diff --git a/tests/baselines/reference/discriminatedUnionTypes1.js b/tests/baselines/reference/discriminatedUnionTypes1.js
new file mode 100644
index 00000000000..8679689569a
--- /dev/null
+++ b/tests/baselines/reference/discriminatedUnionTypes1.js
@@ -0,0 +1,252 @@
+//// [discriminatedUnionTypes1.ts]
+interface Square {
+    kind: "square";
+    size: number;
+}
+
+interface Rectangle {
+    kind: "rectangle";
+    width: number;
+    height: number;
+}
+
+interface Circle {
+    kind: "circle";
+    radius: number;
+}
+
+type Shape = Square | Rectangle | Circle;
+
+function area1(s: Shape) {
+    if (s.kind === "square") {
+        return s.size * s.size;
+    }
+    else if (s.kind === "circle") {
+        return Math.PI * s.radius * s.radius;
+    }
+    else if (s.kind === "rectangle") {
+        return s.width * s.height;
+    }
+    else {
+        return 0;
+    }
+}
+
+function area2(s: Shape) {
+    switch (s.kind) {
+        case "square": return s.size * s.size;
+        case "rectangle": return s.width * s.height;
+        case "circle": return Math.PI * s.radius * s.radius;
+    }
+}
+
+function assertNever(x: never): never {
+    throw new Error("Unexpected object: " + x);
+}
+
+function area3(s: Shape) {
+    switch (s.kind) {
+        case "square": return s.size * s.size;
+        case "rectangle": return s.width * s.height;
+        case "circle": return Math.PI * s.radius * s.radius;
+        default: return assertNever(s);
+    }
+}
+
+function area4(s: Shape) {
+    switch (s.kind) {
+        case "square": return s.size * s.size;
+        case "rectangle": return s.width * s.height;
+        case "circle": return Math.PI * s.radius * s.radius;
+    }
+    return assertNever(s);
+}
+
+type Message =
+    { kind: "A", x: string } |
+    { kind: "B" | "C", y: number } |
+    { kind: "D" };
+
+function f1(m: Message) {
+    if (m.kind === "A") {
+        m;  // { kind: "A", x: string }
+    }
+    else if (m.kind === "D") {
+        m;  // { kind: "D" }
+    }
+    else {
+        m;  // { kind: "B" | "C", y: number }
+    }
+}
+
+function f2(m: Message) {
+    if (m.kind === "A") {
+        return;
+    }
+    m;  // { kind: "B" | "C", y: number } | { kind: "D" }
+}
+
+function f3(m: Message) {
+    if (m.kind === "X") {
+        m;  // never
+    }
+}
+
+function f4(m: Message, x: "A" | "D") {
+    if (m.kind == x) {
+        m;  // { kind: "A", x: string } | { kind: "D" }
+    }
+}
+
+function f5(m: Message) {
+    switch (m.kind) {
+        case "A":
+            m;  // { kind: "A", x: string }
+            break;
+        case "D":
+            m;  // { kind: "D" }
+            break;
+        default:
+            m;  // { kind: "B" | "C", y: number }
+    }
+}
+
+function f6(m: Message) {
+    switch (m.kind) {
+        case "A":
+            m;  // { kind: "A", x: string }
+        case "D":
+            m;  // { kind: "A", x: string } | { kind: "D" }
+            break;
+        default:
+            m;  // { kind: "B" | "C", y: number }
+    }
+}
+
+function f7(m: Message) {
+    switch (m.kind) {
+        case "A":
+        case "B":
+            return;
+    }
+    m;  // { kind: "B" | "C", y: number } | { kind: "D" }
+}
+
+function f8(m: Message) {
+    switch (m.kind) {
+        case "A":
+            return;
+        case "D":
+            throw new Error();
+    }
+    m;  // { kind: "B" | "C", y: number }
+}
+
+//// [discriminatedUnionTypes1.js]
+function area1(s) {
+    if (s.kind === "square") {
+        return s.size * s.size;
+    }
+    else if (s.kind === "circle") {
+        return Math.PI * s.radius * s.radius;
+    }
+    else if (s.kind === "rectangle") {
+        return s.width * s.height;
+    }
+    else {
+        return 0;
+    }
+}
+function area2(s) {
+    switch (s.kind) {
+        case "square": return s.size * s.size;
+        case "rectangle": return s.width * s.height;
+        case "circle": return Math.PI * s.radius * s.radius;
+    }
+}
+function assertNever(x) {
+    throw new Error("Unexpected object: " + x);
+}
+function area3(s) {
+    switch (s.kind) {
+        case "square": return s.size * s.size;
+        case "rectangle": return s.width * s.height;
+        case "circle": return Math.PI * s.radius * s.radius;
+        default: return assertNever(s);
+    }
+}
+function area4(s) {
+    switch (s.kind) {
+        case "square": return s.size * s.size;
+        case "rectangle": return s.width * s.height;
+        case "circle": return Math.PI * s.radius * s.radius;
+    }
+    return assertNever(s);
+}
+function f1(m) {
+    if (m.kind === "A") {
+        m; // { kind: "A", x: string }
+    }
+    else if (m.kind === "D") {
+        m; // { kind: "D" }
+    }
+    else {
+        m; // { kind: "B" | "C", y: number }
+    }
+}
+function f2(m) {
+    if (m.kind === "A") {
+        return;
+    }
+    m; // { kind: "B" | "C", y: number } | { kind: "D" }
+}
+function f3(m) {
+    if (m.kind === "X") {
+        m; // never
+    }
+}
+function f4(m, x) {
+    if (m.kind == x) {
+        m; // { kind: "A", x: string } | { kind: "D" }
+    }
+}
+function f5(m) {
+    switch (m.kind) {
