From 481882cfdae22e48702e33ef123eca52839cff74 Mon Sep 17 00:00:00 2001
From: Gabrielle <contact@gabriel-langer.ninja>
Date: Thu, 10 Feb 2022 22:32:18 +0100
Subject: [PATCH] Fixed incorrect substitution on index access on generic
 mapped type with key remapping

---
 src/compiler/checker.ts                       |  6 +++--
 ...cessOnGenericMappedTypeWithKeyRemapping.js |  9 +++++++
 ...nGenericMappedTypeWithKeyRemapping.symbols | 24 +++++++++++++++++++
 ...sOnGenericMappedTypeWithKeyRemapping.types | 16 +++++++++++++
 ...cessOnGenericMappedTypeWithKeyRemapping.ts |  4 ++++
 5 files changed, 57 insertions(+), 2 deletions(-)
 create mode 100644 tests/baselines/reference/indexAccessOnGenericMappedTypeWithKeyRemapping.js
 create mode 100644 tests/baselines/reference/indexAccessOnGenericMappedTypeWithKeyRemapping.symbols
 create mode 100644 tests/baselines/reference/indexAccessOnGenericMappedTypeWithKeyRemapping.types
 create mode 100644 tests/cases/compiler/indexAccessOnGenericMappedTypeWithKeyRemapping.ts

diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 2830de0c49d98..9e49166676102 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -15567,8 +15567,10 @@ namespace ts {
         }
 
         function substituteIndexedMappedType(objectType: MappedType, index: Type) {
-            const mapper = createTypeMapper([getTypeParameterFromMappedType(objectType)], [index]);
-            const templateMapper = combineTypeMappers(objectType.mapper, mapper);
+            let templateMapper = objectType.mapper;
+            if (!objectType.declaration.nameType) {
+                templateMapper = combineTypeMappers(templateMapper, createTypeMapper([getTypeParameterFromMappedType(objectType)], [index]));
+            }
             return instantiateType(getTemplateTypeFromMappedType(objectType), templateMapper);
         }
 
