I totally agree on the connection of the words "declared return type"
with the conversion-function-id.
That's why I originally expressed that type-specifier-seq already includes
the case of conversion-function-id.

I'm not sure what your remaining question is, then. Can you give an example?
 

About p2, thank you to highlight its context.
However, I wonder two details, that likely biased my attention in missing
to focus on the correct context:

a) how a trailing-return-type may be persent in one of those context ?
    Currently, I interpret "The type of a parameter-declaration of" (one of three cases),
    because all three cases include parameter-declaration clause in their syntax,
    but another possible interpretation might be "The type of" (one of the three cases),
    that is, applying parameter declaration only to the function declaration.
    Do you believe the text may be clarified to avoid such ambiguity ?

Well, the alternative interpretation is absurd, because you don't get to declare the type of a lambda. But, ideally, it should be possible to parse the sentence without needing semantic knowledge about C++, so, yes, I think this should be clarified. I think this would be an editorial-level change, so please submit an issue here: https://github.com/cplusplus/draft/issues
And attach a pull request, if you can.
 
    Does it affect the way a trailing-return-type may be in place ?

I'm not understanding the question.
 

b) do you believe that the words 'see below' in the p2 statement
    "... in a trailing-return-type that specifies the type that replaces
      such a decl-specifier (see below)"
    are still applicable ?
    The only interpretation I see for them is about type replacement,
    which is already well discussed in [dcl.fct]-p(1.3)
    In the old text of C++20, there was a p3 (corresponding to
    p3 and p4 of the current new draft) that read
    "... that trailing-return-type specifies the declared return type of the function."
    which was redundant compared to [dcl.fct]-p(1.3).
    Should the redundancy be removed also in p2 about the words 'see below' ?
    Is it possible that 'see below' refers §9.3.4.6 [dcl.fct]
    from §9.2.9.7.1 [decl.spec.auto.general] ? A reference may be better ?


The "see below" in p2 refers to p3. To understand what it means, notice that we have the same language in p5, except without "see below" since it's not a forward reference from p5. We have this example:

auto (*fp)() -> auto = f;       // OK

The second `auto` is in "the trailing-return-type that specifies the type that replaces" the first `auto`.

You can have this in a parameter declaration too:

 

will also wait for a comment on the original third point:
trailing return type -> trailing-return-type
in [class.conv.fct]-p3


as well as about the topic in
related to [dcl.type.auto.deduct]-p3.


--
Brian Bi