rebel-lang: scope: add Context::record_type()

Add a function for incrementally typechecking a list of statements,
without actually evaluating it.

1 files changed, 36 insertions, 3 deletions

diff --git a/crates/rebel-lang/src/scope.rs b/crates/rebel-lang/src/scope.rs
index 3fd7c99..a030f47 100644
--- a/crates/rebel-lang/src/scope.rs
+++ b/crates/rebel-lang/src/scope.rs
@@ -4,7 +4,7 @@ use rebel_parse::ast;
 
 use crate::{
 	func::Func,
-	typing::{Type, TypeFamily},
+	typing::{self, Type, TypeError, TypeFamily},
 	value::{self, EvalError, Value},
 };
 
@@ -15,13 +15,46 @@ pub struct Context {
 }
 
 impl Context {
+	pub fn record_type(&mut self, stmt: &ast::BodyStmt) -> typing::Result<Type> {
+		match stmt {
+			ast::BodyStmt::Assign { dest, expr } => {
+				let typ = Type::ast_expr_type(self, expr)?;
+
+				// TODO: Handle explicit type
+				let ast::TypedExpr {
+					expr: dest_expr,
+					typ: _,
+				} = dest;
+
+				// TODO: Handle other assignable expressions
+				let dest_path = match dest_expr {
+					ast::Expr::Path(path) => path,
+					_ => return Err(TypeError),
+				};
+				let [dest_ident] = dest_path.components[..] else {
+					return Err(TypeError);
+				};
+
+				// TODO: Lexical scoping
+				self.values.0.insert(
+					dest_ident.name.to_owned(),
+					ModuleEntry::Def((typ.clone(), None)),
+				);
+
+				Ok(typ)
+			}
+			ast::BodyStmt::Expr { expr } => Type::ast_expr_type(self, expr),
+			ast::BodyStmt::Empty => Ok(Type::Unit),
+		}
+	}
+
 	pub fn execute(&mut self, stmt: &ast::BodyStmt) -> value::Result<Value> {
 		match stmt {
 			ast::BodyStmt::Assign { dest, expr } => {
 				let value = Value::eval(self, expr)?;
 				let typ = value.typ().or(Err(EvalError))?;
 
-				// TODO: Handle specified type
+				// TODO: Handle explicit type
 				let ast::TypedExpr {
 					expr: dest_expr,
 					typ: _,
@@ -39,7 +72,7 @@ impl Context {
 				// TODO: Lexical scoping
 				self.values.0.insert(
 					dest_ident.name.to_owned(),
-					ModuleEntry::Def((typ, (Some(value.clone())))),
+					ModuleEntry::Def((typ, Some(value.clone()))),
 				);
 
 				Ok(value)