+        case "A":
+            m; // { kind: "A", x: string }
+            break;
+        case "D":
+            m; // { kind: "D" }
+            break;
+        default:
+            m; // { kind: "B" | "C", y: number }
+    }
+}
+function f6(m) {
+    switch (m.kind) {
+        case "A":
+            m; // { kind: "A", x: string }
+        case "D":
+            m; // { kind: "A", x: string } | { kind: "D" }
+            break;
+        default:
+            m; // { kind: "B" | "C", y: number }
+    }
+}
+function f7(m) {
+    switch (m.kind) {
+        case "A":
+        case "B":
+            return;
+    }
+    m; // { kind: "B" | "C", y: number } | { kind: "D" }
+}
+function f8(m) {
+    switch (m.kind) {
+        case "A":
+            return;
+        case "D":
+            throw new Error();
+    }
+    m; // { kind: "B" | "C", y: number }
+}
diff --git a/tests/baselines/reference/discriminatedUnionTypes1.symbols b/tests/baselines/reference/discriminatedUnionTypes1.symbols
new file mode 100644
index 00000000000..38069447423
--- /dev/null
+++ b/tests/baselines/reference/discriminatedUnionTypes1.symbols
@@ -0,0 +1,402 @@
+=== tests/cases/conformance/types/union/discriminatedUnionTypes1.ts ===
+interface Square {
+>Square : Symbol(Square, Decl(discriminatedUnionTypes1.ts, 0, 0))
+
+    kind: "square";
+>kind : Symbol(Square.kind, Decl(discriminatedUnionTypes1.ts, 0, 18))
+
+    size: number;
+>size : Symbol(Square.size, Decl(discriminatedUnionTypes1.ts, 1, 19))
+}
+
+interface Rectangle {
+>Rectangle : Symbol(Rectangle, Decl(discriminatedUnionTypes1.ts, 3, 1))
+
+    kind: "rectangle";
+>kind : Symbol(Rectangle.kind, Decl(discriminatedUnionTypes1.ts, 5, 21))
+
+    width: number;
+>width : Symbol(Rectangle.width, Decl(discriminatedUnionTypes1.ts, 6, 22))
+
+    height: number;
+>height : Symbol(Rectangle.height, Decl(discriminatedUnionTypes1.ts, 7, 18))
+}
+
+interface Circle {
+>Circle : Symbol(Circle, Decl(discriminatedUnionTypes1.ts, 9, 1))
+
+    kind: "circle";
+>kind : Symbol(Circle.kind, Decl(discriminatedUnionTypes1.ts, 11, 18))
+
+    radius: number;
+>radius : Symbol(Circle.radius, Decl(discriminatedUnionTypes1.ts, 12, 19))
+}
+
+type Shape = Square | Rectangle | Circle;
+>Shape : Symbol(Shape, Decl(discriminatedUnionTypes1.ts, 14, 1))
+>Square : Symbol(Square, Decl(discriminatedUnionTypes1.ts, 0, 0))
+>Rectangle : Symbol(Rectangle, Decl(discriminatedUnionTypes1.ts, 3, 1))
+>Circle : Symbol(Circle, Decl(discriminatedUnionTypes1.ts, 9, 1))
+
+function area1(s: Shape) {
+>area1 : Symbol(area1, Decl(discriminatedUnionTypes1.ts, 16, 41))
+>s : Symbol(s, Decl(discriminatedUnionTypes1.ts, 18, 15))
+>Shape : Symbol(Shape, Decl(discriminatedUnionTypes1.ts, 14, 1))
+
+    if (s.kind === "square") {
+>s.kind : Symbol(kind, Decl(discriminatedUnionTypes1.ts, 0, 18), Decl(discriminatedUnionTypes1.ts, 5, 21), Decl(discriminatedUnionTypes1.ts, 11, 18))
+>s : Symbol(s, Decl(discriminatedUnionTypes1.ts, 18, 15))
+>kind : Symbol(kind, Decl(discriminatedUnionTypes1.ts, 0, 18), Decl(discriminatedUnionTypes1.ts, 5, 21), Decl(discriminatedUnionTypes1.ts, 11, 18))
+
+        return s.size * s.size;
+>s.size : Symbol(Square.size, Decl(discriminatedUnionTypes1.ts, 1, 19))
+>s : Symbol(s, Decl(discriminatedUnionTypes1.ts, 18, 15))
+>size : Symbol(Square.size, Decl(discriminatedUnionTypes1.ts, 1, 19))
+>s.size : Symbol(Square.size, Decl(discriminatedUnionTypes1.ts, 1, 19))
+>s : Symbol(s, Decl(discriminatedUnionTypes1.ts, 18, 15))
+>size : Symbol(Square.size, Decl(discriminatedUnionTypes1.ts, 1, 19))
+    }
+    else if (s.kind === "circle") {
+>s.kind : Symbol(kind, Decl(discriminatedUnionTypes1.ts, 5, 21), Decl(discriminatedUnionTypes1.ts, 11, 18))
+>s : Symbol(s, Decl(discriminatedUnionTypes1.ts, 18, 15))
+>kind : Symbol(kind, Decl(discriminatedUnionTypes1.ts, 5, 21), Decl(discriminatedUnionTypes1.ts, 11, 18))
+
+        return Math.PI * s.radius * s.radius;
+>Math.PI : Symbol(Math.PI, Decl(lib.d.ts, --, --))
+>Math : Symbol(Math, Decl(lib.d.ts, --, --), Decl(lib.d.ts, --, --))
+>PI : Symbol(Math.PI, Decl(lib.d.ts, --, --))
+>s.radius : Symbol(Circle.radius, Decl(discriminatedUnionTypes1.ts, 12, 19))
+>s : Symbol(s, Decl(discriminatedUnionTypes1.ts, 18, 15))
+>radius : Symbol(Circle.radius, Decl(discriminatedUnionTypes1.ts, 12, 19))
+>s.radius : Symbol(Circle.radius, Decl(discriminatedUnionTypes1.ts, 12, 19))
+>s : Symbol(s, Decl(discriminatedUnionTypes1.ts, 18, 15))
+>radius : Symbol(Circle.radius, Decl(discriminatedUnionTypes1.ts, 12, 19))
+    }
+    else if (s.kind === "rectangle") {
+>s.kind : Symbol(Rectangle.kind, Decl(discriminatedUnionTypes1.ts, 5, 21))
+>s : Symbol(s, Decl(discriminatedUnionTypes1.ts, 18, 15))
+>kind : Symbol(Rectangle.kind, Decl(discriminatedUnionTypes1.ts, 5, 21))
+
+        return s.width * s.height;
+>s.width : Symbol(Rectangle.width, Decl(discriminatedUnionTypes1.ts, 6, 22))
+>s : Symbol(s, Decl(discriminatedUnionTypes1.ts, 18, 15))
+>width : Symbol(Rectangle.width, Decl(discriminatedUnionTypes1.ts, 6, 22))
+>s.height : Symbol(Rectangle.height, Decl(discriminatedUnionTypes1.ts, 7, 18))
+>s : Symbol(s, Decl(discriminatedUnionTypes1.ts, 18, 15))
