[vala/0.52] codegen: Don't add errornous cast for unknown type_symbol

[Rico Tzschichholz <ricotz src gnome org>]

commit 4759fece4e422601f4084df2ce9fd1c1700698e9
Author: Rico Tzschichholz <ricotz ubuntu com>
Date:   Fri May 7 13:46:28 2021 +0200

    codegen: Don't add errornous cast for unknown type_symbol
    
    This causes invalid C code for reference transfer of GenericType.
    
    Regression of 7ae2f115a702439bd94bf09867b38019f39d010f
    
    Fixes https://gitlab.gnome.org/GNOME/vala/issues/1180

 codegen/valaccodememberaccessmodule.vala |  2 +-
 tests/generics/reference-transfer.vala   | 14 ++++++++++++--
 2 files changed, 13 insertions(+), 3 deletions(-)
---
diff --git a/codegen/valaccodememberaccessmodule.vala b/codegen/valaccodememberaccessmodule.vala
index ea8e3a3d8..d5d089010 100644
--- a/codegen/valaccodememberaccessmodule.vala
+++ b/codegen/valaccodememberaccessmodule.vala
@@ -431,7 +431,7 @@ public abstract class Vala.CCodeMemberAccessModule : CCodeControlFlowModule {
                // Add cast for narrowed type access of variables if needed
                if (expr.symbol_reference is Variable) {
                        unowned GLibValue cvalue = (GLibValue) expr.target_value;
-                       if (cvalue.value_type.type_symbol != expr.value_type.type_symbol) {
+                       if (cvalue.value_type.type_symbol != null && cvalue.value_type.type_symbol != 
expr.value_type.type_symbol) {
                                cvalue.cvalue = new CCodeCastExpression (cvalue.cvalue, get_ccode_name 
(expr.value_type));
                        }
                }
diff --git a/tests/generics/reference-transfer.vala b/tests/generics/reference-transfer.vala
index da2c1e305..5dc7a666f 100644
--- a/tests/generics/reference-transfer.vala
+++ b/tests/generics/reference-transfer.vala
@@ -19,6 +19,16 @@ void foo<G> (owned G g) {
 }
 
 void main () {
-       foo<string> ("foo");
-       bar<string> (new Bar<string> ("bar"));
+       {
+               foo<string> ("foo");
+       }
+       {
+               bar<string> (new Bar<string> ("bar"));
+       }
+       {
+               var bar = new Bar<string> ("bar");
+               var t = (owned) bar.g;
+               assert (bar.g == null);
+               assert (t == "bar");
+       }
 }