From dd07cdc60eef30442dc455001488578a968474dd Mon Sep 17 00:00:00 2001
From: Anders Hejlsberg <andersh@microsoft.com>
Date: Thu, 7 Oct 2021 16:36:34 -0700
Subject: [PATCH] Add tests

---
 .../dependentDestructuredVariables.js         | 336 +++++++++++++
 .../dependentDestructuredVariables.symbols    | 409 ++++++++++++++++
 .../dependentDestructuredVariables.types      | 441 ++++++++++++++++++
 .../dependentDestructuredVariables.ts         | 161 +++++++
 4 files changed, 1347 insertions(+)
 create mode 100644 tests/baselines/reference/dependentDestructuredVariables.js
 create mode 100644 tests/baselines/reference/dependentDestructuredVariables.symbols
 create mode 100644 tests/baselines/reference/dependentDestructuredVariables.types
 create mode 100644 tests/cases/conformance/controlFlow/dependentDestructuredVariables.ts

diff --git a/tests/baselines/reference/dependentDestructuredVariables.js b/tests/baselines/reference/dependentDestructuredVariables.js
new file mode 100644
index 0000000000000..82d41eb8b8d8d
--- /dev/null
+++ b/tests/baselines/reference/dependentDestructuredVariables.js
@@ -0,0 +1,336 @@
+//// [dependentDestructuredVariables.ts]
+type Action =
+    | { kind: 'A', payload: number }
+    | { kind: 'B', payload: string };
+
+function f10({ kind, payload }: Action) {
+    if (kind === 'A') {
+        payload.toFixed();
+    }
+    if (kind === 'B') {
+        payload.toUpperCase();
+    }
+}
+
+function f11(action: Action) {
+    const { kind, payload } = action;
+    if (kind === 'A') {
+        payload.toFixed();
+    }
+    if (kind === 'B') {
+        payload.toUpperCase();
+    }
+}
+
+function f12({ kind, payload }: Action) {
+    switch (kind) {
+        case 'A':
+            payload.toFixed();
+            break;
+        case 'B':
+            payload.toUpperCase();
+            break;
+        default:
+            payload;  // never
+    }
+}
+
+type Action2 =
+    | { kind: 'A', payload: number | undefined }
+    | { kind: 'B', payload: string | undefined };
+
+function f20({ kind, payload }: Action2) {
+    if (payload) {
+        if (kind === 'A') {
+            payload.toFixed();
+        }
+        if (kind === 'B') {
+            payload.toUpperCase();
+        }
+    }
+}
+
+function f21(action: Action2) {
+    const { kind, payload } = action;
+    if (payload) {
+        if (kind === 'A') {
+            payload.toFixed();
+        }
+        if (kind === 'B') {
+            payload.toUpperCase();
+        }
+    }
+}
+
+function f22(action: Action2) {
+    if (action.payload) {
+        const { kind, payload } = action;
+        if (kind === 'A') {
+            payload.toFixed();
+        }
+        if (kind === 'B') {
+            payload.toUpperCase();
+        }
+    }
+}
+
+function f23({ kind, payload }: Action2) {
+    if (payload) {
+        switch (kind) {
+            case 'A':
+                payload.toFixed();
+                break;
+            case 'B':
+                payload.toUpperCase();
+                break;
+            default:
+                payload;  // never
+        }
+    }
+}
+
+type Foo =
+    | { kind: 'A', isA: true }
+    | { kind: 'B', isA: false }
+    | { kind: 'C', isA: false };
+
+function f30({ kind, isA }: Foo) {
+    if (kind === 'A') {
+        isA;   // true
+    }
+    if (kind === 'B') {
+        isA;   // false
+    }
+    if (kind === 'C') {
+        isA;   // false
+    }
+    if (isA) {
+        kind;  // 'A'
+    }
+    else {
+        kind;  // 'B' | 'C'
+    }
+}
+
+// Repro from #35283
+
+interface A<T> { variant: 'a', value: T }
+
+interface B<T> { variant: 'b', value: Array<T> }
+
+type AB<T> = A<T> | B<T>;
+
+declare function printValue<T>(t: T): void;
+
+declare function printValueList<T>(t: Array<T>): void;
+
+function unrefined1<T>(ab: AB<T>): void {
+    const { variant, value } = ab;
+    if (variant === 'a') {
+        printValue<T>(value);
+    }
+    else {
+        printValueList<T>(value);
+    }
+}
+
+// Repro from #38020
+
+type Action3 =
+    | {type: 'add', payload: { toAdd: number } }
+    | {type: 'remove', payload: { toRemove: number } };
+
+const reducerBroken = (state: number, { type, payload }: Action3) => {
+    switch (type) {
+        case 'add':
+            return state + payload.toAdd;
+        case 'remove':
+            return state - payload.toRemove;
+    }
+}
+
+// Repro from #46143
+
+declare var it: Iterator<number>;
+const { value, done } = it.next();
+if (!done) {
+    value;  // number
+}
+
+
+//// [dependentDestructuredVariables.js]
+"use strict";
+function f10({ kind, payload }) {
+    if (kind === 'A') {
+        payload.toFixed();
+    }
+    if (kind === 'B') {
+        payload.toUpperCase();
+    }
+}
+function f11(action) {
+    const { kind, payload } = action;
+    if (kind === 'A') {
+        payload.toFixed();
+    }
+    if (kind === 'B') {
+        payload.toUpperCase();
+    }
+}
+function f12({ kind, payload }) {
+    switch (kind) {
+        case 'A':
+            payload.toFixed();
+            break;
+        case 'B':
+            payload.toUpperCase();
