closure-requirements: add regression tests

Author: lcnr

tests/ui/nll/closure-requirements/thread_scope_correct_implied_bound.rs

@@ -0,0 +1,23 @@
+// This example broke while refactoring the way closure
+// requirements are handled. The setup here matches
+// `thread::scope`.
+
+//@ check-pass
+
+struct Outlives<'hr, 'scope: 'hr>(*mut (&'scope (), &'hr ()));
+impl<'hr, 'scope> Outlives<'hr, 'scope> {
+    fn outlives_hr<T: 'hr>(self) {}
+}
+
+fn takes_closure_implied_bound<'scope>(f: impl for<'hr> FnOnce(Outlives<'hr, 'scope>)) {}
+
+fn requires_external_outlives_hr<T>() {
+    // implied bounds:
+    // - `T: 'scope` as `'scope` is local to this function
+    // - `'scope: 'hr` as it's an implied bound of `Outlives`
+    //
+    // need to prove `T: 'hr` :>
+    takes_closure_implied_bound(|proof| proof.outlives_hr::<T>());
+}
+
+fn main() {}

tests/ui/nll/closure-requirements/thread_scope_incorrect_implied_bound.rs

@@ -0,0 +1,21 @@
+// This example incorrectly compiled while refactoring the way
+// closure requirements are handled.
+
+struct Outlives<'hr: 'scope, 'scope>(*mut (&'scope (), &'hr ()));
+impl<'hr, 'scope> Outlives<'hr, 'scope> {
+    fn outlives_hr<T: 'hr>(self) {}
+}
+
+fn takes_closure_implied_bound<'scope>(f: impl for<'hr> FnOnce(Outlives<'hr, 'scope>)) {}
+
+fn requires_external_outlives_hr<T>() {
+    // implied bounds:
+    // - `T: 'scope` as `'scope` is local to this function
+    // - `'hr: 'scope` as it's an implied bound of `Outlives`
+    //
+    // need to prove `T: 'hr` :<
+    takes_closure_implied_bound(|proof| proof.outlives_hr::<T>());
+    //~^ ERROR the parameter type `T` may not live long enough
+}
+
+fn main() {}

tests/ui/nll/closure-requirements/thread_scope_incorrect_implied_bound.stderr

@@ -0,0 +1,17 @@
+error[E0310]: the parameter type `T` may not live long enough
+  --> $DIR/thread_scope_incorrect_implied_bound.rs:17:47
+   |
+LL |     takes_closure_implied_bound(|proof| proof.outlives_hr::<T>());
+   |                                               ^^^^^^^^^^^
+   |                                               |
+   |                                               the parameter type `T` must be valid for the static lifetime...
+   |                                               ...so that the type `T` will meet its required lifetime bounds
+   |
+help: consider adding an explicit lifetime bound
+   |
+LL | fn requires_external_outlives_hr<T: 'static>() {
+   |                                   +++++++++
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0310`.

tests/ui/nll/ty-outlives/projection-implied-bounds.rs

@@ -1,8 +1,6 @@
 // Test that we can deduce when projections like `T::Item` outlive the
 // function body. Test that this does not imply that `T: 'a` holds.
 
-//@ compile-flags:-Zverbose-internals
-
 use std::cell::Cell;
 
 fn twice<F, T>(mut value: T, mut f: F)

tests/ui/nll/ty-outlives/projection-implied-bounds.stderr

@@ -1,5 +1,5 @@
 error[E0310]: the parameter type `T` may not live long enough
-  --> $DIR/projection-implied-bounds.rs:30:36
+  --> $DIR/projection-implied-bounds.rs:28:36
    |
 LL |     twice(value, |value_ref, item| invoke2(value_ref, item));
    |                                    ^^^^^^^^^^^^^^^^^^^^^^^^