unify closures and generator handling in wf

Author: aliemjay

compiler/rustc_trait_selection/src/traits/wf.rs

@@ -681,23 +681,9 @@ impl<'a, 'tcx> WfPredicates<'a, 'tcx> {
 
                 ty::GeneratorWitness(..) | ty::GeneratorWitnessMIR(..) => {
                     // Unspecified in RFC 1214.
-                    // They are always WF when the gnereator passes typeck/borrowck.
-                    walker.skip_current_subtree();
                 }
 
-                ty::Generator(did, args, ..) => {
-                    // Walk ALL the types in the generator: this will
-                    // include the upvar types as well as the yield
-                    // type. Note that this is mildly distinct from
-                    // the closure case, where we have to be careful
-                    // about the signature of the closure. We don't
-                    // have the problem of implied bounds here since
-                    // generators don't take arguments.
-                    let obligations = self.nominal_obligations(did, args);
-                    self.out.extend(obligations);
-                }
-
-                ty::Closure(did, args) => {
+                ty::Closure(did, args) | ty::Generator(did, args, ..) => {
                     // Only check the upvar types for WF, not the rest
                     // of the types within. This is needed because we
                     // capture the signature and it may not be WF
@@ -719,8 +705,15 @@ impl<'a, 'tcx> WfPredicates<'a, 'tcx> {
                     // shorthand for something like `where(T: 'a) {
                     // fn(&'a T) }`, as discussed in #25860.
                     walker.skip_current_subtree(); // subtree handled below
+
+                    let upvars = match ty.kind() {
+                        ty::Closure(..) => args.as_closure().tupled_upvars_ty(),
+                        ty::Generator(..) => args.as_generator().tupled_upvars_ty(),
+                        _ => unreachable!(),
+                    };
                     // FIXME(eddyb) add the type to `walker` instead of recursing.
-                    self.compute(args.as_closure().tupled_upvars_ty().into());
+                    self.compute(upvars.into());
+
                     // Note that we cannot skip the generic types
                     // types. Normally, within the fn
                     // body where they are created, the generics will

tests/ui/async-await/generator-wf-check.output_wf.stderr

@@ -4,7 +4,7 @@
 // edition: 2021
 // revisions: output output_wf witness witness_wf
 //[output] check-pass
-//[output_wf] check-fail
+//[output_wf] check-pass
 //[witness] check-fail
 //[witness_wf] check-fail
 
@@ -22,7 +22,6 @@ fn test_output<T>() {
 #[cfg(output_wf)]
 fn test_output_wf<T>() {
     wf(async {
-    //[output_wf]~^ ERROR `T` may not live long enough
         None::<Static<T>>
     });
 }

tests/ui/async-await/generator-wf-check.rs

@@ -1,5 +1,5 @@
 error[E0310]: the parameter type `T` may not live long enough
-  --> $DIR/generator-wf-check.rs:33:22
+  --> $DIR/generator-wf-check.rs:32:22
    |
 LL |         let witness: Option<Static<T>> = None;
    |                      ^^^^^^^^^^^^^^^^^ ...so that the type `T` will meet its required lifetime bounds
@@ -10,7 +10,7 @@ LL | fn test_witness<T: 'static>() {
    |                  +++++++++
 
 error[E0310]: the parameter type `T` may not live long enough
-  --> $DIR/generator-wf-check.rs:36:9
+  --> $DIR/generator-wf-check.rs:35:9
    |
 LL |         drop(witness);
    |         ^^^^^^^^^^^^^ ...so that the type `T` will meet its required lifetime bounds

tests/ui/async-await/generator-wf-check.witness.stderr

@@ -1,5 +1,5 @@
 error[E0310]: the parameter type `T` may not live long enough
-  --> $DIR/generator-wf-check.rs:44:22
+  --> $DIR/generator-wf-check.rs:43:22
    |
 LL |         let witness: Option<Static<T>> = None;
    |                      ^^^^^^^^^^^^^^^^^ ...so that the type `T` will meet its required lifetime bounds
@@ -10,7 +10,7 @@ LL | fn test_witness_wf<T: 'static>() {
    |                     +++++++++
 
 error[E0310]: the parameter type `T` may not live long enough
-  --> $DIR/generator-wf-check.rs:47:9
+  --> $DIR/generator-wf-check.rs:46:9
    |
 LL |         drop(witness);
    |         ^^^^^^^^^^^^^ ...so that the type `T` will meet its required lifetime bounds