Resolve vars before calling unnormalized_obligations

compiler/rustc_trait_selection/src/traits/query/type_op/implied_outlives_bounds.rs

@@ -95,6 +95,7 @@ pub fn compute_implied_outlives_bounds_inner<'tcx>(
             continue;
         }
 
+        let arg = ocx.infcx.resolve_vars_if_possible(arg);
         // From the full set of obligations, just filter down to the region relationships.
         for obligation in
             wf::unnormalized_obligations(ocx.infcx, param_env, arg, DUMMY_SP, CRATE_DEF_ID)

tests/ui/traits/next-solver/implied_outlives_bounds_not_resolving_vars_ice.rs

@@ -0,0 +1,19 @@
+//@ compile-flags: -Znext-solver
+
+// Regression test for https://github.com/rust-lang/rust-clippy/issues/17439
+
+#![feature(inherent_associated_types)]
+
+struct Foo<T>(T);
+
+impl<'a> Foo<fn(&'a ())> {
+    type Assoc = &'a ();
+}
+
+fn bar(_: fn(Foo<for<'b> fn(Foo<fn(&'b ())>::Assoc)>::Assoc)) {}
+//~^ ERROR: higher-ranked subtype error
+//~| ERROR: higher-ranked subtype error
+//~| ERROR: lifetime bound not satisfied [E0478]
+//~| ERROR: lifetime bound not satisfied [E0478]
+
+fn main() {}

tests/ui/traits/next-solver/implied_outlives_bounds_not_resolving_vars_ice.stderr

@@ -0,0 +1,29 @@
+error[E0478]: lifetime bound not satisfied
+  --> $DIR/implied_outlives_bounds_not_resolving_vars_ice.rs:13:11
+   |
+LL | fn bar(_: fn(Foo<for<'b> fn(Foo<fn(&'b ())>::Assoc)>::Assoc)) {}
+   |           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error[E0478]: lifetime bound not satisfied
+  --> $DIR/implied_outlives_bounds_not_resolving_vars_ice.rs:13:11
+   |
+LL | fn bar(_: fn(Foo<for<'b> fn(Foo<fn(&'b ())>::Assoc)>::Assoc)) {}
+   |           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
+
+error: higher-ranked subtype error
+  --> $DIR/implied_outlives_bounds_not_resolving_vars_ice.rs:13:1
+   |
+LL | fn bar(_: fn(Foo<for<'b> fn(Foo<fn(&'b ())>::Assoc)>::Assoc)) {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: higher-ranked subtype error
+  --> $DIR/implied_outlives_bounds_not_resolving_vars_ice.rs:13:8
+   |
+LL | fn bar(_: fn(Foo<for<'b> fn(Foo<fn(&'b ())>::Assoc)>::Assoc)) {}
+   |        ^
+
+error: aborting due to 4 previous errors
+
+For more information about this error, try `rustc --explain E0478`.