Add regression ui test for rust-lang#140162 and for rust-lang#139651

Author: GuillaumeGomez

tests/rustdoc-ui/doctest/test-main-alongside-exprs.rs

@@ -0,0 +1,22 @@
+// This test ensures that if there is an expression alongside a `main`
+// function, it will not consider the entire code to be part of the `main`
+// function and will generate its own function to wrap everything.
+//
+// This is a regression test for:
+// * <https://github.com/rust-lang/rust/issues/140162>
+// * <https://github.com/rust-lang/rust/issues/139651>
+//@ compile-flags:--test
+//@ normalize-stdout: "tests/rustdoc-ui/doctest" -> "$$DIR"
+//@ normalize-stdout: "finished in \d+\.\d+s" -> "finished in $$TIME"
+//@ check-pass
+
+#![crate_name = "foo"]
+
+//! ```
+//! # if cfg!(miri) { return; }
+//! use std::ops::Deref;
+//!
+//! fn main() {
+//!     println!("Hi!");
+//! }
+//! ```

tests/rustdoc-ui/doctest/test-main-alongside-exprs.stdout

@@ -0,0 +1,6 @@
+
+running 1 test
+test $DIR/test-main-alongside-exprs.rs - (line 15) ... ok
+
+test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in $TIME
+