Cv-qualification of prvalues during reference binding

Question

Consider this example:

const int& r2 = 5;

The rules governing reference-initialization are found in [dcl.init.ref]/5:

A reference to type “cv1 T1” is initialized by an expression of type “cv2 T2” as follows:

• (5.1) [..]
• (5.2) [..]
• (5.3) Otherwise, if the initializer expression
  • (5.3.1) is an rvalue [..] and “cv1 T1” is reference-compatible with “cv2 T2”, or
  • (5.3.2) [..]

then the initializer expression [..] is called the converted initializer. If the converted initializer is a prvalue, its type T4 is adjusted to type “cv1 T4” ([conv.qual]) and the temporary materialization conversion ([conv.rval]) is applied. In any case, the reference is bound to the resulting glvalue [..].

Here, The converted initializer is a prvalue of type T4 (int); then it's adjusted to cv1 T4 (const int). But [expr.type]/2 states:

If a prvalue initially has the type “cv T”, where T is a cv-unqualified non-class, non-array type, the type of the expression is adjusted to T prior to any further analysis.

One said to me that this rule ([expr.type]/2) does not apply to specifically this case. And I need to know the reason behind that.

I claim that the reason for not applying [expr.type]/2 is because initially (before adjustment) the type of the prvalue is T4 (int) i.e, it's cv-unqualified type, so [expr.type]/2 cannot be applied since the initial type of the prvalue is not cv-qualified type. Even after the adjustment to cv1 T4, the rule [expr.type]/2 also doesn't apply because cv1 T4 is not the initial type of the prvalue. My question is: Are those correct reasons?

Indeed both questions this and this are relatively similar but specifically I'm asking a specific, different question regarding the rule [expr.type]/2.

Answer 1

IMO the mentioned case (const int& r2 = 5;) should fall into [dcl.init.ref]/(5.4.2). I think this is related to a mischange introduced by P0135R1 and fixed by CWG2481.

One said to me that this rule ([expr.type]/2) does not apply to specifically this case. And I need to know the reason behind that.

I think that is a non-standard comprehension of the cases addressed by CWG2481, which should be equivalent to the standard one. That is just saying "cv-qualification is not stripped".

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Perhaps the use of "rvalue" in [dcl.init.ref]/(5.3.1) is wrong unintended and the value category should be "xvalue". I'll contact CWG chair for clarification.

I've opened an editorial issue #5821 to ask whether "its type T4 is adjusted to type “cv1 T4”" (5.3) and "considering the type of the prvalue to be “cv1 T1”" (5.4.2) have the same meaning.

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Edit: CWG2657 has been opened for this.