Initial commit.

.gitignore

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+.stack-work/
+dist/
+# Generated automatically by hpack:
+*.cabal

CONTRIBUTING.md

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+# How to Contribute
+
+We'd love to accept your patches and contributions to this project. There are
+just a few small guidelines you need to follow.
+
+## Contributor License Agreement
+
+Contributions to this project must be accompanied by a Contributor License
+Agreement. You (or your employer) retain the copyright to your contribution;
+this simply gives us permission to use and redistribute your contributions as
+part of the project. Head over to <https://cla.developers.google.com/> to see
+your current agreements on file or to sign a new one.
+
+You generally only need to submit a CLA once, so if you've already submitted one
+(even if it was for a different project), you probably don't need to do it
+again.
+
+## Code reviews
+
+All submissions, including submissions by project members, require review. We
+use GitHub pull requests for this purpose. Consult
+[GitHub Help](https://help.github.com/articles/about-pull-requests/) for more
+information on using pull requests.
+
+## Community Guidelines
+
+This project follows
+[Google's Open Source Community Guidelines](https://opensource.google.com/conduct/).

ChangeLog.md

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+# Changelog for haskell-syntax
+
+## Unreleased changes

LICENSE

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+Copyright 2019 Google LLC
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are
+met:
+
+   * Redistributions of source code must retain the above copyright
+notice, this list of conditions and the following disclaimer.
+   * Redistributions in binary form must reproduce the above
+copyright notice, this list of conditions and the following disclaimer
+in the documentation and/or other materials provided with the
+distribution.
+
+   * Neither the name of Google LLC nor the names of its
+contributors may be used to endorse or promote products derived from
+this software without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

README.md

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+# ghc-source-gen
+
+`ghc-source-gen` is a Haskell library for constructing Haskell syntax trees using the GHC API.  This package is compatible with multiple versions of GHC: currently,= 8.2, 8.4, 8.6, and 8.8.
+
+This is not an officially supported Google product.
+
+## Example
+
+This example constructs and prints a module defining the
+`const` function:
+
+```haskell
+{-# LANGUAGE OverloadedStrings #-}
+{-# LANGUAGE NoMonomorphismRestriction #-}
+import GHC.SourceGen
+import GHC.Paths (libdir)
+
+constModule :: HsModule'
+constModule =
+    module' (Just "Const") (Just [var "const"]) []
+        [ typeSig "const" $ a --> b --> a
+        , funBind "const" $ matchRhs [wildP, x] x
+        ]
+  where
+    a = var "a"
+    b = var "b"
+    x = var "x"
+
+main = runGhc (Just libdir) $ putPpr constModule
+```
+
+Which will output:
+
+```
+module Const (
+        const
+    ) where
+const :: a -> b -> a
+const _ x = x
+```
+
+## Syntax Types
+
+GHC represents Haskell syntax trees with several parametrized datatypes; for example: `HsExpr p` for expressions, `HsDecl p` for declarations, etc.  The parameter `p` determines which stage of compilation that data has last completed: parsing, renaming, or type-checking.
+
+`ghc-source-gen` constructs values as GHC would represent them
+immediately after the parsing step.  In ghc-8.6, that
+corresponds to `p` being `GhcPs`.  It defines several type
+synonyms, such as:
+
+```haskell
+type HsExpr' = HsExpr GhcPs
+type HsType' = HsType GhcPs
+type HsDecl' = HsDecl GhcPs
+type HsModule' = HsModule GhcPs
+-- etc.
+```
+
+GHC's datatypes generally contain location information in the
+form of [`SrcSpan`](http://hackage.haskell.org/package/ghc/docs/SrcLoc.html#t:SrcSpan) values which point to their original
+location in a source file.  `ghc-source-gen` constructs values
+at runtime, so it uses a dummy value for `SrcSpan` on using a
+dummy SrcSpan.  (GHC does something similar for code written at the interactive GHCi prompt.)
+
+`ghc-source-gen` aims to be a low-level wrapper around GHC's
+types.  In particular, it does not explicitly help the user
+generate unique names like, for example, `template-haskell`'s
+[`newName`](http://hackage.haskell.org/package/template-haskell/docs/Language-Haskell-TH.html#v:newName)
+action.  However, we may add support for that in future
+versions of this library.