+>height : Symbol(Rectangle.height, Decl(discriminatedUnionTypes1.ts, 7, 18))
+    }
+    else {
+        return 0;
+    }
+}
+
+function area2(s: Shape) {
+>area2 : Symbol(area2, Decl(discriminatedUnionTypes1.ts, 31, 1))
+>s : Symbol(s, Decl(discriminatedUnionTypes1.ts, 33, 15))
+>Shape : Symbol(Shape, Decl(discriminatedUnionTypes1.ts, 14, 1))
+
+    switch (s.kind) {
+>s.kind : Symbol(kind, Decl(discriminatedUnionTypes1.ts, 0, 18), Decl(discriminatedUnionTypes1.ts, 5, 21), Decl(discriminatedUnionTypes1.ts, 11, 18))
+>s : Symbol(s, Decl(discriminatedUnionTypes1.ts, 33, 15))
+>kind : Symbol(kind, Decl(discriminatedUnionTypes1.ts, 0, 18), Decl(discriminatedUnionTypes1.ts, 5, 21), Decl(discriminatedUnionTypes1.ts, 11, 18))
+
+        case "square": return s.size * s.size;
+>s.size : Symbol(Square.size, Decl(discriminatedUnionTypes1.ts, 1, 19))
+>s : Symbol(s, Decl(discriminatedUnionTypes1.ts, 33, 15))
+>size : Symbol(Square.size, Decl(discriminatedUnionTypes1.ts, 1, 19))
+>s.size : Symbol(Square.size, Decl(discriminatedUnionTypes1.ts, 1, 19))
+>s : Symbol(s, Decl(discriminatedUnionTypes1.ts, 33, 15))
+>size : Symbol(Square.size, Decl(discriminatedUnionTypes1.ts, 1, 19))
+
+        case "rectangle": return s.width * s.height;
+>s.width : Symbol(Rectangle.width, Decl(discriminatedUnionTypes1.ts, 6, 22))
+>s : Symbol(s, Decl(discriminatedUnionTypes1.ts, 33, 15))
+>width : Symbol(Rectangle.width, Decl(discriminatedUnionTypes1.ts, 6, 22))
+>s.height : Symbol(Rectangle.height, Decl(discriminatedUnionTypes1.ts, 7, 18))
+>s : Symbol(s, Decl(discriminatedUnionTypes1.ts, 33, 15))
+>height : Symbol(Rectangle.height, Decl(discriminatedUnionTypes1.ts, 7, 18))
+
+        case "circle": return Math.PI * s.radius * s.radius;
+>Math.PI : Symbol(Math.PI, Decl(lib.d.ts, --, --))
+>Math : Symbol(Math, Decl(lib.d.ts, --, --), Decl(lib.d.ts, --, --))
+>PI : Symbol(Math.PI, Decl(lib.d.ts, --, --))
+>s.radius : Symbol(Circle.radius, Decl(discriminatedUnionTypes1.ts, 12, 19))
+>s : Symbol(s, Decl(discriminatedUnionTypes1.ts, 33, 15))
+>radius : Symbol(Circle.radius, Decl(discriminatedUnionTypes1.ts, 12, 19))
+>s.radius : Symbol(Circle.radius, Decl(discriminatedUnionTypes1.ts, 12, 19))
+>s : Symbol(s, Decl(discriminatedUnionTypes1.ts, 33, 15))
+>radius : Symbol(Circle.radius, Decl(discriminatedUnionTypes1.ts, 12, 19))
+    }
+}
+
+function assertNever(x: never): never {
+>assertNever : Symbol(assertNever, Decl(discriminatedUnionTypes1.ts, 39, 1))
+>x : Symbol(x, Decl(discriminatedUnionTypes1.ts, 41, 21))
+
+    throw new Error("Unexpected object: " + x);
+>Error : Symbol(Error, Decl(lib.d.ts, --, --), Decl(lib.d.ts, --, --))
+>x : Symbol(x, Decl(discriminatedUnionTypes1.ts, 41, 21))
+}
+
+function area3(s: Shape) {
+>area3 : Symbol(area3, Decl(discriminatedUnionTypes1.ts, 43, 1))
+>s : Symbol(s, Decl(discriminatedUnionTypes1.ts, 45, 15))
+>Shape : Symbol(Shape, Decl(discriminatedUnionTypes1.ts, 14, 1))
+
+    switch (s.kind) {
+>s.kind : Symbol(kind, Decl(discriminatedUnionTypes1.ts, 0, 18), Decl(discriminatedUnionTypes1.ts, 5, 21), Decl(discriminatedUnionTypes1.ts, 11, 18))
+>s : Symbol(s, Decl(discriminatedUnionTypes1.ts, 45, 15))
+>kind : Symbol(kind, Decl(discriminatedUnionTypes1.ts, 0, 18), Decl(discriminatedUnionTypes1.ts, 5, 21), Decl(discriminatedUnionTypes1.ts, 11, 18))
+
+        case "square": return s.size * s.size;
+>s.size : Symbol(Square.size, Decl(discriminatedUnionTypes1.ts, 1, 19))
+>s : Symbol(s, Decl(discriminatedUnionTypes1.ts, 45, 15))
+>size : Symbol(Square.size, Decl(discriminatedUnionTypes1.ts, 1, 19))
+>s.size : Symbol(Square.size, Decl(discriminatedUnionTypes1.ts, 1, 19))
+>s : Symbol(s, Decl(discriminatedUnionTypes1.ts, 45, 15))
+>size : Symbol(Square.size, Decl(discriminatedUnionTypes1.ts, 1, 19))
+
+        case "rectangle": return s.width * s.height;
+>s.width : Symbol(Rectangle.width, Decl(discriminatedUnionTypes1.ts, 6, 22))
+>s : Symbol(s, Decl(discriminatedUnionTypes1.ts, 45, 15))
+>width : Symbol(Rectangle.width, Decl(discriminatedUnionTypes1.ts, 6, 22))
+>s.height : Symbol(Rectangle.height, Decl(discriminatedUnionTypes1.ts, 7, 18))
+>s : Symbol(s, Decl(discriminatedUnionTypes1.ts, 45, 15))
+>height : Symbol(Rectangle.height, Decl(discriminatedUnionTypes1.ts, 7, 18))
+
+        case "circle": return Math.PI * s.radius * s.radius;
+>Math.PI : Symbol(Math.PI, Decl(lib.d.ts, --, --))
+>Math : Symbol(Math, Decl(lib.d.ts, --, --), Decl(lib.d.ts, --, --))
+>PI : Symbol(Math.PI, Decl(lib.d.ts, --, --))
+>s.radius : Symbol(Circle.radius, Decl(discriminatedUnionTypes1.ts, 12, 19))
+>s : Symbol(s, Decl(discriminatedUnionTypes1.ts, 45, 15))
+>radius : Symbol(Circle.radius, Decl(discriminatedUnionTypes1.ts, 12, 19))
+>s.radius : Symbol(Circle.radius, Decl(discriminatedUnionTypes1.ts, 12, 19))
+>s : Symbol(s, Decl(discriminatedUnionTypes1.ts, 45, 15))
+>radius : Symbol(Circle.radius, Decl(discriminatedUnionTypes1.ts, 12, 19))
+
+        default: return assertNever(s);
+>assertNever : Symbol(assertNever, Decl(discriminatedUnionTypes1.ts, 39, 1))
+>s : Symbol(s, Decl(discriminatedUnionTypes1.ts, 45, 15))
+    }
+}
+
