fix: Don't pass 'If' to InvalidObj when Obj actually is 'Mod' (#1327)

* fix: Don't pass 'If' to InvalidObj when Obj actually is 'Mod'

* fix: Better error message

* fix: Better error

* fix: Show the name of the module in the error message

* fix: Use `root` to get correct location for InvalidObj error

* fix: keep old xobj for now

Author: eriksvedang

src/InitialTypes.hs

@@ -98,7 +98,7 @@ initialTypes typeEnv rootEnv root = evalState (visit rootEnv root) 0
       If -> pure (Left (InvalidObj If xobj))
       While -> pure (Left (InvalidObj While xobj))
       Do -> pure (Left (InvalidObj Do xobj))
-      (Mod _ _) -> pure (Left (InvalidObj If xobj))
+      m@(Mod _ _) -> pure (Left (InvalidObj m xobj))
       e@(Deftype _) -> pure (Left (InvalidObj e xobj))
       e@(External _) -> pure (Left (InvalidObj e xobj))
       e@(ExternalType _) -> pure (Left (InvalidObj e xobj))

src/TypeError.hs

@@ -103,6 +103,13 @@ instance Show TypeError where
   show (InvalidObj If xobj) =
     "I didn’t understand the `if` statement at " ++ prettyInfoFromXObj xobj
       ++ ".\n\nIs it valid? Every `if` needs to follow the form `(if cond iftrue iffalse)`."
+  show (InvalidObj (Mod env _) xobj) =
+    let moduleName =
+          case envModuleName env of
+            Just name -> "the module '" ++ name ++ "'"
+            Nothing -> "an unnamed module"
+     in "I didn’t understand the form mentioning " ++ moduleName ++ " at " ++ prettyInfoFromXObj xobj
+          ++ ".\n\nAre you using a module or type where a value is expected?"
   show (InvalidObj o xobj) =
     "I didn’t understand the form `" ++ prettyObj o ++ "` at "
       ++ prettyInfoFromXObj xobj