From 99c5c096c5895aaec570dbe6a68094bd1b958bff Mon Sep 17 00:00:00 2001
From: Anders Hejlsberg <andersh@microsoft.com>
Date: Thu, 7 May 2020 11:08:02 -0700
Subject: [PATCH] Properly finalize evolving array type in getTypeAtFlowCall

---
 src/compiler/checker.ts | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 0872ee38e2b..e60afaeca66 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -20360,7 +20360,7 @@ namespace ts {
                     const predicate = getTypePredicateOfSignature(signature);
                     if (predicate && (predicate.kind === TypePredicateKind.AssertsThis || predicate.kind === TypePredicateKind.AssertsIdentifier)) {
                         const flowType = getTypeAtFlowNode(flow.antecedent);
-                        const type = getTypeFromFlowType(flowType);
+                        const type = finalizeEvolvingArrayType(getTypeFromFlowType(flowType));
                         const narrowedType = predicate.type ? narrowTypeByTypePredicate(type, predicate, flow.node, /*assumeTrue*/ true) :
                             predicate.kind === TypePredicateKind.AssertsIdentifier && predicate.parameterIndex >= 0 && predicate.parameterIndex < flow.node.arguments.length ? narrowTypeByAssertion(type, flow.node.arguments[predicate.parameterIndex]) :
                             type;