+function area4(s: Shape) {
+>area4 : Symbol(area4, Decl(discriminatedUnionTypes1.ts, 52, 1))
+>s : Symbol(s, Decl(discriminatedUnionTypes1.ts, 54, 15))
+>Shape : Symbol(Shape, Decl(discriminatedUnionTypes1.ts, 14, 1))
+
+    switch (s.kind) {
+>s.kind : Symbol(kind, Decl(discriminatedUnionTypes1.ts, 0, 18), Decl(discriminatedUnionTypes1.ts, 5, 21), Decl(discriminatedUnionTypes1.ts, 11, 18))
+>s : Symbol(s, Decl(discriminatedUnionTypes1.ts, 54, 15))
+>kind : Symbol(kind, Decl(discriminatedUnionTypes1.ts, 0, 18), Decl(discriminatedUnionTypes1.ts, 5, 21), Decl(discriminatedUnionTypes1.ts, 11, 18))
+
+        case "square": return s.size * s.size;
+>s.size : Symbol(Square.size, Decl(discriminatedUnionTypes1.ts, 1, 19))
+>s : Symbol(s, Decl(discriminatedUnionTypes1.ts, 54, 15))
+>size : Symbol(Square.size, Decl(discriminatedUnionTypes1.ts, 1, 19))
+>s.size : Symbol(Square.size, Decl(discriminatedUnionTypes1.ts, 1, 19))
+>s : Symbol(s, Decl(discriminatedUnionTypes1.ts, 54, 15))
+>size : Symbol(Square.size, Decl(discriminatedUnionTypes1.ts, 1, 19))
+
+        case "rectangle": return s.width * s.height;
+>s.width : Symbol(Rectangle.width, Decl(discriminatedUnionTypes1.ts, 6, 22))
+>s : Symbol(s, Decl(discriminatedUnionTypes1.ts, 54, 15))
+>width : Symbol(Rectangle.width, Decl(discriminatedUnionTypes1.ts, 6, 22))
+>s.height : Symbol(Rectangle.height, Decl(discriminatedUnionTypes1.ts, 7, 18))
+>s : Symbol(s, Decl(discriminatedUnionTypes1.ts, 54, 15))
+>height : Symbol(Rectangle.height, Decl(discriminatedUnionTypes1.ts, 7, 18))
+
+        case "circle": return Math.PI * s.radius * s.radius;
+>Math.PI : Symbol(Math.PI, Decl(lib.d.ts, --, --))
+>Math : Symbol(Math, Decl(lib.d.ts, --, --), Decl(lib.d.ts, --, --))
+>PI : Symbol(Math.PI, Decl(lib.d.ts, --, --))
+>s.radius : Symbol(Circle.radius, Decl(discriminatedUnionTypes1.ts, 12, 19))
+>s : Symbol(s, Decl(discriminatedUnionTypes1.ts, 54, 15))
+>radius : Symbol(Circle.radius, Decl(discriminatedUnionTypes1.ts, 12, 19))
+>s.radius : Symbol(Circle.radius, Decl(discriminatedUnionTypes1.ts, 12, 19))
+>s : Symbol(s, Decl(discriminatedUnionTypes1.ts, 54, 15))
+>radius : Symbol(Circle.radius, Decl(discriminatedUnionTypes1.ts, 12, 19))
+    }
+    return assertNever(s);
+>assertNever : Symbol(assertNever, Decl(discriminatedUnionTypes1.ts, 39, 1))
+>s : Symbol(s, Decl(discriminatedUnionTypes1.ts, 54, 15))
+}
+
+type Message =
+>Message : Symbol(Message, Decl(discriminatedUnionTypes1.ts, 61, 1))
+
+    { kind: "A", x: string } |
+>kind : Symbol(kind, Decl(discriminatedUnionTypes1.ts, 64, 5))
+>x : Symbol(x, Decl(discriminatedUnionTypes1.ts, 64, 16))
+
+    { kind: "B" | "C", y: number } |
+>kind : Symbol(kind, Decl(discriminatedUnionTypes1.ts, 65, 5))
+>y : Symbol(y, Decl(discriminatedUnionTypes1.ts, 65, 22))
+
+    { kind: "D" };
+>kind : Symbol(kind, Decl(discriminatedUnionTypes1.ts, 66, 5))
+
+function f1(m: Message) {
+>f1 : Symbol(f1, Decl(discriminatedUnionTypes1.ts, 66, 18))
+>m : Symbol(m, Decl(discriminatedUnionTypes1.ts, 68, 12))
+>Message : Symbol(Message, Decl(discriminatedUnionTypes1.ts, 61, 1))
+
+    if (m.kind === "A") {
+>m.kind : Symbol(kind, Decl(discriminatedUnionTypes1.ts, 64, 5), Decl(discriminatedUnionTypes1.ts, 65, 5), Decl(discriminatedUnionTypes1.ts, 66, 5))
+>m : Symbol(m, Decl(discriminatedUnionTypes1.ts, 68, 12))
+>kind : Symbol(kind, Decl(discriminatedUnionTypes1.ts, 64, 5), Decl(discriminatedUnionTypes1.ts, 65, 5), Decl(discriminatedUnionTypes1.ts, 66, 5))
+
+        m;  // { kind: "A", x: string }
+>m : Symbol(m, Decl(discriminatedUnionTypes1.ts, 68, 12))
+    }
+    else if (m.kind === "D") {
+>m.kind : Symbol(kind, Decl(discriminatedUnionTypes1.ts, 65, 5), Decl(discriminatedUnionTypes1.ts, 66, 5))
+>m : Symbol(m, Decl(discriminatedUnionTypes1.ts, 68, 12))
+>kind : Symbol(kind, Decl(discriminatedUnionTypes1.ts, 65, 5), Decl(discriminatedUnionTypes1.ts, 66, 5))
+
+        m;  // { kind: "D" }
+>m : Symbol(m, Decl(discriminatedUnionTypes1.ts, 68, 12))
+    }
+    else {
+        m;  // { kind: "B" | "C", y: number }
+>m : Symbol(m, Decl(discriminatedUnionTypes1.ts, 68, 12))
+    }
+}
+
+function f2(m: Message) {
+>f2 : Symbol(f2, Decl(discriminatedUnionTypes1.ts, 78, 1))
+>m : Symbol(m, Decl(discriminatedUnionTypes1.ts, 80, 12))
+>Message : Symbol(Message, Decl(discriminatedUnionTypes1.ts, 61, 1))
+
+    if (m.kind === "A") {
+>m.kind : Symbol(kind, Decl(discriminatedUnionTypes1.ts, 64, 5), Decl(discriminatedUnionTypes1.ts, 65, 5), Decl(discriminatedUnionTypes1.ts, 66, 5))
+>m : Symbol(m, Decl(discriminatedUnionTypes1.ts, 80, 12))
+>kind : Symbol(kind, Decl(discriminatedUnionTypes1.ts, 64, 5), Decl(discriminatedUnionTypes1.ts, 65, 5), Decl(discriminatedUnionTypes1.ts, 66, 5))
+
+        return;
+    }
+    m;  // { kind: "B" | "C", y: number } | { kind: "D" }
+>m : Symbol(m, Decl(discriminatedUnionTypes1.ts, 80, 12))
+}
+
+function f3(m: Message) {
+>f3 : Symbol(f3, Decl(discriminatedUnionTypes1.ts, 85, 1))
+>m : Symbol(m, Decl(discriminatedUnionTypes1.ts, 87, 12))
+>Message : Symbol(Message, Decl(discriminatedUnionTypes1.ts, 61, 1))
+
+    if (m.kind === "X") {
