Allow error messages in parsing (for debugging)

And fix an off-by-one in day 5

1 files changed, 1 insertions, 1 deletions

diff --git a/Common/DayPart.lean b/Common/DayPart.lean
index c6a4d44..a701272 100644
--- a/Common/DayPart.lean
+++ b/Common/DayPart.lean
@@ -6,7 +6,7 @@ inductive Parts
 | Two
 
 class Parse (day : Days) {ι : outParam Type} where
-  parse : String → Option ι
+  parse : String → Except String ι
 
 class Part (day : Days) (part : Parts) {ι ρ : outParam Type} [Parse day (ι := ι)] [ToString ρ] where
   run : ι → Option ρ -- can fail, because it deals with user input...