Improve handling of import statements in GHCi (#20473)

Currently in GHCi, when given a line of user input we:

1. Attempt to parse and handle it as a statement
2. Otherwise, attempt to parse and handle a single import
3. Otherwise, check if there are imports present (and if so display an error message)
4. Otherwise, attempt to parse a module and only handle the declarations

This patch simplifies the process to:

Attempt to parse and handle it as a statement
Otherwise, attempt to parse a module and handle the imports and declarations

This means that multiple imports in a multiline are now accepted, and a multiline containing both imports and declarations is now accepted (as well as when separated by semicolons).

1 files changed, 10 insertions, 4 deletions

diff --git a/compiler/GHC/Driver/Main.hs b/compiler/GHC/Driver/Main.hs
index 26647df369..ffc0cef89d 100644
--- a/compiler/GHC/Driver/Main.hs
+++ b/compiler/GHC/Driver/Main.hs
@@ -74,6 +74,7 @@ module GHC.Driver.Main
     , hscTcRnLookupRdrName
     , hscStmt, hscParseStmtWithLocation, hscStmtWithLocation, hscParsedStmt
     , hscDecls, hscParseDeclsWithLocation, hscDeclsWithLocation, hscParsedDecls
+    , hscParseModuleWithLocation
     , hscTcExpr, TcRnExprMode(..), hscImport, hscKcType
     , hscParseExpr
     , hscParseType
@@ -1937,12 +1938,17 @@ hscDecls :: HscEnv
          -> IO ([TyThing], InteractiveContext)
 hscDecls hsc_env str = hscDeclsWithLocation hsc_env str "<interactive>" 1
 
-hscParseDeclsWithLocation :: HscEnv -> String -> Int -> String -> IO [LHsDecl GhcPs]
-hscParseDeclsWithLocation hsc_env source line_num str = do
-    L _ (HsModule{ hsmodDecls = decls }) <-
+hscParseModuleWithLocation :: HscEnv -> String -> Int -> String -> IO HsModule
+hscParseModuleWithLocation hsc_env source line_num str = do
+    L _ mod <-
       runInteractiveHsc hsc_env $
         hscParseThingWithLocation source line_num parseModule str
-    return decls
+    return mod
+
+hscParseDeclsWithLocation :: HscEnv -> String -> Int -> String -> IO [LHsDecl GhcPs]
+hscParseDeclsWithLocation hsc_env source line_num str = do
+  HsModule { hsmodDecls = decls } <- hscParseModuleWithLocation hsc_env source line_num str
+  return decls
 
 -- | Compile a decls
 hscDeclsWithLocation :: HscEnv