feat(frontends/lean/parser): protect imported modules from Lua definitions and macros in the file importing the module

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>

src/frontends/lean/parser.cpp

@@ -2346,7 +2346,8 @@ class parser::imp {
             return;
         }
         try {
-            parser import_parser(m_env, m_io_state, in, m_script_state, true /* use exceptions */, false /* not interactive */);
+            script_state state; // Empty state object for the imported module
+            parser import_parser(m_env, m_io_state, in, &state, true /* use exceptions */, false /* not interactive */);
             import_parser();
         } catch (interrupted &) {
             throw;

tests/lean/macro.lean

@@ -0,0 +1,11 @@
+(**
+macro("IdMacro",
+      { macro_arg.Expr },
+      function (env, e)
+         return e
+      end
+)
+**)
+
+Show IdMacro 10.
+Import "module.lean"

tests/lean/macro.lean.expected.out

@@ -0,0 +1,5 @@
+  Set: pp::colors
+  Set: pp::unicode
+10
+Error (line: 2, pos: 5) unknown identifier 'IdMacro'
+Error (line: 11, pos: 0) failed to import file './module.lean'

tests/lean/module.lean

@@ -0,0 +1,2 @@
+(* The following command should fail because the IdMacro is not defined *)
+Show IdMacro 20.

tests/lean/module.lean.expected.out

@@ -0,0 +1,3 @@
+  Set: pp::colors
+  Set: pp::unicode
+Error (line: 2, pos: 5) unknown identifier 'IdMacro'