c++: ICE with deferred noexcept when deducing targs [PR82099]

In this test we ICE in type_throw_all_p because it got a deferred
noexcept which it shouldn't.  Here's the story:

In noexcept61.C, we call bar, so we perform overload resolution.  When
adding the (only) candidate, we need to deduce template arguments, so
call fn_type_unification as usually.  That deduces U to

  void (*) (int &, int &)

which is correct, but its noexcept-spec is deferred_noexcept.  Then
we call add_function_candidate (bar), wherein we try to create an
implicit conversion sequence for every argument.  Since baz<int> is
of unknown type, we instantiate_type it; it is a TEMPLATE_ID_EXPR
so that calls resolve_address_of_overloaded_function.  But we crash
there, because target_type contains the deferred_noexcept.

So we need to maybe_instantiate_noexcept before we can compare types.
resolve_overloaded_unification seemed like the appropriate spot, now
fn_type_unification produces the function type with its noexcept-spec
instantiated.  This shouldn't go against CWG 1330 because here we
really need to instantiate the noexcept-spec.

This also fixes class-deduction76.C, a dg-ice test I recently added,
therefore this fix also fixes c++/90799, yay.

gcc/cp/ChangeLog:

	PR c++/82099
	* pt.c (resolve_overloaded_unification): Call
	maybe_instantiate_noexcept after instantiating the function
	decl.

gcc/testsuite/ChangeLog:

	PR c++/82099
	* g++.dg/cpp1z/class-deduction76.C: Remove dg-ice.
	* g++.dg/cpp0x/noexcept61.C: New test.

3 files changed, 20 insertions, 1 deletions

diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index 062ef85..0d061ad 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -22373,6 +22373,9 @@ resolve_overloaded_unification (tree tparms,
 		  --function_depth;
 		}
 
+	      if (flag_noexcept_type)
+		maybe_instantiate_noexcept (fn, tf_none);
+
 	      elem = TREE_TYPE (fn);
 	      if (try_one_overload (tparms, targs, tempargs, parm,
 				    elem, strict, sub_strict, addr_p, explain_p)
diff --git a/gcc/testsuite/g++.dg/cpp0x/noexcept61.C b/gcc/testsuite/g++.dg/cpp0x/noexcept61.C
new file mode 100644
index 0000000..653cd7e
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/noexcept61.C
@@ -0,0 +1,17 @@
+// PR c++/82099
+// { dg-do compile { target c++11 } }
+
+template <typename T, typename U>
+void bar (T &x, T &y, U u)
+{
+  u (x, y);
+}
+
+template <typename T>
+void baz (T &x, T &y) noexcept (noexcept (x == y));
+
+void
+foo (int x, int y)
+{
+  bar (x, y, baz<int>);
+}
diff --git a/gcc/testsuite/g++.dg/cpp1z/class-deduction76.C b/gcc/testsuite/g++.dg/cpp1z/class-deduction76.C
index 23bb6e8..a131a38 100644
--- a/gcc/testsuite/g++.dg/cpp1z/class-deduction76.C
+++ b/gcc/testsuite/g++.dg/cpp1z/class-deduction76.C
@@ -1,6 +1,5 @@
 // PR c++/90799
 // { dg-do compile { target c++17 } }
-// { dg-ice "unify" }
 
 template<class T>
 void foo() noexcept(T::value);