From 0823eba8a3257b80df68494ac0d534ac9b6bd16b Mon Sep 17 00:00:00 2001
From: Anders Hejlsberg <andersh@microsoft.com>
Date: Mon, 11 Sep 2017 10:38:46 -0700
Subject: [PATCH] Add tests

---
 .../higherOrderMappedIndexLookupInference.js  |  43 ++++++++
 ...herOrderMappedIndexLookupInference.symbols |  98 +++++++++++++++++
 ...igherOrderMappedIndexLookupInference.types | 104 ++++++++++++++++++
 .../higherOrderMappedIndexLookupInference.ts  |  25 +++++
 4 files changed, 270 insertions(+)
 create mode 100644 tests/baselines/reference/higherOrderMappedIndexLookupInference.js
 create mode 100644 tests/baselines/reference/higherOrderMappedIndexLookupInference.symbols
 create mode 100644 tests/baselines/reference/higherOrderMappedIndexLookupInference.types
 create mode 100644 tests/cases/compiler/higherOrderMappedIndexLookupInference.ts

diff --git a/tests/baselines/reference/higherOrderMappedIndexLookupInference.js b/tests/baselines/reference/higherOrderMappedIndexLookupInference.js
new file mode 100644
index 00000000000..e8e09a59713
--- /dev/null
+++ b/tests/baselines/reference/higherOrderMappedIndexLookupInference.js
@@ -0,0 +1,43 @@
+//// [higherOrderMappedIndexLookupInference.ts]
+// @strict
+
+function f1(a: <T>() => keyof T, b: <U>() => keyof U) {
+    a = b;
+    b = a;
+}
+
+function f2(a: <T, K extends keyof T>() => T[K], b: <U, L extends keyof U>() => U[L]) {
+    a = b;
+    b = a;
+}
+
+function f3(a: <T>() => { [K in keyof T]: T[K] }, b: <U>() => { [K in keyof U]: U[K] }) {
+    a = b;
+    b = a;
+}
+
+// Repro from #18338
+
+type IdMapped<T> = { [K in keyof T]: T[K] }
+
+declare const f: <T>() => IdMapped<T>;
+declare const g: <U>() => { [K in keyof U]: U[K] };
+
+const h: typeof g = f;
+
+
+//// [higherOrderMappedIndexLookupInference.js]
+// @strict
+function f1(a, b) {
+    a = b;
+    b = a;
+}
+function f2(a, b) {
+    a = b;
+    b = a;
+}
+function f3(a, b) {
+    a = b;
+    b = a;
+}
+var h = f;
diff --git a/tests/baselines/reference/higherOrderMappedIndexLookupInference.symbols b/tests/baselines/reference/higherOrderMappedIndexLookupInference.symbols
new file mode 100644
index 00000000000..44ecb1e6d02
--- /dev/null
+++ b/tests/baselines/reference/higherOrderMappedIndexLookupInference.symbols
@@ -0,0 +1,98 @@
+=== tests/cases/compiler/higherOrderMappedIndexLookupInference.ts ===
+// @strict
+
+function f1(a: <T>() => keyof T, b: <U>() => keyof U) {
+>f1 : Symbol(f1, Decl(higherOrderMappedIndexLookupInference.ts, 0, 0))
+>a : Symbol(a, Decl(higherOrderMappedIndexLookupInference.ts, 2, 12))
+>T : Symbol(T, Decl(higherOrderMappedIndexLookupInference.ts, 2, 16))
+>T : Symbol(T, Decl(higherOrderMappedIndexLookupInference.ts, 2, 16))
