[lldb][ClangASTImporter] Don't ASTImport LambdaExpr nodes (#154962) #11478
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This patch works around an assertion that we hit in the `LambdaExpr` constructor when we call it from `ASTNodeImporter::VisitLambdaExpr` (see llvm#149477). The lambda that we imported doesn't have the `NumCaptures` field accurately set to the one on the source decl. This is because in `MinimalImport` mode, we skip importing of lambda definitions: https://github.com/llvm/llvm-project/blob/e21b0dd81928a3266df0e3ede008fb7a6676ff95/clang/lib/AST/ASTImporter.cpp#L2499 In practice we have seen this assertion occur in our `import-std-module` test-suite when libc++ headers decide to use lambdas inside inline function bodies (the latest failure being caused by llvm#144602). To avoid running into this whenever libc++ decides to use lambdas in headers, this patch skips `ASTImport` of lambdas alltogether. Ideally this would bubble up to the user or log as an error, but we swallow the `ASTImportError`s currently. The only way this codepath is hit is when lambdas are used inside functions in defined in the expression evaluator, or when importing AST nodes from Clang modules. Both of these are very niche use-cases (for now), so a workaround seemed appropriate. (cherry picked from commit 0bbb794)
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adrian-prantl
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Sep 23, 2025
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This patch works around an assertion that we hit in the
LambdaExprconstructor when we call it fromASTNodeImporter::VisitLambdaExpr(see llvm#149477). The lambda that we imported doesn't have theNumCapturesfield accurately set to the one on the source decl. This is because inMinimalImportmode, we skip importing of lambda definitions:https://github.com/llvm/llvm-project/blob/e21b0dd81928a3266df0e3ede008fb7a6676ff95/clang/lib/AST/ASTImporter.cpp#L2499
In practice we have seen this assertion occur in our
import-std-moduletest-suite when libc++ headers decide to use lambdas inside inline function bodies (the latest failure being caused by llvm#144602).To avoid running into this whenever libc++ decides to use lambdas in headers, this patch skips
ASTImportof lambdas alltogether. Ideally this would bubble up to the user or log as an error, but we swallow theASTImportErrors currently. The only way this codepath is hit is when lambdas are used inside functions in defined in the expression evaluator, or when importing AST nodes from Clang modules. Both of these are very niche use-cases (for now), so a workaround seemed appropriate.(cherry picked from commit 0bbb794)
rdar://160792616