no error or warning using new module with old version of Ceylon

[jvasileff]

New modules (e.g. modules compiled against 1.3.2) may use 1.3.2 features, and therefore should not be usable without some sort of error, warning, or special flag with older versions of Ceylon (e.g. 1.3.1). Or, more precisely, older versions of the language module.

A module with

module simple "1.0.0" {
    import ceylon.collection "1.3.2";
}

compiles and runs without a compatibility error using the 1.3.0 and 1.3.1 dists.

The program

import ceylon.collection {...}

shared void run() {
    print("hello");
    print(ArrayList());
}

does however fail at runtime on 1.3.0 with

jvasileff@tau:tmp.J0YFhXtJ$ swceylon 1.3.0
jvasileff@tau:tmp.J0YFhXtJ$ ceylon compile
ceylon run simNote: Created module simple/1.0.0
jvasileff@tau:tmp.J0YFhXtJ$ ceylon run simple
hello
Exception in thread "main" java.lang.LinkageError: loader constraint violation: loader (instance of ceylon/modules/jboss/runtime/CeylonModuleClassLoader) previou
sly initiated loading for a different type with name "com/redhat/ceylon/compiler/java/runtime/model/TypeDescriptor"
        at java.lang.ClassLoader.defineClass1(Native Method)
        at java.lang.ClassLoader.defineClass(ClassLoader.java:763)
        at org.jboss.modules.ModuleClassLoader.doDefineOrLoadClass(ModuleClassLoader.java:353)
        at org.jboss.modules.ModuleClassLoader.defineClass(ModuleClassLoader.java:432)