Python API: do not dec_ref C array values when coming from struct fields

TN: T423-042

testsuite/tests/python_api/array-struct-array/expected_concrete_syntax.lkt

@@ -0,0 +1,18 @@
+import lexer_example
+grammar foo_grammar {
+    @main_rule main_rule <- Example("example")
+
+}
+
+@root_node class FooNode {
+}
+
+class Example : FooNode {
+
+    @export fun example_holders (): Array[ExampleHolder] =
+    [ExampleHolder(examples=[self])]
+}
+
+struct ExampleHolder {
+    examples : Array[Example]
+}

testsuite/tests/python_api/array-struct-array/main.py

@@ -0,0 +1,8 @@
+from __future__ import absolute_import, division, print_function
+
+import libfoolang as lfl
+
+
+ctx = lfl.AnalysisContext()
+u = ctx.get_from_buffer("test", "example")
+print(u.root.p_example_holders)

testsuite/tests/python_api/array-struct-array/test.out

@@ -0,0 +1,2 @@
+[<ExampleHolder examples=[<Example test:1:1-1:8>]>]
+Done

testsuite/tests/python_api/array-struct-array/test.py

@@ -0,0 +1,24 @@
+from __future__ import absolute_import, division, print_function
+
+from langkit.dsl import ASTNode, Struct, T, UserField
+from langkit.expressions import Entity, langkit_property
+
+from utils import build_and_run
+
+
+class FooNode(ASTNode):
+    pass
+
+
+class ExampleHolder(Struct):
+    examples = UserField(type=T.Example.entity.array)
+
+
+class Example(FooNode):
+    @langkit_property(return_type=ExampleHolder.array, public=True)
+    def example_holders():
+        return ExampleHolder.new(examples=Entity.singleton).singleton
+
+
+build_and_run(lkt_file='expected_concrete_syntax.lkt', py_script='main.py')
+print('Done')

testsuite/tests/python_api/array-struct-array/test.yaml

@@ -0,0 +1 @@
+driver: python