Setup.hs

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+-- Copyright 2019 Google LLC
+--
+-- Use of this source code is governed by a BSD-style
+-- license that can be found in the LICENSE file or at
+-- https://developers.google.com/open-source/licenses/bsd
+
+import Distribution.Simple
+main = defaultMain

check.sh

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+#!/bin/bash
+# Copyright 2019 Google LLC
+#
+# Use of this source code is governed by a BSD-style
+# license that can be found in the LICENSE file or at
+# https://developers.google.com/open-source/licenses/bsd
+
+# This script tests that ghc-source-gen works on multiple GHC versions.
+# TODO: turn this into a CI script.
+
+set -ueo pipefail
+
+for flag in --resolver={lts-11.22,lts-12.8,lts-13.23} --stack-yaml=stack-8.8.yaml
+do
+    echo ====== $flag ======
+    stack test $flag ghc-source-gen
+done

ghc-show-ast/Main.hs

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+-- Copyright 2019 Google LLC
+--
+-- Use of this source code is governed by a BSD-style
+-- license that can be found in the LICENSE file or at
+-- https://developers.google.com/open-source/licenses/bsd
+
+{-# LANGUAGE GADTs #-}
+module Main where
+
+import Data.Data
+import Data.Typeable (cast)
+import Language.Haskell.GHC.ExactPrint.Parsers
+import System.Environment (getArgs)
+import Text.PrettyPrint
+
+import FastString
+import Name
+    ( Name
+    , isExternalName
+    , isInternalName
+    , isSystemName
+    , isWiredInName
+    , nameOccName
+    , nameUnique
+    )
+import OccName
+    ( OccName
+    , occNameSpace
+    , occNameString
+    , NameSpace
+    , varName
+    , dataName
+    , tvName
+    , tcClsName
+    )
+
+main :: IO ()
+main = do
+    [f] <- getArgs
+    result <- parseModule f
+    case result of
+        Left err -> print err
+        Right (_, ps) -> do
+            print $ gPrint ps
+
+gPrint :: Data a => a -> Doc
+gPrint x
+    | showConstr c == "L", [_,e] <- xs = e
+    | showConstr c == "(:)" = gPrintList x
+    | Just occ <- cast x = text $ showOccName occ
+    | Just name <- cast x = text $ showName name
+    | Just s <- cast x = text $ showFastString s
+    | otherwise =
+        hang (text $ showConstr c) 2 (sep $ map parens xs)
+  where
+    c = toConstr x
+    xs = gmapQ gPrint x
+
+gPrintList :: Data a => a -> Doc
+gPrintList = brackets . sep . punctuate comma . elems
+  where
+    elems :: Data b => b -> [Doc]
+    elems xs = case gmapQ SomeData xs of
+                [] -> []
+                [x,y] -> renderCons x y
+                _ -> error $ "gPrintList: unexpected number of fields"
+    renderCons :: SomeData -> SomeData -> [Doc]
+    renderCons (SomeData x) (SomeData y) = gPrint x : elems y
+
+data SomeData where
+    SomeData :: Data a => a -> SomeData
+
+showOccName :: OccName -> String
+showOccName o = "OccName{" ++ showNameSpace (occNameSpace o)
+                ++ "," ++ show (occNameString o) ++ "}"
+
+showFastString :: FastString -> String
+showFastString = show . unpackFS
+
+showNameSpace :: NameSpace -> String
+showNameSpace ns
+    | ns == varName = "VarName"
+    | ns == dataName = "DataName"
+    | ns == tvName = "TvName"
+    | ns == tcClsName = "TcClsName"
+    | otherwise = "Unknown"
+
+showName :: Name -> String
+showName n = "Name{" ++ nameSort ++ ":" ++ showOccName (nameOccName n)
+                ++ "," ++ show (nameUnique n)
+                ++ "}"
+  where
+    nameSort
+        | isExternalName n = "external"
+        | isInternalName n = "internal"
+        | isSystemName n = "system"
+        | isWiredInName n = "wired-in"
+        | otherwise = "unknown" -- Shouldn't happen; these guards are exhaustive

