,8 +2,8 @@ use std::fmt;
 use std::time::{SystemTime, UNIX_EPOCH};
 
 use crate::errors::Error;
-use crate::treewalk::interpreter::Value;
 use crate::parser::Literal;
+use crate::treewalk::interpreter::Value;
 
 pub trait Builtin: fmt::Debug {
     fn arity(&self) -> usize;
diff --git a/users/tazjin/rlox/src/treewalk/mod.rs b/users/tazjin/rlox/src/treewalk/mod.rs
index d76045b91b..95136b2fa1 100644
--- a/users/tazjin/rlox/src/treewalk/mod.rs
+++ b/users/tazjin/rlox/src/treewalk/mod.rs
@@ -1,2 +1,52 @@
+use crate::*;
+
 pub mod interpreter;
 mod resolver;
+
+pub fn main() {
+    let mut args = env::args();
+
+    if args.len() > 2 {
+        println!("Usage: rlox [script]");
+        process::exit(1);
+    } else if let Some(file) = args.nth(1) {
+        run_file(&file);
+    } else {
+        run_prompt();
+    }
+}
+
+// Run Lox code from a file and print results to stdout
+fn run_file(file: &str) {
+    let contents = fs::read_to_string(file).expect("failed to read the input file");
+    let mut lox = treewalk::interpreter::Interpreter::create();
+    run(&mut lox, &contents);
+}
+
+// Evaluate Lox code interactively in a shitty REPL.
+fn run_prompt() {
+    let mut line = String::new();
+    let mut lox = treewalk::interpreter::Interpreter::create();
+
+    loop {
+        print!("> ");
+        io::stdout().flush().unwrap();
+        io::stdin()
+            .read_line(&mut line)
+            .expect("failed to read user input");
+        run(&mut lox, &line);
+        line.clear();
+    }
+}
+
+fn run(lox: &mut treewalk::interpreter::Interpreter, code: &str) {
+    let chars: Vec<char> = code.chars().collect();
+
+    let result = scanner::scan(&chars)
+        .and_then(|tokens| parser::parse(tokens))
+        .and_then(|program| lox.interpret(program).map_err(|e| vec![e]));
+
+    if let Err(errors) = result {
+        report_errors(errors);
+    }
+}