From 775670d792fb8ff314ed519ff295583ab31d90ef Mon Sep 17 00:00:00 2001
From: Jakub Jelinek <jakub@redhat.com>
Date: Tue, 17 Dec 2019 22:40:14 +0100
Subject: [PATCH] re PR c++/59655 (incorrect diagnostic on templatized function
 with lambda parameter)

	PR c++/59655
	* pt.c (push_tinst_level_loc): If limit_bad_template_recursion,
	set TREE_NO_WARNING on tldcl.
	* decl2.c (no_linkage_error): Treat templates with TREE_NO_WARNING
	as defined during error recovery.

	* g++.dg/cpp0x/diag3.C: New test.

From-SVN: r279470
---
 gcc/cp/ChangeLog                   |  8 ++++++++
 gcc/cp/decl2.c                     |  9 ++++++++-
 gcc/cp/pt.c                        |  7 ++++++-
 gcc/testsuite/ChangeLog            |  3 +++
 gcc/testsuite/g++.dg/cpp0x/diag3.C | 20 ++++++++++++++++++++
 5 files changed, 45 insertions(+), 2 deletions(-)
 create mode 100644 gcc/testsuite/g++.dg/cpp0x/diag3.C

diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index a64bb164664..6b5849e45b3 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,3 +1,11 @@
+2019-12-17  Jakub Jelinek  <jakub@redhat.com>
+
+	PR c++/59655
+	* pt.c (push_tinst_level_loc): If limit_bad_template_recursion,
+	set TREE_NO_WARNING on tldcl.
+	* decl2.c (no_linkage_error): Treat templates with TREE_NO_WARNING
+	as defined during error recovery.
+
 2019-12-13  Jason Merrill  <jason@redhat.com>
 
 	PR c++/91165 - verify_gimple ICE with cached constexpr.
diff --git a/gcc/cp/decl2.c b/gcc/cp/decl2.c
index 46cc58265a6..ea83210fecb 100644
--- a/gcc/cp/decl2.c
+++ b/gcc/cp/decl2.c
@@ -4414,7 +4414,14 @@ decl_maybe_constant_var_p (tree decl)
 void
 no_linkage_error (tree decl)
 {
-  if (cxx_dialect >= cxx11 && decl_defined_p (decl))
+  if (cxx_dialect >= cxx11
+      && (decl_defined_p (decl)
+	  /* Treat templates which limit_bad_template_recursion decided
+	     not to instantiate as if they were defined.  */
+	  || (errorcount + sorrycount > 0
+	      && DECL_LANG_SPECIFIC (decl)
+	      && DECL_TEMPLATE_INFO (decl)
+	      && TREE_NO_WARNING (decl))))
     /* In C++11 it's ok if the decl is defined.  */
     return;
   tree t = no_linkage_check (TREE_TYPE (decl), /*relaxed_p=*/false);
diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index 6f658de28ed..fe6cfc2590b 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -10640,7 +10640,12 @@ push_tinst_level_loc (tree tldcl, tree targs, location_t loc)
      anything else.  Do allow deduction substitution and decls usable in
      constant expressions.  */
   if (!targs && limit_bad_template_recursion (tldcl))
-    return false;
+    {
+      /* Avoid no_linkage_errors and unused function warnings for this
+	 decl.  */
+      TREE_NO_WARNING (tldcl) = 1;
+      return false;
+    }
 
   /* When not -quiet, dump template instantiations other than functions, since
      announce_function will take care of those.  */
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 0ba27eba78b..a3125166f97 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,5 +1,8 @@
 2019-12-17  Jakub Jelinek  <jakub@redhat.com>
 
+	PR c++/59655
+	* g++.dg/cpp0x/diag3.C: New test.
+
 	PR target/92841
 	* gcc.target/i386/pr92841.c: New test.
 
diff --git a/gcc/testsuite/g++.dg/cpp0x/diag3.C b/gcc/testsuite/g++.dg/cpp0x/diag3.C
new file mode 100644
index 00000000000..7409b30fb4b
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/diag3.C
@@ -0,0 +1,20 @@
+// PR c++/59655
+// { dg-do compile { target c++11 } }
+
+template<typename T> struct A { static constexpr bool value = false; };
+
+struct B {
+  template<typename T>
+  B (T t)
+  {
+    static_assert (A<T>::value, "baz");		// { dg-error "static assertion failed" }
+    foo (t);
+  }
+  template<typename T> void foo (T) {}		// { dg-bogus "used but never defined" }
+};
+
+int
+main ()
+{
+  B t([](int) { });
+}
-- 
2.30.2