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AndaristAndarist
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Check if switch statements are exhaustive when their expressions is generic with a literal type constraint (#60644)
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5 files changed

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lines changed

5 files changed

+618
-1
lines changed

‎src/compiler/checker.ts

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Original file line numberDiff line numberDiff line change
@@ -38682,7 +38682,7 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
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// A missing not-equal flag indicates that the type wasn't handled by some case.
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return !someType(operandConstraint, t => getTypeFacts(t, notEqualFacts) === notEqualFacts);
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}
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const type = checkExpressionCached(node.expression);
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const type = getBaseConstraintOrType(checkExpressionCached(node.expression));
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if (!isLiteralType(type)) {
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return false;
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}

‎tests/baselines/reference/dependentReturnType9.errors.txt

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dependentReturnType9.ts(57,4): error TS2366: Function lacks ending return statement and return type does not include 'undefined'.
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==== dependentReturnType9.ts (1 errors) ====
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type Payload =
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| { _tag: "auth"; username: string; password: string }
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| { _tag: "cart"; items: Array<{ id: string; quantity: number }> }
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| { _tag: "person"; name: string; age: number };
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type PayloadContent = {
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[P in Payload as P["_tag"]]: Omit<P, "_tag">;
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};
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// ok, exhaustive cases and default case with throw
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function mockPayload<P_TAG extends Payload["_tag"]>(
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str: P_TAG,
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): PayloadContent[P_TAG] {
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switch (str) {
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case "auth":
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return { username: "test", password: "admin" };
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case "cart":
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return { items: [{ id: "123", quantity: 123 }] };
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case "person":
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return { name: "andrea", age: 27 };
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default:
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throw new Error("unknown tag");
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}
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}
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// ok, non-exhaustive cases but default case with throw
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function mockPayload2<P_TAG extends Payload["_tag"]>(
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str: P_TAG,
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): PayloadContent[P_TAG] {
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switch (str) {
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case "auth":
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return { username: "test", password: "admin" };
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case "cart":
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return { items: [{ id: "123", quantity: 123 }] };
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default:
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throw new Error("unhandled tag");
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}
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}
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// ok, exhaustive cases
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function mockPayload3<P_TAG extends Payload["_tag"]>(
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str: P_TAG,
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): PayloadContent[P_TAG] {
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switch (str) {
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case "auth":
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return { username: "test", password: "admin" };
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case "cart":
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return { items: [{ id: "123", quantity: 123 }] };
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case "person":
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return { name: "andrea", age: 27 };
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}
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}
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// error, non-exhaustive cases
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function mockPayload4<P_TAG extends Payload["_tag"]>(
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str: P_TAG,
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): PayloadContent[P_TAG] {
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~~~~~~~~~~~~~~~~~~~~~
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!!! error TS2366: Function lacks ending return statement and return type does not include 'undefined'.
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switch (str) {
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case "auth":
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return { username: "test", password: "admin" };
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case "cart":
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return { items: [{ id: "123", quantity: 123 }] };
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}
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}
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‎tests/baselines/reference/dependentReturnType9.symbols

