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

src/interpreter/bytecode-generator.cc

Index: src/interpreter/bytecode-generator.cc
diff --git a/src/interpreter/bytecode-generator.cc b/src/interpreter/bytecode-generator.cc
index 58f6e7288dc9c71e5c37863e4c643c0dbbfafaa0..04dd44a4b15a65b6d68ceca3fdbc3d4911d6427a 100644
--- a/src/interpreter/bytecode-generator.cc
+++ b/src/interpreter/bytecode-generator.cc
@@ -833,6 +833,8 @@ void BytecodeGenerator::VisitVariableDeclaration(VariableDeclaration* decl) {
           .CallRuntime(Runtime::kDeclareEvalVar, name, 1);
       break;
     }
+    case VariableLocation::MODULE:
+      UNREACHABLE();
   }
 }
 
@@ -874,7 +876,10 @@ void BytecodeGenerator::VisitFunctionDeclaration(FunctionDeclaration* decl) {
       VisitForAccumulatorValue(decl->fun());
       builder()->StoreAccumulatorInRegister(literal).CallRuntime(
           Runtime::kDeclareEvalFunction, name, 2);
+      break;
     }
+    case VariableLocation::MODULE:
+      UNREACHABLE();
   }
 }
 
@@ -1876,6 +1881,8 @@ void BytecodeGenerator::VisitVariableLoad(Variable* variable,
       execution_result()->SetResultInAccumulator();
       break;
     }
+    case VariableLocation::MODULE:
+      UNREACHABLE();
   }
 }
 
@@ -2101,6 +2108,8 @@ void BytecodeGenerator::VisitVariableAssignment(Variable* variable,
       builder()->StoreLookupSlot(variable->name(), language_mode());
       break;
     }
+    case VariableLocation::MODULE:
+      UNREACHABLE();
   }
 }