Bug: Cannot construct a value of type: PlutusTx.Builtins.Internal.BuiltinUnit
#7162
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…iltin types Add intelligent detection of stage violations when using PlutusTx builtin types. The previous error message "Cannot construct a value of type: BuiltinUnit" was cryptic and unhelpful for users encountering stage violations. This change introduces: - Template Haskell-based detection of builtin types from PlutusTx.Builtins.Internal - Module-aware type checking to avoid false positives - Comprehensive error messages explaining stage violations and how to fix them - Clear guidance on moving functions to top-level scope The improved error message explains the root cause (stage violation), provides actionable solutions (move to top-level, check variable scope), and maintains the original technical context for advanced debugging. This addresses the confusing error reported in plutus-private#1626 while maintaining full compatibility with existing functionality.
Document investigation into disabling mkSimplPass for better error messages. This investigation explored whether removing the GHC simplifier pass could improve error messages for stage violations. While disabling the pass does provide clearer errors, it breaks legitimate plugin functionality that depends on pre-inlining. The investigation concludes that targeted error message improvements (like the stage violation detection) are more practical than removing core functionality. These notes preserve the analysis for future reference and provide context for the chosen approach.
SeungheonOh
reviewed
Jul 25, 2025
| - **Solutions**: | ||
| - Move functions to top-level | ||
| - Generate minimal unfoldings during desugaring (GHC enhancement needed) | ||
| - Create lightweight unfolding pass (lighter than full simplifier) |
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is this possible without making changes to GHC itself? From what I can see(which can be very wrong), we can only really change the plugin pass and the plugin pass doesn't have access to other stages of compilation.
This would be very easy if we have whole compilation pipeline under control.
| OtherCon [] | ||
| ``` | ||
| - **Root cause**: GHC #16615 - local bindings lack unfoldings without simplifier | ||
| - **Pattern**: Functions marked `{-# INLINEABLE #-}` but defined after their use site |
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It's probably also the case for function marked inlineable but defined on the other module.
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Closes https://github.com/IntersectMBO/plutus-private/issues/1626