+>m.kind : Symbol(kind, Decl(discriminatedUnionTypes1.ts, 64, 5), Decl(discriminatedUnionTypes1.ts, 65, 5), Decl(discriminatedUnionTypes1.ts, 66, 5))
+>m : Symbol(m, Decl(discriminatedUnionTypes1.ts, 87, 12))
+>kind : Symbol(kind, Decl(discriminatedUnionTypes1.ts, 64, 5), Decl(discriminatedUnionTypes1.ts, 65, 5), Decl(discriminatedUnionTypes1.ts, 66, 5))
+
+        m;  // never
+>m : Symbol(m, Decl(discriminatedUnionTypes1.ts, 87, 12))
+    }
+}
+
+function f4(m: Message, x: "A" | "D") {
+>f4 : Symbol(f4, Decl(discriminatedUnionTypes1.ts, 91, 1))
+>m : Symbol(m, Decl(discriminatedUnionTypes1.ts, 93, 12))
+>Message : Symbol(Message, Decl(discriminatedUnionTypes1.ts, 61, 1))
+>x : Symbol(x, Decl(discriminatedUnionTypes1.ts, 93, 23))
+
+    if (m.kind == x) {
+>m.kind : Symbol(kind, Decl(discriminatedUnionTypes1.ts, 64, 5), Decl(discriminatedUnionTypes1.ts, 65, 5), Decl(discriminatedUnionTypes1.ts, 66, 5))
+>m : Symbol(m, Decl(discriminatedUnionTypes1.ts, 93, 12))
+>kind : Symbol(kind, Decl(discriminatedUnionTypes1.ts, 64, 5), Decl(discriminatedUnionTypes1.ts, 65, 5), Decl(discriminatedUnionTypes1.ts, 66, 5))
+>x : Symbol(x, Decl(discriminatedUnionTypes1.ts, 93, 23))
+
+        m;  // { kind: "A", x: string } | { kind: "D" }
+>m : Symbol(m, Decl(discriminatedUnionTypes1.ts, 93, 12))
+    }
+}
+
+function f5(m: Message) {
+>f5 : Symbol(f5, Decl(discriminatedUnionTypes1.ts, 97, 1))
+>m : Symbol(m, Decl(discriminatedUnionTypes1.ts, 99, 12))
+>Message : Symbol(Message, Decl(discriminatedUnionTypes1.ts, 61, 1))
+
+    switch (m.kind) {
+>m.kind : Symbol(kind, Decl(discriminatedUnionTypes1.ts, 64, 5), Decl(discriminatedUnionTypes1.ts, 65, 5), Decl(discriminatedUnionTypes1.ts, 66, 5))
+>m : Symbol(m, Decl(discriminatedUnionTypes1.ts, 99, 12))
+>kind : Symbol(kind, Decl(discriminatedUnionTypes1.ts, 64, 5), Decl(discriminatedUnionTypes1.ts, 65, 5), Decl(discriminatedUnionTypes1.ts, 66, 5))
+
+        case "A":
+            m;  // { kind: "A", x: string }
+>m : Symbol(m, Decl(discriminatedUnionTypes1.ts, 99, 12))
+
+            break;
+        case "D":
+            m;  // { kind: "D" }
+>m : Symbol(m, Decl(discriminatedUnionTypes1.ts, 99, 12))
+
+            break;
+        default:
+            m;  // { kind: "B" | "C", y: number }
+>m : Symbol(m, Decl(discriminatedUnionTypes1.ts, 99, 12))
+    }
+}
+
+function f6(m: Message) {
+>f6 : Symbol(f6, Decl(discriminatedUnionTypes1.ts, 110, 1))
+>m : Symbol(m, Decl(discriminatedUnionTypes1.ts, 112, 12))
+>Message : Symbol(Message, Decl(discriminatedUnionTypes1.ts, 61, 1))
+
+    switch (m.kind) {
+>m.kind : Symbol(kind, Decl(discriminatedUnionTypes1.ts, 64, 5), Decl(discriminatedUnionTypes1.ts, 65, 5), Decl(discriminatedUnionTypes1.ts, 66, 5))
+>m : Symbol(m, Decl(discriminatedUnionTypes1.ts, 112, 12))
+>kind : Symbol(kind, Decl(discriminatedUnionTypes1.ts, 64, 5), Decl(discriminatedUnionTypes1.ts, 65, 5), Decl(discriminatedUnionTypes1.ts, 66, 5))
+
+        case "A":
+            m;  // { kind: "A", x: string }
+>m : Symbol(m, Decl(discriminatedUnionTypes1.ts, 112, 12))
+
+        case "D":
+            m;  // { kind: "A", x: string } | { kind: "D" }
+>m : Symbol(m, Decl(discriminatedUnionTypes1.ts, 112, 12))
+
+            break;
+        default:
+            m;  // { kind: "B" | "C", y: number }
+>m : Symbol(m, Decl(discriminatedUnionTypes1.ts, 112, 12))
+    }
+}
+
+function f7(m: Message) {
+>f7 : Symbol(f7, Decl(discriminatedUnionTypes1.ts, 122, 1))
+>m : Symbol(m, Decl(discriminatedUnionTypes1.ts, 124, 12))
+>Message : Symbol(Message, Decl(discriminatedUnionTypes1.ts, 61, 1))
+
+    switch (m.kind) {
+>m.kind : Symbol(kind, Decl(discriminatedUnionTypes1.ts, 64, 5), Decl(discriminatedUnionTypes1.ts, 65, 5), Decl(discriminatedUnionTypes1.ts, 66, 5))
+>m : Symbol(m, Decl(discriminatedUnionTypes1.ts, 124, 12))
+>kind : Symbol(kind, Decl(discriminatedUnionTypes1.ts, 64, 5), Decl(discriminatedUnionTypes1.ts, 65, 5), Decl(discriminatedUnionTypes1.ts, 66, 5))
+
+        case "A":
+        case "B":
+            return;
+    }
+    m;  // { kind: "B" | "C", y: number } | { kind: "D" }
+>m : Symbol(m, Decl(discriminatedUnionTypes1.ts, 124, 12))
+}
+
+function f8(m: Message) {
+>f8 : Symbol(f8, Decl(discriminatedUnionTypes1.ts, 131, 1))
+>m : Symbol(m, Decl(discriminatedUnionTypes1.ts, 133, 12))
+>Message : Symbol(Message, Decl(discriminatedUnionTypes1.ts, 61, 1))
+
+    switch (m.kind) {
+>m.kind : Symbol(kind, Decl(discriminatedUnionTypes1.ts, 64, 5), Decl(discriminatedUnionTypes1.ts, 65, 5), Decl(discriminatedUnionTypes1.ts, 66, 5))
+>m : Symbol(m, Decl(discriminatedUnionTypes1.ts, 133, 12))
+>kind : Symbol(kind, Decl(discriminatedUnionTypes1.ts, 64, 5), Decl(discriminatedUnionTypes1.ts, 65, 5), Decl(discriminatedUnionTypes1.ts, 66, 5))
+
+        case "A":
+            return;
+        case "D":
+            throw new Error();
+>Error : Symbol(Error, Decl(lib.d.ts, --, --), Decl(lib.d.ts, --, --))
+    }
+    m;  // { kind: "B" | "C", y: number }
+>m : Symbol(m, Decl(discriminatedUnionTypes1.ts, 133, 12))
+}
diff --git a/tests/baselines/reference/discriminatedUnionTypes1.types b/tests/baselines/reference/discriminatedUnionTypes1.types
