Merge pull request #7373 from Microsoft/limitInferenceDepth

set the maximum depth to explore during type inference

Author: vladima

src/compiler/checker.ts

@@ -6585,6 +6585,7 @@ 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> = {};
@@ -6713,6 +6714,11 @@ 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;
                         }