rustdoc: search for tuples and unit by type with ()

tests/rustdoc-js/tuple-unit.rs

@@ -0,0 +1,18 @@
+pub struct P;
+pub struct Q;
+pub struct R<T>(T);
+
+// Checks that tuple and unit both work
+pub fn side_effect() { }
+
+// Check a non-tuple
+pub fn not_tuple() -> P { loop {} }
+
+// Check a 1-tuple
+pub fn one() -> (P,) { loop {} }
+
+// Check a 2-tuple
+pub fn two() -> (P,P) { loop {} }
+
+// Check a nested tuple
+pub fn nest() -> (Q, R<(u32,)>) { loop {} }