Fix evaluation order in struct field expressions

Fixes #4445

gcc/rust/ChangeLog:

	* backend/rust-compile-expr.cc (CompileExpr::visit): Get struct field
	type with field name
	* typecheck/rust-hir-type-check-struct.cc (TypeCheckStructExpr::resolve): Cancel
	reordering of struct field exprs

Signed-off-by: Mohamed El Shorbagy <mohrizq895@gmail.com>

Author: elshorbagyx

gcc/rust/backend/rust-compile-expr.cc

@@ -595,17 +595,39 @@ CompileExpr::visit (HIR::StructExprStructFields &struct_expr)
     }
   else
     {
-      // this assumes all fields are in order from type resolution and if a
-      // base struct was specified those fields are filed via accessors
       for (size_t i = 0; i < struct_expr.get_fields ().size (); i++)
 	{
+	  std::string field_name;
+	  auto &argument = struct_expr.get_fields ().at (i);
+	  switch (argument->get_kind ())
+	    {
+	    case HIR::StructExprField::StructExprFieldKind::IDENTIFIER:
+	      field_name
+		= (static_cast<HIR::StructExprFieldIdentifier &> (*argument))
+		    .get_field_name ();
+	      break;
+
+	    case HIR::StructExprField::StructExprFieldKind::IDENTIFIER_VALUE:
+	      field_name = (static_cast<HIR::StructExprFieldIdentifierValue &> (
+			      *argument))
+			     .get_field_name ();
+	      break;
+
+	    case HIR::StructExprField::StructExprFieldKind::INDEX_VALUE:
+	      field_name = std::to_string (
+		(static_cast<HIR::StructExprFieldIndexValue &> (*argument))
+		  .get_tuple_index ());
+	      break;
+	    }
+
 	  // assignments are coercion sites so lets convert the rvalue if
 	  // necessary
-	  auto respective_field = variant->get_field_at_index (i);
+	  TyTy::StructFieldType *respective_field = nullptr;
+	  auto _ok
+	    = variant->lookup_field (field_name, &respective_field, nullptr);
+	  rust_assert (_ok);
 	  auto expected = respective_field->get_field_type ();
 
-	  // process arguments
-	  auto &argument = struct_expr.get_fields ().at (i);
 	  auto lvalue_locus
 	    = ctx->get_mappings ().lookup_location (expected->get_ty_ref ());
 	  auto rvalue_locus = argument->get_locus ();

gcc/rust/typecheck/rust-hir-type-check-struct.cc

@@ -235,23 +235,6 @@ TypeCheckStructExpr::resolve (HIR::StructExprStructFields &struct_expr)
 	}
       rust_assert (struct_expr.union_index != -1);
     }
-  else
-    {
-      // everything is ok, now we need to ensure all field values are ordered
-      // correctly. The GIMPLE backend uses a simple algorithm that assumes each
-      // assigned field in the constructor is in the same order as the field in
-      // the type
-      for (auto &field : struct_expr.get_fields ())
-	field.release ();
-
-      std::vector<std::unique_ptr<HIR::StructExprField> > ordered_fields;
-      ordered_fields.reserve (adtFieldIndexToField.size ());
-
-      for (size_t i = 0; i < adtFieldIndexToField.size (); i++)
-	ordered_fields.emplace_back (adtFieldIndexToField[i]);
-
-      struct_expr.set_fields_as_owner (std::move (ordered_fields));
-    }
 
   resolved = struct_def;
 }