[interp] Fix enum constrained calls on netcore (#18659)

We were failing to dereference a managed pointer to the enum, due to incorrect checks, when doing a constrained call.

Fixes https://github.com/mono/mono/issues/18530

Co-authored-by: Vlad Brezae <brezaevlad@gmail.com>

1 files changed, 10 insertions, 3 deletions

diff --git a/mono/mini/interp/transform.c b/mono/mini/interp/transform.c
index ad7154ef66b..be002146491 100644
--- a/mono/mini/interp/transform.c
+++ b/mono/mini/interp/transform.c
@@ -2193,8 +2193,14 @@ interp_transform_call (TransformData *td, MonoMethod *method, MonoMethod *target
 			interp_add_ins (td, MINT_LDIND_I);
 			td->last_ins->data [0] = csignature->param_count;
 		} else if (target_method->klass == mono_defaults.object_class || target_method->klass == m_class_get_parent (mono_defaults.enum_class) || target_method->klass == mono_defaults.enum_class) {
-			if (target_method->klass == mono_defaults.enum_class && (td->sp - csignature->param_count - 1)->type == STACK_TYPE_MP) {
-				/* managed pointer on the stack, we need to deref that puppy */
+			/*
+			 * Constrained expects a managed pointer that normally needs dereferencing.
+			 * For value types that have their storage on the vtstack, a managed pointer
+			 * to it is identical to the internal pointer that is passed on the stack
+			 * when using the value type, not needing any dereferencing.
+			 */
+			g_assert ((td->sp - csignature->param_count - 1)->type == STACK_TYPE_MP);
+			if (mint_type (m_class_get_byval_arg (constrained_class)) != MINT_TYPE_VT) {
 				/* Always load the entire stackval, to handle also the case where the enum has long storage */
 				interp_add_ins (td, MINT_LDIND_I8);
 				td->last_ins->data [0] = csignature->param_count;
@@ -2209,7 +2215,8 @@ interp_transform_call (TransformData *td, MonoMethod *method, MonoMethod *target
 				 * but that type doesn't override the method we're
 				 * calling, so we need to box `this'.
 				 */
-				if (target_method->klass == mono_defaults.enum_class && (td->sp - csignature->param_count - 1)->type == STACK_TYPE_MP) {
+				g_assert ((td->sp - csignature->param_count - 1)->type == STACK_TYPE_MP);
+				if (mint_type (m_class_get_byval_arg (constrained_class)) != MINT_TYPE_VT) {
 					/* managed pointer on the stack, we need to deref that puppy */
 					/* Always load the entire stackval, to handle also the case where the enum has long storage */
 					interp_add_ins (td, MINT_LDIND_I8);