rustdoc: fix generics tracking bug in type binding

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

@@ -1545,11 +1545,12 @@ function initSearch(rawSearchIndex) {
                 for (j = i; j !== fl; ++j) {
                     const fnType = fnTypes[j];
                     if (unifyFunctionTypeIsMatchCandidate(fnType, queryElem, whereClause, mgens)) {
+                        const mgensScratch = new Map(mgens);
                         const simplifiedGenerics = unifyFunctionTypeCheckBindings(
                             fnType,
                             queryElem,
                             whereClause,
-                            mgens
+                            mgensScratch
                         );
                         if (simplifiedGenerics) {
                             if (!fnTypesScratch) {
@@ -1559,7 +1560,7 @@ function initSearch(rawSearchIndex) {
                                 simplifiedGenerics,
                                 queryElem.generics,
                                 whereClause,
-                                mgens,
+                                mgensScratch,
                                 mgensScratch => {
                                     matchCandidates.push({
                                         fnTypesScratch,
@@ -1635,7 +1636,7 @@ function initSearch(rawSearchIndex) {
          *
          * @param {FunctionType} fnType
          * @param {QueryElement} queryElem
-         * @param {[FunctionType]} whereClause - Trait bounds for generic items.
+         * @param {[FunctionSearchType]} whereClause - Trait bounds for generic items.
          * @param {Map<number,number>|null} mgensIn - Map functions generics to query generics.
          * @returns {boolean}
          */
@@ -1725,10 +1726,11 @@ function initSearch(rawSearchIndex) {
          * @param {FunctionType} fnType
          * @param {QueryElement} queryElem
          * @param {[FunctionType]} whereClause - Trait bounds for generic items.
-         * @param {Map<number,number>|null} mgensIn - Map functions generics to query generics.
+         * @param {Map<number,number>|null} mgensInout - Map functions generics to query generics.
+         *                                               Written on success.
          * @returns {boolean|FunctionType[]}
          */
-        function unifyFunctionTypeCheckBindings(fnType, queryElem, whereClause, mgensIn) {
+        function unifyFunctionTypeCheckBindings(fnType, queryElem, whereClause, mgensInout) {
             // Simplify generics now
             let simplifiedGenerics = fnType.generics;
             if (!simplifiedGenerics) {
@@ -1738,17 +1740,24 @@ function initSearch(rawSearchIndex) {
                 return false;
             }
             if (fnType.bindings.size > 0) {
+                const mgensResults = new Map(mgensInout);
                 for (const [name, constraints] of queryElem.bindings.entries()) {
                     if (!fnType.bindings.has(name)) {
                         return false;
                     }
                     // Since both items must have exactly one entry per name,
-                    // we don't need to backtrack here.
+                    // we don't need to backtrack here, but do need to write mgens.
                     if (!unifyFunctionTypes(
                         fnType.bindings.get(name),
                         constraints,
                         whereClause,
-                        mgensIn
+                        mgensResults,
+                        mgens => {
+                            for (const [fid, qid] of mgens.entries()) {
+                                mgensResults.set(fid, qid);
+                            }
+                            return true;
+                        }
                     )) {
                         return false;
                     }
@@ -1766,6 +1775,11 @@ function initSearch(rawSearchIndex) {
                 } else {
                     simplifiedGenerics = binds;
                 }
+                if (mgensInout) {
+                    for (const [fid, qid] of mgensResults.entries()) {
+                        mgensInout.set(fid, qid);
+                    }
+                }
             }
             return simplifiedGenerics;
         }

tests/rustdoc-js/assoc-type-backtrack.js

@@ -0,0 +1,66 @@
+// exact-check
+
+const EXPECTED = [
+    {
+        'query': 'mytrait, mytrait2 -> T',
+        'correction': null,
+        'others': [
+            { 'path': 'assoc_type_backtrack::MyTrait', 'name': 'fold' },
+            { 'path': 'assoc_type_backtrack::Cloned', 'name': 'fold' },
+        ],
+    },
+    {
+        'query': 'mytrait<U>, mytrait2 -> T',
+        'correction': null,
+        'others': [
+            { 'path': 'assoc_type_backtrack::MyTrait', 'name': 'fold' },
+            { 'path': 'assoc_type_backtrack::Cloned', 'name': 'fold' },
+        ],
+    },
+    {
+        'query': 'mytrait<Item=U>, mytrait2 -> T',
+        'correction': null,
+        'others': [
+            { 'path': 'assoc_type_backtrack::MyTrait', 'name': 'fold' },
+            { 'path': 'assoc_type_backtrack::Cloned', 'name': 'fold' },
+        ],
+    },
+    {
+        'query': 'mytrait<T>, mytrait2 -> T',
+        'correction': null,
+        'others': [],
+    },
+    {
+        'query': 'mytrait<Item=T>, mytrait2 -> T',
+        'correction': null,
+        'others': [],
+    },
+    {
+        'query': 'mytrait<T> -> Option<T>',
+        'correction': null,
+        'others': [
+            { 'path': 'assoc_type_backtrack::MyTrait', 'name': 'next' },
+        ],
+    },
+    {
+        'query': 'mytrait<Item=T> -> Option<T>',
+        'correction': null,
+        'others': [
+            { 'path': 'assoc_type_backtrack::MyTrait', 'name': 'next' },
+        ],
+    },
+    {
+        'query': 'mytrait<U> -> Option<T>',
+        'correction': null,
+        'others': [
+            { 'path': 'assoc_type_backtrack::Cloned', 'name': 'next' },
+        ],
+    },
+    {
+        'query': 'mytrait<Item=U> -> Option<T>',
+        'correction': null,
+        'others': [
+            { 'path': 'assoc_type_backtrack::Cloned', 'name': 'next' },
+        ],
+    },
+];

tests/rustdoc-js/assoc-type-backtrack.rs

@@ -0,0 +1,27 @@
+pub trait MyTrait2<X> {
+    type Output;
+}
+
+pub trait MyTrait {
+    type Item;
+    fn next(&mut self) -> Option<Self::Item>;
+    fn fold<B, F>(self, init: B, f: F) -> B where
+        Self: Sized,
+        F: MyTrait2<(B, Self::Item), Output=B>;
+}
+
+pub struct Cloned<I>(I);
+
+impl<'a, T, I> MyTrait for Cloned<I> where
+    T: 'a + Clone,
+    I: MyTrait<Item = &'a T>
+{
+    type Item = T;
+    fn next(&mut self) -> Option<Self::Item> { loop {} }
+    fn fold<B, F>(self, init: B, f: F) -> B where
+        Self: Sized,
+        F: MyTrait2<(B, Self::Item), Output=B>
+    {
+        loop {}
+    }
+}