rustdoc-search: add search query syntax `Fn(T) -> U`

This is implemented, in addition to the ML-style one,
because Rust does it. If we don't, we'll never hear the end of it.

This commit also refactors some duplicate parts of the parser
into a dedicated function.

3 files changed, 348 insertions, 12 deletions

diff --git a/tests/rustdoc-js-std/parser-errors.js b/tests/rustdoc-js-std/parser-errors.js
index 8efb81841d4..ffd169812b6 100644
--- a/tests/rustdoc-js-std/parser-errors.js
+++ b/tests/rustdoc-js-std/parser-errors.js
@@ -195,7 +195,7 @@ const PARSED = [
         original: "a (b:",
         returned: [],
         userQuery: "a (b:",
-        error: "Expected `,`, `:` or `->`, found `(`",
+        error: "Unclosed `(`",
     },
     {
         query: "_:",
@@ -357,7 +357,16 @@ const PARSED = [
         original: "a,:",
         returned: [],
         userQuery: "a,:",
-        error: 'Unexpected `,` in type filter (before `:`)',
+        error: 'Expected type filter before `:`',
+    },
+    {
+        query: "a!:",
+        elems: [],
+        foundElems: 0,
+        original: "a!:",
+        returned: [],
+        userQuery: "a!:",
+        error: 'Unexpected `!` in type filter (before `:`)',
     },
     {
         query: "  a<>  :",
@@ -366,7 +375,7 @@ const PARSED = [
         original: "a<>  :",
         returned: [],
         userQuery: "a<>  :",
-        error: 'Unexpected `<` in type filter (before `:`)',
+        error: 'Expected `,`, `:` or `->` after `>`, found `:`',
     },
     {
         query: "mod : :",
diff --git a/tests/rustdoc-js-std/parser-hof.js b/tests/rustdoc-js-std/parser-hof.js
index 331c516e047..0b99c45b7a9 100644
--- a/tests/rustdoc-js-std/parser-hof.js
+++ b/tests/rustdoc-js-std/parser-hof.js
@@ -1,4 +1,5 @@
 const PARSED = [
+    // ML-style HOF
     {
         query: "(-> F<P>)",
         elems: [{
@@ -373,4 +374,339 @@ const PARSED = [
         userQuery: "x, trait:(aaaaa, b -> a)",
         error: null,
     },
+    // Rust-style HOF
+    {
+        query: "Fn () -> F<P>",
+        elems: [{
+            name: "fn",
+            fullPath: ["fn"],
+            pathWithoutLast: [],
+            pathLast: "fn",
+            generics: [],
+            bindings: [
+                [
+                    "output",
+                    [{
+                        name: "f",
+                        fullPath: ["f"],
+                        pathWithoutLast: [],
+                        pathLast: "f",
+                        generics: [
+                            {
+                                name: "p",
+                                fullPath: ["p"],
+                                pathWithoutLast: [],
+                                pathLast: "p",
+                                generics: [],
+                            },
+                        ],
+                        typeFilter: -1,
+                    }],
+                ],
+            ],
+            typeFilter: -1,
+        }],
+        foundElems: 1,
+        original: "Fn () -> F<P>",
+        returned: [],
+        userQuery: "fn () -> f<p>",
+        error: null,
+    },
+    {
+        query: "FnMut() -> P",
+        elems: [{
+            name: "fnmut",
+            fullPath: ["fnmut"],
+            pathWithoutLast: [],
+            pathLast: "fnmut",
+            generics: [],
+            bindings: [
+                [
+                    "output",
+                    [{
+                        name: "p",
+                        fullPath: ["p"],
+                        pathWithoutLast: [],
+                        pathLast: "p",
+                        generics: [],
+                        typeFilter: -1,
+                    }],
+                ],
+            ],
+            typeFilter: -1,
+        }],
+        foundElems: 1,
+        original: "FnMut() -> P",
+        returned: [],
+        userQuery: "fnmut() -> p",
+        error: null,
+    },
+    {
+        query: "(FnMut() -> P)",
+        elems: [{
+            name: "fnmut",
+            fullPath: ["fnmut"],
+            pathWithoutLast: [],
+            pathLast: "fnmut",
+            generics: [],
+            bindings: [
+                [
+                    "output",
+                    [{
+                        name: "p",
+                        fullPath: ["p"],
+                        pathWithoutLast: [],
+                        pathLast: "p",
+                        generics: [],
+                        typeFilter: -1,
+                    }],
+                ],
+            ],
+            typeFilter: -1,
+        }],
+        foundElems: 1,
+        original: "(FnMut() -> P)",
+        returned: [],
+        userQuery: "(fnmut() -> p)",
+        error: null,
+    },
+    {
+        query: "Fn(F<P>)",
+        elems: [{
+            name: "fn",
+            fullPath: ["fn"],
+            pathWithoutLast: [],
+            pathLast: "fn",
+            generics: [{
+                name: "f",
+                fullPath: ["f"],
+                pathWithoutLast: [],
+                pathLast: "f",
+                generics: [
+                    {
+                        name: "p",
+                        fullPath: ["p"],
+                        pathWithoutLast: [],
+                        pathLast: "p",
+                        generics: [],
+                    },
+                ],
+                typeFilter: -1,
+            }],
+            bindings: [
+                [
+                    "output",
+                    [],
+                ],
+            ],
+            typeFilter: -1,
+        }],
+        foundElems: 1,
+        original: "Fn(F<P>)",
+        returned: [],
+        userQuery: "fn(f<p>)",
+        error: null,
+    },
+    {
+        query: "primitive:fnonce(aaaaa, b) -> a",
+        elems: [{
+            name: "fnonce",
+            fullPath: ["fnonce"],
+            pathWithoutLast: [],
+            pathLast: "fnonce",
+            generics: [
+                {
+                    name: "aaaaa",
+                    fullPath: ["aaaaa"],
+                    pathWithoutLast: [],
+                    pathLast: "aaaaa",
+                    generics: [],
+                    typeFilter: -1,
+                },
+                {
+                    name: "b",
+                    fullPath: ["b"],
+                    pathWithoutLast: [],
