Go patch committed: Don't use sink as method expression thunk parameter

[Ian Lance Taylor via Gcc-patches]

This Go frontend patch avoids using a sink name (_) as a parameter
name when creating a method expression thunk.  The patch also fixes a
couple of cases where the error led to a later compiler crash.  The
test case is https://go.dev/cl/414336.  This fixes
https://go.dev/issue/52871.  Bootstrapped and ran Go testsuite on
x86_64-pc-linux-gnu.  Committed to mainline.

Ian

5f6b6494035fb984d745efa28d334f7893e7272b
diff --git a/gcc/go/gofrontend/MERGE b/gcc/go/gofrontend/MERGE
index f84347ea575..16d274ce99d 100644
--- a/gcc/go/gofrontend/MERGE
+++ b/gcc/go/gofrontend/MERGE
@@ -1,4 +1,4 @@
-6edae0ef6521569e8f949aaaafa9dc1139825051
+927528cdc112fc51e0d07ee79e7a1254b586eabe
 
 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/expressions.cc b/gcc/go/gofrontend/expressions.cc
index 135dae02262..f59f61d19ad 100644
--- a/gcc/go/gofrontend/expressions.cc
+++ b/gcc/go/gofrontend/expressions.cc
@@ -1426,7 +1426,12 @@ Sink_expression::do_get_backend(Translate_context* 
context)
   Gogo* gogo = context->gogo();
   if (this->bvar_ == NULL)
     {
-      go_assert(this->type_ != NULL && !this->type_->is_sink_type());
+      if (this->type_ == NULL || this->type_->is_sink_type())
+       {
+         go_assert(saw_errors());
+         return gogo->backend()->error_expression();
+       }
+
       Named_object* fn = context->function();
       go_assert(fn != NULL);
       Bfunction* fn_ctx = fn->func_value()->get_or_make_decl(gogo, fn);
@@ -15235,7 +15240,7 @@ Selector_expression::lower_method_expression(Gogo* gogo)
           p != method_parameters->end();
           ++p, ++i)
        {
-         if (!p->name().empty())
+         if (!p->name().empty() && !Gogo::is_sink_name(p->name()))
            parameters->push_back(*p);
          else
            {
diff --git a/gcc/go/gofrontend/types.cc b/gcc/go/gofrontend/types.cc
index 39aea769eb2..e82be6840aa 100644
--- a/gcc/go/gofrontend/types.cc
+++ b/gcc/go/gofrontend/types.cc
@@ -4654,8 +4654,11 @@ class Sink_type : public Type
   { return false; }
 
   Btype*
-  do_get_backend(Gogo*)
-  { go_unreachable(); }
+  do_get_backend(Gogo* gogo)
+  {
+    go_assert(saw_errors());
+    return gogo->backend()->error_type();
+  }
 
   Expression*
   do_type_descriptor(Gogo*, Named_type*)