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List:       cfe-commits
Subject:    Re: [PATCH] D11194: Instantiate function declarations in instantiated functions.
From:       Serge Pavlov via cfe-commits <cfe-commits () lists ! llvm ! org>
Date:       2015-08-18 17:05:13
Message-ID: 9a1076bb86197901f64639cb34719a0d () localhost ! localdomain
[Download RAW message or body]

sepavloff added inline comments.

================
Comment at: lib/AST/DeclBase.cpp:273
@@ +272,3 @@
+    return true;
+  if (const CXXRecordDecl *ClassD = dyn_cast<CXXRecordDecl>(LDC))
+    return ClassD->isLocalClass() && !ClassD->isLambda();;
----------------
rsmith wrote:
> It's not necessary for this change, but to match its documentation this function \
> should handle other kinds of `TagDecl` too (enums, C structs). Something like: 
> do {
> if (LDC->isFunctionOrMethod())
> return true;
> if (!isa<TagDecl>(LDC))
> return false;
> LDC = LDC->getLexicalParent();
> } while (LDC);
> return false;
> 
> ... maybe?
The proposed code recognizes lambda as lexically contained within a function. As a \
result, the following test starts to fail (obtained from \
CXX\expr\expr.prim\expr.prim.lambda\default-arguments.cpp): ```
struct NoDefaultCtor {
  NoDefaultCtor(const NoDefaultCtor&); // expected-note{{candidate constructor}}
  ~NoDefaultCtor();
};

template<typename T>
void defargs_in_template_unused(T t) {
  auto l1 = [](const T& value = T()) { };
  l1(t);
}

template void defargs_in_template_unused(NoDefaultCtor);
```
because default value for lambda argument cannot be instantiated. It is not clear \
whether instantiation of the lambda default argument must always occur similar to \
DR1484. I couldn't find appropriate place in the standard. According to spirit it \
shouldn't as lambda is not a separate declaration but a part of instantiated content. \
If so  14.6.4.1p2 is more likely to be applied and the above test must pass.

Maybe we need to rename `isLexicallyWithinFunctionOrMethod` to \
`shouldBeAlwaysInstantiated` or something like that to avoid misunderstanding?



http://reviews.llvm.org/D11194



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