ghc-show-ast/README.md

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+ghc-show-ast helps debug the behavior of GHC that ghc-source-gen is trying to imitate.
+This program parses a source file with GHC and then pretty-prints the AST.
+
+To use:
+
+    stack run ghc-show-ast -- path/to/file.hs

ghc-show-ast/package.yaml

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+# Copyright 2019 Google LLC
+#
+# Use of this source code is governed by a BSD-style
+# license that can be found in the LICENSE file or at
+# https://developers.google.com/open-source/licenses/bsd
+
+name: ghc-show-ast
+
+executables:
+  ghc-show-ast:
+    main: Main.hs
+    dependencies:
+    - base
+    - ghc
+    - ghc-exactprint
+    - pretty

package.yaml

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+# Copyright 2019 Google LLC
+#
+# Use of this source code is governed by a BSD-style
+# license that can be found in the LICENSE file or at
+# https://developers.google.com/open-source/licenses/bsd
+
+name:                ghc-source-gen
+version:             0.1.0.0
+github:              "google/ghc-source-gen"
+license:             BSD3
+author:              "Judah Jacobson"
+maintainer:          "[email protected]"
+copyright:           "Google LLC"
+
+extra-source-files:
+- README.md
+- ChangeLog.md
+
+synopsis:            Constructs Haskell syntax trees for the GHC API.
+category:            Development
+description:         Please see the README on GitHub at <https://github.com/google/ghc-source-gen>
+
+dependencies:
+- base >= 4.7 && < 5
+- ghc >= 8.2 && < 8.9
+
+default-extensions:
+- DataKinds
+- FlexibleInstances
+- TypeSynonymInstances
+
+library:
+  source-dirs: src
+  other-modules:
+  - GHC.SourceGen.Binds.Internal
+  - GHC.SourceGen.Expr.Internal
+  - GHC.SourceGen.Lit.Internal
+  - GHC.SourceGen.Name.Internal
+  - GHC.SourceGen.Syntax.Internal
+  - GHC.SourceGen.Type.Internal
+
+tests:
+  pprint_examples:
+    main: pprint_examples.hs
+    source-dirs: tests
+    dependencies:
+    - ghc-source-gen
+    - ghc-paths == 0.1.*
+
+  # TODO: Fill out this test, and use it to replace pprint_examples.
+  pprint_test:
+    main: pprint_test.hs
+    source-dirs: tests
+    dependencies:
+    - ghc-source-gen
+    - ghc-paths == 0.1.*
+    - tasty
+    - tasty-hunit

src/GHC/SourceGen.hs

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+-- Copyright 2019 Google LLC
+--
+-- Use of this source code is governed by a BSD-style
+-- license that can be found in the LICENSE file or at
+-- https://developers.google.com/open-source/licenses/bsd
+
+-- | This module exports all of the definitions in this package in one
+-- convenient location.
+--
+-- For more details and examples of usage, see
+-- <https://github.com/google/ghc-source-gen>.
+module GHC.SourceGen
+    ( -- * Syntax types
+      -- | These modules declare combinators for constructing different parts
+      -- of a GHC syntax tree.
+      module GHC.SourceGen.Syntax,
+      module GHC.SourceGen.Name,
+      module GHC.SourceGen.Decl,
+      module GHC.SourceGen.Expr,
+      module GHC.SourceGen.Module,
+      module GHC.SourceGen.Pat,
+      module GHC.SourceGen.Type,
+      -- * Overloaded combinators
+      -- | Certain concepts make sense in different
+      -- parts of Haskell syntax.  For example, 'var' may be used in
+      -- expressions, types, patterns, and import or export lists.
+      module GHC.SourceGen.Binds,
+      module GHC.SourceGen.Lit,
+      module GHC.SourceGen.Overloaded,
+      -- * Renders Haskell syntax into text
+      module GHC.SourceGen.Pretty,
+    ) where
+
+import GHC.SourceGen.Binds
+import GHC.SourceGen.Decl
+import GHC.SourceGen.Expr
+import GHC.SourceGen.Lit
+import GHC.SourceGen.Module
+import GHC.SourceGen.Name
+import GHC.SourceGen.Overloaded
+import GHC.SourceGen.Pat
+import GHC.SourceGen.Pretty
+import GHC.SourceGen.Syntax
+import GHC.SourceGen.Type
+