add new tests for re_rebalance_coherence

src/test/ui/coherence/impl[t]-foreign[foreign[t],local]-for-foreign.rs

@@ -0,0 +1,14 @@
+#![feature(re_rebalance_coherence)]
+
+// check-pass
+// compile-flags:--crate-name=test
+// aux-build:coherence_lib.rs
+
+extern crate coherence_lib as lib;
+use lib::*;
+use std::rc::Rc;
+
+struct Local;
+impl<T> Remote2<Rc<T>, Local> for usize { }
+
+fn main() {}

src/test/ui/coherence/impl[t]-foreign[local]-for-fundamental[t].rs

@@ -0,0 +1,21 @@
+#![feature(re_rebalance_coherence)]
+
+// compile-flags:--crate-name=test
+// aux-build:coherence_lib.rs
+// check-pass
+
+extern crate coherence_lib as lib;
+use lib::*;
+use std::rc::Rc;
+
+struct Local;
+
+impl<T> Remote1<Local> for Box<T> {
+    // FIXME(#64412) -- this is expected to error
+}
+
+impl<T> Remote1<Local> for &T {
+    // FIXME(#64412) -- this is expected to error
+}
+
+fn main() {}

src/test/ui/coherence/impl[t]-foreign[local]-for-t.rs

@@ -0,0 +1,16 @@
+#![feature(re_rebalance_coherence)]
+
+// compile-flags:--crate-name=test
+// aux-build:coherence_lib.rs
+
+extern crate coherence_lib as lib;
+use lib::*;
+use std::rc::Rc;
+
+struct Local;
+
+impl<T> Remote1<Local> for T {
+    //~^ ERROR type parameter `T` must be used as the type parameter for some local type
+}
+
+fn main() {}

src/test/ui/coherence/impl[t]-foreign[local]-for-t.stderr

@@ -0,0 +1,11 @@
+error[E0210]: type parameter `T` must be used as the type parameter for some local type (e.g., `MyStruct<T>`)
+  --> $DIR/impl[t]-foreign[local]-for-t.rs:12:1
+   |
+LL | impl<T> Remote1<Local> for T {
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type parameter `T` must be used as the type parameter for some local type
+   |
+   = note: only traits defined in the current crate can be implemented for a type parameter
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0210`.