STOFL if narrowed variable is mentioned in 'case' condition expression

[zhuravlikjb]

A very simple repro:

function f(x: {a: "A", b} | {a: "C", e}) {
    switch (x.a) {
    case x:
        break;
    }
}

that results in stack overflow:

C:\Users\Anton.Lobov\Desktop\ts_new\TypeScript>node built\local\tsc.js hello.ts
C:\Users\Anton.Lobov\Desktop\ts_new\TypeScript\built\local\tsc.js:37776
                throw e;
                ^

RangeError: Maximum call stack size exceeded
    at Object.hasOwnProperty (native)
    at Object.hasProperty (C:\Users\Anton.Lobov\Desktop\ts_new\TypeScript\built\local\tsc.js:1060:31)
    at getPropertyOfUnionOrIntersectionType (C:\Users\Anton.Lobov\Desktop\ts_new\TypeScript\built\local\tsc.js:17227:20)
    at getPropertyOfType (C:\Users\Anton.Lobov\Desktop\ts_new\TypeScript\built\local\tsc.js:17255:24)
    at getTypeOfPropertyOfType (C:\Users\Anton.Lobov\Desktop\ts_new\TypeScript\built\local\tsc.js:16003:24)
    at narrowTypeBySwitchOnDiscriminant (C:\Users\Anton.Lobov\Desktop\ts_new\TypeScript\built\local\tsc.js:20364:32)
    at getTypeAtSwitchClause (C:\Users\Anton.Lobov\Desktop\ts_new\TypeScript\built\local\tsc.js:20207:24)
    at getTypeAtFlowNode (C:\Users\Anton.Lobov\Desktop\ts_new\TypeScript\built\local\tsc.js:20145:32)
    at getFlowTypeOfReference (C:\Users\Anton.Lobov\Desktop\ts_new\TypeScript\built\local\tsc.js:20118:26)
    at checkIdentifier (C:\Users\Anton.Lobov\Desktop\ts_new\TypeScript\built\local\tsc.js:20577:28)

[mhegazy]

@sandersn can you take a look.

[ahejlsberg]

I see what the issue is here. The control flow graph for each case expression includes the FlowSwitchClause flow node, but it shouldn't. It's an easy fix, I will put up a PR.