cgen: fix generics struct_init (#9661)

vlib/v/gen/c/cgen.v

@@ -5002,7 +5002,7 @@ fn (mut g Gen) struct_init(struct_init ast.StructInit) {
 		g.go_back_out(3)
 		return
 	}
-	sym := g.table.get_final_type_symbol(struct_init.typ)
+	sym := g.table.get_final_type_symbol(g.unwrap_generic(struct_init.typ))
 	is_amp := g.is_amp
 	is_multiline := struct_init.fields.len > 5
 	g.is_amp = false // reset the flag immediately so that other struct inits in this expr are handled correctly

vlib/v/tests/generics_struct_init_test.v

@@ -0,0 +1,15 @@
+struct Blah {
+mut:
+	arr []string
+}
+
+fn test<T>() T {
+	return T{}
+}
+
+fn test_generics_struct_init() {
+	mut b := test<Blah>()
+	b.arr << 'item'
+	println(b.arr)
+	assert b.arr == ['item']
+}