rustdoc-search: allow `:: ` and ` ::`

This restriction made sense back when spaces separated function
parameters, but now that they separate path components, there's
no real ambiguity any more.

Additionally, the Rust language allows it.

src/librustdoc/html/static/js/search.js

@@ -512,18 +512,15 @@ function initSearch(rawSearchIndex) {
                 bindingName,
             };
         }
+        const quadcolon = /::\s*::/.exec(path);
         if (path.startsWith("::")) {
             throw ["Paths cannot start with ", "::"];
         } else if (path.endsWith("::")) {
             throw ["Paths cannot end with ", "::"];
-        } else if (path.includes("::::")) {
-            throw ["Unexpected ", "::::"];
-        } else if (path.includes(" ::")) {
-            throw ["Unexpected ", " ::"];
-        } else if (path.includes(":: ")) {
-            throw ["Unexpected ", ":: "];
+        } else if (quadcolon !== null) {
+            throw ["Unexpected ", quadcolon[0]];
         }
-        const pathSegments = path.split(/::|\s+/);
+        const pathSegments = path.split(/(?:::\s*)|(?:\s+(?:::\s*)?)/);
         // In case we only have something like `<p>`, there is no name.
         if (pathSegments.length === 0 || (pathSegments.length === 1 && pathSegments[0] === "")) {
             if (generics.length > 0 || prevIs(parserState, ">")) {

tests/rustdoc-js-std/parser-errors.js

@@ -143,6 +143,15 @@ const PARSED = [
         userQuery: "a::::b",
         error: "Unexpected `::::`",
     },
+    {
+        query: "a:: ::b",
+        elems: [],
+        foundElems: 0,
+        original: "a:: ::b",
+        returned: [],
+        userQuery: "a:: ::b",
+        error: "Unexpected `:: ::`",
+    },
     {
         query: "a::b::",
         elems: [],
@@ -314,24 +323,6 @@ const PARSED = [
         userQuery: 'a<->',
         error: 'Unexpected `-` after `<`',
     },
-    {
-        query: "a:: a",
-        elems: [],
-        foundElems: 0,
-        original: 'a:: a',
-        returned: [],
-        userQuery: 'a:: a',
-        error: 'Unexpected `:: `',
-    },
-    {
-        query: "a ::a",
-        elems: [],
-        foundElems: 0,
-        original: 'a ::a',
-        returned: [],
-        userQuery: 'a ::a',
-        error: 'Unexpected ` ::`',
-    },
     {
         query: "a<a>:",
         elems: [],

tests/rustdoc-js-std/parser-paths.js

@@ -15,6 +15,54 @@ const PARSED = [
         userQuery: "a::b",
         error: null,
     },
+    {
+        query: "a:: a",
+        elems: [{
+            name: "a:: a",
+            fullPath: ["a", "a"],
+            pathWithoutLast: ["a"],
+            pathLast: "a",
+            generics: [],
+            typeFilter: -1,
+        }],
+        foundElems: 1,
+        original: 'a:: a',
+        returned: [],
+        userQuery: 'a:: a',
+        error: null,
+    },
+    {
+        query: "a ::a",
+        elems: [{
+            name: "a ::a",
+            fullPath: ["a", "a"],
+            pathWithoutLast: ["a"],
+            pathLast: "a",
+            generics: [],
+            typeFilter: -1,
+        }],
+        foundElems: 1,
+        original: 'a ::a',
+        returned: [],
+        userQuery: 'a ::a',
+        error: null,
+    },
+    {
+        query: "a  ::  a",
+        elems: [{
+            name: "a  ::  a",
+            fullPath: ["a", "a"],
+            pathWithoutLast: ["a"],
+            pathLast: "a",
+            generics: [],
+            typeFilter: -1,
+        }],
+        foundElems: 1,
+        original: 'a  ::  a',
+        returned: [],
+        userQuery: 'a  ::  a',
+        error: null,
+    },
     {
         query: 'A::B,C',
         elems: [