polytropos-plugin: TcPlugin that emits literal evidence for Polytropos row classes

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A GHC typechecker plugin for polytropos that solves the evidence-class constraints (Polytropos.Core.FieldIndex, Polytropos.Core.ConstructorIndex, Polytropos.Core.RowEq, Polytropos.Core.RowShow, Polytropos.Core.RowEqSum, Polytropos.Core.RowShowSum, Polytropos.Core.AllFields) by inspecting the row carried in a Polytropos.Core.RowRep's type and emitting literal slot indices, tags, and dictionary vectors directly into GHC Core AST — eliminating inductive type-level search and pointer-chasing runtime overhead entirely.

Uses the ghc-tcplugin-api library for a streamlined interface to GHC's typechecker plugin API across compiler versions.

Start at the front door module Polytropos.Plugin for complete usage instructions and worked examples. Enable in consuming packages via: ghc-options: -fplugin=Polytropos.Plugin.

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Properties

Versions	0.1.0.0, 0.1.0.2
Change log	CHANGELOG.md
Dependencies	base (>=4.18 && <4.23), ghc (>=9.6 && <9.15), ghc-tcplugin-api (>=0.1 && <0.21) [details]
License	(EUPL-1.2 OR Apache-2.0)
Author	Nadia Yvette Chambers
Maintainer	nadia.yvette.chambers@ik.me
Category	Compiler Plugin
Home page	https://github.com/NadiaYvette/polytropos
Bug tracker	https://github.com/NadiaYvette/polytropos/issues
Source repo	head: git clone https://github.com/NadiaYvette/polytropos(packages/polytropos-plugin)
Uploaded	by nyc at 2026-10-17T18:55:12Z

Modules

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Polytropos
- Polytropos.Plugin
  - Polytropos.Plugin.Source

Downloads

polytropos-plugin-0.1.0.0.tar.gz [browse] (Cabal source package)
Package description (as included in the package)

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Readme for polytropos-plugin-0.1.0.0

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polytropos-plugin

GHC typechecker plugin synthesizing literal dictionaries and \(O(1)\) jump tables directly into Core AST for polytropos.

Overview

In traditional Haskell row libraries, solving field offsets or dictionary instances involves either:

Recursive type-level search (\(O(N)\) or \(O(N^2)\) compile-time scaling).
Runtime dictionary passing and pointer chasing.

polytropos-plugin solves evidence constraints (FieldIndex, ConstructorIndex, RowEq, RowShow, RowEqSum, RowShowSum, AllFields) by inspecting the row at compile time and emitting literal slot indices, tags, and dictionary vectors directly into GHC Core AST.

Usage

Enable the plugin in your .cabal file or module:

build-depends:
    polytropos-core >= 0.1 && < 0.2
  , polytropos-plugin >= 0.1 && < 0.2

ghc-options: -fplugin=Polytropos.Plugin

Features

Literal Offset Resolution: Solves FieldIndex @"foo" r directly to integer slot literals.
Literal Tag Resolution: Solves ConstructorIndex @"Bar" s directly to integer constructor tags.
Unrolled Core Synthesis: Direct code generation for record equality (RowEq) and formatting (RowShow).
Human-Centric Error Diagnostics: Custom TypeError reporting with Levenshtein-distance fuzzy field name suggestions when fields or constructors are missing.
Cross-GHC Support: Supports GHC 9.6 through GHC 9.14 via internal compatibility shims.

Documentation & Repository

Main Repository: https://github.com/NadiaYvette/polytropos
Plugin Architecture: PLUGIN_INVARIANTS.md

License

Dual-licensed under EUPL-1.2 OR Apache-2.0.