}
     } else if expr is ast.CastExpr {
         c.check_expr_opt_call(expr.expr, ret_type)
+    } else if expr is ast.AsCast {
+        c.check_expr_opt_call(expr.expr, ret_type)
     }
     return ret_type
 }
         }
         return
     }
-
     if node.stmts.len == 0 {
         if ret_type != ast.void_type {
             // x := f() or {}
                 }
             }
             else {
-                if stmt.typ == ast.void_type {
+                if stmt.typ == ast.void_type || expr_return_type == ast.void_type {
                     return
                 }
                 if is_noreturn_callexpr(stmt.expr) {

new file mode 100644
+vlib/v/checker/tests/as_cast_option_result_unhandled_err.vv:11:6: error: ret_sum_result() returns a result, so it should have either an `or {}` block, or `!` at the end
+    9 | }
+   10 |
+   11 | _ := ret_sum_result() as int
+      |      ~~~~~~~~~~~~~~~~
+   12 | _ := ret_sum_option() as string
+vlib/v/checker/tests/as_cast_option_result_unhandled_err.vv:12:6: error: ret_sum_option() returns an option, so it should have either an `or {}` block, or `?` at the end
+   10 |
+   11 | _ := ret_sum_result() as int
+   12 | _ := ret_sum_option() as string
+      |      ~~~~~~~~~~~~~~~~

new file mode 100644
+type Sum = int | string
+
+fn ret_sum_result() !Sum {
+    return 0
+}
+
+fn ret_sum_option() ?Sum {
+    return '0'
+}
+
+_ := ret_sum_result() as int
+_ := ret_sum_option() as string

 pub fn (mut e Eval) eval(mut files []&ast.File) {
     e.register_symbols(mut files)
     // println(files.map(it.path_base))
-    e.run_func(e.mods['main']['main'] or { ast.EmptyStmt{} } as ast.FnDecl)
+    e.run_func(e.mods['main']['main'] or { ast.FnDecl{} } as ast.FnDecl)
 }
 
 // first arg is reciever (if method)