Add array length to the proc macro buffer

The compiler cannot infer the array length from the type, we should
therefore hand it the information. The proc macro buffer missed that
information.

gcc/rust/ChangeLog:

	* backend/rust-compile.cc (proc_macro_buffer): Update type builder with
	array length information.
	(proc_macro_array): Update type initializer with array length
	information.

Signed-off-by: Pierre-Emmanuel Patry <[email protected]>

gcc/rust/backend/rust-compile.cc

@@ -207,8 +207,14 @@ proc_macro ()
 tree
 proc_macro_buffer (tree proc_macro_type, size_t total_macro)
 {
-  // FIXME: Add the array length, build a structure containing an array
-  return build_array_type_nelts (proc_macro_type, total_macro);
+  auto length_field = Backend::typed_identifier ("length", unsigned_type_node,
+						 BUILTINS_LOCATION);
+
+  auto array_type = build_array_type_nelts (proc_macro_type, total_macro);
+  auto macros_field
+    = Backend::typed_identifier ("macros", array_type, BUILTINS_LOCATION);
+
+  return Backend::struct_type ({length_field, macros_field});
 }
 
 // The entrypoint of a proc macro crate is a reference to the proc macro buffer
@@ -374,8 +380,15 @@ proc_macro_array (Context *ctx, tree proc_macro_buffer_type,
       index++;
     }
 
-  return Backend::array_constructor_expression (proc_macro_buffer_type, indexes,
-						ctors, BUILTINS_LOCATION);
+  auto length = build_int_cst (unsigned_type_node, ctors.size ());
+  auto array = Backend::array_constructor_expression (
+    build_array_type_nelts (proc_macro_type, ctors.size ()), indexes, ctors,
+    BUILTINS_LOCATION);
+  return Backend::constructor_expression (proc_macro_buffer_type,
+					  false /* invariant */,
+					  {length, array},
+					  -1 /* Structure: No index */,
+					  BUILTINS_LOCATION);
 }
 } // namespace init