Add parseExpr and compileParsedExpr and use them in GHC API and GHCi

Summary:
This commit brings following changes and fixes:

 * Implement parseExpr and compileParsedExpr;
 * Fix compileExpr and dynCompilerExpr, which returned `()` for empty expr;
 * Fix :def and :cmd, which didn't work if `IO` or `String` is not in scope;
 * Use GHCiMonad instead IO in :def and :cmd;
 * Clean PrelInfo: delete dead comment and duplicate entries, add assertion.

See new tests for more details.

Test Plan: ./validate

Reviewers: austin, dterei, simonmar

Reviewed By: simonmar

Subscribers: thomie, bgamari

Differential Revision: https://phabricator.haskell.org/D974

GHC Trac Issues: #10508

8 files changed, 81 insertions, 1 deletions

diff --git a/testsuite/tests/ghc-api/T10508_api.hs b/testsuite/tests/ghc-api/T10508_api.hs
new file mode 100644
index 0000000000..afe8e50e73
--- /dev/null
+++ b/testsuite/tests/ghc-api/T10508_api.hs
@@ -0,0 +1,32 @@
+module Main where
+
+import DynFlags
+import GHC
+
+import Control.Monad (forM_)
+import Control.Monad.IO.Class (liftIO)
+import System.Environment (getArgs)
+
+main :: IO ()
+main = do
+  [libdir] <- getArgs
+  runGhc (Just libdir) $ do
+    dflags <- getSessionDynFlags
+    setSessionDynFlags $ dflags
+      `gopt_unset` Opt_ImplicitImportQualified
+      `xopt_unset` Opt_ImplicitPrelude
+
+    forM_ exprs $ \expr ->
+      handleSourceError printException $ do
+        dyn <- dynCompileExpr expr
+        liftIO $ print dyn
+  where
+  exprs =
+    [ ""
+    , "(),()"
+    , "()"
+    , "\"test\""
+    , unlines [ "[()]"
+              , " :: [()]"
+              ]
+    ]
diff --git a/testsuite/tests/ghc-api/T10508_api.stderr b/testsuite/tests/ghc-api/T10508_api.stderr
new file mode 100644
index 0000000000..29533435f3
--- /dev/null
+++ b/testsuite/tests/ghc-api/T10508_api.stderr
@@ -0,0 +1,4 @@
+
+<no location info>: error: not an expression: ‘’
+
+<interactive>:1:3: error: parse error on input ‘,’
diff --git a/testsuite/tests/ghc-api/T10508_api.stdout b/testsuite/tests/ghc-api/T10508_api.stdout
new file mode 100644
index 0000000000..9a6eb4c38f
--- /dev/null
+++ b/testsuite/tests/ghc-api/T10508_api.stdout
@@ -0,0 +1,3 @@
+<<()>>
+<<[Char]>>
+<<[()]>>
diff --git a/testsuite/tests/ghc-api/all.T b/testsuite/tests/ghc-api/all.T
index 11e8c422b6..c4783ea15d 100644
--- a/testsuite/tests/ghc-api/all.T
+++ b/testsuite/tests/ghc-api/all.T
@@ -8,4 +8,9 @@ test('T8639_api', normal,
 test('T8628', normal,
               run_command,
               ['$MAKE -s --no-print-directory T8628'])
-test('T9595', extra_run_opts('"' + config.libdir + '"'), compile_and_run, ['-package ghc'])
+test('T9595', extra_run_opts('"' + config.libdir + '"'),
+              compile_and_run,
+              ['-package ghc'])
+test('T10508_api', extra_run_opts('"' + config.libdir + '"'),
+                   compile_and_run,
+                   ['-package ghc'])
diff --git a/testsuite/tests/ghci/scripts/T10508.script b/testsuite/tests/ghci/scripts/T10508.script
new file mode 100644
index 0000000000..5ac770060b
--- /dev/null
+++ b/testsuite/tests/ghci/scripts/T10508.script
@@ -0,0 +1,21 @@
+-- :cmd accepts an expr of type 'IO String'
+let cmd = return "0"
+:cmd cmd
+
+-- works with multiline mode, handles indention correctly
+:{
+:cmd return $ unlines
+  [ "1"
+  , "2"
+  ]
+:}
+
+-- it should work even 'IO' or 'String' is not in scope
+import Prelude ()
+:cmd cmd
+
+-- or even when a different 'String' is in scope
+import Prelude
+type String = ShowS
+:def macro \_ -> return id
+:macro
diff --git a/testsuite/tests/ghci/scripts/T10508.stderr b/testsuite/tests/ghci/scripts/T10508.stderr
new file mode 100644
index 0000000000..c5aff2361c
--- /dev/null
+++ b/testsuite/tests/ghci/scripts/T10508.stderr
@@ -0,0 +1,8 @@
+
+<interactive>:1:15:
+    Couldn't match type ‘a0 -> a0’ with ‘[Char]’
+    Expected type: Prelude.String
+      Actual type: a0 -> a0
+    Probable cause: ‘id’ is applied to too few arguments
+    In the first argument of ‘return’, namely ‘id’
+    In the expression: return id
\ No newline at end of file
diff --git a/testsuite/tests/ghci/scripts/T10508.stdout b/testsuite/tests/ghci/scripts/T10508.stdout
new file mode 100644
index 0000000000..c6c8d3a447
--- /dev/null
+++ b/testsuite/tests/ghci/scripts/T10508.stdout
@@ -0,0 +1,6 @@
+0
+1
+2
+0
+unknown command ':macro'
+use :? for help.
diff --git a/testsuite/tests/ghci/scripts/all.T b/testsuite/tests/ghci/scripts/all.T
index df02add5b4..c2c75ecb94 100755
--- a/testsuite/tests/ghci/scripts/all.T
+++ b/testsuite/tests/ghci/scripts/all.T
@@ -221,3 +221,4 @@ test('T10110', normal, ghci_script, ['T10110.script'])
 test('T10322', normal, ghci_script, ['T10322.script'])
 test('T10466', normal, ghci_script, ['T10466.script'])
 test('T10501', normal, ghci_script, ['T10501.script'])
+test('T10508', normal, ghci_script, ['T10508.script'])