+            break;
+        default:
+            payload; // never
+    }
+}
+function f20({ kind, payload }) {
+    if (payload) {
+        if (kind === 'A') {
+            payload.toFixed();
+        }
+        if (kind === 'B') {
+            payload.toUpperCase();
+        }
+    }
+}
+function f21(action) {
+    const { kind, payload } = action;
+    if (payload) {
+        if (kind === 'A') {
+            payload.toFixed();
+        }
+        if (kind === 'B') {
+            payload.toUpperCase();
+        }
+    }
+}
+function f22(action) {
+    if (action.payload) {
+        const { kind, payload } = action;
+        if (kind === 'A') {
+            payload.toFixed();
+        }
+        if (kind === 'B') {
+            payload.toUpperCase();
+        }
+    }
+}
+function f23({ kind, payload }) {
+    if (payload) {
+        switch (kind) {
+            case 'A':
+                payload.toFixed();
+                break;
+            case 'B':
+                payload.toUpperCase();
+                break;
+            default:
+                payload; // never
+        }
+    }
+}
+function f30({ kind, isA }) {
+    if (kind === 'A') {
+        isA; // true
+    }
+    if (kind === 'B') {
+        isA; // false
+    }
+    if (kind === 'C') {
+        isA; // false
+    }
+    if (isA) {
+        kind; // 'A'
+    }
+    else {
+        kind; // 'B' | 'C'
+    }
+}
+function unrefined1(ab) {
+    const { variant, value } = ab;
+    if (variant === 'a') {
+        printValue(value);
+    }
+    else {
+        printValueList(value);
+    }
+}
+const reducerBroken = (state, { type, payload }) => {
+    switch (type) {
+        case 'add':
+            return state + payload.toAdd;
+        case 'remove':
+            return state - payload.toRemove;
+    }
+};
+const { value, done } = it.next();
+if (!done) {
+    value; // number
+}
+
+
+//// [dependentDestructuredVariables.d.ts]
+declare type Action = {
+    kind: 'A';
+    payload: number;
+} | {
+    kind: 'B';
+    payload: string;
+};
+declare function f10({ kind, payload }: Action): void;
+declare function f11(action: Action): void;
+declare function f12({ kind, payload }: Action): void;
+declare type Action2 = {
+    kind: 'A';
+    payload: number | undefined;
+} | {
+    kind: 'B';
+    payload: string | undefined;
+};
+declare function f20({ kind, payload }: Action2): void;
+declare function f21(action: Action2): void;
+declare function f22(action: Action2): void;
+declare function f23({ kind, payload }: Action2): void;
+declare type Foo = {
+    kind: 'A';
+    isA: true;
+} | {
+    kind: 'B';
+    isA: false;
+} | {
+    kind: 'C';
+    isA: false;
+};
+declare function f30({ kind, isA }: Foo): void;
+interface A<T> {
+    variant: 'a';
+    value: T;
+}
+interface B<T> {
+    variant: 'b';
+    value: Array<T>;
+}
+declare type AB<T> = A<T> | B<T>;
+declare function printValue<T>(t: T): void;
+declare function printValueList<T>(t: Array<T>): void;
+declare function unrefined1<T>(ab: AB<T>): void;
+declare type Action3 = {
+    type: 'add';
+    payload: {
+        toAdd: number;
+    };
+} | {
+    type: 'remove';
+    payload: {
+        toRemove: number;
+    };
+};
+declare const reducerBroken: (state: number, { type, payload }: Action3) => number;
+declare var it: Iterator<number>;
+declare const value: any, done: boolean | undefined;
diff --git a/tests/baselines/reference/dependentDestructuredVariables.symbols b/tests/baselines/reference/dependentDestructuredVariables.symbols
new file mode 100644
index 0000000000000..2700f368585fe
--- /dev/null
+++ b/tests/baselines/reference/dependentDestructuredVariables.symbols
@@ -0,0 +1,409 @@
+=== tests/cases/conformance/controlFlow/dependentDestructuredVariables.ts ===
+type Action =
+>Action : Symbol(Action, Decl(dependentDestructuredVariables.ts, 0, 0))
+
+    | { kind: 'A', payload: number }
+>kind : Symbol(kind, Decl(dependentDestructuredVariables.ts, 1, 7))
+>payload : Symbol(payload, Decl(dependentDestructuredVariables.ts, 1, 18))
+
+    | { kind: 'B', payload: string };
+>kind : Symbol(kind, Decl(dependentDestructuredVariables.ts, 2, 7))
+>payload : Symbol(payload, Decl(dependentDestructuredVariables.ts, 2, 18))
+
+function f10({ kind, payload }: Action) {
+>f10 : Symbol(f10, Decl(dependentDestructuredVariables.ts, 2, 37))
+>kind : Symbol(kind, Decl(dependentDestructuredVariables.ts, 4, 14))
+>payload : Symbol(payload, Decl(dependentDestructuredVariables.ts, 4, 20))
+>Action : Symbol(Action, Decl(dependentDestructuredVariables.ts, 0, 0))
+
+    if (kind === 'A') {
+>kind : Symbol(kind, Decl(dependentDestructuredVariables.ts, 4, 14))
+
+        payload.toFixed();
+>payload.toFixed : Symbol(Number.toFixed, Decl(lib.es5.d.ts, --, --))
+>payload : Symbol(payload, Decl(dependentDestructuredVariables.ts, 4, 20))
+>toFixed : Symbol(Number.toFixed, Decl(lib.es5.d.ts, --, --))
+    }
+    if (kind === 'B') {
+>kind : Symbol(kind, Decl(dependentDestructuredVariables.ts, 4, 14))
+
+        payload.toUpperCase();
+>payload.toUpperCase : Symbol(String.toUpperCase, Decl(lib.es5.d.ts, --, --))
