Make it compile with MicroHs

.github/workflows/mhs-ci.yml

@@ -0,0 +1,59 @@
+name: ci-mhs
+
+on:
+  push:
+    branches: [ "master" ]
+  pull_request:
+    branches: [ "master" ]
+
+jobs:
+  build-mhs-mtl:
+    runs-on: ubuntu-latest
+    steps:
+
+    - name: checkout mhs repo
+      uses: actions/checkout@v4
+      with:
+        repository: augustss/MicroHs
+        ref: stable-6
+        path: mhs
+    - name: make and install mhs
+      run: |
+        cd mhs
+        make minstall
+
+    - name: checkout transformers repo
+      uses: actions/checkout@v4
+      with:
+        repository: augustss/transformers
+        path: transformers
+    - name: compile and install transformers package
+      run: |
+        PATH="$HOME/.mcabal/bin:$PATH"
+        cd transformers
+        mcabal install
+
+    - name: checkout mtl repo
+      uses: actions/checkout@v4
+      with:
+        repository: augustss/mtl
+        path: mtl
+    - name: compile and install mtl package
+      run: |
+        PATH="$HOME/.mcabal/bin:$PATH"
+        cd mtl
+        mcabal install
+
+    - name: checkout parsec repo
+      uses: actions/checkout@v4
+      with:
+        path: parsec
+    - name: compile and install parsec package
+      run: |
+        PATH="$HOME/.mcabal/bin:$PATH"
+        cd parsec
+        mcabal install
+
+    - name: cleanup
+      run: |
+        rm -rf $HOME/.mcabal

parsec.cabal

@@ -67,8 +67,7 @@ library
         base       >= 4.12.0.0 && < 4.21,
         mtl        >= 2.2.2    && < 2.4,
         bytestring >= 0.10.8.2 && < 0.13,
-        text      (>= 1.2.3.0  && < 1.3)
-               || (>= 2.0 && < 2.2)
+        text      (>= 1.2.3.0  && < 1.3) || (>= 2.0 && < 2.2)
 
     default-language: Haskell2010
     other-extensions:
@@ -86,7 +85,7 @@ library
         UndecidableInstances
 
     ghc-options: -Wall
-    if impl(ghc >= 8.0)
+    if impl(ghc >= 8.0) || impl(mhs)
         ghc-options: -Wcompat -Wnoncanonical-monad-instances -Wno-trustworthy-safe
         if impl(ghc < 8.8)
           ghc-options: -Wnoncanonical-monadfail-instances

src/Text/Parsec/Token.hs

@@ -1,5 +1,6 @@
 {-# LANGUAGE FlexibleContexts #-}
 {-# LANGUAGE PolymorphicComponents #-}
+{-# LANGUAGE ScopedTypeVariables #-}
 {-# LANGUAGE Safe #-}
 
 -----------------------------------------------------------------------------
@@ -348,7 +349,7 @@ data GenTokenParser s u m
 -- >  reserved    = P.reserved lexer
 -- >  ...
 
-makeTokenParser :: (Stream s m Char)
+makeTokenParser :: forall s m u . (Stream s m Char)
                 => GenLanguageDef s u m -> GenTokenParser s u m
 {-# INLINABLE makeTokenParser #-}
 makeTokenParser languageDef
@@ -390,6 +391,8 @@ makeTokenParser languageDef
     -----------------------------------------------------------
     -- Bracketing
     -----------------------------------------------------------
+    parens, braces, angles, brackets
+                   :: forall a. ParsecT s u m a -> ParsecT s u m a
     parens p        = between (symbol "(") (symbol ")") p
     braces p        = between (symbol "{") (symbol "}") p
     angles p        = between (symbol "<") (symbol ">") p
@@ -400,6 +403,8 @@ makeTokenParser languageDef
     dot             = symbol "."
     colon           = symbol ":"
 
+    commaSep, semiSep, commaSep1, semiSep1
+                   :: forall a. ParsecT s u m a -> ParsecT s u m [a]
     commaSep p      = sepBy p comma
     semiSep p       = sepBy p semi
 
@@ -681,6 +686,7 @@ makeTokenParser languageDef
     symbol name
         = lexeme (string name)
 
+    lexeme :: forall a. ParsecT s u m a -> ParsecT s u m a
     lexeme p
         = do{ x <- p; whiteSpace; return x  }