Add tests for issue 4573

It's unclear which PR resolved this issue, however the behavior of
adding inline comments to the next line can't be reproduced.

These test cases should serve to prevent a regression.

Author: ytmimi

tests/target/issue_4573.rs

@@ -0,0 +1,97 @@
+// rustmft-version:Two
+// rustmft-use_small_heuristics:Max
+// rustmft-merge_derives:false
+// These are the same rustfmt configuration options that are used
+// in the comiler as of ce39461ca75a and 8eb7c58dbb7b
+// These are commits in https://github.com/rust-lang/rust
+
+#[cfg(not(miri))] // inline comment
+extern crate foo;
+
+#[cfg(not(miri))] // inline comment
+extern crate foo as bar;
+
+#[cfg(not(miri))] // inline comment
+use foo;
+
+#[cfg(not(miri))] // inline comment
+use foo;
+
+#[cfg(not(miri))] // inline comment
+use foo::bar;
+
+#[cfg(not(miri))] // inline comment
+use foo::bar as FooBar;
+
+#[cfg(not(miri))] // inline comment
+static FOO: i32 = 42;
+
+#[cfg(not(miri))] // inline comment
+static FOO: i32 = 42;
+
+#[cfg(not(miri))] // inline comment
+static FOO: &'static str = "bar";
+
+#[cfg(not(miri))] // inline comment
+const FOO: i32 = 42;
+
+#[cfg(not(miri))] // inline comment
+fn foo(bar: usize) {
+    #[cfg(not(miri))] // inline comment
+    println!("hello world!");
+}
+
+#[cfg(not(miri))] // inline comment
+mod foo {}
+
+#[cfg(not(miri))] // inline comment
+mod foo {}
+
+#[cfg(not(miri))] // inline comment
+extern "C" {
+    fn my_c_function(x: i32) -> bool;
+}
+
+#[cfg(not(miri))] // inline comment
+extern "C" {
+    fn my_c_function(x: i32) -> bool;
+}
+
+#[cfg(not(miri))] // inline comment
+pub extern "C" fn callable_from_c(x: i32) -> bool {
+    x % 3 == 0
+}
+
+#[cfg(not(miri))] // inline comment
+type Foo = Bar<u8>;
+
+#[cfg(not(miri))] // inline comment
+enum Foo {
+    Bar,
+    Baz,
+}
+
+#[cfg(not(miri))] // inline comment
+struct Foo<A> {
+    x: A,
+}
+
+#[cfg(not(miri))] // inline comment
+union Foo<A, B> {
+    x: A,
+    y: B,
+}
+
+#[cfg(not(miri))] // inline comment
+trait Foo {}
+
+#[cfg(not(miri))] // inline comment
+trait Foo = Bar + Quux;
+
+#[cfg(not(miri))] // inline comment
+impl Foo {}
+
+#[cfg(not(miri))] // inline comment
+macro_rules! bar {
+    (3) => {};
+}