+>b : Symbol(b, Decl(higherOrderMappedIndexLookupInference.ts, 2, 32))
+>U : Symbol(U, Decl(higherOrderMappedIndexLookupInference.ts, 2, 37))
+>U : Symbol(U, Decl(higherOrderMappedIndexLookupInference.ts, 2, 37))
+
+    a = b;
+>a : Symbol(a, Decl(higherOrderMappedIndexLookupInference.ts, 2, 12))
+>b : Symbol(b, Decl(higherOrderMappedIndexLookupInference.ts, 2, 32))
+
+    b = a;
+>b : Symbol(b, Decl(higherOrderMappedIndexLookupInference.ts, 2, 32))
+>a : Symbol(a, Decl(higherOrderMappedIndexLookupInference.ts, 2, 12))
+}
+
+function f2(a: <T, K extends keyof T>() => T[K], b: <U, L extends keyof U>() => U[L]) {
+>f2 : Symbol(f2, Decl(higherOrderMappedIndexLookupInference.ts, 5, 1))
+>a : Symbol(a, Decl(higherOrderMappedIndexLookupInference.ts, 7, 12))
+>T : Symbol(T, Decl(higherOrderMappedIndexLookupInference.ts, 7, 16))
+>K : Symbol(K, Decl(higherOrderMappedIndexLookupInference.ts, 7, 18))
+>T : Symbol(T, Decl(higherOrderMappedIndexLookupInference.ts, 7, 16))
+>T : Symbol(T, Decl(higherOrderMappedIndexLookupInference.ts, 7, 16))
+>K : Symbol(K, Decl(higherOrderMappedIndexLookupInference.ts, 7, 18))
+>b : Symbol(b, Decl(higherOrderMappedIndexLookupInference.ts, 7, 48))
+>U : Symbol(U, Decl(higherOrderMappedIndexLookupInference.ts, 7, 53))
+>L : Symbol(L, Decl(higherOrderMappedIndexLookupInference.ts, 7, 55))
+>U : Symbol(U, Decl(higherOrderMappedIndexLookupInference.ts, 7, 53))
+>U : Symbol(U, Decl(higherOrderMappedIndexLookupInference.ts, 7, 53))
+>L : Symbol(L, Decl(higherOrderMappedIndexLookupInference.ts, 7, 55))
+
+    a = b;
+>a : Symbol(a, Decl(higherOrderMappedIndexLookupInference.ts, 7, 12))
+>b : Symbol(b, Decl(higherOrderMappedIndexLookupInference.ts, 7, 48))
+
+    b = a;
+>b : Symbol(b, Decl(higherOrderMappedIndexLookupInference.ts, 7, 48))
+>a : Symbol(a, Decl(higherOrderMappedIndexLookupInference.ts, 7, 12))
+}
+
+function f3(a: <T>() => { [K in keyof T]: T[K] }, b: <U>() => { [K in keyof U]: U[K] }) {
+>f3 : Symbol(f3, Decl(higherOrderMappedIndexLookupInference.ts, 10, 1))
+>a : Symbol(a, Decl(higherOrderMappedIndexLookupInference.ts, 12, 12))
+>T : Symbol(T, Decl(higherOrderMappedIndexLookupInference.ts, 12, 16))
+>K : Symbol(K, Decl(higherOrderMappedIndexLookupInference.ts, 12, 27))
+>T : Symbol(T, Decl(higherOrderMappedIndexLookupInference.ts, 12, 16))
+>T : Symbol(T, Decl(higherOrderMappedIndexLookupInference.ts, 12, 16))
+>K : Symbol(K, Decl(higherOrderMappedIndexLookupInference.ts, 12, 27))
+>b : Symbol(b, Decl(higherOrderMappedIndexLookupInference.ts, 12, 49))
+>U : Symbol(U, Decl(higherOrderMappedIndexLookupInference.ts, 12, 54))
+>K : Symbol(K, Decl(higherOrderMappedIndexLookupInference.ts, 12, 65))
+>U : Symbol(U, Decl(higherOrderMappedIndexLookupInference.ts, 12, 54))
