compiler: avoid aliases in receiver types

If a package declares a method on an alias type, the alias would be
used in the export data.  This would then trigger a compiler
assertion on import: we should not be adding methods to aliases.

Fix the problem by ensuring that receiver types do not use alias types.
This seems preferable to consistently avoiding aliases in export data,
as aliases can cross packages.  And it's painful to try to patch this
while writing the export data, as at that point all the types are known.

Test case is https://golang.org/cl/335172.

Fixes golang/go#47131

Reviewed-on: https://go-review.googlesource.com/c/gofrontend/+/335729

4 files changed, 100 insertions, 1 deletions

diff --git a/gcc/go/gofrontend/MERGE b/gcc/go/gofrontend/MERGE
index 4d0f44f..5323e18 100644
--- a/gcc/go/gofrontend/MERGE
+++ b/gcc/go/gofrontend/MERGE
@@ -1,4 +1,4 @@
-adcf10890833026437a94da54934ce50c0018309
+920549b6382a2623538d31001271941f0e9e5a51
 
 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/gogo.cc b/gcc/go/gofrontend/gogo.cc
index 2872d2e..95b76bd 100644
--- a/gcc/go/gofrontend/gogo.cc
+++ b/gcc/go/gofrontend/gogo.cc
@@ -5763,6 +5763,26 @@ Function::check_labels() const
     }
 }
 
+// Set the receiver type.  This is used to remove aliases.
+
+void
+Function::set_receiver_type(Type* rtype)
+{
+  Function_type* oft = this->type_;
+  Typed_identifier* rec = new Typed_identifier(oft->receiver()->name(),
+					       rtype,
+					       oft->receiver()->location());
+  Typed_identifier_list* parameters = NULL;
+  if (oft->parameters() != NULL)
+    parameters = oft->parameters()->copy();
+  Typed_identifier_list* results = NULL;
+  if (oft->results() != NULL)
+    results = oft->results()->copy();
+  Function_type* nft = Type::make_function_type(rec, parameters, results,
+						oft->location());
+  this->type_ = nft;
+}
+
 // Swap one function with another.  This is used when building the
 // thunk we use to call a function which calls recover.  It may not
 // work for any other case.
@@ -7285,6 +7305,26 @@ Function_declaration::set_nointerface()
   this->pragmas_ |= GOPRAGMA_NOINTERFACE;
 }
 
+// Set the receiver type.  This is used to remove aliases.
+
+void
+Function_declaration::set_receiver_type(Type* rtype)
+{
+  Function_type* oft = this->fntype_;
+  Typed_identifier* rec = new Typed_identifier(oft->receiver()->name(),
+					       rtype,
+					       oft->receiver()->location());
+  Typed_identifier_list* parameters = NULL;
+  if (oft->parameters() != NULL)
+    parameters = oft->parameters()->copy();
+  Typed_identifier_list* results = NULL;
+  if (oft->results() != NULL)
+    results = oft->results()->copy();
+  Function_type* nft = Type::make_function_type(rec, parameters, results,
+						oft->location());
+  this->fntype_ = nft;
+}
+
 // Import an inlinable function.  This is used for an inlinable
 // function whose body is recorded in the export data.  Parse the
 // export data into a Block and create a regular function using that
diff --git a/gcc/go/gofrontend/gogo.h b/gcc/go/gofrontend/gogo.h
index f4155a2..c49bc92 100644
--- a/gcc/go/gofrontend/gogo.h
+++ b/gcc/go/gofrontend/gogo.h
@@ -1724,6 +1724,10 @@ class Function
   set_is_referenced_by_inline()
   { this->is_referenced_by_inline_ = true; }
 
+  // Set the receiver type.  This is used to remove aliases.
+  void
+  set_receiver_type(Type* rtype);
+
   // Swap with another function.  Used only for the thunk which calls
   // recover.
   void
@@ -1990,6 +1994,10 @@ class Function_declaration
   set_is_on_inlinable_list()
   { this->is_on_inlinable_list_ = true; }
 
+  // Set the receiver type.  This is used to remove aliases.
+  void
+  set_receiver_type(Type* rtype);
+
   // Import the function body, creating a function.
   void
   import_function_body(Gogo*, Named_object*);
diff --git a/gcc/go/gofrontend/types.cc b/gcc/go/gofrontend/types.cc
index d08cbc9..ab7166b 100644
--- a/gcc/go/gofrontend/types.cc
+++ b/gcc/go/gofrontend/types.cc
@@ -10416,6 +10416,57 @@ Named_type::finalize_methods(Gogo* gogo)
       return;
     }
 
+  // Remove any aliases in the local method receiver types.
+  Bindings* methods = this->local_methods_;
+  if (methods != NULL)
+    {
+      for (Bindings::const_declarations_iterator p =
+	     methods->begin_declarations();
+	   p != methods->end_declarations();
+	   ++p)
+	{
+	  Named_object* no = p->second;
+	  Function_type* fntype;
+	  if (no->is_function())
+	    fntype = no->func_value()->type();
+	  else if (no->is_function_declaration())
+	    fntype = no->func_declaration_value()->type();
+	  else
+	    {
+	      go_assert(saw_errors());
+	      continue;
+	    }
+
+	  Type* rtype = fntype->receiver()->type();
+	  bool is_pointer = false;
+	  Type* pt = rtype->points_to();
+	  if (pt != NULL)
+	    {
+	      rtype = pt;
+	      is_pointer = true;
+	    }
+	  if (rtype->named_type() != this)
+	    {
+	      if (rtype->unalias() != this)
+		{
+		  go_assert(saw_errors());
+		  continue;
+		}
+
+	      rtype = this;
+	      if (is_pointer)
+		rtype = Type::make_pointer_type(rtype);
+
+	      if (no->is_function())
+		no->func_value()->set_receiver_type(rtype);
+	      else if (no->is_function_declaration())
+		no->func_declaration_value()->set_receiver_type(rtype);
+	      else
+		go_unreachable();
+	    }
+	}
+    }
+
   Type::finalize_methods(gogo, this, this->location_, &this->all_methods_);
 }