tree fc7d75d91e149abe53197ba91e002dd3df75f360
parent 300cff08c7da09260e83f865718bcee831aed9e4
author Joe Tsai <joetsai@digital-static.net> 1553040246 -0700
committer Joe Tsai <thebrokentoaster@gmail.com> 1553190469 +0000

internal/fileinit: prevent map entry descriptors from implementing MessageType

The protobuf type system hacks the representation of map entries into that
of a pseudo-message descriptor.

Previously, we made all message descriptors implement MessageType
where type descriptors had a GoType method that simply returned nil.
Unfortunately, this violates a nice property in the Go type system
where being able to assert to a MessageType guarantees that Go type
information is truly associated with that descriptor.

This CL makes it such that message descriptors for map entries
do not implement MessageType.

Change-Id: I23873cb71fe0ab3c0befd8052830ea6e53c97ca9
Reviewed-on: https://go-review.googlesource.com/c/protobuf/+/168399
Reviewed-by: Damien Neil <dneil@google.com>