new file mode 100644
index 00000000000..234de28eaba
--- /dev/null
+++ b/tests/baselines/reference/discriminatedUnionTypes1.types
@@ -0,0 +1,465 @@
+=== tests/cases/conformance/types/union/discriminatedUnionTypes1.ts ===
+interface Square {
+>Square : Square
+
+    kind: "square";
+>kind : "square"
+
+    size: number;
+>size : number
+}
+
+interface Rectangle {
+>Rectangle : Rectangle
+
+    kind: "rectangle";
+>kind : "rectangle"
+
+    width: number;
+>width : number
+
+    height: number;
+>height : number
+}
+
+interface Circle {
+>Circle : Circle
+
+    kind: "circle";
+>kind : "circle"
+
+    radius: number;
+>radius : number
+}
+
+type Shape = Square | Rectangle | Circle;
+>Shape : Square | Rectangle | Circle
+>Square : Square
+>Rectangle : Rectangle
+>Circle : Circle
+
+function area1(s: Shape) {
+>area1 : (s: Square | Rectangle | Circle) => number
+>s : Square | Rectangle | Circle
+>Shape : Square | Rectangle | Circle
+
+    if (s.kind === "square") {
+>s.kind === "square" : boolean
+>s.kind : "square" | "rectangle" | "circle"
+>s : Square | Rectangle | Circle
+>kind : "square" | "rectangle" | "circle"
+>"square" : string
+
+        return s.size * s.size;
+>s.size * s.size : number
+>s.size : number
+>s : Square
+>size : number
+>s.size : number
+>s : Square
+>size : number
+    }
+    else if (s.kind === "circle") {
+>s.kind === "circle" : boolean
+>s.kind : "rectangle" | "circle"
+>s : Rectangle | Circle
+>kind : "rectangle" | "circle"
+>"circle" : string
+
+        return Math.PI * s.radius * s.radius;
+>Math.PI * s.radius * s.radius : number
+>Math.PI * s.radius : number
+>Math.PI : number
+>Math : Math
+>PI : number
+>s.radius : number
+>s : Circle
+>radius : number
+>s.radius : number
+>s : Circle
+>radius : number
+    }
+    else if (s.kind === "rectangle") {
+>s.kind === "rectangle" : boolean
+>s.kind : "rectangle"
+>s : Rectangle
+>kind : "rectangle"
+>"rectangle" : string
+
+        return s.width * s.height;
+>s.width * s.height : number
+>s.width : number
+>s : Rectangle
+>width : number
+>s.height : number
+>s : Rectangle
+>height : number
+    }
+    else {
+        return 0;
+>0 : number
+    }
+}
+
+function area2(s: Shape) {
+>area2 : (s: Square | Rectangle | Circle) => number
+>s : Square | Rectangle | Circle
+>Shape : Square | Rectangle | Circle
+
+    switch (s.kind) {
+>s.kind : "square" | "rectangle" | "circle"
+>s : Square | Rectangle | Circle
+>kind : "square" | "rectangle" | "circle"
+
+        case "square": return s.size * s.size;
+>"square" : string
+>s.size * s.size : number
+>s.size : number
+>s : Square
+>size : number
+>s.size : number
+>s : Square
+>size : number
+
+        case "rectangle": return s.width * s.height;
+>"rectangle" : string
+>s.width * s.height : number
+>s.width : number
+>s : Rectangle
+>width : number
+>s.height : number
+>s : Rectangle
+>height : number
+
+        case "circle": return Math.PI * s.radius * s.radius;
+>"circle" : string
+>Math.PI * s.radius * s.radius : number
+>Math.PI * s.radius : number
+>Math.PI : number
+>Math : Math
+>PI : number
+>s.radius : number
+>s : Circle
+>radius : number
+>s.radius : number
+>s : Circle
+>radius : number
+    }
+}
+
+function assertNever(x: never): never {
+>assertNever : (x: never) => never
+>x : never
+
+    throw new Error("Unexpected object: " + x);
+>new Error("Unexpected object: " + x) : Error
+>Error : ErrorConstructor
+>"Unexpected object: " + x : string
+>"Unexpected object: " : string
+>x : never
+}
+
+function area3(s: Shape) {
+>area3 : (s: Square | Rectangle | Circle) => number
+>s : Square | Rectangle | Circle
+>Shape : Square | Rectangle | Circle
+
+    switch (s.kind) {
+>s.kind : "square" | "rectangle" | "circle"
+>s : Square | Rectangle | Circle
+>kind : "square" | "rectangle" | "circle"
+
+        case "square": return s.size * s.size;
+>"square" : string
+>s.size * s.size : number
+>s.size : number
+>s : Square
+>size : number
+>s.size : number
+>s : Square
+>size : number
+
+        case "rectangle": return s.width * s.height;
+>"rectangle" : string
+>s.width * s.height : number
+>s.width : number
+>s : Rectangle
+>width : number
+>s.height : number
+>s : Rectangle
+>height : number
+
+        case "circle": return Math.PI * s.radius * s.radius;
+>"circle" : string
+>Math.PI * s.radius * s.radius : number
+>Math.PI * s.radius : number
+>Math.PI : number
+>Math : Math
+>PI : number
+>s.radius : number
+>s : Circle
+>radius : number
+>s.radius : number
+>s : Circle
+>radius : number
+
+        default: return assertNever(s);
+>assertNever(s) : never
+>assertNever : (x: never) => never
+>s : never
+    }
+}
+
+function area4(s: Shape) {
+>area4 : (s: Square | Rectangle | Circle) => number
+>s : Square | Rectangle | Circle
+>Shape : Square | Rectangle | Circle
+
+    switch (s.kind) {
+>s.kind : "square" | "rectangle" | "circle"
+>s : Square | Rectangle | Circle
+>kind : "square" | "rectangle" | "circle"
+
+        case "square": return s.size * s.size;
+>"square" : string
+>s.size * s.size : number
+>s.size : number
+>s : Square
+>size : number
+>s.size : number
+>s : Square
+>size : number
+
