diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index d80c15d2168..aa42de2c05f 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,3 +1,10 @@
+2018-05-08  Paolo Carlini  <paolo.carlini@oracle.com>
+
+	PR c++/84588
+	* parser.c (cp_parser_parameter_declaration_list): When the
+	entire parameter-declaration-list is erroneous maybe call
+	abort_fully_implicit_template.
+
 2018-05-08  Marek Polacek  <polacek@redhat.com>
 
 	PR c++/85695
diff --git a/gcc/cp/parser.c b/gcc/cp/parser.c
index f8ecf030c0d..59829f3a7fe 100644
--- a/gcc/cp/parser.c
+++ b/gcc/cp/parser.c
@@ -21344,6 +21344,8 @@ cp_parser_parameter_declaration_list (cp_parser* parser, bool *is_error)
 	{
 	  *is_error = true;
 	  parameters = error_mark_node;
+	  if (parser->fully_implicit_function_template_p)
+	    abort_fully_implicit_template (parser);
 	  break;
 	}
 
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 3bfeb894b9b..68c0033b511 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2018-05-08  Paolo Carlini  <paolo.carlini@oracle.com>
+
+	PR c++/84588
+	* g++.dg/cpp1y/pr84588.C: New.
+
 2018-05-08  Marek Polacek  <polacek@redhat.com>
 
 	PR c++/85695
diff --git a/gcc/testsuite/g++.dg/cpp1y/pr84588.C b/gcc/testsuite/g++.dg/cpp1y/pr84588.C
new file mode 100644
index 00000000000..9d7f9027b45
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp1y/pr84588.C
@@ -0,0 +1,10 @@
+// { dg-do compile { target c++14 } }
+// { dg-options "-w" }
+
+struct a {
+  void b() {}
+  void c(auto = [] {
+    if (a a(int auto){})  // { dg-error "two or more data types" }
+      ;
+  }) {}
+};