[clang] Reland "[Modules] Record whether VarDecl initializers contain side effects" (PR #145447)

[via cfe-commits]

bgra8 wrote:

@hnrklssn we (at google) have bisected a clang crash at the original commit (https://github.com/llvm/llvm-project/commit/f2e9f882e07e0b6507ece9ca8abbbb556cd5c659) that also reproduces at this revision.

Here's the stack trace:

```
assert.h assertion failed at llvm-project/llvm/include/llvm/Support/Casting.h:566 in decltype(auto) llvm::cast(const From &) [To = clang::RecordType, From = clang::QualType]: isa<To>(Val) && "cast<Ty>() argument of incompatible type!"
*** Check failure stack trace: ***
    @     0x55b57e120f04  absl::log_internal::LogMessage::SendToLog()
    @     0x55b57e120ec7  absl::log_internal::LogMessage::Flush()
    @     0x55b57e349204  __assert_fail
    @     0x55b57a572ad0  CheckEvaluationResult()
    @     0x55b57a5353a5  clang::Expr::EvaluateAsInitializer()
    @     0x55b57a44eb32  clang::VarDecl::evaluateValueImpl()
    @     0x55b57a44e07a  clang::VarDecl::evaluateValue()
    @     0x55b57a44df78  clang::VarDecl::hasInitWithSideEffects()
    @     0x55b579595839  clang::ASTDeclWriter::VisitVarDecl()
    @     0x55b57958e996  clang::ASTDeclWriter::Visit()
    @     0x55b5795a18bc  clang::ASTWriter::WriteDecl()
    @     0x55b579551725  clang::ASTWriter::WriteDeclAndTypes()
    @     0x55b57954b42b  clang::ASTWriter::WriteASTCore()
    @     0x55b57954a131  clang::ASTWriter::WriteAST()
    @     0x55b5795bb1e0  clang::PCHGenerator::HandleTranslationUnit()
    @     0x55b579127cfd  clang::MultiplexConsumer::HandleTranslationUnit()
    @     0x55b57933a948  clang::ParseAST()
    @     0x55b57906e34a  clang::FrontendAction::Execute()
    @     0x55b578fe125d  clang::CompilerInstance::ExecuteAction()
    @     0x55b57842586b  clang::ExecuteCompilerInvocation()
    @     0x55b578419218  cc1_main()
    @     0x55b578416334  ExecuteCC1Tool()
    @     0x55b579197a3e  llvm::function_ref<>::callback_fn<>()
    @     0x55b57df95c9c  llvm::CrashRecoveryContext::RunSafely()
    @     0x55b579196f24  clang::driver::CC1Command::Execute()
    @     0x55b579157615  clang::driver::Compilation::ExecuteCommand()
    @     0x55b5791578af  clang::driver::Compilation::ExecuteJobs()
    @     0x55b579173200  clang::driver::Driver::ExecuteCompilation()
    @     0x55b57841593d  clang_main()
    @     0x55b578413cf4  main
    @     0x7fc1572933d4  __libc_start_main
    @     0x55b578413c2a  _start
```

Can you please take a look?

https://github.com/llvm/llvm-project/pull/145447