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//// [tests/cases/compiler/dependentReturnType9.ts] ////
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=== dependentReturnType9.ts ===
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type Payload =
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>Payload : Symbol(Payload, Decl(dependentReturnType9.ts, 0, 0))
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| { _tag: "auth"; username: string; password: string }
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>_tag : Symbol(_tag, Decl(dependentReturnType9.ts, 1, 5))
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>username : Symbol(username, Decl(dependentReturnType9.ts, 1, 19))
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>password : Symbol(password, Decl(dependentReturnType9.ts, 1, 37))
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| { _tag: "cart"; items: Array<{ id: string; quantity: number }> }
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>_tag : Symbol(_tag, Decl(dependentReturnType9.ts, 2, 5))
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>items : Symbol(items, Decl(dependentReturnType9.ts, 2, 19))
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>Array : Symbol(Array, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))
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>id : Symbol(id, Decl(dependentReturnType9.ts, 2, 34))
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>quantity : Symbol(quantity, Decl(dependentReturnType9.ts, 2, 46))
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| { _tag: "person"; name: string; age: number };
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>_tag : Symbol(_tag, Decl(dependentReturnType9.ts, 3, 5))
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>name : Symbol(name, Decl(dependentReturnType9.ts, 3, 21))
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>age : Symbol(age, Decl(dependentReturnType9.ts, 3, 35))
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type PayloadContent = {
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>PayloadContent : Symbol(PayloadContent, Decl(dependentReturnType9.ts, 3, 50))
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[P in Payload as P["_tag"]]: Omit<P, "_tag">;
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>P : Symbol(P, Decl(dependentReturnType9.ts, 6, 3))
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>Payload : Symbol(Payload, Decl(dependentReturnType9.ts, 0, 0))
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>P : Symbol(P, Decl(dependentReturnType9.ts, 6, 3))
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>Omit : Symbol(Omit, Decl(lib.es5.d.ts, --, --))
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>P : Symbol(P, Decl(dependentReturnType9.ts, 6, 3))
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};
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// ok, exhaustive cases and default case with throw
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function mockPayload<P_TAG extends Payload["_tag"]>(
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>mockPayload : Symbol(mockPayload, Decl(dependentReturnType9.ts, 7, 2))
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>P_TAG : Symbol(P_TAG, Decl(dependentReturnType9.ts, 10, 21))
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>Payload : Symbol(Payload, Decl(dependentReturnType9.ts, 0, 0))
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str: P_TAG,
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>str : Symbol(str, Decl(dependentReturnType9.ts, 10, 52))
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>P_TAG : Symbol(P_TAG, Decl(dependentReturnType9.ts, 10, 21))
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): PayloadContent[P_TAG] {
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>PayloadContent : Symbol(PayloadContent, Decl(dependentReturnType9.ts, 3, 50))
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>P_TAG : Symbol(P_TAG, Decl(dependentReturnType9.ts, 10, 21))
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switch (str) {
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>str : Symbol(str, Decl(dependentReturnType9.ts, 10, 52))
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case "auth":
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return { username: "test", password: "admin" };
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>username : Symbol(username, Decl(dependentReturnType9.ts, 15, 14))
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>password : Symbol(password, Decl(dependentReturnType9.ts, 15, 32))
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case "cart":
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return { items: [{ id: "123", quantity: 123 }] };
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>items : Symbol(items, Decl(dependentReturnType9.ts, 17, 14))
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>id : Symbol(id, Decl(dependentReturnType9.ts, 17, 24))
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>quantity : Symbol(quantity, Decl(dependentReturnType9.ts, 17, 35))
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case "person":
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return { name: "andrea", age: 27 };
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>name : Symbol(name, Decl(dependentReturnType9.ts, 19, 14))
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>age : Symbol(age, Decl(dependentReturnType9.ts, 19, 30))
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default:
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throw new Error("unknown tag");
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>Error : Symbol(Error, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))
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}
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}
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// ok, non-exhaustive cases but default case with throw
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function mockPayload2<P_TAG extends Payload["_tag"]>(
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>mockPayload2 : Symbol(mockPayload2, Decl(dependentReturnType9.ts, 23, 1))
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>P_TAG : Symbol(P_TAG, Decl(dependentReturnType9.ts, 26, 22))
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>Payload : Symbol(Payload, Decl(dependentReturnType9.ts, 0, 0))
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str: P_TAG,
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>str : Symbol(str, Decl(dependentReturnType9.ts, 26, 53))
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>P_TAG : Symbol(P_TAG, Decl(dependentReturnType9.ts, 26, 22))
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): PayloadContent[P_TAG] {