+>payload : Symbol(payload, Decl(dependentDestructuredVariables.ts, 4, 20))
+>toUpperCase : Symbol(String.toUpperCase, Decl(lib.es5.d.ts, --, --))
+    }
+}
+
+function f11(action: Action) {
+>f11 : Symbol(f11, Decl(dependentDestructuredVariables.ts, 11, 1))
+>action : Symbol(action, Decl(dependentDestructuredVariables.ts, 13, 13))
+>Action : Symbol(Action, Decl(dependentDestructuredVariables.ts, 0, 0))
+
+    const { kind, payload } = action;
+>kind : Symbol(kind, Decl(dependentDestructuredVariables.ts, 14, 11))
+>payload : Symbol(payload, Decl(dependentDestructuredVariables.ts, 14, 17))
+>action : Symbol(action, Decl(dependentDestructuredVariables.ts, 13, 13))
+
+    if (kind === 'A') {
+>kind : Symbol(kind, Decl(dependentDestructuredVariables.ts, 14, 11))
+
+        payload.toFixed();
+>payload.toFixed : Symbol(Number.toFixed, Decl(lib.es5.d.ts, --, --))
+>payload : Symbol(payload, Decl(dependentDestructuredVariables.ts, 14, 17))
+>toFixed : Symbol(Number.toFixed, Decl(lib.es5.d.ts, --, --))
+    }
+    if (kind === 'B') {
+>kind : Symbol(kind, Decl(dependentDestructuredVariables.ts, 14, 11))
+
+        payload.toUpperCase();
+>payload.toUpperCase : Symbol(String.toUpperCase, Decl(lib.es5.d.ts, --, --))
+>payload : Symbol(payload, Decl(dependentDestructuredVariables.ts, 14, 17))
+>toUpperCase : Symbol(String.toUpperCase, Decl(lib.es5.d.ts, --, --))
+    }
+}
+
+function f12({ kind, payload }: Action) {
+>f12 : Symbol(f12, Decl(dependentDestructuredVariables.ts, 21, 1))
+>kind : Symbol(kind, Decl(dependentDestructuredVariables.ts, 23, 14))
+>payload : Symbol(payload, Decl(dependentDestructuredVariables.ts, 23, 20))
+>Action : Symbol(Action, Decl(dependentDestructuredVariables.ts, 0, 0))
+
+    switch (kind) {
+>kind : Symbol(kind, Decl(dependentDestructuredVariables.ts, 23, 14))
+
+        case 'A':
+            payload.toFixed();
+>payload.toFixed : Symbol(Number.toFixed, Decl(lib.es5.d.ts, --, --))
+>payload : Symbol(payload, Decl(dependentDestructuredVariables.ts, 23, 20))
+>toFixed : Symbol(Number.toFixed, Decl(lib.es5.d.ts, --, --))
+
+            break;
+        case 'B':
+            payload.toUpperCase();
+>payload.toUpperCase : Symbol(String.toUpperCase, Decl(lib.es5.d.ts, --, --))
+>payload : Symbol(payload, Decl(dependentDestructuredVariables.ts, 23, 20))
+>toUpperCase : Symbol(String.toUpperCase, Decl(lib.es5.d.ts, --, --))
+
+            break;
+        default:
+            payload;  // never
+>payload : Symbol(payload, Decl(dependentDestructuredVariables.ts, 23, 20))
+    }
+}
+
+type Action2 =
+>Action2 : Symbol(Action2, Decl(dependentDestructuredVariables.ts, 34, 1))
+
+    | { kind: 'A', payload: number | undefined }
+>kind : Symbol(kind, Decl(dependentDestructuredVariables.ts, 37, 7))
+>payload : Symbol(payload, Decl(dependentDestructuredVariables.ts, 37, 18))
+
+    | { kind: 'B', payload: string | undefined };
+>kind : Symbol(kind, Decl(dependentDestructuredVariables.ts, 38, 7))
+>payload : Symbol(payload, Decl(dependentDestructuredVariables.ts, 38, 18))
+
+function f20({ kind, payload }: Action2) {
+>f20 : Symbol(f20, Decl(dependentDestructuredVariables.ts, 38, 49))
+>kind : Symbol(kind, Decl(dependentDestructuredVariables.ts, 40, 14))
+>payload : Symbol(payload, Decl(dependentDestructuredVariables.ts, 40, 20))
+>Action2 : Symbol(Action2, Decl(dependentDestructuredVariables.ts, 34, 1))
+
+    if (payload) {
+>payload : Symbol(payload, Decl(dependentDestructuredVariables.ts, 40, 20))
+
+        if (kind === 'A') {
+>kind : Symbol(kind, Decl(dependentDestructuredVariables.ts, 40, 14))
+
+            payload.toFixed();
+>payload.toFixed : Symbol(Number.toFixed, Decl(lib.es5.d.ts, --, --))
+>payload : Symbol(payload, Decl(dependentDestructuredVariables.ts, 40, 20))
+>toFixed : Symbol(Number.toFixed, Decl(lib.es5.d.ts, --, --))
+        }
+        if (kind === 'B') {
+>kind : Symbol(kind, Decl(dependentDestructuredVariables.ts, 40, 14))
+
+            payload.toUpperCase();
+>payload.toUpperCase : Symbol(String.toUpperCase, Decl(lib.es5.d.ts, --, --))
+>payload : Symbol(payload, Decl(dependentDestructuredVariables.ts, 40, 20))
+>toUpperCase : Symbol(String.toUpperCase, Decl(lib.es5.d.ts, --, --))
+        }
+    }
+}
+
+function f21(action: Action2) {
+>f21 : Symbol(f21, Decl(dependentDestructuredVariables.ts, 49, 1))
+>action : Symbol(action, Decl(dependentDestructuredVariables.ts, 51, 13))
+>Action2 : Symbol(Action2, Decl(dependentDestructuredVariables.ts, 34, 1))
+
+    const { kind, payload } = action;
+>kind : Symbol(kind, Decl(dependentDestructuredVariables.ts, 52, 11))
+>payload : Symbol(payload, Decl(dependentDestructuredVariables.ts, 52, 17))
+>action : Symbol(action, Decl(dependentDestructuredVariables.ts, 51, 13))
+
+    if (payload) {
+>payload : Symbol(payload, Decl(dependentDestructuredVariables.ts, 52, 17))
+
+        if (kind === 'A') {
+>kind : Symbol(kind, Decl(dependentDestructuredVariables.ts, 52, 11))
+
+            payload.toFixed();
+>payload.toFixed : Symbol(Number.toFixed, Decl(lib.es5.d.ts, --, --))
