Suggestion for a more useful error message for template field duplication
This looks like a side effect of the following being valid Haskell program:
{-# LANGUAGE DuplicateRecordFields, DisambiguateRecordFields #-}
module Test where
data X = X { a :: Int, a :: Int }
I don’t actually know why this is valid. DuplicateRecordFields is supposed to allow for duplicate fields in different records, I don’t see why it’s valid within the same record.
The case that blows up in your example is then not the definition of the datatype but one of the generated methods for things like choices, signatories, … which is why the l ocation is off.
We could probably add our own check here. I opened Better errors on duplicate record fields · Issue #8994 · digital-asset/daml · GitHub to track this.
Thank you!
We just merged an improvement here. The following template
template T
with
a : Int
a : Bool
p : Party
where
signatory p
now produces the error:
File: daml/Main.daml
Hidden: no
Range: 8:5-8:6
Source: parser
Severity: DsError
Message: Duplicate field name a. Original definition at daml/Main.daml:7:5.
which highlights the duplicate field and shows you the location of the first field definition.
Thank you, does it also highlight the error when the fields with identical names have the same type? Actually this was the case when I encountered the error, I copy+pasted the list of fields from another template, and there was an overlap so I copied the field twice.
To set expectations, it’s worth mentioning that, as this just missed the 1.11 RC train, this improvement will not be included in the stable Daml Connect 1.11 release, but will (likely) be included in the first snapshot of the 1.12 development cycle, which should be created around the second half of next week.
