c++: ICE with redundant capture [PR108829]

Here we crash in is_capture_proxy:

  /* Location wrappers should be stripped or otherwise handled by the
     caller before using this predicate.  */
  gcc_checking_assert (!location_wrapper_p (decl));

We only crash with the redundant capture:

  int abyPage = [=, abyPage] { ... }

because prune_lambda_captures is only called when there was a default
capture, and with [=] only abyPage won't be in LAMBDA_EXPR_CAPTURE_LIST.

The problem is that LAMBDA_CAPTURE_EXPLICIT_P wasn't propagated
correctly and so var_to_maybe_prune proceeded where it shouldn't.

Co-Authored by: Patrick Palka <ppalka@redhat.com>

	PR c++/108829

gcc/cp/ChangeLog:

	* pt.cc (prepend_one_capture): Set LAMBDA_CAPTURE_EXPLICIT_P.
	(tsubst_lambda_expr): Pass LAMBDA_CAPTURE_EXPLICIT_P to
	prepend_one_capture.

gcc/testsuite/ChangeLog:

	* g++.dg/cpp0x/lambda/lambda-108829-2.C: New test.
	* g++.dg/cpp0x/lambda/lambda-108829.C: New test.

3 files changed, 28 insertions, 3 deletions

diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
index b1ac7d4..1a071e9 100644
--- a/gcc/cp/pt.cc
+++ b/gcc/cp/pt.cc
@@ -19870,10 +19870,11 @@ tsubst_non_call_postfix_expression (tree t, tree args,
 
 /* Subroutine of tsubst_lambda_expr: add the FIELD/INIT capture pair to the
    LAMBDA_EXPR_CAPTURE_LIST passed in LIST.  Do deduction for a previously
-   dependent init-capture.  */
+   dependent init-capture.  EXPLICIT_P is true if the original list had
+   explicit captures.  */
 
 static void
-prepend_one_capture (tree field, tree init, tree &list,
+prepend_one_capture (tree field, tree init, tree &list, bool explicit_p,
 		     tsubst_flags_t complain)
 {
   if (tree auto_node = type_uses_auto (TREE_TYPE (field)))
@@ -19893,6 +19894,7 @@ prepend_one_capture (tree field, tree init, tree &list,
       cp_apply_type_quals_to_decl (cp_type_quals (type), field);
     }
   list = tree_cons (field, init, list);
+  LAMBDA_CAPTURE_EXPLICIT_P (list) = explicit_p;
 }
 
 /* T is a LAMBDA_EXPR.  Generate a new LAMBDA_EXPR for the current
@@ -19982,12 +19984,13 @@ tsubst_lambda_expr (tree t, tree args, tsubst_flags_t complain, tree in_decl)
 	    prepend_one_capture (TREE_VEC_ELT (field, i),
 				 TREE_VEC_ELT (init, i),
 				 LAMBDA_EXPR_CAPTURE_LIST (r),
+				 LAMBDA_CAPTURE_EXPLICIT_P (cap),
 				 complain);
 	}
       else
 	{
 	  prepend_one_capture (field, init, LAMBDA_EXPR_CAPTURE_LIST (r),
-			       complain);
+			       LAMBDA_CAPTURE_EXPLICIT_P (cap), complain);
 
 	  if (id_equal (DECL_NAME (field), "__this"))
 	    LAMBDA_EXPR_THIS_CAPTURE (r) = field;
diff --git a/gcc/testsuite/g++.dg/cpp0x/lambda/lambda-108829-2.C b/gcc/testsuite/g++.dg/cpp0x/lambda/lambda-108829-2.C
new file mode 100644
index 0000000..4e24470
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/lambda/lambda-108829-2.C
@@ -0,0 +1,11 @@
+// PR c++/108829
+// { dg-do compile { target c++11 } }
+
+template<int, class... Ts>
+void f(Ts... ts) {
+  constexpr int IDX_PAGE_SIZE = 4096;
+  int abyPage = [=, ts...] { return IDX_PAGE_SIZE; }();  // { dg-error "redundant" }
+}
+void h() {
+  f<1>(0, 1);
+}
diff --git a/gcc/testsuite/g++.dg/cpp0x/lambda/lambda-108829.C b/gcc/testsuite/g++.dg/cpp0x/lambda/lambda-108829.C
new file mode 100644
index 0000000..e621a0d
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/lambda/lambda-108829.C
@@ -0,0 +1,11 @@
+// PR c++/108829
+// { dg-do compile { target c++11 } }
+
+template <int>
+void f(void) {
+  constexpr int IDX_PAGE_SIZE = 4096;
+  int abyPage = [=, abyPage] { return IDX_PAGE_SIZE; }(); // { dg-error "redundant" }
+}
+void h() {
+  f<1>();
+}