+>payload : Symbol(payload, Decl(dependentDestructuredVariables.ts, 52, 17))
+>toFixed : Symbol(Number.toFixed, Decl(lib.es5.d.ts, --, --))
+        }
+        if (kind === 'B') {
+>kind : Symbol(kind, Decl(dependentDestructuredVariables.ts, 52, 11))
+
+            payload.toUpperCase();
+>payload.toUpperCase : Symbol(String.toUpperCase, Decl(lib.es5.d.ts, --, --))
+>payload : Symbol(payload, Decl(dependentDestructuredVariables.ts, 52, 17))
+>toUpperCase : Symbol(String.toUpperCase, Decl(lib.es5.d.ts, --, --))
+        }
+    }
+}
+
+function f22(action: Action2) {
+>f22 : Symbol(f22, Decl(dependentDestructuredVariables.ts, 61, 1))
+>action : Symbol(action, Decl(dependentDestructuredVariables.ts, 63, 13))
+>Action2 : Symbol(Action2, Decl(dependentDestructuredVariables.ts, 34, 1))
+
+    if (action.payload) {
+>action.payload : Symbol(payload, Decl(dependentDestructuredVariables.ts, 37, 18), Decl(dependentDestructuredVariables.ts, 38, 18))
+>action : Symbol(action, Decl(dependentDestructuredVariables.ts, 63, 13))
+>payload : Symbol(payload, Decl(dependentDestructuredVariables.ts, 37, 18), Decl(dependentDestructuredVariables.ts, 38, 18))
+
+        const { kind, payload } = action;
+>kind : Symbol(kind, Decl(dependentDestructuredVariables.ts, 65, 15))
+>payload : Symbol(payload, Decl(dependentDestructuredVariables.ts, 65, 21))
+>action : Symbol(action, Decl(dependentDestructuredVariables.ts, 63, 13))
+
+        if (kind === 'A') {
+>kind : Symbol(kind, Decl(dependentDestructuredVariables.ts, 65, 15))
+
+            payload.toFixed();
+>payload.toFixed : Symbol(Number.toFixed, Decl(lib.es5.d.ts, --, --))
+>payload : Symbol(payload, Decl(dependentDestructuredVariables.ts, 65, 21))
+>toFixed : Symbol(Number.toFixed, Decl(lib.es5.d.ts, --, --))
+        }
+        if (kind === 'B') {
+>kind : Symbol(kind, Decl(dependentDestructuredVariables.ts, 65, 15))
+
+            payload.toUpperCase();
+>payload.toUpperCase : Symbol(String.toUpperCase, Decl(lib.es5.d.ts, --, --))
+>payload : Symbol(payload, Decl(dependentDestructuredVariables.ts, 65, 21))
+>toUpperCase : Symbol(String.toUpperCase, Decl(lib.es5.d.ts, --, --))
+        }
+    }
+}
+
+function f23({ kind, payload }: Action2) {
+>f23 : Symbol(f23, Decl(dependentDestructuredVariables.ts, 73, 1))
+>kind : Symbol(kind, Decl(dependentDestructuredVariables.ts, 75, 14))
+>payload : Symbol(payload, Decl(dependentDestructuredVariables.ts, 75, 20))
+>Action2 : Symbol(Action2, Decl(dependentDestructuredVariables.ts, 34, 1))
+
+    if (payload) {
+>payload : Symbol(payload, Decl(dependentDestructuredVariables.ts, 75, 20))
+
+        switch (kind) {
+>kind : Symbol(kind, Decl(dependentDestructuredVariables.ts, 75, 14))
+
+            case 'A':
+                payload.toFixed();
+>payload.toFixed : Symbol(Number.toFixed, Decl(lib.es5.d.ts, --, --))
+>payload : Symbol(payload, Decl(dependentDestructuredVariables.ts, 75, 20))
+>toFixed : Symbol(Number.toFixed, Decl(lib.es5.d.ts, --, --))
+
+                break;
+            case 'B':
+                payload.toUpperCase();
+>payload.toUpperCase : Symbol(String.toUpperCase, Decl(lib.es5.d.ts, --, --))
+>payload : Symbol(payload, Decl(dependentDestructuredVariables.ts, 75, 20))
+>toUpperCase : Symbol(String.toUpperCase, Decl(lib.es5.d.ts, --, --))
+
+                break;
+            default:
+                payload;  // never
+>payload : Symbol(payload, Decl(dependentDestructuredVariables.ts, 75, 20))
+        }
+    }
+}
+
+type Foo =
+>Foo : Symbol(Foo, Decl(dependentDestructuredVariables.ts, 88, 1))
+
+    | { kind: 'A', isA: true }
+>kind : Symbol(kind, Decl(dependentDestructuredVariables.ts, 91, 7))
+>isA : Symbol(isA, Decl(dependentDestructuredVariables.ts, 91, 18))
+
+    | { kind: 'B', isA: false }
+>kind : Symbol(kind, Decl(dependentDestructuredVariables.ts, 92, 7))
+>isA : Symbol(isA, Decl(dependentDestructuredVariables.ts, 92, 18))
+
+    | { kind: 'C', isA: false };
+>kind : Symbol(kind, Decl(dependentDestructuredVariables.ts, 93, 7))
+>isA : Symbol(isA, Decl(dependentDestructuredVariables.ts, 93, 18))
+
+function f30({ kind, isA }: Foo) {
+>f30 : Symbol(f30, Decl(dependentDestructuredVariables.ts, 93, 32))
+>kind : Symbol(kind, Decl(dependentDestructuredVariables.ts, 95, 14))
+>isA : Symbol(isA, Decl(dependentDestructuredVariables.ts, 95, 20))
+>Foo : Symbol(Foo, Decl(dependentDestructuredVariables.ts, 88, 1))
+
+    if (kind === 'A') {
+>kind : Symbol(kind, Decl(dependentDestructuredVariables.ts, 95, 14))
+
+        isA;   // true
+>isA : Symbol(isA, Decl(dependentDestructuredVariables.ts, 95, 20))
+    }
+    if (kind === 'B') {
+>kind : Symbol(kind, Decl(dependentDestructuredVariables.ts, 95, 14))
+
+        isA;   // false
+>isA : Symbol(isA, Decl(dependentDestructuredVariables.ts, 95, 20))
+    }
+    if (kind === 'C') {
+>kind : Symbol(kind, Decl(dependentDestructuredVariables.ts, 95, 14))
+
+        isA;   // false
+>isA : Symbol(isA, Decl(dependentDestructuredVariables.ts, 95, 20))
+    }
+    if (isA) {
+>isA : Symbol(isA, Decl(dependentDestructuredVariables.ts, 95, 20))
+
+        kind;  // 'A'
