Proposed resolution (September, 2021):

Change 6.4.3 [basic.scope.block] bullet 2.2 as follows:

If a declaration whose target scope is the block scope S of a

• compound-statement of a lambda-expression, function-body, or function-try-block,

• substatement of a selection or iteration statement that is not itself a selection or iteration statement, or

• handler of a function-try-block

potentially conflicts with a declaration whose target scope is the parent scope of S, the program is ill-formed.

(See editorial issue 4843.)

[Accepted at the February, 2022 meeting.]

The changes of P1787R6 inadvertently made constructs like

  if (int a = 1)
    if (int a = 1)
      ...

ill-formed.