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

4 files changed, 45 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'])