+>kind : Symbol(kind, Decl(dependentDestructuredVariables.ts, 95, 14))
+    }
+    else {
+        kind;  // 'B' | 'C'
+>kind : Symbol(kind, Decl(dependentDestructuredVariables.ts, 95, 14))
+    }
+}
+
+// Repro from #35283
+
+interface A<T> { variant: 'a', value: T }
+>A : Symbol(A, Decl(dependentDestructuredVariables.ts, 111, 1))
+>T : Symbol(T, Decl(dependentDestructuredVariables.ts, 115, 12))
+>variant : Symbol(A.variant, Decl(dependentDestructuredVariables.ts, 115, 16))
+>value : Symbol(A.value, Decl(dependentDestructuredVariables.ts, 115, 30))
+>T : Symbol(T, Decl(dependentDestructuredVariables.ts, 115, 12))
+
+interface B<T> { variant: 'b', value: Array<T> }
+>B : Symbol(B, Decl(dependentDestructuredVariables.ts, 115, 41))
+>T : Symbol(T, Decl(dependentDestructuredVariables.ts, 117, 12))
+>variant : Symbol(B.variant, Decl(dependentDestructuredVariables.ts, 117, 16))
+>value : Symbol(B.value, Decl(dependentDestructuredVariables.ts, 117, 30))
+>Array : Symbol(Array, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --), Decl(lib.es2015.core.d.ts, --, --), Decl(lib.es2015.iterable.d.ts, --, --), Decl(lib.es2015.symbol.wellknown.d.ts, --, --))
+>T : Symbol(T, Decl(dependentDestructuredVariables.ts, 117, 12))
+
+type AB<T> = A<T> | B<T>;
+>AB : Symbol(AB, Decl(dependentDestructuredVariables.ts, 117, 48))
+>T : Symbol(T, Decl(dependentDestructuredVariables.ts, 119, 8))
+>A : Symbol(A, Decl(dependentDestructuredVariables.ts, 111, 1))
+>T : Symbol(T, Decl(dependentDestructuredVariables.ts, 119, 8))
+>B : Symbol(B, Decl(dependentDestructuredVariables.ts, 115, 41))
+>T : Symbol(T, Decl(dependentDestructuredVariables.ts, 119, 8))
+
+declare function printValue<T>(t: T): void;
+>printValue : Symbol(printValue, Decl(dependentDestructuredVariables.ts, 119, 25))
+>T : Symbol(T, Decl(dependentDestructuredVariables.ts, 121, 28))
+>t : Symbol(t, Decl(dependentDestructuredVariables.ts, 121, 31))
+>T : Symbol(T, Decl(dependentDestructuredVariables.ts, 121, 28))
+
+declare function printValueList<T>(t: Array<T>): void;
+>printValueList : Symbol(printValueList, Decl(dependentDestructuredVariables.ts, 121, 43))
+>T : Symbol(T, Decl(dependentDestructuredVariables.ts, 123, 32))
+>t : Symbol(t, Decl(dependentDestructuredVariables.ts, 123, 35))
+>Array : Symbol(Array, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --), Decl(lib.es2015.core.d.ts, --, --), Decl(lib.es2015.iterable.d.ts, --, --), Decl(lib.es2015.symbol.wellknown.d.ts, --, --))
+>T : Symbol(T, Decl(dependentDestructuredVariables.ts, 123, 32))
+
+function unrefined1<T>(ab: AB<T>): void {
+>unrefined1 : Symbol(unrefined1, Decl(dependentDestructuredVariables.ts, 123, 54))
+>T : Symbol(T, Decl(dependentDestructuredVariables.ts, 125, 20))
+>ab : Symbol(ab, Decl(dependentDestructuredVariables.ts, 125, 23))
+>AB : Symbol(AB, Decl(dependentDestructuredVariables.ts, 117, 48))
+>T : Symbol(T, Decl(dependentDestructuredVariables.ts, 125, 20))
+
+    const { variant, value } = ab;
+>variant : Symbol(variant, Decl(dependentDestructuredVariables.ts, 126, 11))
+>value : Symbol(value, Decl(dependentDestructuredVariables.ts, 126, 20))
+>ab : Symbol(ab, Decl(dependentDestructuredVariables.ts, 125, 23))
+
+    if (variant === 'a') {
+>variant : Symbol(variant, Decl(dependentDestructuredVariables.ts, 126, 11))
+
+        printValue<T>(value);
+>printValue : Symbol(printValue, Decl(dependentDestructuredVariables.ts, 119, 25))
+>T : Symbol(T, Decl(dependentDestructuredVariables.ts, 125, 20))
+>value : Symbol(value, Decl(dependentDestructuredVariables.ts, 126, 20))
+    }
+    else {
+        printValueList<T>(value);
+>printValueList : Symbol(printValueList, Decl(dependentDestructuredVariables.ts, 121, 43))
+>T : Symbol(T, Decl(dependentDestructuredVariables.ts, 125, 20))
+>value : Symbol(value, Decl(dependentDestructuredVariables.ts, 126, 20))
+    }
+}
+
+// Repro from #38020
+
+type Action3 =
+>Action3 : Symbol(Action3, Decl(dependentDestructuredVariables.ts, 133, 1))
+
+    | {type: 'add', payload: { toAdd: number } }
+>type : Symbol(type, Decl(dependentDestructuredVariables.ts, 138, 7))
+>payload : Symbol(payload, Decl(dependentDestructuredVariables.ts, 138, 19))
+>toAdd : Symbol(toAdd, Decl(dependentDestructuredVariables.ts, 138, 30))
+
+    | {type: 'remove', payload: { toRemove: number } };
+>type : Symbol(type, Decl(dependentDestructuredVariables.ts, 139, 7))
+>payload : Symbol(payload, Decl(dependentDestructuredVariables.ts, 139, 22))
+>toRemove : Symbol(toRemove, Decl(dependentDestructuredVariables.ts, 139, 33))
+
+const reducerBroken = (state: number, { type, payload }: Action3) => {
+>reducerBroken : Symbol(reducerBroken, Decl(dependentDestructuredVariables.ts, 141, 5))
+>state : Symbol(state, Decl(dependentDestructuredVariables.ts, 141, 23))
+>type : Symbol(type, Decl(dependentDestructuredVariables.ts, 141, 39))
+>payload : Symbol(payload, Decl(dependentDestructuredVariables.ts, 141, 45))
+>Action3 : Symbol(Action3, Decl(dependentDestructuredVariables.ts, 133, 1))
+
+    switch (type) {
+>type : Symbol(type, Decl(dependentDestructuredVariables.ts, 141, 39))
+
+        case 'add':
