[gcc r12-7851] c++: CTAD and member function references [PR103943]

[gcc r12-7851] c++: CTAD and member function references [PR103943]

[Jason Merrill]

https://gcc.gnu.org/g:8bc5cdaafa2e729f9209684dc30aa0acb72d2580

commit r12-7851-g8bc5cdaafa2e729f9209684dc30aa0acb72d2580
Author: Jason Merrill <jason@redhat.com>
Date:   Sat Mar 26 22:05:53 2022 -0400

    c++: CTAD and member function references [PR103943]
    
    More quirks of rewriting member references to dependent references for
    CTAD.  A reference to a member of dependent scope is definitely dependent.
    And since r11-7044, tsubst_baselink builds a SCOPE_REF, so
    tsubst_qualified_id should just use it.
    
            PR c++/103943
    
    gcc/cp/ChangeLog:
    
            * pt.cc (tsubst_qualified_id): Handle getting SCOPE_REF from
            tsubst_baselink.
            (instantiation_dependent_scope_ref_p): Check dependent_scope_p.
    
    gcc/testsuite/ChangeLog:
    
            * g++.dg/cpp1z/class-deduction109.C: New test.

Diff:
---
 gcc/cp/pt.cc                                    | 21 +++++---
 gcc/testsuite/g++.dg/cpp1z/class-deduction109.C | 64 +++++++++++++++++++++++++
 2 files changed, 79 insertions(+), 6 deletions(-)

diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
index 173bc3a8c7f..b229c9fc739 100644
--- a/gcc/cp/pt.cc
+++ b/gcc/cp/pt.cc
@@ -16590,12 +16590,20 @@ tsubst_qualified_id (tree qualified_id, tree args,
 
   if (dependent_scope_p (scope))
     {
-      if (is_template)
-	expr = build_min_nt_loc (loc, TEMPLATE_ID_EXPR, expr, template_args);
-      tree r = build_qualified_name (NULL_TREE, scope, expr,
-				     QUALIFIED_NAME_IS_TEMPLATE (qualified_id));
-      REF_PARENTHESIZED_P (r) = REF_PARENTHESIZED_P (qualified_id);
-      return r;
+      if (TREE_CODE (expr) == SCOPE_REF)
+	/* We built one in tsubst_baselink.  */
+	gcc_checking_assert (same_type_p (scope, TREE_OPERAND (expr, 0)));
+      else
+	{
+	  if (is_template)
+	    expr = build_min_nt_loc (loc, TEMPLATE_ID_EXPR, expr,
+				     template_args);
+	  expr = build_qualified_name (NULL_TREE, scope, expr,
+				       QUALIFIED_NAME_IS_TEMPLATE
+				       (qualified_id));
+	}
+      REF_PARENTHESIZED_P (expr) = REF_PARENTHESIZED_P (qualified_id);
+      return expr;
     }
 
   if (!BASELINK_P (name) && !DECL_P (expr))
@@ -27334,6 +27342,7 @@ instantiation_dependent_scope_ref_p (tree t)
 {
   if (DECL_P (TREE_OPERAND (t, 1))
       && CLASS_TYPE_P (TREE_OPERAND (t, 0))
+      && !dependent_scope_p (TREE_OPERAND (t, 0))
       && !unknown_base_ref_p (t)
       && accessible_in_template_p (TREE_OPERAND (t, 0),
 				   TREE_OPERAND (t, 1)))
diff --git a/gcc/testsuite/g++.dg/cpp1z/class-deduction109.C b/gcc/testsuite/g++.dg/cpp1z/class-deduction109.C
new file mode 100644
index 00000000000..e621ebad28a
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp1z/class-deduction109.C
@@ -0,0 +1,64 @@
+// PR c++/103943
+// { dg-do compile { target c++17 } }
+
+template<typename R, typename...AA> struct F0 { //OK
+    R(*fun_ptr)(AA...);
+};
+template<typename R, typename...AA> struct F1 { //OK
+    R(*fun_ptr)(AA...);
+    F1(R(*fun_ptr)(AA...)) : fun_ptr(fun_ptr) {}
+};
+template<typename R, typename...AA> struct F2 { //OK
+    R(*fun_ptr)(AA...);
+    using fun_ptr_t = decltype(fun_ptr);
+    F2(fun_ptr_t fun_ptr) : fun_ptr(fun_ptr) {}
+};
+template<typename R, typename...AA> struct F3 {
+    R(*fun_ptr)(AA...);
+//  using fun_ptr_t = decltype(fun_ptr); //OK as in F2
+    using fun_ptr_t = decltype(F3::fun_ptr); //ICE: Segmentation fault
+//  using fun_ptr_t = decltype(F3<R, AA...>::fun_ptr); //ICE: Segmentation fault
+    F3(fun_ptr_t fun_ptr) : fun_ptr(fun_ptr) {}
+};
+template<typename R, typename...AA> struct F4 {
+    static R fun_not_implemented(AA...);
+//  using fun_ptr_t = decltype(&fun_not_implemented); //OK
+    using fun_ptr_t = decltype(&F4::fun_not_implemented); //OK with aggregate initialization (no ctor)
+//  using fun_ptr_t = decltype(&F4<R, AA...>::fun_not_implemented); //OK with aggregate initialization (no ctor)
+    fun_ptr_t fun_ptr;
+};
+template<typename R, typename...AA> struct F5 { //OK
+    static R fun_not_implemented(AA...);
+    using fun_ptr_t = decltype(&fun_not_implemented);
+    fun_ptr_t fun_ptr;
+    F5(fun_ptr_t fun_ptr) : fun_ptr(fun_ptr) {}
+};
+template<typename R, typename...AA> struct F6 {
+    static R fun_not_implemented(AA...);
+//  using fun_ptr_t = decltype(&fun_not_implemented); //OK as in F5
+    using fun_ptr_t = decltype(&F6::fun_not_implemented); //ICE: in build_qualified_name, at cp/tree.c:2238
+//  using fun_ptr_t = decltype(&F6<R, AA...>::fun_not_implemented); //ICE: in build_qualified_name, at cp/tree.c:2238
+    fun_ptr_t fun_ptr;
+    F6(fun_ptr_t fun_ptr) : fun_ptr(fun_ptr) {}
+};
+template<typename R, typename...AA> F0(R(*fun_ptr)(AA...)) -> F0<R, AA...>;
+template<typename R, typename...AA> F1(R(*fun_ptr)(AA...)) -> F1<R, AA...>;
+template<typename R, typename...AA> F2(R(*fun_ptr)(AA...)) -> F2<R, AA...>;
+template<typename R, typename...AA> F3(R(*fun_ptr)(AA...)) -> F3<R, AA...>;
+template<typename R, typename...AA> F4(R(*fun_ptr)(AA...)) -> F4<R, AA...>;
+template<typename R, typename...AA> F5(R(*fun_ptr)(AA...)) -> F5<R, AA...>;
+template<typename R, typename...AA> F6(R(*fun_ptr)(AA...)) -> F6<R, AA...>;
+
+int fun(int a) {
+    return a + 1;
+}
+#pragma GCC diagnostic ignored "-Wunused-but-set-variable"
+void test() {
+    auto f0 = F0{&fun}; //OK
+    auto f1 = F1{&fun}; //OK
+    auto f2 = F2{&fun}; //OK
+    auto f3 = F3{&fun}; //ICE: Segmentation fault
+    auto f4 = F4{&fun}; //OK
+    auto f5 = F5{&fun}; //OK
+    auto f6 = F6{&fun}; //ICE: in build_qualified_name, at cp/tree.c:2238
+}