[Bug c++/65284] [5 Regression] ICE (segfault) on arm-linux-gnueabihf

["aldyh at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65284

--- Comment #6 from Aldy Hernandez <aldyh at gcc dot gnu.org> ---
For the construction of the lambda in the simplified testcase I have just
uploaded:

  MaybeInt().xmap([abc](int childId)
          {
            return ParsedSchema(bark, childId + 666);
          });

We initially generate the following tree:

ParsedSchema::findNested()::<lambda(int)> (const struct __lambda0 * const
__closure, int childId)
{
  const int abc [value-expr: __closure->__abc];

  <<cleanup_point return D.2331 = <<< Unknown tree: aggr_init_expr
  6
  __comp_ctor 
  *NON_LVALUE_EXPR <this>
  NON_LVALUE_EXPR <this>
  *NON_LVALUE_EXPR <this> = bark;, <<< Unknown tree: empty_class_expr >>>;
  childId + 666 >>>>>;
}

Whose AGGR_INIT_EXPR will be gimplified into:

ParsedSchema::findNested()::<lambda(int)> (const struct __lambda0 * const
__closure, int childId)
{
  const int abc [value-expr: __closure->__abc];

  <<cleanup_point return D.2331 = ParsedSchema::ParsedSchema (&*NON_LVALUE_EXPR
<this>, *NON_LVALUE_EXPR <this> = bark;, <<< Unknown tree: empty_class_expr
>>>;, childId + 666)>>;
}

Notice the non-existent return value from ParsedSchema::ParsedSchema is being
read from, and constructors do not return anything.  I suppose D.2331 should be
set from NON_LVALUE_EXPR<this>, although even the assignment into
*NON_LVALUE_EXPR looks odd.  Isn't a NON_LVALUE_EXPR by definition not
assignable?

Before the patch that broke this, we had:

  <<cleanup_point return <retval> = TARGET_EXPR <D.2133, <<< Unknown tree:
aggr_init_expr
  6
  __comp_ctor 
  D.2133
  (struct ParsedSchema *) 0
  TARGET_EXPR <D.2123, bark>;, <<< Unknown tree: empty_class_expr >>>;
  childId + 666 >>>>;, D.2133>>;

Notice the TARGET_EXPR, which then does the right thing when gimplified.