+            return state + payload.toAdd;
+>state : Symbol(state, Decl(dependentDestructuredVariables.ts, 141, 23))
+>payload.toAdd : Symbol(toAdd, Decl(dependentDestructuredVariables.ts, 138, 30))
+>payload : Symbol(payload, Decl(dependentDestructuredVariables.ts, 141, 45))
+>toAdd : Symbol(toAdd, Decl(dependentDestructuredVariables.ts, 138, 30))
+
+        case 'remove':
+            return state - payload.toRemove;
+>state : Symbol(state, Decl(dependentDestructuredVariables.ts, 141, 23))
+>payload.toRemove : Symbol(toRemove, Decl(dependentDestructuredVariables.ts, 139, 33))
+>payload : Symbol(payload, Decl(dependentDestructuredVariables.ts, 141, 45))
+>toRemove : Symbol(toRemove, Decl(dependentDestructuredVariables.ts, 139, 33))
+    }
+}
+
+// Repro from #46143
+
+declare var it: Iterator<number>;
+>it : Symbol(it, Decl(dependentDestructuredVariables.ts, 152, 11))
+>Iterator : Symbol(Iterator, Decl(lib.es2015.iterable.d.ts, --, --))
+
+const { value, done } = it.next();
+>value : Symbol(value, Decl(dependentDestructuredVariables.ts, 153, 7))
+>done : Symbol(done, Decl(dependentDestructuredVariables.ts, 153, 14))
+>it.next : Symbol(Iterator.next, Decl(lib.es2015.iterable.d.ts, --, --))
+>it : Symbol(it, Decl(dependentDestructuredVariables.ts, 152, 11))
+>next : Symbol(Iterator.next, Decl(lib.es2015.iterable.d.ts, --, --))
+
+if (!done) {
+>done : Symbol(done, Decl(dependentDestructuredVariables.ts, 153, 14))
+
+    value;  // number
+>value : Symbol(value, Decl(dependentDestructuredVariables.ts, 153, 7))
+}
+
diff --git a/tests/baselines/reference/dependentDestructuredVariables.types b/tests/baselines/reference/dependentDestructuredVariables.types
new file mode 100644
index 0000000000000..1c8df34341cef
--- /dev/null
+++ b/tests/baselines/reference/dependentDestructuredVariables.types
@@ -0,0 +1,441 @@
+=== tests/cases/conformance/controlFlow/dependentDestructuredVariables.ts ===
+type Action =
+>Action : Action
+
+    | { kind: 'A', payload: number }
+>kind : "A"
+>payload : number
+
+    | { kind: 'B', payload: string };
+>kind : "B"
+>payload : string
+
+function f10({ kind, payload }: Action) {
+>f10 : ({ kind, payload }: Action) => void
+>kind : "A" | "B"
+>payload : string | number
+
+    if (kind === 'A') {
+>kind === 'A' : boolean
+>kind : "A" | "B"
+>'A' : "A"
+
+        payload.toFixed();
+>payload.toFixed() : string
+>payload.toFixed : (fractionDigits?: number | undefined) => string
+>payload : number
+>toFixed : (fractionDigits?: number | undefined) => string
+    }
+    if (kind === 'B') {
+>kind === 'B' : boolean
+>kind : "A" | "B"
+>'B' : "B"
+
+        payload.toUpperCase();
+>payload.toUpperCase() : string
+>payload.toUpperCase : () => string
+>payload : string
+>toUpperCase : () => string
+    }
+}
+
+function f11(action: Action) {
+>f11 : (action: Action) => void
+>action : Action
+
+    const { kind, payload } = action;
+>kind : "A" | "B"
+>payload : string | number
+>action : Action
+
+    if (kind === 'A') {
+>kind === 'A' : boolean
+>kind : "A" | "B"
+>'A' : "A"
+
+        payload.toFixed();
+>payload.toFixed() : string
+>payload.toFixed : (fractionDigits?: number | undefined) => string
+>payload : number
+>toFixed : (fractionDigits?: number | undefined) => string
+    }
+    if (kind === 'B') {
+>kind === 'B' : boolean
+>kind : "A" | "B"
+>'B' : "B"
+
+        payload.toUpperCase();
+>payload.toUpperCase() : string
+>payload.toUpperCase : () => string
+>payload : string
+>toUpperCase : () => string
+    }
+}
+
+function f12({ kind, payload }: Action) {
+>f12 : ({ kind, payload }: Action) => void
+>kind : "A" | "B"
+>payload : string | number
+
+    switch (kind) {
+>kind : "A" | "B"
+
+        case 'A':
+>'A' : "A"
+
+            payload.toFixed();
+>payload.toFixed() : string
+>payload.toFixed : (fractionDigits?: number | undefined) => string
+>payload : number
+>toFixed : (fractionDigits?: number | undefined) => string
+
+            break;
+        case 'B':
+>'B' : "B"
+
+            payload.toUpperCase();
+>payload.toUpperCase() : string
+>payload.toUpperCase : () => string
+>payload : string
+>toUpperCase : () => string
+
+            break;
+        default:
+            payload;  // never
+>payload : never
+    }
+}
+
+type Action2 =
+>Action2 : Action2
+
+    | { kind: 'A', payload: number | undefined }
+>kind : "A"
+>payload : number | undefined
+
+    | { kind: 'B', payload: string | undefined };
+>kind : "B"
+>payload : string | undefined
+
+function f20({ kind, payload }: Action2) {
+>f20 : ({ kind, payload }: Action2) => void
+>kind : "A" | "B"
+>payload : string | number | undefined
+
+    if (payload) {
+>payload : string | number | undefined
+
+        if (kind === 'A') {
+>kind === 'A' : boolean
+>kind : "A" | "B"
+>'A' : "A"
+
+            payload.toFixed();
+>payload.toFixed() : string
+>payload.toFixed : (fractionDigits?: number | undefined) => string
+>payload : number
+>toFixed : (fractionDigits?: number | undefined) => string
+        }
+        if (kind === 'B') {
+>kind === 'B' : boolean
+>kind : "A" | "B"
+>'B' : "B"
+
