Move code generation into a build script

.gitignore

@@ -1 +1,3 @@
 /target
+# Autogenerated
+/src/ast.rs

Cargo.toml

@@ -4,10 +4,6 @@ version = "0.1.0"
 edition = "2021"
 default-run = "jlox-rust"
 
-[[bin]]
-name = "astgen"
-path = "bin/astgen.rs"
-
 [dependencies]
 anyhow = "1.0.83"
 itertools = "0.12.1"

build.rs

@@ -2,26 +2,31 @@
 
 use std::{
     collections::BTreeMap,
+    fs::File,
     io::{self, Write},
     iter,
 };
 
-fn main() {
-    let mut stdout = io::stdout();
+pub fn main() {
+    let mut ast_file = File::create("./src/ast.rs").expect("could not open src/ast.rs for writing");
+    do_ast_codegen(&mut ast_file);
+}
+
+fn do_ast_codegen<W: Write>(mut output: W) {
     // Autogenerated file, clippy can leave us alone
-    writeln!(stdout, "#![allow(clippy::all)]").unwrap();
+    writeln!(output, "#![allow(clippy::all)]").unwrap();
 
     writeln!(
-        stdout,
-        "// This file is auto-generated. Do not modify it directly, but rather use bin/astgen.rs.\n"
+        output,
+        "// This file is auto-generated. Do not modify it directly, but rather modify build.rs.\n"
     )
     .unwrap();
 
-    define_imports(&mut stdout, &["crate::lex::Token"]).expect("failed to define imports");
-    writeln!(stdout).unwrap();
+    define_imports(&mut output, &["crate::lex::Token"]).expect("failed to define imports");
+    writeln!(output).unwrap();
 
     define_literals(
-        &mut stdout,
+        &mut output,
         "LiteralValue",
         &BTreeMap::from([
             ("Number", Some("f64")),
@@ -32,7 +37,7 @@ fn main() {
         ]),
     )
     .expect("failed to generate literals");
-    writeln!(stdout).unwrap();
+    writeln!(output).unwrap();
 
     let expr_types = BTreeMap::from([
         (
@@ -44,21 +49,21 @@ fn main() {
         ("Literal", "value: LiteralValue"),
     ]);
 
-    define_ast(&mut stdout, "Expr", &expr_types).expect("failed to generate ast values");
-    writeln!(stdout).unwrap();
-    define_visitor_trait(&mut stdout, "ExprVisitor", "Expr", &expr_types)
+    define_ast(&mut output, "Expr", &expr_types).expect("failed to generate ast values");
+    writeln!(output).unwrap();
+    define_visitor_trait(&mut output, "ExprVisitor", "Expr", &expr_types)
         .expect("failed to generate visitor trait");
 
-    writeln!(stdout).unwrap();
+    writeln!(output).unwrap();
 
     let statement_types = BTreeMap::from([
         ("Expression", "expression: Expr"),
         ("Print", "expression: Expr"),
     ]);
 
-    define_ast(&mut stdout, "Stmt", &statement_types).expect("failed to generate ast values");
-    writeln!(stdout).unwrap();
-    define_visitor_trait(&mut stdout, "StmtVisitor", "Stmt", &statement_types)
+    define_ast(&mut output, "Stmt", &statement_types).expect("failed to generate ast values");
+    writeln!(output).unwrap();
+    define_visitor_trait(&mut output, "StmtVisitor", "Stmt", &statement_types)
         .expect("failed to generate visitor trait");
 }
 

src/ast.rs

@@ -1,70 +0,0 @@
-#![allow(clippy::all)]
-// This file is auto-generated. Do not modify it directly, but rather use bin/astgen.rs.
-
-use crate::lex::Token;
-
-#[derive(Debug, Clone)]
-pub enum LiteralValue {
-    False,
-    Nil,
-    Number(f64),
-    String(String),
-    True,
-}
-
-#[derive(Debug, Clone)]
-pub enum Expr {
-    Binary {
-         left: Box<Expr>,
-         operator: Token,
-         right: Box<Expr>,
-    },
-    Grouping {
-         expr: Box<Expr>,
-    },
-    Literal {
-         value: LiteralValue,
-    },
-    Unary {
-         expr: Box<Expr>,
-         operator: Token,
-    },
-}
-
-pub trait ExprVisitor<T> {
-    fn visit_expr(&mut self, expr: &Expr) -> T {
-        match expr {
-            Expr::Binary { left, operator, right } => self.visit_binary(left.as_ref(), &operator, right.as_ref()),
-            Expr::Grouping { expr } => self.visit_grouping(expr.as_ref()),
-            Expr::Literal { value } => self.visit_literal(&value),
-            Expr::Unary { expr, operator } => self.visit_unary(expr.as_ref(), &operator),
-        }
-    }
-
-    fn visit_binary(&mut self, left: &Expr, operator: &Token, right: &Expr) -> T;
-    fn visit_grouping(&mut self, expr: &Expr) -> T;
-    fn visit_literal(&mut self, value: &LiteralValue) -> T;
-    fn visit_unary(&mut self, expr: &Expr, operator: &Token) -> T;
-}
-
-#[derive(Debug, Clone)]
-pub enum Stmt {
-    Expression {
-         expression: Expr,
-    },
-    Print {
-         expression: Expr,
-    },
-}
-
-pub trait StmtVisitor<T> {
-    fn visit_stmt(&mut self, stmt: &Stmt) -> T {
-        match stmt {
-            Stmt::Expression { expression } => self.visit_expression(&expression),
-            Stmt::Print { expression } => self.visit_print(&expression),
-        }
-    }
-
-    fn visit_expression(&mut self, expression: &Expr) -> T;
-    fn visit_print(&mut self, expression: &Expr) -> T;
-}