BugSuppression works by traversing the lexical decl context of the
decl-with-issue to record what source ranges should be suppressed by
some attribute.
Note that the decl-with-issue will be changed to the lexical decl
context of the original decl-with-issue, to make suppression attributes
work that were attached to the CXXRecordDecl containing the
CXXMethodDecl (bug report's DeclWithIssue).
It happens so that it uses a DynamicRecursiveASTVisitor, which has a
couple of traversal options. Namely:
- ShouldVisitTemplateInstantiations
- ShouldWalkTypesOfTypeLocs
- ShouldVisitImplicitCode
- ShouldVisitLambdaBody
By default, these have the correct values, except for
ShouldVisitTemplateInstantiations. We should traverse template
instantiations because that might be where the bug is reported - thus,
where we might have a [[clang::suppress]] that we should honor.
In this patch I'll explicitly set these traversal options to avoid
further confusion.
rdar://164646398
The attribute is now allowed on an assortment of declarations, to
suppress warnings related to declarations themselves, or all warnings in
the lexical scope of the declaration.
I don't necessarily see a reason to have a list at all, but it does look
as if some of those more niche items aren't properly supported by the
compiler itself so let's maintain a short safe list for now.
The initial implementation raised a question whether the attribute
should apply to lexical declaration context vs. "actual" declaration
context. I'm using "lexical" here because it results in less warnings
suppressed, which is the conservative behavior: we can always expand it
later if we think this is wrong, without breaking any existing code. I
also think that this is the correct behavior that we will probably never
want to change, given that the user typically desires to keep the
suppressions as localized as possible.