diff --git a/tests/baselines/reference/indexAccessOnGenericMappedTypeWithKeyRemapping.js b/tests/baselines/reference/indexAccessOnGenericMappedTypeWithKeyRemapping.js
new file mode 100644
index 0000000000000..be63ec884ac67
--- /dev/null
+++ b/tests/baselines/reference/indexAccessOnGenericMappedTypeWithKeyRemapping.js
@@ -0,0 +1,9 @@
+//// [indexAccessOnGenericMappedTypeWithKeyRemapping.ts]
+type Foo<T extends string> = {
+    [RemappedT in T as `get${RemappedT}`]: RemappedT;
+};
+const get = <T extends string>(t: T, foo: Foo<T>): T => foo[`get${t}`];
+
+
+//// [indexAccessOnGenericMappedTypeWithKeyRemapping.js]
+var get = function (t, foo) { return foo["get".concat(t)]; };
diff --git a/tests/baselines/reference/indexAccessOnGenericMappedTypeWithKeyRemapping.symbols b/tests/baselines/reference/indexAccessOnGenericMappedTypeWithKeyRemapping.symbols
new file mode 100644
index 0000000000000..4c64ea71d4d5c
--- /dev/null
+++ b/tests/baselines/reference/indexAccessOnGenericMappedTypeWithKeyRemapping.symbols
@@ -0,0 +1,24 @@
+=== tests/cases/compiler/indexAccessOnGenericMappedTypeWithKeyRemapping.ts ===
+type Foo<T extends string> = {
+>Foo : Symbol(Foo, Decl(indexAccessOnGenericMappedTypeWithKeyRemapping.ts, 0, 0))
+>T : Symbol(T, Decl(indexAccessOnGenericMappedTypeWithKeyRemapping.ts, 0, 9))
+
+    [RemappedT in T as `get${RemappedT}`]: RemappedT;
+>RemappedT : Symbol(RemappedT, Decl(indexAccessOnGenericMappedTypeWithKeyRemapping.ts, 1, 5))
+>T : Symbol(T, Decl(indexAccessOnGenericMappedTypeWithKeyRemapping.ts, 0, 9))
+>RemappedT : Symbol(RemappedT, Decl(indexAccessOnGenericMappedTypeWithKeyRemapping.ts, 1, 5))
+>RemappedT : Symbol(RemappedT, Decl(indexAccessOnGenericMappedTypeWithKeyRemapping.ts, 1, 5))
+
+};
+const get = <T extends string>(t: T, foo: Foo<T>): T => foo[`get${t}`];
+>get : Symbol(get, Decl(indexAccessOnGenericMappedTypeWithKeyRemapping.ts, 3, 5))
+>T : Symbol(T, Decl(indexAccessOnGenericMappedTypeWithKeyRemapping.ts, 3, 13))
+>t : Symbol(t, Decl(indexAccessOnGenericMappedTypeWithKeyRemapping.ts, 3, 31))
+>T : Symbol(T, Decl(indexAccessOnGenericMappedTypeWithKeyRemapping.ts, 3, 13))
+>foo : Symbol(foo, Decl(indexAccessOnGenericMappedTypeWithKeyRemapping.ts, 3, 36))
+>Foo : Symbol(Foo, Decl(indexAccessOnGenericMappedTypeWithKeyRemapping.ts, 0, 0))
+>T : Symbol(T, Decl(indexAccessOnGenericMappedTypeWithKeyRemapping.ts, 3, 13))
+>T : Symbol(T, Decl(indexAccessOnGenericMappedTypeWithKeyRemapping.ts, 3, 13))
+>foo : Symbol(foo, Decl(indexAccessOnGenericMappedTypeWithKeyRemapping.ts, 3, 36))
+>t : Symbol(t, Decl(indexAccessOnGenericMappedTypeWithKeyRemapping.ts, 3, 31))
+
diff --git a/tests/baselines/reference/indexAccessOnGenericMappedTypeWithKeyRemapping.types b/tests/baselines/reference/indexAccessOnGenericMappedTypeWithKeyRemapping.types
new file mode 100644
index 0000000000000..9e4bd0225f6e4
--- /dev/null
+++ b/tests/baselines/reference/indexAccessOnGenericMappedTypeWithKeyRemapping.types
@@ -0,0 +1,16 @@
+=== tests/cases/compiler/indexAccessOnGenericMappedTypeWithKeyRemapping.ts ===
+type Foo<T extends string> = {
+>Foo : Foo<T>
+
+    [RemappedT in T as `get${RemappedT}`]: RemappedT;
+};
+const get = <T extends string>(t: T, foo: Foo<T>): T => foo[`get${t}`];
+>get : <T extends string>(t: T, foo: Foo<T>) => T
+><T extends string>(t: T, foo: Foo<T>): T => foo[`get${t}`] : <T extends string>(t: T, foo: Foo<T>) => T
+>t : T
+>foo : Foo<T>
+>foo[`get${t}`] : Foo<T>[`get${T}`]
+>foo : Foo<T>
+>`get${t}` : `get${T}`
+>t : T
+
diff --git a/tests/cases/compiler/indexAccessOnGenericMappedTypeWithKeyRemapping.ts b/tests/cases/compiler/indexAccessOnGenericMappedTypeWithKeyRemapping.ts
new file mode 100644
index 0000000000000..ffde5e10b05d5
--- /dev/null
+++ b/tests/cases/compiler/indexAccessOnGenericMappedTypeWithKeyRemapping.ts
@@ -0,0 +1,4 @@
+type Foo<T extends string> = {
+    [RemappedT in T as `get${RemappedT}`]: RemappedT;
+};
+const get = <T extends string>(t: T, foo: Foo<T>): T => foo[`get${t}`];