src/jdk.scripting.nashorn/share/classes/jdk/nashorn/internal/runtime/SetMethodCreator.java

*** 143,154 ****
      private SetMethod createExistingPropertySetter() {
          final Property property = find.getProperty();
          final boolean isStrict  = NashornCallSiteDescriptor.isStrict(desc);
          final MethodHandle methodHandle;
  
!         if (NashornCallSiteDescriptor.isDeclaration(desc)) {
!             assert property.needsDeclaration();
              // This is a LET or CONST being declared. The property is already there but flagged as needing declaration.
              // We create a new PropertyMap with the flag removed. The map is installed with a fast compare-and-set
              // method if the pre-callsite map is stable (which should be the case for function scopes except for
              // non-strict functions containing eval() with var). Otherwise we have to use a slow setter that creates
              // a new PropertyMap on the fly.
--- 143,153 ----
      private SetMethod createExistingPropertySetter() {
          final Property property = find.getProperty();
          final boolean isStrict  = NashornCallSiteDescriptor.isStrict(desc);
          final MethodHandle methodHandle;
  
!         if (NashornCallSiteDescriptor.isDeclaration(desc) && property.needsDeclaration()) {
              // This is a LET or CONST being declared. The property is already there but flagged as needing declaration.
              // We create a new PropertyMap with the flag removed. The map is installed with a fast compare-and-set
              // method if the pre-callsite map is stable (which should be the case for function scopes except for
              // non-strict functions containing eval() with var). Otherwise we have to use a slow setter that creates
              // a new PropertyMap on the fly.