+            payload.toUpperCase();
+>payload.toUpperCase() : string
+>payload.toUpperCase : () => string
+>payload : string
+>toUpperCase : () => string
+        }
+    }
+}
+
+function f21(action: Action2) {
+>f21 : (action: Action2) => void
+>action : Action2
+
+    const { kind, payload } = action;
+>kind : "A" | "B"
+>payload : string | number | undefined
+>action : Action2
+
+    if (payload) {
+>payload : string | number | undefined
+
+        if (kind === 'A') {
+>kind === 'A' : boolean
+>kind : "A" | "B"
+>'A' : "A"
+
+            payload.toFixed();
+>payload.toFixed() : string
+>payload.toFixed : (fractionDigits?: number | undefined) => string
+>payload : number
+>toFixed : (fractionDigits?: number | undefined) => string
+        }
+        if (kind === 'B') {
+>kind === 'B' : boolean
+>kind : "A" | "B"
+>'B' : "B"
+
+            payload.toUpperCase();
+>payload.toUpperCase() : string
+>payload.toUpperCase : () => string
+>payload : string
+>toUpperCase : () => string
+        }
+    }
+}
+
+function f22(action: Action2) {
+>f22 : (action: Action2) => void
+>action : Action2
+
+    if (action.payload) {
+>action.payload : string | number | undefined
+>action : Action2
+>payload : string | number | undefined
+
+        const { kind, payload } = action;
+>kind : "A" | "B"
+>payload : string | number
+>action : Action2
+
+        if (kind === 'A') {
+>kind === 'A' : boolean
+>kind : "A" | "B"
+>'A' : "A"
+
+            payload.toFixed();
+>payload.toFixed() : string
+>payload.toFixed : (fractionDigits?: number | undefined) => string
+>payload : number
+>toFixed : (fractionDigits?: number | undefined) => string
+        }
+        if (kind === 'B') {
+>kind === 'B' : boolean
+>kind : "A" | "B"
+>'B' : "B"
+
+            payload.toUpperCase();
+>payload.toUpperCase() : string
+>payload.toUpperCase : () => string
+>payload : string
+>toUpperCase : () => string
+        }
+    }
+}
+
+function f23({ kind, payload }: Action2) {
+>f23 : ({ kind, payload }: Action2) => void
+>kind : "A" | "B"
+>payload : string | number | undefined
+
+    if (payload) {
+>payload : string | number | undefined
+
+        switch (kind) {
+>kind : "A" | "B"
+
+            case 'A':
+>'A' : "A"
+
+                payload.toFixed();
+>payload.toFixed() : string
+>payload.toFixed : (fractionDigits?: number | undefined) => string
+>payload : number
+>toFixed : (fractionDigits?: number | undefined) => string
+
+                break;
+            case 'B':
+>'B' : "B"
+
+                payload.toUpperCase();
+>payload.toUpperCase() : string
+>payload.toUpperCase : () => string
+>payload : string
+>toUpperCase : () => string
+
+                break;
+            default:
+                payload;  // never
+>payload : never
+        }
+    }
+}
+
+type Foo =
+>Foo : Foo
+
+    | { kind: 'A', isA: true }
+>kind : "A"
+>isA : true
+>true : true
+
+    | { kind: 'B', isA: false }
+>kind : "B"
+>isA : false
+>false : false
+
+    | { kind: 'C', isA: false };
+>kind : "C"
+>isA : false
+>false : false
+
+function f30({ kind, isA }: Foo) {
+>f30 : ({ kind, isA }: Foo) => void
+>kind : "A" | "B" | "C"
+>isA : boolean
+
+    if (kind === 'A') {
+>kind === 'A' : boolean
+>kind : "A" | "B" | "C"
+>'A' : "A"
+
+        isA;   // true
+>isA : true
+    }
+    if (kind === 'B') {
+>kind === 'B' : boolean
+>kind : "A" | "B" | "C"
+>'B' : "B"
+
+        isA;   // false
+>isA : false
+    }
+    if (kind === 'C') {
+>kind === 'C' : boolean
+>kind : "A" | "B" | "C"
+>'C' : "C"
+
+        isA;   // false
+>isA : false
+    }
+    if (isA) {
+>isA : boolean
+
+        kind;  // 'A'
+>kind : "A"
+    }
+    else {
+        kind;  // 'B' | 'C'
+>kind : "B" | "C"
+    }
+}
+
+// Repro from #35283
+
+interface A<T> { variant: 'a', value: T }
+>variant : "a"
+>value : T
+
+interface B<T> { variant: 'b', value: Array<T> }
+>variant : "b"
+>value : T[]
+
+type AB<T> = A<T> | B<T>;
+>AB : AB<T>
+
+declare function printValue<T>(t: T): void;
+>printValue : <T>(t: T) => void
+>t : T
+
+declare function printValueList<T>(t: Array<T>): void;
+>printValueList : <T>(t: Array<T>) => void
+>t : T[]
+
+function unrefined1<T>(ab: AB<T>): void {
+>unrefined1 : <T>(ab: AB<T>) => void
+>ab : AB<T>
+
+    const { variant, value } = ab;
+>variant : "a" | "b"
+>value : T | T[]
+>ab : AB<T>
+
+    if (variant === 'a') {
+>variant === 'a' : boolean
+>variant : "a" | "b"
+>'a' : "a"
+
+        printValue<T>(value);
+>printValue<T>(value) : void
+>printValue : <T>(t: T) => void
+>value : T
+    }
+    else {
+        printValueList<T>(value);
+>printValueList<T>(value) : void
+>printValueList : <T>(t: T[]) => void
+>value : T[]
+    }
+}
+
+// Repro from #38020
+
+type Action3 =
+>Action3 : Action3
+
+    | {type: 'add', payload: { toAdd: number } }
+>type : "add"
+>payload : { toAdd: number; }
+>toAdd : number
+
+    | {type: 'remove', payload: { toRemove: number } };
+>type : "remove"
+>payload : { toRemove: number; }
+>toRemove : number
+
+const reducerBroken = (state: number, { type, payload }: Action3) => {
+>reducerBroken : (state: number, { type, payload }: Action3) => number
