llvm-project

63c29df8 - [Serialization] Fix assertion on re-deserialized friend template spec… (#200566)

[Serialization] Fix assertion on re-deserialized friend template spec… (#200566) …ialization in PCH (#198133) A friend function-template specialization declared inside a class template is serialized into a PCH. When the class template is later instantiated while loading the PCH, the friend specialization can be deserialized re-entrantly (VisitFriendDecl -> VisitFunctionDecl -> ... -> VisitFunctionDecl for the same specialization) at the same time as the canonical copy, producing two redeclarations of the same specialization in the template's specialization set. ASTDeclReader::VisitFunctionDecl asserted that this collision could only happen when merging declarations from different modules. Since 38b3d87bd384, friend functions defined inside dependent class templates are loaded eagerly, so the collision can now also occur within a single PCH/AST file (non-modules build), tripping the assertion: Assertion failed: (Reader.getContext().getLangOpts().Modules && "already deserialized this template specialization"), function VisitFunctionDecl The merge that follows (mergeRedeclarable) already links the two redeclarations correctly regardless of whether modules are enabled, so the fix is to drop the modules-only assumption and let the merge run. Fixes https://github.com/llvm/llvm-project/issues/198133