invalid arithmetic between different enumeration types

While compiling with c++26, I am seeing the error:

glslang/glslang/MachineIndependent/ParseHelper.cpp:10361:108: error: invalid arithmetic between different enumeration types ('TLayoutPacking' and 'TLayoutMatrix')
10361 | size_t originMemberHash = hasher(originType->getStruct()->at(i).type->getQualifier().layoutPacking +
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ^
10362 | originType->getStruct()->at(i).type->getQualifier().layoutMatrix);
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

glslang/glslang/MachineIndependent/ParseHelper.cpp:10363:102: error: invalid arithmetic between different enumeration types ('TLayoutPacking' and 'TLayoutMatrix')
10363 | size_t tmpMemberHash = hasher(tmpType->getStruct()->at(i).type->getQualifier().layoutPacking +
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ^
10364 | tmpType->getStruct()->at(i).type->getQualifier().layoutMatrix);
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Start in glslang/glslang/MachineIndependent/ParseHelper.cpp around lines 10361-10364, where the member hashes add TLayoutPacking and TLayoutMatrix values. Reproduce the diagnostic with a C++26 build, then verify the affected code compiles without the invalid-enumeration-arithmetic errors.

Written by the indexing model from the issue text.