Defer distributing index over generic object types

Author: Andarist

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]

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))
+
+};
+

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]>;
+};
+

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]>;
+};