+                    pathLast: "b",
+                    generics: [],
+                    typeFilter: -1,
+                },
+            ],
+            bindings: [
+                [
+                    "output",
+                    [{
+                        name: "a",
+                        fullPath: ["a"],
+                        pathWithoutLast: [],
+                        pathLast: "a",
+                        generics: [],
+                        typeFilter: -1,
+                    }],
+                ],
+            ],
+            typeFilter: 1,
+        }],
+        foundElems: 1,
+        original: "primitive:fnonce(aaaaa, b) -> a",
+        returned: [],
+        userQuery: "primitive:fnonce(aaaaa, b) -> a",
+        error: null,
+    },
+    {
+        query: "primitive:fnonce(aaaaa, keyword:b) -> trait:a",
+        elems: [{
+            name: "fnonce",
+            fullPath: ["fnonce"],
+            pathWithoutLast: [],
+            pathLast: "fnonce",
+            generics: [
+                {
+                    name: "aaaaa",
+                    fullPath: ["aaaaa"],
+                    pathWithoutLast: [],
+                    pathLast: "aaaaa",
+                    generics: [],
+                    typeFilter: -1,
+                },
+                {
+                    name: "b",
+                    fullPath: ["b"],
+                    pathWithoutLast: [],
+                    pathLast: "b",
+                    generics: [],
+                    typeFilter: 0,
+                },
+            ],
+            bindings: [
+                [
+                    "output",
+                    [{
+                        name: "a",
+                        fullPath: ["a"],
+                        pathWithoutLast: [],
+                        pathLast: "a",
+                        generics: [],
+                        typeFilter: 10,
+                    }],
+                ],
+            ],
+            typeFilter: 1,
+        }],
+        foundElems: 1,
+        original: "primitive:fnonce(aaaaa, keyword:b) -> trait:a",
+        returned: [],
+        userQuery: "primitive:fnonce(aaaaa, keyword:b) -> trait:a",
+        error: null,
+    },
+    {
+        query: "x, trait:fn(aaaaa, b -> a)",
+        elems: [
+            {
+                name: "x",
+                fullPath: ["x"],
+                pathWithoutLast: [],
+                pathLast: "x",
+                generics: [],
+                typeFilter: -1,
+            },
+            {
+                name: "fn",
+                fullPath: ["fn"],
+                pathWithoutLast: [],
+                pathLast: "fn",
+                generics: [
+                    {
+                        name: "->",
+                        fullPath: ["->"],
+                        pathWithoutLast: [],
+                        pathLast: "->",
+                        generics: [
+                            {
+                                name: "aaaaa",
+                                fullPath: ["aaaaa"],
+                                pathWithoutLast: [],
+                                pathLast: "aaaaa",
+                                generics: [],
+                                typeFilter: -1,
+                            },
+                            {
+                                name: "b",
+                                fullPath: ["b"],
+                                pathWithoutLast: [],
+                                pathLast: "b",
+                                generics: [],
+                                typeFilter: -1,
+                            },
+                        ],
+                        bindings: [
+                            [
+                                "output",
+                                [{
+                                    name: "a",
+                                    fullPath: ["a"],
+                                    pathWithoutLast: [],
+                                    pathLast: "a",
+                                    generics: [],
+                                    typeFilter: -1,
+                                }],
+                            ],
+                        ],
+                        typeFilter: -1,
+                    },
+                ],
+                bindings: [
+                    [
+                        "output",
+                        [],
+                    ]
+                ],
+                typeFilter: 10,
+            }
+        ],
+        foundElems: 2,
+        original: "x, trait:fn(aaaaa, b -> a)",
+        returned: [],
+        userQuery: "x, trait:fn(aaaaa, b -> a)",
+        error: null,
+    },
+    {
+        query: 'a,b(c)',
+        elems: [
+            {
+                name: "a",
+                fullPath: ["a"],
+                pathWithoutLast: [],
+                pathLast: "a",
+                generics: [],
+                typeFilter: -1,
+            },
+            {
+                name: "b",
+                fullPath: ["b"],
+                pathWithoutLast: [],
+                pathLast: "b",
+                generics: [{
+                    name: "c",
+                    fullPath: ["c"],
+                    pathWithoutLast: [],
+                    pathLast: "c",
+                    generics: [],
+                    typeFilter: -1,
+                }],
+                bindings: [
+                    [
+                        "output",
+                        [],
+                    ]
+                ],
+                typeFilter: -1,
+            }
+        ],
+        foundElems: 2,
+        original: "a,b(c)",
+        returned: [],
+        userQuery: "a,b(c)",
+        error: null,
+    },
 ];
diff --git a/tests/rustdoc-js-std/parser-weird-queries.js b/tests/rustdoc-js-std/parser-weird-queries.js
index 26b8c32d680..499b82a3469 100644
--- a/tests/rustdoc-js-std/parser-weird-queries.js
+++ b/tests/rustdoc-js-std/parser-weird-queries.js
@@ -38,15 +38,6 @@ const PARSED = [
         error: null,
     },
     {
-        query: 'a,b(c)',
-        elems: [],
-        foundElems: 0,
-        original: "a,b(c)",
-        returned: [],
-        userQuery: "a,b(c)",
-        error: "Expected `,`, `:` or `->`, found `(`",
-    },
-    {
         query: 'aaa,a',
         elems: [
             {