Invalid SDF3 source directory expression results in an exception

[molenzwiebel]

Summary

Setting an invalid main-source-directory in spoofaxc.cfg results in an exception.

What you did

sdf3 {
  source = files {
    main-source-directory = 1
  }
}

What you expected to happen

Statix error.

What actually happened

An internal error occurred during: "CFG editor update".
BUG: invalid AST shape, expected string or String/Path/JavaId/SortId/StrategyId application in AST: UInt("1"{TermIndex("eclipse-resource##/dynamix/spoofaxc.cfg",10)}){TermIndex("eclipse-resource##/dynamix/spoofaxc.cfg",11)}

Context

• Spoofax version: devenv, spoofax-pie commit bb75f54
• Operating system & version: Windows

[Gohla]

There's a whole class of errors like these. The issue is that the code that converts from the CFG to a configuration object runs regardless of whether the static semantics finds any errors. The reason for this is that I'd like to be able to produce a configuration object even in case of errors (i.e., error recovery).

However, that would require many error checks across the entire conversion code, so maybe this was a bad idea and this should be reverted. That would require splitting out errors that are produced on the Java side (e.g., whether directories/files exist) to separate code that does run alongside static semantics, and the conversion code which can assume that all checks have passed.

[Gohla]

Fixed by b4a108e.