From f4dcf881dc82e0492049a792715926ace90d73f2 Mon Sep 17 00:00:00 2001
From: Anders Hejlsberg <andersh@microsoft.com>
Date: Fri, 18 Feb 2022 07:06:55 -0800
Subject: [PATCH] Add regression test

---
 tests/baselines/reference/correlatedUnions.js | 53 +++++++++++++
 .../reference/correlatedUnions.symbols        | 78 +++++++++++++++++++
 .../reference/correlatedUnions.types          | 71 +++++++++++++++++
 tests/cases/compiler/correlatedUnions.ts      | 28 +++++++
 4 files changed, 230 insertions(+)

diff --git a/tests/baselines/reference/correlatedUnions.js b/tests/baselines/reference/correlatedUnions.js
index b42a48c68a0e2..f1e13f4417030 100644
--- a/tests/baselines/reference/correlatedUnions.js
+++ b/tests/baselines/reference/correlatedUnions.js
@@ -181,6 +181,34 @@ function f3<K extends keyof ArgMap>(funcs: Funcs, key: K, arg: ArgMap[K]) {
 function f4<K extends keyof ArgMap>(x: Funcs[keyof ArgMap], y: Funcs[K]) {
     x = y;
 }
+
+// Repro from #47890
+
+interface MyObj {
+    someKey: {
+      name: string;
+    }
+    someOtherKey: {
+      name: number;
+    }
+}
+
+const ref: MyObj = {
+    someKey: { name: "" },
+    someOtherKey: { name: 42 }
+};
+
+function func<K extends keyof MyObj>(k: K): MyObj[K]['name'] | undefined {
+    const myObj: Partial<MyObj>[K] = ref[k];
+    if (myObj) {
+      return myObj.name;
+    }
+    const myObj2: Partial<MyObj>[keyof MyObj] = ref[k];
+    if (myObj2) {
+      return myObj2.name;
+    }
+    return undefined;
+}
 
 
 //// [correlatedUnions.js]
@@ -282,6 +310,21 @@ function f3(funcs, key, arg) {
 function f4(x, y) {
     x = y;
 }
+var ref = {
+    someKey: { name: "" },
+    someOtherKey: { name: 42 }
+};
+function func(k) {
+    var myObj = ref[k];
+    if (myObj) {
+        return myObj.name;
+    }
+    var myObj2 = ref[k];
+    if (myObj2) {
+        return myObj2.name;
+    }
+    return undefined;
+}
 
 
 //// [correlatedUnions.d.ts]
@@ -398,3 +441,13 @@ declare function f1<K extends keyof ArgMap>(funcs: Funcs, key: K, arg: ArgMap[K]
 declare function f2<K extends keyof ArgMap>(funcs: Funcs, key: K, arg: ArgMap[K]): void;
 declare function f3<K extends keyof ArgMap>(funcs: Funcs, key: K, arg: ArgMap[K]): void;
 declare function f4<K extends keyof ArgMap>(x: Funcs[keyof ArgMap], y: Funcs[K]): void;
+interface MyObj {
+    someKey: {
+        name: string;
+    };
+    someOtherKey: {
+        name: number;
+    };
+}
+declare const ref: MyObj;
+declare function func<K extends keyof MyObj>(k: K): MyObj[K]['name'] | undefined;
diff --git a/tests/baselines/reference/correlatedUnions.symbols b/tests/baselines/reference/correlatedUnions.symbols
index 040c3983e95dd..16fa17e1a4f0e 100644
--- a/tests/baselines/reference/correlatedUnions.symbols
+++ b/tests/baselines/reference/correlatedUnions.symbols
@@ -675,3 +675,81 @@ function f4<K extends keyof ArgMap>(x: Funcs[keyof ArgMap], y: Funcs[K]) {
 >y : Symbol(y, Decl(correlatedUnions.ts, 179, 59))
 }
 
