No JLS assertion specifying a compile-time error

[Georgiy Rakov]

Hello,

currently javac from JDK9 build 159 fails to compile following modules:
module m1 { exports p; }
module m2 { exports p; }
module m3 {
    required m1
    required m2;
}

./modules/m3/module-info.java:1: error: module m3 reads package p from 
both m1 and m2
module m3 {
^
1 error

Currently lang-vm 
<http://cr.openjdk.java.net/%7Emr/jigsaw/spec/lang-vm.html> doesn't 
specify this behavior, however API documnetation 
<http://cr.openjdk.java.net/%7Emr/jigsaw/spec/api/java/lang/module/Configuration.html#resolveRequires-java.lang.module.ModuleFinder-java.util.List-java.lang.module.ModuleFinder-java.util.Collection-> 
specifies that such error can occur during resolution.

Should lang-vm specify it explicitly as a compile-time error?

Thank you,
Georgiy.