make PhantomData #[structural_match].

Author: Centril

src/libcore/lib.rs

@@ -129,6 +129,7 @@
 #![feature(const_transmute)]
 #![feature(reverse_bits)]
 #![feature(non_exhaustive)]
+#![feature(structural_match)]
 
 #[prelude_import]
 #[allow(unused)]

src/libcore/marker.rs

@@ -578,6 +578,7 @@ macro_rules! impls{
 ///
 /// [drop check]: ../../nomicon/dropck.html
 #[lang = "phantom_data"]
+#[structural_match]
 #[stable(feature = "rust1", since = "1.0.0")]
 pub struct PhantomData<T:?Sized>;
 

src/test/ui/rfc1445/phantom-data-is-structurally-matchable.rs

@@ -0,0 +1,53 @@
+// run-pass
+
+// This file checks that `PhantomData` is considered structurally matchable.
+
+use std::marker::PhantomData;
+
+fn main() {
+ let mut count = 0;
+
+ // A type which is not structurally matchable:
+ struct NotSM;
+
+ // And one that is:
+ #[derive(PartialEq, Eq)]
+ struct SM;
+
+ // Check that SM is #[structural_match]:
+ const CSM: SM = SM;
+ match SM {
+ CSM => count += 1,
+ };
+
+ // Check that PhantomData<T> is #[structural_match] even if T is not.
+ const CPD1: PhantomData<NotSM> = PhantomData;
+ match PhantomData {
+ CPD1 => count += 1,
+ };
+
+ // Check that PhantomData<T> is #[structural_match] when T is.
+ const CPD2: PhantomData<SM> = PhantomData;
+ match PhantomData {
+ CPD2 => count += 1,
+ };
+
+ // Check that a type which has a PhantomData is `#[structural_match]`.
+ #[derive(PartialEq, Eq, Default)]
+ struct Foo {
+ alpha: PhantomData<NotSM>,
+ beta: PhantomData<SM>,
+ }
+
+ const CFOO: Foo = Foo {
+ alpha: PhantomData,
+ beta: PhantomData,
+ };
+
+ match Foo::default() {
+ CFOO => count += 1,
+ };
+
+ // Final count must be 4 now if all
+ assert_eq!(count, 4);
+}