Improve the cycle tests

src/test/ui/associated-types/defaults-cyclic-fail-1.rs

@@ -15,6 +15,10 @@ impl Tr for u8 {
     type A = u8;
 }
 
+impl Tr for u16 {
+    type B = ();
+}
+
 impl Tr for u32 {
     type A = ();
     type B = u8;
@@ -28,8 +32,14 @@ impl Tr for bool {
 }
 // (the error is shown twice for some reason)
 
-fn main() {
-    // Check that the overridden type propagates to the other
-    let _a: <u8 as Tr>::A = 0u8;
-    let _b: <u8 as Tr>::B = 0u8;
+impl Tr for usize {
+//~^ ERROR overflow evaluating the requirement
+    type B = &'static Self::A;
+    //~^ ERROR overflow evaluating the requirement
+}
+
+fn main() {
+    // We don't check that the types project correctly because the cycle errors stop compilation
+    // before `main` is type-checked.
+    // `defaults-cyclic-pass-1.rs` does this.
 }

src/test/ui/associated-types/defaults-cyclic-fail-1.stderr

@@ -0,0 +1,33 @@
+error[E0275]: overflow evaluating the requirement `<() as Tr>::B`
+  --> $DIR/defaults-cyclic-fail-1.rs:12:6
+   |
+LL | impl Tr for () {}
+   |      ^^
+
+error[E0275]: overflow evaluating the requirement `<bool as Tr>::B`
+  --> $DIR/defaults-cyclic-fail-1.rs:30:6
+   |
+LL | impl Tr for bool {
+   |      ^^
+
+error[E0275]: overflow evaluating the requirement `<usize as Tr>::B`
+  --> $DIR/defaults-cyclic-fail-1.rs:37:6
+   |
+LL | impl Tr for usize {
+   |      ^^
+
+error[E0275]: overflow evaluating the requirement `<bool as Tr>::B`
+  --> $DIR/defaults-cyclic-fail-1.rs:32:5
+   |
+LL |     type A = Box<Self::B>;
+   |     ^^^^^^^^^^^^^^^^^^^^^^
+
+error[E0275]: overflow evaluating the requirement `<usize as Tr>::A`
+  --> $DIR/defaults-cyclic-fail-1.rs:39:5
+   |
+LL |     type B = &'static Self::A;
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 5 previous errors
+
+For more information about this error, try `rustc --explain E0275`.

src/test/ui/associated-types/defaults-cyclic-fail-2.rs

@@ -0,0 +1,49 @@
+// compile-fail
+
+#![feature(associated_type_defaults)]
+
+// A more complex version of `defaults-cyclic-fail-1.rs`, with non-trivial defaults.
+
+// Having a cycle in assoc. type defaults is okay...
+trait Tr {
+    type A = Vec<Self::B>;
+    type B = Box<Self::A>;
+}
+
+// ...but is an error in any impl that doesn't override at least one of the defaults
+impl Tr for () {}
+//~^ ERROR overflow evaluating the requirement
+
+// As soon as at least one is redefined, it works:
+impl Tr for u8 {
+    type A = u8;
+}
+
+impl Tr for u16 {
+    type B = ();
+}
+
+impl Tr for u32 {
+    type A = ();
+    type B = u8;
+}
+
+// ...but only if this actually breaks the cycle
+impl Tr for bool {
+//~^ ERROR overflow evaluating the requirement
+    type A = Box<Self::B>;
+    //~^ ERROR overflow evaluating the requirement
+}
+// (the error is shown twice for some reason)
+
+impl Tr for usize {
+//~^ ERROR overflow evaluating the requirement
+    type B = &'static Self::A;
+    //~^ ERROR overflow evaluating the requirement
+}
+
+fn main() {
+    // We don't check that the types project correctly because the cycle errors stop compilation
+    // before `main` is type-checked.
+    // `defaults-cyclic-pass-2.rs` does this.
+}

src/test/ui/associated-types/defaults-cyclic-fail-2.stderr

@@ -0,0 +1,33 @@
+error[E0275]: overflow evaluating the requirement `<() as Tr>::B`
+  --> $DIR/defaults-cyclic-fail-2.rs:14:6
+   |
+LL | impl Tr for () {}
+   |      ^^
+
+error[E0275]: overflow evaluating the requirement `<bool as Tr>::B`
+  --> $DIR/defaults-cyclic-fail-2.rs:32:6
+   |
+LL | impl Tr for bool {
+   |      ^^
+
+error[E0275]: overflow evaluating the requirement `<usize as Tr>::B`
+  --> $DIR/defaults-cyclic-fail-2.rs:39:6
+   |
+LL | impl Tr for usize {
+   |      ^^
+
+error[E0275]: overflow evaluating the requirement `<bool as Tr>::B`
+  --> $DIR/defaults-cyclic-fail-2.rs:34:5
+   |
+LL |     type A = Box<Self::B>;
+   |     ^^^^^^^^^^^^^^^^^^^^^^
+
+error[E0275]: overflow evaluating the requirement `<usize as Tr>::A`
+  --> $DIR/defaults-cyclic-fail-2.rs:41:5
+   |
+LL |     type B = &'static Self::A;
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 5 previous errors
+
+For more information about this error, try `rustc --explain E0275`.

