Go patch committed: Skip stubs for ambiguous direct iface methods

[Ian Lance Taylor via Gcc-patches]

This patch to the Go frontend by Михаил Аблакатов (Mikhail Ablakatov)
avoids generating stubs for ambiguous direct interface methods.  The
current implementation checks whether it has to generate a stub method
for a promoted method of an embedded struct field in
Type::build_stub_methods().  If the promoted method is ambiguous it's
simply skipped.  But struct types that can fit in an interface value
(e.g. structs that consist of a single pointer field) get a second
chance in Type::build_direct_iface_stub_methods().

This patch adds the same check used by Type::build_stub_methods() to
Type::build_direct_iface_stub_methods().

Bootstrapped and ran Go testsuite on x86_64-pc-linux-gnu.

This fixes https://go.dev/issue/52870.  The test case is
https://go.dev/cl/412535.

Committed to mainline.

Ian

79d599b057cca42b84303ae25c7ab9f43e9f5eac
diff --git a/gcc/go/gofrontend/MERGE b/gcc/go/gofrontend/MERGE
index aeada9f8d0c..0cda305c648 100644
--- a/gcc/go/gofrontend/MERGE
+++ b/gcc/go/gofrontend/MERGE
@@ -1,4 +1,4 @@
-bbb3a4347714faee620dc205674510a0f20b81ae
+8db6b78110f84e22c409f334aeaefb80a8b39917
 
 The first line of this file holds the git revision number of the last
 merge done from the gofrontend repository.
diff --git a/gcc/go/gofrontend/types.cc b/gcc/go/gofrontend/types.cc
index a8e309041e7..eb3afd94682 100644
--- a/gcc/go/gofrontend/types.cc
+++ b/gcc/go/gofrontend/types.cc
@@ -11891,7 +11891,7 @@ Type::build_direct_iface_stub_methods(Gogo* gogo, const 
Type* type,
         need_stub = true;
       if (!in_heap && !m->is_value_method())
         need_stub = true;
-      if (!need_stub)
+      if (!need_stub || m->is_ambiguous())
         continue;
 
       Type* receiver_type = const_cast<Type*>(type);