From 53019064cba5f1fbde6b5d2f80712be2a7e5c4f5 Mon Sep 17 00:00:00 2001
From: Jake Bailey <5341706+jakebailey@users.noreply.github.com>
Date: Sun, 19 Mar 2023 11:22:08 -0700
Subject: [PATCH 1/2] Don't recalculate undefined in
 getConstraintOfDistributiveConditionalType

---
 src/compiler/checker.ts | 6 ++++++
 src/compiler/types.ts   | 2 ++
 2 files changed, 8 insertions(+)

diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index cc64670dd993c..6e93cf5d1d905 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -13594,6 +13594,10 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
     }
 
     function getConstraintOfDistributiveConditionalType(type: ConditionalType): Type | undefined {
+        if (type.resolvedDefaultConstraintOfDistributed !== undefined) {
+            return type.resolvedDefaultConstraintOfDistributed || undefined;
+        }
+
         // Check if we have a conditional type of the form 'T extends U ? X : Y', where T is a constrained
         // type parameter. If so, create an instantiation of the conditional type where T is replaced
         // with its constraint. We do this because if the constraint is a union type it will be distributed
@@ -13611,10 +13615,12 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
             if (constraint && constraint !== type.checkType) {
                 const instantiated = getConditionalTypeInstantiation(type, prependTypeMapping(type.root.checkType, constraint, type.mapper));
                 if (!(instantiated.flags & TypeFlags.Never)) {
+                    type.resolvedDefaultConstraintOfDistributed = instantiated;
                     return instantiated;
                 }
             }
         }
+        type.resolvedDefaultConstraintOfDistributed = false;
         return undefined;
     }
 
diff --git a/src/compiler/types.ts b/src/compiler/types.ts
index d8234398128ef..016403f36442c 100644
--- a/src/compiler/types.ts
+++ b/src/compiler/types.ts
@@ -6630,6 +6630,8 @@ export interface ConditionalType extends InstantiableType {
     /** @internal */
     resolvedDefaultConstraint?: Type;
     /** @internal */
+    resolvedDefaultConstraintOfDistributed?: Type | false;
+    /** @internal */
     mapper?: TypeMapper;
     /** @internal */
     combinedMapper?: TypeMapper;

From c92c51d2a10bfc119630f6214646f9c53a3d72a1 Mon Sep 17 00:00:00 2001
From: Jake Bailey <5341706+jakebailey@users.noreply.github.com>
Date: Mon, 27 Mar 2023 13:09:14 -0700
Subject: [PATCH 2/2] Rename to resolvedConstraintOfDistributive

---
 src/compiler/checker.ts | 8 ++++----
 src/compiler/types.ts   | 2 +-
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index ca3aa287682c9..d87983beae947 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -13605,8 +13605,8 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
     }
 
     function getConstraintOfDistributiveConditionalType(type: ConditionalType): Type | undefined {
-        if (type.resolvedDefaultConstraintOfDistributed !== undefined) {
-            return type.resolvedDefaultConstraintOfDistributed || undefined;
+        if (type.resolvedConstraintOfDistributive !== undefined) {
+            return type.resolvedConstraintOfDistributive || undefined;
         }
 
         // Check if we have a conditional type of the form 'T extends U ? X : Y', where T is a constrained
@@ -13626,12 +13626,12 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
             if (constraint && constraint !== type.checkType) {
                 const instantiated = getConditionalTypeInstantiation(type, prependTypeMapping(type.root.checkType, constraint, type.mapper));
                 if (!(instantiated.flags & TypeFlags.Never)) {
-                    type.resolvedDefaultConstraintOfDistributed = instantiated;
+                    type.resolvedConstraintOfDistributive = instantiated;
                     return instantiated;
                 }
             }
         }
-        type.resolvedDefaultConstraintOfDistributed = false;
+        type.resolvedConstraintOfDistributive = false;
         return undefined;
     }
 
diff --git a/src/compiler/types.ts b/src/compiler/types.ts
index 92d4fccdcb45b..7e14ff22dede6 100644
--- a/src/compiler/types.ts
+++ b/src/compiler/types.ts
@@ -6645,7 +6645,7 @@ export interface ConditionalType extends InstantiableType {
     /** @internal */
     resolvedDefaultConstraint?: Type;
     /** @internal */
-    resolvedDefaultConstraintOfDistributed?: Type | false;
+    resolvedConstraintOfDistributive?: Type | false;
     /** @internal */
     mapper?: TypeMapper;
     /** @internal */