Reach reparsability of core pretty-printer #1181
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timsueberkrueb
commented
Nov 5, 2025
| //def toDoc(n: Name): Doc = n.toString | ||
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| def toDoc(s: symbols.Symbol): Doc = s.show | ||
| def toDoc(s: symbols.Symbol): Doc = s.name.name ++ "$" ++ s.id.toString |
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$ is a valid character in identifiers, so we need to find another symbol. How about #?
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TIL, I thought we didn't allow it in source exactly for this reason. Does anybody actually use it anywhere [in source]?
timsueberkrueb
commented
Nov 5, 2025
| lazy val externBodyTemplate: P[Template[Expr]] = | ||
| ( | ||
| (multilineString | stringLiteral) ~ | ||
| rep((`++` ~> expr) ~ (`++` ~> (multilineString | stringLiteral))) |
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I chose the syntax "string" ++ (<expr> ++ "string")* for extern body template strings because it is easy to parse. Open to to other suggestions!
timsueberkrueb
commented
Nov 5, 2025
| | failure("Expected an identifier") | ||
| ) | ||
| | failure("Expected an identifier") | ||
| ) |
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Undo some of these spurious white space changes.
timsueberkrueb
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Nov 5, 2025
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Currently, it is very hard to write tests for core. There are two main reasons for this:
While a new core frontend would subsume both of these problems, it is a lot more effort than adding a re-parsable mode to the current core pretty-printer. This would allow us to compile source programs to core and pretty-print them to use them as golden output in core tests.
In particular, when developing the new normalizer (#1127), I would like to track its behavior in unit tests, but they are currently very time-consuming to write due to the fact I cannot just use pretty-printed core for comparison.