[PATCH] D124351: [Clang] Implement Change scope of lambda trailing-return-type

[Corentin Jabot via Phabricator via cfe-commits]

cor3ntin added a comment.

In D124351#4101611 <https://reviews.llvm.org/D124351#4101611>, @rupprecht wrote:

> Hi, me again :)
>
> I ran into an interesting build breakage from this, I can't tell if it's a legitimate breakage based on reading P2036R3 and P2579R0 (mostly I'm not a language lawyer).
>
>   struct StringLiteral {
>     template <int N>
>     StringLiteral(const char (&array)[N])
>         __attribute__((enable_if(N > 0 && N == __builtin_strlen(array) + 1,
>                                  "invalid string literal")));
>   };
>   
>   struct Message {
>     Message(StringLiteral);
>   };
>   
>   void Func1() {
>     auto x = Message("x");  // Note: this is fine
>   
>     // Note: "xx\0" to force a different type, StringLiteral<3>, otherwise this
>     // successfully builds.
>     auto y = [&](decltype(Message("xx"))) {};
>   
>     // ^ fails with: repro.cc:18:13: error: reference to local variable 'array'
>     // declared in enclosing function 'StringLiteral::StringLiteral<3>'
>   
>     (void)x;
>     (void)y;
>   }
>
> https://godbolt.org/z/M4E6jKxxn
>
> Does this look like an intended breakage from this patch?

Looks like we fail to enter the appropriate context when evaluating the lambda, definitely


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