Merge pull request #7377 from Microsoft/port-7373-7163

Ports #7373 and #7163 in release-1.8

Author: vladima

src/compiler/checker.ts

@@ -6444,8 +6444,10 @@ namespace ts {
         function inferTypes(context: InferenceContext, source: Type, target: Type) {
             let sourceStack: Type[];
             let targetStack: Type[];
+            const maxDepth = 5;
             let depth = 0;
             let inferiority = 0;
+            const visited: Map<boolean> = {};
             inferFromTypes(source, target);
 
             function isInProcess(source: Type, target: Type) {
@@ -6571,10 +6573,21 @@ namespace ts {
                         if (isInProcess(source, target)) {
                             return;
                         }
+                        // we delibirately limit the depth we examine to infer types: this speeds up the overall inference process
+                        // and user rarely expects inferences to be made from the deeply nested constituents.
+                        if (depth > maxDepth) {
+                            return;
+                        }
                         if (isDeeplyNestedGeneric(source, sourceStack, depth) && isDeeplyNestedGeneric(target, targetStack, depth)) {
                             return;
                         }
 
+                        const key = source.id + "," + target.id;
+                        if (hasProperty(visited, key)) {
+                            return;
+                        }
+                        visited[key] = true;
+
                         if (depth === 0) {
                             sourceStack = [];
                             targetStack = [];