src/jdk.scripting.nashorn/share/classes/jdk/nashorn/internal/parser/Parser.java

*** 1102,1117 ****
                  try {
                      init = assignmentExpression(!isStatement);
                  } finally {
                      defaultNames.pop();
                  }
!             } else if (varType == CONST) {
                  throw error(AbstractParser.message("missing.const.assignment", name.getName()));
              }
  
              // Allocate var node.
!             final VarNode var = new VarNode(varLine, varToken, sourceOrder, finish, name.setIsDeclaredHere(), init, varFlags);
              vars.add(var);
              appendStatement(var);
  
              if (type != COMMARIGHT) {
                  break;
--- 1102,1119 ----
                  try {
                      init = assignmentExpression(!isStatement);
                  } finally {
                      defaultNames.pop();
                  }
!             } else if (varType == CONST && isStatement) {
                  throw error(AbstractParser.message("missing.const.assignment", name.getName()));
              }
  
+             // Only set declaration flag on lexically scoped let/const as it adds runtime overhead.
+             final IdentNode actualName = varType == LET || varType == CONST ? name.setIsDeclaredHere() : name;
              // Allocate var node.
!             final VarNode var = new VarNode(varLine, varToken, sourceOrder, finish, actualName, init, varFlags);
              vars.add(var);
              appendStatement(var);
  
              if (type != COMMARIGHT) {
                  break;
*** 1245,1255 ****
                  next();
              }
  
              expect(LPAREN);
  
- 
              switch (type) {
              case VAR:
                  // Var declaration captured in for outer block.
                  vars = variableStatement(type, false, forStart);
                  break;
--- 1247,1256 ----