+        case "rectangle": return s.width * s.height;
+>"rectangle" : string
+>s.width * s.height : number
+>s.width : number
+>s : Rectangle
+>width : number
+>s.height : number
+>s : Rectangle
+>height : number
+
+        case "circle": return Math.PI * s.radius * s.radius;
+>"circle" : string
+>Math.PI * s.radius * s.radius : number
+>Math.PI * s.radius : number
+>Math.PI : number
+>Math : Math
+>PI : number
+>s.radius : number
+>s : Circle
+>radius : number
+>s.radius : number
+>s : Circle
+>radius : number
+    }
+    return assertNever(s);
+>assertNever(s) : never
+>assertNever : (x: never) => never
+>s : never
+}
+
+type Message =
+>Message : { kind: "A"; x: string; } | { kind: "B" | "C"; y: number; } | { kind: "D"; }
+
+    { kind: "A", x: string } |
+>kind : "A"
+>x : string
+
+    { kind: "B" | "C", y: number } |
+>kind : "B" | "C"
+>y : number
+
+    { kind: "D" };
+>kind : "D"
+
+function f1(m: Message) {
+>f1 : (m: { kind: "A"; x: string; } | { kind: "B" | "C"; y: number; } | { kind: "D"; }) => void
+>m : { kind: "A"; x: string; } | { kind: "B" | "C"; y: number; } | { kind: "D"; }
+>Message : { kind: "A"; x: string; } | { kind: "B" | "C"; y: number; } | { kind: "D"; }
+
+    if (m.kind === "A") {
+>m.kind === "A" : boolean
+>m.kind : "A" | "B" | "C" | "D"
+>m : { kind: "A"; x: string; } | { kind: "B" | "C"; y: number; } | { kind: "D"; }
+>kind : "A" | "B" | "C" | "D"
+>"A" : string
+
+        m;  // { kind: "A", x: string }
+>m : { kind: "A"; x: string; }
+    }
+    else if (m.kind === "D") {
+>m.kind === "D" : boolean
+>m.kind : "B" | "C" | "D"
+>m : { kind: "B" | "C"; y: number; } | { kind: "D"; }
+>kind : "B" | "C" | "D"
+>"D" : string
+
+        m;  // { kind: "D" }
+>m : { kind: "D"; }
+    }
+    else {
+        m;  // { kind: "B" | "C", y: number }
+>m : { kind: "B" | "C"; y: number; }
+    }
+}
+
+function f2(m: Message) {
+>f2 : (m: { kind: "A"; x: string; } | { kind: "B" | "C"; y: number; } | { kind: "D"; }) => void
+>m : { kind: "A"; x: string; } | { kind: "B" | "C"; y: number; } | { kind: "D"; }
+>Message : { kind: "A"; x: string; } | { kind: "B" | "C"; y: number; } | { kind: "D"; }
+
+    if (m.kind === "A") {
+>m.kind === "A" : boolean
+>m.kind : "A" | "B" | "C" | "D"
+>m : { kind: "A"; x: string; } | { kind: "B" | "C"; y: number; } | { kind: "D"; }
+>kind : "A" | "B" | "C" | "D"
+>"A" : string
+
+        return;
+    }
+    m;  // { kind: "B" | "C", y: number } | { kind: "D" }
+>m : { kind: "B" | "C"; y: number; } | { kind: "D"; }
+}
+
+function f3(m: Message) {
+>f3 : (m: { kind: "A"; x: string; } | { kind: "B" | "C"; y: number; } | { kind: "D"; }) => void
+>m : { kind: "A"; x: string; } | { kind: "B" | "C"; y: number; } | { kind: "D"; }
+>Message : { kind: "A"; x: string; } | { kind: "B" | "C"; y: number; } | { kind: "D"; }
+
+    if (m.kind === "X") {
+>m.kind === "X" : boolean
+>m.kind : "A" | "B" | "C" | "D"
+>m : { kind: "A"; x: string; } | { kind: "B" | "C"; y: number; } | { kind: "D"; }
+>kind : "A" | "B" | "C" | "D"
+>"X" : string
+
+        m;  // never
+>m : never
+    }
+}
+
+function f4(m: Message, x: "A" | "D") {
+>f4 : (m: { kind: "A"; x: string; } | { kind: "B" | "C"; y: number; } | { kind: "D"; }, x: "A" | "D") => void
+>m : { kind: "A"; x: string; } | { kind: "B" | "C"; y: number; } | { kind: "D"; }
+>Message : { kind: "A"; x: string; } | { kind: "B" | "C"; y: number; } | { kind: "D"; }
+>x : "A" | "D"
+
+    if (m.kind == x) {
+>m.kind == x : boolean
+>m.kind : "A" | "B" | "C" | "D"
+>m : { kind: "A"; x: string; } | { kind: "B" | "C"; y: number; } | { kind: "D"; }
+>kind : "A" | "B" | "C" | "D"
+>x : "A" | "D"
+
+        m;  // { kind: "A", x: string } | { kind: "D" }
+>m : { kind: "A"; x: string; } | { kind: "D"; }
+    }
+}
+
+function f5(m: Message) {
+>f5 : (m: { kind: "A"; x: string; } | { kind: "B" | "C"; y: number; } | { kind: "D"; }) => void
+>m : { kind: "A"; x: string; } | { kind: "B" | "C"; y: number; } | { kind: "D"; }
+>Message : { kind: "A"; x: string; } | { kind: "B" | "C"; y: number; } | { kind: "D"; }
+
+    switch (m.kind) {
+>m.kind : "A" | "B" | "C" | "D"
+>m : { kind: "A"; x: string; } | { kind: "B" | "C"; y: number; } | { kind: "D"; }
+>kind : "A" | "B" | "C" | "D"
+
+        case "A":
+>"A" : string
+
+            m;  // { kind: "A", x: string }
+>m : { kind: "A"; x: string; }
+
+            break;
+        case "D":
+>"D" : string
+
+            m;  // { kind: "D" }
+>m : { kind: "D"; }
+
+            break;
+        default:
+            m;  // { kind: "B" | "C", y: number }
+>m : { kind: "B" | "C"; y: number; }
+    }
+}
+
+function f6(m: Message) {
+>f6 : (m: { kind: "A"; x: string; } | { kind: "B" | "C"; y: number; } | { kind: "D"; }) => void
+>m : { kind: "A"; x: string; } | { kind: "B" | "C"; y: number; } | { kind: "D"; }
+>Message : { kind: "A"; x: string; } | { kind: "B" | "C"; y: number; } | { kind: "D"; }
+
+    switch (m.kind) {
+>m.kind : "A" | "B" | "C" | "D"
+>m : { kind: "A"; x: string; } | { kind: "B" | "C"; y: number; } | { kind: "D"; }
+>kind : "A" | "B" | "C" | "D"
+
+        case "A":
+>"A" : string
+
+            m;  // { kind: "A", x: string }
+>m : { kind: "A"; x: string; }
