checker: fix orm cast check (#12018)

vlib/v/checker/checker.v

@@ -7930,6 +7930,10 @@ fn (mut c Checker) sql_expr(mut node ast.SqlExpr) ast.Type {
 	sym := c.table.get_type_symbol(node.table_expr.typ)
 	c.ensure_type_exists(node.table_expr.typ, node.pos) or { return ast.void_type }
 	c.cur_orm_ts = *sym
+	if sym.info !is ast.Struct {
+		c.error('The table symbol `$sym.name` has to be a struct', node.table_expr.pos)
+		return ast.void_type
+	}
 	info := sym.info as ast.Struct
 	fields := c.fetch_and_verify_orm_fields(info, node.table_expr.pos, sym.name)
 	mut sub_structs := map[int]ast.SqlExpr{}

vlib/v/checker/tests/orm_not_a_struct.out

@@ -0,0 +1,7 @@
+vlib/v/checker/tests/orm_not_a_struct.vv:10:15: error: The table symbol `Person` has to be a struct
+    8 |     db := sqlite.connect(':memory:')?
+    9 |     _ := sql db {
+   10 |         select from Person
+      |                     ~~~~~~
+   11 |     }
+   12 | }

vlib/v/checker/tests/orm_not_a_struct.vv

@@ -0,0 +1,12 @@
+import sqlite
+
+enum Person {
+	test
+}
+
+fn main() {
+	db := sqlite.connect(':memory:')?
+	_ := sql db {
+		select from Person
+	}
+}