From 684b03983540b04755b9f21ef206dc87b2b06858 Mon Sep 17 00:00:00 2001
From: Andrew Branch <andrew@wheream.io>
Date: Mon, 15 Mar 2021 14:37:59 -0700
Subject: [PATCH] Types that extend Array or ReadonlyArray are automatically
 array-like

---
 src/compiler/checker.ts                       |  8 +++++-
 .../reference/excessiveStackDepthFlatArray.js | 19 ++++++++++++++
 .../excessiveStackDepthFlatArray.symbols      | 26 +++++++++++++++++++
 .../excessiveStackDepthFlatArray.types        | 23 ++++++++++++++++
 .../compiler/excessiveStackDepthFlatArray.ts  |  9 +++++++
 5 files changed, 84 insertions(+), 1 deletion(-)
 create mode 100644 tests/baselines/reference/excessiveStackDepthFlatArray.js
 create mode 100644 tests/baselines/reference/excessiveStackDepthFlatArray.symbols
 create mode 100644 tests/baselines/reference/excessiveStackDepthFlatArray.types
 create mode 100644 tests/cases/compiler/excessiveStackDepthFlatArray.ts

diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 625cfabd99b..a5260871b52 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -19703,7 +19703,13 @@ namespace ts {
         function isArrayLikeType(type: Type): boolean {
             // A type is array-like if it is a reference to the global Array or global ReadonlyArray type,
             // or if it is not the undefined or null type and if it is assignable to ReadonlyArray<any>
-            return isArrayType(type) || !(type.flags & TypeFlags.Nullable) && isTypeAssignableTo(type, anyReadonlyArrayType);
+            return isArrayType(type) || hasArrayOrReadonlyArrayBaseType(type) || !(type.flags & TypeFlags.Nullable) && isTypeAssignableTo(type, anyReadonlyArrayType);
+        }
+
+        function hasArrayOrReadonlyArrayBaseType(type: Type): boolean {
+            return !!(getObjectFlags(type) & ObjectFlags.Reference)
+                && !!(getObjectFlags((type as TypeReference).target) & ObjectFlags.ClassOrInterface)
+                && some(getBaseTypes((type as TypeReference).target as InterfaceType), isArrayType);
         }
 
