[vala/staging] vala: Don't allow casting real structs to classes or simple-types

[Rico Tzschichholz <ricotz src gnome org>]

commit af730d4eef2879b487fff6f949a01b69b3b78f5f
Author: Yotam Nachum <me yotam net>
Date:   Sat Nov 6 19:05:13 2021 +0200

    vala: Don't allow casting real structs to classes or simple-types
    
    This led to C compiler errors or obvious runtimes failures.
    
    Fixes https://gitlab.gnome.org/GNOME/vala/issues/1249

 tests/Makefile.am                               |  2 ++
 tests/structs/cast-struct-to-class.test         | 10 ++++++++++
 tests/structs/cast-struct-to-simple-struct.test | 10 ++++++++++
 vala/valacastexpression.vala                    |  9 +++++++++
 4 files changed, 31 insertions(+)
---
diff --git a/tests/Makefile.am b/tests/Makefile.am
index 9a6c4b3f2..ad65913ce 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -345,6 +345,8 @@ TESTS = \
        enums/bug763831.vala \
        enums/bug780050.vala \
        structs/cast-struct-boxed.vala \
+       structs/cast-struct-to-class.test \
+       structs/cast-struct-to-simple-struct.test \
        structs/struct_only.vala \
        structs/struct-base-types.vala \
        structs/struct-boxed-cast.vala \
diff --git a/tests/structs/cast-struct-to-class.test b/tests/structs/cast-struct-to-class.test
new file mode 100644
index 000000000..c87931ea0
--- /dev/null
+++ b/tests/structs/cast-struct-to-class.test
@@ -0,0 +1,10 @@
+Invalid Code
+
+struct Foo {
+       public int i;
+}
+
+void main () {
+       Foo foo = { 42 };
+       Object bar = (Object) foo;
+}
diff --git a/tests/structs/cast-struct-to-simple-struct.test b/tests/structs/cast-struct-to-simple-struct.test
new file mode 100644
index 000000000..3cb6681fc
--- /dev/null
+++ b/tests/structs/cast-struct-to-simple-struct.test
@@ -0,0 +1,10 @@
+Invalid Code
+
+struct Foo {
+       public int i;
+}
+
+void main () {
+       Foo foo = { 42 };
+       int bar = (int) foo;
+}
diff --git a/vala/valacastexpression.vala b/vala/valacastexpression.vala
index 732b99a71..5d0783e41 100644
--- a/vala/valacastexpression.vala
+++ b/vala/valacastexpression.vala
@@ -170,6 +170,15 @@ public class Vala.CastExpression : Expression {
                        return false;
                }
 
+               // Allow casting to array or pointer type
+               if (!(type_reference is ArrayType || type_reference is PointerType)) {
+                       if (!type_reference.is_real_struct_type () && inner.value_type.is_real_struct_type ()
+                           && (context.profile != Profile.GOBJECT || !(is_gvariant (context, 
inner.value_type) || is_gvalue (context, inner.value_type)))) {
+                               error = true;
+                               Report.error (source_reference, "Casting of struct `%s' to `%s' is not 
allowed", inner.value_type.to_qualified_string (), type_reference.to_qualified_string ());
+                       }
+               }
+
                if (type_reference is DelegateType && inner.value_type is MethodType) {
                        if (target_type != null) {
                                inner.value_type.value_owned = target_type.value_owned;