To reproduce the issue execute test:
test/tools/javac/T8159970/TypeEqualityInInferenceTest.java

with this command from a langtools repo:

~/jtreg/bin/jtreg -vmoption:-Xmx512m -jdk:/path/to/jdk1.9.0/ -vmoption:-ea:com.sun.tools... -javacoptions:-g -r:jtregOut/JTreport -w:jtregOut/JTwork -ignore:quiet -samevm -Xpatch:java.compiler="build/modules/java.compiler" -Xpatch:jdk.compiler="build/modules/jdk.compiler" -Xpatch:jdk.javadoc="build/modules/jdk.javadoc" -Xpatch:jdk.jdeps="build/modules/jdk.jdeps" -Xpatch:jdk.jshell="build/modules/jdk.jshell" test/tools/javac/T8159970/TypeEqualityInInferenceTest.java

the generated file will have 3 rerun sections 2 for compilation and the last one for test execution, the last one is the one that is not updated for modules.

the corresponding rerun command obtained with othervm mode is more complete but there is an error at execution time.