Update BUILD.bazel

adding rust_doc_test to ffi example

Author: sebas-zip

examples/ffi/rust_calling_c/example_2/BUILD.bazel

@@ -1,4 +1,4 @@
-load("@rules_rust//rust:defs.bzl", "rust_doc", "rust_library", "rust_test")
+load("@rules_rust//rust:defs.bzl", "rust_doc", "rust_doc_test", "rust_library", "rust_test")
 
 package(default_visibility = ["//rust_calling_c/example_2:__subpackages__"])
 
@@ -24,6 +24,11 @@ rust_doc(
     crate = ":matrix",
 )
 
+rust_doc_test(
+    name = "matrix_doc_test",
+    crate = ":matrix",
+)
+
 ## Do the same as above, but with a dynamic c library.
 
 rust_library(

examples/ffi/rust_calling_c/example_2/src/matrix.rs

@@ -25,6 +25,14 @@ pub struct Matrix {
 }
 
 /// Wrapper around low-level FFI Matrix API.
+///
+/// Here is a simple example of how to use the Matrix struct:
+/// ```
+/// use matrix::Matrix;
+/// let matrix = Matrix::new(2, 4, &[11, 12, 13, 14, 21, 22, 23, 24]);
+/// assert_eq!(2, matrix.rows());
+/// assert_eq!(4, matrix.cols());
+/// ```
 impl Matrix {
     /// Constructs a new Matrix from the given data. Matrix returned contains a copy of the data
     /// provided.