transpile: Add snapshot test for #1506

Author: Rua

c2rust-transpile/tests/snapshots/exprs.c

@@ -38,3 +38,12 @@ void compound_literal(){
     /// https://github.com/immunant/c2rust/issues/1234
     int i = (enum {A, B, C}){1};
 }
+
+void statement_expr() {
+    ({
+        puts("should execute");
+        return;
+    });
+
+    puts("should be unreachable!");
+}

c2rust-transpile/tests/snapshots/snapshots__transpile@exprs.c.snap

@@ -11,7 +11,7 @@ input_file: c2rust-transpile/tests/snapshots/exprs.c
     unused_assignments,
     unused_mut
 )]
-#![feature(raw_ref_op)]
+#![feature(label_break_value, raw_ref_op)]
 extern "C" {
     fn puts(str: *const ::core::ffi::c_char) -> ::core::ffi::c_int;
 }
@@ -56,3 +56,8 @@ pub unsafe extern "C" fn unary_with_side_effect() {
 pub unsafe extern "C" fn compound_literal() {
     let mut i: ::core::ffi::c_int = B as ::core::ffi::c_int;
 }
+#[no_mangle]
+pub unsafe extern "C" fn statement_expr() {
+    puts(b"should execute\0" as *const u8 as *const ::core::ffi::c_char);
+    puts(b"should be unreachable!\0" as *const u8 as *const ::core::ffi::c_char);
+}