tree 28d07a8f175fd475bc07cf27f329c43113fbc18b
parent 93adb37c0ddd0e5862c3e4341d0b0e9a31ec08af
author Henner Zeller <h.zeller@acm.org> 1748688087 +0200
committer Henner Zeller <h.zeller@acm.org> 1748700679 +0200

Don't use down_cast<> with the assumption that type-mismatch returns null.

We typically don't compile-in RTTI so relying on down_cast<> returning
nullptr or a correct type will result in subtle issues.

Instead, provide MaybeNode() and MaybeLeaf() that use the SymbolKind
to provide such casts.

This should be expanded:
  * Ideally we remove _all_ uses of down_cast<> and use type-safe
    ways of doing the same thing (and then: remove verible::down_cast<>).
  * There are a few places where we CHECK() fail on type-mismatch, assuming
    these can't happen; but that depends on how valid our syntax tree is,
    which depends on the input the the parser to reject such input. These
    should be reformulated with graceful error handling.

Fixes #2419