Enhance "returning address of local var" checker

[Quuxplusone]

Bugzilla Link	PR38878
Status	NEW
Importance	P enhancement
Reported by	David Bolvansky (david.bolvansky@gmail.com)
Reported on	2018-09-09 09:57:18 -0700
Last modified on	2018-09-09 09:58:39 -0700
Version	trunk
Hardware	PC Linux
CC	dgregor@apple.com, llvm-bugs@lists.llvm.org
Fixed by commit(s)
Attachments
Blocks
Blocked by
See also

struct S&& po() {
    struct S tmp;
    return std::move(tmp);
}

No warning from Clang.

GCC warns:
<source>: In function 'S&& po()':
<source>:14:23: warning: function returns address of local variable [-Wreturn-
local-addr]
14 |     return std::move(tmp);
   |                       ^
<source>:13:14: note: declared here
13 |     struct S tmp;

[Quuxplusone]

• std::forward too