Go patch committed: Don't record dependencies of redefinitions

[Ian Lance Taylor]

This patch by Chris Manghane fixes a Go frontend crash on invalid code
that redefines a variable.  This fixes https://golang.org/issue/11543
.  Bootstrapped and ran Go testsuite on x86_64-unknown-linux-gnu.
Committed to mainline.

Ian

Index: gcc/go/gofrontend/MERGE
===================================================================
--- gcc/go/gofrontend/MERGE     (revision 227245)
+++ gcc/go/gofrontend/MERGE     (working copy)
@@ -1,4 +1,4 @@
-5ee78e7d52a4cad0b23f5bc62e5b452489243c70
+a1d2cac484f46068b5a6ddf3e041d425a3d25e0c
 
 The first line of this file holds the git revision number of the last
 merge done from the gofrontend repository.
Index: gcc/go/gofrontend/gogo.cc
===================================================================
--- gcc/go/gofrontend/gogo.cc   (revision 226899)
+++ gcc/go/gofrontend/gogo.cc   (working copy)
@@ -6753,7 +6753,8 @@ Unknown_name::set_real_named_object(Name
 Named_object::Named_object(const std::string& name,
                           const Package* package,
                           Classification classification)
-  : name_(name), package_(package), classification_(classification)
+  : name_(name), package_(package), classification_(classification),
+    is_redefinition_(false)
 {
   if (Gogo::is_sink_name(name))
     go_assert(classification == NAMED_OBJECT_SINK);
@@ -7439,6 +7440,8 @@ Bindings::new_definition(Named_object* o
   else
     error_at(new_object->location(), "redefinition of %qs: %s", n.c_str(),
             reason.c_str());
+  old_object->set_is_redefinition();
+  new_object->set_is_redefinition();
 
   inform(old_object->location(), "previous definition of %qs was here",
         n.c_str());
Index: gcc/go/gofrontend/gogo.h
===================================================================
--- gcc/go/gofrontend/gogo.h    (revision 226846)
+++ gcc/go/gofrontend/gogo.h    (working copy)
@@ -2389,6 +2389,17 @@ class Named_object
   void
   export_named_object(Export*) const;
 
+  // Mark this named object as an invalid redefinition of another object.
+  void
+  set_is_redefinition()
+  { this->is_redefinition_ = true; }
+
+  // Return whether or not this object is a invalid redefinition of another
+  // object.
+  bool
+  is_redefinition() const
+  { return this->is_redefinition_; }
+
  private:
   Named_object(const std::string&, const Package*, Classification);
 
@@ -2412,6 +2423,8 @@ class Named_object
     Function_declaration* func_declaration_value;
     Package* package_value;
   } u_;
+  // True if this object is an invalid redefinition of another object.
+  bool is_redefinition_;
 };
 
 // A binding contour.  This binds names to objects.
Index: gcc/go/gofrontend/parse.cc
===================================================================
--- gcc/go/gofrontend/parse.cc  (revision 227160)
+++ gcc/go/gofrontend/parse.cc  (working copy)
@@ -1741,6 +1741,14 @@ Parse::init_vars_from_call(const Typed_i
            first_var = no;
          else
            {
+              // If the current object is a redefinition of another object, we
+              // might have already recorded the dependency relationship 
between
+              // it and the first variable.  Either way, an error will be
+              // reported for the redefinition and we don't need to properly
+              // record dependency information for an invalid program.
+              if (no->is_redefinition())
+                continue;
+
              // The subsequent vars have an implicit dependency on
              // the first one, so that everything gets initialized in
              // the right order and so that we detect cycles