+>U : Symbol(U, Decl(higherOrderMappedIndexLookupInference.ts, 12, 54))
+>K : Symbol(K, Decl(higherOrderMappedIndexLookupInference.ts, 12, 65))
+
+    a = b;
+>a : Symbol(a, Decl(higherOrderMappedIndexLookupInference.ts, 12, 12))
+>b : Symbol(b, Decl(higherOrderMappedIndexLookupInference.ts, 12, 49))
+
+    b = a;
+>b : Symbol(b, Decl(higherOrderMappedIndexLookupInference.ts, 12, 49))
+>a : Symbol(a, Decl(higherOrderMappedIndexLookupInference.ts, 12, 12))
+}
+
+// Repro from #18338
+
+type IdMapped<T> = { [K in keyof T]: T[K] }
+>IdMapped : Symbol(IdMapped, Decl(higherOrderMappedIndexLookupInference.ts, 15, 1))
+>T : Symbol(T, Decl(higherOrderMappedIndexLookupInference.ts, 19, 14))
+>K : Symbol(K, Decl(higherOrderMappedIndexLookupInference.ts, 19, 22))
+>T : Symbol(T, Decl(higherOrderMappedIndexLookupInference.ts, 19, 14))
+>T : Symbol(T, Decl(higherOrderMappedIndexLookupInference.ts, 19, 14))
+>K : Symbol(K, Decl(higherOrderMappedIndexLookupInference.ts, 19, 22))
+
+declare const f: <T>() => IdMapped<T>;
+>f : Symbol(f, Decl(higherOrderMappedIndexLookupInference.ts, 21, 13))
+>T : Symbol(T, Decl(higherOrderMappedIndexLookupInference.ts, 21, 18))
+>IdMapped : Symbol(IdMapped, Decl(higherOrderMappedIndexLookupInference.ts, 15, 1))
+>T : Symbol(T, Decl(higherOrderMappedIndexLookupInference.ts, 21, 18))
+
+declare const g: <U>() => { [K in keyof U]: U[K] };
+>g : Symbol(g, Decl(higherOrderMappedIndexLookupInference.ts, 22, 13))
+>U : Symbol(U, Decl(higherOrderMappedIndexLookupInference.ts, 22, 18))
+>K : Symbol(K, Decl(higherOrderMappedIndexLookupInference.ts, 22, 29))
+>U : Symbol(U, Decl(higherOrderMappedIndexLookupInference.ts, 22, 18))
+>U : Symbol(U, Decl(higherOrderMappedIndexLookupInference.ts, 22, 18))
+>K : Symbol(K, Decl(higherOrderMappedIndexLookupInference.ts, 22, 29))
+
+const h: typeof g = f;
+>h : Symbol(h, Decl(higherOrderMappedIndexLookupInference.ts, 24, 5))
+>g : Symbol(g, Decl(higherOrderMappedIndexLookupInference.ts, 22, 13))
+>f : Symbol(f, Decl(higherOrderMappedIndexLookupInference.ts, 21, 13))
+
diff --git a/tests/baselines/reference/higherOrderMappedIndexLookupInference.types b/tests/baselines/reference/higherOrderMappedIndexLookupInference.types
new file mode 100644
index 00000000000..f1c2b0aa17b
--- /dev/null
+++ b/tests/baselines/reference/higherOrderMappedIndexLookupInference.types
@@ -0,0 +1,104 @@
+=== tests/cases/compiler/higherOrderMappedIndexLookupInference.ts ===
+// @strict
+
+function f1(a: <T>() => keyof T, b: <U>() => keyof U) {
+>f1 : (a: <T>() => keyof T, b: <U>() => keyof U) => void
+>a : <T>() => keyof T
+>T : T
+>T : T
+>b : <U>() => keyof U
+>U : U
+>U : U
+
+    a = b;
+>a = b : <U>() => keyof U