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>PayloadContent : Symbol(PayloadContent, Decl(dependentReturnType9.ts, 3, 50))
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>P_TAG : Symbol(P_TAG, Decl(dependentReturnType9.ts, 26, 22))
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switch (str) {
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>str : Symbol(str, Decl(dependentReturnType9.ts, 26, 53))
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case "auth":
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return { username: "test", password: "admin" };
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>username : Symbol(username, Decl(dependentReturnType9.ts, 31, 14))
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>password : Symbol(password, Decl(dependentReturnType9.ts, 31, 32))
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case "cart":
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return { items: [{ id: "123", quantity: 123 }] };
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>items : Symbol(items, Decl(dependentReturnType9.ts, 33, 14))
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>id : Symbol(id, Decl(dependentReturnType9.ts, 33, 24))
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>quantity : Symbol(quantity, Decl(dependentReturnType9.ts, 33, 35))
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default:
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throw new Error("unhandled tag");
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>Error : Symbol(Error, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))
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}
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}
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// ok, exhaustive cases
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function mockPayload3<P_TAG extends Payload["_tag"]>(
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>mockPayload3 : Symbol(mockPayload3, Decl(dependentReturnType9.ts, 37, 1))
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>P_TAG : Symbol(P_TAG, Decl(dependentReturnType9.ts, 40, 22))
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>Payload : Symbol(Payload, Decl(dependentReturnType9.ts, 0, 0))
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str: P_TAG,
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>str : Symbol(str, Decl(dependentReturnType9.ts, 40, 53))
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>P_TAG : Symbol(P_TAG, Decl(dependentReturnType9.ts, 40, 22))
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): PayloadContent[P_TAG] {
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>PayloadContent : Symbol(PayloadContent, Decl(dependentReturnType9.ts, 3, 50))
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>P_TAG : Symbol(P_TAG, Decl(dependentReturnType9.ts, 40, 22))
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switch (str) {
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>str : Symbol(str, Decl(dependentReturnType9.ts, 40, 53))
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case "auth":
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return { username: "test", password: "admin" };
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>username : Symbol(username, Decl(dependentReturnType9.ts, 45, 14))
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>password : Symbol(password, Decl(dependentReturnType9.ts, 45, 32))
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case "cart":
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return { items: [{ id: "123", quantity: 123 }] };
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>items : Symbol(items, Decl(dependentReturnType9.ts, 47, 14))
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>id : Symbol(id, Decl(dependentReturnType9.ts, 47, 24))
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>quantity : Symbol(quantity, Decl(dependentReturnType9.ts, 47, 35))
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case "person":
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return { name: "andrea", age: 27 };
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>name : Symbol(name, Decl(dependentReturnType9.ts, 49, 14))
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>age : Symbol(age, Decl(dependentReturnType9.ts, 49, 30))
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}
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}
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// error, non-exhaustive cases
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function mockPayload4<P_TAG extends Payload["_tag"]>(
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>mockPayload4 : Symbol(mockPayload4, Decl(dependentReturnType9.ts, 51, 1))
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>P_TAG : Symbol(P_TAG, Decl(dependentReturnType9.ts, 54, 22))
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>Payload : Symbol(Payload, Decl(dependentReturnType9.ts, 0, 0))
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str: P_TAG,
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>str : Symbol(str, Decl(dependentReturnType9.ts, 54, 53))
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>P_TAG : Symbol(P_TAG, Decl(dependentReturnType9.ts, 54, 22))
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): PayloadContent[P_TAG] {
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>PayloadContent : Symbol(PayloadContent, Decl(dependentReturnType9.ts, 3, 50))
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>P_TAG : Symbol(P_TAG, Decl(dependentReturnType9.ts, 54, 22))
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switch (str) {
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>str : Symbol(str, Decl(dependentReturnType9.ts, 54, 53))
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case "auth":
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return { username: "test", password: "admin" };
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>username : Symbol(username, Decl(dependentReturnType9.ts, 59, 14))
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>password : Symbol(password, Decl(dependentReturnType9.ts, 59, 32))
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case "cart":
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return { items: [{ id: "123", quantity: 123 }] };
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>items : Symbol(items, Decl(dependentReturnType9.ts, 61, 14))
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>id : Symbol(id, Decl(dependentReturnType9.ts, 61, 24))
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>quantity : Symbol(quantity, Decl(dependentReturnType9.ts, 61, 35))
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}
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}
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