Don't forget that the lifetime on hir types is 'tcx

compiler/rustc_hir/src/hir.rs

@@ -248,7 +248,7 @@ pub struct InferArg {
 }
 
 impl InferArg {
-    pub fn to_ty(&self) -> Ty<'_> {
+    pub fn to_ty(&self) -> Ty<'static> {
         Ty { kind: TyKind::Infer, span: self.span, hir_id: self.hir_id }
     }
 }