Ignore import decls to delay the running module inits.

If we preload modules using cling::Interpreter::loadModule the
deserializations of the module initializers (such as global variables).

We want the behavior of clang::Sema::ActOnModuleImport, however, it requires
valid source locations.

This patch ignores the ImportDecls which presumably came from loadModule.

lib/Interpreter/DeclCollector.cpp

@@ -56,6 +56,7 @@ namespace {
       if (VD->hasGlobalStorage() && !VD->getType().isConstQualified()
           && VD->getTemplateSpecializationKind() == TSK_Undeclared)
         return true;
+
     return false;
   }
 
@@ -231,6 +232,18 @@ namespace cling {
         continue;
       }
     } else {
+
+      // FIXME: This is a temporary fix for the ROOT module preloading mechanism.
+      // When we preload modules we would like to enable a module as if we called
+      // clang::Sema::ActOnModuleImport (which does not call HandleTopLevelDecl).
+      // However, we need a valid source locations as modules are very sensitive
+      // to them. In order to have a valid source location,
+      // Interpreter::loadModule calls '#pragma clang module import "A"', which
+      // calls HandleTopLevelDecl which causes CodeGen to run the module
+      // initializers eagerly.
+      if (DGR.isSingleDecl() && isa<ImportDecl>(DGR.getSingleDecl()))
+	return true;
+
       m_Consumer->HandleTopLevelDecl(DGR);
     }
     return true;