https://llvm.org/bugs/show_bug.cgi?id=23748
Bug ID: 23748
Summary: Tag lookup should not find hidden declarations
Product: clang
Version: trunk
Hardware: PC
OS: All
Status: NEW
Severity: normal
Priority: P
Component: Modules
Assignee: [email protected]
Reporter: [email protected]
CC: [email protected], [email protected]
Classification: Unclassified
Created attachment 14432
--> https://llvm.org/bugs/attachment.cgi?id=14432&action=edit
a test case demonstrating the problem
Currently, LookupResult::isHiddenDeclarationVisible() is defined as follows:
bool isHiddenDeclarationVisible() const {
return AllowHidden || LookupKind == Sema::LookupTagName;
}
This is trying to ensure that elaborated type specifiers are linked into
existing declaration chains even if those declarations are hidden. This is
necessary in C because we don't perform a second redeclaration lookup when the
initial lookup didn't find anything. (It's not necessary in C++ because we
have to perform that redeclaration lookup anyway, because of friends.)
Unfortunately, it can lead to incorrect results if the tag lookup finds
something hidden in an inner scope when it should have found something
non-hidden in an outer scope. That can't happen in C because there's only one
open scope to which modules can add declarations, the global scope; but it can
happen in C++ because of namespaces.
I've attached a simple testcase which reproduces the problem. The code should
compile because the elaborated type specifier should find the non-hidden
declaration ::A from Module.h instead of the hidden declaration ns::A from
Submodule.h.
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