From 00e3926c48c050b4e859072f58e6189d05593054 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Mateusz=20Burzy=C5=84ski?= <mateuszburzynski@gmail.com>
Date: Tue, 30 Aug 2022 17:55:17 +0200
Subject: [PATCH] Defer distributing index over generic object types

---
 src/compiler/checker.ts                       |  3 ++
 ...tWithIndexSignatureWithNonNullable.symbols | 39 +++++++++++++++++++
 ...intWithIndexSignatureWithNonNullable.types | 24 ++++++++++++
 ...traintWithIndexSignatureWithNonNullable.ts | 16 ++++++++
 4 files changed, 82 insertions(+)
 create mode 100644 tests/baselines/reference/mappedTypeOverNullableConstraintWithIndexSignatureWithNonNullable.symbols
 create mode 100644 tests/baselines/reference/mappedTypeOverNullableConstraintWithIndexSignatureWithNonNullable.types
 create mode 100644 tests/cases/compiler/mappedTypeOverNullableConstraintWithIndexSignatureWithNonNullable.ts

diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 01fc87bae36a4..70daadb092357 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -15903,6 +15903,9 @@ namespace ts {
         }
 
         function distributeIndexOverObjectType(objectType: Type, indexType: Type, writing: boolean) {
+            if (shouldDeferIndexType(objectType)) {
+                return;
+            }
             // (T | U)[K] -> T[K] | U[K] (reading)
             // (T | U)[K] -> T[K] & U[K] (writing)
             // (T & U)[K] -> T[K] & U[K]
diff --git a/tests/baselines/reference/mappedTypeOverNullableConstraintWithIndexSignatureWithNonNullable.symbols b/tests/baselines/reference/mappedTypeOverNullableConstraintWithIndexSignatureWithNonNullable.symbols
new file mode 100644
index 0000000000000..c94bc76ef60a3
--- /dev/null
+++ b/tests/baselines/reference/mappedTypeOverNullableConstraintWithIndexSignatureWithNonNullable.symbols
@@ -0,0 +1,39 @@
+=== tests/cases/compiler/mappedTypeOverNullableConstraintWithIndexSignatureWithNonNullable.ts ===
+interface StateSchema {
+>StateSchema : Symbol(StateSchema, Decl(mappedTypeOverNullableConstraintWithIndexSignatureWithNonNullable.ts, 0, 0))
+
+  states?: {
+>states : Symbol(StateSchema.states, Decl(mappedTypeOverNullableConstraintWithIndexSignatureWithNonNullable.ts, 0, 23))
+
+    [key: string]: StateSchema;
+>key : Symbol(key, Decl(mappedTypeOverNullableConstraintWithIndexSignatureWithNonNullable.ts, 2, 5))
+>StateSchema : Symbol(StateSchema, Decl(mappedTypeOverNullableConstraintWithIndexSignatureWithNonNullable.ts, 0, 0))
+
+  };
+}
+
+declare class StateNode<TStateSchema extends StateSchema> {
+>StateNode : Symbol(StateNode, Decl(mappedTypeOverNullableConstraintWithIndexSignatureWithNonNullable.ts, 4, 1))
+>TStateSchema : Symbol(TStateSchema, Decl(mappedTypeOverNullableConstraintWithIndexSignatureWithNonNullable.ts, 6, 24))
+>StateSchema : Symbol(StateSchema, Decl(mappedTypeOverNullableConstraintWithIndexSignatureWithNonNullable.ts, 0, 0))
+
+  schema: TStateSchema;
+>schema : Symbol(StateNode.schema, Decl(mappedTypeOverNullableConstraintWithIndexSignatureWithNonNullable.ts, 6, 59))
+>TStateSchema : Symbol(TStateSchema, Decl(mappedTypeOverNullableConstraintWithIndexSignatureWithNonNullable.ts, 6, 24))
+}
+
+type StateNodesConfig<TStateSchema extends StateSchema> = {
+>StateNodesConfig : Symbol(StateNodesConfig, Decl(mappedTypeOverNullableConstraintWithIndexSignatureWithNonNullable.ts, 8, 1))
+>TStateSchema : Symbol(TStateSchema, Decl(mappedTypeOverNullableConstraintWithIndexSignatureWithNonNullable.ts, 10, 22))
+>StateSchema : Symbol(StateSchema, Decl(mappedTypeOverNullableConstraintWithIndexSignatureWithNonNullable.ts, 0, 0))
+
+  [K in keyof TStateSchema["states"]]: StateNode<NonNullable<TStateSchema["states"]>[K]>;
+>K : Symbol(K, Decl(mappedTypeOverNullableConstraintWithIndexSignatureWithNonNullable.ts, 11, 3))
+>TStateSchema : Symbol(TStateSchema, Decl(mappedTypeOverNullableConstraintWithIndexSignatureWithNonNullable.ts, 10, 22))
+>StateNode : Symbol(StateNode, Decl(mappedTypeOverNullableConstraintWithIndexSignatureWithNonNullable.ts, 4, 1))
+>NonNullable : Symbol(NonNullable, Decl(lib.es5.d.ts, --, --))
+>TStateSchema : Symbol(TStateSchema, Decl(mappedTypeOverNullableConstraintWithIndexSignatureWithNonNullable.ts, 10, 22))
+>K : Symbol(K, Decl(mappedTypeOverNullableConstraintWithIndexSignatureWithNonNullable.ts, 11, 3))
+
+};
+
diff --git a/tests/baselines/reference/mappedTypeOverNullableConstraintWithIndexSignatureWithNonNullable.types b/tests/baselines/reference/mappedTypeOverNullableConstraintWithIndexSignatureWithNonNullable.types
new file mode 100644
index 0000000000000..324becfe6b1cf
--- /dev/null
+++ b/tests/baselines/reference/mappedTypeOverNullableConstraintWithIndexSignatureWithNonNullable.types
@@ -0,0 +1,24 @@
+=== tests/cases/compiler/mappedTypeOverNullableConstraintWithIndexSignatureWithNonNullable.ts ===
+interface StateSchema {
+  states?: {
+>states : { [key: string]: StateSchema; } | undefined
+
+    [key: string]: StateSchema;
+>key : string
+
+  };
+}
+
+declare class StateNode<TStateSchema extends StateSchema> {
+>StateNode : StateNode<TStateSchema>
+
+  schema: TStateSchema;
+>schema : TStateSchema
+}
+
+type StateNodesConfig<TStateSchema extends StateSchema> = {
+>StateNodesConfig : StateNodesConfig<TStateSchema>
+
+  [K in keyof TStateSchema["states"]]: StateNode<NonNullable<TStateSchema["states"]>[K]>;
+};
+
diff --git a/tests/cases/compiler/mappedTypeOverNullableConstraintWithIndexSignatureWithNonNullable.ts b/tests/cases/compiler/mappedTypeOverNullableConstraintWithIndexSignatureWithNonNullable.ts
new file mode 100644
index 0000000000000..025170356f969
--- /dev/null
+++ b/tests/cases/compiler/mappedTypeOverNullableConstraintWithIndexSignatureWithNonNullable.ts
@@ -0,0 +1,16 @@
+// @noEmit: true
+// @strict: true
+
+interface StateSchema {
+  states?: {
+    [key: string]: StateSchema;
+  };
+}
+
+declare class StateNode<TStateSchema extends StateSchema> {
+  schema: TStateSchema;
+}
+
+type StateNodesConfig<TStateSchema extends StateSchema> = {
+  [K in keyof TStateSchema["states"]]: StateNode<NonNullable<TStateSchema["states"]>[K]>;
+};