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cbfa5c84f9
Here's an example crash that we've seen sporadically over the years:
```
0 libsystem_kernel.dylib 0x19d392388 __pthread_kill + 8
1 libsystem_pthread.dylib 0x19d3cb88c pthread_kill + 296
2 libsystem_c.dylib 0x19d29cd04 raise + 32
3 LLDB 0x112cbbc94 SignalHandler(int, __siginfo*, void*) + 324
4 libsystem_platform.dylib 0x19d4056a4 _sigtramp + 56
5 LLDB 0x110dcbd38 clang::TextDiagnosticPrinter::HandleDiagnostic(clang::DiagnosticsEngine::Level, clang::Diagnostic const&) + 1216
6 LLDB 0x110dcbd38 clang::TextDiagnosticPrinter::HandleDiagnostic(clang::DiagnosticsEngine::Level, clang::Diagnostic const&) + 1216
7 LLDB 0x10de12128 ClangDiagnosticManagerAdapter::HandleDiagnostic(clang::DiagnosticsEngine::Level, clang::Diagnostic const&) + 332
8 LLDB 0x1121eb3dc clang::DiagnosticIDs::ProcessDiag(clang::DiagnosticsEngine&) const + 200
9 LLDB 0x1121e67a0 clang::DiagnosticsEngine::EmitCurrentDiagnostic(bool) + 100
10 LLDB 0x111d766cc IsStructurallyEquivalent(clang::StructuralEquivalenceContext&, clang::FieldDecl*, clang::FieldDecl*, clang::QualType) + 1568
11 LLDB 0x111d71b54 IsStructurallyEquivalent(clang::StructuralEquivalenceContext&, clang::RecordDecl*, clang::RecordDecl*) + 2076
12 LLDB 0x111d6e448 clang::StructuralEquivalenceContext::Finish() + 204
13 LLDB 0x111d6e1e0 clang::StructuralEquivalenceContext::IsEquivalent(clang::Decl*, clang::Decl*) + 32
14 LLDB 0x111d3b788 clang::ASTNodeImporter::IsStructuralMatch(clang::Decl*, clang::Decl*, bool, bool) + 168
15 LLDB 0x111d404e0 clang::ASTNodeImporter::VisitFunctionDecl(clang::FunctionDecl*) + 1300
16 LLDB 0x111d5cae0 clang::ASTImporter::ImportImpl(clang::Decl*) + 24
17 LLDB 0x10ddf30bc lldb_private::ClangASTImporter::ASTImporterDelegate::ImportImpl(clang::Decl*) + 308
18 LLDB 0x111d48140 clang::ASTImporter::Import(clang::Decl*) + 984
19 LLDB 0x10ddee9dc lldb_private::ClangASTImporter::CopyDecl(clang::ASTContext*, clang::Decl*) + 100
20 LLDB 0x10ddfab40 lldb_private::ClangASTSource::FindExternalLexicalDecls(clang::DeclContext const*, llvm::function_ref<bool (clang::Decl::Kind)>, llvm::SmallVectorImpl<clang::Decl*>&) + 1692
21 LLDB 0x111e1cb84 clang::DeclContext::LoadLexicalDeclsFromExternalStorage() const + 180
22 LLDB 0x111e1df50 clang::DeclContext::buildLookup() + 204
23 LLDB 0x111e1dcf4 clang::DeclContext::makeDeclVisibleInContextWithFlags(clang::NamedDecl*, bool, bool) + 504
24 LLDB 0x111d3b01c clang::ASTNodeImporter::ImportDeclContext(clang::DeclContext*, bool) + 724
25 LLDB 0x111d62d10 clang::ASTImporter::ImportDefinition(clang::Decl*) + 428
26 LLDB 0x10ddf1cb0 lldb_private::ClangASTImporter::ASTImporterDelegate::ImportDefinitionTo(clang::Decl*, clang::Decl*) + 524
27 LLDB 0x10ddef3c8 (anonymous namespace)::CompleteTagDeclsScope::~CompleteTagDeclsScope() + 616
28 LLDB 0x10ddef6dc lldb_private::ClangASTImporter::DeportDecl(clang::ASTContext*, clang::Decl*) + 436
29 LLDB 0x10ddec3dc lldb_private::ASTResultSynthesizer::CommitPersistentDecls() + 236
30 LLDB 0x10de1091c lldb_private::ClangExpressionParser::ParseInternal(lldb_private::DiagnosticManager&, clang::CodeCompleteConsumer*, unsigned int, unsigned int) + 2292
31 LLDB 0x10de21238 lldb_private::ClangUserExpression::TryParse(lldb_private::DiagnosticManager&, lldb_private::ExecutionContext&, lldb_private::ExecutionPolicy, bool, bool) + 328
...
```
Here `ASTImporter::IsStructurallyEquivalent` is trying to emit a
diagnostic using `ClangExpressionParser`'s
`ClangDiagnosticManagerAdapter`. But `TextDiagnosticPrinter::TextDiag`
seems to be `nullptr`. This can only happen when we call
`HandleDiagnostic` on `ClangDiagnosticManagerAdapter` after we called
`EndSourceFile`. Specifically, it looks like when moving a type from
`Expression` AST to `Scratch` AST (in `CommitPersistentDecls`),
something went wrong, so the ASTImporter tried to emit a diagnostic, but
we already called `EndSourceFile` at that point.
This patch moves the call to `ResetManager` to before
`CommitPersistentDecls`, so if we called `HandleDiagnostic`, we would
correctly short-circuit out of it. This seems to have been intended
anyway based on this comment:
cecdff9283/lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionParser.cpp (L200-L204)
But something must have broken that during a refactor.
I'm not 100% sure how best to test this because we need a scenario where
moving a type into the scratch AST fails, but the expression itself
succeeded.
rdar://159647906