         function isEmptyArrayLiteralType(type: Type): boolean {
diff --git a/tests/baselines/reference/excessiveStackDepthFlatArray.js b/tests/baselines/reference/excessiveStackDepthFlatArray.js
new file mode 100644
index 00000000000..a8e70171466
--- /dev/null
+++ b/tests/baselines/reference/excessiveStackDepthFlatArray.js
@@ -0,0 +1,19 @@
+//// [excessiveStackDepthFlatArray.ts]
+interface MiddlewareArray<T> extends Array<T> {}
+declare function configureStore(options: { middleware: MiddlewareArray<any> }): void;
+
+declare const defaultMiddleware: MiddlewareArray<any>;
+configureStore({
+  middleware: [...defaultMiddleware], // Should not error
+});
+
+
+//// [excessiveStackDepthFlatArray.js]
+var __spreadArray = (this && this.__spreadArray) || function (to, from) {
+    for (var i = 0, il = from.length, j = to.length; i < il; i++, j++)
+        to[j] = from[i];
+    return to;
+};
+configureStore({
+    middleware: __spreadArray([], defaultMiddleware)
+});
diff --git a/tests/baselines/reference/excessiveStackDepthFlatArray.symbols b/tests/baselines/reference/excessiveStackDepthFlatArray.symbols
new file mode 100644
index 00000000000..9d05616763f
--- /dev/null
+++ b/tests/baselines/reference/excessiveStackDepthFlatArray.symbols
@@ -0,0 +1,26 @@
+=== tests/cases/compiler/excessiveStackDepthFlatArray.ts ===
+interface MiddlewareArray<T> extends Array<T> {}
+>MiddlewareArray : Symbol(MiddlewareArray, Decl(excessiveStackDepthFlatArray.ts, 0, 0))
+>T : Symbol(T, Decl(excessiveStackDepthFlatArray.ts, 0, 26))
+>Array : Symbol(Array, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --), Decl(lib.es2015.core.d.ts, --, --), Decl(lib.es2015.iterable.d.ts, --, --), Decl(lib.es2015.symbol.wellknown.d.ts, --, --) ... and 2 more)
+>T : Symbol(T, Decl(excessiveStackDepthFlatArray.ts, 0, 26))
+
+declare function configureStore(options: { middleware: MiddlewareArray<any> }): void;
+>configureStore : Symbol(configureStore, Decl(excessiveStackDepthFlatArray.ts, 0, 48))
+>options : Symbol(options, Decl(excessiveStackDepthFlatArray.ts, 1, 32))
+>middleware : Symbol(middleware, Decl(excessiveStackDepthFlatArray.ts, 1, 42))
+>MiddlewareArray : Symbol(MiddlewareArray, Decl(excessiveStackDepthFlatArray.ts, 0, 0))
+
+declare const defaultMiddleware: MiddlewareArray<any>;
+>defaultMiddleware : Symbol(defaultMiddleware, Decl(excessiveStackDepthFlatArray.ts, 3, 13))
+>MiddlewareArray : Symbol(MiddlewareArray, Decl(excessiveStackDepthFlatArray.ts, 0, 0))
+
+configureStore({
+>configureStore : Symbol(configureStore, Decl(excessiveStackDepthFlatArray.ts, 0, 48))
+
+  middleware: [...defaultMiddleware], // Should not error
+>middleware : Symbol(middleware, Decl(excessiveStackDepthFlatArray.ts, 4, 16))
+>defaultMiddleware : Symbol(defaultMiddleware, Decl(excessiveStackDepthFlatArray.ts, 3, 13))
+
+});
+
diff --git a/tests/baselines/reference/excessiveStackDepthFlatArray.types b/tests/baselines/reference/excessiveStackDepthFlatArray.types
new file mode 100644
index 00000000000..ad02a8e74b6
--- /dev/null
+++ b/tests/baselines/reference/excessiveStackDepthFlatArray.types
@@ -0,0 +1,23 @@
+=== tests/cases/compiler/excessiveStackDepthFlatArray.ts ===
+interface MiddlewareArray<T> extends Array<T> {}
+declare function configureStore(options: { middleware: MiddlewareArray<any> }): void;
+>configureStore : (options: {    middleware: MiddlewareArray<any>;}) => void
+>options : { middleware: MiddlewareArray<any>; }
+>middleware : MiddlewareArray<any>
+
+declare const defaultMiddleware: MiddlewareArray<any>;
+>defaultMiddleware : MiddlewareArray<any>
+
+configureStore({
+>configureStore({  middleware: [...defaultMiddleware], // Should not error}) : void
+>configureStore : (options: { middleware: MiddlewareArray<any>; }) => void
+>{  middleware: [...defaultMiddleware], // Should not error} : { middleware: any[]; }
+
+  middleware: [...defaultMiddleware], // Should not error
+>middleware : any[]
+>[...defaultMiddleware] : any[]
+>...defaultMiddleware : any
+>defaultMiddleware : MiddlewareArray<any>
+
+});
+
diff --git a/tests/cases/compiler/excessiveStackDepthFlatArray.ts b/tests/cases/compiler/excessiveStackDepthFlatArray.ts
new file mode 100644
index 00000000000..fd16b622199
--- /dev/null
+++ b/tests/cases/compiler/excessiveStackDepthFlatArray.ts
@@ -0,0 +1,9 @@
+// @lib: es2019
+
+interface MiddlewareArray<T> extends Array<T> {}
+declare function configureStore(options: { middleware: MiddlewareArray<any> }): void;
+
+declare const defaultMiddleware: MiddlewareArray<any>;
+configureStore({
+  middleware: [...defaultMiddleware], // Should not error
+});