tests/cases/conformance/controlFlow/exhaustiveSwitchStatements1.ts(7,9): error TS7027: Unreachable code detected. tests/cases/conformance/controlFlow/exhaustiveSwitchStatements1.ts(235,5): error TS2367: This condition will always return 'false' since the types 'keyof O' and '"c"' have no overlap. tests/cases/conformance/controlFlow/exhaustiveSwitchStatements1.ts(247,10): error TS2339: Property 'kind' does not exist on type 'never'. ==== tests/cases/conformance/controlFlow/exhaustiveSwitchStatements1.ts (3 errors) ==== function f1(x: 1 | 2): string { if (!!true) { switch (x) { case 1: return 'a'; case 2: return 'b'; } x; // Unreachable ~~ !!! error TS7027: Unreachable code detected. } else { throw 0; } } function f2(x: 1 | 2) { let z: number; switch (x) { case 1: z = 10; break; case 2: z = 20; break; } z; // Definitely assigned } function f3(x: 1 | 2) { switch (x) { case 1: return 10; case 2: return 20; // Default considered reachable to allow defensive coding default: throw new Error("Bad input"); } } // Repro from #11572 enum E { A, B } function f(e: E): number { switch (e) { case E.A: return 0 case E.B: return 1 } } function g(e: E): number { if (!true) return -1 else switch (e) { case E.A: return 0 case E.B: return 1 } } // Repro from #12668 interface Square { kind: "square"; size: number; } interface Rectangle { kind: "rectangle"; width: number; height: number; } interface Circle { kind: "circle"; radius: number; } interface Triangle { kind: "triangle"; side: number; } type Shape = Square | Rectangle | Circle | Triangle; function area(s: Shape): number { let area; switch (s.kind) { case "square": area = s.size * s.size; break; case "rectangle": area = s.width * s.height; break; case "circle": area = Math.PI * s.radius * s.radius; break; case "triangle": area = Math.sqrt(3) / 4 * s.side * s.side; break; } return area; } function areaWrapped(s: Shape): number { let area; area = (() => { 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; case "triangle": return Math.sqrt(3) / 4 * s.side * s.side; } })(); return area; } // Repro from #13241 enum MyEnum { A, B } function thisGivesError(e: MyEnum): string { let s: string; switch (e) { case MyEnum.A: s = "it was A"; break; case MyEnum.B: s = "it was B"; break; } return s; } function good1(e: MyEnum): string { let s: string; switch (e) { case MyEnum.A: s = "it was A"; break; case MyEnum.B: s = "it was B"; break; default: s = "it was something else"; break; } return s; } function good2(e: MyEnum): string { switch (e) { case MyEnum.A: return "it was A"; case MyEnum.B: return "it was B"; } } // Repro from #18362 enum Level { One, Two, } const doSomethingWithLevel = (level: Level) => { let next: Level; switch (level) { case Level.One: next = Level.Two; break; case Level.Two: next = Level.One; break; } return next; }; // Repro from #20409 interface Square2 { kind: "square"; size: number; } interface Circle2 { kind: "circle"; radius: number; } type Shape2 = Square2 | Circle2; function withDefault(s1: Shape2, s2: Shape2): string { switch (s1.kind) { case "square": return "1"; case "circle": switch (s2.kind) { case "square": return "2"; case "circle": return "3"; default: return "never"; } } } function withoutDefault(s1: Shape2, s2: Shape2): string { switch (s1.kind) { case "square": return "1"; case "circle": switch (s2.kind) { case "square": return "2"; case "circle": return "3"; } } } // Repro from #20823 function test4(value: 1 | 2) { let x: string; switch (value) { case 1: x = "one"; break; case 2: x = "two"; break; } return x; } // Repro from #34661 enum Animal { DOG, CAT } declare const zoo: { animal: Animal } | undefined; function expression(): Animal { switch (zoo?.animal ?? Animal.DOG) { case Animal.DOG: return Animal.DOG case Animal.CAT: return Animal.CAT } } // Repro from #34840 function foo() { const foo: number | undefined = 0; while (true) { const stats = foo; switch (stats) { case 1: break; case 2: break; } } } // Repro from #35070 type O = { a: number, b: number }; type K = keyof O | 'c'; function ff(o: O, k: K) { switch(k) { case 'c': k = 'a'; } k === 'c'; // Error ~~~~~~~~~ !!! error TS2367: This condition will always return 'false' since the types 'keyof O' and '"c"' have no overlap. return o[k]; } // Repro from #35431 type A = { kind: "abc" } | { kind: "def" }; function f35431(a: A) { switch (a.kind) { case "abc": case "def": return; default: a!.kind; // Error expected ~~~~ !!! error TS2339: Property 'kind' does not exist on type 'never'. } }