+// Repro from #47890
+
+interface MyObj {
+>MyObj : Symbol(MyObj, Decl(correlatedUnions.ts, 181, 1))
+
+    someKey: {
+>someKey : Symbol(MyObj.someKey, Decl(correlatedUnions.ts, 185, 17))
+
+      name: string;
+>name : Symbol(name, Decl(correlatedUnions.ts, 186, 14))
+    }
+    someOtherKey: {
+>someOtherKey : Symbol(MyObj.someOtherKey, Decl(correlatedUnions.ts, 188, 5))
+
+      name: number;
+>name : Symbol(name, Decl(correlatedUnions.ts, 189, 19))
+    }
+}
+
+const ref: MyObj = {
+>ref : Symbol(ref, Decl(correlatedUnions.ts, 194, 5))
+>MyObj : Symbol(MyObj, Decl(correlatedUnions.ts, 181, 1))
+
+    someKey: { name: "" },
+>someKey : Symbol(someKey, Decl(correlatedUnions.ts, 194, 20))
+>name : Symbol(name, Decl(correlatedUnions.ts, 195, 14))
+
+    someOtherKey: { name: 42 }
+>someOtherKey : Symbol(someOtherKey, Decl(correlatedUnions.ts, 195, 26))
+>name : Symbol(name, Decl(correlatedUnions.ts, 196, 19))
+
+};
+
+function func<K extends keyof MyObj>(k: K): MyObj[K]['name'] | undefined {
+>func : Symbol(func, Decl(correlatedUnions.ts, 197, 2))
+>K : Symbol(K, Decl(correlatedUnions.ts, 199, 14))
+>MyObj : Symbol(MyObj, Decl(correlatedUnions.ts, 181, 1))
+>k : Symbol(k, Decl(correlatedUnions.ts, 199, 37))
+>K : Symbol(K, Decl(correlatedUnions.ts, 199, 14))
+>MyObj : Symbol(MyObj, Decl(correlatedUnions.ts, 181, 1))
+>K : Symbol(K, Decl(correlatedUnions.ts, 199, 14))
+
+    const myObj: Partial<MyObj>[K] = ref[k];
+>myObj : Symbol(myObj, Decl(correlatedUnions.ts, 200, 9))
+>Partial : Symbol(Partial, Decl(lib.es5.d.ts, --, --))
+>MyObj : Symbol(MyObj, Decl(correlatedUnions.ts, 181, 1))
+>K : Symbol(K, Decl(correlatedUnions.ts, 199, 14))
+>ref : Symbol(ref, Decl(correlatedUnions.ts, 194, 5))
+>k : Symbol(k, Decl(correlatedUnions.ts, 199, 37))
+
+    if (myObj) {
+>myObj : Symbol(myObj, Decl(correlatedUnions.ts, 200, 9))
+
+      return myObj.name;
+>myObj.name : Symbol(name, Decl(correlatedUnions.ts, 186, 14), Decl(correlatedUnions.ts, 189, 19))
+>myObj : Symbol(myObj, Decl(correlatedUnions.ts, 200, 9))
+>name : Symbol(name, Decl(correlatedUnions.ts, 186, 14), Decl(correlatedUnions.ts, 189, 19))
+    }
+    const myObj2: Partial<MyObj>[keyof MyObj] = ref[k];
+>myObj2 : Symbol(myObj2, Decl(correlatedUnions.ts, 204, 9))
+>Partial : Symbol(Partial, Decl(lib.es5.d.ts, --, --))
+>MyObj : Symbol(MyObj, Decl(correlatedUnions.ts, 181, 1))
+>MyObj : Symbol(MyObj, Decl(correlatedUnions.ts, 181, 1))
+>ref : Symbol(ref, Decl(correlatedUnions.ts, 194, 5))
+>k : Symbol(k, Decl(correlatedUnions.ts, 199, 37))
+
+    if (myObj2) {
+>myObj2 : Symbol(myObj2, Decl(correlatedUnions.ts, 204, 9))
+
+      return myObj2.name;
+>myObj2.name : Symbol(name, Decl(correlatedUnions.ts, 186, 14), Decl(correlatedUnions.ts, 189, 19))
+>myObj2 : Symbol(myObj2, Decl(correlatedUnions.ts, 204, 9))
+>name : Symbol(name, Decl(correlatedUnions.ts, 186, 14), Decl(correlatedUnions.ts, 189, 19))
+    }
+    return undefined;
+>undefined : Symbol(undefined)
+}
+
diff --git a/tests/baselines/reference/correlatedUnions.types b/tests/baselines/reference/correlatedUnions.types
index ae14133757619..3a4d950070704 100644
--- a/tests/baselines/reference/correlatedUnions.types
+++ b/tests/baselines/reference/correlatedUnions.types
@@ -624,3 +624,74 @@ function f4<K extends keyof ArgMap>(x: Funcs[keyof ArgMap], y: Funcs[K]) {
 >y : Funcs[K]
 }
 
