128 lines
2.7 KiB
TypeScript
128 lines
2.7 KiB
TypeScript
// @strictNullChecks: true
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// Repro from #8513
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let cond: boolean;
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export type Optional<a> = Some<a> | None;
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export interface None { readonly none: string; }
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export interface Some<a> { readonly some: a; }
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export const none : None = { none: '' };
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export function isSome<a>(value: Optional<a>): value is Some<a> {
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return 'some' in value;
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}
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function someFrom<a>(some: a) {
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return { some };
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}
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export function fn<r>(makeSome: () => r): void {
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let result: Optional<r> = none;
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result; // None
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while (cond) {
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result; // Some<r> | None
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result = someFrom(isSome(result) ? result.some : makeSome());
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result; // Some<r>
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}
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}
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function foo1() {
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let x: string | number | boolean = 0;
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x; // number
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while (cond) {
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x; // number, then string | number
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x = typeof x === "string" ? x.slice() : "abc";
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x; // string
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}
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x;
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}
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function foo2() {
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let x: string | number | boolean = 0;
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x; // number
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while (cond) {
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x; // number, then string | number
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if (typeof x === "string") {
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x = x.slice();
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}
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else {
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x = "abc";
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}
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x; // string
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}
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x;
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}
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// Type guards as assertions
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function f1() {
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let x: string | number | undefined = undefined;
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x; // undefined
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if (x) {
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x; // string | number (guard as assertion)
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}
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x; // string | number | undefined
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}
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function f2() {
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let x: string | number | undefined = undefined;
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x; // undefined
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if (typeof x === "string") {
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x; // string (guard as assertion)
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}
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x; // string | undefined
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}
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function f3() {
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let x: string | number | undefined = undefined;
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x; // undefined
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if (!x) {
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return;
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}
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x; // string | number (guard as assertion)
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}
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function f4() {
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let x: string | number | undefined = undefined;
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x; // undefined
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if (typeof x === "boolean") {
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x; // nothing (boolean not in declared type)
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}
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x; // undefined
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}
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function f5(x: string | number) {
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if (typeof x === "string" && typeof x === "number") {
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x; // number (guard as assertion)
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}
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else {
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x; // string | number
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}
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x; // string | number
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}
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function f6() {
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let x: string | undefined | null;
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x!.slice();
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x = "";
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x!.slice();
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x = undefined;
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x!.slice();
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x = null;
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x!.slice();
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x = <undefined | null>undefined;
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x!.slice();
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x = <string | undefined>"";
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x!.slice();
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x = <string | null>"";
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x!.slice();
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}
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function f7() {
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let x: string;
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x!.slice();
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}
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