rustdoc_json: Add a test for some GenericArgs cases.

Author: nnethercote

tests/rustdoc-json/generic-args.rs

@@ -0,0 +1,20 @@
+pub struct MyStruct(u32);
+
+pub trait MyTrait {
+    type MyType;
+    fn my_fn(&self);
+}
+
+impl MyTrait for MyStruct {
+    type MyType = u32;
+    fn my_fn(&self) {}
+}
+
+//@ is "$.index[?(@.name=='my_fn1')].inner.function.sig.inputs[0][1].qualified_path.args" {\"angle_bracketed\":{\"args\":[],\"constraints\":[]}}
+//@ is "$.index[?(@.name=='my_fn1')].inner.function.sig.inputs[0][1].qualified_path.self_type.resolved_path.args" {\"angle_bracketed\":{\"args\":[],\"constraints\":[]}}
+pub fn my_fn1(_: <MyStruct as MyTrait>::MyType) {}
+
+//@ is "$.index[?(@.name=='my_fn2')].inner.function.sig.inputs[0][1].dyn_trait.traits[0].trait.args.angle_bracketed.constraints[0].args" {\"angle_bracketed\":{\"args\":[],\"constraints\":[]}}
+pub fn my_fn2(_: IntoIterator<Item = MyStruct, IntoIter = impl Clone>) {}
+
+fn main() {}