[C++ PATCH] PR c++/91930 - ICE with constrained inherited default ctor.

[Jason Merrill]

The testcase was crashing because lazily_declare_fn was failing to add a
defaulted constructor, because the implicit declaration was less constrained
than the inherited default constructor.  But when we have an inherited
constructor, we shouldn't be trying to declare a default constructor in the
first place, because it counts as "a user-declared constructor".  With that
fixed I needed to adjust a couple of inherited constructor testcases that
previously had been diagnosing the default constructor as deleted rather
than not declared.

Tested x86_64-pc-linux-gnu, applying to trunk.

	* name-lookup.c (do_class_using_decl): Set TYPE_HAS_USER_CONSTRUCTOR
	for inherited constructor.
---
 gcc/cp/name-lookup.c                                |  1 +
 gcc/testsuite/g++.dg/cpp0x/inh-ctor5.C              |  4 ++--
 gcc/testsuite/g++.dg/cpp1z/inh-ctor22.C             |  4 ++--
 gcc/testsuite/g++.dg/cpp2a/concepts-inherit-ctor6.C | 12 ++++++++++++
 4 files changed, 17 insertions(+), 4 deletions(-)
 create mode 100644 gcc/testsuite/g++.dg/cpp2a/concepts-inherit-ctor6.C

diff --git a/gcc/cp/name-lookup.c b/gcc/cp/name-lookup.c
index 57ab129c9ec..9352ce5da0b 100644
--- a/gcc/cp/name-lookup.c
+++ b/gcc/cp/name-lookup.c
@@ -4613,6 +4613,7 @@ do_class_using_decl (tree scope, tree name)
       maybe_warn_cpp0x (CPP0X_INHERITING_CTORS);
       name = ctor_identifier;
       CLASSTYPE_NON_AGGREGATE (current_class_type) = true;
+      TYPE_HAS_USER_CONSTRUCTOR (current_class_type) = true;
     }
 
   /* Cannot introduce a constructor name.  */
diff --git a/gcc/testsuite/g++.dg/cpp0x/inh-ctor5.C b/gcc/testsuite/g++.dg/cpp0x/inh-ctor5.C
index d0038c16a14..673b6380504 100644
--- a/gcc/testsuite/g++.dg/cpp0x/inh-ctor5.C
+++ b/gcc/testsuite/g++.dg/cpp0x/inh-ctor5.C
@@ -6,13 +6,13 @@ struct B1 {
 struct B2 {
   B2(double) { }
 };
-struct D1 : B1 {    // { dg-error "no match" }
+struct D1 : B1 {
   using B1::B1;	    // implicitly declares D1(int)
   int x;
 };
 void test() {
   D1 d(6);	    // OK: d.x is not initialized
-  D1 e;		    // { dg-error "deleted" } D1 has no default constructor
+  D1 e;		    // { dg-error "no match" } D1 has no default constructor
 }
 struct D2 : B2 {
   using B2::B2;	    // { dg-error "B1::B1" }
diff --git a/gcc/testsuite/g++.dg/cpp1z/inh-ctor22.C b/gcc/testsuite/g++.dg/cpp1z/inh-ctor22.C
index 02ec58a3e8e..98336a158c1 100644
--- a/gcc/testsuite/g++.dg/cpp1z/inh-ctor22.C
+++ b/gcc/testsuite/g++.dg/cpp1z/inh-ctor22.C
@@ -12,7 +12,7 @@ struct B2 {
 
 int get();
 
-struct D1 : B1 {		// { dg-message "B1::B1" }
+struct D1 : B1 {
   using B1::B1;  // inherits B1(int, ...)
   int x;
   int y = get();
@@ -22,7 +22,7 @@ void test() {
   D1 d(2, 3, 4); // OK: B1 is initialized by calling B1(2, 3, 4),
   // then d.x is default-initialized (no initialization is performed),
   // then d.y is initialized by calling get()
-  D1 e;          // { dg-error "" } D1 has a deleted default constructor
+  D1 e;          // { dg-error "" } D1 has no default constructor
 }
 
 struct D2 : B2 {
diff --git a/gcc/testsuite/g++.dg/cpp2a/concepts-inherit-ctor6.C b/gcc/testsuite/g++.dg/cpp2a/concepts-inherit-ctor6.C
new file mode 100644
index 00000000000..c92d6ac774c
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/concepts-inherit-ctor6.C
@@ -0,0 +1,12 @@
+// PR c++/91930
+// { dg-do compile { target c++2a } }
+
+template <typename T> struct basic_mixin {
+  basic_mixin() requires true;
+};
+
+struct mixin : basic_mixin<int> {
+  using basic_mixin<int>::basic_mixin;
+};
+
+mixin m;

base-commit: a8bf45f436ead5d31db39e9a9578429524d70a2f
-- 
2.18.1