test: add nonstandard_style lint test

Adds a test to make sure that no excess warnings are emitted when
dealing with non-standard field names in `init!`.

Signed-off-by: Mirko Adzic <adzicmirko97@gmail.com>

Author: Mirko-A

tests/nonstandard_style.rs

@@ -0,0 +1,31 @@
+//! Tests that no extra warnings are emitted for non-standard style fields when using `init!`.
+//!
+//! See: https://github.com/Rust-for-Linux/pin-init/issues/125
+
+// Should be implied by crate lint settings, but just to be sure:
+#![deny(nonstandard_style)]
+#![allow(dead_code)]
+#![cfg_attr(USE_RUSTC_FEATURES, feature(lint_reasons))]
+#![cfg_attr(USE_RUSTC_FEATURES, feature(raw_ref_op))]
+
+use pin_init::*;
+
+#[allow(nonstandard_style)]
+struct Foo {
+    NON_STANDARD_A: usize,
+    nonStandardB: Bar,
+}
+
+#[allow(non_snake_case)]
+struct Bar {
+    Non_Standard_C: usize,
+}
+
+impl Foo {
+    fn new() -> impl Init<Self> {
+        init!(Self {
+            NON_STANDARD_A: 42,
+            nonStandardB <- init!(Bar { Non_Standard_C: 42 }),
+        })
+    }
+}