[PATCH] D121465: WIP: [clang][modules] Do not report declarations without linkage as ambiguous

[Jan Svoboda via Phabricator via cfe-commits]

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When finalizing the result of name lookup that encountered ambiguity, we check equivalence for declarations with internal linkage. If the declarations are equivalent, we just produce a warning instead of ambiguous result.

In `Sema::isEquivalentInternalLinkageDeclaration` that implements the check, we have a special case for constants of anonymous enums. However, it only kicks in for C++ anonymous enums (since they have `NoLinkage`, meaning they are not externally visible).

In (Objective)C, constants of anonymous enums are `VisibleNoLinkage`, meaning they _are_ externally visible, so the special case doesn't apply for them.

This patch renames the function to `isEquivalentNonExternalLinkageDeclaration` (its documentation already says it handles declarations with "internal/no linkage") and makes it so that even `VisibleNoLinkage` declarations are not marked as ambiguous. This is achieved by using `hasExternalFormalLinkage` instead of `isExternallyVisible` in one of the equivalence checks. Later on, we don't even emit the warning for such declarations, since they are considered the same entity.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D121465

Files:
  clang/include/clang/Sema/Sema.h
  clang/lib/Sema/SemaDeclCXX.cpp
  clang/lib/Sema/SemaLookup.cpp
  clang/lib/Sema/SemaOverload.cpp
  clang/test/Modules/ambiguous-anonymous-enum-lookup.m.cpp

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