Bug: Cannot construct a value of type: PlutusTx.Builtins.Internal.BuiltinUnit

plutus-tx-plugin/plutus-tx-plugin.cabal

@@ -134,6 +134,7 @@ test-suite plutus-tx-plugin-tests
     Budget.WithGHCOptimisations
     Budget.WithoutGHCOptimisations
     BuiltinList.Budget.Spec
+    BuiltinUnit.Spec
     ByteStringLiterals.Lib
     ByteStringLiterals.Spec
     DataList.Budget.Spec

plutus-tx-plugin/test/BuiltinUnit/Spec.hs

@@ -0,0 +1,106 @@
+{-# LANGUAGE BlockArguments    #-}
+{-# LANGUAGE DataKinds         #-}
+{-# LANGUAGE NoImplicitPrelude #-}
+{-# LANGUAGE Strict            #-}
+{-# LANGUAGE TemplateHaskell   #-}
+{-# LANGUAGE TypeApplications  #-}
+{-# OPTIONS_GHC -ddump-simpl-iterations -dsuppress-all #-}
+{-# OPTIONS_GHC -fno-float-in #-}
+{-# OPTIONS_GHC -fno-full-laziness #-}
+{-# OPTIONS_GHC -fno-ignore-interface-pragmas #-}
+{-# OPTIONS_GHC -fno-local-float-out #-}
+{-# OPTIONS_GHC -fno-omit-interface-pragmas #-}
+{-# OPTIONS_GHC -fno-spec-constr #-}
+{-# OPTIONS_GHC -fno-specialise #-}
+{-# OPTIONS_GHC -fno-strictness #-}
+{-# OPTIONS_GHC -fno-unbox-small-strict-fields #-}
+{-# OPTIONS_GHC -fno-unbox-strict-fields #-}
+{-# OPTIONS_GHC -fplugin PlutusTx.Plugin #-}
+
+module BuiltinUnit.Spec where
+
+import PlutusTx.Prelude
+import Prelude (IO, seq)
+
+import Control.Lens (view)
+import PlutusTx (CompiledCode, compile, getPlcNoAnn)
+import PlutusTx.Builtins.Internal (unitval)
+import Test.Tasty (TestTree, testGroup)
+import Test.Tasty.HUnit (Assertion, testCase)
+import UntypedPlutusCore (progTerm)
+
+tests :: TestTree
+tests =
+  testGroup
+    "BuiltinUnit"
+    [ testCase "error ()" do assertCompiledTerm code1
+    , testCase "unitval" do assertCompiledTerm code2
+    , testCase "locally defined constructor" do assertCompiledTerm code3
+    , testCase "toOpaque ()" do assertCompiledTerm code4
+    ]
+
+{- GHC Core after simplification:
+
+code1 = case error () of
+  validator1_X0 { BuiltinUnit ipv_smFH -> plc Proxy validator1_X0 }
+
+code2 = case unitval of
+  validator2_X0 { BuiltinUnit ipv_smFJ -> plc Proxy validator2_X0 }
+
+code3 = case unitval of
+  builtinUnit_X0 { BuiltinUnit ipv_smFL -> plc Proxy builtinUnit_X0 }
+
+code4 = case toOpaque $fHasToOpaque()BuiltinUnit () of
+  validator4_X0 { BuiltinUnit ipv_smGp -> plc Proxy validator4_X0 }
+
+Compilation error:
+
+<no location info>: error:
+    GHC Core to PLC plugin:
+    Error: Unsupported feature:
+    Cannot construct a value of type: BuiltinUnit
+    Note: GHC can generate these unexpectedly, you may need
+    '-fno-strictness', '-fno-specialise', '-fno-spec-constr',
+    '-fno-unbox-strict-fields', or '-fno-unbox-small-strict-fields'.
+Context: Compiling expr: BuiltinUnit
+Context: Compiling expr: BuiltinUnit ipv
+Context: Compiling definition of: validator1
+Context: Compiling expr: validator1
+Context: Compiling expr at: test/BuiltinUnit/Spec.hs:75:11-36
+Context: Compiling expr: validator1
+-}
+
+code1 :: CompiledCode BuiltinUnit
+code1 = $$(compile [||validator1||])
+ where
+  validator1 :: BuiltinUnit
+  validator1 = PlutusTx.Prelude.error ()
+  {-# INLINEABLE validator1 #-}
+
+code2 :: CompiledCode BuiltinUnit
+code2 = $$(compile [||validator2||])
+ where
+  validator2 :: BuiltinUnit
+  validator2 = unitval
+  {-# INLINEABLE validator2 #-}
+
+code3 :: CompiledCode BuiltinUnit
+code3 = $$(compile [||validator3||])
+ where
+  validator3 :: BuiltinUnit
+  validator3 = builtinUnit
+  {-# INLINEABLE validator3 #-}
+
+  builtinUnit :: BuiltinUnit
+  builtinUnit = unitval
+  {-# INLINEABLE builtinUnit #-}
+
+code4 :: CompiledCode BuiltinUnit
+code4 = $$(compile [||validator4||])
+ where
+  validator4 :: BuiltinUnit
+  validator4 = toOpaque ()
+  {-# INLINEABLE validator4 #-}
+
+assertCompiledTerm :: CompiledCode a -> Assertion
+assertCompiledTerm code = view progTerm (getPlcNoAnn code) `seq` return @IO ()

plutus-tx-plugin/test/Spec.hs

@@ -6,6 +6,7 @@ import AssocMap.Spec qualified as AssocMap
 import Blueprint.Tests qualified
 import Budget.Spec qualified as Budget
 import BuiltinList.Budget.Spec qualified as BuiltinList.Budget
+import BuiltinUnit.Spec qualified as BuiltinUnit
 import ByteStringLiterals.Spec qualified as ByteStringLiterals
 import DataList.Budget.Spec qualified as DataList.Budget
 import Inline.Spec qualified as Inline
@@ -60,4 +61,5 @@ tests =
     , embed AssocMap.propertyTests
     , embed List.propertyTests
     , Array.smokeTests
+    , embed BuiltinUnit.tests
     ]