Stack overflow when inferring recursive type

[plol]

TypeScript Version: 3.9.0-dev.20200319

Search Terms:
call stack exceeded

Code

export type A = "number" | "null" | A[];

export type F<T> = null extends T
 ? [F<NonNullable<T>>, "null"]
 : T extends number
 ? "number"
 : never;

export type G<T> = { [k in keyof T]: F<T[k]> };

interface K {
 b: number | null;
}

const gK: { [key in keyof K]: A } = { b: ["number", "null"] };

function foo<T>(g: G<T>): T {
 return {} as any;
}

foo(gK);

Expected behavior:
Not crashing the compiler

Actual behavior:

% ./node_modules/.bin/tsc --version
Version 3.9.0-dev.20200319
% ./node_modules/.bin/tsc bug.ts
...node_modules/typescript/lib/tsc.js:81982
 throw e;
 ^

RangeError: Maximum call stack size exceeded
 at makeCompositeTypeMapper (/home/plol/src/wtf/bug/node_modules/typescript/lib/tsc.js:38964:41)
 at combineTypeMappers (/home/plol/src/wtf/bug/node_modules/typescript/lib/tsc.js:38974:30)
 at instantiateTypeWorker (/home/plol/src/wtf/bug/node_modules/typescript/lib/tsc.js:39273:62)
 at instantiateType (/home/plol/src/wtf/bug/node_modules/typescript/lib/tsc.js:39220:26)
 at getMappedType (/home/plol/src/wtf/bug/node_modules/typescript/lib/tsc.js:38952:63)
 at /home/plol/src/wtf/bug/node_modules/typescript/lib/tsc.js:39187:92
 at Object.map (/home/plol/src/wtf/bug/node_modules/typescript/lib/tsc.js:335:29)
 at getConditionalTypeInstantiation (/home/plol/src/wtf/bug/node_modules/typescript/lib/tsc.js:39187:40)
 at instantiateTypeWorker (/home/plol/src/wtf/bug/node_modules/typescript/lib/tsc.js:39273:24)
 at instantiateType (/home/plol/src/wtf/bug/node_modules/typescript/lib/tsc.js:39220:26)

[ahejlsberg]

Issue here is that tuple types have no associated symbol and we use the symbol to track and stop recursion. Pretty easy to fix.