Delay finishing the C++ translation unit until we reach the real EOF. #6489
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This fixes some issues where we would produce duplicated or incorrect diagnostics at the end of the C++ translation unit, particularly for unused declarations. Don't allow a C++ module to be defined in an inline Cpp fragment.
Reuse the same parser for macro parsing.
jonmeow
approved these changes
Dec 11, 2025
toolchain/check/cpp/generate_ast.cpp
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| // Parse the imports and inline C++ fragments. This is notionally very | ||
| // similar to `ParseAST`, but doesn't parse C++20 modules and stops just | ||
| // before reaching the end of the translation unit. |
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Perhaps move this to be a function comment? I'm not sure if it's just understood what ExecuteAction is expected to do.
Co-authored-by: Jon Ross-Perkins <[email protected]>
toolchain/check/context.h
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| "Already have a C++ context"); | ||
| cpp_context_ = std::move(cpp_context); |
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Suggested change
| "Already have a C++ context"); | |
| cpp_context_ = std::move(cpp_context); | |
| CARBON_CHECK(!cpp_context_ || !cpp_context, "Already have a C++ context"); |
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Instead of parsing a complete C++ translation unit and then interacting with the translation unit further after the fact, delay finishing the translation unit until we finish the Carbon check phase. This fixes some issues where we would produce duplicated or incorrect diagnostics at the end of the C++ translation unit, particularly for unused declarations. Now we're in control of how we parse the translation unit, also disable parsing of C++20 modules if the syntax appears within
import Cpp inlinecode.Keep the same clang parser alive throughout check, and use it instead of building a new one when parsing macros. This resolves issues where the translation unit scope was destroyed too early, resulting in unqualified lookup within macros being unable to find global scope entities.