Do not ICE on async fn with non-Copy infered type arg

Fix #66958.

src/librustc_mir/borrow_check/diagnostics/conflict_errors.rs

@@ -240,15 +240,16 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                     let tcx = self.infcx.tcx;
                     let generics = tcx.generics_of(self.mir_def_id);
                     let param = generics.type_param(&param_ty, tcx);
-                    let generics = tcx.hir().get_generics(self.mir_def_id).unwrap();
-                    suggest_constraining_type_param(
-                        generics,
-                        &mut err,
-                        &param.name.as_str(),
-                        "Copy",
-                        tcx.sess.source_map(),
-                        span,
-                    );
+                    if let Some(generics) = tcx.hir().get_generics(self.mir_def_id) {
+                        suggest_constraining_type_param(
+                            generics,
+                            &mut err,
+                            &param.name.as_str(),
+                            "Copy",
+                            tcx.sess.source_map(),
+                            span,
+                        );
+                    }
                 }
                 let span = if let Some(local) = place.as_local() {
                     let decl = &self.body.local_decls[local];

src/test/ui/issues/issue-66958.rs

@@ -0,0 +1,15 @@
+// edition:2018
+
+struct Ia<S>(u32, S);
+
+impl<S> Ia<S> {
+    fn partial(_: S) {}
+    fn full(self) {}
+
+    async fn crash(self) {
+        Self::partial(self.1);
+        Self::full(self); //~ ERROR use of moved value: `self`
+    }
+}
+
+fn main() {}

src/test/ui/issues/issue-66958.stderr

@@ -0,0 +1,13 @@
+error[E0382]: use of moved value: `self`
+  --> $DIR/issue-66958.rs:11:20
+   |
+LL |         Self::partial(self.1);
+   |                       ------ value moved here
+LL |         Self::full(self);
+   |                    ^^^^ value used here after partial move
+   |
+   = note: move occurs because `self.1` has type `S`, which does not implement the `Copy` trait
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0382`.