[jdk11u-dev] RFR: 8210649: AssertionError @ jdk.compiler/com.sun.tools.javac.comp.Modules.enter(Modules.java:244)

[Basil Crow]

Hi all,

This pull request contains a clean backport of commit [44ae643b2b49b66b1fff4c151c17972c6b683cc0](https://github.com/openjdk/jdk/commit/44ae643b2b4) from the [openjdk/jdk](https://git.openjdk.java.net/jdk) repository.

The commit being backported was authored by Jan Lahoda on June 1, 2020, and was reviewed by Vicente Romero.

See [JDK-8210649](https://bugs.openjdk.java.net/browse/JDK-8210649) and [MCOMPILER-346](https://issues.apache.org/jira/browse/MCOMPILER-346) for more information.

Thanks!

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Commit messages:
 - Backport 44ae643b2b49b66b1fff4c151c17972c6b683cc0

Changes: https://git.openjdk.java.net/jdk11u-dev/pull/919/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk11u-dev&pr=919&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8210649
  Stats: 176 lines in 3 files changed: 161 ins; 8 del; 7 mod
  Patch: https://git.openjdk.java.net/jdk11u-dev/pull/919.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk11u-dev pull/919/head:pull/919

PR: https://git.openjdk.java.net/jdk11u-dev/pull/919