[modules] Introduce new VariableLocation for module imports/exports.

src/compiler/ast-graph-builder.cc

Index: src/compiler/ast-graph-builder.cc
diff --git a/src/compiler/ast-graph-builder.cc b/src/compiler/ast-graph-builder.cc
index 3668ff8c01cdfe07d121b8eaa201ad2623b2fd57..fcb3a061838a9d27a68d71bc4aa44128f5c8264e 100644
--- a/src/compiler/ast-graph-builder.cc
+++ b/src/compiler/ast-graph-builder.cc
@@ -1185,6 +1185,8 @@ void AstGraphBuilder::VisitVariableDeclaration(VariableDeclaration* decl) {
       PrepareFrameState(store, decl->proxy()->id());
       break;
     }
+    case VariableLocation::MODULE:
+      UNREACHABLE();
   }
 }
 
@@ -1228,6 +1230,8 @@ void AstGraphBuilder::VisitFunctionDeclaration(FunctionDeclaration* decl) {
       PrepareFrameState(store, decl->proxy()->id());
       break;
     }
+    case VariableLocation::MODULE:
+      UNREACHABLE();
   }
 }
 
@@ -3445,6 +3449,8 @@ Node* AstGraphBuilder::BuildVariableLoad(Variable* variable,
       PrepareFrameState(value, bailout_id, combine);
       return value;
     }
+    case VariableLocation::MODULE:
+      UNREACHABLE();
   }
   UNREACHABLE();
   return nullptr;
@@ -3480,6 +3486,8 @@ Node* AstGraphBuilder::BuildVariableDelete(Variable* variable,
       PrepareFrameState(result, bailout_id, combine);
       return result;
     }
+    case VariableLocation::MODULE:
+      UNREACHABLE();
   }
   UNREACHABLE();
   return nullptr;
@@ -3590,6 +3598,8 @@ Node* AstGraphBuilder::BuildVariableAssignment(
       PrepareFrameState(store, bailout_id, combine);
       return store;
     }
+    case VariableLocation::MODULE:
+      UNREACHABLE();
   }
   UNREACHABLE();
   return nullptr;