rustdoc: be more strict about "Methods from Deref"

hack: is_doc_subtype_of always returns true for TyAlias

it's worth noting that this function is only used in
the handling of "Methods from Deref", and we were previously
assuming all generic parameters were meaningless,
so this is still an improvment from the status quo.

this change means that we will have strictly less false positives
without adding any new false negitives.

Co-authored-by: Guillaume Gomez <guillaume1.gomez@gmail.com>

1 files changed, 27 insertions, 0 deletions

diff --git a/tests/rustdoc/deref/deref-methods-24686-target.rs b/tests/rustdoc/deref/deref-methods-24686-target.rs
new file mode 100644
index 00000000000..e019488ca80
--- /dev/null
+++ b/tests/rustdoc/deref/deref-methods-24686-target.rs
@@ -0,0 +1,27 @@
+#![crate_name = "foo"]
+
+// test for https://github.com/rust-lang/rust/issues/24686
+use std::ops::Deref;
+
+pub struct Foo<T>(T);
+impl Foo<i32> {
+    pub fn get_i32(&self) -> i32 { self.0 }
+}
+impl Foo<u32> {
+    pub fn get_u32(&self) -> u32 { self.0 }
+}
+
+// Note that the same href is used both on the method itself,
+// and on the sidebar items.
+//@ has foo/struct.Bar.html
+//@ has - '//a[@href="#method.get_i32"]' 'get_i32'
+//@ !has - '//a[@href="#method.get_u32"]' 'get_u32'
+//@ count - '//ul[@class="block deref-methods"]//a' 1
+//@ count - '//a[@href="#method.get_i32"]' 2
+pub struct Bar(Foo<i32>);
+impl Deref for Bar {
+    type Target = Foo<i32>;
+    fn deref(&self) -> &Foo<i32> {
+        &self.0
+    }
+}