[PATCH] c++: spurious ADDR_EXPR after overload set pruning [PR107461]

[Patrick Palka <ppalka@redhat.com>]

Here the ahead-of-time overload set pruning in finish_call_expr is
unintentionally returning a CALL_EXPR whose pruned callee is wrapped in
an ADDR_EXPR, despite the original callee not being wrapped in an
ADDR_EXPR.  This ends up causing a bogus declaration matching error in
the below testcase because the call to min in #1 is expressed as a
CALL_EXPR to ADDR_EXPR to FUNCTION_DECL, whereas the level-lowered call
to min in #2 is expressed instead as a CALL_EXPR to FUNCTION_DECL.

This patch fixes this by stripping this ADDR_EXPR appropriately.
Thus the first call to min now gets expresssed as a CALL_EXPR to
FUNCTION_DECL, matching the form it had before r12-6075-g2decd2cabe5a4f.

Bootstrapped and regtested on x86_64-pc-linu-xgnu, does this look OK
for trunk and 12?

	PR c++/107461

gcc/cp/ChangeLog:

	* semantics.cc (finish_call_expr): Strip ADDR_EXPR from
	the selected callee during overload set pruning.

gcc/testsuite/ChangeLog:

	* g++.dg/template/friend75.C: New test.
---
 gcc/cp/semantics.cc                      | 15 +++++++++-----
 gcc/testsuite/g++.dg/template/friend75.C | 26 ++++++++++++++++++++++++
 2 files changed, 36 insertions(+), 5 deletions(-)
 create mode 100644 gcc/testsuite/g++.dg/template/friend75.C

diff --git a/gcc/cp/semantics.cc b/gcc/cp/semantics.cc
index b3afea85196..fe9262a257f 100644
--- a/gcc/cp/semantics.cc
+++ b/gcc/cp/semantics.cc
@@ -2957,13 +2957,18 @@ finish_call_expr (tree fn, vec<tree, va_gc> **args, bool disallow_virtual,
       if (TREE_CODE (result) == CALL_EXPR
 	  && really_overloaded_fn (orig_fn))
 	{
-	  orig_fn = CALL_EXPR_FN (result);
-	  if (TREE_CODE (orig_fn) == COMPONENT_REF)
+	  tree sel_fn = CALL_EXPR_FN (result);
+	  if (TREE_CODE (sel_fn) == COMPONENT_REF)
 	    {
 	      /* The non-dependent result of build_new_method_call.  */
-	      orig_fn = TREE_OPERAND (orig_fn, 1);
-	      gcc_assert (BASELINK_P (orig_fn));
-	    }
+	      sel_fn = TREE_OPERAND (sel_fn, 1);
+	      gcc_assert (BASELINK_P (sel_fn));
+	    }
+	  else if (TREE_CODE (sel_fn) == ADDR_EXPR)
+	    /* Undo the ADDR_EXPR callee wrapping performed by build_over_call
+	       since the original callee didn't have it.  */
+	    sel_fn = TREE_OPERAND (sel_fn, 0);
+	  orig_fn = sel_fn;
 	}
 
       result = build_call_vec (TREE_TYPE (result), orig_fn, orig_args);
diff --git a/gcc/testsuite/g++.dg/template/friend75.C b/gcc/testsuite/g++.dg/template/friend75.C
new file mode 100644
index 00000000000..800d3043c8a
--- /dev/null
+++ b/gcc/testsuite/g++.dg/template/friend75.C
@@ -0,0 +1,26 @@
+// PR c++/107461
+// { dg-do compile { target c++11 } }
+
+template<class T>
+constexpr T min(T t0, T t1) {
+  return t0 < t1 ? t0 : t1;
+}
+
+template<int MAX>
+struct Matrix;
+
+template<int MAXOP, int other_MAXOP>
+Matrix<min(MAXOP, other_MAXOP)>
+operator+(Matrix<MAXOP> const& lhs, Matrix<other_MAXOP> const& rhs); // #1
+
+template<int MAX>
+struct Matrix {
+  template<int MAXOP, int other_MAXOP>
+  friend Matrix<min(MAXOP, other_MAXOP)>
+  operator+(Matrix<MAXOP> const& lhs, Matrix<other_MAXOP> const& rhs); // #2
+};
+
+void f() {
+  Matrix<1> a;
+  a+a;
+}
-- 
2.39.1.388.g2fc9e9ca3c