compiler: look through aliases for type compatibility

    Aliases are supposed to be identical to the type being aliased, so
    questions about type compatibility need to always ignore aliases,
    except for error messages involving the type name.

    The test case for this is https://golang.org/cl/94995.

    Fixes golang/go#23912

    Reviewed-on: https://go-review.googlesource.com/94996

From-SVN: r257845

diff --git a/gcc/go/gofrontend/MERGE b/gcc/go/gofrontend/MERGE
index cb7dffd7905c34d604856ace43f1139826536fec..61bed68afca6c6a1d14bedbf26a60297cdaafd94 100644 (file)
--- a/gcc/go/gofrontend/MERGE
+++ b/gcc/go/gofrontend/MERGE
@@ -1,4 +1,4 @@
-cef3934fbc63f5e121abb8f88d3799961ac95b59
+459a8a94e04a19bde7173ef7cf2db369c2e62e2d
 
 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 40eccfcadcaf8b70a7b04abf55d7adf1a6c4faf9..11924e6e224f027ecee12be8372cd6c23ae4345a 100644 (file)
--- a/gcc/go/gofrontend/types.cc
+++ b/gcc/go/gofrontend/types.cc
@@ -597,10 +597,10 @@ Type::are_compatible_for_comparison(bool is_equality_op, const Type *t1,
          return false;
        }
 
-      if (t1->named_type() != NULL)
-       return t1->named_type()->named_type_is_comparable(reason);
-      else if (t2->named_type() != NULL)
-       return t2->named_type()->named_type_is_comparable(reason);
+      if (t1->unalias()->named_type() != NULL)
+       return t1->unalias()->named_type()->named_type_is_comparable(reason);
+      else if (t2->unalias()->named_type() != NULL)
+       return t2->unalias()->named_type()->named_type_is_comparable(reason);
       else if (t1->struct_type() != NULL)
        {
          if (t1->struct_type()->is_struct_incomparable())
@@ -678,6 +678,12 @@ Type::are_assignable(const Type* lhs, const Type* rhs, std::string* reason)
   if (Type::are_identical(lhs, rhs, true, reason))
     return true;
 
+  // Ignore aliases, except for error messages.
+  const Type* lhs_orig = lhs;
+  const Type* rhs_orig = rhs;
+  lhs = lhs->unalias();
+  rhs = rhs->unalias();
+
   // The types are assignable if they have identical underlying types
   // and either LHS or RHS is not a named type.
   if (((lhs->named_type() != NULL && rhs->named_type() == NULL)
@@ -740,15 +746,16 @@ Type::are_assignable(const Type* lhs, const Type* rhs, std::string* reason)
     {
       if (rhs->interface_type() != NULL)
        reason->assign(_("need explicit conversion"));
-      else if (lhs->named_type() != NULL && rhs->named_type() != NULL)
+      else if (lhs_orig->named_type() != NULL
+              && rhs_orig->named_type() != NULL)
        {
-         size_t len = (lhs->named_type()->name().length()
-                       + rhs->named_type()->name().length()
+         size_t len = (lhs_orig->named_type()->name().length()
+                       + rhs_orig->named_type()->name().length()
                        + 100);
          char* buf = new char[len];
          snprintf(buf, len, _("cannot use type %s as type %s"),
-                  rhs->named_type()->message_name().c_str(),
-                  lhs->named_type()->message_name().c_str());
+                  rhs_orig->named_type()->message_name().c_str(),
+                  lhs_orig->named_type()->message_name().c_str());
          reason->assign(buf);
          delete[] buf;
        }
@@ -768,6 +775,10 @@ Type::are_convertible(const Type* lhs, const Type* rhs, std::string* reason)
   if (Type::are_assignable(lhs, rhs, reason))
     return true;
 
+  // Ignore aliases.
+  lhs = lhs->unalias();
+  rhs = rhs->unalias();
+
   // A pointer to a regular type may not be converted to a pointer to
   // a type that may not live in the heap, except when converting from
   // unsafe.Pointer.