add type check

include/ast/passes/type_check.h

@@ -13,6 +13,7 @@ class TypeCheck : public Pass {
    public:
     explicit TypeCheck();
     void visit_declaration(shared_ptr<ast::Declaration>) override;
+    void visit_assignment(shared_ptr<ast::Assignment>) override;
     void visit_function(shared_ptr<ast::Function>) override;
     void visit_call(shared_ptr<ast::Call>) override;
     void visit_return(shared_ptr<ast::Return>) override;

src/ast/passes/type_check.cpp

@@ -18,6 +18,19 @@ void TypeCheck::visit_declaration(shared_ptr<ast::Declaration> node) {
     }
 }
 
+void TypeCheck::visit_assignment(shared_ptr<ast::Assignment> node) {
+    visit(node->var);
+    visit(node->expr);
+
+    Type var = *node->var->get_type();
+    Type expr = *node->expr->get_type();
+    if (var != expr) {
+        throw TypeError(node->token->getLine(),
+                        "mismatched lhs(" + var.get_name() + ") and rhs(" +
+                            expr.get_name() + ") types on assignment");
+    }
+}
+
 void TypeCheck::visit_function(shared_ptr<ast::Function> node) {
     for (const auto& param : node->params) {
         visit(param);

tests/input/errors/type/assignment.in

@@ -0,0 +1,6 @@
+fn main(): i32 {
+    let x: i32 = 5;
+    x = 'a';
+
+    return 0;
+}

tests/output/errors/type/assignment.out

@@ -0,0 +1 @@
+TypeError on Line 3