rustdoc-json: Improve test for auto-trait impls

Author: aDotInTheVoid

tests/rustdoc-json/impls/auto.rs

@@ -17,6 +17,8 @@ impl Foo {
 // Testing spans, so all tests below code
 //@ is "$.index[?(@.docs=='has span')].span.begin" "[13, 1]"
 //@ is "$.index[?(@.docs=='has span')].span.end" "[15, 2]"
-// FIXME: this doesn't work due to https://github.com/freestrings/jsonpath/issues/91
-// is "$.index[?(@.inner.impl.is_synthetic==true)].span" null
+//@ is "$.index[?(@.docs=='has span')].inner.impl.is_synthetic" false
+//@ is "$.index[?(@.inner.impl.is_synthetic==true)].span" null
+//@ is "$.index[?(@.inner.impl.is_synthetic==true)].inner.impl.for.resolved_path.path" '"Foo"'
+//@ is "$.index[?(@.inner.impl.is_synthetic==true)].inner.impl.trait.path" '"Bar"'
 pub struct Foo;