[gcc r14-6026] c++: lambda capture and explicit object parm

[Jason Merrill]

https://gcc.gnu.org/g:73e2bdbf9bed48b2b30691f03e79230bff4850c6

commit r14-6026-g73e2bdbf9bed48b2b30691f03e79230bff4850c6
Author: Jason Merrill <jason@redhat.com>
Date:   Wed Nov 29 21:51:36 2023 -0500

    c++: lambda capture and explicit object parm
    
    More adjustments to allow for explicit object parameters in lambdas.  This
    has no practical effect until that patch goes in, but applying this
    separately seems reasonable.
    
    gcc/cp/ChangeLog:
    
            * semantics.cc (finish_non_static_data_member)
            (finish_decltype_type, capture_decltype):
            Handle deduced closure parameter.

Diff:
---
 gcc/cp/semantics.cc | 26 ++++++++++++++++++++++----
 1 file changed, 22 insertions(+), 4 deletions(-)

diff --git a/gcc/cp/semantics.cc b/gcc/cp/semantics.cc
index 36b57ac9524..fbbc18336a0 100644
--- a/gcc/cp/semantics.cc
+++ b/gcc/cp/semantics.cc
@@ -2262,6 +2262,16 @@ finish_non_static_data_member (tree decl, tree object, tree qualifying_scope,
       else if (PACK_EXPANSION_P (type))
 	/* Don't bother trying to represent this.  */
 	type = NULL_TREE;
+      else if (WILDCARD_TYPE_P (TREE_TYPE (object)))
+	/* We don't know what the eventual quals will be, so punt until
+	   instantiation time.
+
+	   This can happen when called from build_capture_proxy for an explicit
+	   object lambda.  It's a bit marginal to call this function in that
+	   case, since this function is for references to members of 'this',
+	   but the deduced type is required to be derived from the closure
+	   type, so it works.  */
+	type = NULL_TREE;
       else
 	{
 	  /* Set the cv qualifiers.  */
@@ -11682,6 +11692,7 @@ finish_decltype_type (tree expr, bool id_expression_or_member_access_p,
      A<decltype(sizeof(T))>::U doesn't require 'typename'.  */
   if (instantiation_dependent_uneval_expression_p (expr))
     {
+    dependent:
       type = cxx_make_type (DECLTYPE_TYPE);
       DECLTYPE_TYPE_EXPR (type) = expr;
       DECLTYPE_TYPE_ID_EXPR_OR_MEMBER_ACCESS_P (type)
@@ -11856,7 +11867,11 @@ finish_decltype_type (tree expr, bool id_expression_or_member_access_p,
       if (outer_automatic_var_p (STRIP_REFERENCE_REF (expr))
 	  && current_function_decl
 	  && LAMBDA_FUNCTION_P (current_function_decl))
-	type = capture_decltype (STRIP_REFERENCE_REF (expr));
+	{
+	  type = capture_decltype (STRIP_REFERENCE_REF (expr));
+	  if (!type)
+	    goto dependent;
+	}
       else if (error_operand_p (expr))
 	type = error_mark_node;
       else if (expr == current_class_ptr)
@@ -12754,7 +12769,8 @@ apply_deduced_return_type (tree fco, tree return_type)
 
 /* DECL is a local variable or parameter from the surrounding scope of a
    lambda-expression.  Returns the decltype for a use of the capture field
-   for DECL even if it hasn't been captured yet.  */
+   for DECL even if it hasn't been captured yet.  Or NULL_TREE if we can't give
+   a correct answer at this point and we should build a DECLTYPE_TYPE.  */
 
 static tree
 capture_decltype (tree decl)
@@ -12792,9 +12808,11 @@ capture_decltype (tree decl)
 
   if (!TYPE_REF_P (type))
     {
-      int quals = cp_type_quals (type);
       tree obtype = TREE_TYPE (DECL_ARGUMENTS (current_function_decl));
-      gcc_checking_assert (!WILDCARD_TYPE_P (non_reference (obtype)));
+      if (WILDCARD_TYPE_P (non_reference (obtype)))
+	/* We don't know what the eventual obtype quals will be.  */
+	return NULL_TREE;
+      int quals = cp_type_quals (type);
       if (INDIRECT_TYPE_P (obtype))
 	quals |= cp_type_quals (TREE_TYPE (obtype));
       type = cp_build_qualified_type (type, quals);