HasField instance for generic variant types used over a data-dependency is not found by LF typechecker.

This is in a package dependency configuration where one package depends on two others, as a data dependency.

        package 3
          /    \
    data /      \ data
        /        \
package 1       package 2

When defining a two-parameter class within package 3 and an instance of it that links a type from package 1 to one from package 2, the LF typecheck fails (after a successful GHC type check/inference). Suspected cause: attempt to specialise the instance code. But note that no concrete instance is known in this code, all types still have type parameters.

Note that this compiles fine when the dependencies between the packages are full (not data-) dependencies.

data-depend-triangle $ ll
total 20
drwxr-xr-x  5 jost jost 4096 Aug 31 18:03 ./
drwxr-xr-x 13 jost jost 4096 Aug 31 18:02 ../
drwxr-xr-x  4 jost jost 4096 Aug 31 18:10 package1/
drwxr-xr-x  4 jost jost 4096 Aug 31 18:10 package2/
drwxr-xr-x  4 jost jost 4096 Sep  1 09:41 package3/
data-depend-triangle $ more package?/daml.yaml
::::::::::::::
package1/daml.yaml
::::::::::::::
sdk-version: 1.4.0
name: package1
version: 0.0.1000
parties:
  - 00001
dependencies:
- daml-prim
- daml-stdlib
source: src
::::::::::::::
package2/daml.yaml
::::::::::::::
sdk-version: 1.4.0
name: package2
version: 0.0.1000
parties:
  - 00001
dependencies:
- daml-prim
- daml-stdlib
source: src/
::::::::::::::
package3/daml.yaml
::::::::::::::
sdk-version: 1.4.0
name: package3
version: 0.0.1000
parties:
  - 00001
dependencies:
- daml-prim
- daml-stdlib
data-dependencies:
- ../package1/.daml/dist/package1-0.0.1000.dar
- ../package2/.daml/dist/package2-0.0.1000.dar
source: src
data-depend-triangle $ more package?/src/*daml
::::::::::::::
package1/src/Package1File.daml
::::::::::::::
module Package1File where

data AVariant x y = V1 with theX: x
                  | V2 with theYs: [y]
::::::::::::::
package2/src/Package2File.daml
::::::::::::::
module Package2File where

-- identical to the definition in Package1File
data AVariant x y = V1 with theX: x
                  | V2 with theYs: [y]
::::::::::::::
package3/src/Package3File.daml
::::::::::::::
daml 1.2
module Package3File where

import Package1File qualified as P1
import Package2File qualified as P2

class Convert a b where
  convert : a -> b

instance Convert a a' => Convert [a] [a'] where
  convert = fmap convert

instance (Convert x x', Convert y y') =>
         Convert (P1.AVariant x y) (P2.AVariant x' y') where
  convert = \a -> case a of
            P1.V1{} ->
              P2.V1 with
                theX = convert a.theX
            P1.V2{} ->
              P2.V2 with
                theYs = convert a.theYs
data-depend-triangle $ for i in 1 2 3; do (cd package$i && daml build); done
Compiling package1 to a DAR.
Created .daml/dist/package1-0.0.1000.dar
Compiling package2 to a DAR.
Created .daml/dist/package2-0.0.1000.dar
Compiling package3 to a DAR.
File:     src/Package3File.daml
Hidden:   no
Range:    1:0-100001:0
Source:   DAML-LF typechecker
Severity: DsError
Message: 
  error type checking value Package3File.$cconvert1:
  unknown value:
  e196c7990292b3791ab23cab64be3c89edcd06e3707efa7896d504c5ab29f3b4:Package1File:$fHasField"theX"AVariantx_ait
ERROR: Creation of DAR file failed.
data-depend-triangle $ 

[sofiafaro-da]

Looks like the generated names are in the typechecked ast (-ddump-tc-ast).

[hurryabit]

@jberthold-da We fixed this particular issue. It will be part of SDK 1.6.0.