Frequent crashes on Windows with Assertion failed: IDAndOffset.first.isValid() && "invalid FileID for transition"

[z2oh]

Assertion failed: IDAndOffset.first.isValid() && "invalid FileID for transition", file C:\a\swift-build\swift-build\SourceCache\llvm-project\clang\lib\Serialization\ASTReader.cpp, line 6609

The assertion in question: https://github.com/apple/llvm-project/blob/51859f9280134994d482f8420619760409903585/clang/lib/Serialization/ASTReader.cpp#L6675

We're seeing this happen frequently enough to hit the 6 crashes in 3 minutes no-restart limit.

This may not be actually be a sourcekit-lsp issue, but as it materializes as a crash I figured it was worth flagging here.

[ahoppen]

Tracked in Apple’s issue tracker as rdar://125018783

[ahoppen]

Do you have a crash trace of the call stack that caused the assertion failure?