Implement a new generic expression AST to use with future parsers #633
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doriable
approved these changes
Nov 20, 2025
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This PR adds
experimental/expr, a new AST for generic expressions, which is capable of representing (at minimum) both Protobuf and CEL expressions, along with many other potential syntaxes.This is intended to unify our expression parsing framework; eventually, it should ideally replace the
ast.Expr*types, but that is not a short-term goal for this package. For now, it will be used as a testing ground for a new stand-alone expression language.This PR also includes an
internal/exprxpackage which provides an expression serialization mechanism for use in tests, similar toastx.ToProto. It also includes new keywords, which do not have corresponding taxa; that will be rectified as part of the work to implement the parser.Finally, I've added
Trie.Prefixes, which allows iterating over all prefixes of a string in a trie. This is necessary in the lexer so that the keyword we select in the lexer does not wind up being the longest prefix among all keywords, not just those the lexer configuration accepts.