[gcc(refs/vendors/ARM/heads/arm-perf-staging)] c++: Fix lambda in atomic constraint.

[Tamar Christina]

https://gcc.gnu.org/g:1e166191ef330f3491d405bf3eb09b2b796c9b0e

commit 1e166191ef330f3491d405bf3eb09b2b796c9b0e
Author: Jason Merrill <jason@redhat.com>
Date:   Sat Feb 15 14:48:08 2020 +0100

    c++: Fix lambda in atomic constraint.
    
    find_template_parameters needs to find the mention of T in the lambda.
    Fixing that leaves this as a hard error, which may be surprising but is
    consistent with lambdas in other SFINAE contexts like template argument
    deduction.
    
    gcc/cp/ChangeLog
    2020-02-15  Jason Merrill  <jason@redhat.com>
    
            PR c++/92556
            * pt.c (any_template_parm_r): Look into lambda body.

Diff:
---
 gcc/cp/ChangeLog                              |  3 +++
 gcc/cp/pt.c                                   |  9 +++++++++
 gcc/testsuite/g++.dg/cpp2a/concepts-lambda5.C | 10 ++++++++++
 3 files changed, 22 insertions(+)

diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index ed6b0d0207e..6ac938b4d2b 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,5 +1,8 @@
 2020-02-15  Jason Merrill  <jason@redhat.com>
 
+	PR c++/92556
+	* pt.c (any_template_parm_r): Look into lambda body.
+
 	PR c++/92583
 	* pt.c (any_template_parm_r): Remove CONSTRUCTOR handling.
 
diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index d19bde7bcbe..6c9abb8f3d3 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -10479,6 +10479,15 @@ any_template_parm_r (tree t, void *data)
       }
       break;
 
+    case LAMBDA_EXPR:
+      {
+	/* Look in the parms and body.  */
+	tree fn = lambda_function (t);
+	WALK_SUBTREE (TREE_TYPE (fn));
+	WALK_SUBTREE (DECL_SAVED_TREE (fn));
+      }
+      break;
+
     default:
       break;
     }
diff --git a/gcc/testsuite/g++.dg/cpp2a/concepts-lambda5.C b/gcc/testsuite/g++.dg/cpp2a/concepts-lambda5.C
new file mode 100644
index 00000000000..fe471899c14
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/concepts-lambda5.C
@@ -0,0 +1,10 @@
+// PR c++/92556
+// { dg-do compile { target c++2a } }
+
+// Having this as a hard error is consistent with template argument deduction;
+// it's an open core issue (jason 2020-02-14).
+template <class T> concept has_value
+  = requires { []{T::value;}; }; // { dg-error "" }
+template <has_value T> void f() { }
+template <class T> void f() { }
+void q() { f<int>(); }