[Bug c++/79133] New: lambda capture shadowing parameter & decltype confusion

[nathan at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79133

            Bug ID: 79133
           Summary: lambda capture shadowing parameter & decltype
                    confusion
           Product: gcc
           Version: 7.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: nathan at gcc dot gnu.org
  Target Milestone: ---

Created attachment 40535
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=40535&action=edit
reproducer

When a simple lambda capture and a lambda parameter share a name, the capture
object is seen inside the lambda.  Except inside decltype, which sees the
parameter.

The attached testcase produces (at -O2):

        subq    $8, %rsp
        movl    $1, %edi <-- size of lambda parm 'z'
        call    _Z3Barj
        movl    $4, %edi <-- size of lambda capture 'z'
        call    _Z3Barj
        movl    $5, %eax <-- value of lambda capture 'z'
        addq    $8, %rsp
        ret

Possibly related email:
https://gcc.gnu.org/ml/gcc-patches/2017-01/msg01331.html