Use HLint. (#1045)

.github/workflows/hlint.yml

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+name: HLint
+on: [push, pull_request]
+
+jobs:
+  hlint:
+    runs-on: ubuntu-latest
+    permissions:
+      # Needed to upload results to GitHub code scanning.
+      security-events: write
+    steps:
+      - uses: actions/checkout@v4
+      - uses: haskell-actions/hlint-scan@v1

.hlint.yaml

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+# HLint configuration file
+# https://github.com/ndmitchell/hlint
+##########################
+
+# This file contains a template configuration file, which is typically
+# placed as .hlint.yaml in the root of your project
+
+
+# Warnings currently triggered by your code
+- ignore: {name: "Evaluate"} # 1 hint
+- ignore: {name: "Functor law"} # 1 hint
+- ignore: {name: "Parse error: on input `pattern'"} # 11 hints
+- ignore: {name: "Redundant $"} # 8 hints
+- ignore: {name: "Redundant bracket"} # 11 hints
+- ignore: {name: "Redundant lambda"} # 1 hint
+- ignore: {name: "Redundant seq"} # 2 hints
+- ignore: {name: "Traversable law"} # 1 hint
+- ignore: {name: "Unused LANGUAGE pragma"} # 6 hints
+- ignore: {name: "Use ++"} # 3 hints
+- ignore: {name: "Use :"} # 1 hint
+- ignore: {name: "Use <$>"} # 8 hints
+- ignore: {name: "Use <&>"} # 3 hints
+- ignore: {name: "Use asks"} # 23 hints
+- ignore: {name: "Use concatMap"} # 1 hint
+- ignore: {name: "Use fewer imports"} # 6 hints
+- ignore: {name: "Use fmap"} # 7 hints
+- ignore: {name: "Use forM_"} # 1 hint
+- ignore: {name: "Use gets"} # 5 hints
+- ignore: {name: "Use intercalate"} # 1 hint
+- ignore: {name: "Use lambda-case"} # 11 hints
+- ignore: {name: "Use list comprehension"} # 1 hint
+- ignore: {name: "Use newtype instead of data"} # 2 hints
+- ignore: {name: "Use notElem"} # 1 hint
+- ignore: {name: "Use section"} # 1 hint
+- ignore: {name: "Use span"} # 1 hint
+- ignore: {name: "Use typeRep"} # 4 hints
+
+
+# Specify additional command line arguments
+#
+# - arguments: [--color, --cpp-simple, -XQuasiQuotes]
+
+
+# Control which extensions/flags/modules/functions can be used
+#
+# - extensions:
+#   - default: false # all extension are banned by default
+#   - name: [PatternGuards, ViewPatterns] # only these listed extensions can be used
+#   - {name: CPP, within: CrossPlatform} # CPP can only be used in a given module
+#
+# - flags:
+#   - {name: -w, within: []} # -w is allowed nowhere
+#
+# - modules:
+#   - {name: [Data.Set, Data.HashSet], as: Set} # if you import Data.Set qualified, it must be as 'Set'
+#   - {name: Control.Arrow, within: []} # Certain modules are banned entirely
+#
+# - functions:
+#   - {name: unsafePerformIO, within: []} # unsafePerformIO can only appear in no modules
+
+
+# Add custom hints for this project
+#
+# Will suggest replacing "wibbleMany [myvar]" with "wibbleOne myvar"
+# - error: {lhs: "wibbleMany [x]", rhs: wibbleOne x}
+
+# The hints are named by the string they display in warning messages.
+# For example, if you see a warning starting like
+#
+# Main.hs:116:51: Warning: Redundant ==
+#
+# You can refer to that hint with `{name: Redundant ==}` (see below).
+
+# Turn on hints that are off by default
+#
+# Ban "module X(module X) where", to require a real export list
+# - warn: {name: Use explicit module export list}
+#
+# Replace a $ b $ c with a . b $ c
+# - group: {name: dollar, enabled: true}
+#
+# Generalise map to fmap, ++ to <>
+# - group: {name: generalise, enabled: true}
+#
+# Warn on use of partial functions
+# - group: {name: partial, enabled: true}
+
+
+# Ignore some builtin hints
+# - ignore: {name: Use let}
+# - ignore: {name: Use const, within: SpecialModule} # Only within certain modules
+
+
+# Define some custom infix operators
+# - fixity: infixr 3 ~^#^~
+
+
+# To generate a suitable file for HLint do:
+# $ hlint --default > .hlint.yaml