From 6e6fbdabb1d5184f5e63d04d87c32a55c4e703d0 Mon Sep 17 00:00:00 2001
From: Daniel Rosenwasser <DanielRosenwasser@users.noreply.github.com>
Date: Thu, 1 Jul 2021 23:36:34 +0000
Subject: [PATCH] Avoid doing subtype reduction on arrays when contextually
 typed by array types.

---
 src/compiler/checker.ts | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 761ca7a95ec..545282638ed 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -26175,8 +26175,9 @@ namespace ts {
             if (forceTuple || inConstContext || contextualType && someType(contextualType, isTupleLikeType)) {
                 return createArrayLiteralType(createTupleType(elementTypes, elementFlags, /*readonly*/ inConstContext));
             }
+            const unionReductionStrategy = contextualType && isArrayType(contextualType) ? UnionReduction.None : UnionReduction.Subtype;
             return createArrayLiteralType(createArrayType(elementTypes.length ?
-                getUnionType(sameMap(elementTypes, (t, i) => elementFlags[i] & ElementFlags.Variadic ? getIndexedAccessTypeOrUndefined(t, numberType) || anyType : t), UnionReduction.Subtype) :
+                getUnionType(sameMap(elementTypes, (t, i) => elementFlags[i] & ElementFlags.Variadic ? getIndexedAccessTypeOrUndefined(t, numberType) || anyType : t), unionReductionStrategy) :
                 strictNullChecks ? implicitNeverType : undefinedWideningType, inConstContext));
         }