+>(state: number, { type, payload }: Action3) => {    switch (type) {        case 'add':            return state + payload.toAdd;        case 'remove':            return state - payload.toRemove;    }} : (state: number, { type, payload }: Action3) => number
+>state : number
+>type : "add" | "remove"
+>payload : { toAdd: number; } | { toRemove: number; }
+
+    switch (type) {
+>type : "add" | "remove"
+
+        case 'add':
+>'add' : "add"
+
+            return state + payload.toAdd;
+>state + payload.toAdd : number
+>state : number
+>payload.toAdd : number
+>payload : { toAdd: number; }
+>toAdd : number
+
+        case 'remove':
+>'remove' : "remove"
+
+            return state - payload.toRemove;
+>state - payload.toRemove : number
+>state : number
+>payload.toRemove : number
+>payload : { toRemove: number; }
+>toRemove : number
+    }
+}
+
+// Repro from #46143
+
+declare var it: Iterator<number>;
+>it : Iterator<number, any, undefined>
+
+const { value, done } = it.next();
+>value : any
+>done : boolean | undefined
+>it.next() : IteratorResult<number, any>
+>it.next : (...args: [] | [undefined]) => IteratorResult<number, any>
+>it : Iterator<number, any, undefined>
+>next : (...args: [] | [undefined]) => IteratorResult<number, any>
+
+if (!done) {
+>!done : boolean
+>done : boolean | undefined
+
+    value;  // number
+>value : number
+}
+
diff --git a/tests/cases/conformance/controlFlow/dependentDestructuredVariables.ts b/tests/cases/conformance/controlFlow/dependentDestructuredVariables.ts
new file mode 100644
index 0000000000000..55e95ddf09163
--- /dev/null
+++ b/tests/cases/conformance/controlFlow/dependentDestructuredVariables.ts
@@ -0,0 +1,161 @@
+// @strict: true
+// @declaration: true
+// @target: es2015
+
+type Action =
+    | { kind: 'A', payload: number }
+    | { kind: 'B', payload: string };
+
+function f10({ kind, payload }: Action) {
+    if (kind === 'A') {
+        payload.toFixed();
+    }
+    if (kind === 'B') {
+        payload.toUpperCase();
+    }
+}
+
+function f11(action: Action) {
+    const { kind, payload } = action;
+    if (kind === 'A') {
+        payload.toFixed();
+    }
+    if (kind === 'B') {
+        payload.toUpperCase();
+    }
+}
+
+function f12({ kind, payload }: Action) {
+    switch (kind) {
+        case 'A':
+            payload.toFixed();
+            break;
+        case 'B':
+            payload.toUpperCase();
+            break;
+        default:
+            payload;  // never
+    }
+}
+
+type Action2 =
+    | { kind: 'A', payload: number | undefined }
+    | { kind: 'B', payload: string | undefined };
+
+function f20({ kind, payload }: Action2) {
+    if (payload) {
+        if (kind === 'A') {
+            payload.toFixed();
+        }
+        if (kind === 'B') {
+            payload.toUpperCase();
+        }
+    }
+}
+
+function f21(action: Action2) {
+    const { kind, payload } = action;
+    if (payload) {
+        if (kind === 'A') {
+            payload.toFixed();
+        }
+        if (kind === 'B') {
+            payload.toUpperCase();
+        }
+    }
+}
+
+function f22(action: Action2) {
+    if (action.payload) {
+        const { kind, payload } = action;
+        if (kind === 'A') {
+            payload.toFixed();
+        }
+        if (kind === 'B') {
+            payload.toUpperCase();
+        }
+    }
+}
+
+function f23({ kind, payload }: Action2) {
+    if (payload) {
+        switch (kind) {
+            case 'A':
+                payload.toFixed();
+                break;
+            case 'B':
+                payload.toUpperCase();
+                break;
+            default:
+                payload;  // never
+        }
+    }
+}
+
+type Foo =
+    | { kind: 'A', isA: true }
+    | { kind: 'B', isA: false }
+    | { kind: 'C', isA: false };
+
+function f30({ kind, isA }: Foo) {
+    if (kind === 'A') {
+        isA;   // true
+    }
+    if (kind === 'B') {
+        isA;   // false
+    }
+    if (kind === 'C') {
+        isA;   // false
+    }
+    if (isA) {
+        kind;  // 'A'
+    }
+    else {
+        kind;  // 'B' | 'C'
+    }
+}
+
+// Repro from #35283
+
+interface A<T> { variant: 'a', value: T }
+
+interface B<T> { variant: 'b', value: Array<T> }
+
+type AB<T> = A<T> | B<T>;
+
+declare function printValue<T>(t: T): void;
+
+declare function printValueList<T>(t: Array<T>): void;
+
+function unrefined1<T>(ab: AB<T>): void {
+    const { variant, value } = ab;
+    if (variant === 'a') {
+        printValue<T>(value);
+    }
+    else {
+        printValueList<T>(value);
+    }
+}
+
+// Repro from #38020
+
+type Action3 =
+    | {type: 'add', payload: { toAdd: number } }
+    | {type: 'remove', payload: { toRemove: number } };
+
+const reducerBroken = (state: number, { type, payload }: Action3) => {
+    switch (type) {
+        case 'add':
+            return state + payload.toAdd;
+        case 'remove':
+            return state - payload.toRemove;
+    }
+}
+
+// Repro from #46143
+
+declare var it: Iterator<number>;
+const { value, done } = it.next();
+if (!done) {
+    value;  // number
+}