[PATCH] D52513: [Modules] Do not emit file modification error when -fno-validate-pch is set

[Richard Smith - zygoloid via Phabricator via cfe-commits]

rsmith added a comment.

The consequence of this will be that we use a stale PCH / PCM file if files have changed, rather than emitting an "out of date" error if / when we decide we need to reference a modified file that was used to build the AST file. That can lead to bad things happening: any time we decide to re-lex or otherwise go back to the original source file, we'll be "surprised" that it's not the same as we remember it being. `-fno-validate-pch` isn't supposed to allow the files on disk to have changed, it's a promise that they haven't.


https://reviews.llvm.org/D52513