sv_elaborate crashes with SIGSEGV

Describe the bug

When elaborating SystemVerilog designs using sv_elaborate (the Slang frontend), OpenROAD crashes with a SIGSEGV (or UndefinedBehaviorSanitizer: invalid-bool-load under ASan/UBSan) if the design contains a conditional generate block (if-generate or case-generate) with internal nets or variables.

Expected Behavior

No error.

Environment

Git Commit: 34075db75016d6f080abe02a9cc4760c2af50768 (Latest upstream master)
OS / Kernel: Debian GNU/Linux rodete (6.18.14-1rodete3-amd64)
CMake: 3.31.9
Python: 3.10.6
SWIG: 4.3.0
Slang Version: 10.0.150+f04e81565
Yosys-Slang Revision: 82effc8d9541be69e1ed3ec44759a4449f5d9247

Note I didn't use cmake while reproducing this.

To Reproduce

bazelisk build --copt=-fsanitize=undefined --linkopt=-fno-sanitize-link-runtime //:openroad && ASAN_OPTIONS=detect_leaks=0:halt_on_error=1 ./bazel-bin/openroad -no_splash <<< "sv_elaborate --top top <(echo 'module top; if (1) begin : g wire w; end endmodule'); exit"

You may need to point to a specific asan library like --linkopt=/usr/lib/x86_64-linux-gnu/libubsan.so.1 and/or LD_PRELOAD=/usr/lib/x86_64-linux-gnu/libasan.so.8, but hopefully not.

This sigsegvs and gives the following backtrace (obtained seperately):

#0  slang_frontend::build_hierpath2(NetlistContext&, ostringstream&, Scope const*, string const&)
    at third-party/slang-elab/src/slang_frontend.cc:2520
#1  slang_frontend::build_hiername(NetlistContext&, Symbol const&, string const&)
    at third-party/slang-elab/src/slang_frontend.cc:2632
#2  slang_frontend::PopulateNetlist::add_internal_wires(InstanceBodySymbol const&)
    at third-party/slang-elab/src/slang_frontend.cc:2158
#3  slang::ast::ASTVisitor::visitDefault<slang::ast::GenerateBlockSymbol>(GenerateBlockSymbol const&)
#4  slang::ast::ASTVisitor::visitDefault<slang::ast::InstanceBodySymbol>(InstanceBodySymbol const&)
#5  slang_frontend::populate_netlist(HierarchyQueue&, NetlistContext&)
    at third-party/slang-elab/src/slang_frontend.cc:2208
#6  syn::elaborateImpl(...) at src/syn/src/elab/driver.cc:151
#7  syn::Synthesis::svElaborate(...) at src/syn/src/synthesis.cpp:44

Relevant log output

Screenshots

No response

Additional Context

In Slang GenerateBlockSymbol stores its loop iteration index and conditional branch expression in an anonymous union:

struct GenerateBlockSymbol : public Scope, public Symbol {
    union {
        const SVInt* arrayIndex = nullptr;
        const Expression* conditionExpression;
    };
    /// Returns the loop-iteration index, or nullptr if this block is not a loop iteration.
    const SVInt* getArrayIndex() const {
        return branchKind == GenerateBranchKind::LoopIteration ? arrayIndex : nullptr;
    }
};

In OpenROAD's slang-elab frontend the code directly accesses block.arrayIndex instead of using the safe accessor block.getArrayIndex(). https://github.com/povik/sv-elab/blob/82effc8d9541be69e1ed3ec44759a4449f5d9247/src/slang_frontend.cc#L2519