Closed
Description
TypeScript Version: 3.1.0-dev.20180913
Search Terms:
typechecking infinite recursion
Code
export type DirectoryBase = {name: string}
export type DirectoryEntries = {readonly [n in string]: Directory};
export type Directory = DirectoryBase & {entries: DirectoryEntries};
export type ExactDirectory<E extends DirectoryEntries> = DirectoryBase & {entries: E};
export type Accessor<D extends Directory> =
D extends Directory ? {[K in keyof D['entries']]: Accessor<D['entries'][K]>} : {};
// intersection and conditional type are necessary to exhibit the problem
export type BadAccessor<D extends Directory> = {
} & (D extends Directory ? {[K in keyof D['entries']]: Accessor<D['entries'][K]>} : {});
function f<E extends DirectoryEntries, C extends Directory>(accessor: Accessor<C>): void {
const a1 = accessor as Accessor<ExactDirectory<E>>; // ok, error as expected
const a2 = accessor as BadAccessor<ExactDirectory<E>>; // boom
}Expected behavior:
compilation error is reported
Actual behavior:
apparently, compilation does not terminate
Playground Link: nope WARNING pasting the above code to the playground freezes the playground UI, and because it remembers the code you are stuck forever. Browsers start warning about unresponsive page after a while.
Related Issues:
might be the same as #27066 but observed behavior is different