+
+        case "D":
+>"D" : string
+
+            m;  // { kind: "A", x: string } | { kind: "D" }
+>m : { kind: "D"; } | { kind: "A"; x: string; }
+
+            break;
+        default:
+            m;  // { kind: "B" | "C", y: number }
+>m : { kind: "B" | "C"; y: number; }
+    }
+}
+
+function f7(m: Message) {
+>f7 : (m: { kind: "A"; x: string; } | { kind: "B" | "C"; y: number; } | { kind: "D"; }) => void
+>m : { kind: "A"; x: string; } | { kind: "B" | "C"; y: number; } | { kind: "D"; }
+>Message : { kind: "A"; x: string; } | { kind: "B" | "C"; y: number; } | { kind: "D"; }
+
+    switch (m.kind) {
+>m.kind : "A" | "B" | "C" | "D"
+>m : { kind: "A"; x: string; } | { kind: "B" | "C"; y: number; } | { kind: "D"; }
+>kind : "A" | "B" | "C" | "D"
+
+        case "A":
+>"A" : string
+
+        case "B":
+>"B" : string
+
+            return;
+    }
+    m;  // { kind: "B" | "C", y: number } | { kind: "D" }
+>m : { kind: "B" | "C"; y: number; } | { kind: "D"; }
+}
+
+function f8(m: Message) {
+>f8 : (m: { kind: "A"; x: string; } | { kind: "B" | "C"; y: number; } | { kind: "D"; }) => void
+>m : { kind: "A"; x: string; } | { kind: "B" | "C"; y: number; } | { kind: "D"; }
+>Message : { kind: "A"; x: string; } | { kind: "B" | "C"; y: number; } | { kind: "D"; }
+
+    switch (m.kind) {
+>m.kind : "A" | "B" | "C" | "D"
+>m : { kind: "A"; x: string; } | { kind: "B" | "C"; y: number; } | { kind: "D"; }
+>kind : "A" | "B" | "C" | "D"
+
+        case "A":
+>"A" : string
+
+            return;
+        case "D":
+>"D" : string
+
+            throw new Error();
+>new Error() : Error
+>Error : ErrorConstructor
+    }
+    m;  // { kind: "B" | "C", y: number }
+>m : { kind: "B" | "C"; y: number; }
+}
diff --git a/tests/cases/conformance/types/union/discriminatedUnionTypes1.ts b/tests/cases/conformance/types/union/discriminatedUnionTypes1.ts
new file mode 100644
index 00000000000..404162308b9
--- /dev/null
+++ b/tests/cases/conformance/types/union/discriminatedUnionTypes1.ts
@@ -0,0 +1,142 @@
+interface Square {
+    kind: "square";
+    size: number;
+}
+
+interface Rectangle {
+    kind: "rectangle";
+    width: number;
+    height: number;
+}
+
+interface Circle {
+    kind: "circle";
+    radius: number;
+}
+
+type Shape = Square | Rectangle | Circle;
+
+function area1(s: Shape) {
+    if (s.kind === "square") {
+        return s.size * s.size;
+    }
+    else if (s.kind === "circle") {
+        return Math.PI * s.radius * s.radius;
+    }
+    else if (s.kind === "rectangle") {
+        return s.width * s.height;
+    }
+    else {
+        return 0;
+    }
+}
+
+function area2(s: Shape) {
+    switch (s.kind) {
+        case "square": return s.size * s.size;
+        case "rectangle": return s.width * s.height;
+        case "circle": return Math.PI * s.radius * s.radius;
+    }
+}
+
+function assertNever(x: never): never {
+    throw new Error("Unexpected object: " + x);
+}
+
+function area3(s: Shape) {
+    switch (s.kind) {
+        case "square": return s.size * s.size;
+        case "rectangle": return s.width * s.height;
+        case "circle": return Math.PI * s.radius * s.radius;
+        default: return assertNever(s);
+    }
+}
+
+function area4(s: Shape) {
+    switch (s.kind) {
+        case "square": return s.size * s.size;
+        case "rectangle": return s.width * s.height;
+        case "circle": return Math.PI * s.radius * s.radius;
+    }
+    return assertNever(s);
+}
+
+type Message =
+    { kind: "A", x: string } |
+    { kind: "B" | "C", y: number } |
+    { kind: "D" };
+
+function f1(m: Message) {
+    if (m.kind === "A") {
+        m;  // { kind: "A", x: string }
+    }
+    else if (m.kind === "D") {
+        m;  // { kind: "D" }
+    }
+    else {
+        m;  // { kind: "B" | "C", y: number }
+    }
+}
+
+function f2(m: Message) {
+    if (m.kind === "A") {
+        return;
+    }
+    m;  // { kind: "B" | "C", y: number } | { kind: "D" }
+}
+
+function f3(m: Message) {
+    if (m.kind === "X") {
+        m;  // never
+    }
+}
+
+function f4(m: Message, x: "A" | "D") {
+    if (m.kind == x) {
+        m;  // { kind: "A", x: string } | { kind: "D" }
+    }
+}
+
+function f5(m: Message) {
+    switch (m.kind) {
+        case "A":
+            m;  // { kind: "A", x: string }
+            break;
+        case "D":
+            m;  // { kind: "D" }
+            break;
+        default:
+            m;  // { kind: "B" | "C", y: number }
+    }
+}
+
+function f6(m: Message) {
+    switch (m.kind) {
+        case "A":
+            m;  // { kind: "A", x: string }
+        case "D":
+            m;  // { kind: "A", x: string } | { kind: "D" }
+            break;
+        default:
+            m;  // { kind: "B" | "C", y: number }
+    }
+}
+
+function f7(m: Message) {
+    switch (m.kind) {
+        case "A":
+        case "B":
+            return;
+    }
+    m;  // { kind: "B" | "C", y: number } | { kind: "D" }
+}
+
+function f8(m: Message) {
+    switch (m.kind) {
+        case "A":
+            return;
+        case "D":
+            throw new Error();
+    }
+    m;  // { kind: "B" | "C", y: number }
+}
\ No newline at end of file