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

2 files changed, 24 insertions, 18 deletions

diff --git a/compiler/prelude/PrelInfo.hs b/compiler/prelude/PrelInfo.hs
index 4d1cd9af95..5ab060e941 100644
--- a/compiler/prelude/PrelInfo.hs
+++ b/compiler/prelude/PrelInfo.hs
@@ -36,6 +36,8 @@ import TysWiredIn
 import HscTypes
 import Class
 import TyCon
+import Outputable
+import UniqFM
 import Util
 import {-# SOURCE #-} TcTypeNats ( typeNatTyCons )
 
@@ -53,13 +55,20 @@ import Data.Array
 ********************************************************************* -}
 
 knownKeyNames :: [Name]
-knownKeyNames
-  = map getName wiredInThings
-    ++ cTupleTyConNames
-    ++ basicKnownKeyNames
+knownKeyNames =
+  ASSERT2( isNullUFM badNamesUFM, text "badknownKeyNames" <+> ppr badNamesUFM )
+  names
+  where
+  badNamesUFM = filterUFM (\ns -> length ns > 1) namesUFM
+  namesUFM = foldl (\m n -> addToUFM_Acc (:) singleton m n n) emptyUFM names
+  names = concat
+    [ map getName wiredInThings
+    , cTupleTyConNames
+    , basicKnownKeyNames
 #ifdef GHCI
-    ++ templateHaskellNames
+    , templateHaskellNames
 #endif
+    ]
 
 {- *********************************************************************
 *                                                                      *
diff --git a/compiler/prelude/PrelNames.hs b/compiler/prelude/PrelNames.hs
index ded9583c62..8b60088666 100644
--- a/compiler/prelude/PrelNames.hs
+++ b/compiler/prelude/PrelNames.hs
@@ -170,12 +170,6 @@ isUnboundName name = name `hasKey` unboundKey
 This section tells what the compiler knows about the association of
 names with uniques.  These ones are the *non* wired-in ones.  The
 wired in ones are defined in TysWiredIn etc.
-
-The names for DPH can come from one of multiple backend packages. At the point where
-'basicKnownKeyNames' is used, we don't know which backend it will be.  Hence, we list
-the names for multiple backends.  That works out fine, although they use the same uniques,
-as we are guaranteed to only load one backend; hence, only one of the different names
-sharing a unique will be used.
 -}
 
 basicKnownKeyNames :: [Name]
@@ -188,7 +182,6 @@ basicKnownKeyNames
         stringTyConName,
         ratioDataConName,
         ratioTyConName,
-        integerTyConName,
 
         --  Classes.  *Must* include:
         --      classes that are grabbed by key (e.g., eqClassKey)
@@ -221,6 +214,8 @@ basicKnownKeyNames
         mkAppTyName,
         typeLitTypeRepName,
 
+        -- Dynamic
+        toDynName,
 
         -- Numeric stuff
         negateName, minusName, geName, eqName,
@@ -247,8 +242,8 @@ basicKnownKeyNames
         fmapName,
         joinMName,
 
-        -- MonadRec stuff
-        mfixName,
+        -- MonadFix
+        monadFixClassName, mfixName,
 
         -- Arrow stuff
         arrAName, composeAName, firstAName,
@@ -318,9 +313,6 @@ basicKnownKeyNames
         rationalToFloatName,
         rationalToDoubleName,
 
-        -- MonadFix
-        monadFixClassName, mfixName,
-
         -- Other classes
         randomClassName, randomGenClassName, monadPlusClassName,
 
@@ -1038,7 +1030,9 @@ mkPolyTyConAppName    = varQual tYPEABLE_INTERNAL (fsLit "mkPolyTyConApp") mkPol
 mkAppTyName           = varQual tYPEABLE_INTERNAL (fsLit "mkAppTy")        mkAppTyKey
 typeLitTypeRepName    = varQual tYPEABLE_INTERNAL (fsLit "typeLitTypeRep") typeLitTypeRepKey
 
-
+-- Dynamic
+toDynName :: Name
+toDynName = varQual dYNAMIC (fsLit "toDyn") toDynIdKey
 
 -- Class Data
 dataClassName :: Name
@@ -1887,6 +1881,9 @@ mkPolyTyConAppKey = mkPreludeMiscIdUnique 504
 mkAppTyKey        = mkPreludeMiscIdUnique 505
 typeLitTypeRepKey = mkPreludeMiscIdUnique 506
 
+-- Dynamic
+toDynIdKey :: Unique
+toDynIdKey = mkPreludeMiscIdUnique 507
 
 {-
 ************************************************************************