| Issue |
204632
|
| Summary |
Clang asserts in ASTContext::setCurrentNamedModule after C++ named module conflicts with module map module
|
| Labels |
|
| Assignees |
|
| Reporter |
hongtaihu
|
### Reproducer
`main.cpp`:
```cpp
export module M;
```
`module.modulemap`:
```text
module M {}
```
Run:
```bash
clang++ -x c++ -fsyntax-only -std=c++26 -fmodules \
-fmodule-map-file=module.modulemap \
main.cpp
```
I can also reproduce with `--target=x86_64-pc-win32`, but the target is not required.
### Actual result
Clang diagnoses the module redefinition, then asserts:
```text
main.cpp:1:15: error: redefinition of module 'M'
1 | export module M;
| ^
module.modulemap:1:8: note: previously defined here
1 | module M {}
| ^
clang++: .../clang/lib/AST/ASTContext.cpp:1173:
void clang::ASTContext::setCurrentNamedModule(clang::Module*):
Assertion `M->isNamedModule()` failed.
```
Top of the stack:
```text
clang::ASTContext::setCurrentNamedModule(clang::Module*)
clang::Sema::ActOnModuleDecl(...)
clang::Parser::ParseModuleDecl(...)
clang::Parser::ParseTopLevelDecl(...)
clang::ParseAST(...)
```
### Expected result
Clang should reject the conflicting module declaration/module-map module without asserting.
### Version
Reproduced with an assertions build:
```text
clang version 23.0.0git (https://github.com/llvm/llvm-project.git ae35674951e4d20d45ed6202e641976c9c055f22)
Build config: +assertions
```
### Notes
This looks related to module declaration recovery when a C++ named module declaration conflicts with an existing Clang module-map module of the same name. I also have a nearby single-file reproducer that reaches a `ModuleMap` assertion in the same `Sema::ActOnModuleDecl` path; I will file it separately and cross-link it because it may share the same root cause.
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