prepare types for two-pass implementation

src/lib.rs

@@ -1,4 +1,5 @@
 pub mod ast;
 pub mod run;
 pub mod scope;
+pub mod twopass;
 pub mod types;

src/twopass.rs

@@ -0,0 +1,79 @@
+use std::collections::HashMap;
+
+use crate::ast;
+
+#[derive(Debug, Clone)]
+pub struct Function {
+	name: Option<ast::Ident>,
+	args: Vec<ast::Ident>,
+	locals: Vec<ast::Ident>,
+	upvalues: Vec<(ast::Ident, Ident)>,
+	body: Vec<Statement>,
+	ret: Box<Expression>,
+}
+
+#[derive(Debug, Clone, Copy)]
+enum Ident {
+	Upvalue(usize),
+	Local(usize),
+	Argument(usize),
+}
+
+#[derive(Debug, Clone)]
+enum Statement {
+	Assign {
+		target: Location,
+		source: Box<Expression>,
+	},
+	Call(Call),
+}
+
+#[derive(Debug, Clone)]
+enum Location {
+	Variable {
+		name: Ident,
+	},
+	Field {
+		table: Box<Location>,
+		index: Box<Expression>,
+	},
+}
+
+#[derive(Debug, Clone)]
+enum Expression {
+	Constant(ast::Constant),
+	Variable(Location),
+	Call(Call),
+	Function(Function),
+}
+
+#[derive(Debug, Clone)]
+struct Call {
+	callee: Location,
+	args: Vec<Expression>,
+}
+
+#[derive(Debug)]
+struct BuildContext<'a> {
+	parent: Option<&'a mut BuildContext<'a>>,
+	upvalues: Vec<(ast::Ident, Ident)>,
+	scope: HashMap<ast::Ident, Ident>,
+}
+
+impl BuildContext<'_> {
+	fn request(&mut self, name: &ast::Ident) -> Option<Ident> {
+		if let Some(ident) = self.scope.get(name) {
+			return Some(*ident);
+		}
+		if let Some(ident) = self.parent.as_mut()?.request(name) {
+			let index = self.upvalues.len();
+			self.upvalues.push((name.clone(), ident));
+			return Some(Ident::Upvalue(index));
+		}
+		None
+	}
+}
+
+pub fn build(code: ast::Function) -> Function {
+	todo!()
+}