src/test/ui/associated-types/defaults-cyclic-fail.stderr

@@ -1,21 +0,0 @@
-error[E0275]: overflow evaluating the requirement `<() as Tr>::B`
-  --> $DIR/defaults-cyclic-fail.rs:10:6
-   |
-LL | impl Tr for () {}
-   |      ^^
-
-error[E0275]: overflow evaluating the requirement `<bool as Tr>::B`
-  --> $DIR/defaults-cyclic-fail.rs:24:6
-   |
-LL | impl Tr for bool {
-   |      ^^
-
-error[E0275]: overflow evaluating the requirement `<bool as Tr>::B`
-  --> $DIR/defaults-cyclic-fail.rs:26:5
-   |
-LL |     type A = Box<Self::B>;
-   |     ^^^^^^^^^^^^^^^^^^^^^^
-
-error: aborting due to 3 previous errors
-
-For more information about this error, try `rustc --explain E0275`.

src/test/ui/associated-types/defaults-cyclic-pass-1.rs

@@ -0,0 +1,56 @@
+// check-pass
+
+#![feature(associated_type_defaults)]
+
+// Having a cycle in assoc. type defaults is okay, as long as there's no impl
+// that retains it.
+trait Tr {
+    type A = Self::B;
+    type B = Self::A;
+
+    fn f();
+}
+
+// An impl has to break the cycle to be accepted.
+impl Tr for u8 {
+    type A = u8;
+
+    fn f() {
+        // Check that the type propagates as expected (seen from inside the impl)
+        let _: Self::A = 0u8;
+        let _: Self::B = 0u8;
+    }
+}
+
+impl Tr for String {
+    type B = ();
+
+    fn f() {
+        // Check that the type propagates as expected (seen from inside the impl)
+        let _: Self::A = ();
+        let _: Self::B = ();
+    }
+}
+
+impl Tr for () {
+    type A = Vec<()>;
+    type B = u8;
+
+    fn f() {
+        // Check that the type propagates as expected (seen from inside the impl)
+        let _: Self::A = Vec::<()>::new();
+        let _: Self::B = 0u8;
+    }
+}
+
+fn main() {
+    // Check that both impls now have the right types (seen from outside the impls)
+    let _: <u8 as Tr>::A = 0u8;
+    let _: <u8 as Tr>::B = 0u8;
+
+    let _: <String as Tr>::A = ();
+    let _: <String as Tr>::B = ();
+
+    let _: <() as Tr>::A = Vec::<()>::new();
+    let _: <() as Tr>::B = 0u8;
+}

src/test/ui/associated-types/defaults-cyclic-pass-2.rs

@@ -0,0 +1,56 @@
+// check-pass
+
+#![feature(associated_type_defaults)]
+
+// Having a cycle in assoc. type defaults is okay, as long as there's no impl
+// that retains it.
+trait Tr {
+    type A = Vec<Self::B>;
+    type B = Box<Self::A>;
+
+    fn f();
+}
+
+// An impl has to break the cycle to be accepted.
+impl Tr for u8 {
+    type A = u8;
+
+    fn f() {
+        // Check that the type propagates as expected (seen from inside the impl)
+        let _: Self::A = 0u8;
+        let _: Self::B = Box::new(0u8);
+    }
+}
+
+impl Tr for String {
+    type B = ();
+
+    fn f() {
+        // Check that the type propagates as expected (seen from inside the impl)
+        let _: Self::A = Vec::<()>::new();
+        let _: Self::B = ();
+    }
+}
+
+impl Tr for () {
+    type A = Vec<()>;
+    type B = u8;
+
+    fn f() {
+        // Check that the type propagates as expected (seen from inside the impl)
+        let _: Self::A = Vec::<()>::new();
+        let _: Self::B = 0u8;
+    }
+}
+
+fn main() {
+    // Check that both impls now have the right types (seen from outside the impls)
+    let _: <u8 as Tr>::A = 0u8;
+    let _: <u8 as Tr>::B = Box::new(0u8);
+
+    let _: <String as Tr>::A = Vec::<()>::new();
+    let _: <String as Tr>::B = ();
+
+    let _: <() as Tr>::A = Vec::<()>::new();
+    let _: <() as Tr>::B = 0u8;
+}

src/test/ui/associated-types/defaults-cyclic-pass.rs

@@ -1,17 +0,0 @@
-// check-pass
-
-#![feature(associated_type_defaults)]
-
-// Having a cycle in assoc. type defaults is okay, as long as there's no impl
-// that retains it.
-trait Tr {
-    type A = Self::B;
-    type B = Self::A;
-}
-
-// An impl has to break the cycle to be accepted.
-impl Tr for u8 {
-    type A = u8;
-}
-
-fn main() {}