+// Repro from #47890
+
+interface MyObj {
+    someKey: {
+>someKey : { name: string; }
+
+      name: string;
+>name : string
+    }
+    someOtherKey: {
+>someOtherKey : { name: number; }
+
+      name: number;
+>name : number
+    }
+}
+
+const ref: MyObj = {
+>ref : MyObj
+>{    someKey: { name: "" },    someOtherKey: { name: 42 }} : { someKey: { name: string; }; someOtherKey: { name: number; }; }
+
+    someKey: { name: "" },
+>someKey : { name: string; }
+>{ name: "" } : { name: string; }
+>name : string
+>"" : ""
+
+    someOtherKey: { name: 42 }
+>someOtherKey : { name: number; }
+>{ name: 42 } : { name: number; }
+>name : number
+>42 : 42
+
+};
+
+function func<K extends keyof MyObj>(k: K): MyObj[K]['name'] | undefined {
+>func : <K extends keyof MyObj>(k: K) => MyObj[K]['name'] | undefined
+>k : K
+
+    const myObj: Partial<MyObj>[K] = ref[k];
+>myObj : Partial<MyObj>[K]
+>ref[k] : MyObj[K]
+>ref : MyObj
+>k : K
+
+    if (myObj) {
+>myObj : Partial<MyObj>[K]
+
+      return myObj.name;
+>myObj.name : string | number
+>myObj : { name: string; } | { name: number; }
+>name : string | number
+    }
+    const myObj2: Partial<MyObj>[keyof MyObj] = ref[k];
+>myObj2 : { name: string; } | { name: number; } | undefined
+>ref[k] : { name: string; } | { name: number; }
+>ref : MyObj
+>k : K
+
+    if (myObj2) {
+>myObj2 : { name: string; } | { name: number; }
+
+      return myObj2.name;
+>myObj2.name : string | number
+>myObj2 : { name: string; } | { name: number; }
+>name : string | number
+    }
+    return undefined;
+>undefined : undefined
+}
+
diff --git a/tests/cases/compiler/correlatedUnions.ts b/tests/cases/compiler/correlatedUnions.ts
index 546d511034bae..f6b4086f03f5a 100644
--- a/tests/cases/compiler/correlatedUnions.ts
+++ b/tests/cases/compiler/correlatedUnions.ts
@@ -183,3 +183,31 @@ function f3<K extends keyof ArgMap>(funcs: Funcs, key: K, arg: ArgMap[K]) {
 function f4<K extends keyof ArgMap>(x: Funcs[keyof ArgMap], y: Funcs[K]) {
     x = y;
 }
+
+// Repro from #47890
+
+interface MyObj {
+    someKey: {
+      name: string;
+    }
+    someOtherKey: {
+      name: number;
+    }
+}
+
+const ref: MyObj = {
+    someKey: { name: "" },
+    someOtherKey: { name: 42 }
+};
+
+function func<K extends keyof MyObj>(k: K): MyObj[K]['name'] | undefined {
+    const myObj: Partial<MyObj>[K] = ref[k];
+    if (myObj) {
+      return myObj.name;
+    }
+    const myObj2: Partial<MyObj>[keyof MyObj] = ref[k];
+    if (myObj2) {
+      return myObj2.name;
+    }
+    return undefined;
+}