reproduction: Use of fromString @BuiltinByteStringHex with inscrutable content

[Unisay]

Related to https://github.com/IntersectMBO/plutus-private/issues/1480

[Unisay]

Peculiar fact: with this compiler option the error is:

    GHC Core to PLC plugin: Error: 
    Unexpected error during compilation, please report this to the Plutus team:
    Use of fromString @PlutusTx.Builtins.HasOpaque.BuiltinByteStringHex with inscrutable content: 
    GHC.Types.: @GHC.Types.Char 
      (GHC.Types.C# 'f'#) 
      (GHC.Base.build @GHC.Types.Char (\ (@b) -> GHC.CString.unpackFoldrCString# @b "0"#))

but without it the error is different (even more confusing):

GHC Core to PLC plugin: Error: Unsupported feature: 
Literal string (maybe you need to use OverloadedStrings)
Context: Compiling expr: "f0"#
Context: Compiling expr: GHC.Base.build
                           @GHC.Types.Char
                           (\ (@b) -> GHC.CString.unpackFoldrCString# @b "f0"#)

[zliu41]

There's no reason to put {-# OPTIONS_GHC -fplugin PlutusTx.Plugin #-} in this module.
@Unisay can you post the entire GHC core for this module?

[Unisay]

Without this pragma the GHC's recompilation avoidance mechanism would not recompile this module whenever something in the plugin changes; For this reason I always add it in tests.

However, my point was different: the presence/absense of this pragrma does change the compilation error, while my expectation was that it shouldn't make any difference.

can you post the entire GHC core for this module?

Sure.

==================== Tidy Core ====================
Result size of Tidy Core
  = {terms: 23, types: 8, coercions: 2, joins: 0/0}

-- RHS size: {terms: 1, types: 0, coercions: 0, joins: 0/0}
ByteStringLiterals.Lib.$trModule4 :: ghc-prim:GHC.Prim.Addr#
[GblId,
 Unf=Unf{Src=<vanilla>, TopLvl=True,
         Value=True, ConLike=True, WorkFree=True, Expandable=True,
         Guidance=IF_ARGS [] 150 0}]
ByteStringLiterals.Lib.$trModule4
  = "plutus-tx-plugin-1.42.0.0-inplace-plutus-tx-plugin-tests"#

-- RHS size: {terms: 2, types: 0, coercions: 0, joins: 0/0}
ByteStringLiterals.Lib.$trModule3 :: ghc-prim:GHC.Types.TrName
[GblId,
 Unf=Unf{Src=<vanilla>, TopLvl=True,
         Value=True, ConLike=True, WorkFree=True, Expandable=True,
         Guidance=IF_ARGS [] 10 10}]
ByteStringLiterals.Lib.$trModule3
  = ghc-prim:GHC.Types.TrNameS ByteStringLiterals.Lib.$trModule4

-- RHS size: {terms: 1, types: 0, coercions: 0, joins: 0/0}
ByteStringLiterals.Lib.$trModule2 :: ghc-prim:GHC.Prim.Addr#
[GblId,
 Unf=Unf{Src=<vanilla>, TopLvl=True,
         Value=True, ConLike=True, WorkFree=True, Expandable=True,
         Guidance=IF_ARGS [] 70 0}]
ByteStringLiterals.Lib.$trModule2 = "ByteStringLiterals.Lib"#

-- RHS size: {terms: 2, types: 0, coercions: 0, joins: 0/0}
ByteStringLiterals.Lib.$trModule1 :: ghc-prim:GHC.Types.TrName
[GblId,
 Unf=Unf{Src=<vanilla>, TopLvl=True,
         Value=True, ConLike=True, WorkFree=True, Expandable=True,
         Guidance=IF_ARGS [] 10 10}]
ByteStringLiterals.Lib.$trModule1
  = ghc-prim:GHC.Types.TrNameS ByteStringLiterals.Lib.$trModule2

-- RHS size: {terms: 3, types: 0, coercions: 0, joins: 0/0}
ByteStringLiterals.Lib.$trModule :: ghc-prim:GHC.Types.Module
[GblId,
 Unf=Unf{Src=<vanilla>, TopLvl=True,
         Value=True, ConLike=True, WorkFree=True, Expandable=True,
         Guidance=IF_ARGS [] 10 10}]
ByteStringLiterals.Lib.$trModule
  = ghc-prim:GHC.Types.Module
      ByteStringLiterals.Lib.$trModule3 ByteStringLiterals.Lib.$trModule1

-- RHS size: {terms: 6, types: 1, coercions: 0, joins: 0/0}
ByteStringLiterals.Lib.hex1 [InlPrag=INLINABLE]
  :: PlutusTx.Builtins.Internal.BuiltinByteString
[GblId,
 Unf=Unf{Src=StableUser, TopLvl=True,
         Value=False, ConLike=False, WorkFree=False, Expandable=False,
         Guidance=IF_ARGS [] 80 0
         Tmpl= src<test/ByteStringLiterals/Lib.hs:12:1-10>
               PlutusTx.Builtins.HasOpaque.stringToBuiltinByteStringHex
                 (ghc-prim:GHC.Types.:
                    @ghc-prim:GHC.Types.Char
                    (ghc-prim:GHC.Types.C# 'f'#)
                    (GHC.Base.build
                       @ghc-prim:GHC.Types.Char
                       (\ (@b_iafj) ->
                          ghc-prim:GHC.CString.unpackFoldrCString# @b_iafj "0"#)))}]
ByteStringLiterals.Lib.hex1
  = src<test/ByteStringLiterals/Lib.hs:12:1-10>
    PlutusTx.Builtins.HasOpaque.stringToBuiltinByteStringHex
      (ghc-prim:GHC.Types.:
         @ghc-prim:GHC.Types.Char
         (ghc-prim:GHC.Types.C# 'f'#)
         (ghc-prim:GHC.CString.unpackCString# "0"#))

-- RHS size: {terms: 1, types: 0, coercions: 2, joins: 0/0}
hex [InlPrag=INLINABLE] :: BuiltinByteStringHex
[GblId,
 Unf=Unf{Src=<vanilla>, TopLvl=True,
         Value=False, ConLike=False, WorkFree=True, Expandable=True,
         Guidance=ALWAYS_IF(arity=0,unsat_ok=True,boring_ok=True)}]
hex
  = ByteStringLiterals.Lib.hex1
    `cast` (Sym (PlutusTx.Builtins.HasOpaque.N:BuiltinByteStringHex[0])
            :: PlutusTx.Builtins.Internal.BuiltinByteString
               ~R# BuiltinByteStringHex)