rustdoc-search: parse and search with ML-style HOF

Option::map, for example, looks like this:

    option<t>, (t -> u) -> option<u>

This syntax searches all of the HOFs in Rust: traits Fn, FnOnce,
and FnMut, and bare fn primitives.

2 files changed, 106 insertions, 0 deletions

diff --git a/tests/rustdoc-js/hof.js b/tests/rustdoc-js/hof.js
new file mode 100644
index 00000000000..1f5d2bfb666
--- /dev/null
+++ b/tests/rustdoc-js/hof.js
@@ -0,0 +1,94 @@
+// exact-check
+
+const EXPECTED = [
+    // ML-style higher-order function notation
+    {
+        'query': 'bool, (u32 -> !) -> ()',
+        'others': [
+            {"path": "hof", "name": "fn_ptr"},
+        ],
+    },
+    {
+        'query': 'u8, (u32 -> !) -> ()',
+        'others': [
+            {"path": "hof", "name": "fn_once"},
+        ],
+    },
+    {
+        'query': 'i8, (u32 -> !) -> ()',
+        'others': [
+            {"path": "hof", "name": "fn_mut"},
+        ],
+    },
+    {
+        'query': 'char, (u32 -> !) -> ()',
+        'others': [
+            {"path": "hof", "name": "fn_"},
+        ],
+    },
+    {
+        'query': '(first<u32> -> !) -> ()',
+        'others': [
+            {"path": "hof", "name": "fn_ptr"},
+        ],
+    },
+    {
+        'query': '(second<u32> -> !) -> ()',
+        'others': [
+            {"path": "hof", "name": "fn_once"},
+        ],
+    },
+    {
+        'query': '(third<u32> -> !) -> ()',
+        'others': [
+            {"path": "hof", "name": "fn_mut"},
+        ],
+    },
+    {
+        'query': '(u32 -> !) -> ()',
+        'others': [
+            {"path": "hof", "name": "fn_"},
+            {"path": "hof", "name": "fn_ptr"},
+            {"path": "hof", "name": "fn_mut"},
+            {"path": "hof", "name": "fn_once"},
+        ],
+    },
+    {
+        'query': 'u32 -> !',
+        // not a HOF query
+        'others': [],
+    },
+    {
+        'query': '(str, str -> i8) -> ()',
+        'others': [
+            {"path": "hof", "name": "multiple"},
+        ],
+    },
+    {
+        'query': '(str ->) -> ()',
+        'others': [
+            {"path": "hof", "name": "multiple"},
+        ],
+    },
+    {
+        'query': '(-> i8) -> ()',
+        'others': [
+            {"path": "hof", "name": "multiple"},
+        ],
+    },
+    {
+        'query': '(str -> str) -> ()',
+        // params and return are not the same
+        'others': [],
+    },
+    {
+        'query': '(i8 ->) -> ()',
+        // params and return are not the same
+        'others': [],
+    },
+    {
+        'query': '(-> str) -> ()',
+        // params and return are not the same
+        'others': [],
+    },
+];
diff --git a/tests/rustdoc-js/hof.rs b/tests/rustdoc-js/hof.rs
new file mode 100644
index 00000000000..4d2c6e331ca
--- /dev/null
+++ b/tests/rustdoc-js/hof.rs
@@ -0,0 +1,12 @@
+#![feature(never_type)]
+
+pub struct First<T>(T);
+pub struct Second<T>(T);
+pub struct Third<T>(T);
+
+pub fn fn_ptr(_: fn (First<u32>) -> !, _: bool) {}
+pub fn fn_once(_: impl FnOnce (Second<u32>) -> !, _: u8) {}
+pub fn fn_mut(_: impl FnMut (Third<u32>) -> !, _: i8) {}
+pub fn fn_(_: impl Fn (u32) -> !, _: char) {}
+
+pub fn multiple(_: impl Fn(&'static str, &'static str) -> i8) {}