+>a : <T>() => keyof T
+>b : <U>() => keyof U
+
+    b = a;
+>b = a : <T>() => keyof T
+>b : <U>() => keyof U
+>a : <T>() => keyof T
+}
+
+function f2(a: <T, K extends keyof T>() => T[K], b: <U, L extends keyof U>() => U[L]) {
+>f2 : (a: <T, K extends keyof T>() => T[K], b: <U, L extends keyof U>() => U[L]) => void
+>a : <T, K extends keyof T>() => T[K]
+>T : T
+>K : K
+>T : T
+>T : T
+>K : K
+>b : <U, L extends keyof U>() => U[L]
+>U : U
+>L : L
+>U : U
+>U : U
+>L : L
+
+    a = b;
+>a = b : <U, L extends keyof U>() => U[L]
+>a : <T, K extends keyof T>() => T[K]
+>b : <U, L extends keyof U>() => U[L]
+
+    b = a;
+>b = a : <T, K extends keyof T>() => T[K]
+>b : <U, L extends keyof U>() => U[L]
+>a : <T, K extends keyof T>() => T[K]
+}
+
+function f3(a: <T>() => { [K in keyof T]: T[K] }, b: <U>() => { [K in keyof U]: U[K] }) {
+>f3 : (a: <T>() => { [K in keyof T]: T[K]; }, b: <U>() => { [K in keyof U]: U[K]; }) => void
+>a : <T>() => { [K in keyof T]: T[K]; }
+>T : T
+>K : K
+>T : T
+>T : T
+>K : K
+>b : <U>() => { [K in keyof U]: U[K]; }
+>U : U
+>K : K
+>U : U
+>U : U
+>K : K
+
+    a = b;
+>a = b : <U>() => { [K in keyof U]: U[K]; }
+>a : <T>() => { [K in keyof T]: T[K]; }
+>b : <U>() => { [K in keyof U]: U[K]; }
+
+    b = a;
+>b = a : <T>() => { [K in keyof T]: T[K]; }
+>b : <U>() => { [K in keyof U]: U[K]; }
+>a : <T>() => { [K in keyof T]: T[K]; }
+}
+
+// Repro from #18338
+
+type IdMapped<T> = { [K in keyof T]: T[K] }
+>IdMapped : IdMapped<T>
+>T : T
+>K : K
+>T : T
+>T : T
+>K : K
+
+declare const f: <T>() => IdMapped<T>;
+>f : <T>() => IdMapped<T>
+>T : T
+>IdMapped : IdMapped<T>
+>T : T
+
+declare const g: <U>() => { [K in keyof U]: U[K] };
+>g : <U>() => { [K in keyof U]: U[K]; }
+>U : U
+>K : K
+>U : U
+>U : U
+>K : K
+
+const h: typeof g = f;
+>h : <U>() => { [K in keyof U]: U[K]; }
+>g : <U>() => { [K in keyof U]: U[K]; }
+>f : <T>() => IdMapped<T>
+
diff --git a/tests/cases/compiler/higherOrderMappedIndexLookupInference.ts b/tests/cases/compiler/higherOrderMappedIndexLookupInference.ts
new file mode 100644
index 00000000000..96156283915
--- /dev/null
+++ b/tests/cases/compiler/higherOrderMappedIndexLookupInference.ts
@@ -0,0 +1,25 @@
+// @strict
+
+function f1(a: <T>() => keyof T, b: <U>() => keyof U) {
+    a = b;
+    b = a;
+}
+
+function f2(a: <T, K extends keyof T>() => T[K], b: <U, L extends keyof U>() => U[L]) {
+    a = b;
+    b = a;
+}
+
+function f3(a: <T>() => { [K in keyof T]: T[K] }, b: <U>() => { [K in keyof U]: U[K] }) {
+    a = b;
+    b = a;
+}
+
+// Repro from #18338
+
+type IdMapped<T> = { [K in keyof T]: T[K] }
+
+declare const f: <T>() => IdMapped<T>;
+declare const g: <U>() => { [K in keyof U]: U[K] };
+
+const h: typeof g = f;