implement type-changing-struct-update

put the test dir in test/ui/rfcs

src/test/ui/rfcs/rfc-2528-type-changing-struct-update/feature-gate.rs

@@ -1,3 +1,5 @@
+// gate-test-type_changing_struct_update
+
 #[derive(Debug)]
 struct Machine<S> {
     state: S,

src/test/ui/rfcs/rfc-2528-type-changing-struct-update/feature-gate.stderr

@@ -1,5 +1,5 @@
 error[E0308]: mismatched types
-  --> $DIR/feature-gate-type_changing_struct_update.rs:20:11
+  --> $DIR/feature-gate.rs:22:11
    |
 LL |         ..m1
    |           ^^ expected struct `State2`, found struct `State1`

src/test/ui/rfcs/rfc-2528-type-changing-struct-update/lifetime-update.rs

@@ -0,0 +1,43 @@
+#![feature(type_changing_struct_update)]
+#![allow(incomplete_features)]
+
+#[derive(Clone)]
+struct Machine<'a, S> {
+    state: S,
+    lt_str: &'a str,
+    common_field: i32,
+}
+
+#[derive(Clone)]
+struct State1;
+#[derive(Clone)]
+struct State2;
+
+fn update_to_state2() {
+    let s = String::from("hello");
+    let m1: Machine<State1> = Machine {
+        state: State1,
+        lt_str: &s,
+                //~^ ERROR `s` does not live long enough [E0597]
+                // FIXME: The error here actually comes from line 34. The
+                // span of the error message should be corrected to line 34
+        common_field: 2,
+    };
+    // update lifetime
+    let m3: Machine<'static, State1> = Machine {
+        lt_str: "hello, too",
+        ..m1.clone()
+    };
+    // update lifetime and type
+    let m4: Machine<'static, State2> = Machine {
+        state: State2,
+        lt_str: "hello, again",
+        ..m1.clone()
+    };
+    // updating to `static should fail.
+    let m2: Machine<'static, State1> = Machine {
+        ..m1
+    };
+}
+
+fn main() {}

src/test/ui/rfcs/rfc-2528-type-changing-struct-update/lifetime-update.stderr

@@ -0,0 +1,15 @@
+error[E0597]: `s` does not live long enough
+  --> $DIR/lifetime-update.rs:20:17
+   |
+LL |         lt_str: &s,
+   |                 ^^ borrowed value does not live long enough
+...
+LL |     let m2: Machine<'static, State1> = Machine {
+   |             ------------------------ type annotation requires that `s` is borrowed for `'static`
+...
+LL | }
+   | - `s` dropped here while still borrowed
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0597`.

src/test/ui/rfcs/rfc-2528-type-changing-struct-update/type-generic-update.rs

@@ -0,0 +1,57 @@
+#![feature(type_changing_struct_update)]
+#![allow(incomplete_features)]
+
+struct Machine<'a, S, M> {
+    state: S,
+    message: M,
+    lt_str: &'a str,
+    common_field: i32,
+}
+
+struct State1;
+struct State2;
+
+struct Message1;
+struct Message2;
+
+fn update() {
+    let m1: Machine<State1, Message1> = Machine {
+        state: State1,
+        message: Message1,
+        lt_str: "hello",
+        common_field: 2,
+    };
+    // single type update
+    let m2: Machine<State2, Message1> = Machine {
+        state: State2,
+        ..m1
+    };
+    // multiple type update
+    let m3: Machine<State2, Message2> = Machine {
+        state: State2,
+        message: Message2,
+        ..m1
+    };
+}
+
+fn fail_update() {
+    let m1: Machine<f64, f64> = Machine {
+        state: 3.2,
+        message: 6.4,
+        lt_str: "hello",
+        common_field: 2,
+    };
+    // single type update fail
+    let m2: Machine<i32, f64> = Machine {
+        ..m1
+        //~^ ERROR mismatched types [E0308]
+    };
+    // multiple type update fail
+    let m3 = Machine::<i32, i32> {
+        ..m1
+        //~^ ERROR mismatched types [E0308]
+        //~| ERROR mismatched types [E0308]
+    };
+}
+
+fn main() {}

src/test/ui/rfcs/rfc-2528-type-changing-struct-update/type-generic-update.stderr

@@ -0,0 +1,30 @@
+error[E0308]: mismatched types
+  --> $DIR/type-generic-update.rs:46:11
+   |
+LL |         ..m1
+   |           ^^ field type mismatch: Machine.state
+   |
+   = note: expected type `i32`
+              found type `f64`
+
+error[E0308]: mismatched types
+  --> $DIR/type-generic-update.rs:51:11
+   |
+LL |         ..m1
+   |           ^^ field type mismatch: Machine.state
+   |
+   = note: expected type `i32`
+              found type `f64`
+
+error[E0308]: mismatched types
+  --> $DIR/type-generic-update.rs:51:11
+   |
+LL |         ..m1
+   |           ^^ field type mismatch: Machine.message
+   |
+   = note: expected type `i32`
+              found type `f64`
+
+error: aborting due to 3 previous errors
+
+For more information about this error, try `rustc --explain E0308`.